linux/fs/kernfs
Tejun Heo df6a58c5c5 kernfs: don't depend on d_find_any_alias() when generating notifications
kernfs_notify_workfn() sends out file modified events for the
scheduled kernfs_nodes.  Because the modifications aren't from
userland, it doesn't have the matching file struct at hand and can't
use fsnotify_modify().  Instead, it looked up the inode and then used
d_find_any_alias() to find the dentry and used fsnotify_parent() and
fsnotify() directly to generate notifications.

The assumption was that the relevant dentries would have been pinned
if there are listeners, which isn't true as inotify doesn't pin
dentries at all and watching the parent doesn't pin the child dentries
even for dnotify.  This led to, for example, inotify watchers not
getting notifications if the system is under memory pressure and the
matching dentries got reclaimed.  It can also be triggered through
/proc/sys/vm/drop_caches or a remount attempt which involves shrinking
dcache.

fsnotify_parent() only uses the dentry to access the parent inode,
which kernfs can do easily.  Update kernfs_notify_workfn() so that it
uses fsnotify() directly for both the parent and target inodes without
going through d_find_any_alias().  While at it, supply the target file
name to fsnotify() from kernfs_node->name.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Evgeny Vereshchagin <evvers@ya.ru>
Fixes: d911d98748 ("kernfs: make kernfs_notify() trigger inotify events too")
Cc: John McCutchan <john@johnmccutchan.com>
Cc: Robert Love <rlove@rlove.org>
Cc: Eric Paris <eparis@parisplace.org>
Cc: stable@vger.kernel.org # v3.16+
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2016-08-31 14:48:52 +02:00
..
Kconfig kernfs: add CONFIG_KERNFS 2014-02-07 16:08:57 -08:00
Makefile sysfs, kernfs: add skeletons for kernfs 2013-11-27 13:28:24 -08:00
dir.c vfs: make the string hashes salt the hash 2016-06-10 20:21:46 -07:00
file.c kernfs: don't depend on d_find_any_alias() when generating notifications 2016-08-31 14:48:52 +02:00
inode.c switch ->setxattr() to passing dentry and inode separately 2016-05-27 20:09:16 -04:00
kernfs-internal.h switch ->setxattr() to passing dentry and inode separately 2016-05-27 20:09:16 -04:00
mount.c vfs: Generalize filesystem nodev handling. 2016-06-23 15:41:57 -05:00
symlink.c switch ->get_link() to delayed_call, kill ->put_link() 2015-12-30 13:01:03 -05:00