[PATCH v3 0/9] Update to zstd-1.4.6

Nick Terrell
2020-09-23T22:38:13Z

This patchset upgrades the zstd library to the latest upstream release. The
current zstd version in the kernel is a modified version of upstream zstd-1.3.1.
At the time it was integrated, zstd wasn't ready to be used in the kernel as-is.
But, it is now possible to use upstream zstd directly in the kernel.

I have not yet release zstd-1.4.6 upstream. I want the zstd version in the kernel
to match up with a known upstream release, so we know exactly what code is
running. Whenever this patchset is ready for merge, I will cut a release at the
upstream commit that gets merged. This should not be necessary for future
releases.

The kernel zstd library is automatically generated from upstream zstd. A script
makes the necessary changes and imports it into the kernel. The changes are:

1. Replace all libc dependencies with kernel replacements and rewrite includes.
2. Remove unncessary portability macros like: #if defined(_MSC_VER).
3. 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.

I've updated zstd to upstream with one big patch because every commit must build,
so that precludes partial updates. Since the commit is 100% generated, I hope the
review burden is lightened. I considered replaying upstream commits, but that is
not possible because there have been ~3500 upstream commits since the last zstd
import, and the commits don't all build individually. 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. After this big switch in how the kernel consumes zstd, future patches
will be smaller, because they will only have one upstream release worth of
changes each.

This patchset changes the zstd API from a custom kernel API to the upstream API.
I considered wrapping the upstream API with a wrapper that is closer to the
kernel style guide. Following advise from https://lkml.org/lkml/2020/9/17/814
I've chosen to use the upstream API directly, to minimize opportunities to
introduce bugs, and because using the upstream API directly makes debugging and
communication with upstream easier.

This patchset comes in 3 parts:
1. The first 2 patches prepare for the zstd upgrade. The first patch adds a
compatibility wrapper so zstd can be upgraded without modifying any callers.
The second patch adds an indirection for the lib/decompress_unzstd.c including
of all decompression source files.
2. Import zstd-1.4.6. This patch is completely generated from upstream using
automated tooling.
3. Update all callers to the zstd-1.4.6 API then delete the compatibility
wrapper.

I tested every caller of zstd on x86_64. I tested both after the 1.4.6 upgrade
using the compatibility wrapper, and after the final patch in this series.

I tested kernel and initramfs decompression in i386 and arm.

I ran benchmarks to compare the current zstd in the kernel with zstd-1.4.6.
I benchmarked on x86_64 using QEMU with KVM enabled on an Intel i9-9900k.
I found:
* 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

The latest zstd also offers bug fixes and a 1 KB reduction in stack uage during
compression.

Please let me know if there is anything that I can do to ease the way for these
patches. I think it is important because it gets large performance improvements,
contains bug fixes, and is switching to a more maintainable model of consuming
upstream zstd directly, making it easy to keep up to date.

Best,
Nick Terrell

v1 -> v2:
* Successfully tested F2FS with help from Chao Yu to fix my test.
* (1/9) Fix ZSTD_initCStream() wrapper to handle pledged_src_size=0 means unknown.
This fixes F2FS with the zstd-1.4.6 compatibility wrapper, exposed by the test.

v2 -> v3:
* (3/9) Silence warnings by Kernel Test Robot:
https://github.com/facebook/zstd/pull/2324
Stack size warnings remain, but these aren't new, and the functions it warns on
are either unused or not in the maximum stack path. This patchset reduces zstd
compression stack usage by 1 KB overall. I've gotten the low hanging fruit, and
more stack reduction would require significant changes that have the potential
to introduce new bugs. However, I do hope to continue to reduce zstd stack
usage in future versions.

Nick Terrell (9):
lib: zstd: Add zstd compatibility wrapper
lib: zstd: Add decompress_sources.h for decompress_unzstd
lib: zstd: Upgrade to latest upstream zstd version 1.4.6
crypto: zstd: Switch to zstd-1.4.6 API
btrfs: zstd: Switch to the zstd-1.4.6 API
f2fs: zstd: Switch to the zstd-1.4.6 API
squashfs: zstd: Switch to the zstd-1.4.6 API
lib: unzstd: Switch to the zstd-1.4.6 API
lib: zstd: Remove zstd compatibility wrapper

crypto/zstd.c | 22 +-
fs/btrfs/zstd.c | 46 +-
fs/f2fs/compress.c | 100 +-
fs/squashfs/zstd_wrapper.c | 7 +-
include/linux/zstd.h | 3021 ++++++++----
include/linux/zstd_errors.h | 76 +
lib/decompress_unzstd.c | 44 +-
lib/zstd/Makefile | 35 +-
lib/zstd/bitstream.h | 379 --
lib/zstd/common/bitstream.h | 437 ++
lib/zstd/common/compiler.h | 134 +
lib/zstd/common/cpu.h | 194 +
lib/zstd/common/debug.c | 24 +
lib/zstd/common/debug.h | 101 +
lib/zstd/common/entropy_common.c | 355 ++
lib/zstd/common/error_private.c | 55 +
lib/zstd/common/error_private.h | 66 +
lib/zstd/common/fse.h | 709 +++
lib/zstd/common/fse_decompress.c | 380 ++
lib/zstd/common/huf.h | 352 ++
lib/zstd/common/mem.h | 347 ++
lib/zstd/common/zstd_common.c | 83 +
lib/zstd/common/zstd_deps.h | 134 +
lib/zstd/common/zstd_internal.h | 434 ++
lib/zstd/compress.c | 3485 --------------
lib/zstd/compress/fse_compress.c | 625 +++
lib/zstd/compress/hist.c | 165 +
lib/zstd/compress/hist.h | 75 +
lib/zstd/compress/huf_compress.c | 764 +++
lib/zstd/compress/zstd_compress.c | 4160 +++++++++++++++++
lib/zstd/compress/zstd_compress_internal.h | 1103 +++++
lib/zstd/compress/zstd_compress_literals.c | 158 +
lib/zstd/compress/zstd_compress_literals.h | 29 +
lib/zstd/compress/zstd_compress_sequences.c | 433 ++
lib/zstd/compress/zstd_compress_sequences.h | 54 +
lib/zstd/compress/zstd_compress_superblock.c | 849 ++++
lib/zstd/compress/zstd_compress_superblock.h | 32 +
lib/zstd/compress/zstd_cwksp.h | 524 +++
lib/zstd/compress/zstd_double_fast.c | 521 +++
lib/zstd/compress/zstd_double_fast.h | 32 +
lib/zstd/compress/zstd_fast.c | 496 ++
lib/zstd/compress/zstd_fast.h | 31 +
lib/zstd/compress/zstd_lazy.c | 1138 +++++
lib/zstd/compress/zstd_lazy.h | 61 +
lib/zstd/compress/zstd_ldm.c | 619 +++
lib/zstd/compress/zstd_ldm.h | 104 +
lib/zstd/compress/zstd_opt.c | 1200 +++++
lib/zstd/compress/zstd_opt.h | 50 +
lib/zstd/decompress.c | 2531 ----------
lib/zstd/decompress/huf_decompress.c | 1205 +++++
lib/zstd/decompress/zstd_ddict.c | 241 +
lib/zstd/decompress/zstd_ddict.h | 44 +
lib/zstd/decompress/zstd_decompress.c | 1836 ++++++++
lib/zstd/decompress/zstd_decompress_block.c | 1540 ++++++
lib/zstd/decompress/zstd_decompress_block.h | 62 +
.../decompress/zstd_decompress_internal.h | 195 +
lib/zstd/decompress_sources.h | 18 +
lib/zstd/entropy_common.c | 243 -
lib/zstd/error_private.h | 53 -
lib/zstd/fse.h | 575 ---
lib/zstd/fse_compress.c | 795 ----
lib/zstd/fse_decompress.c | 325 --
lib/zstd/huf.h | 212 -
lib/zstd/huf_compress.c | 772 ---
lib/zstd/huf_decompress.c | 960 ----
lib/zstd/mem.h | 151 -
lib/zstd/zstd_common.c | 75 -
lib/zstd/zstd_compress_module.c | 79 +
lib/zstd/zstd_decompress_module.c | 79 +
lib/zstd/zstd_internal.h | 273 --
lib/zstd/zstd_opt.h | 1014 ----
71 files changed, 24509 insertions(+), 13012 deletions(-)
create mode 100644 include/linux/zstd_errors.h
delete mode 100644 lib/zstd/bitstream.h
create mode 100644 lib/zstd/common/bitstream.h
create mode 100644 lib/zstd/common/compiler.h
create mode 100644 lib/zstd/common/cpu.h
create mode 100644 lib/zstd/common/debug.c
create mode 100644 lib/zstd/common/debug.h
create mode 100644 lib/zstd/common/entropy_common.c
create mode 100644 lib/zstd/common/error_private.c
create mode 100644 lib/zstd/common/error_private.h
create mode 100644 lib/zstd/common/fse.h
create mode 100644 lib/zstd/common/fse_decompress.c
create mode 100644 lib/zstd/common/huf.h
create mode 100644 lib/zstd/common/mem.h
create mode 100644 lib/zstd/common/zstd_common.c
create mode 100644 lib/zstd/common/zstd_deps.h
create mode 100644 lib/zstd/common/zstd_internal.h
delete mode 100644 lib/zstd/compress.c
create mode 100644 lib/zstd/compress/fse_compress.c
create mode 100644 lib/zstd/compress/hist.c
create mode 100644 lib/zstd/compress/hist.h
create mode 100644 lib/zstd/compress/huf_compress.c
create mode 100644 lib/zstd/compress/zstd_compress.c
create mode 100644 lib/zstd/compress/zstd_compress_internal.h
create mode 100644 lib/zstd/compress/zstd_compress_literals.c
create mode 100644 lib/zstd/compress/zstd_compress_literals.h
create mode 100644 lib/zstd/compress/zstd_compress_sequences.c
create mode 100644 lib/zstd/compress/zstd_compress_sequences.h
create mode 100644 lib/zstd/compress/zstd_compress_superblock.c
create mode 100644 lib/zstd/compress/zstd_compress_superblock.h
create mode 100644 lib/zstd/compress/zstd_cwksp.h
create mode 100644 lib/zstd/compress/zstd_double_fast.c
create mode 100644 lib/zstd/compress/zstd_double_fast.h
create mode 100644 lib/zstd/compress/zstd_fast.c
create mode 100644 lib/zstd/compress/zstd_fast.h
create mode 100644 lib/zstd/compress/zstd_lazy.c
create mode 100644 lib/zstd/compress/zstd_lazy.h
create mode 100644 lib/zstd/compress/zstd_ldm.c
create mode 100644 lib/zstd/compress/zstd_ldm.h
create mode 100644 lib/zstd/compress/zstd_opt.c
create mode 100644 lib/zstd/compress/zstd_opt.h
delete mode 100644 lib/zstd/decompress.c
create mode 100644 lib/zstd/decompress/huf_decompress.c
create mode 100644 lib/zstd/decompress/zstd_ddict.c
create mode 100644 lib/zstd/decompress/zstd_ddict.h
create mode 100644 lib/zstd/decompress/zstd_decompress.c
create mode 100644 lib/zstd/decompress/zstd_decompress_block.c
create mode 100644 lib/zstd/decompress/zstd_decompress_block.h
create mode 100644 lib/zstd/decompress/zstd_decompress_internal.h
create mode 100644 lib/zstd/decompress_sources.h
delete mode 100644 lib/zstd/entropy_common.c
delete mode 100644 lib/zstd/error_private.h
delete mode 100644 lib/zstd/fse.h
delete mode 100644 lib/zstd/fse_compress.c
delete mode 100644 lib/zstd/fse_decompress.c
delete mode 100644 lib/zstd/huf.h
delete mode 100644 lib/zstd/huf_compress.c
delete mode 100644 lib/zstd/huf_decompress.c
delete mode 100644 lib/zstd/mem.h
delete mode 100644 lib/zstd/zstd_common.c
create mode 100644 lib/zstd/zstd_compress_module.c
create mode 100644 lib/zstd/zstd_decompress_module.c
delete mode 100644 lib/zstd/zstd_internal.h
delete mode 100644 lib/zstd/zstd_opt.h

--
2.28.0