[Deepin-Kernel-SIG] [linux 6.6.y] [Upstream] Sync fs enhanced update from mainline-v6.8#1958
Merged
opsiff merged 11 commits intoJul 7, 2026
Merged
Conversation
mainline inclusion from mainline-v6.7-rc1 category: performance In recent discussions around some performance improvements in the file handling area we discussed switching the file cache to rely on SLAB_TYPESAFE_BY_RCU which allows us to get rid of call_rcu() based freeing for files completely. This is a pretty sensitive change overall but it might actually be worth doing. The main downside is the subtlety. The other one is that we should really wait for Jann's patch to land that enables KASAN to handle SLAB_TYPESAFE_BY_RCU UAFs. Currently it doesn't but a patch for this exists. With SLAB_TYPESAFE_BY_RCU objects may be freed and reused multiple times which requires a few changes. So it isn't sufficient anymore to just acquire a reference to the file in question under rcu using atomic_long_inc_not_zero() since the file might have already been recycled and someone else might have bumped the reference. In other words, callers might see reference count bumps from newer users. For this reason it is necessary to verify that the pointer is the same before and after the reference count increment. This pattern can be seen in get_file_rcu() and __files_get_rcu(). In addition, it isn't possible to access or check fields in struct file without first aqcuiring a reference on it. Not doing that was always very dodgy and it was only usable for non-pointer data in struct file. With SLAB_TYPESAFE_BY_RCU it is necessary that callers first acquire a reference under rcu or they must hold the files_lock of the fdtable. Failing to do either one of this is a bug. Thanks to Jann for pointing out that we need to ensure memory ordering between reallocations and pointer check by ensuring that all subsequent loads have a dependency on the second load in get_file_rcu() and providing a fixup that was folded into this patch. Cc: Jann Horn <jannh@google.com> Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Christian Brauner <brauner@kernel.org> (cherry picked from commit 0ede61d) Signed-off-by: Wentao Guan <guanwentao@uniontech.com>
![sourcery-ai[bot]](https://avatars.githubusercontent.com/in/48477?s=60&v=4){kind=small}
|
[APPROVALNOTIFIER] This PR is NOT APPROVED This pull-request has been approved by: The full list of commands accepted by this bot can be found here. DetailsNeeds approval from an approver in each of these files:Approvers can indicate their approval by writing |
mainline inclusion from mainline-v6.7-rc1 category: performance Backing files as used by overlayfs are never installed into file descriptor tables and are explicitly documented as such. They aren't subject to rcu access conditions like regular files are. Their lifetime is bound to the lifetime of the overlayfs file, i.e., they're stashed in ovl_file->private_data and go away otherwise. If they're set as vma->vm_file - which is their main purpose - then they're subject to regular refcount rules and vma->vm_file can't be installed into an fdtable after having been set. All in all I don't see any need for rcu delay here. So free it directly. This all hinges on such hybrid beasts to never actually be installed into fdtables which - as mentioned before - is not allowed. So add an explicit WARN_ON_ONCE() so we catch any case where someone is suddenly trying to install one of those things into a file descriptor table so we can have a nice long chat with them. Link: https://lore.kernel.org/r/20231005-sakralbau-wappnen-f5c31755ed70@brauner Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Christian Brauner <brauner@kernel.org> (cherry picked from commit 6cf41fc) Signed-off-by: Wentao Guan <guanwentao@uniontech.com>
mainline inclusion from mainline-v6.8-rc1 category: performance A file that has never gotten FMODE_OPENED will never have RCU-accessed references, its final fput() is equivalent to file_free() and if it doesn't have FMODE_BACKING either, it can be done from any context and won't need task_work treatment. Now that we have SLAB_TYPESAFE_BY_RCU we can simplify this and have other callers benefit. All of that can be achieved easier is to make fput() recoginze that case and call file_free() directly. No need to introduce a special primitive for that. It also allowed things like failing dentry_open() could benefit from that as well. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> [Christian Brauner <brauner@kernel.org>: massage commit message] Link: https://lore.kernel.org/r/20231126020834.GC38156@ZenIV Signed-off-by: Christian Brauner <brauner@kernel.org> (cherry picked from commit 7cb537b) Signed-off-by: Wentao Guan <guanwentao@uniontech.com>
mainline inclusion from mainline-v6.8-rc1 category: performance Commit 0ede61d ("file: convert to SLAB_TYPESAFE_BY_RCU") caused a performance regression as reported by the kernel test robot. The __fget_light() function is one of those critical ones for some loads, and the code generation was unnecessarily impacted. Let's just write that function to better. Reported-by: kernel test robot <oliver.sang@intel.com> Cc: Christian Brauner <brauner@kernel.org> Cc: Jann Horn <jannh@google.com> Cc: Mateusz Guzik <mjguzik@gmail.com> Closes: https://lore.kernel.org/oe-lkp/202311201406.2022ca3f-oliver.sang@intel.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Link: https://lore.kernel.org/r/CAHk-=wiCJtLbFWNURB34b9a_R_unaH3CiMRXfkR0-iihB_z68A@mail.gmail.com Signed-off-by: Christian Brauner <brauner@kernel.org> (cherry picked from commit 253ca86) Signed-off-by: Wentao Guan <guanwentao@uniontech.com>
opsiff
force-pushed
the
linux-6.6.y-2026-07-07-fs-2
branch
from
68a65ba to
1a660ce
Compare
mainline inclusion from mainline-v6.8-rc1 category: performance That really shouldn't have "get" in there as that implies we're bumping the reference count which we don't do at all. We used to but not anmore. Now we're just closing the fd and pick that file from the fdtable without bumping the reference count. Update the wrong documentation while at it. Link: https://lore.kernel.org/r/20231130-vfs-files-fixes-v1-1-e73ca6f4ea83@kernel.org Reviewed-by: Jan Kara <jack@suse.cz> Reviewed-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Christian Brauner <brauner@kernel.org> Conflicts: include/linux/fdtable.h [also change EXPORT_SYMBOL] (cherry picked from commit a88c955) Signed-off-by: Wentao Guan <guanwentao@uniontech.com>
deepin inclusion category: other To Keep KAPI, add a shim for file_close_fd. Fixes: 363e3f1 ("file: s/close_fd_get_file()/file_close_fd()/g") Signed-off-by: Wentao Guan <guanwentao@uniontech.com>
mainline inclusion from mainline-v6.8-rc1 category: performance 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> (cherry picked from commit 24fa3ae) Signed-off-by: Wentao Guan <guanwentao@uniontech.com>
mainline inclusion from mainline-v6.8-rc1 category: performance The naming is actively misleading since we switched to SLAB_TYPESAFE_BY_RCU. rcu_head is #define callback_head. Use callback_head directly and rename f_rcuhead to f_task_work. Add comments in there to explain what it's used for. Link: https://lore.kernel.org/r/20231130-vfs-files-fixes-v1-3-e73ca6f4ea83@kernel.org Reviewed-by: Jan Kara <jack@suse.cz> Reviewed-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Christian Brauner <brauner@kernel.org> (cherry picked from commit 372a34e) Signed-off-by: Wentao Guan <guanwentao@uniontech.com>
mainline inclusion from mainline-v6.8-rc1 category: performance Not every subsystem needs to have their own specialized helper. Just us the __receive_fd() helper. Link: https://lore.kernel.org/r/20231130-vfs-files-fixes-v1-4-e73ca6f4ea83@kernel.org Reviewed-by: Jan Kara <jack@suse.cz> Reviewed-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Christian Brauner <brauner@kernel.org> (cherry picked from commit eac9189) Signed-off-by: Wentao Guan <guanwentao@uniontech.com>
mainline inclusion from mainline-v6.8-rc1 category: performance Honestly, there's little value in having a helper with and without that int __user *ufd argument. It's just messy and doesn't really give us anything. Just expose receive_fd() with that argument and get rid of that helper. Link: https://lore.kernel.org/r/20231130-vfs-files-fixes-v1-5-e73ca6f4ea83@kernel.org Reviewed-by: Jan Kara <jack@suse.cz> Reviewed-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Christian Brauner <brauner@kernel.org> (cherry picked from commit 4e94ddf) Signed-off-by: Wentao Guan <guanwentao@uniontech.com>
mainline inclusion from mainline-v6.11-rc1 category: performance After commit 0ede61d ("file: convert to SLAB_TYPESAFE_BY_RCU") this loop always iterates exactly one time. Delete the for statement and pull the code in a tab. Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Reviewed-by: Christian Brauner <brauner@kernel.org> Acked-by: Jiri Olsa <jolsa@kernel.org> Acked-by: Yonghong Song <yonghong.song@linux.dev> Link: https://lore.kernel.org/bpf/ZoWJF51D4zWb6f5t@stanley.mountain (cherry picked from commit bc239eb) Signed-off-by: Wentao Guan <guanwentao@uniontech.com>
opsiff
force-pushed
the
linux-6.6.y-2026-07-07-fs-2
branch
from
1a660ce to
7c7725b
Compare
Member
Author
|
commit file: convert to SLAB_TYPESAFE_BY_RCU change KAPI, and have no idea to add compat for it, remove the pr from top now! |
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
4 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
No description provided.