squashfs: fix percpu address space issues in decompressor_multi_percpu.c

When strict percpu address space checks are enabled, then current direct
casts between the percpu address space and the gener

squashfs: fix percpu address space issues in decompressor_multi_percpu.c

When strict percpu address space checks are enabled, then current direct
casts between the percpu address space and the generic address space fail
the compilation on x86_64 with:

decompressor_multi_percpu.c: In function `squashfs_decompressor_create':
decompressor_multi_percpu.c:49:16: error: cast to generic address space pointer from disjoint `__seg_gs' address space pointer

decompressor_multi_percpu.c: In function `squashfs_decompressor_destroy':
decompressor_multi_percpu.c:64:25: error: cast to `__seg_gs' address space pointer from disjoint generic address space pointer

decompressor_multi_percpu.c: In function `squashfs_decompress':
decompressor_multi_percpu.c:82:25: error: cast to `__seg_gs' address space pointer from disjoint generic address space pointer

Add intermediate casts to unsigned long, as advised in [1] and [2].

Side note: sparse still requires __force when casting from the percpu
address space, although the documentation [2] allows casts to unsigned
long without __force attribute.

Found by GCC's named address space checks.

There were no changes in the resulting object file.

[1] https://gcc.gnu.org/onlinedocs/gcc/Named-Address-Spaces.html#x86-Named-Address-Spaces
[2] https://sparse.docs.kernel.org/en/latest/annotations.html#address-space-name

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Uros Bizjak <[email protected]>
Cc: Phillip Lougher <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

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squashfs: don't include buffer_head.h

Squashfs has stopped using buffers heads in 93e72b3c612adcaca1
("squashfs: migrate from ll_rw_block usage to BIO").

Link: https://lkml.kernel.org/r/20230517071

squashfs: don't include buffer_head.h

Squashfs has stopped using buffers heads in 93e72b3c612adcaca1
("squashfs: migrate from ll_rw_block usage to BIO").

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Christoph Hellwig <[email protected]>
Reviewed-by: Pankaj Raghav <[email protected]>
Reviewed-by: Phillip Lougher <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

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squashfs: add the mount parameter theads=<single|multi|percpu>

Patch series 'squashfs: Add the mount parameter "threads="'.

Currently, Squashfs supports multiple decompressor parallel modes.
Howev

squashfs: add the mount parameter theads=<single|multi|percpu>

Patch series 'squashfs: Add the mount parameter "threads="'.

Currently, Squashfs supports multiple decompressor parallel modes.
However, this mode can be configured only during kernel building and does
not support flexible selection during runtime.

In the current patch set, the mount parameter "threads=" is added to allow
users to select the parallel decompressor mode and configure the number of
decompressors when mounting a file system.

"threads=<single|multi|percpu|1|2|3|...>"
The upper limit is num_online_cpus() * 2.


This patch (of 2):

Squashfs supports three decompression concurrency modes:
Single-thread mode: concurrent reads are blocked and the memory
overhead is small.
Multi-thread mode/percpu mode: reduces concurrent read blocking but
increases memory overhead.

The corresponding schema must be fixed at compile time. During mounting,
the concurrent decompression mode cannot be adjusted based on file read
blocking.

The mount parameter theads=<single|multi|percpu> is added to select
the concurrent decompression mode of a single SquashFS file system
image.

Link: https://lkml.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Xiaoming Ni <[email protected]>
Reviewed-by: Phillip Lougher <[email protected]>
Cc: Jianguo Chen <[email protected]>
Cc: Jubin Zhong <[email protected]>
Cc: Zhang Yi <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

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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

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.

[[email protected]: fix build error reported by Randy]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Philippe Liard <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
Cc: Adrien Schildknecht <[email protected]>
Cc: Phillip Lougher <[email protected]>
Cc: Guenter Roeck <[email protected]>
Cc: Daniel Rosenberg <[email protected]>
Link: https://chromium.googlesource.com/chromiumos/platform/crosvm
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>

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squashfs: Make use of local lock in multi_cpu decompressor

The squashfs multi CPU decompressor makes use of get_cpu_ptr() to
acquire a pointer to per-CPU data. get_cpu_ptr() implicitly disables
pree

squashfs: Make use of local lock in multi_cpu decompressor

The squashfs multi CPU decompressor makes use of get_cpu_ptr() to
acquire a pointer to per-CPU data. get_cpu_ptr() implicitly disables
preemption which serializes the access to the per-CPU data.

But decompression can take quite some time depending on the size. The
observed preempt disabled times in real world scenarios went up to 8ms,
causing massive wakeup latencies. This happens on all CPUs as the
decompression is fully parallelized.

Replace the implicit preemption control with an explicit local lock.
This allows RT kernels to substitute it with a real per CPU lock, which
serializes the access but keeps the code section preemptible. On non RT
kernels this maps to preempt_disable() as before, i.e. no functional
change.

[ bigeasy: Use local_lock(), patch description]

Reported-by: Alexander Stein <[email protected]>
Signed-off-by: Julia Cartwright <[email protected]>
Signed-off-by: Sebastian Andrzej Siewior <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
Tested-by: Alexander Stein <[email protected]>
Acked-by: Peter Zijlstra <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

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treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 499

Based on 1 normalized pattern(s):

this work is licensed under the terms of the gnu gpl version 2 see
the copying file in the t

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 499

Based on 1 normalized pattern(s):

this work is licensed under the terms of the gnu gpl version 2 see
the copying file in the top level directory

extracted by the scancode license scanner the SPDX license identifier

GPL-2.0-only

has been chosen to replace the boilerplate/reference in 35 file(s).

Signed-off-by: Thomas Gleixner <[email protected]>
Reviewed-by: Kate Stewart <[email protected]>
Reviewed-by: Enrico Weigelt <[email protected]>
Reviewed-by: Allison Randal <[email protected]>
Cc: [email protected]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

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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 proce

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 <[email protected]>
Reviewed-by: Minchan Kim <[email protected]>

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Squashfs: add multi-threaded decompression using percpu variable

Add a multi-threaded decompression implementation which uses
percpu variables.

Using percpu variables has advantages and disadvantag

Squashfs: add multi-threaded decompression using percpu variable

Add a multi-threaded decompression implementation which uses
percpu variables.

Using percpu variables has advantages and disadvantages over
implementations which do not use percpu variables.

Advantages:
* the nature of percpu variables ensures decompression is
load-balanced across the multiple cores.
* simplicity.

Disadvantages: it limits decompression to one thread per core.

Signed-off-by: Phillip Lougher <[email protected]>

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