lwn.git/lib, branch v5.16-rc3

parisc: Increase FRAME_WARN to 2048 bytes on parisc

2021-11-22T06:37:31+00:00

PA-RISC uses a much bigger frame size for functions than other architectures. So increase it to 2048 for 32- and 64-bit kernels. This fixes e.g. a warning in lib/xxhash.c. Reported-by: kernel test robot Signed-off-by: Helge Deller

kasan: test: silence intentional read overflow warnings

2021-11-20T18:35:54+00:00

As done in commit d73dad4eb5ad ("kasan: test: bypass __alloc_size checks") for __write_overflow warnings, also silence some more cases that trip the __read_overflow warnings seen in 5.16-rc1[1]: In file included from include/linux/string.h:253, from include/linux/bitmap.h:10, from include/linux/cpumask.h:12, from include/linux/mm_types_task.h:14, from include/linux/mm_types.h:5, from include/linux/page-flags.h:13, from arch/arm64/include/asm/mte.h:14, from arch/arm64/include/asm/pgtable.h:12, from include/linux/pgtable.h:6, from include/linux/kasan.h:29, from lib/test_kasan.c:10: In function 'memcmp', inlined from 'kasan_memcmp' at lib/test_kasan.c:897:2: include/linux/fortify-string.h:263:25: error: call to '__read_overflow' declared with attribute error: detected read beyond size of object (1st parameter) 263 | __read_overflow(); | ^~~~~~~~~~~~~~~~~ In function 'memchr', inlined from 'kasan_memchr' at lib/test_kasan.c:872:2: include/linux/fortify-string.h:277:17: error: call to '__read_overflow' declared with attribute error: detected read beyond size of object (1st parameter) 277 | __read_overflow(); | ^~~~~~~~~~~~~~~~~ [1] http://kisskb.ellerman.id.au/kisskb/buildresult/14660585/log/ Link: https://lkml.kernel.org/r/20211116004111.3171781-1-keescook@chromium.org Fixes: d73dad4eb5ad ("kasan: test: bypass __alloc_size checks") Signed-off-by: Kees Cook Reviewed-by: Andrey Konovalov Acked-by: Marco Elver Cc: Andrey Ryabinin Cc: Alexander Potapenko Cc: Dmitry Vyukov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

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

2021-11-19T01:09:05+00:00

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

lib: zstd: Don't add -O3 to cflags

2021-11-18T21:16:22+00:00

After the update to zstd-1.4.10 passing -O3 is no longer necessary to get good performance from zstd. Using the default optimization level -O2 is sufficient to get good performance. I've measured no significant change to compression speed, and a ~1% decompression speed loss, which is acceptable. This fixes the reported parisc -Wframe-larger-than=1536 errors [0]. The gcc-8-hppa-linux-gnu compiler performed very poorly with -O3, generating stacks that are ~3KB. With -O2 these same functions generate stacks in the < 100B, completely fixing the problem. Function size deltas are listed below: ZSTD_compressBlock_fast_extDict_generic: 3800 -> 68 ZSTD_compressBlock_fast: 2216 -> 40 ZSTD_compressBlock_fast_dictMatchState: 1848 -> 64 ZSTD_compressBlock_doubleFast_extDict_generic: 3744 -> 76 ZSTD_fillDoubleHashTable: 3252 -> 0 ZSTD_compressBlock_doubleFast: 5856 -> 36 ZSTD_compressBlock_doubleFast_dictMatchState: 5380 -> 84 ZSTD_copmressBlock_lazy2: 2420 -> 72 Additionally, this improves the reported code bloat [1]. With gcc-11 bloat-o-meter shows an 80KB code size improvement: ``` > ../scripts/bloat-o-meter vmlinux.old vmlinux add/remove: 31/8 grow/shrink: 24/155 up/down: 25734/-107924 (-82190) Total: Before=6418562, After=6336372, chg -1.28% ``` Compared to before the zstd-1.4.10 update we see a total code size regression of 105KB, down from 374KB at v5.16-rc1: ``` > ../scripts/bloat-o-meter vmlinux.old vmlinux add/remove: 292/62 grow/shrink: 56/88 up/down: 235009/-127487 (107522) Total: Before=6228850, After=6336372, chg +1.73% ``` [0] https://lkml.org/lkml/2021/11/15/710 [1] https://lkml.org/lkml/2021/11/14/189 Link: https://lore.kernel.org/r/20211117014949.1169186-4-nickrterrell@gmail.com/ Link: https://lore.kernel.org/r/20211117201459.1194876-4-nickrterrell@gmail.com/ Reported-by: Geert Uytterhoeven Tested-by: Geert Uytterhoeven Reviewed-by: Geert Uytterhoeven Signed-off-by: Nick Terrell

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

2021-11-18T21:15:33+00:00

`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 Tested-by: Geert Uytterhoeven Reviewed-by: Geert Uytterhoeven Signed-off-by: Nick Terrell

lib: zstd: Fix unused variable warning

2021-11-18T21:12:26+00:00

The variable `litLengthSum` is only used by an `assert()`, so when asserts are disabled the compiler doesn't see any usage and warns. This issue is already fixed upstream by PR #2838 [0]. It was reported by the Kernel test robot in [1]. Another approach would be to change zstd's disabled `assert()` definition to use the argument in a disabled branch, instead of ignoring the argument. I've avoided this approach because there are some small changes necessary to get zstd to build, and I would want to thoroughly re-test for performance, since that is slightly changing the code in every function in zstd. It seems like a trivial change, but some functions are pretty sensitive to small changes. However, I think it is a valid approach that I would like to see upstream take, so I've opened Issue #2868 to attempt this upstream. Lastly, I've chosen not to use __maybe_unused because all code in lib/zstd/ must eventually be upstreamed. Upstream zstd can't use __maybe_unused because it isn't portable across all compilers. [0] https://github.com/facebook/zstd/pull/2838 [1] https://lore.kernel.org/linux-mm/202111120312.833wII4i-lkp@intel.com/T/ [2] https://github.com/facebook/zstd/issues/2868 Link: https://lore.kernel.org/r/20211117014949.1169186-2-nickrterrell@gmail.com/ Link: https://lore.kernel.org/r/20211117201459.1194876-2-nickrterrell@gmail.com/ Reported-by: kernel test robot Signed-off-by: Nick Terrell

Merge tag 'printk-for-5.16-fixup' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux

2021-11-18T18:50:45+00:00

Pull printk fixes from Petr Mladek: - Try to flush backtraces from other CPUs also on the local one. This was a regression caused by printk_safe buffers removal. - Remove header dependency warning. * tag 'printk-for-5.16-fixup' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux: printk: Remove printk.h inclusion in percpu.h printk: restore flushing of NMI buffers on remote CPUs after NMI backtraces

Merge branch 'rework/printk_safe-removal' into for-linus

2021-11-18T09:03:47+00:00

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

2021-11-13T23:32:30+00:00

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 Tested By: Paul Jones Tested-by: Oleksandr Natalenko Tested-by: Sedat Dilek # LLVM/Clang v13.0.0 on x86-64 Tested-by: Jean-Denis Girard * 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

mm/migrate.c: remove MIGRATE_PFN_LOCKED

2021-11-11T17:34:35+00:00

MIGRATE_PFN_LOCKED is used to indicate to migrate_vma_prepare() that a source page was already locked during migrate_vma_collect(). If it wasn't then the a second attempt is made to lock the page. However if the first attempt failed it's unlikely a second attempt will succeed, and the retry adds complexity. So clean this up by removing the retry and MIGRATE_PFN_LOCKED flag. Destination pages are also meant to have the MIGRATE_PFN_LOCKED flag set, but nothing actually checks that. Link: https://lkml.kernel.org/r/20211025041608.289017-1-apopple@nvidia.com Signed-off-by: Alistair Popple Reviewed-by: Ralph Campbell Acked-by: Felix Kuehling Cc: Alex Deucher Cc: Jerome Glisse Cc: John Hubbard Cc: Zi Yan Cc: Christoph Hellwig Cc: Ben Skeggs Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds