History log of /openbmc/linux/lib/zstd/common/compiler.h (Results 26 – 45 of 45)
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# 4922f092 14-Dec-2021 Jason Gunthorpe <jgg@nvidia.com>

Merge tag 'v5.16-rc5' into rdma.git for-next

Required due to dependencies in following patches.

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


Revision tags: v5.15.8
# 6773cc31 13-Dec-2021 Ingo Molnar <mingo@kernel.org>

Merge tag 'v5.16-rc5' into locking/core, to pick up fixes

Signed-off-by: Ingo Molnar <mingo@kernel.org>


# a7fb920b 10-Dec-2021 Jonathan Corbet <corbet@lwn.net>

Merge tag 'v5.16-rc4' into docs-next

I have a couple of fixes for warnings introduced after -rc1; catch up to
-rc4 so that the fixes have something to fix.


# 86329873 09-Dec-2021 Daniel Lezcano <daniel.lezcano@linaro.org>

Merge branch 'reset/of-get-optional-exclusive' of git://git.pengutronix.de/pza/linux into timers/drivers/next

"Add optional variant of of_reset_control_get_exclusive(). If the
requested reset is not

Merge branch 'reset/of-get-optional-exclusive' of git://git.pengutronix.de/pza/linux into timers/drivers/next

"Add optional variant of of_reset_control_get_exclusive(). If the
requested reset is not specified in the device tree, this function
returns NULL instead of an error."

This dependency is needed for the Generic Timer Module (a.k.a OSTM)
support for RZ/G2L.

Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>

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Revision tags: v5.15.7
# 4383cfa1 07-Dec-2021 Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

Merge tag 'v5.16-rc4' into media_tree

Linux 5.16-rc4

* tag 'v5.16-rc4': (984 commits)
Linux 5.16-rc4
KVM: SVM: Do not terminate SEV-ES guests on GHCB validation failure
KVM: SEV: Fall back to

Merge tag 'v5.16-rc4' into media_tree

Linux 5.16-rc4

* tag 'v5.16-rc4': (984 commits)
Linux 5.16-rc4
KVM: SVM: Do not terminate SEV-ES guests on GHCB validation failure
KVM: SEV: Fall back to vmalloc for SEV-ES scratch area if necessary
KVM: SEV: Return appropriate error codes if SEV-ES scratch setup fails
parisc: Mark cr16 CPU clocksource unstable on all SMP machines
parisc: Fix "make install" on newer debian releases
sched/uclamp: Fix rq->uclamp_max not set on first enqueue
preempt/dynamic: Fix setup_preempt_mode() return value
cifs: avoid use of dstaddr as key for fscache client cookie
cifs: add server conn_id to fscache client cookie
cifs: wait for tcon resource_id before getting fscache super
cifs: fix missed refcounting of ipc tcon
x86/xen: Add xenpv_restore_regs_and_return_to_usermode()
x86/entry: Use the correct fence macro after swapgs in kernel CR3
fget: check that the fd still exists after getting a ref to it
x86/entry: Add a fence for kernel entry SWAPGS in paranoid_entry()
x86/sev: Fix SEV-ES INS/OUTS instructions for word, dword, and qword
powercap: DTPM: Drop unused local variable from init_dtpm()
io-wq: don't retry task_work creation failure on fatal conditions
serial: 8250_bcm7271: UART errors after resuming from S2
...

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# 83b965d1 06-Dec-2021 Rob Clark <robdclark@chromium.org>

Merge remote-tracking branch 'drm/drm-next' into msm-next-staging

Backmerge drm-next to pull in:

8f59ee9a570c ("drm/msm/dsi: Adjust probe order")

Signed-off-by: Rob Clark <robdclark@chromium.org>


Revision tags: v5.15.6
# 4d012040 29-Nov-2021 Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Merge 5.16-rc3 into usb-next

We need the USB driver fixes in here as well.

Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>


# 24cd7197 29-Nov-2021 Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Merge 5.16-rc3 into staging-next

We need the staging driver fixes in here as well.

Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>


# 5d331b59 29-Nov-2021 Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Merge 5.16-rc3 into char-misc-next

We need the char/misc fixes in here as well.

Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>


# 2448eab4 26-Nov-2021 Linus Walleij <linus.walleij@linaro.org>

Merge tag 'v5.16-rc2' into devel

Linux 5.16-rc2 is needed because nonurgent fixes headed
for next are strongly textually dependent on a fix that
was applied for rc2.

Signed-off-by: Linus Walleij <l

Merge tag 'v5.16-rc2' into devel

Linux 5.16-rc2 is needed because nonurgent fixes headed
for next are strongly textually dependent on a fix that
was applied for rc2.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

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# 93d5404e 26-Nov-2021 Jakub Kicinski <kuba@kernel.org>

Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net

drivers/net/ipa/ipa_main.c
8afc7e471ad3 ("net: ipa: separate disabling setup from modem stop")
76b5fbcd6b47 ("net: ipa: kill ipa_mo

Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net

drivers/net/ipa/ipa_main.c
8afc7e471ad3 ("net: ipa: separate disabling setup from modem stop")
76b5fbcd6b47 ("net: ipa: kill ipa_modem_init()")

Duplicated include, drop one.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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Revision tags: v5.15.5
# 448cc2fb 22-Nov-2021 Jani Nikula <jani.nikula@intel.com>

Merge drm/drm-next into drm-intel-next

Sync up with drm-next to get v5.16-rc2.

Signed-off-by: Jani Nikula <jani.nikula@intel.com>


# 8626afb1 22-Nov-2021 Tvrtko Ursulin <tvrtko.ursulin@intel.com>

Merge drm/drm-next into drm-intel-gt-next

Thomas needs the dma_resv_for_each_fence API for i915/ttm async migration
work.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>


Revision tags: v5.15.4
# 4c388a8e 18-Nov-2021 Linus Torvalds <torvalds@linux-foundation.org>

Merge tag 'zstd-for-linus-5.16-rc1' of git://github.com/terrelln/linux

Pull zstd fixes from Nick Terrell:
"Fix stack usage on parisc & improve code size bloat

This contains three commits:

1.

Merge tag 'zstd-for-linus-5.16-rc1' of git://github.com/terrelln/linux

Pull zstd fixes from Nick Terrell:
"Fix stack usage on parisc & improve code size bloat

This contains three commits:

1. Fixes a minor unused variable warning reported by Kernel test
robot [0].

2. Improves the reported code bloat (-88KB / 374KB) [1] by outlining
some functions that are unlikely to be used in performance
sensitive workloads.

3. Fixes the reported excess stack usage on parisc [2] by removing
-O3 from zstd's compilation flags. -O3 triggered bugs in the
hppa-linux-gnu gcc-8 compiler. -O2 performance is acceptable:
neutral compression, about -1% decompression speed. We also reduce
code bloat (-105KB / 374KB).

After this our code bloat is cut from 374KB to 105KB with gcc-11. If
we wanted to cut the remaining 105KB we'd likely have to trade
signicant performance, so I want to say that this is enough for now.

We should be able to get further gains without sacrificing speed, but
that will take some significant optimization effort, and isn't
suitable for a quick fix. I've opened an upstream issue [3] to track
the code size, and try to avoid future regressions, and improve it in
the long term"

Link: https://lore.kernel.org/linux-mm/202111120312.833wII4i-lkp@intel.com/T/ [0]
Link: https://lkml.org/lkml/2021/11/15/710 [1]
Link: https://lkml.org/lkml/2021/11/14/189 [2]
Link: https://github.com/facebook/zstd/issues/2867 [3]
Link: https://lore.kernel.org/r/20211117014949.1169186-1-nickrterrell@gmail.com/
Link: https://lore.kernel.org/r/20211117201459.1194876-1-nickrterrell@gmail.com/

* tag 'zstd-for-linus-5.16-rc1' of git://github.com/terrelln/linux:
lib: zstd: Don't add -O3 to cflags
lib: zstd: Don't inline functions in zstd_opt.c
lib: zstd: Fix unused variable warning

show more ...


Revision tags: v5.15.3
# 1974990c 15-Nov-2021 Nick Terrell <terrelln@fb.com>

lib: zstd: Don't inline functions in zstd_opt.c

`zstd_opt.c` contains the match finder for the highest compression
levels. These levels are already very slow, and are unlikely to be used
in the kern

lib: zstd: Don't inline functions in zstd_opt.c

`zstd_opt.c` contains the match finder for the highest compression
levels. These levels are already very slow, and are unlikely to be used
in the kernel. If they are used, they shouldn't be used in latency
sensitive workloads, so slowing them down shouldn't be a big deal.

This saves 188 KB of the 288 KB regression reported by Geert Uytterhoeven [0].
I've also opened an issue upstream [1] so that we can properly tackle
the code size issue in `zstd_opt.c` for all users, and can hopefully
remove this hack in the next zstd version we import.

Bloat-o-meter output on x86-64:

```
> ../scripts/bloat-o-meter vmlinux.old vmlinux
add/remove: 6/5 grow/shrink: 1/9 up/down: 16673/-209939 (-193266)
Function old new delta
ZSTD_compressBlock_opt_generic.constprop - 7559 +7559
ZSTD_insertBtAndGetAllMatches - 6304 +6304
ZSTD_insertBt1 - 1731 +1731
ZSTD_storeSeq - 693 +693
ZSTD_BtGetAllMatches - 255 +255
ZSTD_updateRep - 128 +128
ZSTD_updateTree 96 99 +3
ZSTD_insertAndFindFirstIndexHash3 81 - -81
ZSTD_setBasePrices.constprop 98 - -98
ZSTD_litLengthPrice.constprop 138 - -138
ZSTD_count 362 181 -181
ZSTD_count_2segments 1407 938 -469
ZSTD_insertBt1.constprop 2689 - -2689
ZSTD_compressBlock_btultra2 19990 423 -19567
ZSTD_compressBlock_btultra 19633 15 -19618
ZSTD_initStats_ultra 19825 - -19825
ZSTD_compressBlock_btopt 20374 12 -20362
ZSTD_compressBlock_btopt_extDict 29984 12 -29972
ZSTD_compressBlock_btultra_extDict 30718 15 -30703
ZSTD_compressBlock_btopt_dictMatchState 32689 12 -32677
ZSTD_compressBlock_btultra_dictMatchState 33574 15 -33559
Total: Before=6611828, After=6418562, chg -2.92%
```

[0] https://lkml.org/lkml/2021/11/14/189
[1] https://github.com/facebook/zstd/issues/2862

Link: https://lore.kernel.org/r/20211117014949.1169186-3-nickrterrell@gmail.com/
Link: https://lore.kernel.org/r/20211117201459.1194876-3-nickrterrell@gmail.com/

Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Tested-by: Geert Uytterhoeven <geert@linux-m68k.org>
Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Nick Terrell <terrelln@fb.com>

show more ...


# 50fc2494 18-Nov-2021 Jakub Kicinski <kuba@kernel.org>

Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net

Signed-off-by: Jakub Kicinski <kuba@kernel.org>


# a713ca23 18-Nov-2021 Thomas Zimmermann <tzimmermann@suse.de>

Merge drm/drm-next into drm-misc-next

Backmerging from drm/drm-next for v5.16-rc1.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>


# 467dd91e 16-Nov-2021 Maxime Ripard <maxime@cerno.tech>

Merge drm/drm-fixes into drm-misc-fixes

We need -rc1 to address a breakage in drm/scheduler affecting panfrost.

Signed-off-by: Maxime Ripard <maxime@cerno.tech>


# c8c10954 13-Nov-2021 Linus Torvalds <torvalds@linux-foundation.org>

Merge tag 'zstd-for-linus-v5.16' of git://github.com/terrelln/linux

Pull zstd update from Nick Terrell:
"Update to zstd-1.4.10.

Add myself as the maintainer of zstd and update the zstd version i

Merge tag 'zstd-for-linus-v5.16' of git://github.com/terrelln/linux

Pull zstd update from Nick Terrell:
"Update to zstd-1.4.10.

Add myself as the maintainer of zstd and update the zstd version in
the kernel, which is now 4 years out of date, to a much more recent
zstd release. This includes bug fixes, much more extensive fuzzing,
and performance improvements. And generates the kernel zstd
automatically from upstream zstd, so it is easier to keep the zstd
verison up to date, and we don't fall so far out of date again.

This includes 5 commits that update the zstd library version:

- Adds a new kernel-style wrapper around zstd.

This wrapper API is functionally equivalent to the subset of the
current zstd API that is currently used. The wrapper API changes to
be kernel style so that the symbols don't collide with zstd's
symbols. The update to zstd-1.4.10 maintains the same API and
preserves the semantics, so that none of the callers need to be
updated. All callers are updated in the commit, because there are
zero functional changes.

- Adds an indirection for `lib/decompress_unzstd.c` so it doesn't
depend on the layout of `lib/zstd/` to include every source file.
This allows the next patch to be automatically generated.

- Imports the zstd-1.4.10 source code. This commit is automatically
generated from upstream zstd (https://github.com/facebook/zstd).

- Adds me (terrelln@fb.com) as the maintainer of `lib/zstd`.

- Fixes a newly added build warning for clang.

The discussion around this patchset has been pretty long, so I've
included a FAQ-style summary of the history of the patchset, and why
we are taking this approach.

Why do we need to update?
-------------------------

The zstd version in the kernel is based off of zstd-1.3.1, which is
was released August 20, 2017. Since then zstd has seen many bug fixes
and performance improvements. And, importantly, upstream zstd is
continuously fuzzed by OSS-Fuzz, and bug fixes aren't backported to
older versions. So the only way to sanely get these fixes is to keep
up to date with upstream zstd.

There are no known security issues that affect the kernel, but we need
to be able to update in case there are. And while there are no known
security issues, there are relevant bug fixes. For example the problem
with large kernel decompression has been fixed upstream for over 2
years [1]

Additionally the performance improvements for kernel use cases are
significant. Measured for x86_64 on my Intel i9-9900k @ 3.6 GHz:

- BtrFS zstd compression at levels 1 and 3 is 5% faster

- BtrFS zstd decompression+read is 15% faster

- SquashFS zstd decompression+read is 15% faster

- F2FS zstd compression+write at level 3 is 8% faster

- F2FS zstd decompression+read is 20% faster

- ZRAM decompression+read is 30% faster

- Kernel zstd decompression is 35% faster

- Initramfs zstd decompression+build is 5% faster

On top of this, there are significant performance improvements coming
down the line in the next zstd release, and the new automated update
patch generation will allow us to pull them easily.

How is the update patch generated?
----------------------------------

The first two patches are preparation for updating the zstd version.
Then the 3rd patch in the series imports upstream zstd into the
kernel. This patch is automatically generated from upstream. A script
makes the necessary changes and imports it into the kernel. The
changes are:

- Replace all libc dependencies with kernel replacements and rewrite
includes.

- Remove unncessary portability macros like: #if defined(_MSC_VER).

- Use the kernel xxhash instead of bundling it.

This automation gets tested every commit by upstream's continuous
integration. When we cut a new zstd release, we will submit a patch to
the kernel to update the zstd version in the kernel.

The automated process makes it easy to keep the kernel version of zstd
up to date. The current zstd in the kernel shares the guts of the
code, but has a lot of API and minor changes to work in the kernel.
This is because at the time upstream zstd was not ready to be used in
the kernel envrionment as-is. But, since then upstream zstd has
evolved to support being used in the kernel as-is.

Why are we updating in one big patch?
-------------------------------------

The 3rd patch in the series is very large. This is because it is
restructuring the code, so it both deletes the existing zstd, and
re-adds the new structure. Future updates will be directly
proportional to the changes in upstream zstd since the last import.
They will admittidly be large, as zstd is an actively developed
project, and has hundreds of commits between every release. However,
there is no other great alternative.

One option ruled out is to replay every upstream zstd commit. This is
not feasible for several reasons:

- There are over 3500 upstream commits since the zstd version in the
kernel.

- The automation to automatically generate the kernel update was only
added recently, so older commits cannot easily be imported.

- Not every upstream zstd commit builds.

- Only zstd releases are "supported", and individual commits may have
bugs that were fixed before a release.

Another option to reduce the patch size would be to first reorganize
to the new file structure, and then apply the patch. However, the
current kernel zstd is formatted with clang-format to be more
"kernel-like". But, the new method imports zstd as-is, without
additional formatting, to allow for closer correlation with upstream,
and easier debugging. So the patch wouldn't be any smaller.

It also doesn't make sense to import upstream zstd commit by commit
going forward. Upstream zstd doesn't support production use cases
running of the development branch. We have a lot of post-commit
fuzzing that catches many bugs, so indiviudal commits may be buggy,
but fixed before a release. So going forward, I intend to import every
(important) zstd release into the Kernel.

So, while it isn't ideal, updating in one big patch is the only patch
I see forward.

Who is responsible for this code?
---------------------------------

I am. This patchset adds me as the maintainer for zstd. Previously,
there was no tree for zstd patches. Because of that, there were
several patches that either got ignored, or took a long time to merge,
since it wasn't clear which tree should pick them up. I'm officially
stepping up as maintainer, and setting up my tree as the path through
which zstd patches get merged. I'll make sure that patches to the
kernel zstd get ported upstream, so they aren't erased when the next
version update happens.

How is this code tested?
------------------------

I tested every caller of zstd on x86_64 (BtrFS, ZRAM, SquashFS, F2FS,
Kernel, InitRAMFS). I also tested Kernel & InitRAMFS on i386 and
aarch64. I checked both performance and correctness.

Also, thanks to many people in the community who have tested these
patches locally.

Lastly, this code will bake in linux-next before being merged into
v5.16.

Why update to zstd-1.4.10 when zstd-1.5.0 has been released?
------------------------------------------------------------

This patchset has been outstanding since 2020, and zstd-1.4.10 was the
latest release when it was created. Since the update patch is
automatically generated from upstream, I could generate it from
zstd-1.5.0.

However, there were some large stack usage regressions in zstd-1.5.0,
and are only fixed in the latest development branch. And the latest
development branch contains some new code that needs to bake in the
fuzzer before I would feel comfortable releasing to the kernel.

Once this patchset has been merged, and we've released zstd-1.5.1, we
can update the kernel to zstd-1.5.1, and exercise the update process.

You may notice that zstd-1.4.10 doesn't exist upstream. This release
is an artifical release based off of zstd-1.4.9, with some fixes for
the kernel backported from the development branch. I will tag the
zstd-1.4.10 release after this patchset is merged, so the Linux Kernel
is running a known version of zstd that can be debugged upstream.

Why was a wrapper API added?
----------------------------

The first versions of this patchset migrated the kernel to the
upstream zstd API. It first added a shim API that supported the new
upstream API with the old code, then updated callers to use the new
shim API, then transitioned to the new code and deleted the shim API.
However, Cristoph Hellwig suggested that we transition to a kernel
style API, and hide zstd's upstream API behind that. This is because
zstd's upstream API is supports many other use cases, and does not
follow the kernel style guide, while the kernel API is focused on the
kernel's use cases, and follows the kernel style guide.

Where is the previous discussion?
---------------------------------

Links for the discussions of the previous versions of the patch set
below. The largest changes in the design of the patchset are driven by
the discussions in v11, v5, and v1. Sorry for the mix of links, I
couldn't find most of the the threads on lkml.org"

Link: https://lkml.org/lkml/2020/9/29/27 [1]
Link: https://www.spinics.net/lists/linux-crypto/msg58189.html [v12]
Link: https://lore.kernel.org/linux-btrfs/20210430013157.747152-1-nickrterrell@gmail.com/ [v11]
Link: https://lore.kernel.org/lkml/20210426234621.870684-2-nickrterrell@gmail.com/ [v10]
Link: https://lore.kernel.org/linux-btrfs/20210330225112.496213-1-nickrterrell@gmail.com/ [v9]
Link: https://lore.kernel.org/linux-f2fs-devel/20210326191859.1542272-1-nickrterrell@gmail.com/ [v8]
Link: https://lkml.org/lkml/2020/12/3/1195 [v7]
Link: https://lkml.org/lkml/2020/12/2/1245 [v6]
Link: https://lore.kernel.org/linux-btrfs/20200916034307.2092020-1-nickrterrell@gmail.com/ [v5]
Link: https://www.spinics.net/lists/linux-btrfs/msg105783.html [v4]
Link: https://lkml.org/lkml/2020/9/23/1074 [v3]
Link: https://www.spinics.net/lists/linux-btrfs/msg105505.html [v2]
Link: https://lore.kernel.org/linux-btrfs/20200916034307.2092020-1-nickrterrell@gmail.com/ [v1]
Signed-off-by: Nick Terrell <terrelln@fb.com>
Tested By: Paul Jones <paul@pauljones.id.au>
Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com> # LLVM/Clang v13.0.0 on x86-64
Tested-by: Jean-Denis Girard <jd.girard@sysnux.pf>

* tag 'zstd-for-linus-v5.16' of git://github.com/terrelln/linux:
lib: zstd: Add cast to silence clang's -Wbitwise-instead-of-logical
MAINTAINERS: Add maintainer entry for zstd
lib: zstd: Upgrade to latest upstream zstd version 1.4.10
lib: zstd: Add decompress_sources.h for decompress_unzstd
lib: zstd: Add kernel-specific API

show more ...


Revision tags: v5.15.2, v5.15.1, v5.15, v5.14.14, v5.14.13, v5.14.12, v5.14.11, v5.14.10, v5.14.9, v5.14.8, v5.14.7, v5.14.6, v5.10.67, v5.10.66, v5.14.5, v5.14.4, v5.10.65, v5.14.3, v5.10.64, v5.14.2, v5.10.63, v5.14.1, v5.10.62, v5.14, v5.10.61, v5.10.60, v5.10.53, v5.10.52, v5.10.51, v5.10.50, v5.10.49, v5.13, v5.10.46, v5.10.43, v5.10.42, v5.10.41, v5.10.40, v5.10.39, v5.4.119, v5.10.36, v5.10.35, v5.10.34, v5.4.116, v5.10.33, v5.12, v5.10.32, v5.10.31, v5.10.30, v5.10.27, v5.10.26, v5.10.25, v5.10.24, v5.10.23, v5.10.22, v5.10.21, v5.10.20, v5.10.19, v5.4.101, v5.10.18, v5.10.17, v5.11, v5.10.16, v5.10.15, v5.10.14, v5.10, v5.8.17, v5.8.16, v5.8.15, v5.9, v5.8.14, v5.8.13, v5.8.12, v5.8.11, v5.8.10, v5.8.9
# e0c1b49f 11-Sep-2020 Nick Terrell <terrelln@fb.com>

lib: zstd: Upgrade to latest upstream zstd version 1.4.10

Upgrade to the latest upstream zstd version 1.4.10.

This patch is 100% generated from upstream zstd commit 20821a46f412 [0].

This patch is

lib: zstd: Upgrade to latest upstream zstd version 1.4.10

Upgrade to the latest upstream zstd version 1.4.10.

This patch is 100% generated from upstream zstd commit 20821a46f412 [0].

This patch is very large because it is transitioning from the custom
kernel zstd to using upstream directly. The new zstd follows upstreams
file structure which is different. Future update patches will be much
smaller because they will only contain the changes from one upstream
zstd release.

As an aid for review I've created a commit [1] that shows the diff
between upstream zstd as-is (which doesn't compile), and the zstd
code imported in this patch. The verion of zstd in this patch is
generated from upstream with changes applied by automation to replace
upstreams libc dependencies, remove unnecessary portability macros,
replace `/**` comments with `/*` comments, and use the kernel's xxhash
instead of bundling it.

The benefits of this patch are as follows:
1. Using upstream directly with automated script to generate kernel
code. This allows us to update the kernel every upstream release, so
the kernel gets the latest bug fixes and performance improvements,
and doesn't get 3 years out of date again. The automation and the
translated code are tested every upstream commit to ensure it
continues to work.
2. Upgrades from a custom zstd based on 1.3.1 to 1.4.10, getting 3 years
of performance improvements and bug fixes. On x86_64 I've measured
15% faster BtrFS and SquashFS decompression+read speeds, 35% faster
kernel decompression, and 30% faster ZRAM decompression+read speeds.
3. Zstd-1.4.10 supports negative compression levels, which allow zstd to
match or subsume lzo's performance.
4. Maintains the same kernel-specific wrapper API, so no callers have to
be modified with zstd version updates.

One concern that was brought up was stack usage. Upstream zstd had
already removed most of its heavy stack usage functions, but I just
removed the last functions that allocate arrays on the stack. I've
measured the high water mark for both compression and decompression
before and after this patch. Decompression is approximately neutral,
using about 1.2KB of stack space. Compression levels up to 3 regressed
from 1.4KB -> 1.6KB, and higher compression levels regressed from 1.5KB
-> 2KB. We've added unit tests upstream to prevent further regression.
I believe that this is a reasonable increase, and if it does end up
causing problems, this commit can be cleanly reverted, because it only
touches zstd.

I chose the bulk update instead of replaying upstream commits because
there have been ~3500 upstream commits since the 1.3.1 release, zstd
wasn't ready to be used in the kernel as-is before a month ago, and not
all upstream zstd commits build. The bulk update preserves bisectablity
because bugs can be bisected to the zstd version update. At that point
the update can be reverted, and we can work with upstream to find and
fix the bug.

Note that upstream zstd release 1.4.10 doesn't exist yet. I have cut a
staging branch at 20821a46f412 [0] and will apply any changes requested
to the staging branch. Once we're ready to merge this update I will cut
a zstd release at the commit we merge, so we have a known zstd release
in the kernel.

The implementation of the kernel API is contained in
zstd_compress_module.c and zstd_decompress_module.c.

[0] https://github.com/facebook/zstd/commit/20821a46f4122f9abd7c7b245d28162dde8129c9
[1] https://github.com/terrelln/linux/commit/e0fa481d0e3df26918da0a13749740a1f6777574

Signed-off-by: Nick Terrell <terrelln@fb.com>
Tested By: Paul Jones <paul@pauljones.id.au>
Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com> # LLVM/Clang v13.0.0 on x86-64
Tested-by: Jean-Denis Girard <jd.girard@sysnux.pf>

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