kernel/linux.git/fs/proc/fd.c, branch v5.10.257

proc/fd: In fdinfo seq_show don't use get_files_struct

2024-06-21T12:52:49+00:00

[ Upstream commit 775e0656b27210ae668e33af00bece858f44576f ] When discussing[1] exec and posix file locks it was realized that none of the callers of get_files_struct fundamentally needed to call get_files_struct, and that by switching them to helper functions instead it will both simplify their code and remove unnecessary increments of files_struct.count. Those unnecessary increments can result in exec unnecessarily unsharing files_struct which breaking posix locks, and it can result in fget_light having to fallback to fget reducing system performance. Instead hold task_lock for the duration that task->files needs to be stable in seq_show. The task_lock was already taken in get_files_struct, and so skipping get_files_struct performs less work overall, and avoids the problems with the files_struct reference count. [1] https://lkml.kernel.org/r/20180915160423.GA31461@redhat.com Suggested-by: Oleg Nesterov Acked-by: Christian Brauner v1: https://lkml.kernel.org/r/20200817220425.9389-12-ebiederm@xmission.com Link: https://lkml.kernel.org/r/20201120231441.29911-17-ebiederm@xmission.com Signed-off-by: Eric W. Biederman Signed-off-by: Chuck Lever Signed-off-by: Sasha Levin

proc/fd: In proc_readfd_common use task_lookup_next_fd_rcu

2024-06-21T12:52:49+00:00

[ Upstream commit 5b17b61870e2f4b0a4fdc5c6039fbdb4ffb796df ] When discussing[1] exec and posix file locks it was realized that none of the callers of get_files_struct fundamentally needed to call get_files_struct, and that by switching them to helper functions instead it will both simplify their code and remove unnecessary increments of files_struct.count. Those unnecessary increments can result in exec unnecessarily unsharing files_struct which breaking posix locks, and it can result in fget_light having to fallback to fget reducing system performance. Using task_lookup_next_fd_rcu simplifies proc_readfd_common, by moving the checking for the maximum file descritor into the generic code, and by remvoing the need for capturing and releasing a reference on files_struct. As task_lookup_fd_rcu may update the fd ctx->pos has been changed to be the fd +2 after task_lookup_fd_rcu returns. [1] https://lkml.kernel.org/r/20180915160423.GA31461@redhat.com Suggested-by: Oleg Nesterov Tested-by: Andy Lavr v1: https://lkml.kernel.org/r/20200817220425.9389-10-ebiederm@xmission.com Link: https://lkml.kernel.org/r/20201120231441.29911-15-ebiederm@xmission.com Signed-off-by: Eric W. Biederman Signed-off-by: Chuck Lever Signed-off-by: Sasha Levin

proc/fd: In tid_fd_mode use task_lookup_fd_rcu

2024-06-21T12:52:48+00:00

[ Upstream commit 64eb661fda0269276b4c46965832938e3f268268 ] When discussing[1] exec and posix file locks it was realized that none of the callers of get_files_struct fundamentally needed to call get_files_struct, and that by switching them to helper functions instead it will both simplify their code and remove unnecessary increments of files_struct.count. Those unnecessary increments can result in exec unnecessarily unsharing files_struct which breaking posix locks, and it can result in fget_light having to fallback to fget reducing system performance. Instead of manually coding finding the files struct for a task and then calling files_lookup_fd_rcu, use the helper task_lookup_fd_rcu that combines those to steps. Making the code simpler and removing the need to get a reference on a files_struct. [1] https://lkml.kernel.org/r/20180915160423.GA31461@redhat.com Suggested-by: Oleg Nesterov Acked-by: Christian Brauner v1: https://lkml.kernel.org/r/20200817220425.9389-7-ebiederm@xmission.com Link: https://lkml.kernel.org/r/20201120231441.29911-12-ebiederm@xmission.com Signed-off-by: Eric W. Biederman Signed-off-by: Chuck Lever Signed-off-by: Sasha Levin

file: Replace fcheck_files with files_lookup_fd_rcu

2024-06-21T12:52:48+00:00

[ Upstream commit f36c2943274199cb8aef32ac96531ffb7c4b43d0 ] This change renames fcheck_files to files_lookup_fd_rcu. All of the remaining callers take the rcu_read_lock before calling this function so the _rcu suffix is appropriate. This change also tightens up the debug check to verify that all callers hold the rcu_read_lock. All callers that used to call files_check with the files->file_lock held have now been changed to call files_lookup_fd_locked. This change of name has helped remind me of which locks and which guarantees are in place helping me to catch bugs later in the patchset. The need for better names became apparent in the last round of discussion of this set of changes[1]. [1] https://lkml.kernel.org/r/CAHk-=wj8BQbgJFLa+J0e=iT-1qpmCRTbPAJ8gd6MJQ=kbRPqyQ@mail.gmail.com Link: https://lkml.kernel.org/r/20201120231441.29911-9-ebiederm@xmission.com Signed-off-by: Eric W. Biederman Signed-off-by: Chuck Lever Signed-off-by: Sasha Levin

file: Factor files_lookup_fd_locked out of fcheck_files

2024-06-21T12:52:48+00:00

[ Upstream commit 120ce2b0cd52abe73e8b16c23461eb14df5a87d8 ] To make it easy to tell where files->file_lock protection is being used when looking up a file create files_lookup_fd_locked. Only allow this function to be called with the file_lock held. Update the callers of fcheck and fcheck_files that are called with the files->file_lock held to call files_lookup_fd_locked instead. Hopefully this makes it easier to quickly understand what is going on. The need for better names became apparent in the last round of discussion of this set of changes[1]. [1] https://lkml.kernel.org/r/CAHk-=wj8BQbgJFLa+J0e=iT-1qpmCRTbPAJ8gd6MJQ=kbRPqyQ@mail.gmail.com Link: https://lkml.kernel.org/r/20201120231441.29911-8-ebiederm@xmission.com Signed-off-by: Eric W. Biederman Signed-off-by: Chuck Lever Signed-off-by: Sasha Levin

proc/fd: In proc_fd_link use fget_task

2024-06-21T12:52:47+00:00

[ Upstream commit 439be32656035d3239fd56f9b83353ec06cb3b45 ] When discussing[1] exec and posix file locks it was realized that none of the callers of get_files_struct fundamentally needed to call get_files_struct, and that by switching them to helper functions instead it will both simplify their code and remove unnecessary increments of files_struct.count. Those unnecessary increments can result in exec unnecessarily unsharing files_struct which breaking posix locks, and it can result in fget_light having to fallback to fget reducing system performance. Simplifying proc_fd_link is a little bit tricky. It is necessary to know that there is a reference to fd_f ile while path_get is running. This reference can either be guaranteed to exist either by locking the fdtable as the code currently does or by taking a reference on the file in question. Use fget_task to remove the need for get_files_struct and to take a reference to file in question. [1] https://lkml.kernel.org/r/20180915160423.GA31461@redhat.com Suggested-by: Oleg Nesterov v1: https://lkml.kernel.org/r/20200817220425.9389-8-ebiederm@xmission.com Link: https://lkml.kernel.org/r/20201120231441.29911-6-ebiederm@xmission.com Signed-off-by: Eric W. Biederman Signed-off-by: Chuck Lever Signed-off-by: Sasha Levin

proc: use "unsigned int" in proc_fill_cache()

2018-06-08T00:34:38+00:00

All those lengths are unsigned as they should be. Link: http://lkml.kernel.org/r/20180423213751.GC9043@avx2 Signed-off-by: Alexey Dobriyan Reviewed-by: Andrew Morton Cc: Al Viro Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

procfs: switch instantiate_t to d_splice_alias()

2018-05-26T18:20:50+00:00

... and get rid of pointless struct inode *dir argument of those, while we are at it. Signed-off-by: Al Viro

don't bother with tid_fd_revalidate() in lookups

2018-05-26T18:20:28+00:00

what we want it for is actually updating inode metadata; take _that_ into a separate helper and use it. Signed-off-by: Al Viro

proc_lookupfd_common(): don't bother with instantiate unless the file is open

2018-05-22T18:28:04+00:00

... and take the "check if file is open, pick ->f_mode" into a helper; tid_fd_revalidate() can use it. The next patch will get rid of tid_fd_revalidate() calls in instantiate callbacks. Signed-off-by: Al Viro