On Wed, Oct 6, 2021 at 9:21 PM Nick Terrell <nickrterrell@xxxxxxxxx> wrote: > > From: Nick Terrell <terrelln@xxxxxx> > > The following changes since commit 9e1ff307c779ce1f0f810c7ecce3d95bbae40896: > > Linux 5.15-rc4 (2021-10-03 14:08:47 -0700) > > are available in the Git repository at: > > https://github.com/terrelln/linux.git zstd-1.4.10 > > for you to fetch changes up to a0ccd980d5048053578f3b524e3cd3f5d980a9c5: > > MAINTAINERS: Add maintainer entry for zstd (2021-10-04 20:04:32 -0700) > > I would like to merge this pull request into linux-next to bake, and then submit > the PR to Linux in the 5.16 merge window. If you have been a part of the > discussion, are a maintainer of a caller of zstd, tested this code, or otherwise > been involved, thank you! And could you please respond below with an appropiate > tag, so I can collect support for the PR > > Best, > Nick Terrell > > ---------------------------------------------------------------- > Update to zstd-1.4.10 > > - The first commit 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. > - The second commit 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. > - The third commit is automatically generated, and imports the zstd-1.4.10 source > code. This commit is completely generated by automation. > - The fourth commit adds me (terrelln@xxxxxx) as the maintainer of `lib/zstd`. > > 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 https://lkml.org/lkml/2020/9/29/27. > > 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. > If you have tested the patches, please reply with a Tested-By so I can collect them > for the PR I will send to Linus. > > 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. > > Changelog > --------- > > 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. > > v3 -> v4: > * (3/9) Fix errors and warnings reported by Kernel Test Robot: > https://github.com/facebook/zstd/pull/2326 > - Replace mem.h with a custom kernel implementation that matches the current > lib/zstd/mem.h in the kernel. This avoids calls to __builtin_bswap*() which > don't work on certain architectures, as exposed by the Kernel Test Robot. > - Remove ASAN/MSAN (un)poisoning code which doesn't work in the kernel, as > exposed by the Kernel Test Robot. > - I've fixed all of the valid cppcheck warnings reported, but there were many > false positives, where cppcheck was incorrectly analyzing the situation, > which I did not fix. I don't believe it is reasonable to expect that upstream > zstd silences all the static analyzer false positives. Upstream zstd uses > clang scan-build for its static analysis. We find that supporting multiple > static analysis tools multiplies the burden of silencing false positives, > without providing enough marginal value over running a single static analysis > tool. > > v4 -> v5: > * Rebase onto v5.10-rc2 > * (6/9) Merge with other F2FS changes (no functional change in patch). > > v5 -> v6: > * Rebase onto v5.10-rc6. > * Switch to using a kernel style wrapper API as suggested by Cristoph. > > v6 -> v7: > * Expose the upstream library header as `include/linux/zstd_lib.h`. > Instead of creating new structs mirroring the upstream zstd structs > use upstream's structs directly with a typedef to get a kernel style name. > This removes the memcpy cruft. > * (1/3) Undo ZSTD_WINDOWLOG_MAX and handle_zstd_error changes. > * (3/3) Expose zstd_errors.h as `include/linux/zstd_errors.h` because it > is needed by the kernel wrapper API. > > v7 -> v8: > * (1/3) Fix typo in EXPORT_SYMBOL(). > * (1/3) Fix typo in zstd.h comments. > * (3/3) Update to latest zstd release: 1.4.6 -> 1.4.10 > This includes ~1KB of stack space reductions. > > v8 -> v9: > * (1/3) Rebase onto v5.12-rc5 > * (1/3) Add zstd_min_clevel() & zstd_max_clevel() and use in f2fs. > Thanks to Oleksandr Natalenko for spotting it! > * (1/3) Move lib/decompress_unzstd.c usage of ZSTD_getErrorCode() > to zstd_get_error_code(). > * (1/3) Update modified zstd headers to yearless copyright. > * (2/3) Add copyright/license header to decompress_sources.h for consistency. > * (3/3) Update to yearless copyright for all zstd files. Thanks to > Mike Dolan for spotting it! > > v9 -> v10: > * Add a 4th patch in the series which adds an entry for zstd to MAINTAINERS. > > v10 -> v11: > * Rebase cleanly onto v5.12-rc8 > * (3/4) Replace invalid kernel style comments in zstd with regular comments. > Thanks to Randy Dunlap for the suggestion. > > v11 -> v12: > * Re-write the cover letter & send as a PR only. > * Rebase cleanly onto 5.15-rc4. > * (3/4) Clean up licensing to reflect that we're GPL-2.0+ OR BSD-3-Clause. > * (3/4) Reduce compression stack usage by 80 bytes. > * (3/4) Make upstream zstd `-Wfall-through` compliant and use the FALLTHROUGH > macro in the Linux Kernel. > > Signed-off-by: Nick Terrell <terrelln@xxxxxx> > Tested By: Paul Jones <paul@xxxxxxxxxxxxxxx> > Tested-by: Oleksandr Natalenko <oleksandr@xxxxxxxxxxxxxx> > Hi Nick, can you please CC me on further patchsets? Thanks for taking responsibility as linux-zstd maintainer. I am currently testing this on top of Linux v5.15-rc4 building with LLVM/Clang v13. Do I also need ZSTD version 1.4.10 in user-space? Debian/unstable AMD64 ships here version 1.4.8. Thanks. Regards, - Sedat - > ---------------------------------------------------------------- > Nick Terrell (4): > lib: zstd: Add kernel-specific API > lib: zstd: Add decompress_sources.h for decompress_unzstd > lib: zstd: Upgrade to latest upstream zstd version 1.4.10 > MAINTAINERS: Add maintainer entry for zstd > > MAINTAINERS | 12 + > crypto/zstd.c | 28 +- > fs/btrfs/zstd.c | 68 +- > fs/f2fs/compress.c | 56 +- > fs/f2fs/super.c | 2 +- > fs/pstore/platform.c | 2 +- > fs/squashfs/zstd_wrapper.c | 16 +- > include/linux/zstd.h | 1252 ++---- > include/linux/zstd_errors.h | 77 + > include/linux/zstd_lib.h | 2432 +++++++++++ > lib/decompress_unzstd.c | 48 +- > lib/zstd/Makefile | 46 +- > lib/zstd/bitstream.h | 380 -- > lib/zstd/common/bitstream.h | 437 ++ > lib/zstd/common/compiler.h | 170 + > lib/zstd/common/cpu.h | 194 + > lib/zstd/common/debug.c | 24 + > lib/zstd/common/debug.h | 101 + > lib/zstd/common/entropy_common.c | 357 ++ > lib/zstd/common/error_private.c | 56 + > lib/zstd/common/error_private.h | 66 + > lib/zstd/common/fse.h | 710 ++++ > lib/zstd/common/fse_decompress.c | 390 ++ > lib/zstd/common/huf.h | 356 ++ > lib/zstd/common/mem.h | 259 ++ > lib/zstd/common/zstd_common.c | 83 + > lib/zstd/common/zstd_deps.h | 125 + > lib/zstd/common/zstd_internal.h | 450 +++ > 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 | 905 +++++ > lib/zstd/compress/zstd_compress.c | 5109 ++++++++++++++++++++++++ > lib/zstd/compress/zstd_compress_internal.h | 1188 ++++++ > lib/zstd/compress/zstd_compress_literals.c | 158 + > lib/zstd/compress/zstd_compress_literals.h | 29 + > lib/zstd/compress/zstd_compress_sequences.c | 439 ++ > lib/zstd/compress/zstd_compress_sequences.h | 54 + > lib/zstd/compress/zstd_compress_superblock.c | 850 ++++ > lib/zstd/compress/zstd_compress_superblock.h | 32 + > lib/zstd/compress/zstd_cwksp.h | 482 +++ > lib/zstd/compress/zstd_double_fast.c | 519 +++ > 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 | 1412 +++++++ > lib/zstd/compress/zstd_lazy.h | 81 + > lib/zstd/compress/zstd_ldm.c | 686 ++++ > lib/zstd/compress/zstd_ldm.h | 110 + > lib/zstd/compress/zstd_ldm_geartab.h | 103 + > lib/zstd/compress/zstd_opt.c | 1345 +++++++ > lib/zstd/compress/zstd_opt.h | 50 + > lib/zstd/decompress.c | 2531 ------------ > lib/zstd/decompress/huf_decompress.c | 1206 ++++++ > lib/zstd/decompress/zstd_ddict.c | 241 ++ > lib/zstd/decompress/zstd_ddict.h | 44 + > lib/zstd/decompress/zstd_decompress.c | 2082 ++++++++++ > lib/zstd/decompress/zstd_decompress_block.c | 1540 +++++++ > lib/zstd/decompress/zstd_decompress_block.h | 62 + > lib/zstd/decompress/zstd_decompress_internal.h | 202 + > lib/zstd/decompress_sources.h | 28 + > 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 | 773 ---- > lib/zstd/huf_decompress.c | 960 ----- > lib/zstd/mem.h | 151 - > lib/zstd/zstd_common.c | 75 - > lib/zstd/zstd_compress_module.c | 160 + > lib/zstd/zstd_decompress_module.c | 105 + > lib/zstd/zstd_internal.h | 273 -- > lib/zstd/zstd_opt.h | 1014 ----- > 76 files changed, 27367 insertions(+), 12941 deletions(-) > create mode 100644 include/linux/zstd_errors.h > create mode 100644 include/linux/zstd_lib.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_ldm_geartab.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
