squashfs: extend "page actor" to handle missing pages

Patch series "Squashfs: handle missing pages decompressing into page
cache".

This patchset enables Squashfs to handle missing pages when directly
decompressing datablocks into the page cache.

Previously if the full set of pages needed was not available, Squashfs
would have to fall back to using an intermediate buffer (the older
method), which is slower, involving a memcopy, and it introduces
contention on a shared buffer.

The first patch extends the "page actor" code to handle missing pages.

The second patch updates Squashfs_readpage_block() to use the new
functionality, and removes the code that falls back to using an
intermediate buffer.

This patchset is independent of the readahead work, and it is standalone.
It can be merged on its own.

But the readahead patch for efficiency also needs this patch-set.


This patch (of 2):

This patch extends the "page actor" code to handle missing pages.

Previously if the full set of pages needed to decompress a Squashfs
datablock was unavailable, this would cause decompression to fail on the
missing pages.

In this case direct decompression into the page cache could not be
achieved and the code would fall back to using the older intermediate
buffer method.

With this patch, direct decompression into the page cache can be achieved
with missing pages.

For "multi-shot" decompressors (zlib, xz, zstd), the page actor will
allocate a temporary buffer which is passed to the decompressor, and then
freed by the page actor.

For "single shot" decompressors (lz4, lzo) which decompress into a
contiguous "bounce buffer", and which is then copied into the page cache,
it would be pointless to allocate a temporary buffer, memcpy into it, and
then free it. For these decompressors -ENOMEM is returned, which
signifies that the memcpy for that page should be skipped.

This also happens if the data block is uncompressed.

Link: https://lkml.kernel.org/r/20220611032133.5743-1-phillip@squashfs.org.uk
Link: https://lkml.kernel.org/r/20220611032133.5743-2-phillip@squashfs.org.uk
Signed-off-by: Phillip Lougher <phillip@squashfs.org.uk>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Hsin-Yi Wang <hsinyi@chromium.org>
Cc: Xiongwei Song <Xiongwei.Song@windriver.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

squashfs: use bvec_virt

Use bvec_virt instead of open coding it.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20210804095634.460779-7-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

squashfs: migrate from ll_rw_block usage to BIO

ll_rw_block() function has been deprecated in favor of BIO which appears
to come with large performance improvements.

This patch decreases boot time by close to 40% when using squashfs for
the root file-system. This is observed at least in the context of
starting an Android VM on Chrome OS using crosvm. The patch was tested
on 4.19 as well as master.

This patch is largely based on Adrien Schildknecht's patch that was
originally sent as https://lkml.org/lkml/2017/9/22/814 though with some
significant changes and simplifications while also taking Phillip
Lougher's feedback into account, around preserving support for
FILE_CACHE in particular.

[akpm@linux-foundation.org: fix build error reported by Randy]
Link: http://lkml.kernel.org/r/319997c2-5fc8-f889-2ea3-d913308a7c1f@infradead.org
Signed-off-by: Philippe Liard <pliard@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Adrien Schildknecht <adrien+dev@schischi.me>
Cc: Phillip Lougher <phillip@squashfs.org.uk>
Cc: Guenter Roeck <groeck@chromium.org>
Cc: Daniel Rosenberg <drosen@google.com>
Link: https://chromium.googlesource.com/chromiumos/platform/crosvm
Link: http://lkml.kernel.org/r/20191106074238.186023-1-pliard@google.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 35

Based on 1 normalized pattern(s):

this program is free software you can redistribute it and or modify
it under the terms of the gnu general public license as published by
the free software foundation either version 2 or at your option any
later version this program is distributed in the hope that it will
be useful but without any warranty without even the implied warranty
of merchantability or fitness for a particular purpose see the gnu
general public license for more details you should have received a
copy of the gnu general public license along with this program if
not write to the free software foundation 51 franklin street fifth
floor boston ma 02110 1301 usa

extracted by the scancode license scanner the SPDX license identifier

GPL-2.0-or-later

has been chosen to replace the boilerplate/reference in 23 file(s).

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Allison Randal <allison@lohutok.net>
Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190520170857.458548087@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

mm, fs: get rid of PAGE_CACHE_* and page_cache_{get,release} macros

PAGE_CACHE_{SIZE,SHIFT,MASK,ALIGN} macros were introduced *long* time
ago with promise that one day it will be possible to implement page
cache with bigger chunks than PAGE_SIZE.

This promise never materialized. And unlikely will.

We have many places where PAGE_CACHE_SIZE assumed to be equal to
PAGE_SIZE. And it's constant source of confusion on whether
PAGE_CACHE_* or PAGE_* constant should be used in a particular case,
especially on the border between fs and mm.

Global switching to PAGE_CACHE_SIZE != PAGE_SIZE would cause to much
breakage to be doable.

Let's stop pretending that pages in page cache are special. They are
not.

The changes are pretty straight-forward:

- <foo> << (PAGE_CACHE_SHIFT - PAGE_SHIFT) -> <foo>;

- <foo> >> (PAGE_CACHE_SHIFT - PAGE_SHIFT) -> <foo>;

- PAGE_CACHE_{SIZE,SHIFT,MASK,ALIGN} -> PAGE_{SIZE,SHIFT,MASK,ALIGN};

- page_cache_get() -> get_page();

- page_cache_release() -> put_page();

This patch contains automated changes generated with coccinelle using
script below. For some reason, coccinelle doesn't patch header files.
I've called spatch for them manually.

The only adjustment after coccinelle is revert of changes to
PAGE_CAHCE_ALIGN definition: we are going to drop it later.

There are few places in the code where coccinelle didn't reach. I'll
fix them manually in a separate patch. Comments and documentation also
will be addressed with the separate patch.

virtual patch

@@
expression E;
@@
- E << (PAGE_CACHE_SHIFT - PAGE_SHIFT)
+ E

@@
expression E;
@@
- E >> (PAGE_CACHE_SHIFT - PAGE_SHIFT)
+ E

@@
@@
- PAGE_CACHE_SHIFT
+ PAGE_SHIFT

@@
@@
- PAGE_CACHE_SIZE
+ PAGE_SIZE

@@
@@
- PAGE_CACHE_MASK
+ PAGE_MASK

@@
expression E;
@@
- PAGE_CACHE_ALIGN(E)
+ PAGE_ALIGN(E)

@@
expression E;
@@
- page_cache_get(E)
+ get_page(E)

@@
expression E;
@@
- page_cache_release(E)
+ put_page(E)

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Squashfs: Generalise paging handling in the decompressors

Further generalise the decompressors by adding a page handler
abstraction. This adds helpers to allow the decompressors
to access and process the output buffers in an implementation
independant manner.

This allows different types of output buffer to be passed
to the decompressors, with the implementation specific
aspects handled at decompression time, but without the
knowledge being held in the decompressor wrapper code.

This will allow the decompressors to handle Squashfs
cache buffers, and page cache pages.

This patch adds the abstraction and an implementation for
the caches.

Signed-off-by: Phillip Lougher <phillip@squashfs.org.uk>
Reviewed-by: Minchan Kim <minchan@kernel.org>

Squashfs: Refactor decompressor interface and code

The decompressor interface and code was written from
the point of view of single-threaded operation. In doing
so it mixed a lot of single-threaded implementation specific
aspects into the decompressor code and elsewhere which makes it
difficult to seamlessly support multiple different decompressor
implementations.

This patch does the following:

1. It removes compressor_options parsing from the decompressor
init() function. This allows the decompressor init() function
to be dynamically called to instantiate multiple decompressors,
without the compressor options needing to be read and parsed each
time.

2. It moves threading and all sleeping operations out of the
decompressors. In doing so, it makes the decompressors
non-blocking wrappers which only deal with interfacing with
the decompressor implementation.

3. It splits decompressor.[ch] into decompressor generic functions
in decompressor.[ch], and moves the single threaded
decompressor implementation into decompressor_single.c.

The result of this patch is Squashfs should now be able to
support multiple decompressors by adding new decompressor_xxx.c
files with specialised implementations of the functions in
decompressor_single.c

Signed-off-by: Phillip Lougher <phillip@squashfs.org.uk>
Reviewed-by: Minchan Kim <minchan@kernel.org>

Squashfs: extend decompressor framework to handle compression options

Extend decompressor framework to handle compression options stored in
the filesystem. These options can be used by the relevant decompressor
at initialisation time to over-ride defaults.

The presence of compression options in the filesystem is indicated by
the COMP_OPT filesystem flag. If present the data is read from the
filesystem and passed to the decompressor init function. The decompressor
init function signature has been extended to take this data.

Also update the init function signature in the glib, lzo and xz
decompressor wrappers.

Signed-off-by: Phillip Lougher <phillip@lougher.demon.co.uk>

Squashfs: move squashfs_i() definition from squashfs.h

Move squashfs_i() definition out of squashfs.h, this eliminates
the need to #include squashfs_fs_i.h from numerous files.

Signed-off-by: Phillip Lougher <phillip@lougher.demon.co.uk>

Squashfs: fix block size use in LZO decompressor

Sizing the buffer using block size alone is incorrect leading
to a potential buffer over-run on 4K block size file systems
(because the metadata block size is always 8K). Srclength is
set to the maximum expected size of the decompressed block and
it is block_size or 8K depending on whether a data or metadata
block is being decompressed.

Signed-off-by: Phillip Lougher <phillip@lougher.demon.co.uk>

Squashfs: Add LZO compression support

Signed-off-by: Chan Jeong <chan.jeong@lge.com>
Signed-off-by: Phillip Lougher <phillip@lougher.demon.co.uk>