mm/z3fold: fix the comment for __encode_handle()

The comment is confusing that Pool lock should be held as this function
accesses first_num above the __encode_handle() because first_num is the
element of z3fold_header which is protected by z3fold_header->page_lock.

I found the same comment for encode_handle() in zbud.c by accident ,Pool
lock should be held as this function accesses first|last_chunks, which is
the element of zbud_header and it does not have any lock, so pool lock
should be held.

Z3fold is based on zbud, maybe the comment come from zbud, but it was
wrong, so fix it.

Link: https://lkml.kernel.org/r/20240219024453.2240147-1-hezhongkun.hzk@bytedance.com
Signed-off-by: Zhongkun He <hezhongkun.hzk@bytedance.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/z3fold: remove obsolete comment for struct z3fold_pool

Since commit e774a7bc7f0a ("mm: zswap: remove page reclaim logic from
z3fold"), zpool and zpool_ops have been removed, so also remove the
corresponding comments.

Link: https://lkml.kernel.org/r/20230814221142.486548-1-xiujianfeng@huaweicloud.com
Signed-off-by: Xiu Jianfeng <xiujianfeng@huawei.com>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/z3fold: use helper function put_z3fold_locked() and put_z3fold_locked_list()

This code is already duplicated six times, use helper function
put_z3fold_locked() to release z3fold page instead of open code it to help
improve code readability a bit. And add put_z3fold_locked_list() helper
function to be consistent with it. No functional change involved.

Link: https://lkml.kernel.org/r/20230803113824.886413-1-ruanjinjie@huawei.com
Signed-off-by: Ruan Jinjie <ruanjinjie@huawei.com>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: zswap: remove shrink from zpool interface

Now that all three zswap backends have removed their shrink code, it is
no longer necessary for the zpool interface to include shrink/writeback
endpoints.

Link: https://lkml.kernel.org/r/20230612093815.133504-6-cerasuolodomenico@gmail.com
Signed-off-by: Domenico Cerasuolo <cerasuolodomenico@gmail.com>
Reviewed-by: Yosry Ahmed <yosryahmed@google.com>
Acked-by: Nhat Pham <nphamcs@gmail.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: zswap: remove page reclaim logic from z3fold

Switch z3fold to the new generic zswap LRU and remove its custom
implementation.

Link: https://lkml.kernel.org/r/20230612093815.133504-4-cerasuolodomenico@gmail.com
Signed-off-by: Domenico Cerasuolo <cerasuolodomenico@gmail.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: remove PageMovable export

The only in-kernel users that need PageMovable() to be exported are z3fold
and zsmalloc and they are only using it for dubious debugging
functionality. So remove those usages and the export so that no driver
code accidentally thinks that they are allowed to use this symbol.

Link: https://lkml.kernel.org/r/20230106135900.3763622-1-gregkh@linuxfoundation.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Acked-by: Minchan Kim <minchan@kernel.org>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

zpool: clean out dead code

There is a lot of provision for flexibility that isn't actually needed or
used. Zswap (the only zpool user) always passes zpool_ops with an .evict
method set. The backends who reclaim only do so for zswap, so they can
also directly call zpool_ops without indirection or checks.

Finally, there is no need to check the retries parameters and bail with
-EINVAL in the reclaim function, when that's called just a few lines below
with a hard-coded 8. There is no need to duplicate the evictable and
sleep_mapped attrs from the driver in zpool_ops.

Link: https://lkml.kernel.org/r/20221128191616.1261026-3-nphamcs@gmail.com
Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Nhat Pham <nphamcs@gmail.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: Convert all PageMovable users to movable_operations

These drivers are rather uncomfortably hammered into the
address_space_operations hole. They aren't filesystems and don't behave
like filesystems. They just need their own movable_operations structure,
which we can point to directly from page->mapping.

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

mm/z3fold: fix z3fold_page_migrate races with z3fold_map

Think about the below scenario:

CPU1 CPU2
z3fold_page_migrate z3fold_map
z3fold_page_trylock
...
z3fold_page_unlock
/* slots still points to old zhdr*/
get_z3fold_header
get slots from handle
get old zhdr from slots
z3fold_page_trylock
return *old* zhdr
encode_handle(new_zhdr, FIRST|LAST|MIDDLE)
put_page(page) /* zhdr is freed! */
but zhdr is still used by caller!

z3fold_map can map freed z3fold page and lead to use-after-free bug. To
fix it, we add PAGE_MIGRATED to indicate z3fold page is migrated and soon
to be released. So get_z3fold_header won't return such page.

Link: https://lkml.kernel.org/r/20220429064051.61552-10-linmiaohe@huawei.com
Fixes: 1f862989b04a ("mm/z3fold.c: support page migration")
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/z3fold: fix z3fold_reclaim_page races with z3fold_free

Think about the below scenario:

CPU1 CPU2
z3fold_reclaim_page z3fold_free
spin_lock(&pool->lock) get_z3fold_header -- hold page_lock
kref_get_unless_zero
kref_put--zhdr->refcount can be 1 now
!z3fold_page_trylock
kref_put -- zhdr->refcount is 0 now
release_z3fold_page
WARN_ON(!list_empty(&zhdr->buddy)); -- we're on buddy now!
spin_lock(&pool->lock); -- deadlock here!

z3fold_reclaim_page might race with z3fold_free and will lead to pool lock
deadlock and zhdr buddy non-empty warning. To fix this, defer getting the
refcount until page_lock is held just like what __z3fold_alloc does. Note
this has the side effect that we won't break the reclaim if we meet a soon
to be released z3fold page now.

Link: https://lkml.kernel.org/r/20220429064051.61552-9-linmiaohe@huawei.com
Fixes: dcf5aedb24f8 ("z3fold: stricter locking and more careful reclaim")
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/z3fold: always clear PAGE_CLAIMED under z3fold page lock

Think about the below race window:

CPU1 CPU2
z3fold_reclaim_page z3fold_free
test_and_set_bit PAGE_CLAIMED
failed to reclaim page
z3fold_page_lock(zhdr);
add back to the lru list;
z3fold_page_unlock(zhdr);
get_z3fold_header
page_claimed=test_and_set_bit PAGE_CLAIMED

clear_bit(PAGE_CLAIMED, &page->private);

if (!page_claimed) /* it's false true */
free_handle is not called

free_handle won't be called in this case. So z3fold_buddy_slots will leak.
Fix it by always clear PAGE_CLAIMED under z3fold page lock.

Link: https://lkml.kernel.org/r/20220429064051.61552-8-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/z3fold: put z3fold page back into unbuddied list when reclaim or migration fails

When doing z3fold page reclaim or migration, the page is removed from
unbuddied list. If reclaim or migration succeeds, it's fine as page is
released. But in case it fails, the page is not put back into unbuddied
list now. The page will be leaked until next compaction work, reclaim or
migration is done.

Link: https://lkml.kernel.org/r/20220429064051.61552-7-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

revert "mm/z3fold.c: allow __GFP_HIGHMEM in z3fold_alloc"

Revert commit f1549cb5ab2b ("mm/z3fold.c: allow __GFP_HIGHMEM in
z3fold_alloc").

z3fold can't support GFP_HIGHMEM page now. page_address is used directly
at all places. Moreover, z3fold_header is on per cpu unbuddied list which
could be accessed anytime. So we should remove the support of GFP_HIGHMEM
allocation for z3fold.

Link: https://lkml.kernel.org/r/20220429064051.61552-6-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/z3fold: throw warning on failure of trylock_page in z3fold_alloc

If trylock_page fails, the page won't be non-lru movable page. When this
page is freed via free_z3fold_page, it will trigger bug on PageMovable
check in __ClearPageMovable. Throw warning on failure of trylock_page to
guard against such rare case just as what zsmalloc does.

Link: https://lkml.kernel.org/r/20220429064051.61552-5-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/z3fold: remove buggy use of stale list for allocation

Currently if z3fold couldn't find an unbuddied page it would first try to
pull a page off the stale list. But this approach is problematic. If
init z3fold page fails later, the page should be freed via
free_z3fold_page to clean up the relevant resource instead of using
__free_page directly. And if page is successfully reused, it will BUG_ON
later in __SetPageMovable because it's already non-lru movable page, i.e.
PAGE_MAPPING_MOVABLE is already set in page->mapping. In order to fix all
of these issues, we can simply remove the buggy use of stale list for
allocation because can_sleep should always be false and we never really
hit the reusing code path now.

Link: https://lkml.kernel.org/r/20220429064051.61552-4-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/z3fold: fix possible null pointer dereferencing

alloc_slots could fail to allocate memory under heavy memory pressure. So
we should check zhdr->slots against NULL to avoid future null pointer
dereferencing.

Link: https://lkml.kernel.org/r/20220429064051.61552-3-linmiaohe@huawei.com
Fixes: fc5488651c7d ("z3fold: simplify freeing slots")
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/z3fold: fix sheduling while atomic

Patch series "A few fixup patches for z3fold".

This series contains a few fixup patches to fix sheduling while atomic,
fix possible null pointer dereferencing, fix various race conditions and
so on. More details can be found in the respective changelogs.


This patch (of 9):

z3fold's page_lock is always held when calling alloc_slots. So gfp should
be GFP_ATOMIC to avoid "scheduling while atomic" bug.

Link: https://lkml.kernel.org/r/20220429064051.61552-1-linmiaohe@huawei.com
Link: https://lkml.kernel.org/r/20220429064051.61552-2-linmiaohe@huawei.com
Fixes: fc5488651c7d ("z3fold: simplify freeing slots")
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/z3fold: remove unneeded PAGE_HEADLESS check in free_handle()

The only caller z3fold_free() never calls free_handle() in PAGE_HEADLESS
case. Remove this unneeded check.

Link: https://lkml.kernel.org/r/20220308134311.59086-9-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/z3fold: remove redundant list_del_init of zhdr->buddy in z3fold_free

do_compact_page() will do list_del_init(&zhdr->buddy) for us. Remove this
extra one to save some possible cpu cycles.

Link: https://lkml.kernel.org/r/20220308134311.59086-8-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/z3fold: move decrement of pool->pages_nr into __release_z3fold_page()

The z3fold will always do atomic64_dec(&pool->pages_nr) when the
__release_z3fold_page() is called. Thus we can move decrement of
pool->pages_nr into __release_z3fold_page() to simplify the code.

Also we can reduce the size of z3fold.o ~1k.

Without this patch:
text data bss dec hex filename
15444 1376 8 16828 41bc mm/z3fold.o
With this patch:
text data bss dec hex filename
15044 1248 8 16300 3fac mm/z3fold.o

Link: https://lkml.kernel.org/r/20220308134311.59086-7-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/z3fold: remove confusing local variable l reassignment

The local variable l holds the address of unbuddied[i] which won't change
after we take the pool lock. Remove it to avoid confusion.

Link: https://lkml.kernel.org/r/20220308134311.59086-6-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/z3fold: remove unneeded page_mapcount_reset and ClearPagePrivate

Page->page_type and PagePrivate are not used in z3fold. We should remove
these confusing unneeded operations. The z3fold do these here is due to
referring to zsmalloc's migration code which does need these operations.

Link: https://lkml.kernel.org/r/20220308134311.59086-5-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/z3fold: minor clean up for z3fold_free

Use put_z3fold_header() to pair with get_z3fold_header. Also fix the
wrong comments. Minor readability improvement.

Link: https://lkml.kernel.org/r/20220308134311.59086-4-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/z3fold: remove obsolete comment in z3fold_alloc

The highmem pages are supported since commit f1549cb5ab2b ("mm/z3fold.c:
allow __GFP_HIGHMEM in z3fold_alloc"). Remove the residual comment.

Link: https://lkml.kernel.org/r/20220308134311.59086-3-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/z3fold: declare z3fold_mount with __init

Patch series "A few cleanup patches for z3fold", v2.

This series contains a few patches to simplify the code, remove unneeded
code, fix obsolete comment and so on. More details can be found in the
respective changelogs.


This patch (of 8):

z3fold_mount is only called during init. So we should declare it with
__init.

Link: https://lkml.kernel.org/r/20220308134311.59086-1-linmiaohe@huawei.com
Link: https://lkml.kernel.org/r/20220308134311.59086-2-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/z3fold: add kerneldoc fields for z3fold_pool

make W=1 generates the following warning for z3fold_pool

mm/z3fold.c:171: warning: Function parameter or member 'zpool' not described in 'z3fold_pool'
mm/z3fold.c:171: warning: Function parameter or member 'zpool_ops' not described in 'z3fold_pool'

Commit 9a001fc19ccc ("z3fold: the 3-fold allocator for compressed pages")
simply did not document the fields at the time. Add rudimentary
documentation.

Link: https://lkml.kernel.org/r/20210520084809.8576-11-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Reviewed-by: Yang Shi <shy828301@gmail.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/z3fold: use release_z3fold_page_locked() to release locked z3fold page

We should use release_z3fold_page_locked() to release z3fold page when
it's locked, although it looks harmless to use release_z3fold_page() now.

Link: https://lkml.kernel.org/r/20210619093151.1492174-7-linmiaohe@huawei.com
Fixes: dcf5aedb24f8 ("z3fold: stricter locking and more careful reclaim")
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Vitaly Wool <vitaly.wool@konsulko.com>
Cc: Hillf Danton <hdanton@sina.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/z3fold: fix potential memory leak in z3fold_destroy_pool()

There is a memory leak in z3fold_destroy_pool() as it forgets to
free_percpu pool->unbuddied. Call free_percpu for pool->unbuddied to fix
this issue.

Link: https://lkml.kernel.org/r/20210619093151.1492174-6-linmiaohe@huawei.com
Fixes: d30561c56f41 ("z3fold: use per-cpu unbuddied lists")
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Vitaly Wool <vitaly.wool@konsulko.com>
Cc: Hillf Danton <hdanton@sina.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/z3fold: remove unused function handle_to_z3fold_header()

handle_to_z3fold_header() is unused now. So we can remove it. As a
result, get_z3fold_header() becomes the only caller of
__get_z3fold_header() and the argument lock is always true. Therefore we
could further fold the __get_z3fold_header() into get_z3fold_header() with
lock = true.

Link: https://lkml.kernel.org/r/20210619093151.1492174-5-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Vitaly Wool <vitaly.wool@konsulko.com>
Cc: Hillf Danton <hdanton@sina.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/z3fold: remove magic number in z3fold_create_pool()

It's meaningless to pass a magic number 2 to __alloc_percpu() as there is
a minimum alignment size of PCPU_MIN_ALLOC_SIZE (> 2) in it. Also there
is no special alignment requirement for unbuddied. So we could replace
this magic number with nature alignment, i.e. __alignof__(struct
list_head), to improve readability.

Link: https://lkml.kernel.org/r/20210619093151.1492174-4-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Vitaly Wool <vitaly.wool@konsulko.com>
Cc: Hillf Danton <hdanton@sina.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/z3fold: avoid possible underflow in z3fold_alloc()

It is not enough to just make sure the z3fold header is not larger than
the page size. When z3fold header is equal to PAGE_SIZE, we would
underflow when check alloc size against PAGE_SIZE - ZHDR_SIZE_ALIGNED -
CHUNK_SIZE in z3fold_alloc(). Make sure there has remaining spaces for
its buddy to fix this theoretical issue.

Link: https://lkml.kernel.org/r/20210619093151.1492174-3-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Vitaly Wool <vitaly.wool@konsulko.com>
Cc: Hillf Danton <hdanton@sina.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/z3fold: define macro NCHUNKS as TOTAL_CHUNKS - ZHDR_CHUNKS

Patch series "Cleanup and fixup for z3fold".

This series contains cleanups to remove unused function, redefine macro to
improve readability and so on. Also this fixes several bugs in z3fold,
such as memory leak in z3fold_destroy_pool(). More details can be found
in the respective changelogs.

This patch (of 6):

To improve code readability, we could define macro NCHUNKS as TOTAL_CHUNKS
- ZHDR_CHUNKS. No functional change intended.

Link: https://lkml.kernel.org/r/20210619093151.1492174-1-linmiaohe@huawei.com
Link: https://lkml.kernel.org/r/20210619093151.1492174-2-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Vitaly Wool <vitaly.wool@konsulko.com>
Cc: Hillf Danton <hdanton@sina.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: fix some typos and code style problems

fix some typos and code style problems in mm.

gfp.h: s/MAXNODES/MAX_NUMNODES
mmzone.h: s/then/than
rmap.c: s/__vma_split()/__vma_adjust()
swap.c: s/__mod_zone_page_stat/__mod_zone_page_state, s/is is/is
swap_state.c: s/whoes/whose
z3fold.c: code style problem fix in z3fold_unregister_migration
zsmalloc.c: s/of/or, s/give/given

Link: https://lkml.kernel.org/r/20210419083057.64820-1-luoshijie1@huawei.com
Signed-off-by: Shijie Luo <luoshijie1@huawei.com>
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

z3fold: prevent reclaim/free race for headless pages

Commit ca0246bb97c2 ("z3fold: fix possible reclaim races") introduced
the PAGE_CLAIMED flag "to avoid racing on a z3fold 'headless' page
release." By atomically testing and setting the bit in each of
z3fold_free() and z3fold_reclaim_page(), a double-free was avoided.

However, commit dcf5aedb24f8 ("z3fold: stricter locking and more careful
reclaim") appears to have unintentionally broken this behavior by moving
the PAGE_CLAIMED check in z3fold_reclaim_page() to after the page lock
gets taken, which only happens for non-headless pages. For headless
pages, the check is now skipped entirely and races can occur again.

I have observed such a race on my system:

page:00000000ffbd76b7 refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x165316
flags: 0x2ffff0000000000()
raw: 02ffff0000000000 ffffea0004535f48 ffff8881d553a170 0000000000000000
raw: 0000000000000000 0000000000000011 00000000ffffffff 0000000000000000
page dumped because: VM_BUG_ON_PAGE(page_ref_count(page) == 0)
------------[ cut here ]------------
kernel BUG at include/linux/mm.h:707!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN PTI
CPU: 2 PID: 291928 Comm: kworker/2:0 Tainted: G B 5.10.7-arch1-1-kasan #1
Hardware name: Gigabyte Technology Co., Ltd. H97N-WIFI/H97N-WIFI, BIOS F9b 03/03/2016
Workqueue: zswap-shrink shrink_worker
RIP: 0010:__free_pages+0x10a/0x130
Code: c1 e7 06 48 01 ef 45 85 e4 74 d1 44 89 e6 31 d2 41 83 ec 01 e8 e7 b0 ff ff eb da 48 c7 c6 e0 32 91 88 48 89 ef e8 a6 89 f8 ff <0f> 0b 4c 89 e7 e8 fc 79 07 00 e9 33 ff ff ff 48 89 ef e8 ff 79 07
RSP: 0000:ffff88819a2ffb98 EFLAGS: 00010296
RAX: 0000000000000000 RBX: ffffea000594c5a8 RCX: 0000000000000000
RDX: 1ffffd4000b298b7 RSI: 0000000000000000 RDI: ffffea000594c5b8
RBP: ffffea000594c580 R08: 000000000000003e R09: ffff8881d5520bbb
R10: ffffed103aaa4177 R11: 0000000000000001 R12: ffffea000594c5b4
R13: 0000000000000000 R14: ffff888165316000 R15: ffffea000594c588
FS: 0000000000000000(0000) GS:ffff8881d5500000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f7c8c3654d8 CR3: 0000000103f42004 CR4: 00000000001706e0
Call Trace:
z3fold_zpool_shrink+0x9b6/0x1240
shrink_worker+0x35/0x90
process_one_work+0x70c/0x1210
worker_thread+0x539/0x1200
kthread+0x330/0x400
ret_from_fork+0x22/0x30
Modules linked in: rfcomm ebtable_filter ebtables ip6table_filter ip6_tables iptable_filter ccm algif_aead des_generic libdes ecb algif_skcipher cmac bnep md4 algif_hash af_alg vfat fat intel_rapl_msr intel_rapl_common x86_pkg_temp_thermal intel_powerclamp coretemp kvm_intel iwlmvm hid_logitech_hidpp kvm at24 mac80211 snd_hda_codec_realtek iTCO_wdt snd_hda_codec_generic intel_pmc_bxt snd_hda_codec_hdmi ledtrig_audio iTCO_vendor_support mei_wdt mei_hdcp snd_hda_intel snd_intel_dspcfg libarc4 soundwire_intel irqbypass iwlwifi soundwire_generic_allocation rapl soundwire_cadence intel_cstate snd_hda_codec intel_uncore btusb joydev mousedev snd_usb_audio pcspkr btrtl uvcvideo nouveau btbcm i2c_i801 btintel snd_hda_core videobuf2_vmalloc i2c_smbus snd_usbmidi_lib videobuf2_memops bluetooth snd_hwdep soundwire_bus snd_soc_rt5640 videobuf2_v4l2 cfg80211 snd_soc_rl6231 videobuf2_common snd_rawmidi lpc_ich alx videodev mdio snd_seq_device snd_soc_core mc ecdh_generic mxm_wmi mei_me
hid_logitech_dj wmi snd_compress e1000e ac97_bus mei ttm rfkill snd_pcm_dmaengine ecc snd_pcm snd_timer snd soundcore mac_hid acpi_pad pkcs8_key_parser it87 hwmon_vid crypto_user fuse ip_tables x_tables ext4 crc32c_generic crc16 mbcache jbd2 dm_crypt cbc encrypted_keys trusted tpm rng_core usbhid dm_mod crct10dif_pclmul crc32_pclmul crc32c_intel ghash_clmulni_intel aesni_intel crypto_simd cryptd glue_helper xhci_pci xhci_pci_renesas i915 video intel_gtt i2c_algo_bit drm_kms_helper syscopyarea sysfillrect sysimgblt fb_sys_fops cec drm agpgart
---[ end trace 126d646fc3dc0ad8 ]---

To fix the issue, re-add the earlier test and set in the case where we
have a headless page.

Link: https://lkml.kernel.org/r/c8106dbe6d8390b290cd1d7f873a2942e805349e.1615452048.git.tommyhebb@gmail.com
Fixes: dcf5aedb24f8 ("z3fold: stricter locking and more careful reclaim")
Signed-off-by: Thomas Hebb <tommyhebb@gmail.com>
Reviewed-by: Vitaly Wool <vitaly.wool@konsulko.com>
Cc: Jongseok Kim <ks77sj@gmail.com>
Cc: Snild Dolkow <snild@sony.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: set the sleep_mapped to true for zbud and z3fold

zpool driver adds a flag to indicate whether the zpool driver can enter an
atomic context after mapping. This patch sets it true for z3fold and
zbud.

Link: https://lkml.kernel.org/r/1611035683-12732-3-git-send-email-tiantao6@hisilicon.com
Signed-off-by: Tian Tao <tiantao6@hisilicon.com>
Reviewed-by: Vitaly Wool <vitaly.wool@konsulko.com>
Acked-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Reported-by: Mike Galbraith <efault@gmx.de>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Barry Song <song.bao.hua@hisilicon.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

z3fold: simplify the zhdr initialization code in init_z3fold_page()

We can simplify the zhdr initialization by memset() the zhdr first
instead of set struct member to zero one by one. This would also make
code more compact and clear.

Link: https://lkml.kernel.org/r/20210120085851.16159-1-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

z3fold: remove unused attribute for release_z3fold_page

Since commit dcf5aedb24f8 ("z3fold: stricter locking and more careful
reclaim"), release_z3fold_page() is used again. So we can drop the
unused attribute safely.

Link: https://lkml.kernel.org/r/20210120084008.58432-1-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

z3fold: remove preempt disabled sections for RT

Replace get_cpu_ptr() with migrate_disable()+this_cpu_ptr() so RT can take
spinlocks that become sleeping locks.

Signed-off-by Mike Galbraith <efault@gmx.de>

Link: https://lkml.kernel.org/r/20201209145151.18994-3-vitaly.wool@konsulko.com
Signed-off-by: Vitaly Wool <vitaly.wool@konsulko.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

z3fold: stricter locking and more careful reclaim

Use temporary slots in reclaim function to avoid possible race when
freeing those.

While at it, make sure we check CLAIMED flag under page lock in the
reclaim function to make sure we are not racing with z3fold_alloc().

Link: https://lkml.kernel.org/r/20201209145151.18994-4-vitaly.wool@konsulko.com
Signed-off-by: Vitaly Wool <vitaly.wool@konsulko.com>
Cc: <stable@vger.kernel.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

z3fold: simplify freeing slots

Patch series "z3fold: stability / rt fixes".

Address z3fold stability issues under stress load, primarily in the
reclaim and free aspects. Besides, it fixes the locking problems that
were only seen in real-time kernel configuration.

This patch (of 3):

There used to be two places in the code where slots could be freed, namely
when freeing the last allocated handle from the slots and when releasing
the z3fold header these slots aree linked to. The logic to decide on
whether to free certain slots was complicated and error prone in both
functions and it led to failures in RT case.

To fix that, make free_handle() the single point of freeing slots.

Link: https://lkml.kernel.org/r/20201209145151.18994-1-vitaly.wool@konsulko.com
Link: https://lkml.kernel.org/r/20201209145151.18994-2-vitaly.wool@konsulko.com
Signed-off-by: Vitaly Wool <vitaly.wool@konsulko.com>
Tested-by: Mike Galbraith <efault@gmx.de>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/z3fold.c: use xx_zalloc instead xx_alloc and memset

alloc_slots() allocates memory for slots using kmem_cache_alloc(), then
memsets it. We can just use kmem_cache_zalloc().

Signed-off-by: Hui Su <sh_def@163.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Link: https://lkml.kernel.org/r/20200926100834.GA184671@rlk
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/z3fold: silence kmemleak false positives of slots

Kmemleak reported many leaks while under memory pressue in,

slots = alloc_slots(pool, gfp);

which is referenced by "zhdr" in init_z3fold_page(),

zhdr->slots = slots;

However, "zhdr" could be gone without freeing slots as the later will be
freed separately when the last "handle" off of "handles" array is freed.
It will be within "slots" which is always aligned.

unreferenced object 0xc000000fdadc1040 (size 104):
comm "oom04", pid 140476, jiffies 4295359280 (age 3454.970s)
hex dump (first 32 bytes):
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
backtrace:
z3fold_zpool_malloc+0x7b0/0xe10
alloc_slots at mm/z3fold.c:214
(inlined by) init_z3fold_page at mm/z3fold.c:412
(inlined by) z3fold_alloc at mm/z3fold.c:1161
(inlined by) z3fold_zpool_malloc at mm/z3fold.c:1735
zpool_malloc+0x34/0x50
zswap_frontswap_store+0x60c/0xda0
zswap_frontswap_store at mm/zswap.c:1093
__frontswap_store+0x128/0x330
swap_writepage+0x58/0x110
pageout+0x16c/0xa40
shrink_page_list+0x1ac8/0x25c0
shrink_inactive_list+0x270/0x730
shrink_lruvec+0x444/0xf30
shrink_node+0x2a4/0x9c0
do_try_to_free_pages+0x158/0x640
try_to_free_pages+0x1bc/0x5f0
__alloc_pages_slowpath.constprop.60+0x4dc/0x15a0
__alloc_pages_nodemask+0x520/0x650
alloc_pages_vma+0xc0/0x420
handle_mm_fault+0x1174/0x1bf0

Signed-off-by: Qian Cai <cai@lca.pw>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Vitaly Wool <vitaly.wool@konsulko.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Link: http://lkml.kernel.org/r/20200522220052.2225-1-cai@lca.pw
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

z3fold: fix use-after-free when freeing handles

free_handle() for a foreign handle may race with inter-page compaction,
what can lead to memory corruption.

To avoid that, take write lock not read lock in free_handle to be
synchronized with __release_z3fold_page().

For example KASAN can detect it:

==================================================================
BUG: KASAN: use-after-free in LZ4_decompress_safe+0x2c4/0x3b8
Read of size 1 at addr ffffffc976695ca3 by task GoogleApiHandle/4121

CPU: 0 PID: 4121 Comm: GoogleApiHandle Tainted: P S OE 4.19.81-perf+ #162
Hardware name: Sony Mobile Communications. PDX-203(KONA) (DT)
Call trace:
LZ4_decompress_safe+0x2c4/0x3b8
lz4_decompress_crypto+0x3c/0x70
crypto_decompress+0x58/0x70
zcomp_decompress+0xd4/0x120
...

Apart from that, initialize zhdr->mapped_count in init_z3fold_page() and
remove "newpage" variable because it is not used anywhere.

Signed-off-by: Uladzislau Rezki <uladzislau.rezki@sony.com>
Signed-off-by: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Qian Cai <cai@lca.pw>
Cc: Raymond Jennings <shentino@gmail.com>
Cc: <stable@vger.kernel.org>
Link: http://lkml.kernel.org/r/20200520082100.28876-1-vitaly.wool@konsulko.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/z3fold.c: do not include rwlock.h directly

rwlock.h should not be included directly. Instead linux/splinlock.h
should be included. One thing it does is to break the RT build.

Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20200224133631.1510569-1-bigeasy@linutronix.de
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/z3fold.c: add inter-page compaction

For each page scheduled for compaction (e. g. by z3fold_free()), try to
apply inter-page compaction before running the traditional/ existing
intra-page compaction. That means, if the page has only one buddy, we
treat that buddy as a new object that we aim to place into an existing
z3fold page. If such a page is found, that object is transferred and the
old page is freed completely. The transferred object is named "foreign"
and treated slightly differently thereafter.

Namely, we increase "foreign handle" counter for the new page. Pages with
non-zero "foreign handle" count become unmovable. This patch implements
"foreign handle" detection when a handle is freed to decrement the foreign
handle counter accordingly, so a page may as well become movable again as
the time goes by.

As a result, we almost always have exactly 3 objects per page and
significantly better average compression ratio.

[cai@lca.pw: fix -Wunused-but-set-variable warnings]
Link: http://lkml.kernel.org/r/1570542062-29144-1-git-send-email-cai@lca.pw
[vitalywool@gmail.com: avoid subtle race when freeing slots]
Link: http://lkml.kernel.org/r/20191127152118.6314b99074b0626d4c5a8835@gmail.com
[vitalywool@gmail.com: compact objects more accurately]
Link: http://lkml.kernel.org/r/20191127152216.6ad33745a21ba71c53606acb@gmail.com
[vitalywool@gmail.com: protect handle reads]
Link: http://lkml.kernel.org/r/20191127152345.8059852f60947686674d726d@gmail.com
Link: http://lkml.kernel.org/r/20191006041457.24113-1-vitalywool@gmail.com
Signed-off-by: Vitaly Wool <vitaly.vul@sony.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Henry Burns <henrywolfeburns@gmail.com>
Cc: Shakeel Butt <shakeelb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/z3fold.c: claim page in the beginning of free

There's a really hard to reproduce race in z3fold between z3fold_free()
and z3fold_reclaim_page(). z3fold_reclaim_page() can claim the page
after z3fold_free() has checked if the page was claimed and
z3fold_free() will then schedule this page for compaction which may in
turn lead to random page faults (since that page would have been
reclaimed by then).

Fix that by claiming page in the beginning of z3fold_free() and not
forgetting to clear the claim in the end.

[vitalywool@gmail.com: v2]
Link: http://lkml.kernel.org/r/20190928113456.152742cf@bigdell
Link: http://lkml.kernel.org/r/20190926104844.4f0c6efa1366b8f5741eaba9@gmail.com
Signed-off-by: Vitaly Wool <vitalywool@gmail.com>
Reported-by: Markus Linnala <markus.linnala@gmail.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Henry Burns <henrywolfeburns@gmail.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Markus Linnala <markus.linnala@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

z3fold: fix memory leak in kmem cache

Currently there is a leak in init_z3fold_page() -- it allocates handles
from kmem cache even for headless pages, but then they are never used and
never freed, so eventually kmem cache may get exhausted. This patch
provides a fix for that.

Link: http://lkml.kernel.org/r/20190917185352.44cf285d3ebd9e64548de5de@gmail.com
Signed-off-by: Vitaly Wool <vitalywool@gmail.com>
Reported-by: Markus Linnala <markus.linnala@gmail.com>
Tested-by: Markus Linnala <markus.linnala@gmail.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Henry Burns <henrywolfeburns@gmail.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

z3fold: fix retry mechanism in page reclaim

z3fold_page_reclaim()'s retry mechanism is broken: on a second iteration
it will have zhdr from the first one so that zhdr is no longer in line
with struct page. That leads to crashes when the system is stressed.

Fix that by moving zhdr assignment up.

While at it, protect against using already freed handles by using own
local slots structure in z3fold_page_reclaim().

Link: http://lkml.kernel.org/r/20190908162919.830388dc7404d1e2c80f4095@gmail.com
Signed-off-by: Vitaly Wool <vitalywool@gmail.com>
Reported-by: Markus Linnala <markus.linnala@gmail.com>
Reported-by: Chris Murphy <bugzilla@colorremedies.com>
Reported-by: Agustin Dall'Alba <agustin@dallalba.com.ar>
Cc: "Maciej S. Szmigiero" <mail@maciej.szmigiero.name>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Henry Burns <henrywolfeburns@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Revert "mm/z3fold.c: fix race between migration and destruction"

With the original commit applied, z3fold_zpool_destroy() may get blocked
on wait_event() for indefinite time. Revert this commit for the time
being to get rid of this problem since the issue the original commit
addresses is less severe.

Link: http://lkml.kernel.org/r/20190910123142.7a9c8d2de4d0acbc0977c602@gmail.com
Fixes: d776aaa9895eb6eb77 ("mm/z3fold.c: fix race between migration and destruction")
Reported-by: Agustín Dall'Alba <agustin@dallalba.com.ar>
Signed-off-by: Vitaly Wool <vitalywool@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Vitaly Wool <vitalywool@gmail.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Jonathan Adams <jwadams@google.com>
Cc: Henry Burns <henrywolfeburns@gmail.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/z3fold.c: fix lock/unlock imbalance in z3fold_page_isolate

Fix lock/unlock imbalance by unlocking *zhdr* before return.

Addresses Coverity ID 1452811 ("Missing unlock")

Link: http://lkml.kernel.org/r/20190826030634.GA4379@embeddedor
Fixes: d776aaa9895e ("mm/z3fold.c: fix race between migration and destruction")
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Henry Burns <henrywolfeburns@gmail.com>
Cc: Vitaly Wool <vitalywool@gmail.com>
Cc: Shakeel Butt <shakeelb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/z3fold.c: fix race between migration and destruction

In z3fold_destroy_pool() we call destroy_workqueue(&pool->compact_wq).
However, we have no guarantee that migration isn't happening in the
background at that time.

Migration directly calls queue_work_on(pool->compact_wq), if destruction
wins that race we are using a destroyed workqueue.

Link: http://lkml.kernel.org/r/20190809213828.202833-1-henryburns@google.com
Signed-off-by: Henry Burns <henryburns@google.com>
Cc: Vitaly Wool <vitalywool@gmail.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Jonathan Adams <jwadams@google.com>
Cc: Henry Burns <henrywolfeburns@gmail.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/z3fold.c: fix z3fold_destroy_pool() race condition

The constraint from the zpool use of z3fold_destroy_pool() is there are
no outstanding handles to memory (so no active allocations), but it is
possible for there to be outstanding work on either of the two wqs in
the pool.

Calling z3fold_deregister_migration() before the workqueues are drained
means that there can be allocated pages referencing a freed inode,
causing any thread in compaction to be able to trip over the bad pointer
in PageMovable().

Link: http://lkml.kernel.org/r/20190726224810.79660-2-henryburns@google.com
Fixes: 1f862989b04a ("mm/z3fold.c: support page migration")
Signed-off-by: Henry Burns <henryburns@google.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Reviewed-by: Jonathan Adams <jwadams@google.com>
Cc: Vitaly Vul <vitaly.vul@sony.com>
Cc: Vitaly Wool <vitalywool@gmail.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Henry Burns <henrywolfeburns@gmail.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/z3fold.c: fix z3fold_destroy_pool() ordering

The constraint from the zpool use of z3fold_destroy_pool() is there are
no outstanding handles to memory (so no active allocations), but it is
possible for there to be outstanding work on either of the two wqs in
the pool.

If there is work queued on pool->compact_workqueue when it is called,
z3fold_destroy_pool() will do:

z3fold_destroy_pool()
destroy_workqueue(pool->release_wq)
destroy_workqueue(pool->compact_wq)
drain_workqueue(pool->compact_wq)
do_compact_page(zhdr)
kref_put(&zhdr->refcount)
__release_z3fold_page(zhdr, ...)
queue_work_on(pool->release_wq, &pool->work) *BOOM*

So compact_wq needs to be destroyed before release_wq.

Link: http://lkml.kernel.org/r/20190726224810.79660-1-henryburns@google.com
Fixes: 5d03a6613957 ("mm/z3fold.c: use kref to prevent page free/compact race")
Signed-off-by: Henry Burns <henryburns@google.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Reviewed-by: Jonathan Adams <jwadams@google.com>
Cc: Vitaly Vul <vitaly.vul@sony.com>
Cc: Vitaly Wool <vitalywool@gmail.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Al Viro <viro@zeniv.linux.org.uk
Cc: Henry Burns <henrywolfeburns@gmail.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/z3fold.c: reinitialize zhdr structs after migration

z3fold_page_migration() calls memcpy(new_zhdr, zhdr, PAGE_SIZE).
However, zhdr contains fields that can't be directly coppied over (ex:
list_head, a circular linked list). We only need to initialize the
linked lists in new_zhdr, as z3fold_isolate_page() already ensures that
these lists are empty

Additionally it is possible that zhdr->work has been placed in a
workqueue. In this case we shouldn't migrate the page, as zhdr->work
references zhdr as opposed to new_zhdr.

Link: http://lkml.kernel.org/r/20190716000520.230595-1-henryburns@google.com
Fixes: 1f862989b04ade61d3 ("mm/z3fold.c: support page migration")
Signed-off-by: Henry Burns <henryburns@google.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Cc: Vitaly Vul <vitaly.vul@sony.com>
Cc: Vitaly Wool <vitalywool@gmail.com>
Cc: Jonathan Adams <jwadams@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/z3fold.c: remove z3fold_migration trylock

z3fold_page_migrate() will never succeed because it attempts to acquire
a lock that has already been taken by migrate.c in __unmap_and_move().

__unmap_and_move() migrate.c
trylock_page(oldpage)
move_to_new_page(oldpage_newpage)
a_ops->migrate_page(oldpage, newpage)
z3fold_page_migrate(oldpage, newpage)
trylock_page(oldpage)

Link: http://lkml.kernel.org/r/20190710213238.91835-1-henryburns@google.com
Fixes: 1f862989b04a ("mm/z3fold.c: support page migration")
Signed-off-by: Henry Burns <henryburns@google.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Cc: Vitaly Wool <vitalywool@gmail.com>
Cc: Vitaly Vul <vitaly.vul@sony.com>
Cc: Jonathan Adams <jwadams@google.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Snild Dolkow <snild@sony.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/z3fold.c: allow __GFP_HIGHMEM in z3fold_alloc

One of the gfp flags used to show that a page is movable is
__GFP_HIGHMEM. Currently z3fold_alloc() fails when __GFP_HIGHMEM is
passed. Now that z3fold pages are movable, we allow __GFP_HIGHMEM. We
strip the movability related flags from the call to kmem_cache_alloc()
for our slots since it is a kernel allocation.

[akpm@linux-foundation.org: coding-style fixes]
Link: http://lkml.kernel.org/r/20190712222118.108192-1-henryburns@google.com
Signed-off-by: Henry Burns <henryburns@google.com>
Acked-by: Vitaly Wool <vitalywool@gmail.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/z3fold: don't try to use buddy slots after free

As reported by Henry Burns:

Running z3fold stress testing with address sanitization showed zhdr->slots
was being used after it was freed.

z3fold_free(z3fold_pool, handle)
free_handle(handle)
kmem_cache_free(pool->c_handle, zhdr->slots)
release_z3fold_page_locked_list(kref)
__release_z3fold_page(zhdr, true)
zhdr_to_pool(zhdr)
slots_to_pool(zhdr->slots) *BOOM*

To fix this, add pointer to the pool back to z3fold_header and modify
zhdr_to_pool to return zhdr->pool.

Link: http://lkml.kernel.org/r/20190708134808.e89f3bfadd9f6ffd7eff9ba9@gmail.com
Fixes: 7c2b8baa61fe ("mm/z3fold.c: add structure for buddy handles")
Signed-off-by: Vitaly Wool <vitalywool@gmail.com>
Reported-by: Henry Burns <henryburns@google.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Cc: Jonathan Adams <jwadams@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/z3fold.c: lock z3fold page before __SetPageMovable()

Following zsmalloc.c's example we call trylock_page() and unlock_page().
Also make z3fold_page_migrate() assert that newpage is passed in locked,
as per the documentation.

[akpm@linux-foundation.org: fix trylock_page return value test, per Shakeel]
Link: http://lkml.kernel.org/r/20190702005122.41036-1-henryburns@google.com
Link: http://lkml.kernel.org/r/20190702233538.52793-1-henryburns@google.com
Signed-off-by: Henry Burns <henryburns@google.com>
Suggested-by: Vitaly Wool <vitalywool@gmail.com>
Acked-by: Vitaly Wool <vitalywool@gmail.com>
Acked-by: David Rientjes <rientjes@google.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Cc: Vitaly Vul <vitaly.vul@sony.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Xidong Wang <wangxidong_97@163.com>
Cc: Jonathan Adams <jwadams@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

z3fold: fix sheduling while atomic

kmem_cache_alloc() may be called from z3fold_alloc() in atomic context, so
we need to pass correct gfp flags to avoid "scheduling while atomic" bug.

Link: http://lkml.kernel.org/r/20190523153245.119dfeed55927e8755250ddd@gmail.com
Fixes: 7c2b8baa61fe5 ("mm/z3fold.c: add structure for buddy handles")
Signed-off-by: Vitaly Wool <vitaly.vul@sony.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

zsfold: Convert zsfold to use the new mount API

Convert the zsfold filesystem to the new internal mount API as the old one
will be obsoleted and removed. This allows greater flexibility in
communication of mount parameters between userspace, the VFS and the
filesystem.

See Documentation/filesystems/mount_api.txt for more information.

Signed-off-by: David Howells <dhowells@redhat.com>

mount_pseudo(): drop 'name' argument, switch to d_make_root()

Once upon a time we used to set ->d_name of e.g. pipefs root
so that d_path() on pipes would work. These days it's
completely pointless - dentries of pipes are not even connected
to pipefs root. However, mount_pseudo() had set the root
dentry name (passed as the second argument) and callers
kept inventing names to pass to it. Including those that
didn't *have* any non-root dentries to start with...

All of that had been pointless for about 8 years now; it's
time to get rid of that cargo-culting...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

treewide: Add SPDX license identifier for more missed files

Add SPDX license identifiers to all files which:

- Have no license information of any form

- Have MODULE_LICENCE("GPL*") inside which was used in the initial
scan/conversion to ignore the file

These files fall under the project license, GPL v2 only. The resulting SPDX
license identifier is:

GPL-2.0-only

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

z3fold: don't bother with dentry_operations

Don't bother with dentry_operations as no dentry is ever allocated.

Signed-off-by: David Howells <dhowells@redhat.com>

mm/z3fold.c: support page migration

Now that we are not using page address in handles directly, we can make
z3fold pages movable to decrease the memory fragmentation z3fold may
create over time.

This patch starts advertising non-headless z3fold pages as movable and
uses the existing kernel infrastructure to implement moving of such pages
per memory management subsystem's request. It thus implements 3 required
callbacks for page migration:

* isolation callback: z3fold_page_isolate(): try to isolate the page by
removing it from all lists. Pages scheduled for some activity and
mapped pages will not be isolated. Return true if isolation was
successful or false otherwise

* migration callback: z3fold_page_migrate(): re-check critical
conditions and migrate page contents to the new page provided by the
memory subsystem. Returns 0 on success or negative error code otherwise

* putback callback: z3fold_page_putback(): put back the page if
z3fold_page_migrate() for it failed permanently (i. e. not with
-EAGAIN code).

[lkp@intel.com: z3fold_page_isolate() can be static]
Link: http://lkml.kernel.org/r/20190419130924.GA161478@ivb42
Link: http://lkml.kernel.org/r/20190417103922.31253da5c366c4ebe0419cfc@gmail.com
Signed-off-by: Vitaly Wool <vitaly.vul@sony.com>
Signed-off-by: kbuild test robot <lkp@intel.com>
Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Cc: Oleksiy Avramchenko <oleksiy.avramchenko@sonymobile.com>
Cc: Uladzislau Rezki <urezki@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/z3fold.c: add structure for buddy handles

For z3fold to be able to move its pages per request of the memory
subsystem, it should not use direct object addresses in handles. Instead,
it will create abstract handles (3 per page) which will contain pointers
to z3fold objects. Thus, it will be possible to change these pointers
when z3fold page is moved.

Link: http://lkml.kernel.org/r/20190417103826.484eaf18c1294d682769880f@gmail.com
Signed-off-by: Vitaly Wool <vitaly.vul@sony.com>
Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Cc: Oleksiy Avramchenko <oleksiy.avramchenko@sonymobile.com>
Cc: Uladzislau Rezki <urezki@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/z3fold.c: improve compression by extending search

The current z3fold implementation only searches this CPU's page lists for
a fitting page to put a new object into. This patch adds quick search for
very well fitting pages (i. e. those having exactly the required number
of free space) on other CPUs too, before allocating a new page for that
object.

Link: http://lkml.kernel.org/r/20190417103733.72ae81abe1552397c95a008e@gmail.com
Signed-off-by: Vitaly Wool <vitaly.vul@sony.com>
Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Cc: Oleksiy Avramchenko <oleksiy.avramchenko@sonymobile.com>
Cc: Uladzislau Rezki <urezki@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/z3fold.c: introduce helper functions

Patch series "z3fold: support page migration", v2.

This patchset implements page migration support and slightly better buddy
search. To implement page migration support, z3fold has to move away from
the current scheme of handle encoding. i. e. stop encoding page address
in handles. Instead, a small per-page structure is created which will
contain actual addresses for z3fold objects, while pointers to fields of
that structure will be used as handles.

Thus, it will be possible to change the underlying addresses to reflect
page migration.

To support migration itself, 3 callbacks will be implemented:

1: isolation callback: z3fold_page_isolate(): try to isolate the page
by removing it from all lists. Pages scheduled for some activity and
mapped pages will not be isolated. Return true if isolation was
successful or false otherwise

2: migration callback: z3fold_page_migrate(): re-check critical
conditions and migrate page contents to the new page provided by the
system. Returns 0 on success or negative error code otherwise

3: putback callback: z3fold_page_putback(): put back the page if
z3fold_page_migrate() for it failed permanently (i. e. not with
-EAGAIN code).

To make sure an isolated page doesn't get freed, its kref is incremented
in z3fold_page_isolate() and decremented during post-migration compaction,
if migration was successful, or by z3fold_page_putback() in the other
case.

Since the new handle encoding scheme implies slight memory consumption
increase, better buddy search (which decreases memory consumption) is
included in this patchset.

This patch (of 4):

Introduce a separate helper function for object allocation, as well as 2
smaller helpers to add a buddy to the list and to get a pointer to the
pool from the z3fold header. No functional changes here.

Link: http://lkml.kernel.org/r/20190417103633.a4bb770b5bf0fb7e43ce1666@gmail.com
Signed-off-by: Vitaly Wool <vitaly.vul@sony.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Cc: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Cc: Oleksiy Avramchenko <oleksiy.avramchenko@sonymobile.com>
Cc: Uladzislau Rezki <urezki@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

z3fold: fix possible reclaim races

Reclaim and free can race on an object which is basically fine but in
order for reclaim to be able to map "freed" object we need to encode
object length in the handle. handle_to_chunks() is then introduced to
extract object length from a handle and use it during mapping.

Moreover, to avoid racing on a z3fold "headless" page release, we should
not try to free that page in z3fold_free() if the reclaim bit is set.
Also, in the unlikely case of trying to reclaim a page being freed, we
should not proceed with that page.

While at it, fix the page accounting in reclaim function.

This patch supersedes "[PATCH] z3fold: fix reclaim lock-ups".

Link: http://lkml.kernel.org/r/20181105162225.74e8837d03583a9b707cf559@gmail.com
Signed-off-by: Vitaly Wool <vitaly.vul@sony.com>
Signed-off-by: Jongseok Kim <ks77sj@gmail.com>
Reported-by-by: Jongseok Kim <ks77sj@gmail.com>
Reviewed-by: Snild Dolkow <snild@sony.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

z3fold: fix reclaim lock-ups

Do not try to optimize in-page object layout while the page is under
reclaim. This fixes lock-ups on reclaim and improves reclaim
performance at the same time.

[akpm@linux-foundation.org: coding-style fixes]
Link: http://lkml.kernel.org/r/20180430125800.444cae9706489f412ad12621@gmail.com
Signed-off-by: Vitaly Wool <vitaly.vul@sony.com>
Reported-by: Guenter Roeck <linux@roeck-us.net>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Cc: <Oleksiy.Avramchenko@sony.com>
Cc: Matthew Wilcox <mawilcox@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/z3fold.c: use gfpflags_allow_blocking

We have a perfectly good macro to determine whether the gfp flags allow
you to sleep or not; use it instead of trying to infer it.

Link: http://lkml.kernel.org/r/20180408062206.GC16007@bombadil.infradead.org
Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Vitaly Wool <vitalywool@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

z3fold: fix memory leak

In z3fold_create_pool(), the memory allocated by __alloc_percpu() is not
released on the error path that pool->compact_wq , which holds the
return value of create_singlethread_workqueue(), is NULL. This will
result in a memory leak bug.

[akpm@linux-foundation.org: fix oops on kzalloc() failure, check __alloc_percpu() retval]
Link: http://lkml.kernel.org/r/1522803111-29209-1-git-send-email-wangxidong_97@163.com
Signed-off-by: Xidong Wang <wangxidong_97@163.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Vitaly Wool <vitalywool@gmail.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

z3fold: limit use of stale list for allocation

Currently if z3fold couldn't find an unbuddied page it would first try
to pull a page off the stale list. The problem with this approach is
that we can't 100% guarantee that the page is not processed by the
workqueue thread at the same time unless we run cancel_work_sync() on
it, which we can't do if we're in an atomic context. So let's just
limit stale list usage to non-atomic contexts only.

Link: http://lkml.kernel.org/r/47ab51e7-e9c1-d30e-ab17-f734dbc3abce@gmail.com
Signed-off-by: Vitaly Vul <vitaly.vul@sony.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: <Oleksiy.Avramchenko@sony.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: docs: fix parameter names mismatch

There are several places where parameter descriptions do no match the
actual code. Fix it.

Link: http://lkml.kernel.org/r/1516700871-22279-3-git-send-email-rppt@linux.vnet.ibm.com
Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/z3fold.c: use kref to prevent page free/compact race

There is a race in the current z3fold implementation between
do_compact() called in a work queue context and the page release
procedure when page's kref goes to 0.

do_compact() may be waiting for page lock, which is released by
release_z3fold_page_locked right before putting the page onto the
"stale" list, and then the page may be freed as do_compact() modifies
its contents.

The mechanism currently implemented to handle that (checking the
PAGE_STALE flag) is not reliable enough. Instead, we'll use page's kref
counter to guarantee that the page is not released if its compaction is
scheduled. It then becomes compaction function's responsibility to
decrease the counter and quit immediately if the page was actually
freed.

Link: http://lkml.kernel.org/r/20171117092032.00ea56f42affbed19f4fcc6c@gmail.com
Signed-off-by: Vitaly Wool <vitaly.wool@sonymobile.com>
Cc: <Oleksiy.Avramchenko@sony.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

z3fold: fix stale list handling

Fix the situation when clear_bit() is called for page->private before
the page pointer is actually assigned. While at it, remove work_busy()
check because it is costly and does not give 100% guarantee anyway.

Signed-off-by: Vitaly Wool <vitalywool@gmail.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: <Oleksiy.Avramchenko@sony.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

z3fold: fix potential race in z3fold_reclaim_page

It is possible that on a (partially) unsuccessful page reclaim,
kref_put() called in z3fold_reclaim_page() does not yield page release,
but the page is released shortly afterwards by another thread. Then
z3fold_reclaim_page() would try to list_add() that (released) page again
which is obviously a bug.

To avoid that, spin_lock() has to be taken earlier, before the
kref_put() call mentioned earlier.

Link: http://lkml.kernel.org/r/20170913162937.bfff21c7d12b12a5f47639fd@gmail.com
Signed-off-by: Vitaly Wool <vitalywool@gmail.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: <Oleksiy.Avramchenko@sony.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

z3fold: use per-cpu unbuddied lists

It's been noted that z3fold doesn't scale well when it's run in a large
number of threads on many cores, which can be easily reproduced with fio
'randrw' test with --numjobs=32. E.g. the result for 1 cluster (4 cores)
is:

Run status group 0 (all jobs):
READ: io=244785MB, aggrb=496883KB/s, minb=15527KB/s, ...
WRITE: io=246735MB, aggrb=500841KB/s, minb=15651KB/s, ...

While for 8 cores (2 clusters) the result is:

Run status group 0 (all jobs):
READ: io=244785MB, aggrb=265942KB/s, minb=8310KB/s, ...
WRITE: io=246735MB, aggrb=268060KB/s, minb=8376KB/s, ...

The bottleneck here is the pool lock which many threads become waiting
upon. To reduce that spin lock contention, z3fold can operate only on
the lists local to the current CPU whenever possible. Due to the nature
of z3fold unbuddied list handling (it only takes the first entry off the
list on a hot path), if the z3fold pool is big enough and balanced well
enough, limiting search to only local unbuddied list doesn't lead to a
significant compression ratio degrade (2.57x vs 2.65x in our
measurements).

This patch also introduces two worker threads: one for async in-page
object layout optimization and one for releasing freed pages. This is
done to speed up z3fold_free() which is often on a hot path.

The fio results for 8-core case are now the following:

Run status group 0 (all jobs):
READ: io=244785MB, aggrb=1568.3MB/s, minb=50182KB/s, ...
WRITE: io=246735MB, aggrb=1580.8MB/s, minb=50582KB/s, ...

So we're in for almost 6x performance increase.

Link: http://lkml.kernel.org/r/20170806181443.f9b65018f8bde25ef990f9e8@gmail.com
Signed-off-by: Vitaly Wool <vitalywool@gmail.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

z3fold: fix page locking in z3fold_alloc()

Stress testing of the current z3fold implementation on a 8-core system
revealed it was possible that a z3fold page deleted from its unbuddied
list in z3fold_alloc() would be put on another unbuddied list by
z3fold_free() while z3fold_alloc() is still processing it. This has
been introduced with commit 5a27aa822 ("z3fold: add kref refcounting")
due to the removal of special handling of a z3fold page not on any list
in z3fold_free().

To fix this, the z3fold page lock should be taken in z3fold_alloc()
before the pool lock is released. To avoid deadlocking, we just try to
lock the page as soon as we get a hold of it, and if trylock fails, we
drop this page and take the next one.

Signed-off-by: Vitaly Wool <vitalywool@gmail.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: <Oleksiy.Avramchenko@sony.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

z3fold: fix spinlock unlocking in page reclaim

Commmit 5a27aa822029 ("z3fold: add kref refcounting") introduced a bug
in z3fold_reclaim_page() with function exit that may leave pool->lock
spinlock held. Here comes the trivial fix.

Fixes: 5a27aa822029 ("z3fold: add kref refcounting")
Link: http://lkml.kernel.org/r/20170311222239.7b83d8e7ef1914e05497649f@gmail.com
Reported-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
Signed-off-by: Vitaly Wool <vitalywool@gmail.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

z3fold: add kref refcounting

With both coming and already present locking optimizations, introducing
kref to reference-count z3fold objects is the right thing to do.
Moreover, it makes buddied list no longer necessary, and allows for a
simpler handling of headless pages.

[akpm@linux-foundation.org: coding-style fixes]
Link: http://lkml.kernel.org/r/20170131214650.8ea78033d91ded233f552bc0@gmail.com
Signed-off-by: Vitaly Wool <vitalywool@gmail.com>
Reviewed-by: Dan Streetman <ddstreet@ieee.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

z3fold: use per-page spinlock

Most of z3fold operations are in-page, such as modifying z3fold page
header or moving z3fold objects within a page. Taking per-pool spinlock
to protect per-page objects is therefore suboptimal, and the idea of
having a per-page spinlock (or rwlock) has been around for some time.

This patch implements spinlock-based per-page locking mechanism which is
lightweight enough to normally fit ok into the z3fold header.

Link: http://lkml.kernel.org/r/20170131214438.433e0a5fda908337b63206d3@gmail.com
Signed-off-by: Vitaly Wool <vitalywool@gmail.com>
Reviewed-by: Dan Streetman <ddstreet@ieee.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

z3fold: extend compaction function

z3fold_compact_page() currently only handles the situation when there's
a single middle chunk within the z3fold page. However it may be worth
it to move middle chunk closer to either first or last chunk, whichever
is there, if the gap between them is big enough.

This patch adds the relevant code, using BIG_CHUNK_GAP define as a
threshold for middle chunk to be worth moving.

Link: http://lkml.kernel.org/r/20170131214334.c4f3eac9a477af0fa9a22c46@gmail.com
Signed-off-by: Vitaly Wool <vitalywool@gmail.com>
Reviewed-by: Dan Streetman <ddstreet@ieee.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

z3fold: fix header size related issues

Currently the whole kernel build will be stopped if the size of struct
z3fold_header is greater than the size of one chunk, which is 64 bytes
by default. This patch instead defines the offset for z3fold objects as
the size of the z3fold header in chunks.

Fixed also are the calculation of num_free_chunks() and the address to
move the middle chunk to in case of in-page compaction in
z3fold_compact_page().

Link: http://lkml.kernel.org/r/20170131214057.d98677032bc7b1c6c59a80c9@gmail.com
Signed-off-by: Vitaly Wool <vitalywool@gmail.com>
Reviewed-by: Dan Streetman <ddstreet@ieee.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

z3fold: make pages_nr atomic

Convert pages_nr per-pool counter to atomic64_t.

Link: http://lkml.kernel.org/r/20170131213946.b828676ab17bbea42022c213@gmail.com
Signed-off-by: Vitaly Wool <vitalywool@gmail.com>
Reviewed-by: Dan Streetman <ddstreet@ieee.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/z3fold.c: limit first_num to the actual range of possible buddy indexes

At present, Tying the first_num size to NCHUNKS_ORDER is confusing. the
number of chunks is completely unrelated to the number of buddies.

The patch limits the first_num to actual range of possible buddy indexes.
and that is more reasonable and obvious without functional change.

Link: http://lkml.kernel.org/r/1476776569-29504-1-git-send-email-zhongjiang@huawei.com
Signed-off-by: zhong jiang <zhongjiang@huawei.com>
Suggested-by: Dan Streetman <ddstreet@ieee.org>
Acked-by: Dan Streetman <ddstreet@ieee.org>
Acked-by: Vitaly Wool <vitalywool@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/z3fold.c: avoid modifying HEADLESS page and minor cleanup

Fix erroneous z3fold header access in a HEADLESS page in reclaim
function, and change one remaining direct handle-to-buddy conversion to
use the appropriate helper.

Link: http://lkml.kernel.org/r/5748706F.9020208@gmail.com
Signed-off-by: Vitaly Wool <vitalywool@gmail.com>
Reviewed-by: Dan Streetman <ddstreet@ieee.org>
Cc: Seth Jennings <sjenning@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

z3fold: the 3-fold allocator for compressed pages

This patch introduces z3fold, a special purpose allocator for storing
compressed pages. It is designed to store up to three compressed pages
per physical page. It is a ZBUD derivative which allows for higher
compression ratio keeping the simplicity and determinism of its
predecessor.

This patch comes as a follow-up to the discussions at the Embedded Linux
Conference in San-Diego related to the talk [1]. The outcome of these
discussions was that it would be good to have a compressed page
allocator as stable and deterministic as zbud with with higher
compression ratio.

To keep the determinism and simplicity, z3fold, just like zbud, always
stores an integral number of compressed pages per page, but it can store
up to 3 pages unlike zbud which can store at most 2. Therefore the
compression ratio goes to around 2.6x while zbud's one is around 1.7x.

The patch is based on the latest linux.git tree.

This version has been updated after testing on various simulators (e.g.
ARM Versatile Express, MIPS Malta, x86_64/Haswell) and basing on
comments from Dan Streetman [3].

[1] https://openiotelc2016.sched.org/event/6DAC/swapping-and-embedded-compression-relieves-the-pressure-vitaly-wool-softprise-consulting-ou
[2] https://lkml.org/lkml/2016/4/21/799
[3] https://lkml.org/lkml/2016/5/4/852

Link: http://lkml.kernel.org/r/20160509151753.ec3f9fda3c9898d31ff52a32@gmail.com
Signed-off-by: Vitaly Wool <vitalywool@gmail.com>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>