On Tue, 2017-08-01 at 07:09 -0400, Sean Anderson wrote: > 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 i_mutex is no longer used for locking, and has been superseded 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> > --- > v2: changed 'yes's to 'exclusive's when describing i_rwsem usage > > Documentation/filesystems/Locking | 43 ++++++++++++++++++++++----------------- > 1 file changed, 24 insertions(+), 19 deletions(-) > > diff --git a/Documentation/filesystems/Locking b/Documentation/filesystems/Locking > index fe25787ff6d4..c0cab97d2b1a 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 Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx>
