mm: pgtable: add missing pt_index to struct ptdesc

In s390, the page->index field is used for gmap (see gmap_shadow_pgt()),
so add the corresponding pt_index to struct ptdesc and add a comment to
clarify this.

Link: https://lkml.kernel.org/r/283624c2af45fb2090b41a6b1b5481bb0a45bad7.1709541697.git.zhengqi.arch@bytedance.com
Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Claudio Imbrenda <imbrenda@linux.ibm.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Janosch Frank <frankja@linux.ibm.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Mike Rapoport (IBM) <rppt@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: pgtable: correct the wrong comment about ptdesc->__page_flags

Patch series "minor fixes and supplement for ptdesc".

In this series, the [PATCH 1/3] and [PATCH 2/3] are fixes for some issues
discovered during code inspection.

The [PATCH 3/3] is a supplement to ptdesc conversion in s390, I don't know
why this is not done in the commit 6326c26c1514 ("s390: convert various
pgalloc functions to use ptdescs"), maybe I missed something. And since I
don't have an s390 environment, I hope kernel test robot can help compile
and test, and this is why I did not fold [PATCH 2/3] and [PATCH 3/3] into
one patch.


This patch (of 3):

The commit 32cc0b7c9d50 ("powerpc: add pte_free_defer() for pgtables
sharing page") introduced the use of PageActive flag to page table
fragments tracking, so the ptdesc->__page_flags is not unused, so correct
the wrong comment.

Link: https://lkml.kernel.org/r/cover.1709541697.git.zhengqi.arch@bytedance.com
Link: https://lkml.kernel.org/r/cc42d5915fd98fd802f920de243f535efcfe01db.1709541697.git.zhengqi.arch@bytedance.com
Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Mike Rapoport (IBM) <rppt@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Claudio Imbrenda <imbrenda@linux.ibm.com>
Cc: Janosch Frank <frankja@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/mmu_gather: add __tlb_remove_folio_pages()

Add __tlb_remove_folio_pages(), which will remove multiple consecutive
pages that belong to the same large folio, instead of only a single page.
We'll be using this function when optimizing unmapping/zapping of large
folios that are mapped by PTEs.

We're using the remaining spare bit in an encoded_page to indicate that
the next enoced page in an array contains actually shifted "nr_pages".
Teach swap/freeing code about putting multiple folio references, and
delayed rmap handling to remove page ranges of a folio.

This extension allows for still gathering almost as many small folios as
we used to (-1, because we have to prepare for a possibly bigger next
entry), but still allows for gathering consecutive pages that belong to
the same large folio.

Note that we don't pass the folio pointer, because it is not required for
now. Further, we don't support page_size != PAGE_SIZE, it won't be
required for simple PTE batching.

We have to provide a separate s390 implementation, but it's fairly
straight forward.

Another, more invasive and likely more expensive, approach would be to use
folio+range or a PFN range instead of page+nr_pages. But, we should do
that consistently for the whole mmu_gather. For now, let's keep it simple
and add "nr_pages" only.

Note that it is now possible to gather significantly more pages: In the
past, we were able to gather ~10000 pages, now we can also gather ~5000
folio fragments that span multiple pages. A folio fragment on x86-64 can
span up to 512 pages (2 MiB THP) and on arm64 with 64k in theory 8192
pages (512 MiB THP). Gathering more memory is not considered something we
should worry about, especially because these are already corner cases.

While we can gather more total memory, we won't free more folio fragments.
As long as page freeing time primarily only depends on the number of
involved folios, there is no effective change for !preempt configurations.
However, we'll adjust tlb_batch_pages_flush() separately to handle corner
cases where page freeing time grows proportionally with the actual memory
size.

Link: https://lkml.kernel.org/r/20240214204435.167852-9-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Ryan Roberts <ryan.roberts@arm.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Michal Hocko <mhocko@suse.com>
Cc: "Naveen N. Rao" <naveen.n.rao@linux.ibm.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Yin Fengwei <fengwei.yin@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/mmu_gather: define ENCODED_PAGE_FLAG_DELAY_RMAP

Nowadays, encoded pages are only used in mmu_gather handling. Let's
update the documentation, and define ENCODED_PAGE_BIT_DELAY_RMAP. While
at it, rename ENCODE_PAGE_BITS to ENCODED_PAGE_BITS.

If encoded page pointers would ever be used in other context again, we'd
likely want to change the defines to reflect their context (e.g.,
ENCODED_PAGE_FLAG_MMU_GATHER_DELAY_RMAP). For now, let's keep it simple.

This is a preparation for using the remaining spare bit to indicate that
the next item in an array of encoded pages is a "nr_pages" argument and
not an encoded page.

Link: https://lkml.kernel.org/r/20240214204435.167852-7-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Ryan Roberts <ryan.roberts@arm.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Michal Hocko <mhocko@suse.com>
Cc: "Naveen N. Rao" <naveen.n.rao@linux.ibm.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Yin Fengwei <fengwei.yin@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: Deprecate pasid field

Drop the pasid field, as all the information needed for sva domain
management has been moved to the newly added iommu_mm field.

Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Vasant Hegde <vasant.hegde@amd.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Tina Zhang <tina.zhang@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/20231027000525.1278806-7-tina.zhang@intel.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>

mm: Add structure to keep sva information

Introduce iommu_mm_data structure to keep sva information (pasid and the
related sva domains). Add iommu_mm pointer, pointing to an instance of
iommu_mm_data structure, to mm.

Reviewed-by: Vasant Hegde <vasant.hegde@amd.com>
Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Tested-by: Nicolin Chen <nicolinc@nvidia.com>
Signed-off-by: Tina Zhang <tina.zhang@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/20231027000525.1278806-5-tina.zhang@intel.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>

iommu: Change kconfig around IOMMU_SVA

Linus suggested that the kconfig here is confusing:

https://lore.kernel.org/all/CAHk-=wgUiAtiszwseM1p2fCJ+sC4XWQ+YN4TanFhUgvUqjr9Xw@mail.gmail.com/

Let's break it into three kconfigs controlling distinct things:

- CONFIG_IOMMU_MM_DATA controls if the mm_struct has the additional
fields for the IOMMU. Currently only PASID, but later patches store
a struct iommu_mm_data *

- CONFIG_ARCH_HAS_CPU_PASID controls if the arch needs the scheduling bit
for keeping track of the ENQCMD instruction. x86 will select this if
IOMMU_SVA is enabled

- IOMMU_SVA controls if the IOMMU core compiles in the SVA support code
for iommu driver use and the IOMMU exported API

This way ARM will not enable CONFIG_ARCH_HAS_CPU_PASID

Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/20231027000525.1278806-2-tina.zhang@intel.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>

page_pool: transition to reference count management after page draining

To support multiple users referencing the same fragment,
'pp_frag_count' is renamed to 'pp_ref_count', transitioning pp pages
from fragment management to reference count management after draining
based on the suggestion from [1].

The idea is that the concept of fragmenting exists before the page is
drained, and all related functions retain their current names.
However, once the page is drained, its management shifts to being
governed by 'pp_ref_count'. Therefore, all functions associated with
that lifecycle stage of a pp page are renamed.

[1]
http://lore.kernel.org/netdev/f71d9448-70c8-8793-dc9a-0eb48a570300@huawei.com

Signed-off-by: Liang Chen <liangchen.linux@gmail.com>
Reviewed-by: Yunsheng Lin <linyunsheng@huawei.com>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Reviewed-by: Mina Almasry <almasrymina@google.com>
Link: https://lore.kernel.org/r/20231212044614.42733-2-liangchen.linux@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

mm/mglru: remove CONFIG_MEMCG

Remove CONFIG_MEMCG in a refactoring to improve code readability at
the cost of a few bytes in struct lru_gen_folio per node when
CONFIG_MEMCG=n.

Link: https://lkml.kernel.org/r/20231227141205.2200125-4-kinseyho@google.com
Signed-off-by: Kinsey Ho <kinseyho@google.com>
Co-developed-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Tested-by: Donet Tom <donettom@linux.vnet.ibm.com>
Acked-by: Yu Zhao <yuzhao@google.com>
Cc: kernel test robot <lkp@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/mglru: add CONFIG_LRU_GEN_WALKS_MMU

Add CONFIG_LRU_GEN_WALKS_MMU such that if disabled, the code that
walks page tables to promote pages into the youngest generation will
not be built.

Also improves code readability by adding two helper functions
get_mm_state() and get_next_mm().

Link: https://lkml.kernel.org/r/20231227141205.2200125-3-kinseyho@google.com
Signed-off-by: Kinsey Ho <kinseyho@google.com>
Co-developed-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Tested-by: Donet Tom <donettom@linux.vnet.ibm.com>
Acked-by: Yu Zhao <yuzhao@google.com>
Cc: kernel test robot <lkp@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

maple_tree: separate ma_state node from status

The maple tree node is overloaded to keep status as well as the active
node. This, unfortunately, results in a re-walk on underflow or overflow.
Since the maple state has room, the status can be placed in its own enum
in the structure. Once an underflow/overflow is detected, certain modes
can restore the status to active and others may need to re-walk just that
one node to see the entry.

The status being an enum has the benefit of detecting unhandled status in
switch statements.

[Liam.Howlett@oracle.com: fix comments about MAS_*]
Link: https://lkml.kernel.org/r/20231106154124.614247-1-Liam.Howlett@oracle.com
[Liam.Howlett@oracle.com: update forking to separate maple state and node]
Link: https://lkml.kernel.org/r/20231106154551.615042-1-Liam.Howlett@oracle.com
[Liam.Howlett@oracle.com: fix mas_prev() state separation code]
Link: https://lkml.kernel.org/r/20231207193319.4025462-1-Liam.Howlett@oracle.com
Link: https://lkml.kernel.org/r/20231101171629.3612299-9-Liam.Howlett@oracle.com
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Peng Zhang <zhangpeng.00@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

pgtable: rename ptdesc _refcount field to __page_refcount

Rename ptdesc _refcount field to __page_refcount similar to the other
unused page fields.

Link: https://lkml.kernel.org/r/982bdc652ba79a606c3d01c905766e7e076b3315.1700594815.git.agordeev@linux.ibm.com
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
Suggested-by: Vishal Moola <vishal.moola@gmail.com>
Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

pgtable: fix s390 ptdesc field comments

Patch series "minor ptdesc updates", v3.


This patch (of 2):

Since commit d08d4e7cd6bf ("s390/mm: use full 4KB page for 2KB PTE") there
is no fragmented page tracking on s390. Fix the corresponding comments.

Link: https://lkml.kernel.org/r/cover.1700594815.git.agordeev@linux.ibm.com
Link: https://lkml.kernel.org/r/2eead241f3a45bed26c7911cf66bded1e35670b8.1700594815.git.agordeev@linux.ibm.com
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
Suggested-by: Heiko Carstens <hca@linux.ibm.com>
Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Cc: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

sched/numa: Fix mm numa_scan_seq based unconditional scan

Since commit fc137c0ddab2 ("sched/numa: enhance vma scanning logic")

NUMA Balancing allows updating PTEs to trap NUMA hinting faults if the
task had previously accessed VMA. However unconditional scan of VMAs are
allowed during initial phase of VMA creation until process's
mm numa_scan_seq reaches 2 even though current task had not accessed VMA.

Rationale:
- Without initial scan subsequent PTE update may never happen.
- Give fair opportunity to all the VMAs to be scanned and subsequently
understand the access pattern of all the VMAs.

But it has a corner case where, if a VMA is created after some time,
process's mm numa_scan_seq could be already greater than 2.

For e.g., values of mm numa_scan_seq when VMAs are created by running
mmtest autonuma benchmark briefly looks like:
start_seq=0 : 459
start_seq=2 : 138
start_seq=3 : 144
start_seq=4 : 8
start_seq=8 : 1
start_seq=9 : 1
This results in no unconditional PTE updates for those VMAs created after
some time.

Fix:
- Note down the initial value of mm numa_scan_seq in per VMA start_seq.
- Allow unconditional scan till start_seq + 2.

Result:
SUT: AMD EPYC Milan with 2 NUMA nodes 256 cpus.
base kernel: upstream 6.6-rc6 with Mels patches [1] applied.

kernbench
========== base patched %gain
Amean elsp-128 165.09 ( 0.00%) 164.78 * 0.19%*

Duration User 41404.28 41375.08
Duration System 9862.22 9768.48
Duration Elapsed 519.87 518.72

Ops NUMA PTE updates 1041416.00 831536.00
Ops NUMA hint faults 263296.00 220966.00
Ops NUMA pages migrated 258021.00 212769.00
Ops AutoNUMA cost 1328.67 1114.69

autonumabench

NUMA01_THREADLOCAL
==================
Amean elsp-NUMA01_THREADLOCAL 81.79 (0.00%) 67.74 * 17.18%*

Duration User 54832.73 47379.67
Duration System 75.00 185.75
Duration Elapsed 576.72 476.09

Ops NUMA PTE updates 394429.00 11121044.00
Ops NUMA hint faults 1001.00 8906404.00
Ops NUMA pages migrated 288.00 2998694.00
Ops AutoNUMA cost 7.77 44666.84

Signed-off-by: Raghavendra K T <raghavendra.kt@amd.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Mel Gorman <mgorman@suse.de>
Link: https://lore.kernel.org/r/2ea7cbce80ac7c62e90cbfb9653a7972f902439f.1697816692.git.raghavendra.kt@amd.com

mm_types: add virtual and _last_cpupid into struct folio

Patch series "mm: convert page cpupid functions to folios", v3.

The cpupid(or access time) used by numa balancing is stored in flags or
_last_cpupid(if LAST_CPUPID_NOT_IN_PAGE_FLAGS) of page, this is to convert
page cpupid to folio cpupid, a new _last_cpupid is added into folio, which
make us to use folio->_last_cpupid directly, and the page cpupid functions
are converted to folio ones.

page_cpupid_last() -> folio_last_cpupid()
xchg_page_access_time() -> folio_xchg_access_time()
page_cpupid_xchg_last() -> folio_xchg_last_cpupid()


This patch (of 19):

If WANT_PAGE_VIRTUAL and LAST_CPUPID_NOT_IN_PAGE_FLAGS defined, the
'virtual' and '_last_cpupid' are in struct page, and since _last_cpupid is
used by numa balancing feature, it is better to move it before KMSAN
metadata from struct page, also add them into struct folio to make us to
access them from folio directly.

Link: https://lkml.kernel.org/r/20231018140806.2783514-1-wangkefeng.wang@huawei.com
Link: https://lkml.kernel.org/r/20231018140806.2783514-2-wangkefeng.wang@huawei.com
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: move vma_policy() and anon_vma_name() decls to mm_types.h

Patch series "Abstract vma_merge() and split_vma()", v4.

The vma_merge() interface is very confusing and its implementation has led
to numerous bugs as a result of that confusion.

In addition there is duplication both in invocation of vma_merge(), but
also in the common mprotect()-style pattern of attempting a merge, then if
this fails, splitting the portion of a VMA about to have its attributes
changed.

This pattern has been copy/pasted around the kernel in each instance where
such an operation has been required, each very slightly modified from the
last to make it even harder to decipher what is going on.

Simplify the whole thing by dividing the actual uses of vma_merge() and
split_vma() into specific and abstracted functions and de-duplicate the
vma_merge()/split_vma() pattern altogether.

Doing so also opens the door to changing how vma_merge() is implemented -
by knowing precisely what cases a caller is invoking rather than having a
central interface where anything might happen we can untangle the brittle
and confusing vma_merge() implementation into something more workable.

For mprotect()-like cases we introduce vma_modify() which performs the
vma_merge()/split_vma() pattern, returning a pointer to either the merged
or split VMA or an ERR_PTR(err) if the splits fail.

We provide a number of inline helper functions to make things even clearer:-

* vma_modify_flags() - Prepare to modify the VMA's flags.
* vma_modify_flags_name() - Prepare to modify the VMA's flags/anon_vma_name
* vma_modify_policy() - Prepare to modify the VMA's mempolicy.
* vma_modify_flags_uffd() - Prepare to modify the VMA's flags/uffd context.

For cases where a new VMA is attempted to be merged with adjacent VMAs we
add:-

* vma_merge_new_vma() - Prepare to merge a new VMA.
* vma_merge_extend() - Prepare to extend the end of a new VMA.


This patch (of 5):

The vma_policy() define is a helper specifically for a VMA field so it
makes sense to host it in the memory management types header.

The anon_vma_name(), anon_vma_name_alloc() and anon_vma_name_free()
functions are a little out of place in mm_inline.h as they define external
functions, and so it makes sense to locate them in mm_types.h.

The purpose of these relocations is to make it possible to abstract static
inline wrappers which invoke both of these helpers.

Link: https://lkml.kernel.org/r/cover.1697043508.git.lstoakes@gmail.com
Link: https://lkml.kernel.org/r/24bfc6c9e382fffbcb0ea8d424392c27d56cc8ca.1697043508.git.lstoakes@gmail.com
Signed-off-by: Lorenzo Stoakes <lstoakes@gmail.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Lorenzo Stoakes <lstoakes@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

page_pool: fragment API support for 32-bit arch with 64-bit DMA

Currently page_pool_alloc_frag() is not supported in 32-bit
arch with 64-bit DMA because of the overlap issue between
pp_frag_count and dma_addr_upper in 'struct page' for those
arches, which seems to be quite common, see [1], which means
driver may need to handle it when using fragment API.

It is assumed that the combination of the above arch with an
address space >16TB does not exist, as all those arches have
64b equivalent, it seems logical to use the 64b version for a
system with a large address space. It is also assumed that dma
address is page aligned when we are dma mapping a page aligned
buffer, see [2].

That means we're storing 12 bits of 0 at the lower end for a
dma address, we can reuse those bits for the above arches to
support 32b+12b, which is 16TB of memory.

If we make a wrong assumption, a warning is emitted so that
user can report to us.

1. https://lore.kernel.org/all/20211117075652.58299-1-linyunsheng@huawei.com/
2. https://lore.kernel.org/all/20230818145145.4b357c89@kernel.org/

Tested-by: Alexander Lobakin <aleksander.lobakin@intel.com>
Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com>
CC: Lorenzo Bianconi <lorenzo@kernel.org>
CC: Alexander Duyck <alexander.duyck@gmail.com>
CC: Liang Chen <liangchen.linux@gmail.com>
CC: Guillaume Tucker <guillaume.tucker@collabora.com>
CC: Matthew Wilcox <willy@infradead.org>
CC: Linux-MM <linux-mm@kvack.org>
Link: https://lore.kernel.org/r/20231013064827.61135-2-linyunsheng@huawei.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

sched/numa: Complete scanning of inactive VMAs when there is no alternative

VMAs are skipped if there is no recent fault activity but this represents
a chicken-and-egg problem as there may be no fault activity if the PTEs
are never updated to trap NUMA hints. There is an indirect reliance on
scanning to be forced early in the lifetime of a task but this may fail
to detect changes in phase behaviour. Force inactive VMAs to be scanned
when all other eligible VMAs have been updated within the same scan
sequence.

Test results in general look good with some changes in performance, both
negative and positive, depending on whether the additional scanning and
faulting was beneficial or not to the workload. The autonuma benchmark
workload NUMA01_THREADLOCAL was picked for closer examination. The workload
creates two processes with numerous threads and thread-local storage that
is zero-filled in a loop. It exercises the corner case where unrelated
threads may skip VMAs that are thread-local to another thread and still
has some VMAs that inactive while the workload executes.

The VMA skipping activity frequency with and without the patch:

6.6.0-rc2-sched-numabtrace-v1
=============================
649 reason=scan_delay
9,094 reason=unsuitable
48,915 reason=shared_ro
143,919 reason=inaccessible
193,050 reason=pid_inactive

6.6.0-rc2-sched-numabselective-v1
=============================
146 reason=seq_completed
622 reason=ignore_pid_inactive

624 reason=scan_delay
6,570 reason=unsuitable
16,101 reason=shared_ro
27,608 reason=inaccessible
41,939 reason=pid_inactive

Note that with the patch applied, the PID activity is ignored
(ignore_pid_inactive) to ensure a VMA with some activity is completely
scanned. In addition, a small number of VMAs are scanned when no other
eligible VMA is available during a single scan window (seq_completed).
The number of times a VMA is skipped due to no PID activity from the
scanning task (pid_inactive) drops dramatically. It is expected that
this will increase the number of PTEs updated for NUMA hinting faults
as well as hinting faults but these represent PTEs that would otherwise
have been missed. The tradeoff is scan+fault overhead versus improving
locality due to migration.

On a 2-socket Cascade Lake test machine, the time to complete the
workload is as follows;

6.6.0-rc2 6.6.0-rc2
sched-numabtrace-v1 sched-numabselective-v1
Min elsp-NUMA01_THREADLOCAL 174.22 ( 0.00%) 117.64 ( 32.48%)
Amean elsp-NUMA01_THREADLOCAL 175.68 ( 0.00%) 123.34 * 29.79%*
Stddev elsp-NUMA01_THREADLOCAL 1.20 ( 0.00%) 4.06 (-238.20%)
CoeffVar elsp-NUMA01_THREADLOCAL 0.68 ( 0.00%) 3.29 (-381.70%)
Max elsp-NUMA01_THREADLOCAL 177.18 ( 0.00%) 128.03 ( 27.74%)

The time to complete the workload is reduced by almost 30%:

6.6.0-rc2 6.6.0-rc2
sched-numabtrace-v1 sched-numabselective-v1 /
Duration User 91201.80 63506.64
Duration System 2015.53 1819.78
Duration Elapsed 1234.77 868.37

In this specific case, system CPU time was not increased but it's not
universally true.

From vmstat, the NUMA scanning and fault activity is as follows;

6.6.0-rc2 6.6.0-rc2
sched-numabtrace-v1 sched-numabselective-v1
Ops NUMA base-page range updates 64272.00 26374386.00
Ops NUMA PTE updates 36624.00 55538.00
Ops NUMA PMD updates 54.00 51404.00
Ops NUMA hint faults 15504.00 75786.00
Ops NUMA hint local faults % 14860.00 56763.00
Ops NUMA hint local percent 95.85 74.90
Ops NUMA pages migrated 1629.00 6469222.00

Both the number of PTE updates and hint faults is dramatically
increased. While this is superficially unfortunate, it represents
ranges that were simply skipped without the patch. As a result
of the scanning and hinting faults, many more pages were also
migrated but as the time to completion is reduced, the overhead
is offset by the gain.

Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Raghavendra K T <raghavendra.kt@amd.com>
Link: https://lore.kernel.org/r/20231010083143.19593-7-mgorman@techsingularity.net

sched/numa: Rename vma_numab_state::access_pids[] => ::pids_active[], ::next_pid_reset => ::pids_active_reset

The access_pids[] field name is somewhat ambiguous as no PIDs are accessed.
Similarly, it's not clear that next_pid_reset is related to access_pids[].
Rename the fields to more accurately reflect their purpose.

[ mingo: Rename in the comments too. ]

Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20231010083143.19593-3-mgorman@techsingularity.net

sched/numa: Document vma_numab_state fields

Document the intended usage of the fields.

[ mingo: Reformatted to take less vertical space & tidied it up. ]

Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20231010083143.19593-2-mgorman@techsingularity.net

mm/swap: use dedicated entry for swap in folio

Let's stop working on the private field and use an explicit swap field.
We have to move the swp_entry_t typedef.

Link: https://lkml.kernel.org/r/20230821160849.531668-3-david@redhat.com
Signed-off-by: Matthew Wilcox <willy@infradead.org>
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Chris Li <chrisl@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/swap: stop using page->private on tail pages for THP_SWAP

Patch series "mm/swap: stop using page->private on tail pages for THP_SWAP
+ cleanups".

This series stops using page->private on tail pages for THP_SWAP, replaces
folio->private by folio->swap for swapcache folios, and starts using
"new_folio" for tail pages that we are splitting to remove the usage of
page->private for swapcache handling completely.


This patch (of 4):

Let's stop using page->private on tail pages, making it possible to just
unconditionally reuse that field in the tail pages of large folios.

The remaining usage of the private field for THP_SWAP is in the THP
splitting code (mm/huge_memory.c), that we'll handle separately later.

Update the THP_SWAP documentation and sanity checks in mm_types.h and
__split_huge_page_tail().

[david@redhat.com: stop using page->private on tail pages for THP_SWAP]
Link: https://lkml.kernel.org/r/6f0a82a3-6948-20d9-580b-be1dbf415701@redhat.com
Link: https://lkml.kernel.org/r/20230821160849.531668-1-david@redhat.com
Link: https://lkml.kernel.org/r/20230821160849.531668-2-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com> [arm64]
Reviewed-by: Yosry Ahmed <yosryahmed@google.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Peter Xu <peterx@redhat.com>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: add missing VM_FAULT_RESULT_TRACE name for VM_FAULT_COMPLETED

VM_FAULT_RESULT_TRACE should contain an element for every vm_fault_reason
to be used as flag_array inside trace_print_flags_seq(). The element for
VM_FAULT_COMPLETED is missing, add it.

Link: https://lkml.kernel.org/r/20230630211957.1341547-3-surenb@google.com
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Hillf Danton <hdanton@sina.com>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Josef Bacik <josef@toxicpanda.com>
Cc: Laurent Dufour <ldufour@linux.ibm.com>
Cc: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Michel Lespinasse <michel@lespinasse.org>
Cc: Minchan Kim <minchan@google.com>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Punit Agrawal <punit.agrawal@bytedance.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Yu Zhao <yuzhao@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: add tail private fields to struct folio

Because THP_SWAP uses page->private for each page, we must not use the
space which overlaps that field for anything which would conflict with
that. We avoid the conflict on 32-bit systems by disallowing THP_SWAP on
32-bit.

Link: https://lkml.kernel.org/r/20230816151201.3655946-13-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Yanteng Si <siyanteng@loongson.cn>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: free up a word in the first tail page

Store the folio order in the low byte of the flags word in the first tail
page. This frees up the word that was being used to store the order and
dtor bytes previously.

Link: https://lkml.kernel.org/r/20230816151201.3655946-11-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Yanteng Si <siyanteng@loongson.cn>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: add large_rmappable page flag

Stored in the first tail page's flags, this flag replaces the destructor.
That removes the last of the destructors, so remove all references to
folio_dtor and compound_dtor.

Link: https://lkml.kernel.org/r/20230816151201.3655946-9-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Yanteng Si <siyanteng@loongson.cn>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: remove page table members from struct page

The page table members are now split out into their own ptdesc struct.
Remove them from struct page.

Link: https://lkml.kernel.org/r/20230807230513.102486-16-vishal.moola@gmail.com
Signed-off-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Acked-by: Mike Rapoport (IBM) <rppt@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Claudio Imbrenda <imbrenda@linux.ibm.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Dinh Nguyen <dinguyen@kernel.org>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Geert Uytterhoeven <geert+renesas@glider.be>
Cc: Guo Ren <guoren@kernel.org>
Cc: Huacai Chen <chenhuacai@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Cc: Jonas Bonn <jonas@southpole.se>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Palmer Dabbelt <palmer@rivosinc.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Richard Weinberger <richard@nod.at>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: add utility functions for ptdesc

Introduce utility functions setting the foundation for ptdescs. These
will also assist in the splitting out of ptdesc from struct page.

Functions that focus on the descriptor are prefixed with ptdesc_* while
functions that focus on the pagetable are prefixed with pagetable_*.

pagetable_alloc() is defined to allocate new ptdesc pages as compound
pages. This is to standardize ptdescs by allowing for one allocation and
one free function, in contrast to 2 allocation and 2 free functions.

Link: https://lkml.kernel.org/r/20230807230513.102486-4-vishal.moola@gmail.com
Signed-off-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Claudio Imbrenda <imbrenda@linux.ibm.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Dinh Nguyen <dinguyen@kernel.org>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Geert Uytterhoeven <geert+renesas@glider.be>
Cc: Guo Ren <guoren@kernel.org>
Cc: Huacai Chen <chenhuacai@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Cc: Jonas Bonn <jonas@southpole.se>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mike Rapoport (IBM) <rppt@kernel.org>
Cc: Palmer Dabbelt <palmer@rivosinc.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Richard Weinberger <richard@nod.at>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

pgtable: create struct ptdesc

Currently, page table information is stored within struct page. As part
of simplifying struct page, create struct ptdesc for page table
information.

Link: https://lkml.kernel.org/r/20230807230513.102486-3-vishal.moola@gmail.com
Signed-off-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Acked-by: Mike Rapoport (IBM) <rppt@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Claudio Imbrenda <imbrenda@linux.ibm.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Dinh Nguyen <dinguyen@kernel.org>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Geert Uytterhoeven <geert+renesas@glider.be>
Cc: Guo Ren <guoren@kernel.org>
Cc: Huacai Chen <chenhuacai@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Cc: Jonas Bonn <jonas@southpole.se>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Palmer Dabbelt <palmer@rivosinc.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Richard Weinberger <richard@nod.at>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/pgtable: add pte_free_defer() for pgtable as page

Add the generic pte_free_defer(), to call pte_free() via call_rcu().
pte_free_defer() will be called inside khugepaged's retract_page_tables()
loop, where allocating extra memory cannot be relied upon. This version
suits all those architectures which use an unfragmented page for one page
table (none of whose pte_free()s use the mm arg which was passed to it).

Link: https://lkml.kernel.org/r/78e921b0-b681-a1b0-dc20-44c9efa4ef3c@google.com
Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Claudio Imbrenda <imbrenda@linux.ibm.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Huang, Ying <ying.huang@intel.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: Jann Horn <jannh@google.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mike Rapoport (IBM) <rppt@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Qi Zheng <zhengqi.arch@bytedance.com>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: SeongJae Park <sj@kernel.org>
Cc: Song Liu <song@kernel.org>
Cc: Steven Price <steven.price@arm.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Will Deacon <will@kernel.org>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Yu Zhao <yuzhao@google.com>
Cc: Zack Rusin <zackr@vmware.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

ksm: add ksm zero pages for each process

As the number of ksm zero pages is not included in ksm_merging_pages per
process when enabling use_zero_pages, it's unclear of how many actual
pages are merged by KSM. To let users accurately estimate their memory
demands when unsharing KSM zero-pages, it's necessary to show KSM zero-
pages per process. In addition, it help users to know the actual KSM
profit because KSM-placed zero pages are also benefit from KSM.

since unsharing zero pages placed by KSM accurately is achieved, then
tracking empty pages merging and unmerging is not a difficult thing any
longer.

Since we already have /proc/<pid>/ksm_stat, just add the information of
'ksm_zero_pages' in it.

Link: https://lkml.kernel.org/r/20230613030938.185993-1-yang.yang29@zte.com.cn
Signed-off-by: xu xin <xu.xin16@zte.com.cn>
Acked-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Xiaokai Ran <ran.xiaokai@zte.com.cn>
Reviewed-by: Yang Yang <yang.yang29@zte.com.cn>
Cc: Claudio Imbrenda <imbrenda@linux.ibm.com>
Cc: Xuexin Jiang <jiang.xuexin@zte.com.cn>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/gup: reintroduce FOLL_NUMA as FOLL_HONOR_NUMA_FAULT

Unfortunately commit 474098edac26 ("mm/gup: replace FOLL_NUMA by
gup_can_follow_protnone()") missed that follow_page() and
follow_trans_huge_pmd() never implicitly set FOLL_NUMA because they really
don't want to fail on PROT_NONE-mapped pages -- either due to NUMA hinting
or due to inaccessible (PROT_NONE) VMAs.

As spelled out in commit 0b9d705297b2 ("mm: numa: Support NUMA hinting
page faults from gup/gup_fast"): "Other follow_page callers like KSM
should not use FOLL_NUMA, or they would fail to get the pages if they use
follow_page instead of get_user_pages."

liubo reported [1] that smaps_rollup results are imprecise, because they
miss accounting of pages that are mapped PROT_NONE. Further, it's easy to
reproduce that KSM no longer works on inaccessible VMAs on x86-64, because
pte_protnone()/pmd_protnone() also indictaes "true" in inaccessible VMAs,
and follow_page() refuses to return such pages right now.

As KVM really depends on these NUMA hinting faults, removing the
pte_protnone()/pmd_protnone() handling in GUP code completely is not
really an option.

To fix the issues at hand, let's revive FOLL_NUMA as FOLL_HONOR_NUMA_FAULT
to restore the original behavior for now and add better comments.

Set FOLL_HONOR_NUMA_FAULT independent of FOLL_FORCE in
is_valid_gup_args(), to add that flag for all external GUP users.

Note that there are three GUP-internal __get_user_pages() users that don't
end up calling is_valid_gup_args() and consequently won't get
FOLL_HONOR_NUMA_FAULT set.

1) get_dump_page(): we really don't want to handle NUMA hinting
faults. It specifies FOLL_FORCE and wouldn't have honored NUMA
hinting faults already.
2) populate_vma_page_range(): we really don't want to handle NUMA hinting
faults. It specifies FOLL_FORCE on accessible VMAs, so it wouldn't have
honored NUMA hinting faults already.
3) faultin_vma_page_range(): we similarly don't want to handle NUMA
hinting faults.

To make the combination of FOLL_FORCE and FOLL_HONOR_NUMA_FAULT work in
inaccessible VMAs properly, we have to perform VMA accessibility checks in
gup_can_follow_protnone().

As GUP-fast should reject such pages either way in
pte_access_permitted()/pmd_access_permitted() -- for example on x86-64 and
arm64 that both implement pte_protnone() -- let's just always fallback to
ordinary GUP when stumbling over pte_protnone()/pmd_protnone().

As Linus notes [2], honoring NUMA faults might only make sense for
selected GUP users.

So we should really see if we can instead let relevant GUP callers specify
it manually, and not trigger NUMA hinting faults from GUP as default.
Prepare for that by making FOLL_HONOR_NUMA_FAULT an external GUP flag and
adding appropriate documenation.

While at it, remove a stale comment from follow_trans_huge_pmd(): That
comment for pmd_protnone() was added in commit 2b4847e73004 ("mm: numa:
serialise parallel get_user_page against THP migration"), which noted:

THP does not unmap pages due to a lack of support for migration
entries at a PMD level. This allows races with get_user_pages

Nowadays, we do have PMD migration entries, so the comment no longer
applies. Let's drop it.

[1] https://lore.kernel.org/r/20230726073409.631838-1-liubo254@huawei.com
[2] https://lore.kernel.org/r/CAHk-=wgRiP_9X0rRdZKT8nhemZGNateMtb366t37d8-x7VRs=g@mail.gmail.com

Link: https://lkml.kernel.org/r/20230803143208.383663-2-david@redhat.com
Fixes: 474098edac26 ("mm/gup: replace FOLL_NUMA by gup_can_follow_protnone()")
Signed-off-by: David Hildenbrand <david@redhat.com>
Reported-by: liubo <liubo254@huawei.com>
Closes: https://lore.kernel.org/r/20230726073409.631838-1-liubo254@huawei.com
Reported-by: Peter Xu <peterx@redhat.com>
Closes: https://lore.kernel.org/all/ZMKJjDaqZ7FW0jfe@x1n/
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Peter Xu <peterx@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: fix memory ordering for mm_lock_seq and vm_lock_seq

mm->mm_lock_seq effectively functions as a read/write lock; therefore it
must be used with acquire/release semantics.

A specific example is the interaction between userfaultfd_register() and
lock_vma_under_rcu().

userfaultfd_register() does the following from the point where it changes
a VMA's flags to the point where concurrent readers are permitted again
(in a simple scenario where only a single private VMA is accessed and no
merging/splitting is involved):

userfaultfd_register
userfaultfd_set_vm_flags
vm_flags_reset
vma_start_write
down_write(&vma->vm_lock->lock)
vma->vm_lock_seq = mm_lock_seq [marks VMA as busy]
up_write(&vma->vm_lock->lock)
vm_flags_init
[sets VM_UFFD_* in __vm_flags]
vma->vm_userfaultfd_ctx.ctx = ctx
mmap_write_unlock
vma_end_write_all
WRITE_ONCE(mm->mm_lock_seq, mm->mm_lock_seq + 1) [unlocks VMA]

There are no memory barriers in between the __vm_flags update and the
mm->mm_lock_seq update that unlocks the VMA, so the unlock can be
reordered to above the `vm_flags_init()` call, which means from the
perspective of a concurrent reader, a VMA can be marked as a userfaultfd
VMA while it is not VMA-locked. That's bad, we definitely need a
store-release for the unlock operation.

The non-atomic write to vma->vm_lock_seq in vma_start_write() is mostly
fine because all accesses to vma->vm_lock_seq that matter are always
protected by the VMA lock. There is a racy read in vma_start_read()
though that can tolerate false-positives, so we should be using
WRITE_ONCE() to keep things tidy and data-race-free (including for KCSAN).

On the other side, lock_vma_under_rcu() works as follows in the relevant
region for locking and userfaultfd check:

lock_vma_under_rcu
vma_start_read
vma->vm_lock_seq == READ_ONCE(vma->vm_mm->mm_lock_seq) [early bailout]
down_read_trylock(&vma->vm_lock->lock)
vma->vm_lock_seq == READ_ONCE(vma->vm_mm->mm_lock_seq) [main check]
userfaultfd_armed
checks vma->vm_flags & __VM_UFFD_FLAGS

Here, the interesting aspect is how far down the mm->mm_lock_seq read can
be reordered - if this read is reordered down below the vma->vm_flags
access, this could cause lock_vma_under_rcu() to partly operate on
information that was read while the VMA was supposed to be locked. To
prevent this kind of downwards bleeding of the mm->mm_lock_seq read, we
need to read it with a load-acquire.

Some of the comment wording is based on suggestions by Suren.

BACKPORT WARNING: One of the functions changed by this patch (which I've
written against Linus' tree) is vma_try_start_write(), but this function
no longer exists in mm/mm-everything. I don't know whether the merged
version of this patch will be ordered before or after the patch that
removes vma_try_start_write(). If you're backporting this patch to a tree
with vma_try_start_write(), make sure this patch changes that function.

Link: https://lkml.kernel.org/r/20230721225107.942336-1-jannh@google.com
Fixes: 5e31275cc997 ("mm: add per-VMA lock and helper functions to control it")
Signed-off-by: Jann Horn <jannh@google.com>
Reviewed-by: Suren Baghdasaryan <surenb@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: move mm_count into its own cache line

The mm_struct mm_count field is frequently updated by mmgrab/mmdrop
performed by context switch. This causes false-sharing for surrounding
mm_struct fields which are read-mostly.

This has been observed on a 2sockets/112core/224cpu Intel Sapphire Rapids
server running hackbench, and by the kernel test robot will-it-scale
testcase.

Move the mm_count field into its own cache line to prevent false-sharing
with other mm_struct fields.

Move mm_count to the first field of mm_struct to minimize the amount of
padding required: rather than adding padding before and after the mm_count
field, padding is only added after mm_count.

Note that I noticed this odd comment in mm_struct:

commit 2e3025434a6b ("mm: relocate 'write_protect_seq' in struct mm_struct")

/*
* With some kernel config, the current mmap_lock's offset
* inside 'mm_struct' is at 0x120, which is very optimal, as
* its two hot fields 'count' and 'owner' sit in 2 different
* cachelines, and when mmap_lock is highly contended, both
* of the 2 fields will be accessed frequently, current layout
* will help to reduce cache bouncing.
*
* So please be careful with adding new fields before
* mmap_lock, which can easily push the 2 fields into one
* cacheline.
*/
struct rw_semaphore mmap_lock;

This comment is rather odd for a few reasons:

- It requires addition/removal of mm_struct fields to carefully consider
field alignment of _other_ fields,
- It expresses the wish to keep an "optimal" alignment for a specific
kernel config.

I suspect that the author of this comment may want to revisit this topic
and perhaps introduce a split-struct approach for struct rw_semaphore,
if the need is to place various fields of this structure in different
cache lines.

Link: https://lkml.kernel.org/r/20230515143536.114960-1-mathieu.desnoyers@efficios.com
Fixes: 223baf9d17f2 ("sched: Fix performance regression introduced by mm_cid")
Fixes: af7f588d8f73 ("sched: Introduce per-memory-map concurrency ID")
Link: https://lore.kernel.org/lkml/7a0c1db1-103d-d518-ed96-1584a28fbf32@efficios.com
Reported-by: kernel test robot <yujie.liu@intel.com>
Link: https://lore.kernel.org/oe-lkp/202305151017.27581d75-yujie.liu@intel.com
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Reviewed-by: Aaron Lu <aaron.lu@intel.com>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Olivier Dion <odion@efficios.com>
Cc: <michael.christie@oracle.com>
Cc: Feng Tang <feng.tang@intel.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Peter Xu <peterx@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

sched: Fix performance regression introduced by mm_cid

Introduce per-mm/cpu current concurrency id (mm_cid) to fix a PostgreSQL
sysbench regression reported by Aaron Lu.

Keep track of the currently allocated mm_cid for each mm/cpu rather than
freeing them immediately on context switch. This eliminates most atomic
operations when context switching back and forth between threads
belonging to different memory spaces in multi-threaded scenarios (many
processes, each with many threads). The per-mm/per-cpu mm_cid values are
serialized by their respective runqueue locks.

Thread migration is handled by introducing invocation to
sched_mm_cid_migrate_to() (with destination runqueue lock held) in
activate_task() for migrating tasks. If the destination cpu's mm_cid is
unset, and if the source runqueue is not actively using its mm_cid, then
the source cpu's mm_cid is moved to the destination cpu on migration.

Introduce a task-work executed periodically, similarly to NUMA work,
which delays reclaim of cid values when they are unused for a period of
time.

Keep track of the allocation time for each per-cpu cid, and let the task
work clear them when they are observed to be older than
SCHED_MM_CID_PERIOD_NS and unused. This task work also clears all
mm_cids which are greater or equal to the Hamming weight of the mm
cidmask to keep concurrency ids compact.

Because we want to ensure the mm_cid converges towards the smaller
values as migrations happen, the prior optimization that was done when
context switching between threads belonging to the same mm is removed,
because it could delay the lazy release of the destination runqueue
mm_cid after it has been replaced by a migration. Removing this prior
optimization is not an issue performance-wise because the introduced
per-mm/per-cpu mm_cid tracking also covers this more specific case.

Fixes: af7f588d8f73 ("sched: Introduce per-memory-map concurrency ID")
Reported-by: Aaron Lu <aaron.lu@intel.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Aaron Lu <aaron.lu@intel.com>
Link: https://lore.kernel.org/lkml/20230327080502.GA570847@ziqianlu-desk2/

sched/numa: implement access PID reset logic

This helps to ensure that only recently accessed PIDs scan the VMAs.

Current implementation: (idea supported by PeterZ)

1. Accessing PID information is maintained in two windows.
access_pids[1] being newest.

2. Reset old access PID info i.e. access_pid[0] every (4 *
sysctl_numa_balancing_scan_delay) interval after initial scan delay
period expires.

The above interval seemed to be experimentally optimum since it avoids
frequent reset of access info as well as helps clearing the old access
info regularly. The reset logic is implemented in scan path.

Link: https://lkml.kernel.org/r/f7a675f66d1442d048b4216b2baf94515012c405.1677672277.git.raghavendra.kt@amd.com
Signed-off-by: Raghavendra K T <raghavendra.kt@amd.com>
Suggested-by: Mel Gorman <mgorman@techsingularity.net>
Cc: Bharata B Rao <bharata@amd.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Disha Talreja <dishaa.talreja@amd.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

sched/numa: enhance vma scanning logic

During Numa scanning make sure only relevant vmas of the tasks are
scanned.

Before:
All the tasks of a process participate in scanning the vma even if they
do not access vma in it's lifespan.

Now:
Except cases of first few unconditional scans, if a process do
not touch vma (exluding false positive cases of PID collisions)
tasks no longer scan all vma

Logic used:

1) 6 bits of PID used to mark active bit in vma numab status during
fault to remember PIDs accessing vma. (Thanks Mel)

2) Subsequently in scan path, vma scanning is skipped if current PID
had not accessed vma.

3) First two times we do allow unconditional scan to preserve earlier
behaviour of scanning.

Acknowledgement to Bharata B Rao <bharata@amd.com> for initial patch to
store pid information and Peter Zijlstra <peterz@infradead.org> (Usage of
test and set bit)

Link: https://lkml.kernel.org/r/092f03105c7c1d3450f4636b1ea350407f07640e.1677672277.git.raghavendra.kt@amd.com
Signed-off-by: Raghavendra K T <raghavendra.kt@amd.com>
Suggested-by: Mel Gorman <mgorman@techsingularity.net>
Cc: David Hildenbrand <david@redhat.com>
Cc: Disha Talreja <dishaa.talreja@amd.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Mike Rapoport <rppt@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

sched/numa: apply the scan delay to every new vma

Pach series "sched/numa: Enhance vma scanning", v3.

The patchset proposes one of the enhancements to numa vma scanning
suggested by Mel. This is continuation of [3].

Reposting the rebased patchset to akpm mm-unstable tree (March 1)

Existing mechanism of scan period involves, scan period derived from
per-thread stats. Process Adaptive autoNUMA [1] proposed to gather NUMA
fault stats at per-process level to capture aplication behaviour better.

During that course of discussion, Mel proposed several ideas to enhance
current numa balancing. One of the suggestion was below

Track what threads access a VMA. The suggestion was to use an unsigned
long pid_mask and use the lower bits to tag approximately what threads
access a VMA. Skip VMAs that did not trap a fault. This would be
approximate because of PID collisions but would reduce scanning of areas
the thread is not interested in. The above suggestion intends not to
penalize threads that has no interest in the vma, thus reduce scanning
overhead.

V3 changes are mostly based on PeterZ comments (details below in changes)

Summary of patchset:

Current patchset implements:

1. Delay the vma scanning logic for newly created VMA's so that
additional overhead of scanning is not incurred for short lived tasks
(implementation by Mel)

2. Store the information of tasks accessing VMA in 2 windows. It is
regularly cleared in (4*sysctl_numa_balancing_scan_delay) interval.
The above time is derived from experimenting (Suggested by PeterZ) to
balance between frequent clearing vs obsolete access data

3. hash_32 used to encode task index accessing VMA information

4. VMA's acess information is used to skip scanning for the tasks
which had not accessed VMA

Changes since V2:
patch1:
- Renaming of structure, macro to function,
- Add explanation to heuristics
- Adding more details from result (PeterZ)
Patch2:
- Usage of test and set bit (PeterZ)
- Move storing access PID info to numa_migrate_prep()
- Add a note on fainess among tasks allowed to scan
(PeterZ)
Patch3:
- Maintain two windows of access PID information
(PeterZ supported implementation and Gave idea to extend
to N if needed)
Patch4:
- Apply hash_32 function to track VMA accessing PIDs (PeterZ)

Changes since RFC V1:
- Include Mel's vma scan delay patch
- Change the accessing pid store logic (Thanks Mel)
- Fencing structure / code to NUMA_BALANCING (David, Mel)
- Adding clearing access PID logic (Mel)
- Descriptive change log ( Mike Rapoport)

Things to ponder over:
==========================================

- Improvement to clearing accessing PIDs logic (discussed in-detail in
patch3 itself (Done in this patchset by implementing 2 window history)

- Current scan period is not changed in the patchset, so we do see
frequent tries to scan. Relaxing scan period dynamically could improve
results further.

[1] sched/numa: Process Adaptive autoNUMA
Link: https://lore.kernel.org/lkml/20220128052851.17162-1-bharata@amd.com/T/

[2] RFC V1 Link:
https://lore.kernel.org/all/cover.1673610485.git.raghavendra.kt@amd.com/

[3] V2 Link:
https://lore.kernel.org/lkml/cover.1675159422.git.raghavendra.kt@amd.com/


Results:
Summary: Huge autonuma cost reduction seen in mmtest. Kernbench improvement
is more than 5% and huge system time (80%+) improvement from mmtest autonuma.
(dbench had huge std deviation to post)

kernbench
===========
6.2.0-mmunstable-base 6.2.0-mmunstable-patched
Amean user-256 22002.51 ( 0.00%) 22649.95 * -2.94%*
Amean syst-256 10162.78 ( 0.00%) 8214.13 * 19.17%*
Amean elsp-256 160.74 ( 0.00%) 156.92 * 2.38%*

Duration User 66017.43 67959.84
Duration System 30503.15 24657.03
Duration Elapsed 504.61 493.12

6.2.0-mmunstable-base 6.2.0-mmunstable-patched
Ops NUMA alloc hit 1738835089.00 1738780310.00
Ops NUMA alloc local 1738834448.00 1738779711.00
Ops NUMA base-page range updates 477310.00 392566.00
Ops NUMA PTE updates 477310.00 392566.00
Ops NUMA hint faults 96817.00 87555.00
Ops NUMA hint local faults % 10150.00 2192.00
Ops NUMA hint local percent 10.48 2.50
Ops NUMA pages migrated 86660.00 85363.00
Ops AutoNUMA cost 489.07 442.14

autonumabench
===============
6.2.0-mmunstable-base 6.2.0-mmunstable-patched
Amean syst-NUMA01 399.50 ( 0.00%) 52.05 * 86.97%*
Amean syst-NUMA01_THREADLOCAL 0.21 ( 0.00%) 0.22 * -5.41%*
Amean syst-NUMA02 0.80 ( 0.00%) 0.78 * 2.68%*
Amean syst-NUMA02_SMT 0.65 ( 0.00%) 0.68 * -3.95%*
Amean elsp-NUMA01 313.26 ( 0.00%) 313.11 * 0.05%*
Amean elsp-NUMA01_THREADLOCAL 1.06 ( 0.00%) 1.08 * -1.76%*
Amean elsp-NUMA02 3.19 ( 0.00%) 3.24 * -1.52%*
Amean elsp-NUMA02_SMT 3.72 ( 0.00%) 3.61 * 2.92%*

Duration User 396433.47 324835.96
Duration System 2808.70 376.66
Duration Elapsed 2258.61 2258.12

6.2.0-mmunstable-base 6.2.0-mmunstable-patched
Ops NUMA alloc hit 59921806.00 49623489.00
Ops NUMA alloc miss 0.00 0.00
Ops NUMA interleave hit 0.00 0.00
Ops NUMA alloc local 59920880.00 49622594.00
Ops NUMA base-page range updates 152259275.00 50075.00
Ops NUMA PTE updates 152259275.00 50075.00
Ops NUMA PMD updates 0.00 0.00
Ops NUMA hint faults 154660352.00 39014.00
Ops NUMA hint local faults % 138550501.00 23139.00
Ops NUMA hint local percent 89.58 59.31
Ops NUMA pages migrated 8179067.00 14147.00
Ops AutoNUMA cost 774522.98 195.69


This patch (of 4):

Currently whenever a new task is created we wait for
sysctl_numa_balancing_scan_delay to avoid unnessary scanning overhead.
Extend the same logic to new or very short-lived VMAs.

[raghavendra.kt@amd.com: add initialization in vm_area_dup())]
Link: https://lkml.kernel.org/r/cover.1677672277.git.raghavendra.kt@amd.com
Link: https://lkml.kernel.org/r/7a6fbba87c8b51e67efd3e74285bb4cb311a16ca.1677672277.git.raghavendra.kt@amd.com
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Raghavendra K T <raghavendra.kt@amd.com>
Cc: Bharata B Rao <bharata@amd.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Disha Talreja <dishaa.talreja@amd.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: separate vma->lock from vm_area_struct

vma->lock being part of the vm_area_struct causes performance regression
during page faults because during contention its count and owner fields
are constantly updated and having other parts of vm_area_struct used
during page fault handling next to them causes constant cache line
bouncing. Fix that by moving the lock outside of the vm_area_struct.

All attempts to keep vma->lock inside vm_area_struct in a separate cache
line still produce performance regression especially on NUMA machines.
Smallest regression was achieved when lock is placed in the fourth cache
line but that bloats vm_area_struct to 256 bytes.

Considering performance and memory impact, separate lock looks like the
best option. It increases memory footprint of each VMA but that can be
optimized later if the new size causes issues. Note that after this
change vma_init() does not allocate or initialize vma->lock anymore. A
number of drivers allocate a pseudo VMA on the stack but they never use
the VMA's lock, therefore it does not need to be allocated. The future
drivers which might need the VMA lock should use
vm_area_alloc()/vm_area_free() to allocate the VMA.

Link: https://lkml.kernel.org/r/20230227173632.3292573-34-surenb@google.com
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: add FAULT_FLAG_VMA_LOCK flag

Add a new flag to distinguish page faults handled under protection of
per-vma lock.

[surenb@google.com: document FAULT_FLAG_VMA_LOCK flag]
Link: https://lkml.kernel.org/r/20230301022720.1380780-2-surenb@google.com
Link: https://lore.kernel.org/all/20230301113648.7c279865@canb.auug.org.au/
Link: https://lkml.kernel.org/r/20230227173632.3292573-26-surenb@google.com
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Reviewed-by: Laurent Dufour <laurent.dufour@fr.ibm.com>
Cc: Dan Carpenter <error27@gmail.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Yu Zhao <yuzhao@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: introduce vma detached flag

Per-vma locking mechanism will search for VMA under RCU protection and
then after locking it, has to ensure it was not removed from the VMA tree
after we found it. To make this check efficient, introduce a
vma->detached flag to mark VMAs which were removed from the VMA tree.

Link: https://lkml.kernel.org/r/20230227173632.3292573-23-surenb@google.com
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: add per-VMA lock and helper functions to control it

Introduce per-VMA locking. The lock implementation relies on a per-vma
and per-mm sequence counters to note exclusive locking:

- read lock - (implemented by vma_start_read) requires the vma
(vm_lock_seq) and mm (mm_lock_seq) sequence counters to differ.
If they match then there must be a vma exclusive lock held somewhere.
- read unlock - (implemented by vma_end_read) is a trivial vma->lock
unlock.
- write lock - (vma_start_write) requires the mmap_lock to be held
exclusively and the current mm counter is assigned to the vma counter.
This will allow multiple vmas to be locked under a single mmap_lock
write lock (e.g. during vma merging). The vma counter is modified
under exclusive vma lock.
- write unlock - (vma_end_write_all) is a batch release of all vma
locks held. It doesn't pair with a specific vma_start_write! It is
done before exclusive mmap_lock is released by incrementing mm
sequence counter (mm_lock_seq).
- write downgrade - if the mmap_lock is downgraded to the read lock, all
vma write locks are released as well (effectivelly same as write
unlock).

Link: https://lkml.kernel.org/r/20230227173632.3292573-13-surenb@google.com
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: rcu safe VMA freeing

This prepares for page faults handling under VMA lock, looking up VMAs
under protection of an rcu read lock, instead of the usual mmap read lock.

Link: https://lkml.kernel.org/r/20230227173632.3292573-11-surenb@google.com
Signed-off-by: Michel Lespinasse <michel@lespinasse.org>
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: remove unused vmf_insert_mixed_prot()

Patch series "Remove drm/ttm-specific mm changes".

Functionality was added specifically for the DRM TTM driver to support
mapping memory for VM_MIXEDMAP VMAs with customised protection flags,
however this has now been rolled back as issues were found with this
approach.

This series removes the mm changes too, retaining some of the useful
comments.


This patch (of 3):

The sole user of vmf_insert_mixed_prot(), the drm ttm module, stopped
using this in commit f91142c62161 ("drm/ttm: nuke VM_MIXEDMAP on BO
mappings v3") citing use of VM_MIXEDMAP in this case being terribly
broken.

Remove this now-dead code and references to it, but retain the useful
description of the prot != vma->vm_page_prot case, moving it to
vmf_insert_pfn_prot() instead.

Link: https://lkml.kernel.org/r/cover.1678661628.git.lstoakes@gmail.com
Link: https://lkml.kernel.org/r/a069644388e6f1593a7020d15840e6fc9f39bcaf.1678661628.git.lstoakes@gmail.com
Signed-off-by: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Christian König <christian.koenig@amd.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Aaron Tomlin <atomlin@atomlin.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Frederic Weisbecker <frederic@kernel.org>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Huacai Chen <chenhuacai@kernel.org>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: "Russell King (Oracle)" <linux@armlinux.org.uk>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: enable maple tree RCU mode by default

Use the maple tree in RCU mode for VMA tracking.

The maple tree tracks the stack and is able to update the pivot
(lower/upper boundary) in-place to allow the page fault handler to write
to the tree while holding just the mmap read lock. This is safe as the
writes to the stack have a guard VMA which ensures there will always be a
NULL in the direction of the growth and thus will only update a pivot.

It is possible, but not recommended, to have VMAs that grow up/down
without guard VMAs. syzbot has constructed a testcase which sets up a VMA
to grow and consume the empty space. Overwriting the entire NULL entry
causes the tree to be altered in a way that is not safe for concurrent
readers; the readers may see a node being rewritten or one that does not
match the maple state they are using.

Enabling RCU mode allows the concurrent readers to see a stable node and
will return the expected result.

[Liam.Howlett@Oracle.com: we don't need to free the nodes with RCU[
Link: https://lore.kernel.org/linux-mm/000000000000b0a65805f663ace6@google.com/
Link: https://lkml.kernel.org/r/20230227173632.3292573-9-surenb@google.com
Fixes: d4af56c5c7c6 ("mm: start tracking VMAs with maple tree")
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Reported-by: syzbot+8d95422d3537159ca390@syzkaller.appspotmail.com
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/gup: move private gup FOLL_ flags to internal.h

Move the flags that should not/are not used outside gup.c and related into
mm/internal.h to discourage driver abuse.

To make this more maintainable going forward compact the two FOLL ranges
with new bit numbers from 0 to 11 and 16 to 21, using shifts so it is
explicit.

Switch to an enum so the whole thing is easier to read.

Link: https://lkml.kernel.org/r/13-v2-987e91b59705+36b-gup_tidy_jgg@nvidia.com
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Claudio Imbrenda <imbrenda@linux.ibm.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Mike Rapoport (IBM) <rppt@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/gup: add FOLL_UNLOCKABLE

Setting FOLL_UNLOCKABLE allows GUP to lock/unlock the mmap lock on its
own. It is a more explicit replacement for locked != NULL. This clears
the way for passing in locked = 1, without intending that the lock can be
unlocked.

Set the flag in all cases where it is used, eg locked is present in the
external interface or locked is used internally with locked = 0.

Link: https://lkml.kernel.org/r/8-v2-987e91b59705+36b-gup_tidy_jgg@nvidia.com
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Acked-by: Mike Rapoport (IBM) <rppt@kernel.org>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Claudio Imbrenda <imbrenda@linux.ibm.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/gup: remove obsolete FOLL_LONGTERM comment

These days FOLL_LONGTERM is not allowed at all on any get_user_pages*()
functions, it must be only be used with pin_user_pages*(), plus it now has
universal support for all the pin_user_pages*() functions.

Link: https://lkml.kernel.org/r/2-v2-987e91b59705+36b-gup_tidy_jgg@nvidia.com
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Claudio Imbrenda <imbrenda@linux.ibm.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Mike Rapoport (IBM) <rppt@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: introduce vma->vm_flags wrapper functions

vm_flags are among VMA attributes which affect decisions like VMA merging
and splitting. Therefore all vm_flags modifications are performed after
taking exclusive mmap_lock to prevent vm_flags updates racing with such
operations. Introduce modifier functions for vm_flags to be used whenever
flags are updated. This way we can better check and control correct
locking behavior during these updates.

Link: https://lkml.kernel.org/r/20230126193752.297968-3-surenb@google.com
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Reviewed-by: Davidlohr Bueso <dave@stgolabs.net>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Mike Rapoport (IBM) <rppt@kernel.org>
Reviewed-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arjun Roy <arjunroy@google.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jann Horn <jannh@google.com>
Cc: Joel Fernandes <joelaf@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kent Overstreet <kent.overstreet@linux.dev>
Cc: Laurent Dufour <ldufour@linux.ibm.com>
Cc: Liam R. Howlett <Liam.Howlett@Oracle.com>
Cc: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Minchan Kim <minchan@google.com>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Peter Oskolkov <posk@google.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Punit Agrawal <punit.agrawal@bytedance.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Sebastian Reichel <sebastian.reichel@collabora.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Soheil Hassas Yeganeh <soheil@google.com>
Cc: Song Liu <songliubraving@fb.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: expand vma iterator interface

Add wrappers for the maple tree to the vma iterator. This will provide
type safety at compile time.

Link: https://lkml.kernel.org/r/20230120162650.984577-8-Liam.Howlett@oracle.com
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: remove the hugetlb field from struct page

Patch series "Get rid of tail page fields".

Continue the shrinkage of the struct page definition by getting rid of the
'first tail page' and 'second tail page' fields. I originally did this
patch set before Hugh's rewrite of the subpages_mapcount, so it needed
substantial updates; hope I didn't miss anything.


This patch (of 28):

commit dad6a5eb5556(mm,hugetlb: use folio fields in second tail page)
added a transitional hugetlb field to struct page and struct folio to make
room for another int in the first tail of a compound page. Hugetlb folio
conversions have changed all page users of this field to use the fields
within the folio so struct page no longer needs this hugetlb specific
field.

Link: https://lkml.kernel.org/r/20230111142915.1001531-1-willy@infradead.org
Link: https://lkml.kernel.org/r/20230111142915.1001531-29-willy@infradead.org
Signed-off-by: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: move page->deferred_list to folio->_deferred_list

Remove the entire block of definitions for the second tail page, and add
the deferred list to the struct folio. This actually moves _deferred_list
to a different offset in struct folio because I don't see a need to
include the padding.

This lets us use list_for_each_entry_safe() in deferred_split_scan()
and avoid a number of calls to compound_head().

Link: https://lkml.kernel.org/r/20230111142915.1001531-25-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

doc: correct struct folio kernel-doc

Insert appropriate public: and private: markers to make the generated
kernel-doc look right.

Link: https://lkml.kernel.org/r/20230111142915.1001531-24-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: remove 'First tail page' members from struct page

All former users now use the folio equivalents, so remove them from the
definition of struct page.

Link: https://lkml.kernel.org/r/20230111142915.1001531-23-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: remove head_compound_mapcount() and _ptr functions

folio_mapcount_ptr(), compound_mapcount_ptr() and subpages_mapcount_ptr()
are all now unused.

Link: https://lkml.kernel.org/r/20230111142915.1001531-16-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: convert total_compound_mapcount() to folio_total_mapcount()

Instead of enforcing that the argument must be a head page by naming,
enforce it with the compiler by making it a folio. Also rename the
counter in struct folio from _compound_mapcount to _entire_mapcount.

Link: https://lkml.kernel.org/r/20230111142915.1001531-5-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: convert head_subpages_mapcount() into folio_nr_pages_mapped()

Calling this 'mapcount' is confusing since mapcount is usually the number
of times something is mapped; instead this is the number of mapped pages.
It's also better to enforce that this is a folio rather than a head page.

Move folio_nr_pages_mapped() into mm/internal.h since this is not
something we want device drivers or filesystems poking at. Get rid of
folio_subpages_mapcount_ptr() and use folio->_nr_pages_mapped directly.

Link: https://lkml.kernel.org/r/20230111142915.1001531-3-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: remove folio_pincount_ptr() and head_compound_pincount()

We can use folio->_pincount directly, since all users are guarded by tests
of compound/large.

Link: https://lkml.kernel.org/r/20230111142915.1001531-2-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: fix comment of page table counter

Commit af5b0f6a09e42 ("mm: consolidate page table accounting")
consolidates page table accounting to a single counter in struct mm_struct
{} as mm->pgtables_bytes. So the meanning of this counter should be the
size of all page tables now.

Link: https://lkml.kernel.org/r/20221224060233.417827-1-kele.huang@columbia.edu
Signed-off-by: Kele Huang <kele.huang@columbia.edu>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Colin Cross <ccross@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Yu Zhao <yuzhao@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: move FOLL_* defs to mm_types.h

Move FOLL_* definitions to linux/mm_types.h to make them more accessible
without having to drag in all of linux/mm.h and everything that drags in
too[1].

Link: https://lkml.kernel.org/r/2161258.1671657894@warthog.procyon.org.uk
Signed-off-by: David Howells <dhowells@redhat.com>
Suggested-by: Matthew Wilcox <willy@infradead.org>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

sched: Introduce per-memory-map concurrency ID

This feature allows the scheduler to expose a per-memory map concurrency
ID to user-space. This concurrency ID is within the possible cpus range,
and is temporarily (and uniquely) assigned while threads are actively
running within a memory map. If a memory map has fewer threads than
cores, or is limited to run on few cores concurrently through sched
affinity or cgroup cpusets, the concurrency IDs will be values close
to 0, thus allowing efficient use of user-space memory for per-cpu
data structures.

This feature is meant to be exposed by a new rseq thread area field.

The primary purpose of this feature is to do the heavy-lifting needed
by memory allocators to allow them to use per-cpu data structures
efficiently in the following situations:

- Single-threaded applications,
- Multi-threaded applications on large systems (many cores) with limited
cpu affinity mask,
- Multi-threaded applications on large systems (many cores) with
restricted cgroup cpuset per container.

One of the key concern from scheduler maintainers is the overhead
associated with additional spin locks or atomic operations in the
scheduler fast-path. This is why the following optimization is
implemented.

On context switch between threads belonging to the same memory map,
transfer the mm_cid from prev to next without any atomic ops. This
takes care of use-cases involving frequent context switch between
threads belonging to the same memory map.

Additional optimizations can be done if the spin locks added when
context switching between threads belonging to different memory maps end
up being a performance bottleneck. Those are left out of this patch
though. A performance impact would have to be clearly demonstrated to
justify the added complexity.

The credit goes to Paul Turner (Google) for the original virtual cpu id
idea. This feature is implemented based on the discussions with Paul
Turner and Peter Oskolkov (Google), but I took the liberty to implement
scheduler fast-path optimizations and my own NUMA-awareness scheme. The
rumor has it that Google have been running a rseq vcpu_id extension
internally in production for a year. The tcmalloc source code indeed has
comments hinting at a vcpu_id prototype extension to the rseq system
call [1].

The following benchmarks do not show any significant overhead added to
the scheduler context switch by this feature:

* perf bench sched messaging (process)

Baseline: 86.5±0.3 ms
With mm_cid: 86.7±2.6 ms

* perf bench sched messaging (threaded)

Baseline: 84.3±3.0 ms
With mm_cid: 84.7±2.6 ms

* hackbench (process)

Baseline: 82.9±2.7 ms
With mm_cid: 82.9±2.9 ms

* hackbench (threaded)

Baseline: 85.2±2.6 ms
With mm_cid: 84.4±2.9 ms

[1] https://github.com/google/tcmalloc/blob/master/tcmalloc/internal/linux_syscall_support.h#L26

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20221122203932.231377-8-mathieu.desnoyers@efficios.com

mm: update mmap_sem comments to refer to mmap_lock

The rename from mm->mmap_sem to mm->mmap_lock was performed in commit
da1c55f1b272 ("mmap locking API: rename mmap_sem to mmap_lock") and commit
c1e8d7c6a7a6 ("map locking API: convert mmap_sem comments"), however some
incorrect comments remain.

This patch simply corrects those comments which are obviously incorrect
within mm itself.

Link: https://lkml.kernel.org/r/33fba04389ab63fc4980e7ba5442f521df6dc657.1673048927.git.lstoakes@gmail.com
Signed-off-by: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

fsdax: introduce page->share for fsdax in reflink mode

Patch series "fsdax,xfs: fix warning messages", v2.

Many testcases failed in dax+reflink mode with warning message in dmesg.
Such as generic/051,075,127. The warning message is like this:
[ 775.509337] ------------[ cut here ]------------
[ 775.509636] WARNING: CPU: 1 PID: 16815 at fs/dax.c:386 dax_insert_entry.cold+0x2e/0x69
[ 775.510151] Modules linked in: auth_rpcgss oid_registry nfsv4 algif_hash af_alg af_packet nft_reject_inet nf_reject_ipv4 nf_reject_ipv6 nft_reject nft_ct nft_chain_nat iptable_nat nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 ip_set nf_tables nfnetlink ip6table_filter ip6_tables iptable_filter ip_tables x_tables dax_pmem nd_pmem nd_btt sch_fq_codel configfs xfs libcrc32c fuse
[ 775.524288] CPU: 1 PID: 16815 Comm: fsx Kdump: loaded Tainted: G W 6.1.0-rc4+ #164 eb34e4ee4200c7cbbb47de2b1892c5a3e027fd6d
[ 775.524904] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS Arch Linux 1.16.0-3-3 04/01/2014
[ 775.525460] RIP: 0010:dax_insert_entry.cold+0x2e/0x69
[ 775.525797] Code: c7 c7 18 eb e0 81 48 89 4c 24 20 48 89 54 24 10 e8 73 6d ff ff 48 83 7d 18 00 48 8b 54 24 10 48 8b 4c 24 20 0f 84 e3 e9 b9 ff <0f> 0b e9 dc e9 b9 ff 48 c7 c6 a0 20 c3 81 48 c7 c7 f0 ea e0 81 48
[ 775.526708] RSP: 0000:ffffc90001d57b30 EFLAGS: 00010082
[ 775.527042] RAX: 000000000000002a RBX: 0000000000000000 RCX: 0000000000000042
[ 775.527396] RDX: ffffea000a0f6c80 RSI: ffffffff81dfab1b RDI: 00000000ffffffff
[ 775.527819] RBP: ffffea000a0f6c40 R08: 0000000000000000 R09: ffffffff820625e0
[ 775.528241] R10: ffffc90001d579d8 R11: ffffffff820d2628 R12: ffff88815fc98320
[ 775.528598] R13: ffffc90001d57c18 R14: 0000000000000000 R15: 0000000000000001
[ 775.528997] FS: 00007f39fc75d740(0000) GS:ffff88817bc80000(0000) knlGS:0000000000000000
[ 775.529474] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 775.529800] CR2: 00007f39fc772040 CR3: 0000000107eb6001 CR4: 00000000003706e0
[ 775.530214] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 775.530592] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 775.531002] Call Trace:
[ 775.531230] <TASK>
[ 775.531444] dax_fault_iter+0x267/0x6c0
[ 775.531719] dax_iomap_pte_fault+0x198/0x3d0
[ 775.532002] __xfs_filemap_fault+0x24a/0x2d0 [xfs aa8d25411432b306d9554da38096f4ebb86bdfe7]
[ 775.532603] __do_fault+0x30/0x1e0
[ 775.532903] do_fault+0x314/0x6c0
[ 775.533166] __handle_mm_fault+0x646/0x1250
[ 775.533480] handle_mm_fault+0xc1/0x230
[ 775.533810] do_user_addr_fault+0x1ac/0x610
[ 775.534110] exc_page_fault+0x63/0x140
[ 775.534389] asm_exc_page_fault+0x22/0x30
[ 775.534678] RIP: 0033:0x7f39fc55820a
[ 775.534950] Code: 00 01 00 00 00 74 99 83 f9 c0 0f 87 7b fe ff ff c5 fe 6f 4e 20 48 29 fe 48 83 c7 3f 49 8d 0c 10 48 83 e7 c0 48 01 fe 48 29 f9 <f3> a4 c4 c1 7e 7f 00 c4 c1 7e 7f 48 20 c5 f8 77 c3 0f 1f 44 00 00
[ 775.535839] RSP: 002b:00007ffc66a08118 EFLAGS: 00010202
[ 775.536157] RAX: 00007f39fc772001 RBX: 0000000000042001 RCX: 00000000000063c1
[ 775.536537] RDX: 0000000000006400 RSI: 00007f39fac42050 RDI: 00007f39fc772040
[ 775.536919] RBP: 0000000000006400 R08: 00007f39fc772001 R09: 0000000000042000
[ 775.537304] R10: 0000000000000001 R11: 0000000000000246 R12: 0000000000000001
[ 775.537694] R13: 00007f39fc772000 R14: 0000000000006401 R15: 0000000000000003
[ 775.538086] </TASK>
[ 775.538333] ---[ end trace 0000000000000000 ]---

This also affects dax+noreflink mode if we run the test after a
dax+reflink test. So, the most urgent thing is solving the warning
messages.

With these fixes, most warning messages in dax_associate_entry() are gone.
But honestly, generic/388 will randomly failed with the warning. The
case shutdown the xfs when fsstress is running, and do it for many times.
I think the reason is that dax pages in use are not able to be invalidated
in time when fs is shutdown. The next time dax page to be associated, it
still remains the mapping value set last time. I'll keep on solving it.

The warning message in dax_writeback_one() can also be fixed because of
the dax unshare.


This patch (of 8):

fsdax page is used not only when CoW, but also mapread. To make the it
easily understood, use 'share' to indicate that the dax page is shared by
more than one extent. And add helper functions to use it.

Also, the flag needs to be renamed to PAGE_MAPPING_DAX_SHARED.

[ruansy.fnst@fujitsu.com: rename several functions]
Link: https://lkml.kernel.org/r/1669972991-246-1-git-send-email-ruansy.fnst@fujitsu.com
[ruansy.fnst@fujitsu.com: v2.2]
Link: https://lkml.kernel.org/r/1670381359-53-1-git-send-email-ruansy.fnst@fujitsu.com
Link: https://lkml.kernel.org/r/1669908538-55-1-git-send-email-ruansy.fnst@fujitsu.com
Link: https://lkml.kernel.org/r/1669908538-55-2-git-send-email-ruansy.fnst@fujitsu.com
Signed-off-by: Shiyang Ruan <ruansy.fnst@fujitsu.com>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: remove VM_FAULT_WRITE

All users -- GUP and KSM -- are gone, let's just remove it.

Link: https://lkml.kernel.org/r/20221021101141.84170-4-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Acked-by: Peter Xu <peterx@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: extend FAULT_FLAG_UNSHARE support to anything in a COW mapping

Extend FAULT_FLAG_UNSHARE to break COW on anything mapped into a
COW (i.e., private writable) mapping and adjust the documentation
accordingly.

FAULT_FLAG_UNSHARE will now also break COW when encountering the shared
zeropage, a pagecache page, a PFNMAP, ... inside a COW mapping, by
properly replacing the mapped page/pfn by a private copy (an exclusive
anonymous page).

Note that only do_wp_page() needs care: hugetlb_wp() already handles
FAULT_FLAG_UNSHARE correctly. wp_huge_pmd()/wp_huge_pud() also handles it
correctly, for example, splitting the huge zeropage on FAULT_FLAG_UNSHARE
such that we can handle FAULT_FLAG_UNSHARE on the PTE level.

This change is a requirement for reliable long-term R/O pinning in
COW mappings.

Link: https://lkml.kernel.org/r/20221116102659.70287-9-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: anonymous shared memory naming

Since commit 9a10064f5625 ("mm: add a field to store names for private
anonymous memory"), name for private anonymous memory, but not shared
anonymous, can be set. However, naming shared anonymous memory just as
useful for tracking purposes.

Extend the functionality to be able to set names for shared anon.

There are two ways to create anonymous shared memory, using memfd or
directly via mmap():
1. fd = memfd_create(...)
mem = mmap(..., MAP_SHARED, fd, ...)
2. mem = mmap(..., MAP_SHARED | MAP_ANONYMOUS, -1, ...)

In both cases the anonymous shared memory is created the same way by
mapping an unlinked file on tmpfs.

The memfd way allows to give a name for anonymous shared memory, but
not useful when parts of shared memory require to have distinct names.

Example use case: The VMM maps VM memory as anonymous shared memory (not
private because VMM is sandboxed and drivers are running in their own
processes). However, the VM tells back to the VMM how parts of the memory
are actually used by the guest, how each of the segments should be backed
(i.e. 4K pages, 2M pages), and some other information about the segments.
The naming allows us to monitor the effective memory footprint for each
of these segments from the host without looking inside the guest.

Sample output:
/* Create shared anonymous segmenet */
anon_shmem = mmap(NULL, SIZE, PROT_READ | PROT_WRITE,
MAP_SHARED | MAP_ANONYMOUS, -1, 0);
/* Name the segment: "MY-NAME" */
rv = prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME,
anon_shmem, SIZE, "MY-NAME");

cat /proc/<pid>/maps (and smaps):
7fc8e2b4c000-7fc8f2b4c000 rw-s 00000000 00:01 1024 [anon_shmem:MY-NAME]

If the segment is not named, the output is:
7fc8e2b4c000-7fc8f2b4c000 rw-s 00000000 00:01 1024 /dev/zero (deleted)

Link: https://lkml.kernel.org/r/20221115020602.804224-1-pasha.tatashin@soleen.com
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Bagas Sanjaya <bagasdotme@gmail.com>
Cc: Colin Cross <ccross@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: "Kirill A . Shutemov" <kirill@shutemov.name>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>
Cc: Vincent Whitchurch <vincent.whitchurch@axis.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: xu xin <cgel.zte@gmail.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Yu Zhao <yuzhao@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: introduce 'encoded' page pointers with embedded extra bits

We already have this notion in parts of the MM code (see the mlock code
with the LRU_PAGE and NEW_PAGE bits), but I'm going to introduce a new
case, and I refuse to do the same thing we've done before where we just
put bits in the raw pointer and say it's still a normal pointer.

So this introduces a 'struct encoded_page' pointer that cannot be used for
anything else than to encode a real page pointer and a couple of extra
bits in the low bits. That way the compiler can trivially track the state
of the pointer and you just explicitly encode and decode the extra bits.

Note that this makes the alignment of 'struct page' explicit even for the
case where CONFIG_HAVE_ALIGNED_STRUCT_PAGE is not set. That is entirely
redundant in almost all cases, since the page structure already contains
several word-sized entries.

However, on m68k, the alignment of even 32-bit data is just 16 bits, and
as such in theory the alignment of 'struct page' could be too. So let's
just make it very very explicit that the alignment needs to be at least 32
bits, giving us a guarantee of two unused low bits in the pointer.

Now, in practice, our page struct array is aligned much more than that
anyway, even on m68k, and our existing code in mm/mlock.c obviously
already depended on that. But since the whole point of this change is to
be careful about the type system when hiding extra bits in the pointer,
let's also be explicit about the assumptions we make.

NOTE! This is being very careful in another way too: it has a build-time
assertion that the 'flags' added to the page pointer actually fit in the
two bits. That means that this helper must be inlined, and can only be
used in contexts where the compiler can statically determine that the
value fits in the available bits.

[akpm@linux-foundation.org: kerneldoc on a forward-declared struct confuses htmldocs]
Link: https://lore.kernel.org/all/Y2tKixpO4RO6DgW5@tuxmaker.boeblingen.de.ibm.com/
Link: https://lkml.kernel.org/r/20221109203051.1835763-1-torvalds@linux-foundation.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Hugh Dickins <hughd@google.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Cc: Heiko Carstens <hca@linux.ibm.com> [s390]
Cc: Nadav Amit <nadav.amit@gmail.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm,thp,rmap: simplify compound page mapcount handling

Compound page (folio) mapcount calculations have been different for anon
and file (or shmem) THPs, and involved the obscure PageDoubleMap flag.
And each huge mapping and unmapping of a file (or shmem) THP involved
atomically incrementing and decrementing the mapcount of every subpage of
that huge page, dirtying many struct page cachelines.

Add subpages_mapcount field to the struct folio and first tail page, so
that the total of subpage mapcounts is available in one place near the
head: then page_mapcount() and total_mapcount() and page_mapped(), and
their folio equivalents, are so quick that anon and file and hugetlb don't
need to be optimized differently. Delete the unloved PageDoubleMap.

page_add and page_remove rmap functions must now maintain the
subpages_mapcount as well as the subpage _mapcount, when dealing with pte
mappings of huge pages; and correct maintenance of NR_ANON_MAPPED and
NR_FILE_MAPPED statistics still needs reading through the subpages, using
nr_subpages_unmapped() - but only when first or last pmd mapping finds
subpages_mapcount raised (double-map case, not the common case).

But are those counts (used to decide when to split an anon THP, and in
vmscan's pagecache_reclaimable heuristic) correctly maintained? Not
quite: since page_remove_rmap() (and also split_huge_pmd()) is often
called without page lock, there can be races when a subpage pte mapcount
0<->1 while compound pmd mapcount 0<->1 is scanning - races which the
previous implementation had prevented. The statistics might become
inaccurate, and even drift down until they underflow through 0. That is
not good enough, but is better dealt with in a followup patch.

Update a few comments on first and second tail page overlaid fields.
hugepage_add_new_anon_rmap() has to "increment" compound_mapcount, but
subpages_mapcount and compound_pincount are already correctly at 0, so
delete its reinitialization of compound_pincount.

A simple 100 X munmap(mmap(2GB, MAP_SHARED|MAP_POPULATE, tmpfs), 2GB) took
18 seconds on small pages, and used to take 1 second on huge pages, but
now takes 119 milliseconds on huge pages. Mapping by pmds a second time
used to take 860ms and now takes 92ms; mapping by pmds after mapping by
ptes (when the scan is needed) used to take 870ms and now takes 495ms.
But there might be some benchmarks which would show a slowdown, because
tail struct pages now fall out of cache until final freeing checks them.

Link: https://lkml.kernel.org/r/47ad693-717-79c8-e1ba-46c3a6602e48@google.com
Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: James Houghton <jthoughton@google.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mina Almasry <almasrymina@google.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Naoya Horiguchi <naoya.horiguchi@linux.dev>
Cc: Peter Xu <peterx@redhat.com>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Zach O'Keefe <zokeefe@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm,hugetlb: use folio fields in second tail page

Patch series "mm,huge,rmap: unify and speed up compound mapcounts".


This patch (of 3):

We want to declare one more int in the first tail of a compound page: that
first tail page being valuable property, since every compound page has a
first tail, but perhaps no more than that.

No problem on 64-bit: there is already space for it. No problem with
32-bit THPs: 5.18 commit 5232c63f46fd ("mm: Make compound_pincount always
available") kindly cleared the space for it, apparently not realizing that
only 64-bit architectures enable CONFIG_THP_SWAP (whose use of tail
page->private might conflict) - but make sure of that in its Kconfig.

But hugetlb pages use tail page->private of the first tail page for a
subpool pointer, which will conflict; and they also use page->private of
the 2nd, 3rd and 4th tails.

Undo "mm: add private field of first tail to struct page and struct
folio"'s recent addition of private_1 to the folio tail: instead add
hugetlb_subpool, hugetlb_cgroup, hugetlb_cgroup_rsvd, hugetlb_hwpoison to
a second tail page of the folio: THP has long been using several fields of
that tail, so make better use of it for hugetlb too. This is not how a
generic folio should be declared in future, but it is an effective
transitional way to make use of it.

Delete the SUBPAGE_INDEX stuff, but keep __NR_USED_SUBPAGE: now 3.

[hughd@google.com: prefix folio's page_1 and page_2 with double underscore,
give folio's _flags_2 and _head_2 a line documentation each]
Link: https://lkml.kernel.org/r/9e2cb6b-5b58-d3f2-b5ee-5f8a14e8f10@google.com
Link: https://lkml.kernel.org/r/5f52de70-975-e94f-f141-543765736181@google.com
Link: https://lkml.kernel.org/r/3818cc9a-9999-d064-d778-9c94c5911e6@google.com
Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: James Houghton <jthoughton@google.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mina Almasry <almasrymina@google.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Naoya Horiguchi <naoya.horiguchi@linux.dev>
Cc: Peter Xu <peterx@redhat.com>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Zach O'Keefe <zokeefe@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: convert mm's rss stats into percpu_counter

Currently mm_struct maintains rss_stats which are updated on page fault
and the unmapping codepaths. For page fault codepath the updates are
cached per thread with the batch of TASK_RSS_EVENTS_THRESH which is 64.
The reason for caching is performance for multithreaded applications
otherwise the rss_stats updates may become hotspot for such applications.

However this optimization comes with the cost of error margin in the rss
stats. The rss_stats for applications with large number of threads can be
very skewed. At worst the error margin is (nr_threads * 64) and we have a
lot of applications with 100s of threads, so the error margin can be very
high. Internally we had to reduce TASK_RSS_EVENTS_THRESH to 32.

Recently we started seeing the unbounded errors for rss_stats for specific
applications which use TCP rx0cp. It seems like vm_insert_pages()
codepath does not sync rss_stats at all.

This patch converts the rss_stats into percpu_counter to convert the error
margin from (nr_threads * 64) to approximately (nr_cpus ^ 2). However
this conversion enable us to get the accurate stats for situations where
accuracy is more important than the cpu cost.

This patch does not make such tradeoffs - we can just use
percpu_counter_add_local() for the updates and percpu_counter_sum() (or
percpu_counter_sync() + percpu_counter_read) for the readers. At the
moment the readers are either procfs interface, oom_killer and memory
reclaim which I think are not performance critical and should be ok with
slow read. However I think we can make that change in a separate patch.

Link: https://lkml.kernel.org/r/20221024052841.3291983-1-shakeelb@google.com
Signed-off-by: Shakeel Butt <shakeelb@google.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: add private field of first tail to struct page and struct folio

Allow struct folio to store hugetlb metadata that is contained in the
private field of the first tail page. On 32-bit, _private_1 aligns with
page[1].private.

Link: https://lkml.kernel.org/r/20220922154207.1575343-3-sidhartha.kumar@oracle.com
Signed-off-by: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Acked-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Colin Cross <ccross@google.com>
Cc: David Howells <dhowells@redhat.com>
Cc: "Eric W . Biederman" <ebiederm@xmission.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: kernel test robot <lkp@intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: William Kucharski <william.kucharski@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

kmsan: add KMSAN runtime core

For each memory location KernelMemorySanitizer maintains two types of
metadata:

1. The so-called shadow of that location - а byte:byte mapping describing
whether or not individual bits of memory are initialized (shadow is 0)
or not (shadow is 1).
2. The origins of that location - а 4-byte:4-byte mapping containing
4-byte IDs of the stack traces where uninitialized values were
created.

Each struct page now contains pointers to two struct pages holding KMSAN
metadata (shadow and origins) for the original struct page. Utility
routines in mm/kmsan/core.c and mm/kmsan/shadow.c handle the metadata
creation, addressing, copying and checking. mm/kmsan/report.c performs
error reporting in the cases an uninitialized value is used in a way that
leads to undefined behavior.

KMSAN compiler instrumentation is responsible for tracking the metadata
along with the kernel memory. mm/kmsan/instrumentation.c provides the
implementation for instrumentation hooks that are called from files
compiled with -fsanitize=kernel-memory.

To aid parameter passing (also done at instrumentation level), each
task_struct now contains a struct kmsan_task_state used to track the
metadata of function parameters and return values for that task.

Finally, this patch provides CONFIG_KMSAN that enables KMSAN, and declares
CFLAGS_KMSAN, which are applied to files compiled with KMSAN. The
KMSAN_SANITIZE:=n Makefile directive can be used to completely disable
KMSAN instrumentation for certain files.

Similarly, KMSAN_ENABLE_CHECKS:=n disables KMSAN checks and makes newly
created stack memory initialized.

Users can also use functions from include/linux/kmsan-checks.h to mark
certain memory regions as uninitialized or initialized (this is called
"poisoning" and "unpoisoning") or check that a particular region is
initialized.

Link: https://lkml.kernel.org/r/20220915150417.722975-12-glider@google.com
Signed-off-by: Alexander Potapenko <glider@google.com>
Acked-by: Marco Elver <elver@google.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Andrey Konovalov <andreyknvl@google.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Eric Biggers <ebiggers@google.com>
Cc: Eric Biggers <ebiggers@kernel.org>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Ilya Leoshkevich <iii@linux.ibm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Vegard Nossum <vegard.nossum@oracle.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: add the first tail page to struct folio

Some of the static checkers get confused by extracting the page from the
folio and referring to fields in the first tail page. Adding these fields
to struct folio lets us avoid doing that. It has the risk that people
will refer to those fields without checking that the folio is actually a
large folio, so prefix them with underscores and document the preferred
function to use instead.

Link: https://lkml.kernel.org/r/20220902194653.1739778-3-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

ksm: count allocated ksm rmap_items for each process

Patch series "ksm: count allocated rmap_items and update documentation",
v5.

KSM can save memory by merging identical pages, but also can consume
additional memory, because it needs to generate rmap_items to save each
scanned page's brief rmap information.

To determine how beneficial the ksm-policy (like madvise), they are using
brings, so we add a new interface /proc/<pid>/ksm_stat for each process
The value "ksm_rmap_items" in it indicates the total allocated ksm
rmap_items of this process.

The detailed description can be seen in the following patches' commit
message.


This patch (of 2):

KSM can save memory by merging identical pages, but also can consume
additional memory, because it needs to generate rmap_items to save each
scanned page's brief rmap information. Some of these pages may be merged,
but some may not be abled to be merged after being checked several times,
which are unprofitable memory consumed.

The information about whether KSM save memory or consume memory in
system-wide range can be determined by the comprehensive calculation of
pages_sharing, pages_shared, pages_unshared and pages_volatile. A simple
approximate calculation:

profit =~ pages_sharing * sizeof(page) - (all_rmap_items) *
sizeof(rmap_item);

where all_rmap_items equals to the sum of pages_sharing, pages_shared,
pages_unshared and pages_volatile.

But we cannot calculate this kind of ksm profit inner single-process wide
because the information of ksm rmap_item's number of a process is lacked.
For user applications, if this kind of information could be obtained, it
helps upper users know how beneficial the ksm-policy (like madvise) they
are using brings, and then optimize their app code. For example, one
application madvise 1000 pages as MERGEABLE, while only a few pages are
really merged, then it's not cost-efficient.

So we add a new interface /proc/<pid>/ksm_stat for each process in which
the value of ksm_rmap_itmes is only shown now and so more values can be
added in future.

So similarly, we can calculate the ksm profit approximately for a single
process by:

profit =~ ksm_merging_pages * sizeof(page) - ksm_rmap_items *
sizeof(rmap_item);

where ksm_merging_pages is shown at /proc/<pid>/ksm_merging_pages, and
ksm_rmap_items is shown in /proc/<pid>/ksm_stat.

Link: https://lkml.kernel.org/r/20220830143731.299702-1-xu.xin16@zte.com.cn
Link: https://lkml.kernel.org/r/20220830143838.299758-1-xu.xin16@zte.com.cn
Signed-off-by: xu xin <xu.xin16@zte.com.cn>
Reviewed-by: Xiaokai Ran <ran.xiaokai@zte.com.cn>
Reviewed-by: Yang Yang <yang.yang29@zte.com.cn>
Signed-off-by: CGEL ZTE <cgel.zte@gmail.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Bagas Sanjaya <bagasdotme@gmail.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Izik Eidus <izik.eidus@ravellosystems.com>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: fixup documentation regarding pte_numa() and PROT_NUMA

pte_numa() no longer exists -- replaced by pte_protnone() -- and PROT_NUMA
probably never existed: MM_CP_PROT_NUMA also ends up using PROT_NONE.

Let's fixup the doc.

Link: https://lkml.kernel.org/r/20220825164659.89824-4-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Peter Xu <peterx@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: remove the vma linked list

Replace any vm_next use with vma_find().

Update free_pgtables(), unmap_vmas(), and zap_page_range() to use the
maple tree.

Use the new free_pgtables() and unmap_vmas() in do_mas_align_munmap(). At
the same time, alter the loop to be more compact.

Now that free_pgtables() and unmap_vmas() take a maple tree as an
argument, rearrange do_mas_align_munmap() to use the new tree to hold the
vmas to remove.

Remove __vma_link_list() and __vma_unlink_list() as they are exclusively
used to update the linked list.

Drop linked list update from __insert_vm_struct().

Rework validation of tree as it was depending on the linked list.

[yang.lee@linux.alibaba.com: fix one kernel-doc comment]
Link: https://bugzilla.openanolis.cn/show_bug.cgi?id=1949
Link: https://lkml.kernel.org/r/20220824021918.94116-1-yang.lee@linux.alibaba.comLink: https://lkml.kernel.org/r/20220906194824.2110408-69-Liam.Howlett@oracle.com
Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
Tested-by: Yu Zhao <yuzhao@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc: SeongJae Park <sj@kernel.org>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: remove vmacache

By using the maple tree and the maple tree state, the vmacache is no
longer beneficial and is complicating the VMA code. Remove the vmacache
to reduce the work in keeping it up to date and code complexity.

Link: https://lkml.kernel.org/r/20220906194824.2110408-26-Liam.Howlett@oracle.com
Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Tested-by: Yu Zhao <yuzhao@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc: SeongJae Park <sj@kernel.org>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: remove rb tree.

Remove the RB tree and start using the maple tree for vm_area_struct
tracking.

Drop validate_mm() calls in expand_upwards() and expand_downwards() as the
lock is not held.

Link: https://lkml.kernel.org/r/20220906194824.2110408-18-Liam.Howlett@oracle.com
Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
Tested-by: Yu Zhao <yuzhao@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc: SeongJae Park <sj@kernel.org>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: add VMA iterator

This thin layer of abstraction over the maple tree state is for iterating
over VMAs. You can go forwards, go backwards or ask where the iterator
is. Rename the existing vma_next() to __vma_next() -- it will be removed
by the end of this series.

Link: https://lkml.kernel.org/r/20220906194824.2110408-10-Liam.Howlett@oracle.com
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Davidlohr Bueso <dave@stgolabs.net>
Tested-by: Yu Zhao <yuzhao@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: David Howells <dhowells@redhat.com>
Cc: SeongJae Park <sj@kernel.org>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: start tracking VMAs with maple tree

Start tracking the VMAs with the new maple tree structure in parallel with
the rb_tree. Add debug and trace events for maple tree operations and
duplicate the rb_tree that is created on forks into the maple tree.

The maple tree is added to the mm_struct including the mm_init struct,
added support in required mm/mmap functions, added tracking in kernel/fork
for process forking, and used to find the unmapped_area and checked
against what the rbtree finds.

This also moves the mmap_lock() in exit_mmap() since the oom reaper call
does walk the VMAs. Otherwise lockdep will be unhappy if oom happens.

When splitting a vma fails due to allocations of the maple tree nodes,
the error path in __split_vma() calls new->vm_ops->close(new). The page
accounting for hugetlb is actually in the close() operation, so it
accounts for the removal of 1/2 of the VMA which was not adjusted. This
results in a negative exit value. To avoid the negative charge, set
vm_start = vm_end and vm_pgoff = 0.

There is also a potential accounting issue in special mappings from
insert_vm_struct() failing to allocate, so reverse the charge there in
the failure scenario.

Link: https://lkml.kernel.org/r/20220906194824.2110408-9-Liam.Howlett@oracle.com
Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Tested-by: Yu Zhao <yuzhao@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: SeongJae Park <sj@kernel.org>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: multi-gen LRU: support page table walks

To further exploit spatial locality, the aging prefers to walk page tables
to search for young PTEs and promote hot pages. A kill switch will be
added in the next patch to disable this behavior. When disabled, the
aging relies on the rmap only.

NB: this behavior has nothing similar with the page table scanning in the
2.4 kernel [1], which searches page tables for old PTEs, adds cold pages
to swapcache and unmaps them.

To avoid confusion, the term "iteration" specifically means the traversal
of an entire mm_struct list; the term "walk" will be applied to page
tables and the rmap, as usual.

An mm_struct list is maintained for each memcg, and an mm_struct follows
its owner task to the new memcg when this task is migrated. Given an
lruvec, the aging iterates lruvec_memcg()->mm_list and calls
walk_page_range() with each mm_struct on this list to promote hot pages
before it increments max_seq.

When multiple page table walkers iterate the same list, each of them gets
a unique mm_struct; therefore they can run concurrently. Page table
walkers ignore any misplaced pages, e.g., if an mm_struct was migrated,
pages it left in the previous memcg will not be promoted when its current
memcg is under reclaim. Similarly, page table walkers will not promote
pages from nodes other than the one under reclaim.

This patch uses the following optimizations when walking page tables:
1. It tracks the usage of mm_struct's between context switches so that
page table walkers can skip processes that have been sleeping since
the last iteration.
2. It uses generational Bloom filters to record populated branches so
that page table walkers can reduce their search space based on the
query results, e.g., to skip page tables containing mostly holes or
misplaced pages.
3. It takes advantage of the accessed bit in non-leaf PMD entries when
CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG=y.
4. It does not zigzag between a PGD table and the same PMD table
spanning multiple VMAs. IOW, it finishes all the VMAs within the
range of the same PMD table before it returns to a PGD table. This
improves the cache performance for workloads that have large
numbers of tiny VMAs [2], especially when CONFIG_PGTABLE_LEVELS=5.

Server benchmark results:
Single workload:
fio (buffered I/O): no change

Single workload:
memcached (anon): +[8, 10]%
Ops/sec KB/sec
patch1-7: 1147696.57 44640.29
patch1-8: 1245274.91 48435.66

Configurations:
no change

Client benchmark results:
kswapd profiles:
patch1-7
48.16% lzo1x_1_do_compress (real work)
8.20% page_vma_mapped_walk (overhead)
7.06% _raw_spin_unlock_irq
2.92% ptep_clear_flush
2.53% __zram_bvec_write
2.11% do_raw_spin_lock
2.02% memmove
1.93% lru_gen_look_around
1.56% free_unref_page_list
1.40% memset

patch1-8
49.44% lzo1x_1_do_compress (real work)
6.19% page_vma_mapped_walk (overhead)
5.97% _raw_spin_unlock_irq
3.13% get_pfn_folio
2.85% ptep_clear_flush
2.42% __zram_bvec_write
2.08% do_raw_spin_lock
1.92% memmove
1.44% alloc_zspage
1.36% memset

Configurations:
no change

Thanks to the following developers for their efforts [3].
kernel test robot <lkp@intel.com>

[1] https://lwn.net/Articles/23732/
[2] https://llvm.org/docs/ScudoHardenedAllocator.html
[3] https://lore.kernel.org/r/202204160827.ekEARWQo-lkp@intel.com/

Link: https://lkml.kernel.org/r/20220918080010.2920238-9-yuzhao@google.com
Signed-off-by: Yu Zhao <yuzhao@google.com>
Acked-by: Brian Geffon <bgeffon@google.com>
Acked-by: Jan Alexander Steffens (heftig) <heftig@archlinux.org>
Acked-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Acked-by: Steven Barrett <steven@liquorix.net>
Acked-by: Suleiman Souhlal <suleiman@google.com>
Tested-by: Daniel Byrne <djbyrne@mtu.edu>
Tested-by: Donald Carr <d@chaos-reins.com>
Tested-by: Holger Hoffstätte <holger@applied-asynchrony.com>
Tested-by: Konstantin Kharlamov <Hi-Angel@yandex.ru>
Tested-by: Shuang Zhai <szhai2@cs.rochester.edu>
Tested-by: Sofia Trinh <sofia.trinh@edi.works>
Tested-by: Vaibhav Jain <vaibhav@linux.ibm.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Hillf Danton <hdanton@sina.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Michael Larabel <Michael@MichaelLarabel.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Mike Rapoport <rppt@linux.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Qi Zheng <zhengqi.arch@bytedance.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/page_alloc: add page->buddy_list and page->pcp_list

Patch series "Drain remote per-cpu directly", v5.

Some setups, notably NOHZ_FULL CPUs, may be running realtime or
latency-sensitive applications that cannot tolerate interference due to
per-cpu drain work queued by __drain_all_pages(). Introduce a new
mechanism to remotely drain the per-cpu lists. It is made possible by
remotely locking 'struct per_cpu_pages' new per-cpu spinlocks. This has
two advantages, the time to drain is more predictable and other unrelated
tasks are not interrupted.

This series has the same intent as Nicolas' series "mm/page_alloc: Remote
per-cpu lists drain support" -- avoid interference of a high priority task
due to a workqueue item draining per-cpu page lists. While many workloads
can tolerate a brief interruption, it may cause a real-time task running
on a NOHZ_FULL CPU to miss a deadline and at minimum, the draining is
non-deterministic.

Currently an IRQ-safe local_lock protects the page allocator per-cpu
lists. The local_lock on its own prevents migration and the IRQ disabling
protects from corruption due to an interrupt arriving while a page
allocation is in progress.

This series adjusts the locking. A spinlock is added to struct
per_cpu_pages to protect the list contents while local_lock_irq is
ultimately replaced by just the spinlock in the final patch. This allows
a remote CPU to safely. Follow-on work should allow the spin_lock_irqsave
to be converted to spin_lock to avoid IRQs being disabled/enabled in most
cases. The follow-on patch will be one kernel release later as it is
relatively high risk and it'll make bisections more clear if there are any
problems.

Patch 1 is a cosmetic patch to clarify when page->lru is storing buddy pages
and when it is storing per-cpu pages.

Patch 2 shrinks per_cpu_pages to make room for a spin lock. Strictly speaking
this is not necessary but it avoids per_cpu_pages consuming another
cache line.

Patch 3 is a preparation patch to avoid code duplication.

Patch 4 is a minor correction.

Patch 5 uses a spin_lock to protect the per_cpu_pages contents while still
relying on local_lock to prevent migration, stabilise the pcp
lookup and prevent IRQ reentrancy.

Patch 6 remote drains per-cpu pages directly instead of using a workqueue.

Patch 7 uses a normal spinlock instead of local_lock for remote draining


This patch (of 7):

The page allocator uses page->lru for storing pages on either buddy or PCP
lists. Create page->buddy_list and page->pcp_list as a union with
page->lru. This is simply to clarify what type of list a page is on in
the page allocator.

No functional change intended.

[minchan@kernel.org: fix page lru fields in macros]
Link: https://lkml.kernel.org/r/20220624125423.6126-2-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Tested-by: Minchan Kim <minchan@kernel.org>
Acked-by: Minchan Kim <minchan@kernel.org>
Reviewed-by: Nicolas Saenz Julienne <nsaenzju@redhat.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Tested-by: Yu Zhao <yuzhao@google.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: avoid unnecessary page fault retires on shared memory types

I observed that for each of the shared file-backed page faults, we're very
likely to retry one more time for the 1st write fault upon no page. It's
because we'll need to release the mmap lock for dirty rate limit purpose
with balance_dirty_pages_ratelimited() (in fault_dirty_shared_page()).

Then after that throttling we return VM_FAULT_RETRY.

We did that probably because VM_FAULT_RETRY is the only way we can return
to the fault handler at that time telling it we've released the mmap lock.

However that's not ideal because it's very likely the fault does not need
to be retried at all since the pgtable was well installed before the
throttling, so the next continuous fault (including taking mmap read lock,
walk the pgtable, etc.) could be in most cases unnecessary.

It's not only slowing down page faults for shared file-backed, but also add
more mmap lock contention which is in most cases not needed at all.

To observe this, one could try to write to some shmem page and look at
"pgfault" value in /proc/vmstat, then we should expect 2 counts for each
shmem write simply because we retried, and vm event "pgfault" will capture
that.

To make it more efficient, add a new VM_FAULT_COMPLETED return code just to
show that we've completed the whole fault and released the lock. It's also
a hint that we should very possibly not need another fault immediately on
this page because we've just completed it.

This patch provides a ~12% perf boost on my aarch64 test VM with a simple
program sequentially dirtying 400MB shmem file being mmap()ed and these are
the time it needs:

Before: 650.980 ms (+-1.94%)
After: 569.396 ms (+-1.38%)

I believe it could help more than that.

We need some special care on GUP and the s390 pgfault handler (for gmap
code before returning from pgfault), the rest changes in the page fault
handlers should be relatively straightforward.

Another thing to mention is that mm_account_fault() does take this new
fault as a generic fault to be accounted, unlike VM_FAULT_RETRY.

I explicitly didn't touch hmm_vma_fault() and break_ksm() because they do
not handle VM_FAULT_RETRY even with existing code, so I'm literally keeping
them as-is.

Link: https://lkml.kernel.org/r/20220530183450.42886-1-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Vineet Gupta <vgupta@kernel.org>
Acked-by: Guo Ren <guoren@kernel.org>
Acked-by: Max Filippov <jcmvbkbc@gmail.com>
Acked-by: Christian Borntraeger <borntraeger@linux.ibm.com>
Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Alistair Popple <apopple@nvidia.com>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk> [arm part]
Acked-by: Heiko Carstens <hca@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Stafford Horne <shorne@gmail.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Johannes Berg <johannes@sipsolutions.net>
Cc: Brian Cain <bcain@quicinc.com>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Richard Weinberger <richard@nod.at>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Janosch Frank <frankja@linux.ibm.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Anton Ivanov <anton.ivanov@cambridgegreys.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Jonas Bonn <jonas@southpole.se>
Cc: Will Deacon <will@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Michal Simek <monstr@monstr.eu>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Chris Zankel <chris@zankel.net>
Cc: Hugh Dickins <hughd@google.com>
Cc: Dinh Nguyen <dinguyen@kernel.org>
Cc: Rich Felker <dalias@libc.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Helge Deller <deller@gmx.de>
Cc: Yoshinori Sato <ysato@users.osdn.me>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: Add kernel-doc for folio->mlock_count

Fix "./include/linux/mm_types.h:279: warning: Function parameter or member
'mlock_count' not described in 'folio'". Also neaten the html by hiding
the anon struct.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

mm/hugetlb: only drop uffd-wp special pte if required

As with shmem uffd-wp special ptes, only drop the uffd-wp special swap pte
if unmapping an entire vma or synchronized such that faults can not race
with the unmap operation. This requires passing zap_flags all the way to
the lowest level hugetlb unmap routine: __unmap_hugepage_range.

In general, unmap calls originated in hugetlbfs code will pass the
ZAP_FLAG_DROP_MARKER flag as synchronization is in place to prevent
faults. The exception is hole punch which will first unmap without any
synchronization. Later when hole punch actually removes the page from the
file, it will check to see if there was a subsequent fault and if so take
the hugetlb fault mutex while unmapping again. This second unmap will
pass in ZAP_FLAG_DROP_MARKER.

The justification of "whether to apply ZAP_FLAG_DROP_MARKER flag when
unmap a hugetlb range" is (IMHO): we should never reach a state when a
page fault could errornously fault in a page-cache page that was
wr-protected to be writable, even in an extremely short period. That
could happen if e.g. we pass ZAP_FLAG_DROP_MARKER when
hugetlbfs_punch_hole() calls hugetlb_vmdelete_list(), because if a page
faults after that call and before remove_inode_hugepages() is executed,
the page cache can be mapped writable again in the small racy window, that
can cause unexpected data overwritten.

[peterx@redhat.com: fix sparse warning]
Link: https://lkml.kernel.org/r/Ylcdw8I1L5iAoWhb@xz-m1.local
[akpm@linux-foundation.org: move zap_flags_t from mm.h to mm_types.h to fix build issues]
Link: https://lkml.kernel.org/r/20220405014915.14873-1-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: "Kirill A . Shutemov" <kirill@shutemov.name>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Nadav Amit <nadav.amit@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: check against orig_pte for finish_fault()

This patch allows do_fault() to trigger on !pte_none() cases too. This
prepares for the pte markers to be handled by do_fault() just like none
pte.

To achieve this, instead of unconditionally check against pte_none() in
finish_fault(), we may hit the case that the orig_pte was some pte marker
so what we want to do is to replace the pte marker with some valid pte
entry. Then if orig_pte was set we'd want to check the current *pte
(under pgtable lock) against orig_pte rather than none pte.

Right now there's no solid way to safely reference orig_pte because when
pmd is not allocated handle_pte_fault() will not initialize orig_pte, so
it's not safe to reference it.

There's another solution proposed before this patch to do pte_clear() for
vmf->orig_pte for pmd==NULL case, however it turns out it'll break arm32
because arm32 could have assumption that pte_t* pointer will always reside
on a real ram32 pgtable, not any kernel stack variable.

To solve this, we add a new flag FAULT_FLAG_ORIG_PTE_VALID, and it'll be
set along with orig_pte when there is valid orig_pte, or it'll be cleared
when orig_pte was not initialized.

It'll be updated every time we call handle_pte_fault(), so e.g. if a page
fault retry happened it'll be properly updated along with orig_pte.

[1] https://lore.kernel.org/lkml/710c48c9-406d-e4c5-a394-10501b951316@samsung.com/

[akpm@linux-foundation.org: coding-style cleanups]
[peterx@redhat.com: fix crash reported by Marek]
Link: https://lkml.kernel.org/r/Ylb9rXJyPm8/ao8f@xz-m1.local
Link: https://lkml.kernel.org/r/20220405014836.14077-1-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Alistair Popple <apopple@nvidia.com>
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: "Kirill A . Shutemov" <kirill@shutemov.name>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Nadav Amit <nadav.amit@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: support GUP-triggered unsharing of anonymous pages

Whenever GUP currently ends up taking a R/O pin on an anonymous page that
might be shared -- mapped R/O and !PageAnonExclusive() -- any write fault
on the page table entry will end up replacing the mapped anonymous page
due to COW, resulting in the GUP pin no longer being consistent with the
page actually mapped into the page table.

The possible ways to deal with this situation are:
(1) Ignore and pin -- what we do right now.
(2) Fail to pin -- which would be rather surprising to callers and
could break user space.
(3) Trigger unsharing and pin the now exclusive page -- reliable R/O
pins.

We want to implement 3) because it provides the clearest semantics and
allows for checking in unpin_user_pages() and friends for possible BUGs:
when trying to unpin a page that's no longer exclusive, clearly something
went very wrong and might result in memory corruptions that might be hard
to debug. So we better have a nice way to spot such issues.

To implement 3), we need a way for GUP to trigger unsharing:
FAULT_FLAG_UNSHARE. FAULT_FLAG_UNSHARE is only applicable to R/O mapped
anonymous pages and resembles COW logic during a write fault. However, in
contrast to a write fault, GUP-triggered unsharing will, for example,
still maintain the write protection.

Let's implement FAULT_FLAG_UNSHARE by hooking into the existing write
fault handlers for all applicable anonymous page types: ordinary pages,
THP and hugetlb.

* If FAULT_FLAG_UNSHARE finds a R/O-mapped anonymous page that has been
marked exclusive in the meantime by someone else, there is nothing to do.
* If FAULT_FLAG_UNSHARE finds a R/O-mapped anonymous page that's not
marked exclusive, it will try detecting if the process is the exclusive
owner. If exclusive, it can be set exclusive similar to reuse logic
during write faults via page_move_anon_rmap() and there is nothing
else to do; otherwise, we either have to copy and map a fresh,
anonymous exclusive page R/O (ordinary pages, hugetlb), or split the
THP.

This commit is heavily based on patches by Andrea.

Link: https://lkml.kernel.org/r/20220428083441.37290-16-david@redhat.com
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Co-developed-by: Andrea Arcangeli <aarcange@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Rientjes <rientjes@google.com>
Cc: Don Dutile <ddutile@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jann Horn <jannh@google.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Khalid Aziz <khalid.aziz@oracle.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Liang Zhang <zhangliang5@huawei.com>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mike Rapoport <rppt@linux.ibm.com>
Cc: Nadav Amit <namit@vmware.com>
Cc: Oded Gabbay <oded.gabbay@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Pedro Demarchi Gomes <pedrodemargomes@gmail.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Roman Gushchin <guro@fb.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Yang Shi <shy828301@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

ksm: count ksm merging pages for each process

Some applications or containers want to use KSM by calling madvise() to
advise areas of address space to be MERGEABLE. But they may not know
which applications are more likely to cause real merges in the
deployment. If this patch is applied, it helps them know their
corresponding number of merged pages, and then optimize their app code.

As current KSM only counts the number of KSM merging pages(e.g.
ksm_pages_sharing and ksm_pages_shared) of the whole system, we cannot see
the more fine-grained KSM merging, for the upper application optimization,
the merging area cannot be set easily according to the KSM page merging
probability of each process. Therefore, it is necessary to add extra
statistical means so that the upper level users can know the detailed KSM
merging information of each process.

We add a new proc file named as ksm_merging_pages under /proc/<pid>/ to
indicate the involved ksm merging pages of this process.

[akpm@linux-foundation.org: fix comment typo, remove BUG_ON()s]
Link: https://lkml.kernel.org/r/20220325082318.2352853-1-xu.xin16@zte.com.cn
Signed-off-by: xu xin <xu.xin16@zte.com.cn>
Reported-by: kernel test robot <lkp@intel.com>
Reviewed-by: Yang Yang <yang.yang29@zte.com.cn>
Reviewed-by: Ran Xiaokai <ran.xiaokai@zte.com.cn>
Reported-by: Zeal Robot <zealci@zte.com.cn>
Cc: Kees Cook <keescook@chromium.org>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Ohhoon Kwon <ohoono.kwon@samsung.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Stephen Brennan <stephen.s.brennan@oracle.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Feng Tang <feng.tang@intel.com>
Cc: Yang Yang <yang.yang29@zte.com.cn>
Cc: Ran Xiaokai <ran.xiaokai@zte.com.cn>
Cc: Zeal Robot <zealci@zte.com.cn>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: Make compound_pincount always available

Move compound_pincount from the third page to the second page, which
means it's available for all compound pages. That lets us delete
hpage_pincount_available().

On 32-bit systems, there isn't enough space for both compound_pincount
and compound_nr in the second page (it would collide with page->private,
which is in use for pages in the swap cache), so revert the optimisation
of storing both compound_order and compound_nr on 32-bit systems.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: William Kucharski <william.kucharski@oracle.com>

mm/munlock: maintain page->mlock_count while unevictable

Previous patches have been preparatory: now implement page->mlock_count.
The ordering of the "Unevictable LRU" is of no significance, and there is
no point holding unevictable pages on a list: place page->mlock_count to
overlay page->lru.prev (since page->lru.next is overlaid by compound_head,
which needs to be even so as not to satisfy PageTail - though 2 could be
added instead of 1 for each mlock, if that's ever an improvement).

But it's only safe to rely on or modify page->mlock_count while lruvec
lock is held and page is on unevictable "LRU" - we can save lots of edits
by continuing to pretend that there's an imaginary LRU here (there is an
unevictable count which still needs to be maintained, but not a list).

The mlock_count technique suffers from an unreliability much like with
page_mlock(): while someone else has the page off LRU, not much can
be done. As before, err on the safe side (behave as if mlock_count 0),
and let try_to_unlock_one() move the page to unevictable if reclaim finds
out later on - a few misplaced pages don't matter, what we want to avoid
is imbalancing reclaim by flooding evictable lists with unevictable pages.

I am not a fan of "if (!isolate_lru_page(page)) putback_lru_page(page);":
if we have taken lruvec lock to get the page off its present list, then
we save everyone trouble (and however many extra atomic ops) by putting
it on its destination list immediately.

Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

mm: Change CONFIG option for mm->pasid field

This currently depends on CONFIG_IOMMU_SUPPORT. But it is only
needed when CONFIG_IOMMU_SVA option is enabled.

Change the CONFIG guards around definition and initialization
of mm->pasid field.

Suggested-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Link: https://lore.kernel.org/r/20220207230254.3342514-3-fenghua.yu@intel.com

mm: refactor vm_area_struct::anon_vma_name usage code

Avoid mixing strings and their anon_vma_name referenced pointers by
using struct anon_vma_name whenever possible. This simplifies the code
and allows easier sharing of anon_vma_name structures when they
represent the same name.

[surenb@google.com: fix comment]

Link: https://lkml.kernel.org/r/20220223153613.835563-1-surenb@google.com
Link: https://lkml.kernel.org/r/20220224231834.1481408-1-surenb@google.com
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Suggested-by: Matthew Wilcox <willy@infradead.org>
Suggested-by: Michal Hocko <mhocko@suse.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Colin Cross <ccross@google.com>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Alexey Gladkov <legion@kernel.org>
Cc: Sasha Levin <sashal@kernel.org>
Cc: Chris Hyser <chris.hyser@oracle.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Peter Collingbourne <pcc@google.com>
Cc: Xiaofeng Cao <caoxiaofeng@yulong.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Cyrill Gorcunov <gorcunov@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: page->mapping folio->mapping should have the same offset

As with the other members of folio, the offset of page->mapping and
folio->mapping must be the same. The compile-time check was
inadvertently removed during development. Add it back.

[willy@infradead.org: changelog redo]

Link: https://lkml.kernel.org/r/20220104011734.21714-1-richard.weiyang@gmail.com
Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: Remove slab from struct page

All members of struct slab can now be removed from struct page.
This shrinks the definition of struct page by 30 LOC, making
it easier to understand.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>

mm/rmap: fix potential batched TLB flush race

In theory, the following race is possible for batched TLB flushing.

CPU0 CPU1
---- ----
shrink_page_list()
unmap
zap_pte_range()
flush_tlb_batched_pending()
flush_tlb_mm()
try_to_unmap()
set_tlb_ubc_flush_pending()
mm->tlb_flush_batched = true
mm->tlb_flush_batched = false

After the TLB is flushed on CPU1 via flush_tlb_mm() and before
mm->tlb_flush_batched is set to false, some PTE is unmapped on CPU0 and
the TLB flushing is pended. Then the pended TLB flushing will be lost.
Although both set_tlb_ubc_flush_pending() and
flush_tlb_batched_pending() are called with PTL locked, different PTL
instances may be used.

Because the race window is really small, and the lost TLB flushing will
cause problem only if a TLB entry is inserted before the unmapping in
the race window, the race is only theoretical. But the fix is simple
and cheap too.

Syzbot has reported this too as follows:

==================================================================
BUG: KCSAN: data-race in flush_tlb_batched_pending / try_to_unmap_one

write to 0xffff8881072cfbbc of 1 bytes by task 17406 on cpu 1:
flush_tlb_batched_pending+0x5f/0x80 mm/rmap.c:691
madvise_free_pte_range+0xee/0x7d0 mm/madvise.c:594
walk_pmd_range mm/pagewalk.c:128 [inline]
walk_pud_range mm/pagewalk.c:205 [inline]
walk_p4d_range mm/pagewalk.c:240 [inline]
walk_pgd_range mm/pagewalk.c:277 [inline]
__walk_page_range+0x981/0x1160 mm/pagewalk.c:379
walk_page_range+0x131/0x300 mm/pagewalk.c:475
madvise_free_single_vma mm/madvise.c:734 [inline]
madvise_dontneed_free mm/madvise.c:822 [inline]
madvise_vma mm/madvise.c:996 [inline]
do_madvise+0xe4a/0x1140 mm/madvise.c:1202
__do_sys_madvise mm/madvise.c:1228 [inline]
__se_sys_madvise mm/madvise.c:1226 [inline]
__x64_sys_madvise+0x5d/0x70 mm/madvise.c:1226
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae

write to 0xffff8881072cfbbc of 1 bytes by task 71 on cpu 0:
set_tlb_ubc_flush_pending mm/rmap.c:636 [inline]
try_to_unmap_one+0x60e/0x1220 mm/rmap.c:1515
rmap_walk_anon+0x2fb/0x470 mm/rmap.c:2301
try_to_unmap+0xec/0x110
shrink_page_list+0xe91/0x2620 mm/vmscan.c:1719
shrink_inactive_list+0x3fb/0x730 mm/vmscan.c:2394
shrink_list mm/vmscan.c:2621 [inline]
shrink_lruvec+0x3c9/0x710 mm/vmscan.c:2940
shrink_node_memcgs+0x23e/0x410 mm/vmscan.c:3129
shrink_node+0x8f6/0x1190 mm/vmscan.c:3252
kswapd_shrink_node mm/vmscan.c:4022 [inline]
balance_pgdat+0x702/0xd30 mm/vmscan.c:4213
kswapd+0x200/0x340 mm/vmscan.c:4473
kthread+0x2c7/0x2e0 kernel/kthread.c:327
ret_from_fork+0x1f/0x30

value changed: 0x01 -> 0x00

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 71 Comm: kswapd0 Not tainted 5.16.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================

[akpm@linux-foundation.org: tweak comments]

Link: https://lkml.kernel.org/r/20211201021104.126469-1-ying.huang@intel.com
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Reported-by: syzbot+aa5bebed695edaccf0df@syzkaller.appspotmail.com
Cc: Nadav Amit <namit@vmware.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Will Deacon <will@kernel.org>
Cc: Yu Zhao <yuzhao@google.com>
Cc: Marco Elver <elver@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: move tlb_flush_pending inline helpers to mm_inline.h

linux/mm_types.h should only define structure definitions, to make it
cheap to include elsewhere. The atomic_t helper function definitions
are particularly large, so it's better to move the helpers using those
into the existing linux/mm_inline.h and only include that where needed.

As a follow-up, we may want to go through all the indirect includes in
mm_types.h and reduce them as much as possible.

Link: https://lkml.kernel.org/r/20211207125710.2503446-2-arnd@kernel.org
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Colin Cross <ccross@google.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Peter Xu <peterx@redhat.com>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Yu Zhao <yuzhao@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Eric Biederman <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: move anon_vma declarations to linux/mm_inline.h

The patch to add anonymous vma names causes a build failure in some
configurations:

include/linux/mm_types.h: In function 'is_same_vma_anon_name':
include/linux/mm_types.h:924:37: error: implicit declaration of function 'strcmp' [-Werror=implicit-function-declaration]
924 | return name && vma_name && !strcmp(name, vma_name);
| ^~~~~~
include/linux/mm_types.h:22:1: note: 'strcmp' is defined in header '<string.h>'; did you forget to '#include <string.h>'?

This should not really be part of linux/mm_types.h in the first place,
as that header is meant to only contain structure defintions and need a
minimum set of indirect includes itself.

While the header clearly includes more than it should at this point,
let's not make it worse by including string.h as well, which would pull
in the expensive (compile-speed wise) fortify-string logic.

Move the new functions into a separate header that only needs to be
included in a couple of locations.

Link: https://lkml.kernel.org/r/20211207125710.2503446-1-arnd@kernel.org
Fixes: "mm: add a field to store names for private anonymous memory"
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Colin Cross <ccross@google.com>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Peter Xu <peterx@redhat.com>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Yu Zhao <yuzhao@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: add anonymous vma name refcounting

While forking a process with high number (64K) of named anonymous vmas
the overhead caused by strdup() is noticeable. Experiments with ARM64
Android device show up to 40% performance regression when forking a
process with 64k unpopulated anonymous vmas using the max name lengths
vs the same process with the same number of anonymous vmas having no
name.

Introduce anon_vma_name refcounted structure to avoid the overhead of
copying vma names during fork() and when splitting named anonymous vmas.

When a vma is duplicated, instead of copying the name we increment the
refcount of this structure. Multiple vmas can point to the same
anon_vma_name as long as they increment the refcount. The name member
of anon_vma_name structure is assigned at structure allocation time and
is never changed. If vma name changes then the refcount of the original
structure is dropped, a new anon_vma_name structure is allocated to hold
the new name and the vma pointer is updated to point to the new
structure.

With this approach the fork() performance regressions is reduced 3-4x
times and with usecases using more reasonable number of VMAs (a few
thousand) the regressions is not measurable.

Link: https://lkml.kernel.org/r/20211019215511.3771969-3-surenb@google.com
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Colin Cross <ccross@google.com>
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: David Rientjes <rientjes@google.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jan Glauber <jan.glauber@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rob Landley <rob@landley.net>
Cc: "Serge E. Hallyn" <serge.hallyn@ubuntu.com>
Cc: Shaohua Li <shli@fusionio.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: add a field to store names for private anonymous memory

In many userspace applications, and especially in VM based applications
like Android uses heavily, there are multiple different allocators in
use. At a minimum there is libc malloc and the stack, and in many cases
there are libc malloc, the stack, direct syscalls to mmap anonymous
memory, and multiple VM heaps (one for small objects, one for big
objects, etc.). Each of these layers usually has its own tools to
inspect its usage; malloc by compiling a debug version, the VM through
heap inspection tools, and for direct syscalls there is usually no way
to track them.

On Android we heavily use a set of tools that use an extended version of
the logic covered in Documentation/vm/pagemap.txt to walk all pages
mapped in userspace and slice their usage by process, shared (COW) vs.
unique mappings, backing, etc. This can account for real physical
memory usage even in cases like fork without exec (which Android uses
heavily to share as many private COW pages as possible between
processes), Kernel SamePage Merging, and clean zero pages. It produces
a measurement of the pages that only exist in that process (USS, for
unique), and a measurement of the physical memory usage of that process
with the cost of shared pages being evenly split between processes that
share them (PSS).

If all anonymous memory is indistinguishable then figuring out the real
physical memory usage (PSS) of each heap requires either a pagemap
walking tool that can understand the heap debugging of every layer, or
for every layer's heap debugging tools to implement the pagemap walking
logic, in which case it is hard to get a consistent view of memory
across the whole system.

Tracking the information in userspace leads to all sorts of problems.
It either needs to be stored inside the process, which means every
process has to have an API to export its current heap information upon
request, or it has to be stored externally in a filesystem that somebody
needs to clean up on crashes. It needs to be readable while the process
is still running, so it has to have some sort of synchronization with
every layer of userspace. Efficiently tracking the ranges requires
reimplementing something like the kernel vma trees, and linking to it
from every layer of userspace. It requires more memory, more syscalls,
more runtime cost, and more complexity to separately track regions that
the kernel is already tracking.

This patch adds a field to /proc/pid/maps and /proc/pid/smaps to show a
userspace-provided name for anonymous vmas. The names of named
anonymous vmas are shown in /proc/pid/maps and /proc/pid/smaps as
[anon:<name>].

Userspace can set the name for a region of memory by calling

prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, start, len, (unsigned long)name)

Setting the name to NULL clears it. The name length limit is 80 bytes
including NUL-terminator and is checked to contain only printable ascii
characters (including space), except '[',']','\','$' and '`'.

Ascii strings are being used to have a descriptive identifiers for vmas,
which can be understood by the users reading /proc/pid/maps or
/proc/pid/smaps. Names can be standardized for a given system and they
can include some variable parts such as the name of the allocator or a
library, tid of the thread using it, etc.

The name is stored in a pointer in the shared union in vm_area_struct
that points to a null terminated string. Anonymous vmas with the same
name (equivalent strings) and are otherwise mergeable will be merged.
The name pointers are not shared between vmas even if they contain the
same name. The name pointer is stored in a union with fields that are
only used on file-backed mappings, so it does not increase memory usage.

CONFIG_ANON_VMA_NAME kernel configuration is introduced to enable this
feature. It keeps the feature disabled by default to prevent any
additional memory overhead and to avoid confusing procfs parsers on
systems which are not ready to support named anonymous vmas.

The patch is based on the original patch developed by Colin Cross, more
specifically on its latest version [1] posted upstream by Sumit Semwal.
It used a userspace pointer to store vma names. In that design, name
pointers could be shared between vmas. However during the last
upstreaming attempt, Kees Cook raised concerns [2] about this approach
and suggested to copy the name into kernel memory space, perform
validity checks [3] and store as a string referenced from
vm_area_struct.

One big concern is about fork() performance which would need to strdup
anonymous vma names. Dave Hansen suggested experimenting with
worst-case scenario of forking a process with 64k vmas having longest
possible names [4]. I ran this experiment on an ARM64 Android device
and recorded a worst-case regression of almost 40% when forking such a
process.

This regression is addressed in the followup patch which replaces the
pointer to a name with a refcounted structure that allows sharing the
name pointer between vmas of the same name. Instead of duplicating the
string during fork() or when splitting a vma it increments the refcount.

[1] https://lore.kernel.org/linux-mm/20200901161459.11772-4-sumit.semwal@linaro.org/
[2] https://lore.kernel.org/linux-mm/202009031031.D32EF57ED@keescook/
[3] https://lore.kernel.org/linux-mm/202009031022.3834F692@keescook/
[4] https://lore.kernel.org/linux-mm/5d0358ab-8c47-2f5f-8e43-23b89d6a8e95@intel.com/

Changes for prctl(2) manual page (in the options section):

PR_SET_VMA
Sets an attribute specified in arg2 for virtual memory areas
starting from the address specified in arg3 and spanning the
size specified in arg4. arg5 specifies the value of the attribute
to be set. Note that assigning an attribute to a virtual memory
area might prevent it from being merged with adjacent virtual
memory areas due to the difference in that attribute's value.

Currently, arg2 must be one of:

PR_SET_VMA_ANON_NAME
Set a name for anonymous virtual memory areas. arg5 should
be a pointer to a null-terminated string containing the
name. The name length including null byte cannot exceed
80 bytes. If arg5 is NULL, the name of the appropriate
anonymous virtual memory areas will be reset. The name
can contain only printable ascii characters (including
space), except '[',']','\','$' and '`'.

This feature is available only if the kernel is built with
the CONFIG_ANON_VMA_NAME option enabled.

[surenb@google.com: docs: proc.rst: /proc/PID/maps: fix malformed table]
Link: https://lkml.kernel.org/r/20211123185928.2513763-1-surenb@google.com
[surenb: rebased over v5.15-rc6, replaced userpointer with a kernel copy,
added input sanitization and CONFIG_ANON_VMA_NAME config. The bulk of the
work here was done by Colin Cross, therefore, with his permission, keeping
him as the author]

Link: https://lkml.kernel.org/r/20211019215511.3771969-2-surenb@google.com
Signed-off-by: Colin Cross <ccross@google.com>
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: David Rientjes <rientjes@google.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jan Glauber <jan.glauber@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rob Landley <rob@landley.net>
Cc: "Serge E. Hallyn" <serge.hallyn@ubuntu.com>
Cc: Shaohua Li <shli@fusionio.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: Split slab into its own type

Make struct slab independent of struct page. It still uses the
underlying memory in struct page for storing slab-specific data, but
slab and slub can now be weaned off using struct page directly. Some of
the wrapper functions (slab_address() and slab_order()) still need to
cast to struct folio, but this is a significant disentanglement.

[ vbabka@suse.cz: Rebase on folios, use folio instead of page where
possible.

Do not duplicate flags field in struct slab, instead make the related
accessors go through slab_folio(). For testing pfmemalloc use the
folio_*_active flag accessors directly so the PageSlabPfmemalloc
wrappers can be removed later.

Make folio_slab() expect only folio_test_slab() == true folios and
virt_to_slab() return NULL when folio_test_slab() == false.

Move struct slab to mm/slab.h.

Don't represent with struct slab pages that are not true slab pages,
but just a compound page obtained directly rom page allocator (with
large kmalloc() for SLUB and SLOB). ]

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Roman Gushchin <guro@fb.com>

page_pool: Revert "page_pool: disable dma mapping support..."

This reverts commit d00e60ee54b12de945b8493cf18c1ada9e422514.

As reported by Guillaume in [1]:
Enabling LPAE always enables CONFIG_ARCH_DMA_ADDR_T_64BIT
in 32-bit systems, which breaks the bootup proceess when a
ethernet driver is using page pool with PP_FLAG_DMA_MAP flag.
As we were hoping we had no active consumers for such system
when we removed the dma mapping support, and LPAE seems like
a common feature for 32 bits system, so revert it.

1. https://www.spinics.net/lists/netdev/msg779890.html

Fixes: d00e60ee54b1 ("page_pool: disable dma mapping support for 32-bit arch with 64-bit DMA")
Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com>
Reported-by: "kernelci.org bot" <bot@kernelci.org>
Tested-by: "kernelci.org bot" <bot@kernelci.org>
Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
Acked-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

mm, slub: change percpu partial accounting from objects to pages

With CONFIG_SLUB_CPU_PARTIAL enabled, SLUB keeps a percpu list of
partial slabs that can be promoted to cpu slab when the previous one is
depleted, without accessing the shared partial list. A slab can be
added to this list by 1) refill of an empty list from get_partial_node()
- once we really have to access the shared partial list, we acquire
multiple slabs to amortize the cost of locking, and 2) first free to a
previously full slab - instead of putting the slab on a shared partial
list, we can more cheaply freeze it and put it on the per-cpu list.

To control how large a percpu partial list can grow for a kmem cache,
set_cpu_partial() calculates a target number of free objects on each
cpu's percpu partial list, and this can be also set by the sysfs file
cpu_partial.

However, the tracking of actual number of objects is imprecise, in order
to limit overhead from cpu X freeing an objects to a slab on percpu
partial list of cpu Y. Basically, the percpu partial slabs form a
single linked list, and when we add a new slab to the list with current
head "oldpage", we set in the struct page of the slab we're adding:

page->pages = oldpage->pages + 1; // this is precise
page->pobjects = oldpage->pobjects + (page->objects - page->inuse);
page->next = oldpage;

Thus the real number of free objects in the slab (objects - inuse) is
only determined at the moment of adding the slab to the percpu partial
list, and further freeing doesn't update the pobjects counter nor
propagate it to the current list head. As Jann reports [1], this can
easily lead to large inaccuracies, where the target number of objects
(up to 30 by default) can translate to the same number of (empty) slab
pages on the list. In case 2) above, we put a slab with 1 free object
on the list, thus only increase page->pobjects by 1, even if there are
subsequent frees on the same slab. Jann has noticed this in practice
and so did we [2] when investigating significant increase of kmemcg
usage after switching from SLAB to SLUB.

While this is no longer a problem in kmemcg context thanks to the
accounting rewrite in 5.9, the memory waste is still not ideal and it's
questionable whether it makes sense to perform free object count based
control when object counts can easily become so much inaccurate. So
this patch converts the accounting to be based on number of pages only
(which is precise) and removes the page->pobjects field completely.
This is also ultimately simpler.

To retain the existing set_cpu_partial() heuristic, first calculate the
target number of objects as previously, but then convert it to target
number of pages by assuming the pages will be half-filled on average.
This assumption might obviously also be inaccurate in practice, but
cannot degrade to actual number of pages being equal to the target
number of objects.

We could also skip the intermediate step with target number of objects
and rewrite the heuristic in terms of pages. However we still have the
sysfs file cpu_partial which uses number of objects and could break
existing users if it suddenly becomes number of pages, so this patch
doesn't do that.

In practice, after this patch the heuristics limit the size of percpu
partial list up to 2 pages. In case of a reported regression (which
would mean some workload has benefited from the previous imprecise
object based counting), we can tune the heuristics to get a better
compromise within the new scheme, while still avoid the unexpectedly
long percpu partial lists.

[1] https://lore.kernel.org/linux-mm/CAG48ez2Qx5K1Cab-m8BdSibp6wLTip6ro4=-umR7BLsEgjEYzA@mail.gmail.com/
[2] https://lore.kernel.org/all/2f0f46e8-2535-410a-1859-e9cfa4e57c18@suse.cz/

==========
Evaluation
==========

Mel was kind enough to run v1 through mmtests machinery for netperf
(localhost) and hackbench and, for most significant results see below.
So there are some apparent regressions, especially with hackbench, which
I think ultimately boils down to having shorter percpu partial lists on
average and some benchmarks benefiting from longer ones. Monitoring
slab usage also indicated less memory usage by slab. Based on that, the
following patch will bump the defaults to allow longer percpu partial
lists than after this patch.

However the goal is certainly not such that we would limit the percpu
partial lists to 30 pages just because previously a specific alloc/free
pattern could lead to the limit of 30 objects translate to a limit to 30
pages - that would make little sense. This is a correctness patch, and
if a workload benefits from larger lists, the sysfs tuning knobs are
still there to allow that.

Netperf

2-socket Intel(R) Xeon(R) Gold 5218R CPU @ 2.10GHz (20 cores, 40 threads per socket), 384GB RAM
TCP-RR:
hmean before 127045.79 after 121092.94 (-4.69%, worse)
stddev before 2634.37 after 1254.08
UDP-RR:
hmean before 166985.45 after 160668.94 ( -3.78%, worse)
stddev before 4059.69 after 1943.63

2-socket Intel(R) Xeon(R) CPU E5-2698 v4 @ 2.20GHz (20 cores, 40 threads per socket), 512GB RAM
TCP-RR:
hmean before 84173.25 after 76914.72 ( -8.62%, worse)
UDP-RR:
hmean before 93571.12 after 96428.69 ( 3.05%, better)
stddev before 23118.54 after 16828.14

2-socket Intel(R) Xeon(R) CPU E5-2670 v3 @ 2.30GHz (12 cores, 24 threads per socket), 64GB RAM
TCP-RR:
hmean before 49984.92 after 48922.27 ( -2.13%, worse)
stddev before 6248.15 after 4740.51
UDP-RR:
hmean before 61854.31 after 68761.81 ( 11.17%, better)
stddev before 4093.54 after 5898.91

other machines - within 2%

Hackbench

(results before and after the patch, negative % means worse)

2-socket AMD EPYC 7713 (64 cores, 128 threads per core), 256GB RAM
hackbench-process-sockets
Amean 1 0.5380 0.5583 ( -3.78%)
Amean 4 0.7510 0.8150 ( -8.52%)
Amean 7 0.7930 0.9533 ( -20.22%)
Amean 12 0.7853 1.1313 ( -44.06%)
Amean 21 1.1520 1.4993 ( -30.15%)
Amean 30 1.6223 1.9237 ( -18.57%)
Amean 48 2.6767 2.9903 ( -11.72%)
Amean 79 4.0257 5.1150 ( -27.06%)
Amean 110 5.5193 7.4720 ( -35.38%)
Amean 141 7.2207 9.9840 ( -38.27%)
Amean 172 8.4770 12.1963 ( -43.88%)
Amean 203 9.6473 14.3137 ( -48.37%)
Amean 234 11.3960 18.7917 ( -64.90%)
Amean 265 13.9627 22.4607 ( -60.86%)
Amean 296 14.9163 26.0483 ( -74.63%)

hackbench-thread-sockets
Amean 1 0.5597 0.5877 ( -5.00%)
Amean 4 0.7913 0.8960 ( -13.23%)
Amean 7 0.8190 1.0017 ( -22.30%)
Amean 12 0.9560 1.1727 ( -22.66%)
Amean 21 1.7587 1.5660 ( 10.96%)
Amean 30 2.4477 1.9807 ( 19.08%)
Amean 48 3.4573 3.0630 ( 11.41%)
Amean 79 4.7903 5.1733 ( -8.00%)
Amean 110 6.1370 7.4220 ( -20.94%)
Amean 141 7.5777 9.2617 ( -22.22%)
Amean 172 9.2280 11.0907 ( -20.18%)
Amean 203 10.2793 13.3470 ( -29.84%)
Amean 234 11.2410 17.1070 ( -52.18%)
Amean 265 12.5970 23.3323 ( -85.22%)
Amean 296 17.1540 24.2857 ( -41.57%)

2-socket Intel(R) Xeon(R) Gold 5218R CPU @ 2.10GHz (20 cores, 40 threads
per socket), 384GB RAM
hackbench-process-sockets
Amean 1 0.5760 0.4793 ( 16.78%)
Amean 4 0.9430 0.9707 ( -2.93%)
Amean 7 1.5517 1.8843 ( -21.44%)
Amean 12 2.4903 2.7267 ( -9.49%)
Amean 21 3.9560 4.2877 ( -8.38%)
Amean 30 5.4613 5.8343 ( -6.83%)
Amean 48 8.5337 9.2937 ( -8.91%)
Amean 79 14.0670 15.2630 ( -8.50%)
Amean 110 19.2253 21.2467 ( -10.51%)
Amean 141 23.7557 25.8550 ( -8.84%)
Amean 172 28.4407 29.7603 ( -4.64%)
Amean 203 33.3407 33.9927 ( -1.96%)
Amean 234 38.3633 39.1150 ( -1.96%)
Amean 265 43.4420 43.8470 ( -0.93%)
Amean 296 48.3680 48.9300 ( -1.16%)

hackbench-thread-sockets
Amean 1 0.6080 0.6493 ( -6.80%)
Amean 4 1.0000 1.0513 ( -5.13%)
Amean 7 1.6607 2.0260 ( -22.00%)
Amean 12 2.7637 2.9273 ( -5.92%)
Amean 21 5.0613 4.5153 ( 10.79%)
Amean 30 6.3340 6.1140 ( 3.47%)
Amean 48 9.0567 9.5577 ( -5.53%)
Amean 79 14.5657 15.7983 ( -8.46%)
Amean 110 19.6213 21.6333 ( -10.25%)
Amean 141 24.1563 26.2697 ( -8.75%)
Amean 172 28.9687 30.2187 ( -4.32%)
Amean 203 33.9763 34.6970 ( -2.12%)
Amean 234 38.8647 39.3207 ( -1.17%)
Amean 265 44.0813 44.1507 ( -0.16%)
Amean 296 49.2040 49.4330 ( -0.47%)

2-socket Intel(R) Xeon(R) CPU E5-2698 v4 @ 2.20GHz (20 cores, 40 threads
per socket), 512GB RAM
hackbench-process-sockets
Amean 1 0.5027 0.5017 ( 0.20%)
Amean 4 1.1053 1.2033 ( -8.87%)
Amean 7 1.8760 2.1820 ( -16.31%)
Amean 12 2.9053 3.1810 ( -9.49%)
Amean 21 4.6777 4.9920 ( -6.72%)
Amean 30 6.5180 6.7827 ( -4.06%)
Amean 48 10.0710 10.5227 ( -4.48%)
Amean 79 16.4250 17.5053 ( -6.58%)
Amean 110 22.6203 24.4617 ( -8.14%)
Amean 141 28.0967 31.0363 ( -10.46%)
Amean 172 34.4030 36.9233 ( -7.33%)
Amean 203 40.5933 43.0850 ( -6.14%)
Amean 234 46.6477 48.7220 ( -4.45%)
Amean 265 53.0530 53.9597 ( -1.71%)
Amean 296 59.2760 59.9213 ( -1.09%)

hackbench-thread-sockets
Amean 1 0.5363 0.5330 ( 0.62%)
Amean 4 1.1647 1.2157 ( -4.38%)
Amean 7 1.9237 2.2833 ( -18.70%)
Amean 12 2.9943 3.3110 ( -10.58%)
Amean 21 4.9987 5.1880 ( -3.79%)
Amean 30 6.7583 7.0043 ( -3.64%)
Amean 48 10.4547 10.8353 ( -3.64%)
Amean 79 16.6707 17.6790 ( -6.05%)
Amean 110 22.8207 24.4403 ( -7.10%)
Amean 141 28.7090 31.0533 ( -8.17%)
Amean 172 34.9387 36.8260 ( -5.40%)
Amean 203 41.1567 43.0450 ( -4.59%)
Amean 234 47.3790 48.5307 ( -2.43%)
Amean 265 53.9543 54.6987 ( -1.38%)
Amean 296 60.0820 60.2163 ( -0.22%)

1-socket Intel(R) Xeon(R) CPU E3-1240 v5 @ 3.50GHz (4 cores, 8 threads),
32 GB RAM
hackbench-process-sockets
Amean 1 1.4760 1.5773 ( -6.87%)
Amean 3 3.9370 4.0910 ( -3.91%)
Amean 5 6.6797 6.9357 ( -3.83%)
Amean 7 9.3367 9.7150 ( -4.05%)
Amean 12 15.7627 16.1400 ( -2.39%)
Amean 18 23.5360 23.6890 ( -0.65%)
Amean 24 31.0663 31.3137 ( -0.80%)
Amean 30 38.7283 39.0037 ( -0.71%)
Amean 32 41.3417 41.6097 ( -0.65%)

hackbench-thread-sockets
Amean 1 1.5250 1.6043 ( -5.20%)
Amean 3 4.0897 4.2603 ( -4.17%)
Amean 5 6.7760 7.0933 ( -4.68%)
Amean 7 9.4817 9.9157 ( -4.58%)
Amean 12 15.9610 16.3937 ( -2.71%)
Amean 18 23.9543 24.3417 ( -1.62%)
Amean 24 31.4400 31.7217 ( -0.90%)
Amean 30 39.2457 39.5467 ( -0.77%)
Amean 32 41.8267 42.1230 ( -0.71%)

2-socket Intel(R) Xeon(R) CPU E5-2670 v3 @ 2.30GHz (12 cores, 24 threads
per socket), 64GB RAM
hackbench-process-sockets
Amean 1 1.0347 1.0880 ( -5.15%)
Amean 4 1.7267 1.8527 ( -7.30%)
Amean 7 2.6707 2.8110 ( -5.25%)
Amean 12 4.1617 4.3383 ( -4.25%)
Amean 21 7.0070 7.2600 ( -3.61%)
Amean 30 9.9187 10.2397 ( -3.24%)
Amean 48 15.6710 16.3923 ( -4.60%)
Amean 79 24.7743 26.1247 ( -5.45%)
Amean 110 34.3000 35.9307 ( -4.75%)
Amean 141 44.2043 44.8010 ( -1.35%)
Amean 172 54.2430 54.7260 ( -0.89%)
Amean 192 60.6557 60.9777 ( -0.53%)

hackbench-thread-sockets
Amean 1 1.0610 1.1353 ( -7.01%)
Amean 4 1.7543 1.9140 ( -9.10%)
Amean 7 2.7840 2.9573 ( -6.23%)
Amean 12 4.3813 4.4937 ( -2.56%)
Amean 21 7.3460 7.5350 ( -2.57%)
Amean 30 10.2313 10.5190 ( -2.81%)
Amean 48 15.9700 16.5940 ( -3.91%)
Amean 79 25.3973 26.6637 ( -4.99%)
Amean 110 35.1087 36.4797 ( -3.91%)
Amean 141 45.8220 46.3053 ( -1.05%)
Amean 172 55.4917 55.7320 ( -0.43%)
Amean 192 62.7490 62.5410 ( 0.33%)

Link: https://lkml.kernel.org/r/20211012134651.11258-1-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reported-by: Jann Horn <jannh@google.com>
Cc: Roman Gushchin <guro@fb.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

coredump: Limit coredumps to a single thread group

Today when a signal is delivered with a handler of SIG_DFL whose
default behavior is to generate a core dump not only that process but
every process that shares the mm is killed.

In the case of vfork this looks like a real world problem. Consider
the following well defined sequence.

if (vfork() == 0) {
execve(...);
_exit(EXIT_FAILURE);
}

If a signal that generates a core dump is received after vfork but
before the execve changes the mm the process that called vfork will
also be killed (as the mm is shared).

Similarly if the execve fails after the point of no return the kernel
delivers SIGSEGV which will kill both the exec'ing process and because
the mm is shared the process that called vfork as well.

As far as I can tell this behavior is a violation of people's
reasonable expectations, POSIX, and is unnecessarily fragile when the
system is low on memory.

Solve this by making a userspace visible change to only kill a single
process/thread group. This is possible because Jann Horn recently
modified[1] the coredump code so that the mm can safely be modified
while the coredump is happening. With LinuxThreads long gone I don't
expect anyone to have a notice this behavior change in practice.

To accomplish this move the core_state pointer from mm_struct to
signal_struct, which allows different thread groups to coredump
simultatenously.

In zap_threads remove the work to kill anything except for the current
thread group.

v2: Remove core_state from the VM_BUG_ON_MM print to fix
compile failure when CONFIG_DEBUG_VM is enabled.
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>

[1] a07279c9a8cd ("binfmt_elf, binfmt_elf_fdpic: use a VMA list snapshot")
Fixes: d89f3847def4 ("[PATCH] thread-aware coredumps, 2.5.43-C3")
History-tree: git://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git
Link: https://lkml.kernel.org/r/87y27mvnke.fsf@disp2133
Link: https://lkml.kernel.org/r/20211007144701.67592574@canb.auug.org.au
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

page_pool: disable dma mapping support for 32-bit arch with 64-bit DMA

As the 32-bit arch with 64-bit DMA seems to rare those days,
and page pool might carry a lot of code and complexity for
systems that possibly.

So disable dma mapping support for such systems, if drivers
really want to work on such systems, they have to implement
their own DMA-mapping fallback tracking outside page_pool.

Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com>
Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

sched: Move mmdrop to RCU on RT

mmdrop() is invoked from finish_task_switch() by the incoming task to drop
the mm which was handed over by the previous task. mmdrop() can be quite
expensive which prevents an incoming real-time task from getting useful
work done.

Provide mmdrop_sched() which maps to mmdrop() on !RT kernels. On RT kernels
it delagates the eventually required invocation of __mmdrop() to RCU.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210928122411.648582026@linutronix.de

mm: Add folio_mapped()

This function is the equivalent of page_mapped(). It is slightly
shorter as we do not need to handle the PageTail() case. Reimplement
page_mapped() as a wrapper around folio_mapped(). folio_mapped()
is 13 bytes smaller than page_mapped(), but the page_mapped() wrapper
is 30 bytes, for a net increase of 17 bytes of text.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: William Kucharski <william.kucharski@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: David Howells <dhowells@redhat.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Mike Rapoport <rppt@linux.ibm.com>

mm: Handle per-folio private data

Add folio_get_private() which mirrors page_private() -- ie folio private
data is the same as page private data. The only difference is that these
return a void * instead of an unsigned long, which matches the majority
of users.

Turn attach_page_private() into folio_attach_private() and reimplement
attach_page_private() as a wrapper. No filesystem which uses page private
data currently supports compound pages, so we're free to define the rules.
attach_page_private() may only be called on a head page; if you want
to add private data to a tail page, you can call set_page_private()
directly (and shouldn't increment the page refcount! That should be
done when adding private data to the head page / folio).

This saves 813 bytes of text with the distro-derived config that I'm
testing due to removing the calls to compound_head() in get_page()
& put_page().

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Acked-by: Jeff Layton <jlayton@kernel.org>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: William Kucharski <william.kucharski@oracle.com>
Reviewed-by: David Howells <dhowells@redhat.com>
Acked-by: Mike Rapoport <rppt@linux.ibm.com>

mm: Introduce struct folio

A struct folio is a new abstraction to replace the venerable struct page.
A function which takes a struct folio argument declares that it will
operate on the entire (possibly compound) page, not just PAGE_SIZE bytes.
In return, the caller guarantees that the pointer it is passing does
not point to a tail page. No change to generated code.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: Jeff Layton <jlayton@kernel.org>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: William Kucharski <william.kucharski@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: David Howells <dhowells@redhat.com>
Acked-by: Mike Rapoport <rppt@linux.ibm.com>

page_pool: add interface to manipulate frag count in page pool

For 32 bit systems with 64 bit dma, dma_addr[1] is used to
store the upper 32 bit dma addr, those system should be rare
those days.

For normal system, the dma_addr[1] in 'struct page' is not
used, so we can reuse dma_addr[1] for storing frag count,
which means how many frags this page might be splited to.

In order to simplify the page frag support in the page pool,
the PAGE_POOL_DMA_USE_PP_FRAG_COUNT macro is added to indicate
the 32 bit systems with 64 bit dma, and the page frag support
in page pool is disabled for such system.

The newly added page_pool_set_frag_count() is called to reserve
the maximum frag count before any page frag is passed to the
user. The page_pool_atomic_sub_frag_count_return() is called
when user is done with the page frag.

Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

mm: fix spelling mistakes

Fix some spelling mistakes in comments:
each having differents usage ==> each has a different usage
statments ==> statements
adresses ==> addresses
aggresive ==> aggressive
datas ==> data
posion ==> poison
higer ==> higher
precisly ==> precisely
wont ==> won't
We moves tha ==> We move the
endianess ==> endianness

Link: https://lkml.kernel.org/r/20210519065853.7723-2-thunder.leizhen@huawei.com
Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Reviewed-by: Souptick Joarder <jrdr.linux@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: add a signature in struct page

This is needed by the page_pool to avoid recycling a page not allocated
via page_pool.

The page->signature field is aliased to page->lru.next and
page->compound_head, but it can't be set by mistake because the
signature value is a bad pointer, and can't trigger a false positive
in PageTail() because the last bit is 0.

Co-developed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Matteo Croce <mcroce@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

mm: gup: pack has_pinned in MMF_HAS_PINNED

has_pinned 32bit can be packed in the MMF_HAS_PINNED bit as a noop
cleanup.

Any atomic_inc/dec to the mm cacheline shared by all threads in pin-fast
would reintroduce a loss of SMP scalability to pin-fast, so there's no
future potential usefulness to keep an atomic in the mm for this.

set_bit(MMF_HAS_PINNED) will be theoretically a bit slower than WRITE_ONCE
(atomic_set is equivalent to WRITE_ONCE), but the set_bit (just like
atomic_set after this commit) has to be still issued only once per "mm",
so the difference between the two will be lost in the noise.

will-it-scale "mmap2" shows no change in performance with enterprise
config as expected.

will-it-scale "pin_fast" retains the > 4000% SMP scalability performance
improvement against upstream as expected.

This is a noop as far as overall performance and SMP scalability are
concerned.

[peterx@redhat.com: pack has_pinned in MMF_HAS_PINNED]
Link: https://lkml.kernel.org/r/YJqWESqyxa8OZA+2@t490s
[akpm@linux-foundation.org: coding style fixes]
[peterx@redhat.com: fix build for task_mmu.c, introduce mm_set_has_pinned_flag, fix comments]

Link: https://lkml.kernel.org/r/20210507150553.208763-4-peterx@redhat.com
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jann Horn <jannh@google.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Kirill Shutemov <kirill@shutemov.name>
Cc: Kirill Tkhai <ktkhai@virtuozzo.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: relocate 'write_protect_seq' in struct mm_struct

0day robot reported a 9.2% regression for will-it-scale mmap1 test
case[1], caused by commit 57efa1fe5957 ("mm/gup: prevent gup_fast from
racing with COW during fork").

Further debug shows the regression is due to that commit changes the
offset of hot fields 'mmap_lock' inside structure 'mm_struct', thus some
cache alignment changes.

From the perf data, the contention for 'mmap_lock' is very severe and
takes around 95% cpu cycles, and it is a rw_semaphore

struct rw_semaphore {
atomic_long_t count; /* 8 bytes */
atomic_long_t owner; /* 8 bytes */
struct optimistic_spin_queue osq; /* spinner MCS lock */
...

Before commit 57efa1fe5957 adds the 'write_protect_seq', it happens to
have a very optimal cache alignment layout, as Linus explained:

"and before the addition of the 'write_protect_seq' field, the
mmap_sem was at offset 120 in 'struct mm_struct'.

Which meant that count and owner were in two different cachelines,
and then when you have contention and spend time in
rwsem_down_write_slowpath(), this is probably *exactly* the kind
of layout you want.

Because first the rwsem_write_trylock() will do a cmpxchg on the
first cacheline (for the optimistic fast-path), and then in the
case of contention, rwsem_down_write_slowpath() will just access
the second cacheline.

Which is probably just optimal for a load that spends a lot of
time contended - new waiters touch that first cacheline, and then
they queue themselves up on the second cacheline."

After the commit, the rw_semaphore is at offset 128, which means the
'count' and 'owner' fields are now in the same cacheline, and causes
more cache bouncing.

Currently there are 3 "#ifdef CONFIG_XXX" before 'mmap_lock' which will
affect its offset:

CONFIG_MMU
CONFIG_MEMBARRIER
CONFIG_HAVE_ARCH_COMPAT_MMAP_BASES

The layout above is on 64 bits system with 0day's default kernel config
(similar to RHEL-8.3's config), in which all these 3 options are 'y'.
And the layout can vary with different kernel configs.

Relayouting a structure is usually a double-edged sword, as sometimes it
can helps one case, but hurt other cases. For this case, one solution
is, as the newly added 'write_protect_seq' is a 4 bytes long seqcount_t
(when CONFIG_DEBUG_LOCK_ALLOC=n), placing it into an existing 4 bytes
hole in 'mm_struct' will not change other fields' alignment, while
restoring the regression.

Link: https://lore.kernel.org/lkml/20210525031636.GB7744@xsang-OptiPlex-9020/ [1]
Reported-by: kernel test robot <oliver.sang@intel.com>
Signed-off-by: Feng Tang <feng.tang@intel.com>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Cc: Peter Xu <peterx@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: fix struct page layout on 32-bit systems

32-bit architectures which expect 8-byte alignment for 8-byte integers and
need 64-bit DMA addresses (arm, mips, ppc) had their struct page
inadvertently expanded in 2019. When the dma_addr_t was added, it forced
the alignment of the union to 8 bytes, which inserted a 4 byte gap between
'flags' and the union.

Fix this by storing the dma_addr_t in one or two adjacent unsigned longs.
This restores the alignment to that of an unsigned long. We always
store the low bits in the first word to prevent the PageTail bit from
being inadvertently set on a big endian platform. If that happened,
get_user_pages_fast() racing against a page which was freed and
reallocated to the page_pool could dereference a bogus compound_head(),
which would be hard to trace back to this cause.

Link: https://lkml.kernel.org/r/20210510153211.1504886-1-willy@infradead.org
Fixes: c25fff7171be ("mm: add dma_addr_t to struct page")
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Tested-by: Matteo Croce <mcroce@linux.microsoft.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/fork: clear PASID for new mm

When a new mm is created, its PASID should be cleared, i.e. the PASID is
initialized to its init state 0 on both ARM and X86.

This patch was part of the series introducing mm->pasid, but got lost
along the way [1]. It still makes sense to have it, because each address
space has a different PASID. And the IOMMU code in
iommu_sva_alloc_pasid() expects the pasid field of a new mm struct to be
cleared.

[1] https://lore.kernel.org/linux-iommu/YDgh53AcQHT+T3L0@otcwcpicx3.sc.intel.com/

Link: https://lkml.kernel.org/r/20210302103837.2562625-1-jean-philippe@linaro.org
Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Cc: Jacob Pan <jacob.jun.pan@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

tlb: mmu_gather: Remove start/end arguments from tlb_gather_mmu()

The 'start' and 'end' arguments to tlb_gather_mmu() are no longer
needed now that there is a separate function for 'fullmm' flushing.

Remove the unused arguments and update all callers.

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Yu Zhao <yuzhao@google.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/CAHk-=wjQWa14_4UpfDf=fiineNP+RH74kZeDMo_f1D35xNzq9w@mail.gmail.com

tlb: mmu_gather: Introduce tlb_gather_mmu_fullmm()

Passing the range '0, -1' to tlb_gather_mmu() sets the 'fullmm' flag,
which indicates that the mm_struct being operated on is going away. In
this case, some architectures (such as arm64) can elide TLB invalidation
by ensuring that the TLB tag (ASID) associated with this mm is not
immediately reclaimed. Although this behaviour is documented in
asm-generic/tlb.h, it's subtle and easily missed.

Introduce tlb_gather_mmu_fullmm() to make it clearer that this is for the
entire mm and WARN() if tlb_gather_mmu() is called with the 'fullmm'
address range.

Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Yu Zhao <yuzhao@google.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lkml.kernel.org/r/20210127235347.1402-4-will@kernel.org

tlb: mmu_gather: Remove unused start/end arguments from tlb_finish_mmu()

Since commit 7a30df49f63a ("mm: mmu_gather: remove __tlb_reset_range()
for force flush"), the 'start' and 'end' arguments to tlb_finish_mmu()
are no longer used, since we flush the whole mm in case of a nested
invalidation.

Remove the unused arguments and update all callers.

Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Yu Zhao <yuzhao@google.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lkml.kernel.org/r/20210127235347.1402-3-will@kernel.org

mm/lru: revise the comments of lru_lock

Since we changed the pgdat->lru_lock to lruvec->lru_lock, it's time to fix
the incorrect comments in code. Also fixed some zone->lru_lock comment
error from ancient time. etc.

I struggled to understand the comment above move_pages_to_lru() (surely
it never calls page_referenced()), and eventually realized that most of
it had got separated from shrink_active_list(): move that comment back.

Link: https://lkml.kernel.org/r/1604566549-62481-20-git-send-email-alex.shi@linux.alibaba.com
Signed-off-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Tejun Heo <tj@kernel.org>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Jann Horn <jannh@google.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Alexander Duyck <alexander.duyck@gmail.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: "Chen, Rong A" <rong.a.chen@intel.com>
Cc: Daniel Jordan <daniel.m.jordan@oracle.com>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Kirill A. Shutemov <kirill@shutemov.name>
Cc: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mika Penttilä <mika.penttila@nextfour.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Yang Shi <yang.shi@linux.alibaba.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/gup: prevent gup_fast from racing with COW during fork

Since commit 70e806e4e645 ("mm: Do early cow for pinned pages during
fork() for ptes") pages under a FOLL_PIN will not be write protected
during COW for fork. This means that pages returned from
pin_user_pages(FOLL_WRITE) should not become write protected while the pin
is active.

However, there is a small race where get_user_pages_fast(FOLL_PIN) can
establish a FOLL_PIN at the same time copy_present_page() is write
protecting it:

CPU 0 CPU 1
get_user_pages_fast()
internal_get_user_pages_fast()
copy_page_range()
pte_alloc_map_lock()
copy_present_page()
atomic_read(has_pinned) == 0
page_maybe_dma_pinned() == false
atomic_set(has_pinned, 1);
gup_pgd_range()
gup_pte_range()
pte_t pte = gup_get_pte(ptep)
pte_access_permitted(pte)
try_grab_compound_head()
pte = pte_wrprotect(pte)
set_pte_at();
pte_unmap_unlock()
// GUP now returns with a write protected page

The first attempt to resolve this by using the write protect caused
problems (and was missing a barrrier), see commit f3c64eda3e50 ("mm: avoid
early COW write protect games during fork()")

Instead wrap copy_p4d_range() with the write side of a seqcount and check
the read side around gup_pgd_range(). If there is a collision then
get_user_pages_fast() fails and falls back to slow GUP.

Slow GUP is safe against this race because copy_page_range() is only
called while holding the exclusive side of the mmap_lock on the src
mm_struct.

[akpm@linux-foundation.org: coding style fixes]
Link: https://lore.kernel.org/r/CAHk-=wi=iCnYCARbPGjkVJu9eyYeZ13N64tZYLdOB8CP5Q_PLw@mail.gmail.com

Link: https://lkml.kernel.org/r/2-v4-908497cf359a+4782-gup_fork_jgg@nvidia.com
Fixes: f3c64eda3e50 ("mm: avoid early COW write protect games during fork()")
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Peter Xu <peterx@redhat.com>
Acked-by: "Ahmed S. Darwish" <a.darwish@linutronix.de> [seqcount_t parts]
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jann Horn <jannh@google.com>
Cc: Kirill Shutemov <kirill@shutemov.name>
Cc: Kirill Tkhai <ktkhai@virtuozzo.com>
Cc: Leon Romanovsky <leonro@nvidia.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: memcontrol: Use helpers to read page's memcg data

Patch series "mm: allow mapping accounted kernel pages to userspace", v6.

Currently a non-slab kernel page which has been charged to a memory cgroup
can't be mapped to userspace. The underlying reason is simple: PageKmemcg
flag is defined as a page type (like buddy, offline, etc), so it takes a
bit from a page->mapped counter. Pages with a type set can't be mapped to
userspace.

But in general the kmemcg flag has nothing to do with mapping to
userspace. It only means that the page has been accounted by the page
allocator, so it has to be properly uncharged on release.

Some bpf maps are mapping the vmalloc-based memory to userspace, and their
memory can't be accounted because of this implementation detail.

This patchset removes this limitation by moving the PageKmemcg flag into
one of the free bits of the page->mem_cgroup pointer. Also it formalizes
accesses to the page->mem_cgroup and page->obj_cgroups using new helpers,
adds several checks and removes a couple of obsolete functions. As the
result the code became more robust with fewer open-coded bit tricks.

This patch (of 4):

Currently there are many open-coded reads of the page->mem_cgroup pointer,
as well as a couple of read helpers, which are barely used.

It creates an obstacle on a way to reuse some bits of the pointer for
storing additional bits of information. In fact, we already do this for
slab pages, where the last bit indicates that a pointer has an attached
vector of objcg pointers instead of a regular memcg pointer.

This commits uses 2 existing helpers and introduces a new helper to
converts all read sides to calls of these helpers:
struct mem_cgroup *page_memcg(struct page *page);
struct mem_cgroup *page_memcg_rcu(struct page *page);
struct mem_cgroup *page_memcg_check(struct page *page);

page_memcg_check() is intended to be used in cases when the page can be a
slab page and have a memcg pointer pointing at objcg vector. It does
check the lowest bit, and if set, returns NULL. page_memcg() contains a
VM_BUG_ON_PAGE() check for the page not being a slab page.

To make sure nobody uses a direct access, struct page's
mem_cgroup/obj_cgroups is converted to unsigned long memcg_data.

Signed-off-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Link: https://lkml.kernel.org/r/20201027001657.3398190-1-guro@fb.com
Link: https://lkml.kernel.org/r/20201027001657.3398190-2-guro@fb.com
Link: https://lore.kernel.org/bpf/20201201215900.3569844-2-guro@fb.com

mm: Introduce mm_struct.has_pinned

(Commit message majorly collected from Jason Gunthorpe)

Reduce the chance of false positive from page_maybe_dma_pinned() by
keeping track if the mm_struct has ever been used with pin_user_pages().
This allows cases that might drive up the page ref_count to avoid any
penalty from handling dma_pinned pages.

Future work is planned, to provide a more sophisticated solution, likely
to turn it into a real counter. For now, make it atomic_t but use it as
a boolean for simplicity.

Suggested-by: Jason Gunthorpe <jgg@ziepe.ca>
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: Add a pasid member to struct mm_struct

A PASID is shared by all threads in a process. So the logical place to
keep track of it is in the mm_struct. Both ARM and x86 would use this
PASID.

[ bp: Massage commit message. ]

Suggested-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Link: https://lkml.kernel.org/r/1600187413-163670-8-git-send-email-fenghua.yu@intel.com

mm: store compound_nr as well as compound_order

Patch series "THP prep patches".

These are some generic cleanups and improvements, which I would like
merged into mmotm soon. The first one should be a performance improvement
for all users of compound pages, and the others are aimed at getting code
to compile away when CONFIG_TRANSPARENT_HUGEPAGE is disabled (ie small
systems). Also better documented / less confusing than the current prefix
mixture of compound, hpage and thp.

This patch (of 7):

This removes a few instructions from functions which need to know how many
pages are in a compound page. The storage used is either page->mapping on
64-bit or page->index on 32-bit. Both of these are fine to overlay on
tail pages.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: William Kucharski <william.kucharski@oracle.com>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Link: http://lkml.kernel.org/r/20200629151959.15779-1-willy@infradead.org
Link: http://lkml.kernel.org/r/20200629151959.15779-2-willy@infradead.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: memcg/slab: allocate obj_cgroups for non-root slab pages

Allocate and release memory to store obj_cgroup pointers for each non-root
slab page. Reuse page->mem_cgroup pointer to store a pointer to the
allocated space.

This commit temporarily increases the memory footprint of the kernel memory
accounting. To store obj_cgroup pointers we'll need a place for an
objcg_pointer for each allocated object. However, the following patches
in the series will enable sharing of slab pages between memory cgroups,
which will dramatically increase the total slab utilization. And the final
memory footprint will be significantly smaller than before.

To distinguish between obj_cgroups and memcg pointers in case when it's
not obvious which one is used (as in page_cgroup_ino()), let's always set
the lowest bit in the obj_cgroup case. The original obj_cgroups
pointer is marked to be ignored by kmemleak, which otherwise would
report a memory leak for each allocated vector.

Signed-off-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Tejun Heo <tj@kernel.org>
Link: http://lkml.kernel.org/r/20200623174037.3951353-8-guro@fb.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mmap locking API: convert mmap_sem comments

Convert comments that reference mmap_sem to reference mmap_lock instead.

[akpm@linux-foundation.org: fix up linux-next leftovers]
[akpm@linux-foundation.org: s/lockaphore/lock/, per Vlastimil]
[akpm@linux-foundation.org: more linux-next fixups, per Michel]

Signed-off-by: Michel Lespinasse <walken@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Cc: Davidlohr Bueso <dbueso@suse.de>
Cc: David Rientjes <rientjes@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Laurent Dufour <ldufour@linux.ibm.com>
Cc: Liam Howlett <Liam.Howlett@oracle.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ying Han <yinghan@google.com>
Link: http://lkml.kernel.org/r/20200520052908.204642-13-walken@google.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mmap locking API: rename mmap_sem to mmap_lock

Rename the mmap_sem field to mmap_lock. Any new uses of this lock should
now go through the new mmap locking api. The mmap_lock is still
implemented as a rwsem, though this could change in the future.

[akpm@linux-foundation.org: fix it for mm-gup-might_lock_readmmap_sem-in-get_user_pages_fast.patch]

Signed-off-by: Michel Lespinasse <walken@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Davidlohr Bueso <dbueso@suse.de>
Reviewed-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Laurent Dufour <ldufour@linux.ibm.com>
Cc: Liam Howlett <Liam.Howlett@oracle.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ying Han <yinghan@google.com>
Link: http://lkml.kernel.org/r/20200520052908.204642-11-walken@google.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm_types.h: change set_page_private to inline function

Change it to inline function to make callers use the proper argument. And
no need for it to be macro per Andrew's comment [1].

[1] https://lore.kernel.org/lkml/20200518221235.1fa32c38e5766113f78e3f0d@linux-foundation.org/

Signed-off-by: Guoqing Jiang <guoqing.jiang@cloud.ionos.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/20200525203149.18802-1-guoqing.jiang@cloud.ionos.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: fix ambiguous comments for better code readability

The parameter of remap_pfn_range() @pfn passed from the caller is actually
a page-frame number converted by corresponding physical address of kernel
memory, the original comment is ambiguous that may mislead the users.

Meanwhile, there is an ambiguous typo "VMM" in the comment of
vm_area_struct. So fixing them will make the code more readable.

Signed-off-by: chenqiwu <chenqiwu@xiaomi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/1583026921-15279-1-git-send-email-qiwuchen55@gmail.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/gup: page->hpage_pinned_refcount: exact pin counts for huge pages

For huge pages (and in fact, any compound page), the GUP_PIN_COUNTING_BIAS
scheme tends to overflow too easily, each tail page increments the head
page->_refcount by GUP_PIN_COUNTING_BIAS (1024). That limits the number
of huge pages that can be pinned.

This patch removes that limitation, by using an exact form of pin counting
for compound pages of order > 1. The "order > 1" is required because this
approach uses the 3rd struct page in the compound page, and order 1
compound pages only have two pages, so that won't work there.

A new struct page field, hpage_pinned_refcount, has been added, replacing
a padding field in the union (so no new space is used).

This enhancement also has a useful side effect: huge pages and compound
pages (of order > 1) do not suffer from the "potential false positives"
problem that is discussed in the page_dma_pinned() comment block. That is
because these compound pages have extra space for tracking things, so they
get exact pin counts instead of overloading page->_refcount.

Documentation/core-api/pin_user_pages.rst is updated accordingly.

Suggested-by: Jan Kara <jack@suse.cz>
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Link: http://lkml.kernel.org/r/20200211001536.1027652-8-jhubbard@nvidia.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: Add a vmf_insert_mixed_prot() function

The TTM module today uses a hack to be able to set a different page
protection than struct vm_area_struct::vm_page_prot. To be able to do
this properly, add the needed vm functionality as vmf_insert_mixed_prot().

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Cc: "Jérôme Glisse" <jglisse@redhat.com>
Cc: "Christian König" <christian.koenig@amd.com>
Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Acked-by: Christian König <christian.koenig@amd.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Andrew Morton <akpm@linux-foundation.org>

mm/mmu_notifier: Rename struct mmu_notifier_mm to mmu_notifier_subscriptions

The name mmu_notifier_mm implies that the thing is a mm_struct pointer,
and is difficult to abbreviate. The struct is actually holding the
interval tree and hlist containing the notifiers subscribed to a mm.

Use 'subscriptions' as the variable name for this struct instead of the
really terrible and misleading 'mmn_mm'.

Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

mm: thp: handle page cache THP correctly in PageTransCompoundMap

We have a usecase to use tmpfs as QEMU memory backend and we would like
to take the advantage of THP as well. But, our test shows the EPT is
not PMD mapped even though the underlying THP are PMD mapped on host.
The number showed by /sys/kernel/debug/kvm/largepage is much less than
the number of PMD mapped shmem pages as the below:

7f2778200000-7f2878200000 rw-s 00000000 00:14 262232 /dev/shm/qemu_back_mem.mem.Hz2hSf (deleted)
Size: 4194304 kB
[snip]
AnonHugePages: 0 kB
ShmemPmdMapped: 579584 kB
[snip]
Locked: 0 kB

cat /sys/kernel/debug/kvm/largepages
12

And some benchmarks do worse than with anonymous THPs.

By digging into the code we figured out that commit 127393fbe597 ("mm:
thp: kvm: fix memory corruption in KVM with THP enabled") checks if
there is a single PTE mapping on the page for anonymous THP when setting
up EPT map. But the _mapcount < 0 check doesn't work for page cache THP
since every subpage of page cache THP would get _mapcount inc'ed once it
is PMD mapped, so PageTransCompoundMap() always returns false for page
cache THP. This would prevent KVM from setting up PMD mapped EPT entry.

So we need handle page cache THP correctly. However, when page cache
THP's PMD gets split, kernel just remove the map instead of setting up
PTE map like what anonymous THP does. Before KVM calls get_user_pages()
the subpages may get PTE mapped even though it is still a THP since the
page cache THP may be mapped by other processes at the mean time.

Checking its _mapcount and whether the THP has PTE mapped or not.
Although this may report some false negative cases (PTE mapped by other
processes), it looks not trivial to make this accurate.

With this fix /sys/kernel/debug/kvm/largepage would show reasonable
pages are PMD mapped by EPT as the below:

7fbeaee00000-7fbfaee00000 rw-s 00000000 00:14 275464 /dev/shm/qemu_back_mem.mem.SKUvat (deleted)
Size: 4194304 kB
[snip]
AnonHugePages: 0 kB
ShmemPmdMapped: 557056 kB
[snip]
Locked: 0 kB

cat /sys/kernel/debug/kvm/largepages
271

And the benchmarks are as same as anonymous THPs.

[yang.shi@linux.alibaba.com: v4]
Link: http://lkml.kernel.org/r/1571865575-42913-1-git-send-email-yang.shi@linux.alibaba.com
Link: http://lkml.kernel.org/r/1571769577-89735-1-git-send-email-yang.shi@linux.alibaba.com
Fixes: dd78fedde4b9 ("rmap: support file thp")
Signed-off-by: Yang Shi <yang.shi@linux.alibaba.com>
Reported-by: Gang Deng <gavin.dg@linux.alibaba.com>
Tested-by: Gang Deng <gavin.dg@linux.alibaba.com>
Suggested-by: Hugh Dickins <hughd@google.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: <stable@vger.kernel.org> [4.8+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

sched/membarrier: Fix p->mm->membarrier_state racy load

The membarrier_state field is located within the mm_struct, which
is not guaranteed to exist when used from runqueue-lock-free iteration
on runqueues by the membarrier system call.

Copy the membarrier_state from the mm_struct into the scheduler runqueue
when the scheduler switches between mm.

When registering membarrier for mm, after setting the registration bit
in the mm membarrier state, issue a synchronize_rcu() to ensure the
scheduler observes the change. In order to take care of the case
where a runqueue keeps executing the target mm without swapping to
other mm, iterate over each runqueue and issue an IPI to copy the
membarrier_state from the mm_struct into each runqueue which have the
same mm which state has just been modified.

Move the mm membarrier_state field closer to pgd in mm_struct to use
a cache line already touched by the scheduler switch_mm.

The membarrier_execve() (now membarrier_exec_mmap) hook now needs to
clear the runqueue's membarrier state in addition to clear the mm
membarrier state, so move its implementation into the scheduler
membarrier code so it can access the runqueue structure.

Add memory barrier in membarrier_exec_mmap() prior to clearing
the membarrier state, ensuring memory accesses executed prior to exec
are not reordered with the stores clearing the membarrier state.

As suggested by Linus, move all membarrier.c RCU read-side locks outside
of the for each cpu loops.

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Kirill Tkhai <tkhai@yandex.ru>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Paul E. McKenney <paulmck@linux.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Russell King - ARM Linux admin <linux@armlinux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20190919173705.2181-5-mathieu.desnoyers@efficios.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

mm: thp: make deferred split shrinker memcg aware

Currently THP deferred split shrinker is not memcg aware, this may cause
premature OOM with some configuration. For example the below test would
run into premature OOM easily:

$ cgcreate -g memory:thp
$ echo 4G > /sys/fs/cgroup/memory/thp/memory/limit_in_bytes
$ cgexec -g memory:thp transhuge-stress 4000

transhuge-stress comes from kernel selftest.

It is easy to hit OOM, but there are still a lot THP on the deferred split
queue, memcg direct reclaim can't touch them since the deferred split
shrinker is not memcg aware.

Convert deferred split shrinker memcg aware by introducing per memcg
deferred split queue. The THP should be on either per node or per memcg
deferred split queue if it belongs to a memcg. When the page is
immigrated to the other memcg, it will be immigrated to the target memcg's
deferred split queue too.

Reuse the second tail page's deferred_list for per memcg list since the
same THP can't be on multiple deferred split queues.

[yang.shi@linux.alibaba.com: simplify deferred split queue dereference per Kirill Tkhai]
Link: http://lkml.kernel.org/r/1566496227-84952-5-git-send-email-yang.shi@linux.alibaba.com
Link: http://lkml.kernel.org/r/1565144277-36240-5-git-send-email-yang.shi@linux.alibaba.com
Signed-off-by: Yang Shi <yang.shi@linux.alibaba.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Qian Cai <cai@lca.pw>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

hmm: use mmu_notifier_get/put for 'struct hmm'

This is a significant simplification, it eliminates all the remaining
'hmm' stuff in mm_struct, eliminates krefing along the critical notifier
paths, and takes away all the ugly locking and abuse of page_table_lock.

mmu_notifier_get() provides the single struct hmm per struct mm which
eliminates mm->hmm.

It also directly guarantees that no mmu_notifier op callback is callable
while concurrent free is possible, this eliminates all the krefs inside
the mmu_notifier callbacks.

The remaining krefs in the range code were overly cautious, drivers are
already not permitted to free the mirror while a range exists.

Link: https://lore.kernel.org/r/20190806231548.25242-6-jgg@ziepe.ca
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ralph Campbell <rcampbell@nvidia.com>
Tested-by: Ralph Campbell <rcampbell@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

mm: document zone device struct page field usage

Patch series "mm/hmm: fixes for device private page migration", v3.

Testing the latest linux git tree turned up a few bugs with page
migration to and from ZONE_DEVICE private and anonymous pages.
Hopefully it clarifies how ZONE_DEVICE private struct page uses the same
mapping and index fields from the source anonymous page mapping.

This patch (of 3):

Struct page for ZONE_DEVICE private pages uses the page->mapping and and
page->index fields while the source anonymous pages are migrated to
device private memory. This is so rmap_walk() can find the page when
migrating the ZONE_DEVICE private page back to system memory.
ZONE_DEVICE pmem backed fsdax pages also use the page->mapping and
page->index fields when files are mapped into a process address space.

Add comments to struct page and remove the unused "_zd_pad_1" field to
make this more clear.

Link: http://lkml.kernel.org/r/20190724232700.23327-2-rcampbell@nvidia.com
Signed-off-by: Ralph Campbell <rcampbell@nvidia.com>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Christoph Lameter <cl@linux.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Jason Gunthorpe <jgg@mellanox.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/mm_types.h: ifdef struct vm_area_struct::swap_readahead_info

The field is only used in swap code.

Link: http://lkml.kernel.org/r/20190503190500.GA30589@avx2
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: remove the HMM config option

All the mm/hmm.c code is better keyed off HMM_MIRROR. Also let nouveau
depend on it instead of the mix of a dummy dependency symbol plus the
actually selected one. Drop various odd dependencies, as the code is
pretty portable.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: Jason Gunthorpe <jgg@mellanox.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

mm: simplify ZONE_DEVICE page private data

Remove the clumsy hmm_devmem_page_{get,set}_drvdata helpers, and
instead just access the page directly. Also make the page data
a void pointer, and thus much easier to use.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

mm: move buddy list manipulations into helpers

In preparation for runtime randomization of the zone lists, take all
(well, most of) the list_*() functions in the buddy allocator and put
them in helper functions. Provide a common control point for injecting
additional behavior when freeing pages.

[dan.j.williams@intel.com: fix buddy list helpers]
Link: http://lkml.kernel.org/r/155033679702.1773410.13041474192173212653.stgit@dwillia2-desk3.amr.corp.intel.com
[vbabka@suse.cz: remove del_page_from_free_area() migratetype parameter]
Link: http://lkml.kernel.org/r/4672701b-6775-6efd-0797-b6242591419e@suse.cz
Link: http://lkml.kernel.org/r/154899812264.3165233.5219320056406926223.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Tested-by: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Keith Busch <keith.busch@intel.com>
Cc: Robert Elliott <elliott@hpe.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: remove stale comment from page struct

We now use the slab_list list_head instead of the lru list_head. This
comment has become stale.

Remove stale comment from page struct slab_list list_head.

Link: http://lkml.kernel.org/r/20190402230545.2929-8-tobin@kernel.org
Signed-off-by: Tobin C. Harding <tobin@kernel.org>
Acked-by: Christoph Lameter <cl@linux.com>
Reviewed-by: Roman Gushchin <guro@fb.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Pekka Enberg <penberg@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: fix vm_fault_t cast in VM_FAULT_GET_HINDEX()

Symmetrically to VM_FAULT_SET_HINDEX(), we need a force-cast in
VM_FAULT_GET_HINDEX() to tell sparse that this is intentional.

Sparse complains about the current code when building a kernel with
CONFIG_MEMORY_FAILURE:

arch/x86/mm/fault.c:1058:53: warning: restricted vm_fault_t degrades to integer

Link: http://lkml.kernel.org/r/20190327204117.35215-1-jannh@google.com
Fixes: 3d3539018d2c ("mm: create the new vm_fault_t type")
Signed-off-by: Jann Horn <jannh@google.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Souptick Joarder <jrdr.linux@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Rik van Riel <riel@surriel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: create the new vm_fault_t type

Page fault handlers are supposed to return VM_FAULT codes, but some
drivers/file systems mistakenly return error numbers. Now that all
drivers/file systems have been converted to use the vm_fault_t return
type, change the type definition to no longer be compatible with 'int'.
By making it an unsigned int, the function prototype becomes
incompatible with a function which returns int. Sparse will detect any
attempts to return a value which is not a VM_FAULT code.

VM_FAULT_SET_HINDEX and VM_FAULT_GET_HINDEX values are changed to avoid
conflict with other VM_FAULT codes.

[jrdr.linux@gmail.com: fix warnings]
Link: http://lkml.kernel.org/r/20190109183742.GA24326@jordon-HP-15-Notebook-PC
Link: http://lkml.kernel.org/r/20190108183041.GA12137@jordon-HP-15-Notebook-PC
Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com>
Reviewed-by: William Kucharski <william.kucharski@oracle.com>
Reviewed-by: Mike Rapoport <rppt@linux.ibm.com>
Reviewed-by: Matthew Wilcox <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: remove zone_lru_lock() function, access ->lru_lock directly

We have common pattern to access lru_lock from a page pointer:
zone_lru_lock(page_zone(page))

Which is silly, because it unfolds to this:
&NODE_DATA(page_to_nid(page))->node_zones[page_zonenum(page)]->zone_pgdat->lru_lock
while we can simply do
&NODE_DATA(page_to_nid(page))->lru_lock

Remove zone_lru_lock() function, since it's only complicate things. Use
'page_pgdat(page)->lru_lock' pattern instead.

[aryabinin@virtuozzo.com: a slightly better version of __split_huge_page()]
Link: http://lkml.kernel.org/r/20190301121651.7741-1-aryabinin@virtuozzo.com
Link: http://lkml.kernel.org/r/20190228083329.31892-2-aryabinin@virtuozzo.com
Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: William Kucharski <william.kucharski@oracle.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: add dma_addr_t to struct page

The page_pool API is using page->private to store DMA addresses.
As pointed out by David Miller we can't use that on 32-bit architectures
with 64-bit DMA

This patch adds a new dma_addr_t struct to allow storing DMA addresses

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Acked-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

mm: make mm->pinned_vm an atomic64 counter

Taking a sleeping lock to _only_ increment a variable is quite the
overkill, and pretty much all users do this. Furthermore, some drivers
(ie: infiniband and scif) that need pinned semantics can go to quite
some trouble to actually delay via workqueue (un)accounting for pinned
pages when not possible to acquire it.

By making the counter atomic we no longer need to hold the mmap_sem and
can simply some code around it for pinned_vm users. The counter is 64-bit
such that we need not worry about overflows such as rdma user input
controlled from userspace.

Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: Christoph Lameter <cl@linux.com>
Reviewed-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

mm: introduce common STRUCT_PAGE_MAX_SHIFT define

This define is used by arm64 to calculate the size of the vmemmap
region. It is defined as the log2 of the upper bound on the size of a
struct page.

We move it into mm_types.h so it can be defined properly instead of set
and checked with a build bug. This also allows us to use the same
define for riscv.

Link: http://lkml.kernel.org/r/20181107205433.3875-2-logang@deltatee.com
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Acked-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: get rid of vmacache_flush_all() entirely

Jann Horn points out that the vmacache_flush_all() function is not only
potentially expensive, it's buggy too. It also happens to be entirely
unnecessary, because the sequence number overflow case can be avoided by
simply making the sequence number be 64-bit. That doesn't even grow the
data structures in question, because the other adjacent fields are
already 64-bit.

So simplify the whole thing by just making the sequence number overflow
case go away entirely, which gets rid of all the complications and makes
the code faster too. Win-win.

[ Oleg Nesterov points out that the VMACACHE_FULL_FLUSHES statistics
also just goes away entirely with this ]

Reported-by: Jann Horn <jannh@google.com>
Suggested-by: Will Deacon <will.deacon@arm.com>
Acked-by: Davidlohr Bueso <dave@stgolabs.net>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

powerpc/64s: Fix page table fragment refcount race vs speculative references

The page table fragment allocator uses the main page refcount racily
with respect to speculative references. A customer observed a BUG due
to page table page refcount underflow in the fragment allocator. This
can be caused by the fragment allocator set_page_count stomping on a
speculative reference, and then the speculative failure handler
decrements the new reference, and the underflow eventually pops when
the page tables are freed.

Fix this by using a dedicated field in the struct page for the page
table fragment allocator.

Fixes: 5c1f6ee9a31c ("powerpc: Reduce PTE table memory wastage")
Cc: stable@vger.kernel.org # v3.10+
Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

mm: Allocate the mm_cpumask (mm->cpu_bitmap[]) dynamically based on nr_cpu_ids

The mm_struct always contains a cpumask bitmap, regardless of
CONFIG_CPUMASK_OFFSTACK. That means the first step can be to
simplify things, and simply have one bitmask at the end of the
mm_struct for the mm_cpumask.

This does necessitate moving everything else in mm_struct into
an anonymous sub-structure, which can be randomized when struct
randomization is enabled.

The second step is to determine the correct size for the
mm_struct slab object from the size of the mm_struct
(excluding the CPU bitmap) and the size the cpumask.

For init_mm we can simply allocate the maximum size this
kernel is compiled for, since we only have one init_mm
in the system, anyway.

Pointer magic by Mike Galbraith, to evade -Wstringop-overflow
getting confused by the dynamically sized array.

Tested-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Rik van Riel <riel@surriel.com>
Signed-off-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Rik van Riel <riel@surriel.com>
Acked-by: Dave Hansen <dave.hansen@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: kernel-team@fb.com
Cc: luto@kernel.org
Link: http://lkml.kernel.org/r/20180716190337.26133-2-riel@surriel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

mm: add hmm_data to struct page

Make hmm_data an explicit member of the struct page union.

Link: http://lkml.kernel.org/r/20180518194519.3820-14-willy@infradead.org
Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Christoph Lameter <cl@linux.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: add pt_mm to struct page

For pgd page table pages, x86 overloads the page->index field to store a
pointer to the mm_struct. Rename this to pt_mm so it's visible to other
users.

Link: http://lkml.kernel.org/r/20180518194519.3820-13-willy@infradead.org
Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Christoph Lameter <cl@linux.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: improve struct page documentation

Rewrite the documentation to describe what you can use in struct page
rather than what you can't.

Link: http://lkml.kernel.org/r/20180518194519.3820-12-willy@infradead.org
Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Christoph Lameter <cl@linux.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: combine LRU and main union in struct page

This gives us five words of space in a single union in struct page. The
compound_mapcount moves position (from offset 24 to offset 20) on 64-bit
systems, but that does not seem likely to cause any trouble.

Link: http://lkml.kernel.org/r/20180518194519.3820-11-willy@infradead.org
Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: move lru union within struct page

Since the LRU is two words, this does not affect the double-word alignment
of SLUB's freelist.

Link: http://lkml.kernel.org/r/20180518194519.3820-10-willy@infradead.org
Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: combine first three unions in struct page

By combining these three one-word unions into one three-word union, we
make it easier for users to add their own multi-word fields to struct
page, as well as making it obvious that SLUB needs to keep its double-word
alignment for its freelist & counters.

No field moves position; verified with pahole.

Link: http://lkml.kernel.org/r/20180518194519.3820-8-willy@infradead.org
Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Christoph Lameter <cl@linux.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: move _refcount out of struct page union

Keeping the refcount in the union only encourages people to put something
else in the union which will overlap with _refcount and eventually explode
messily. pahole reports no fields change location.

Link: http://lkml.kernel.org/r/20180518194519.3820-7-willy@infradead.org
Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: move 'private' union within struct page

By moving page->private to the fourth word of struct page, we can put the
SLUB counters in the same word as SLAB's s_mem and still do the
cmpxchg_double trick. Now the SLUB counters no longer overlap with the
mapcount or refcount so we can drop the call to page_mapcount_reset() and
simplify set_page_slub_counters() to a single line.

Link: http://lkml.kernel.org/r/20180518194519.3820-6-willy@infradead.org
Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: switch s_mem and slab_cache in struct page

This will allow us to store slub's counters in the same bits as slab's
s_mem. slub now needs to set page->mapping to NULL as it frees the page,
just like slab does.

Link: http://lkml.kernel.org/r/20180518194519.3820-5-willy@infradead.org
Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Acked-by: Christoph Lameter <cl@linux.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: split page_type out from _mapcount

We're already using a union of many fields here, so stop abusing the
_mapcount and make page_type its own field. That implies renaming some of
the machinery that creates PageBuddy, PageBalloon and PageKmemcg; bring
back the PG_buddy, PG_balloon and PG_kmemcg names.

As suggested by Kirill, make page_type a bitmask. Because it starts out
life as -1 (thanks to sharing the storage with _mapcount), setting a page
flag means clearing the appropriate bit. This gives us space for probably
twenty or so extra bits (depending how paranoid we want to be about
_mapcount underflow).

Link: http://lkml.kernel.org/r/20180518194519.3820-3-willy@infradead.org
Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Christoph Lameter <cl@linux.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: change return type to vm_fault_t

Use new return type vm_fault_t for fault handler in struct
vm_operations_struct. For now, this is just documenting that the
function returns a VM_FAULT value rather than an errno. Once all
instances are converted, vm_fault_t will become a distinct type.

See commit 1c8f422059ae ("mm: change return type to vm_fault_t")

Link: http://lkml.kernel.org/r/20180512063745.GA26866@jordon-HP-15-Notebook-PC
Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com>
Reviewed-by: Matthew Wilcox <mawilcox@microsoft.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Joe Perches <joe@perches.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: introduce arg_lock to protect arg_start|end and env_start|end in mm_struct

mmap_sem is on the hot path of kernel, and it very contended, but it is
abused too. It is used to protect arg_start|end and evn_start|end when
reading /proc/$PID/cmdline and /proc/$PID/environ, but it doesn't make
sense since those proc files just expect to read 4 values atomically and
not related to VM, they could be set to arbitrary values by C/R.

And, the mmap_sem contention may cause unexpected issue like below:

INFO: task ps:14018 blocked for more than 120 seconds.
Tainted: G E 4.9.79-009.ali3000.alios7.x86_64 #1
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this
message.
ps D 0 14018 1 0x00000004
Call Trace:
schedule+0x36/0x80
rwsem_down_read_failed+0xf0/0x150
call_rwsem_down_read_failed+0x18/0x30
down_read+0x20/0x40
proc_pid_cmdline_read+0xd9/0x4e0
__vfs_read+0x37/0x150
vfs_read+0x96/0x130
SyS_read+0x55/0xc0
entry_SYSCALL_64_fastpath+0x1a/0xc5

Both Alexey Dobriyan and Michal Hocko suggested to use dedicated lock
for them to mitigate the abuse of mmap_sem.

So, introduce a new spinlock in mm_struct to protect the concurrent
access to arg_start|end, env_start|end and others, as well as replace
write map_sem to read to protect the race condition between prctl and
sys_brk which might break check_data_rlimit(), and makes prctl more
friendly to other VM operations.

This patch just eliminates the abuse of mmap_sem, but it can't resolve
the above hung task warning completely since the later
access_remote_vm() call needs acquire mmap_sem. The mmap_sem
scalability issue will be solved in the future.

[yang.shi@linux.alibaba.com: add comment about mmap_sem and arg_lock]
Link: http://lkml.kernel.org/r/1524077799-80690-1-git-send-email-yang.shi@linux.alibaba.com
Link: http://lkml.kernel.org/r/1523730291-109696-1-git-send-email-yang.shi@linux.alibaba.com
Signed-off-by: Yang Shi <yang.shi@linux.alibaba.com>
Reviewed-by: Cyrill Gorcunov <gorcunov@openvz.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mateusz Guzik <mguzik@redhat.com>
Cc: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: change return type to vm_fault_t

The plan for these patches is to introduce the typedef, initially just
as documentation ("These functions should return a VM_FAULT_ status").
We'll trickle the patches to individual drivers/filesystems in through
the maintainers, as far as possible. Then we'll change the typedef to
an unsigned int and break the compilation of any unconverted
drivers/filesystems.

vmf_insert_page(), vmf_insert_mixed() and vmf_insert_pfn() are three
newly added functions. The various drivers/filesystems where return
value of fault(), huge_fault(), page_mkwrite() and pfn_mkwrite() get
converted, will need them. These functions will return correct
VM_FAULT_ code based on err value.

We've had bugs before where drivers returned -EFOO. And we have this
silly inefficiency where vm_insert_xxx() return an errno which (afaict)
every driver then converts into a VM_FAULT code. In many cases drivers
failed to return correct VM_FAULT code value despite of vm_insert_xxx()
fails. We have indentified and clean up all those existing bugs and
silly inefficiencies in driver/filesystems by adding these three new
inline wrappers. As mentioned above, we will trickle those patches to
individual drivers/filesystems in through maintainers after these three
wrapper functions are merged.

Eventually we can convert vm_insert_xxx() into vmf_insert_xxx() and
remove these inline wrappers, but these are a good intermediate step.

Link: http://lkml.kernel.org/r/20180310162351.GA7422@jordon-HP-15-Notebook-PC
Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: remove reference to PG_buddy

PG_buddy doesn't exist any more. It's called PageBuddy now.

Link: http://lkml.kernel.org/r/20171220155552.15884-9-willy@infradead.org
Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Christoph Lameter <cl@linux.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>