Documentation/filesystems/Locking no longer reflects current locking semantics. i_mutex is no longer used for locking, and has been superseded by i_rwsem. Additionally, ->iterate_shared() was not documented. Signed-off-by: Sean Anderson <seanga2@xxxxxxxxx> Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx> --- Documentation/filesystems/Locking | 43 +++++++++++++++++-------------- 1 file changed, 24 insertions(+), 19 deletions(-) diff --git a/Documentation/filesystems/Locking b/Documentation/filesystems/Locking index 75d2d57e2c44..15853d522941 100644 --- a/Documentation/filesystems/Locking +++ b/Documentation/filesystems/Locking @@ -69,31 +69,31 @@ prototypes: locking rules: all may block - i_mutex(inode) -lookup: yes -create: yes -link: yes (both) -mknod: yes -symlink: yes -mkdir: yes -unlink: yes (both) -rmdir: yes (both) (see below) -rename: yes (all) (see below) + i_rwsem(inode) +lookup: shared +create: exclusive +link: exclusive (both) +mknod: exclusive +symlink: exclusive +mkdir: exclusive +unlink: exclusive (both) +rmdir: exclusive (both)(see below) +rename: exclusive (all) (see below) readlink: no get_link: no -setattr: yes +setattr: exclusive permission: no (may not block if called in rcu-walk mode) get_acl: no getattr: no listxattr: no fiemap: no update_time: no -atomic_open: yes +atomic_open: exclusive tmpfile: no - Additionally, ->rmdir(), ->unlink() and ->rename() have ->i_mutex on -victim. + Additionally, ->rmdir(), ->unlink() and ->rename() have ->i_rwsem + exclusive on victim. cross-directory ->rename() has (per-superblock) ->s_vfs_rename_sem. See Documentation/filesystems/directory-locking for more detailed discussion @@ -111,10 +111,10 @@ prototypes: locking rules: all may block - i_mutex(inode) + i_rwsem(inode) list: no get: no -set: yes +set: exclusive --------------------------- super_operations --------------------------- prototypes: @@ -217,14 +217,14 @@ prototypes: locking rules: All except set_page_dirty and freepage may block - PageLocked(page) i_mutex + PageLocked(page) i_rwsem writepage: yes, unlocks (see below) readpage: yes, unlocks writepages: set_page_dirty no readpages: -write_begin: locks the page yes -write_end: yes, unlocks yes +write_begin: locks the page exclusive +write_end: yes, unlocks exclusive bmap: invalidatepage: yes releasepage: yes @@ -439,6 +439,7 @@ prototypes: ssize_t (*read_iter) (struct kiocb *, struct iov_iter *); ssize_t (*write_iter) (struct kiocb *, struct iov_iter *); int (*iterate) (struct file *, struct dir_context *); + int (*iterate_shared) (struct file *, struct dir_context *); unsigned int (*poll) (struct file *, struct poll_table_struct *); long (*unlocked_ioctl) (struct file *, unsigned int, unsigned long); long (*compat_ioctl) (struct file *, unsigned int, unsigned long); @@ -480,6 +481,10 @@ mutex or just to use i_size_read() instead. Note: this does not protect the file->f_pos against concurrent modifications since this is something the userspace has to take care about. +->iterate() is called with i_rwsem exclusive. + +->iterate_shared() is called with i_rwsem at least shared. + ->fasync() is responsible for maintaining the FASYNC bit in filp->f_flags. Most instances call fasync_helper(), which does that maintenance, so it's not normally something one needs to worry about. Return values > 0 will be -- 2.17.0
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