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| H A D | file.c | diff 24fa3ae9 Thu Nov 30 05:49:08 MST 2023 Christian Brauner <brauner@kernel.org> file: remove pointless wrapper Only io_uring uses __close_fd_get_file(). All it does is hide current->files but io_uring accesses files_struct directly right now anyway so it's a bit pointless. Just rename pick_file() to file_close_fd_locked() and let io_uring use it. Add a lockdep assert in there that we expect the caller to hold file_lock while we're at it. Link: https://lore.kernel.org/r/20231130-vfs-files-fixes-v1-2-e73ca6f4ea83@kernel.org Reviewed-by: Jens Axboe <axboe@kernel.dk> Reviewed-by: Jan Kara <jack@suse.cz> Signed-off-by: Christian Brauner <brauner@kernel.org> diff 61d4fb0b Tue Oct 24 16:14:37 MDT 2023 Christian Brauner <brauner@kernel.org> file, i915: fix file reference for mmap_singleton() Today we got a report at [1] for rcu stalls on the i915 testsuite in [2] due to the conversion of files to SLAB_TYPSSAFE_BY_RCU. Afaict, get_file_rcu() goes into an infinite loop trying to carefully verify that i915->gem.mmap_singleton hasn't changed - see the splat below. So I stared at this code to figure out what it actually does. It seems that the i915->gem.mmap_singleton pointer itself never had rcu semantics. The i915->gem.mmap_singleton is replaced in file->f_op->release::singleton_release(): static int singleton_release(struct inode *inode, struct file *file) { struct drm_i915_private *i915 = file->private_data; cmpxchg(&i915->gem.mmap_singleton, file, NULL); drm_dev_put(&i915->drm); return 0; } The cmpxchg() is ordered against a concurrent update of i915->gem.mmap_singleton from mmap_singleton(). IOW, when mmap_singleton() fails to get a reference on i915->gem.mmap_singleton: While mmap_singleton() does rcu_read_lock(); file = get_file_rcu(&i915->gem.mmap_singleton); rcu_read_unlock(); it allocates a new file via anon_inode_getfile() and does smp_store_mb(i915->gem.mmap_singleton, file); So, then what happens in the case of this bug is that at some point fput() is called and drops the file->f_count to zero leaving the pointer in i915->gem.mmap_singleton in tact. Now, there might be delays until file->f_op->release::singleton_release() is called and i915->gem.mmap_singleton is set to NULL. Say concurrently another task hits mmap_singleton() and does: rcu_read_lock(); file = get_file_rcu(&i915->gem.mmap_singleton); rcu_read_unlock(); When get_file_rcu() fails to get a reference via atomic_inc_not_zero() it will try the reload from i915->gem.mmap_singleton expecting it to be NULL, assuming it has comparable semantics as we expect in __fget_files_rcu(). But it hasn't so it reloads the same pointer again, trying the same atomic_inc_not_zero() again and doing so until file->f_op->release::singleton_release() of the old file has been called. So, in contrast to __fget_files_rcu() here we want to not retry when atomic_inc_not_zero() has failed. We only want to retry in case we managed to get a reference but the pointer did change on reload. <3> [511.395679] rcu: INFO: rcu_preempt detected stalls on CPUs/tasks: <3> [511.395716] rcu: Tasks blocked on level-1 rcu_node (CPUs 0-9): P6238 <3> [511.395934] rcu: (detected by 16, t=65002 jiffies, g=123977, q=439 ncpus=20) <6> [511.395944] task:i915_selftest state:R running task stack:10568 pid:6238 tgid:6238 ppid:1001 flags:0x00004002 <6> [511.395962] Call Trace: <6> [511.395966] <TASK> <6> [511.395974] ? __schedule+0x3a8/0xd70 <6> [511.395995] ? asm_sysvec_apic_timer_interrupt+0x1a/0x20 <6> [511.396003] ? lockdep_hardirqs_on+0xc3/0x140 <6> [511.396013] ? asm_sysvec_apic_timer_interrupt+0x1a/0x20 <6> [511.396029] ? get_file_rcu+0x10/0x30 <6> [511.396039] ? get_file_rcu+0x10/0x30 <6> [511.396046] ? i915_gem_object_mmap+0xbc/0x450 [i915] <6> [511.396509] ? i915_gem_mmap+0x272/0x480 [i915] <6> [511.396903] ? mmap_region+0x253/0xb60 <6> [511.396925] ? do_mmap+0x334/0x5c0 <6> [511.396939] ? vm_mmap_pgoff+0x9f/0x1c0 <6> [511.396949] ? rcu_is_watching+0x11/0x50 <6> [511.396962] ? igt_mmap_offset+0xfc/0x110 [i915] <6> [511.397376] ? __igt_mmap+0xb3/0x570 [i915] <6> [511.397762] ? igt_mmap+0x11e/0x150 [i915] <6> [511.398139] ? __trace_bprintk+0x76/0x90 <6> [511.398156] ? __i915_subtests+0xbf/0x240 [i915] <6> [511.398586] ? __pfx___i915_live_setup+0x10/0x10 [i915] <6> [511.399001] ? __pfx___i915_live_teardown+0x10/0x10 [i915] <6> [511.399433] ? __run_selftests+0xbc/0x1a0 [i915] <6> [511.399875] ? i915_live_selftests+0x4b/0x90 [i915] <6> [511.400308] ? i915_pci_probe+0x106/0x200 [i915] <6> [511.400692] ? pci_device_probe+0x95/0x120 <6> [511.400704] ? really_probe+0x164/0x3c0 <6> [511.400715] ? __pfx___driver_attach+0x10/0x10 <6> [511.400722] ? __driver_probe_device+0x73/0x160 <6> [511.400731] ? driver_probe_device+0x19/0xa0 <6> [511.400741] ? __driver_attach+0xb6/0x180 <6> [511.400749] ? __pfx___driver_attach+0x10/0x10 <6> [511.400756] ? bus_for_each_dev+0x77/0xd0 <6> [511.400770] ? bus_add_driver+0x114/0x210 <6> [511.400781] ? driver_register+0x5b/0x110 <6> [511.400791] ? i915_init+0x23/0xc0 [i915] <6> [511.401153] ? __pfx_i915_init+0x10/0x10 [i915] <6> [511.401503] ? do_one_initcall+0x57/0x270 <6> [511.401515] ? rcu_is_watching+0x11/0x50 <6> [511.401521] ? kmalloc_trace+0xa3/0xb0 <6> [511.401532] ? do_init_module+0x5f/0x210 <6> [511.401544] ? load_module+0x1d00/0x1f60 <6> [511.401581] ? init_module_from_file+0x86/0xd0 <6> [511.401590] ? init_module_from_file+0x86/0xd0 <6> [511.401613] ? idempotent_init_module+0x17c/0x230 <6> [511.401639] ? __x64_sys_finit_module+0x56/0xb0 <6> [511.401650] ? do_syscall_64+0x3c/0x90 <6> [511.401659] ? entry_SYSCALL_64_after_hwframe+0x6e/0xd8 <6> [511.401684] </TASK> Link: [1]: https://lore.kernel.org/intel-gfx/SJ1PR11MB6129CB39EED831784C331BAFB9DEA@SJ1PR11MB6129.namprd11.prod.outlook.com Link: [2]: https://intel-gfx-ci.01.org/tree/linux-next/next-20231013/bat-dg2-11/igt@i915_selftest@live@mman.html#dmesg-warnings10963 Cc: Jann Horn <jannh@google.com>, Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: https://lore.kernel.org/r/20231025-formfrage-watscheln-84526cd3bd7d@brauner Signed-off-by: Christian Brauner <brauner@kernel.org> diff 61d4fb0b Tue Oct 24 16:14:37 MDT 2023 Christian Brauner <brauner@kernel.org> file, i915: fix file reference for mmap_singleton() Today we got a report at [1] for rcu stalls on the i915 testsuite in [2] due to the conversion of files to SLAB_TYPSSAFE_BY_RCU. Afaict, get_file_rcu() goes into an infinite loop trying to carefully verify that i915->gem.mmap_singleton hasn't changed - see the splat below. So I stared at this code to figure out what it actually does. It seems that the i915->gem.mmap_singleton pointer itself never had rcu semantics. The i915->gem.mmap_singleton is replaced in file->f_op->release::singleton_release(): static int singleton_release(struct inode *inode, struct file *file) { struct drm_i915_private *i915 = file->private_data; cmpxchg(&i915->gem.mmap_singleton, file, NULL); drm_dev_put(&i915->drm); return 0; } The cmpxchg() is ordered against a concurrent update of i915->gem.mmap_singleton from mmap_singleton(). IOW, when mmap_singleton() fails to get a reference on i915->gem.mmap_singleton: While mmap_singleton() does rcu_read_lock(); file = get_file_rcu(&i915->gem.mmap_singleton); rcu_read_unlock(); it allocates a new file via anon_inode_getfile() and does smp_store_mb(i915->gem.mmap_singleton, file); So, then what happens in the case of this bug is that at some point fput() is called and drops the file->f_count to zero leaving the pointer in i915->gem.mmap_singleton in tact. Now, there might be delays until file->f_op->release::singleton_release() is called and i915->gem.mmap_singleton is set to NULL. Say concurrently another task hits mmap_singleton() and does: rcu_read_lock(); file = get_file_rcu(&i915->gem.mmap_singleton); rcu_read_unlock(); When get_file_rcu() fails to get a reference via atomic_inc_not_zero() it will try the reload from i915->gem.mmap_singleton expecting it to be NULL, assuming it has comparable semantics as we expect in __fget_files_rcu(). But it hasn't so it reloads the same pointer again, trying the same atomic_inc_not_zero() again and doing so until file->f_op->release::singleton_release() of the old file has been called. So, in contrast to __fget_files_rcu() here we want to not retry when atomic_inc_not_zero() has failed. We only want to retry in case we managed to get a reference but the pointer did change on reload. <3> [511.395679] rcu: INFO: rcu_preempt detected stalls on CPUs/tasks: <3> [511.395716] rcu: Tasks blocked on level-1 rcu_node (CPUs 0-9): P6238 <3> [511.395934] rcu: (detected by 16, t=65002 jiffies, g=123977, q=439 ncpus=20) <6> [511.395944] task:i915_selftest state:R running task stack:10568 pid:6238 tgid:6238 ppid:1001 flags:0x00004002 <6> [511.395962] Call Trace: <6> [511.395966] <TASK> <6> [511.395974] ? __schedule+0x3a8/0xd70 <6> [511.395995] ? asm_sysvec_apic_timer_interrupt+0x1a/0x20 <6> [511.396003] ? lockdep_hardirqs_on+0xc3/0x140 <6> [511.396013] ? asm_sysvec_apic_timer_interrupt+0x1a/0x20 <6> [511.396029] ? get_file_rcu+0x10/0x30 <6> [511.396039] ? get_file_rcu+0x10/0x30 <6> [511.396046] ? i915_gem_object_mmap+0xbc/0x450 [i915] <6> [511.396509] ? i915_gem_mmap+0x272/0x480 [i915] <6> [511.396903] ? mmap_region+0x253/0xb60 <6> [511.396925] ? do_mmap+0x334/0x5c0 <6> [511.396939] ? vm_mmap_pgoff+0x9f/0x1c0 <6> [511.396949] ? rcu_is_watching+0x11/0x50 <6> [511.396962] ? igt_mmap_offset+0xfc/0x110 [i915] <6> [511.397376] ? __igt_mmap+0xb3/0x570 [i915] <6> [511.397762] ? igt_mmap+0x11e/0x150 [i915] <6> [511.398139] ? __trace_bprintk+0x76/0x90 <6> [511.398156] ? __i915_subtests+0xbf/0x240 [i915] <6> [511.398586] ? __pfx___i915_live_setup+0x10/0x10 [i915] <6> [511.399001] ? __pfx___i915_live_teardown+0x10/0x10 [i915] <6> [511.399433] ? __run_selftests+0xbc/0x1a0 [i915] <6> [511.399875] ? i915_live_selftests+0x4b/0x90 [i915] <6> [511.400308] ? i915_pci_probe+0x106/0x200 [i915] <6> [511.400692] ? pci_device_probe+0x95/0x120 <6> [511.400704] ? really_probe+0x164/0x3c0 <6> [511.400715] ? __pfx___driver_attach+0x10/0x10 <6> [511.400722] ? __driver_probe_device+0x73/0x160 <6> [511.400731] ? driver_probe_device+0x19/0xa0 <6> [511.400741] ? __driver_attach+0xb6/0x180 <6> [511.400749] ? __pfx___driver_attach+0x10/0x10 <6> [511.400756] ? bus_for_each_dev+0x77/0xd0 <6> [511.400770] ? bus_add_driver+0x114/0x210 <6> [511.400781] ? driver_register+0x5b/0x110 <6> [511.400791] ? i915_init+0x23/0xc0 [i915] <6> [511.401153] ? __pfx_i915_init+0x10/0x10 [i915] <6> [511.401503] ? do_one_initcall+0x57/0x270 <6> [511.401515] ? rcu_is_watching+0x11/0x50 <6> [511.401521] ? kmalloc_trace+0xa3/0xb0 <6> [511.401532] ? do_init_module+0x5f/0x210 <6> [511.401544] ? load_module+0x1d00/0x1f60 <6> [511.401581] ? init_module_from_file+0x86/0xd0 <6> [511.401590] ? init_module_from_file+0x86/0xd0 <6> [511.401613] ? idempotent_init_module+0x17c/0x230 <6> [511.401639] ? __x64_sys_finit_module+0x56/0xb0 <6> [511.401650] ? do_syscall_64+0x3c/0x90 <6> [511.401659] ? entry_SYSCALL_64_after_hwframe+0x6e/0xd8 <6> [511.401684] </TASK> Link: [1]: https://lore.kernel.org/intel-gfx/SJ1PR11MB6129CB39EED831784C331BAFB9DEA@SJ1PR11MB6129.namprd11.prod.outlook.com Link: [2]: https://intel-gfx-ci.01.org/tree/linux-next/next-20231013/bat-dg2-11/igt@i915_selftest@live@mman.html#dmesg-warnings10963 Cc: Jann Horn <jannh@google.com>, Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: https://lore.kernel.org/r/20231025-formfrage-watscheln-84526cd3bd7d@brauner Signed-off-by: Christian Brauner <brauner@kernel.org> diff 6319194e Thu May 12 15:08:03 MDT 2022 Al Viro <viro@zeniv.linux.org.uk> Unify the primitives for file descriptor closing Currently we have 3 primitives for removing an opened file from descriptor table - pick_file(), __close_fd_get_file() and close_fd_get_file(). Their calling conventions are rather odd and there's a code duplication for no good reason. They can be unified - 1) have __range_close() cap max_fd in the very beginning; that way we don't need separate way for pick_file() to report being past the end of descriptor table. 2) make {__,}close_fd_get_file() return file (or NULL) directly, rather than returning it via struct file ** argument. Don't bother with (bogus) return value - nobody wants that -ENOENT. 3) make pick_file() return NULL on unopened descriptor - the only caller that used to care about the distinction between descriptor past the end of descriptor table and finding NULL in descriptor table doesn't give a damn after (1). 4) lift ->files_lock out of pick_file() That actually simplifies the callers, as well as the primitives themselves. Code duplication is also gone... Reviewed-by: Christian Brauner (Microsoft) <brauner@kernel.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> diff 8760c909 Fri Nov 20 16:14:38 MST 2020 Eric W. Biederman <ebiederm@xmission.com> file: Rename __close_fd to close_fd and remove the files parameter The function __close_fd was added to support binder[1]. Now that binder has been fixed to no longer need __close_fd[2] all calls to __close_fd pass current->files. Therefore transform the files parameter into a local variable initialized to current->files, and rename __close_fd to close_fd to reflect this change, and keep it in sync with the similar changes to __alloc_fd, and __fd_install. This removes the need for callers to care about the extra care that needs to be take if anything except current->files is passed, by limiting the callers to only operation on current->files. [1] 483ce1d4b8c3 ("take descriptor-related part of close() to file.c") [2] 44d8047f1d87 ("binder: use standard functions to allocate fds") Acked-by: Christian Brauner <christian.brauner@ubuntu.com> v1: https://lkml.kernel.org/r/20200817220425.9389-17-ebiederm@xmission.com Link: https://lkml.kernel.org/r/20201120231441.29911-21-ebiederm@xmission.com Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> diff 8760c909 Fri Nov 20 16:14:38 MST 2020 Eric W. Biederman <ebiederm@xmission.com> file: Rename __close_fd to close_fd and remove the files parameter The function __close_fd was added to support binder[1]. Now that binder has been fixed to no longer need __close_fd[2] all calls to __close_fd pass current->files. Therefore transform the files parameter into a local variable initialized to current->files, and rename __close_fd to close_fd to reflect this change, and keep it in sync with the similar changes to __alloc_fd, and __fd_install. This removes the need for callers to care about the extra care that needs to be take if anything except current->files is passed, by limiting the callers to only operation on current->files. [1] 483ce1d4b8c3 ("take descriptor-related part of close() to file.c") [2] 44d8047f1d87 ("binder: use standard functions to allocate fds") Acked-by: Christian Brauner <christian.brauner@ubuntu.com> v1: https://lkml.kernel.org/r/20200817220425.9389-17-ebiederm@xmission.com Link: https://lkml.kernel.org/r/20201120231441.29911-21-ebiederm@xmission.com Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> diff aa384d10 Fri Nov 20 16:14:37 MST 2020 Eric W. Biederman <ebiederm@xmission.com> file: Merge __alloc_fd into alloc_fd The function __alloc_fd was added to support binder[1]. With binder fixed[2] there are no more users. As alloc_fd just calls __alloc_fd with "files=current->files", merge them together by transforming the files parameter into a local variable initialized to current->files. [1] dcfadfa4ec5a ("new helper: __alloc_fd()") [2] 44d8047f1d87 ("binder: use standard functions to allocate fds") Acked-by: Christian Brauner <christian.brauner@ubuntu.com> v1: https://lkml.kernel.org/r/20200817220425.9389-16-ebiederm@xmission.com Link: https://lkml.kernel.org/r/20201120231441.29911-20-ebiederm@xmission.com Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> diff aa384d10 Fri Nov 20 16:14:37 MST 2020 Eric W. Biederman <ebiederm@xmission.com> file: Merge __alloc_fd into alloc_fd The function __alloc_fd was added to support binder[1]. With binder fixed[2] there are no more users. As alloc_fd just calls __alloc_fd with "files=current->files", merge them together by transforming the files parameter into a local variable initialized to current->files. [1] dcfadfa4ec5a ("new helper: __alloc_fd()") [2] 44d8047f1d87 ("binder: use standard functions to allocate fds") Acked-by: Christian Brauner <christian.brauner@ubuntu.com> v1: https://lkml.kernel.org/r/20200817220425.9389-16-ebiederm@xmission.com Link: https://lkml.kernel.org/r/20201120231441.29911-20-ebiederm@xmission.com Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> diff d74ba04d Fri Nov 20 16:14:35 MST 2020 Eric W. Biederman <ebiederm@xmission.com> file: Merge __fd_install into fd_install The function __fd_install was added to support binder[1]. With binder fixed[2] there are no more users. As fd_install just calls __fd_install with "files=current->files", merge them together by transforming the files parameter into a local variable initialized to current->files. [1] f869e8a7f753 ("expose a low-level variant of fd_install() for binder") [2] 44d8047f1d87 ("binder: use standard functions to allocate fds") Acked-by: Christian Brauner <christian.brauner@ubuntu.com> v1:https://lkml.kernel.org/r/20200817220425.9389-14-ebiederm@xmission.com Link: https://lkml.kernel.org/r/20201120231441.29911-18-ebiederm@xmission.com Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> diff d74ba04d Fri Nov 20 16:14:35 MST 2020 Eric W. Biederman <ebiederm@xmission.com> file: Merge __fd_install into fd_install The function __fd_install was added to support binder[1]. With binder fixed[2] there are no more users. As fd_install just calls __fd_install with "files=current->files", merge them together by transforming the files parameter into a local variable initialized to current->files. [1] f869e8a7f753 ("expose a low-level variant of fd_install() for binder") [2] 44d8047f1d87 ("binder: use standard functions to allocate fds") Acked-by: Christian Brauner <christian.brauner@ubuntu.com> v1:https://lkml.kernel.org/r/20200817220425.9389-14-ebiederm@xmission.com Link: https://lkml.kernel.org/r/20201120231441.29911-18-ebiederm@xmission.com Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> |
| H A D | open.c | diff 5f0d594c Fri Feb 02 05:17:23 MST 2024 Tony Solomonik <tony.solomonik@gmail.com> Add do_ftruncate that truncates a struct file do_sys_ftruncate receives a file descriptor, fgets the struct file, and finally actually truncates the file. do_ftruncate allows for passing in a file directly, with the caller already holding a reference to it. Signed-off-by: Tony Solomonik <tony.solomonik@gmail.com> Reviewed-by: Christian Brauner <brauner@kernel.org> Link: https://lore.kernel.org/r/20240202121724.17461-2-tony.solomonik@gmail.com Signed-off-by: Jens Axboe <axboe@kernel.dk> diff 83bc1d29 Mon Oct 09 09:37:10 MDT 2023 Amir Goldstein <amir73il@gmail.com> fs: get mnt_writers count for an open backing file's real path A writeable mapped backing file can perform writes to the real inode. Therefore, the real path mount must be kept writable so long as the writable map exists. This may not be strictly needed for ovelrayfs private upper mount, but it is correct to take the mnt_writers count in the vfs helper. Signed-off-by: Amir Goldstein <amir73il@gmail.com> Link: https://lore.kernel.org/r/20231009153712.1566422-2-amir73il@gmail.com Signed-off-by: Christian Brauner <brauner@kernel.org> diff 3e15dcf7 Fri Sep 08 07:28:59 MDT 2023 Amir Goldstein <amir73il@gmail.com> fs: rename __mnt_{want,drop}_write*() helpers Before exporting these helpers to modules, make their names more meaningful. The names mnt_{get,put)_write_access*() were chosen, because they rhyme with the inode {get,put)_write_access() helpers, which have a very close meaning for the inode object. Suggested-by: Christian Brauner <brauner@kernel.org> Link: https://lore.kernel.org/r/20230817-anfechtbar-ruhelosigkeit-8c6cca8443fc@brauner/ Signed-off-by: Amir Goldstein <amir73il@gmail.com> Message-Id: <20230908132900.2983519-2-amir73il@gmail.com> Signed-off-by: Christian Brauner <brauner@kernel.org> diff 021a160a Tue Aug 08 11:26:35 MDT 2023 Linus Torvalds <torvalds@linux-foundation.org> fs: use __fput_sync in close(2) close(2) is a special case which guarantees a shallow kernel stack, making delegation to task_work machinery unnecessary. Said delegation is problematic as it involves atomic ops and interrupt masking trips, none of which are cheap on x86-64. Forcing close(2) to do it looks like an oversight in the original work. Moreover presence of CONFIG_RSEQ adds an additional overhead as fput() -> task_work_add(..., TWA_RESUME) -> set_notify_resume() makes the thread returning to userspace land in resume_user_mode_work(), where rseq_handle_notify_resume takes a SMAP round-trip if rseq is enabled for the thread (and it is by default with contemporary glibc). Sample result when benchmarking open1_processes -t 1 from will-it-scale (that's an open + close loop) + tmpfs on /tmp, running on the Sapphire Rapid CPU (ops/s): stock+RSEQ: 1329857 stock-RSEQ: 1421667 (+7%) patched: 1523521 (+14.5% / +7%) (with / without rseq) Patched result is the same regardless of rseq as the codepath is avoided. Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Christian Brauner <brauner@kernel.org> diff 021a160a Tue Aug 08 11:26:35 MDT 2023 Linus Torvalds <torvalds@linux-foundation.org> fs: use __fput_sync in close(2) close(2) is a special case which guarantees a shallow kernel stack, making delegation to task_work machinery unnecessary. Said delegation is problematic as it involves atomic ops and interrupt masking trips, none of which are cheap on x86-64. Forcing close(2) to do it looks like an oversight in the original work. Moreover presence of CONFIG_RSEQ adds an additional overhead as fput() -> task_work_add(..., TWA_RESUME) -> set_notify_resume() makes the thread returning to userspace land in resume_user_mode_work(), where rseq_handle_notify_resume takes a SMAP round-trip if rseq is enabled for the thread (and it is by default with contemporary glibc). Sample result when benchmarking open1_processes -t 1 from will-it-scale (that's an open + close loop) + tmpfs on /tmp, running on the Sapphire Rapid CPU (ops/s): stock+RSEQ: 1329857 stock-RSEQ: 1421667 (+7%) patched: 1523521 (+14.5% / +7%) (with / without rseq) Patched result is the same regardless of rseq as the codepath is avoided. Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Christian Brauner <brauner@kernel.org> diff 021a160a Tue Aug 08 11:26:35 MDT 2023 Linus Torvalds <torvalds@linux-foundation.org> fs: use __fput_sync in close(2) close(2) is a special case which guarantees a shallow kernel stack, making delegation to task_work machinery unnecessary. Said delegation is problematic as it involves atomic ops and interrupt masking trips, none of which are cheap on x86-64. Forcing close(2) to do it looks like an oversight in the original work. Moreover presence of CONFIG_RSEQ adds an additional overhead as fput() -> task_work_add(..., TWA_RESUME) -> set_notify_resume() makes the thread returning to userspace land in resume_user_mode_work(), where rseq_handle_notify_resume takes a SMAP round-trip if rseq is enabled for the thread (and it is by default with contemporary glibc). Sample result when benchmarking open1_processes -t 1 from will-it-scale (that's an open + close loop) + tmpfs on /tmp, running on the Sapphire Rapid CPU (ops/s): stock+RSEQ: 1329857 stock-RSEQ: 1421667 (+7%) patched: 1523521 (+14.5% / +7%) (with / without rseq) Patched result is the same regardless of rseq as the codepath is avoided. Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Christian Brauner <brauner@kernel.org> diff 5daeb41a Fri Jul 28 05:58:26 MDT 2023 Aleksa Sarai <cyphar@cyphar.com> fchmodat2: add support for AT_EMPTY_PATH This allows userspace to avoid going through /proc/self/fd when dealing with all types of file descriptors for chmod(), and makes fchmodat2() a proper superset of all other chmod syscalls. The primary difference between fchmodat2(AT_EMPTY_PATH) and fchmod() is that fchmod() doesn't operate on O_PATH file descriptors by design. To quote open(2): > O_PATH (since Linux 2.6.39) > [...] > The file itself is not opened, and other file operations (e.g., > read(2), write(2), fchmod(2), fchown(2), fgetxattr(2), ioctl(2), > mmap(2)) fail with the error EBADF. However, procfs has allowed userspace to do this operation ever since the introduction of O_PATH through magic-links, so adding this feature is only an improvement for programs that have to mess around with /proc/self/fd/$n today to get this behaviour. In addition, fchownat(AT_EMPTY_PATH) has existed since the introduction of O_PATH and allows chown() operations directly on O_PATH descriptors. Signed-off-by: Aleksa Sarai <cyphar@cyphar.com> Acked-by: Alexey Gladkov <legion@kernel.org> Message-Id: <20230728-fchmodat2-at_empty_path-v1-1-f3add31d3516@cyphar.com> Signed-off-by: Christian Brauner <brauner@kernel.org> diff 5daeb41a Fri Jul 28 05:58:26 MDT 2023 Aleksa Sarai <cyphar@cyphar.com> fchmodat2: add support for AT_EMPTY_PATH This allows userspace to avoid going through /proc/self/fd when dealing with all types of file descriptors for chmod(), and makes fchmodat2() a proper superset of all other chmod syscalls. The primary difference between fchmodat2(AT_EMPTY_PATH) and fchmod() is that fchmod() doesn't operate on O_PATH file descriptors by design. To quote open(2): > O_PATH (since Linux 2.6.39) > [...] > The file itself is not opened, and other file operations (e.g., > read(2), write(2), fchmod(2), fchown(2), fgetxattr(2), ioctl(2), > mmap(2)) fail with the error EBADF. However, procfs has allowed userspace to do this operation ever since the introduction of O_PATH through magic-links, so adding this feature is only an improvement for programs that have to mess around with /proc/self/fd/$n today to get this behaviour. In addition, fchownat(AT_EMPTY_PATH) has existed since the introduction of O_PATH and allows chown() operations directly on O_PATH descriptors. Signed-off-by: Aleksa Sarai <cyphar@cyphar.com> Acked-by: Alexey Gladkov <legion@kernel.org> Message-Id: <20230728-fchmodat2-at_empty_path-v1-1-f3add31d3516@cyphar.com> Signed-off-by: Christian Brauner <brauner@kernel.org> diff 5daeb41a Fri Jul 28 05:58:26 MDT 2023 Aleksa Sarai <cyphar@cyphar.com> fchmodat2: add support for AT_EMPTY_PATH This allows userspace to avoid going through /proc/self/fd when dealing with all types of file descriptors for chmod(), and makes fchmodat2() a proper superset of all other chmod syscalls. The primary difference between fchmodat2(AT_EMPTY_PATH) and fchmod() is that fchmod() doesn't operate on O_PATH file descriptors by design. To quote open(2): > O_PATH (since Linux 2.6.39) > [...] > The file itself is not opened, and other file operations (e.g., > read(2), write(2), fchmod(2), fchown(2), fgetxattr(2), ioctl(2), > mmap(2)) fail with the error EBADF. However, procfs has allowed userspace to do this operation ever since the introduction of O_PATH through magic-links, so adding this feature is only an improvement for programs that have to mess around with /proc/self/fd/$n today to get this behaviour. In addition, fchownat(AT_EMPTY_PATH) has existed since the introduction of O_PATH and allows chown() operations directly on O_PATH descriptors. Signed-off-by: Aleksa Sarai <cyphar@cyphar.com> Acked-by: Alexey Gladkov <legion@kernel.org> Message-Id: <20230728-fchmodat2-at_empty_path-v1-1-f3add31d3516@cyphar.com> Signed-off-by: Christian Brauner <brauner@kernel.org> diff 5daeb41a Fri Jul 28 05:58:26 MDT 2023 Aleksa Sarai <cyphar@cyphar.com> fchmodat2: add support for AT_EMPTY_PATH This allows userspace to avoid going through /proc/self/fd when dealing with all types of file descriptors for chmod(), and makes fchmodat2() a proper superset of all other chmod syscalls. The primary difference between fchmodat2(AT_EMPTY_PATH) and fchmod() is that fchmod() doesn't operate on O_PATH file descriptors by design. To quote open(2): > O_PATH (since Linux 2.6.39) > [...] > The file itself is not opened, and other file operations (e.g., > read(2), write(2), fchmod(2), fchown(2), fgetxattr(2), ioctl(2), > mmap(2)) fail with the error EBADF. However, procfs has allowed userspace to do this operation ever since the introduction of O_PATH through magic-links, so adding this feature is only an improvement for programs that have to mess around with /proc/self/fd/$n today to get this behaviour. In addition, fchownat(AT_EMPTY_PATH) has existed since the introduction of O_PATH and allows chown() operations directly on O_PATH descriptors. Signed-off-by: Aleksa Sarai <cyphar@cyphar.com> Acked-by: Alexey Gladkov <legion@kernel.org> Message-Id: <20230728-fchmodat2-at_empty_path-v1-1-f3add31d3516@cyphar.com> Signed-off-by: Christian Brauner <brauner@kernel.org> diff 5daeb41a Fri Jul 28 05:58:26 MDT 2023 Aleksa Sarai <cyphar@cyphar.com> fchmodat2: add support for AT_EMPTY_PATH This allows userspace to avoid going through /proc/self/fd when dealing with all types of file descriptors for chmod(), and makes fchmodat2() a proper superset of all other chmod syscalls. The primary difference between fchmodat2(AT_EMPTY_PATH) and fchmod() is that fchmod() doesn't operate on O_PATH file descriptors by design. To quote open(2): > O_PATH (since Linux 2.6.39) > [...] > The file itself is not opened, and other file operations (e.g., > read(2), write(2), fchmod(2), fchown(2), fgetxattr(2), ioctl(2), > mmap(2)) fail with the error EBADF. However, procfs has allowed userspace to do this operation ever since the introduction of O_PATH through magic-links, so adding this feature is only an improvement for programs that have to mess around with /proc/self/fd/$n today to get this behaviour. In addition, fchownat(AT_EMPTY_PATH) has existed since the introduction of O_PATH and allows chown() operations directly on O_PATH descriptors. Signed-off-by: Aleksa Sarai <cyphar@cyphar.com> Acked-by: Alexey Gladkov <legion@kernel.org> Message-Id: <20230728-fchmodat2-at_empty_path-v1-1-f3add31d3516@cyphar.com> Signed-off-by: Christian Brauner <brauner@kernel.org> diff 5daeb41a Fri Jul 28 05:58:26 MDT 2023 Aleksa Sarai <cyphar@cyphar.com> fchmodat2: add support for AT_EMPTY_PATH This allows userspace to avoid going through /proc/self/fd when dealing with all types of file descriptors for chmod(), and makes fchmodat2() a proper superset of all other chmod syscalls. The primary difference between fchmodat2(AT_EMPTY_PATH) and fchmod() is that fchmod() doesn't operate on O_PATH file descriptors by design. To quote open(2): > O_PATH (since Linux 2.6.39) > [...] > The file itself is not opened, and other file operations (e.g., > read(2), write(2), fchmod(2), fchown(2), fgetxattr(2), ioctl(2), > mmap(2)) fail with the error EBADF. However, procfs has allowed userspace to do this operation ever since the introduction of O_PATH through magic-links, so adding this feature is only an improvement for programs that have to mess around with /proc/self/fd/$n today to get this behaviour. In addition, fchownat(AT_EMPTY_PATH) has existed since the introduction of O_PATH and allows chown() operations directly on O_PATH descriptors. Signed-off-by: Aleksa Sarai <cyphar@cyphar.com> Acked-by: Alexey Gladkov <legion@kernel.org> Message-Id: <20230728-fchmodat2-at_empty_path-v1-1-f3add31d3516@cyphar.com> Signed-off-by: Christian Brauner <brauner@kernel.org> diff 5daeb41a Fri Jul 28 05:58:26 MDT 2023 Aleksa Sarai <cyphar@cyphar.com> fchmodat2: add support for AT_EMPTY_PATH This allows userspace to avoid going through /proc/self/fd when dealing with all types of file descriptors for chmod(), and makes fchmodat2() a proper superset of all other chmod syscalls. The primary difference between fchmodat2(AT_EMPTY_PATH) and fchmod() is that fchmod() doesn't operate on O_PATH file descriptors by design. To quote open(2): > O_PATH (since Linux 2.6.39) > [...] > The file itself is not opened, and other file operations (e.g., > read(2), write(2), fchmod(2), fchown(2), fgetxattr(2), ioctl(2), > mmap(2)) fail with the error EBADF. However, procfs has allowed userspace to do this operation ever since the introduction of O_PATH through magic-links, so adding this feature is only an improvement for programs that have to mess around with /proc/self/fd/$n today to get this behaviour. In addition, fchownat(AT_EMPTY_PATH) has existed since the introduction of O_PATH and allows chown() operations directly on O_PATH descriptors. Signed-off-by: Aleksa Sarai <cyphar@cyphar.com> Acked-by: Alexey Gladkov <legion@kernel.org> Message-Id: <20230728-fchmodat2-at_empty_path-v1-1-f3add31d3516@cyphar.com> Signed-off-by: Christian Brauner <brauner@kernel.org> diff 5daeb41a Fri Jul 28 05:58:26 MDT 2023 Aleksa Sarai <cyphar@cyphar.com> fchmodat2: add support for AT_EMPTY_PATH This allows userspace to avoid going through /proc/self/fd when dealing with all types of file descriptors for chmod(), and makes fchmodat2() a proper superset of all other chmod syscalls. The primary difference between fchmodat2(AT_EMPTY_PATH) and fchmod() is that fchmod() doesn't operate on O_PATH file descriptors by design. To quote open(2): > O_PATH (since Linux 2.6.39) > [...] > The file itself is not opened, and other file operations (e.g., > read(2), write(2), fchmod(2), fchown(2), fgetxattr(2), ioctl(2), > mmap(2)) fail with the error EBADF. However, procfs has allowed userspace to do this operation ever since the introduction of O_PATH through magic-links, so adding this feature is only an improvement for programs that have to mess around with /proc/self/fd/$n today to get this behaviour. In addition, fchownat(AT_EMPTY_PATH) has existed since the introduction of O_PATH and allows chown() operations directly on O_PATH descriptors. Signed-off-by: Aleksa Sarai <cyphar@cyphar.com> Acked-by: Alexey Gladkov <legion@kernel.org> Message-Id: <20230728-fchmodat2-at_empty_path-v1-1-f3add31d3516@cyphar.com> Signed-off-by: Christian Brauner <brauner@kernel.org> |
| /linux-master/include/linux/ | ||
| H A D | fs.h | diff 2824083d Tue Feb 20 22:14:03 MST 2024 Gabriel Krisman Bertazi <krisman@suse.de> ovl: Always reject mounting over case-insensitive directories overlayfs relies on the filesystem setting DCACHE_OP_HASH or DCACHE_OP_COMPARE to reject mounting over case-insensitive directories. Since commit bb9cd9106b22 ("fscrypt: Have filesystems handle their d_ops"), we set ->d_op through a hook in ->d_lookup, which means the root dentry won't have them, causing the mount to accidentally succeed. In v6.7-rc7, the following sequence will succeed to mount, but any dentry other than the root dentry will be a "weird" dentry to ovl and fail with EREMOTE. mkfs.ext4 -O casefold lower.img mount -O loop lower.img lower mount -t overlay -o lowerdir=lower,upperdir=upper,workdir=work ovl /mnt Mounting on a subdirectory fails, as expected, because DCACHE_OP_HASH and DCACHE_OP_COMPARE are properly set by ->lookup. Fix by explicitly rejecting superblocks that allow case-insensitive dentries. Yes, this will be solved when we move d_op configuration back to ->s_d_op. Yet, we better have an explicit fix to avoid messing up again. While there, re-sort the entries to have more descriptive error messages first. Fixes: bb9cd9106b22 ("fscrypt: Have filesystems handle their d_ops") Acked-by: Amir Goldstein <amir73il@gmail.com> Reviewed-by: Eric Biggers <ebiggers@google.com> Link: https://lore.kernel.org/r/20240221171412.10710-2-krisman@suse.de Signed-off-by: Gabriel Krisman Bertazi <krisman@suse.de> diff a4af51ce Tue Feb 06 19:56:15 MST 2024 Kent Overstreet <kent.overstreet@linux.dev> fs: super_set_uuid() Some weird old filesytems have UUID-like things that we wish to expose as UUIDs, but are smaller; add a length field so that the new FS_IOC_(GET|SET)UUID ioctls can handle them in generic code. And add a helper super_set_uuid(), for setting nonstandard length uuids. Helper is now required for the new FS_IOC_GETUUID ioctl; if super_set_uuid() hasn't been called, the ioctl won't be supported. Reviewed-by: Dave Chinner <dchinner@redhat.com> Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev> Link: https://lore.kernel.org/r/20240207025624.1019754-2-kent.overstreet@linux.dev Signed-off-by: Christian Brauner <brauner@kernel.org> diff 3058fca1 Fri Feb 02 04:01:31 MST 2024 Amir Goldstein <amir73il@gmail.com> fs: make file_dentry() a simple accessor file_dentry() is a relic from the days that overlayfs was using files with a "fake" path, meaning, f_path on overlayfs and f_inode on underlying fs. In those days, file_dentry() was needed to get the underlying fs dentry that matches f_inode. Files with "fake" path should not exist nowadays, so make file_dentry() a simple accessor and use an assertion to make sure that file_dentry() was not papering over filesystem bugs. Signed-off-by: Amir Goldstein <amir73il@gmail.com> Link: https://lore.kernel.org/r/20240202110132.1584111-2-amir73il@gmail.com Tested-by: Stefan Berger <stefanb@linux.ibm.com> Signed-off-by: Christian Brauner <brauner@kernel.org> diff d3b1a9a7 Fri Feb 02 01:33:04 MST 2024 JonasZhou <JonasZhou@zhaoxin.com> fs/address_space: move i_mmap_rwsem to mitigate a false sharing with i_mmap. In the struct address_space, there is a 32-byte gap between i_mmap and i_mmap_rwsem. Due to the alignment of struct address_space variables to 8 bytes, in certain situations, i_mmap and i_mmap_rwsem may end up in the same CACHE line. While running Unixbench/execl, we observe high false sharing issues when accessing i_mmap against i_mmap_rwsem. We move i_mmap_rwsem after i_private_list, ensuring a 64-byte gap between i_mmap and i_mmap_rwsem. For Intel Silver machines (2 sockets) using kernel v6.8 rc-2, the score of Unixbench/execl improves by ~3.94%, and the score of Unixbench/shell improves by ~3.26%. Baseline: ------------------------------------------------------------- 162 546 748 11374 21 0xffff92e266af90c0 ------------------------------------------------------------- 46.89% 44.65% 0.00% 0.00% 0x0 1 1 0xffffffff86d5fb96 460 258 271 1069 32 [k] __handle_mm_fault [kernel.vmlinux] memory.c:2940 0 1 4.21% 4.41% 0.00% 0.00% 0x4 1 1 0xffffffff86d0ed54 473 311 288 95 28 [k] filemap_read [kernel.vmlinux] atomic.h:23 0 1 0.00% 0.00% 0.04% 4.76% 0x8 1 1 0xffffffff86d4bcf1 0 0 0 5 4 [k] vma_interval_tree_remove [kernel.vmlinux] rbtree_augmented.h:204 0 1 6.41% 6.02% 0.00% 0.00% 0x8 1 1 0xffffffff86d4ba85 411 271 339 210 32 [k] vma_interval_tree_insert [kernel.vmlinux] interval_tree.c:23 0 1 0.00% 0.00% 0.47% 95.24% 0x10 1 1 0xffffffff86d4bd34 0 0 0 74 32 [k] vma_interval_tree_remove [kernel.vmlinux] rbtree_augmented.h:339 0 1 0.37% 0.13% 0.00% 0.00% 0x10 1 1 0xffffffff86d4bb4f 328 212 380 7 5 [k] vma_interval_tree_remove [kernel.vmlinux] rbtree_augmented.h:338 0 1 5.13% 5.08% 0.00% 0.00% 0x10 1 1 0xffffffff86d4bb4b 416 255 357 197 32 [k] vma_interval_tree_remove [kernel.vmlinux] rbtree_augmented.h:338 0 1 1.10% 0.53% 0.00% 0.00% 0x28 1 1 0xffffffff86e06eb8 395 228 351 24 14 [k] do_dentry_open [kernel.vmlinux] open.c:966 0 1 1.10% 2.14% 57.07% 0.00% 0x38 1 1 0xffffffff878c9225 1364 792 462 7003 32 [k] down_write [kernel.vmlinux] atomic64_64.h:109 0 1 0.00% 0.00% 0.01% 0.00% 0x38 1 1 0xffffffff878c8e75 0 0 252 3 2 [k] rwsem_down_write_slowpath [kernel.vmlinux] atomic64_64.h:109 0 1 0.00% 0.13% 0.00% 0.00% 0x38 1 1 0xffffffff878c8e23 0 596 63 2 2 [k] rwsem_down_write_slowpath [kernel.vmlinux] atomic64_64.h:15 0 1 2.38% 2.94% 6.53% 0.00% 0x38 1 1 0xffffffff878c8ccb 1150 818 570 1197 32 [k] rwsem_down_write_slowpath [kernel.vmlinux] atomic64_64.h:109 0 1 30.59% 32.22% 0.00% 0.00% 0x38 1 1 0xffffffff878c8cb4 423 251 380 648 32 [k] rwsem_down_write_slowpath [kernel.vmlinux] atomic64_64.h:15 0 1 1.83% 1.74% 35.88% 0.00% 0x38 1 1 0xffffffff86b4f833 1217 1112 565 4586 32 [k] up_write [kernel.vmlinux] atomic64_64.h:91 0 1 with this change: ------------------------------------------------------------- 360 12 300 57 35 0xffff982cdae76400 ------------------------------------------------------------- 50.00% 59.67% 0.00% 0.00% 0x0 1 1 0xffffffff8215fb86 352 200 191 558 32 [k] __handle_mm_fault [kernel.vmlinux] memory.c:2940 0 1 8.33% 5.00% 0.00% 0.00% 0x4 1 1 0xffffffff8210ed44 370 284 263 42 24 [k] filemap_read [kernel.vmlinux] atomic.h:23 0 1 0.00% 0.00% 5.26% 2.86% 0x8 1 1 0xffffffff8214bce1 0 0 0 4 4 [k] vma_interval_tree_remove [kernel.vmlinux] rbtree_augmented.h:204 0 1 33.33% 14.33% 0.00% 0.00% 0x8 1 1 0xffffffff8214ba75 344 186 219 140 32 [k] vma_interval_tree_insert [kernel.vmlinux] interval_tree.c:23 0 1 0.00% 0.00% 94.74% 97.14% 0x10 1 1 0xffffffff8214bd24 0 0 0 88 29 [k] vma_interval_tree_remove [kernel.vmlinux] rbtree_augmented.h:339 0 1 8.33% 20.00% 0.00% 0.00% 0x10 1 1 0xffffffff8214bb3b 296 209 226 167 31 [k] vma_interval_tree_remove [kernel.vmlinux] rbtree_augmented.h:338 0 1 0.00% 0.67% 0.00% 0.00% 0x28 1 1 0xffffffff82206f45 0 140 334 4 3 [k] do_dentry_open [kernel.vmlinux] open.c:966 0 1 0.00% 0.33% 0.00% 0.00% 0x38 1 1 0xffffffff8250a6c4 0 286 126 5 5 [k] errseq_sample [kernel.vmlinux] errseq.c:125 0 Signed-off-by: JonasZhou <JonasZhou@zhaoxin.com> Link: https://lore.kernel.org/r/20240202083304.10995-1-JonasZhou-oc@zhaoxin.com Signed-off-by: Christian Brauner <brauner@kernel.org> diff d3b1a9a7 Fri Feb 02 01:33:04 MST 2024 JonasZhou <JonasZhou@zhaoxin.com> fs/address_space: move i_mmap_rwsem to mitigate a false sharing with i_mmap. In the struct address_space, there is a 32-byte gap between i_mmap and i_mmap_rwsem. Due to the alignment of struct address_space variables to 8 bytes, in certain situations, i_mmap and i_mmap_rwsem may end up in the same CACHE line. While running Unixbench/execl, we observe high false sharing issues when accessing i_mmap against i_mmap_rwsem. We move i_mmap_rwsem after i_private_list, ensuring a 64-byte gap between i_mmap and i_mmap_rwsem. For Intel Silver machines (2 sockets) using kernel v6.8 rc-2, the score of Unixbench/execl improves by ~3.94%, and the score of Unixbench/shell improves by ~3.26%. Baseline: ------------------------------------------------------------- 162 546 748 11374 21 0xffff92e266af90c0 ------------------------------------------------------------- 46.89% 44.65% 0.00% 0.00% 0x0 1 1 0xffffffff86d5fb96 460 258 271 1069 32 [k] __handle_mm_fault [kernel.vmlinux] memory.c:2940 0 1 4.21% 4.41% 0.00% 0.00% 0x4 1 1 0xffffffff86d0ed54 473 311 288 95 28 [k] filemap_read [kernel.vmlinux] atomic.h:23 0 1 0.00% 0.00% 0.04% 4.76% 0x8 1 1 0xffffffff86d4bcf1 0 0 0 5 4 [k] vma_interval_tree_remove [kernel.vmlinux] rbtree_augmented.h:204 0 1 6.41% 6.02% 0.00% 0.00% 0x8 1 1 0xffffffff86d4ba85 411 271 339 210 32 [k] vma_interval_tree_insert [kernel.vmlinux] interval_tree.c:23 0 1 0.00% 0.00% 0.47% 95.24% 0x10 1 1 0xffffffff86d4bd34 0 0 0 74 32 [k] vma_interval_tree_remove [kernel.vmlinux] rbtree_augmented.h:339 0 1 0.37% 0.13% 0.00% 0.00% 0x10 1 1 0xffffffff86d4bb4f 328 212 380 7 5 [k] vma_interval_tree_remove [kernel.vmlinux] rbtree_augmented.h:338 0 1 5.13% 5.08% 0.00% 0.00% 0x10 1 1 0xffffffff86d4bb4b 416 255 357 197 32 [k] vma_interval_tree_remove [kernel.vmlinux] rbtree_augmented.h:338 0 1 1.10% 0.53% 0.00% 0.00% 0x28 1 1 0xffffffff86e06eb8 395 228 351 24 14 [k] do_dentry_open [kernel.vmlinux] open.c:966 0 1 1.10% 2.14% 57.07% 0.00% 0x38 1 1 0xffffffff878c9225 1364 792 462 7003 32 [k] down_write [kernel.vmlinux] atomic64_64.h:109 0 1 0.00% 0.00% 0.01% 0.00% 0x38 1 1 0xffffffff878c8e75 0 0 252 3 2 [k] rwsem_down_write_slowpath [kernel.vmlinux] atomic64_64.h:109 0 1 0.00% 0.13% 0.00% 0.00% 0x38 1 1 0xffffffff878c8e23 0 596 63 2 2 [k] rwsem_down_write_slowpath [kernel.vmlinux] atomic64_64.h:15 0 1 2.38% 2.94% 6.53% 0.00% 0x38 1 1 0xffffffff878c8ccb 1150 818 570 1197 32 [k] rwsem_down_write_slowpath [kernel.vmlinux] atomic64_64.h:109 0 1 30.59% 32.22% 0.00% 0.00% 0x38 1 1 0xffffffff878c8cb4 423 251 380 648 32 [k] rwsem_down_write_slowpath [kernel.vmlinux] atomic64_64.h:15 0 1 1.83% 1.74% 35.88% 0.00% 0x38 1 1 0xffffffff86b4f833 1217 1112 565 4586 32 [k] up_write [kernel.vmlinux] atomic64_64.h:91 0 1 with this change: ------------------------------------------------------------- 360 12 300 57 35 0xffff982cdae76400 ------------------------------------------------------------- 50.00% 59.67% 0.00% 0.00% 0x0 1 1 0xffffffff8215fb86 352 200 191 558 32 [k] __handle_mm_fault [kernel.vmlinux] memory.c:2940 0 1 8.33% 5.00% 0.00% 0.00% 0x4 1 1 0xffffffff8210ed44 370 284 263 42 24 [k] filemap_read [kernel.vmlinux] atomic.h:23 0 1 0.00% 0.00% 5.26% 2.86% 0x8 1 1 0xffffffff8214bce1 0 0 0 4 4 [k] vma_interval_tree_remove [kernel.vmlinux] rbtree_augmented.h:204 0 1 33.33% 14.33% 0.00% 0.00% 0x8 1 1 0xffffffff8214ba75 344 186 219 140 32 [k] vma_interval_tree_insert [kernel.vmlinux] interval_tree.c:23 0 1 0.00% 0.00% 94.74% 97.14% 0x10 1 1 0xffffffff8214bd24 0 0 0 88 29 [k] vma_interval_tree_remove [kernel.vmlinux] rbtree_augmented.h:339 0 1 8.33% 20.00% 0.00% 0.00% 0x10 1 1 0xffffffff8214bb3b 296 209 226 167 31 [k] vma_interval_tree_remove [kernel.vmlinux] rbtree_augmented.h:338 0 1 0.00% 0.67% 0.00% 0.00% 0x28 1 1 0xffffffff82206f45 0 140 334 4 3 [k] do_dentry_open [kernel.vmlinux] open.c:966 0 1 0.00% 0.33% 0.00% 0.00% 0x38 1 1 0xffffffff8250a6c4 0 286 126 5 5 [k] errseq_sample [kernel.vmlinux] errseq.c:125 0 Signed-off-by: JonasZhou <JonasZhou@zhaoxin.com> Link: https://lore.kernel.org/r/20240202083304.10995-1-JonasZhou-oc@zhaoxin.com Signed-off-by: Christian Brauner <brauner@kernel.org> diff d3b1a9a7 Fri Feb 02 01:33:04 MST 2024 JonasZhou <JonasZhou@zhaoxin.com> fs/address_space: move i_mmap_rwsem to mitigate a false sharing with i_mmap. In the struct address_space, there is a 32-byte gap between i_mmap and i_mmap_rwsem. Due to the alignment of struct address_space variables to 8 bytes, in certain situations, i_mmap and i_mmap_rwsem may end up in the same CACHE line. While running Unixbench/execl, we observe high false sharing issues when accessing i_mmap against i_mmap_rwsem. We move i_mmap_rwsem after i_private_list, ensuring a 64-byte gap between i_mmap and i_mmap_rwsem. For Intel Silver machines (2 sockets) using kernel v6.8 rc-2, the score of Unixbench/execl improves by ~3.94%, and the score of Unixbench/shell improves by ~3.26%. Baseline: ------------------------------------------------------------- 162 546 748 11374 21 0xffff92e266af90c0 ------------------------------------------------------------- 46.89% 44.65% 0.00% 0.00% 0x0 1 1 0xffffffff86d5fb96 460 258 271 1069 32 [k] __handle_mm_fault [kernel.vmlinux] memory.c:2940 0 1 4.21% 4.41% 0.00% 0.00% 0x4 1 1 0xffffffff86d0ed54 473 311 288 95 28 [k] filemap_read [kernel.vmlinux] atomic.h:23 0 1 0.00% 0.00% 0.04% 4.76% 0x8 1 1 0xffffffff86d4bcf1 0 0 0 5 4 [k] vma_interval_tree_remove [kernel.vmlinux] rbtree_augmented.h:204 0 1 6.41% 6.02% 0.00% 0.00% 0x8 1 1 0xffffffff86d4ba85 411 271 339 210 32 [k] vma_interval_tree_insert [kernel.vmlinux] interval_tree.c:23 0 1 0.00% 0.00% 0.47% 95.24% 0x10 1 1 0xffffffff86d4bd34 0 0 0 74 32 [k] vma_interval_tree_remove [kernel.vmlinux] rbtree_augmented.h:339 0 1 0.37% 0.13% 0.00% 0.00% 0x10 1 1 0xffffffff86d4bb4f 328 212 380 7 5 [k] vma_interval_tree_remove [kernel.vmlinux] rbtree_augmented.h:338 0 1 5.13% 5.08% 0.00% 0.00% 0x10 1 1 0xffffffff86d4bb4b 416 255 357 197 32 [k] vma_interval_tree_remove [kernel.vmlinux] rbtree_augmented.h:338 0 1 1.10% 0.53% 0.00% 0.00% 0x28 1 1 0xffffffff86e06eb8 395 228 351 24 14 [k] do_dentry_open [kernel.vmlinux] open.c:966 0 1 1.10% 2.14% 57.07% 0.00% 0x38 1 1 0xffffffff878c9225 1364 792 462 7003 32 [k] down_write [kernel.vmlinux] atomic64_64.h:109 0 1 0.00% 0.00% 0.01% 0.00% 0x38 1 1 0xffffffff878c8e75 0 0 252 3 2 [k] rwsem_down_write_slowpath [kernel.vmlinux] atomic64_64.h:109 0 1 0.00% 0.13% 0.00% 0.00% 0x38 1 1 0xffffffff878c8e23 0 596 63 2 2 [k] rwsem_down_write_slowpath [kernel.vmlinux] atomic64_64.h:15 0 1 2.38% 2.94% 6.53% 0.00% 0x38 1 1 0xffffffff878c8ccb 1150 818 570 1197 32 [k] rwsem_down_write_slowpath [kernel.vmlinux] atomic64_64.h:109 0 1 30.59% 32.22% 0.00% 0.00% 0x38 1 1 0xffffffff878c8cb4 423 251 380 648 32 [k] rwsem_down_write_slowpath [kernel.vmlinux] atomic64_64.h:15 0 1 1.83% 1.74% 35.88% 0.00% 0x38 1 1 0xffffffff86b4f833 1217 1112 565 4586 32 [k] up_write [kernel.vmlinux] atomic64_64.h:91 0 1 with this change: ------------------------------------------------------------- 360 12 300 57 35 0xffff982cdae76400 ------------------------------------------------------------- 50.00% 59.67% 0.00% 0.00% 0x0 1 1 0xffffffff8215fb86 352 200 191 558 32 [k] __handle_mm_fault [kernel.vmlinux] memory.c:2940 0 1 8.33% 5.00% 0.00% 0.00% 0x4 1 1 0xffffffff8210ed44 370 284 263 42 24 [k] filemap_read [kernel.vmlinux] atomic.h:23 0 1 0.00% 0.00% 5.26% 2.86% 0x8 1 1 0xffffffff8214bce1 0 0 0 4 4 [k] vma_interval_tree_remove [kernel.vmlinux] rbtree_augmented.h:204 0 1 33.33% 14.33% 0.00% 0.00% 0x8 1 1 0xffffffff8214ba75 344 186 219 140 32 [k] vma_interval_tree_insert [kernel.vmlinux] interval_tree.c:23 0 1 0.00% 0.00% 94.74% 97.14% 0x10 1 1 0xffffffff8214bd24 0 0 0 88 29 [k] vma_interval_tree_remove [kernel.vmlinux] rbtree_augmented.h:339 0 1 8.33% 20.00% 0.00% 0.00% 0x10 1 1 0xffffffff8214bb3b 296 209 226 167 31 [k] vma_interval_tree_remove [kernel.vmlinux] rbtree_augmented.h:338 0 1 0.00% 0.67% 0.00% 0.00% 0x28 1 1 0xffffffff82206f45 0 140 334 4 3 [k] do_dentry_open [kernel.vmlinux] open.c:966 0 1 0.00% 0.33% 0.00% 0.00% 0x38 1 1 0xffffffff8250a6c4 0 286 126 5 5 [k] errseq_sample [kernel.vmlinux] errseq.c:125 0 Signed-off-by: JonasZhou <JonasZhou@zhaoxin.com> Link: https://lore.kernel.org/r/20240202083304.10995-1-JonasZhou-oc@zhaoxin.com Signed-off-by: Christian Brauner <brauner@kernel.org> diff d3b1a9a7 Fri Feb 02 01:33:04 MST 2024 JonasZhou <JonasZhou@zhaoxin.com> fs/address_space: move i_mmap_rwsem to mitigate a false sharing with i_mmap. In the struct address_space, there is a 32-byte gap between i_mmap and i_mmap_rwsem. Due to the alignment of struct address_space variables to 8 bytes, in certain situations, i_mmap and i_mmap_rwsem may end up in the same CACHE line. While running Unixbench/execl, we observe high false sharing issues when accessing i_mmap against i_mmap_rwsem. We move i_mmap_rwsem after i_private_list, ensuring a 64-byte gap between i_mmap and i_mmap_rwsem. For Intel Silver machines (2 sockets) using kernel v6.8 rc-2, the score of Unixbench/execl improves by ~3.94%, and the score of Unixbench/shell improves by ~3.26%. Baseline: ------------------------------------------------------------- 162 546 748 11374 21 0xffff92e266af90c0 ------------------------------------------------------------- 46.89% 44.65% 0.00% 0.00% 0x0 1 1 0xffffffff86d5fb96 460 258 271 1069 32 [k] __handle_mm_fault [kernel.vmlinux] memory.c:2940 0 1 4.21% 4.41% 0.00% 0.00% 0x4 1 1 0xffffffff86d0ed54 473 311 288 95 28 [k] filemap_read [kernel.vmlinux] atomic.h:23 0 1 0.00% 0.00% 0.04% 4.76% 0x8 1 1 0xffffffff86d4bcf1 0 0 0 5 4 [k] vma_interval_tree_remove [kernel.vmlinux] rbtree_augmented.h:204 0 1 6.41% 6.02% 0.00% 0.00% 0x8 1 1 0xffffffff86d4ba85 411 271 339 210 32 [k] vma_interval_tree_insert [kernel.vmlinux] interval_tree.c:23 0 1 0.00% 0.00% 0.47% 95.24% 0x10 1 1 0xffffffff86d4bd34 0 0 0 74 32 [k] vma_interval_tree_remove [kernel.vmlinux] rbtree_augmented.h:339 0 1 0.37% 0.13% 0.00% 0.00% 0x10 1 1 0xffffffff86d4bb4f 328 212 380 7 5 [k] vma_interval_tree_remove [kernel.vmlinux] rbtree_augmented.h:338 0 1 5.13% 5.08% 0.00% 0.00% 0x10 1 1 0xffffffff86d4bb4b 416 255 357 197 32 [k] vma_interval_tree_remove [kernel.vmlinux] rbtree_augmented.h:338 0 1 1.10% 0.53% 0.00% 0.00% 0x28 1 1 0xffffffff86e06eb8 395 228 351 24 14 [k] do_dentry_open [kernel.vmlinux] open.c:966 0 1 1.10% 2.14% 57.07% 0.00% 0x38 1 1 0xffffffff878c9225 1364 792 462 7003 32 [k] down_write [kernel.vmlinux] atomic64_64.h:109 0 1 0.00% 0.00% 0.01% 0.00% 0x38 1 1 0xffffffff878c8e75 0 0 252 3 2 [k] rwsem_down_write_slowpath [kernel.vmlinux] atomic64_64.h:109 0 1 0.00% 0.13% 0.00% 0.00% 0x38 1 1 0xffffffff878c8e23 0 596 63 2 2 [k] rwsem_down_write_slowpath [kernel.vmlinux] atomic64_64.h:15 0 1 2.38% 2.94% 6.53% 0.00% 0x38 1 1 0xffffffff878c8ccb 1150 818 570 1197 32 [k] rwsem_down_write_slowpath [kernel.vmlinux] atomic64_64.h:109 0 1 30.59% 32.22% 0.00% 0.00% 0x38 1 1 0xffffffff878c8cb4 423 251 380 648 32 [k] rwsem_down_write_slowpath [kernel.vmlinux] atomic64_64.h:15 0 1 1.83% 1.74% 35.88% 0.00% 0x38 1 1 0xffffffff86b4f833 1217 1112 565 4586 32 [k] up_write [kernel.vmlinux] atomic64_64.h:91 0 1 with this change: ------------------------------------------------------------- 360 12 300 57 35 0xffff982cdae76400 ------------------------------------------------------------- 50.00% 59.67% 0.00% 0.00% 0x0 1 1 0xffffffff8215fb86 352 200 191 558 32 [k] __handle_mm_fault [kernel.vmlinux] memory.c:2940 0 1 8.33% 5.00% 0.00% 0.00% 0x4 1 1 0xffffffff8210ed44 370 284 263 42 24 [k] filemap_read [kernel.vmlinux] atomic.h:23 0 1 0.00% 0.00% 5.26% 2.86% 0x8 1 1 0xffffffff8214bce1 0 0 0 4 4 [k] vma_interval_tree_remove [kernel.vmlinux] rbtree_augmented.h:204 0 1 33.33% 14.33% 0.00% 0.00% 0x8 1 1 0xffffffff8214ba75 344 186 219 140 32 [k] vma_interval_tree_insert [kernel.vmlinux] interval_tree.c:23 0 1 0.00% 0.00% 94.74% 97.14% 0x10 1 1 0xffffffff8214bd24 0 0 0 88 29 [k] vma_interval_tree_remove [kernel.vmlinux] rbtree_augmented.h:339 0 1 8.33% 20.00% 0.00% 0.00% 0x10 1 1 0xffffffff8214bb3b 296 209 226 167 31 [k] vma_interval_tree_remove [kernel.vmlinux] rbtree_augmented.h:338 0 1 0.00% 0.67% 0.00% 0.00% 0x28 1 1 0xffffffff82206f45 0 140 334 4 3 [k] do_dentry_open [kernel.vmlinux] open.c:966 0 1 0.00% 0.33% 0.00% 0.00% 0x38 1 1 0xffffffff8250a6c4 0 286 126 5 5 [k] errseq_sample [kernel.vmlinux] errseq.c:125 0 Signed-off-by: JonasZhou <JonasZhou@zhaoxin.com> Link: https://lore.kernel.org/r/20240202083304.10995-1-JonasZhou-oc@zhaoxin.com Signed-off-by: Christian Brauner <brauner@kernel.org> diff d3b1a9a7 Fri Feb 02 01:33:04 MST 2024 JonasZhou <JonasZhou@zhaoxin.com> fs/address_space: move i_mmap_rwsem to mitigate a false sharing with i_mmap. In the struct address_space, there is a 32-byte gap between i_mmap and i_mmap_rwsem. Due to the alignment of struct address_space variables to 8 bytes, in certain situations, i_mmap and i_mmap_rwsem may end up in the same CACHE line. While running Unixbench/execl, we observe high false sharing issues when accessing i_mmap against i_mmap_rwsem. We move i_mmap_rwsem after i_private_list, ensuring a 64-byte gap between i_mmap and i_mmap_rwsem. For Intel Silver machines (2 sockets) using kernel v6.8 rc-2, the score of Unixbench/execl improves by ~3.94%, and the score of Unixbench/shell improves by ~3.26%. Baseline: ------------------------------------------------------------- 162 546 748 11374 21 0xffff92e266af90c0 ------------------------------------------------------------- 46.89% 44.65% 0.00% 0.00% 0x0 1 1 0xffffffff86d5fb96 460 258 271 1069 32 [k] __handle_mm_fault [kernel.vmlinux] memory.c:2940 0 1 4.21% 4.41% 0.00% 0.00% 0x4 1 1 0xffffffff86d0ed54 473 311 288 95 28 [k] filemap_read [kernel.vmlinux] atomic.h:23 0 1 0.00% 0.00% 0.04% 4.76% 0x8 1 1 0xffffffff86d4bcf1 0 0 0 5 4 [k] vma_interval_tree_remove [kernel.vmlinux] rbtree_augmented.h:204 0 1 6.41% 6.02% 0.00% 0.00% 0x8 1 1 0xffffffff86d4ba85 411 271 339 210 32 [k] vma_interval_tree_insert [kernel.vmlinux] interval_tree.c:23 0 1 0.00% 0.00% 0.47% 95.24% 0x10 1 1 0xffffffff86d4bd34 0 0 0 74 32 [k] vma_interval_tree_remove [kernel.vmlinux] rbtree_augmented.h:339 0 1 0.37% 0.13% 0.00% 0.00% 0x10 1 1 0xffffffff86d4bb4f 328 212 380 7 5 [k] vma_interval_tree_remove [kernel.vmlinux] rbtree_augmented.h:338 0 1 5.13% 5.08% 0.00% 0.00% 0x10 1 1 0xffffffff86d4bb4b 416 255 357 197 32 [k] vma_interval_tree_remove [kernel.vmlinux] rbtree_augmented.h:338 0 1 1.10% 0.53% 0.00% 0.00% 0x28 1 1 0xffffffff86e06eb8 395 228 351 24 14 [k] do_dentry_open [kernel.vmlinux] open.c:966 0 1 1.10% 2.14% 57.07% 0.00% 0x38 1 1 0xffffffff878c9225 1364 792 462 7003 32 [k] down_write [kernel.vmlinux] atomic64_64.h:109 0 1 0.00% 0.00% 0.01% 0.00% 0x38 1 1 0xffffffff878c8e75 0 0 252 3 2 [k] rwsem_down_write_slowpath [kernel.vmlinux] atomic64_64.h:109 0 1 0.00% 0.13% 0.00% 0.00% 0x38 1 1 0xffffffff878c8e23 0 596 63 2 2 [k] rwsem_down_write_slowpath [kernel.vmlinux] atomic64_64.h:15 0 1 2.38% 2.94% 6.53% 0.00% 0x38 1 1 0xffffffff878c8ccb 1150 818 570 1197 32 [k] rwsem_down_write_slowpath [kernel.vmlinux] atomic64_64.h:109 0 1 30.59% 32.22% 0.00% 0.00% 0x38 1 1 0xffffffff878c8cb4 423 251 380 648 32 [k] rwsem_down_write_slowpath [kernel.vmlinux] atomic64_64.h:15 0 1 1.83% 1.74% 35.88% 0.00% 0x38 1 1 0xffffffff86b4f833 1217 1112 565 4586 32 [k] up_write [kernel.vmlinux] atomic64_64.h:91 0 1 with this change: ------------------------------------------------------------- 360 12 300 57 35 0xffff982cdae76400 ------------------------------------------------------------- 50.00% 59.67% 0.00% 0.00% 0x0 1 1 0xffffffff8215fb86 352 200 191 558 32 [k] __handle_mm_fault [kernel.vmlinux] memory.c:2940 0 1 8.33% 5.00% 0.00% 0.00% 0x4 1 1 0xffffffff8210ed44 370 284 263 42 24 [k] filemap_read [kernel.vmlinux] atomic.h:23 0 1 0.00% 0.00% 5.26% 2.86% 0x8 1 1 0xffffffff8214bce1 0 0 0 4 4 [k] vma_interval_tree_remove [kernel.vmlinux] rbtree_augmented.h:204 0 1 33.33% 14.33% 0.00% 0.00% 0x8 1 1 0xffffffff8214ba75 344 186 219 140 32 [k] vma_interval_tree_insert [kernel.vmlinux] interval_tree.c:23 0 1 0.00% 0.00% 94.74% 97.14% 0x10 1 1 0xffffffff8214bd24 0 0 0 88 29 [k] vma_interval_tree_remove [kernel.vmlinux] rbtree_augmented.h:339 0 1 8.33% 20.00% 0.00% 0.00% 0x10 1 1 0xffffffff8214bb3b 296 209 226 167 31 [k] vma_interval_tree_remove [kernel.vmlinux] rbtree_augmented.h:338 0 1 0.00% 0.67% 0.00% 0.00% 0x28 1 1 0xffffffff82206f45 0 140 334 4 3 [k] do_dentry_open [kernel.vmlinux] open.c:966 0 1 0.00% 0.33% 0.00% 0.00% 0x38 1 1 0xffffffff8250a6c4 0 286 126 5 5 [k] errseq_sample [kernel.vmlinux] errseq.c:125 0 Signed-off-by: JonasZhou <JonasZhou@zhaoxin.com> Link: https://lore.kernel.org/r/20240202083304.10995-1-JonasZhou-oc@zhaoxin.com Signed-off-by: Christian Brauner <brauner@kernel.org> diff d8f899d1 Wed Jan 24 07:28:55 MST 2024 Baokun Li <libaokun1@huawei.com> fs: make the i_size_read/write helpers be smp_load_acquire/store_release() In [Link] Linus mentions that acquire/release makes it clear which _particular_ memory accesses are the ordered ones, and it's unlikely to make any performance difference, so it's much better to pair up the release->acquire ordering than have a "wmb->rmb" ordering. ========================================================= update pagecache folio_mark_uptodate(folio) smp_wmb() set_bit PG_uptodate === ↑↑↑ STLR ↑↑↑ === smp_store_release(&inode->i_size, i_size) folio_test_uptodate(folio) test_bit PG_uptodate smp_rmb() === ↓↓↓ LDAR ↓↓↓ === smp_load_acquire(&inode->i_size) copy_page_to_iter() ========================================================= Calling smp_store_release() in i_size_write() ensures that the data in the page and the PG_uptodate bit are updated before the isize is updated, and calling smp_load_acquire() in i_size_read ensures that it will not read a newer isize than the data in the page. Therefore, this avoids buffered read-write inconsistencies caused by Load-Load reordering. Link: https://lore.kernel.org/r/CAHk-=wifOnmeJq+sn+2s-P46zw0SFEbw9BSCGgp2c5fYPtRPGw@mail.gmail.com/ Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Baokun Li <libaokun1@huawei.com> Link: https://lore.kernel.org/r/20240124142857.4146716-2-libaokun1@huawei.com Signed-off-by: Christian Brauner <brauner@kernel.org> diff d8f899d1 Wed Jan 24 07:28:55 MST 2024 Baokun Li <libaokun1@huawei.com> fs: make the i_size_read/write helpers be smp_load_acquire/store_release() In [Link] Linus mentions that acquire/release makes it clear which _particular_ memory accesses are the ordered ones, and it's unlikely to make any performance difference, so it's much better to pair up the release->acquire ordering than have a "wmb->rmb" ordering. ========================================================= update pagecache folio_mark_uptodate(folio) smp_wmb() set_bit PG_uptodate === ↑↑↑ STLR ↑↑↑ === smp_store_release(&inode->i_size, i_size) folio_test_uptodate(folio) test_bit PG_uptodate smp_rmb() === ↓↓↓ LDAR ↓↓↓ === smp_load_acquire(&inode->i_size) copy_page_to_iter() ========================================================= Calling smp_store_release() in i_size_write() ensures that the data in the page and the PG_uptodate bit are updated before the isize is updated, and calling smp_load_acquire() in i_size_read ensures that it will not read a newer isize than the data in the page. Therefore, this avoids buffered read-write inconsistencies caused by Load-Load reordering. Link: https://lore.kernel.org/r/CAHk-=wifOnmeJq+sn+2s-P46zw0SFEbw9BSCGgp2c5fYPtRPGw@mail.gmail.com/ Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Baokun Li <libaokun1@huawei.com> Link: https://lore.kernel.org/r/20240124142857.4146716-2-libaokun1@huawei.com Signed-off-by: Christian Brauner <brauner@kernel.org> |
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