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alistair23-linux/fs/notify
Jan Kara 35e481761c fsnotify: avoid spurious EMFILE errors from inotify_init()
Inotify instance is destroyed when all references to it are dropped.
That not only means that the corresponding file descriptor needs to be
closed but also that all corresponding instance marks are freed (as each
mark holds a reference to the inotify instance).  However marks are
freed only after SRCU period ends which can take some time and thus if
user rapidly creates and frees inotify instances, number of existing
inotify instances can exceed max_user_instances limit although from user
point of view there is always at most one existing instance.  Thus
inotify_init() returns EMFILE error which is hard to justify from user
point of view.  This problem is exposed by LTP inotify06 testcase on
some machines.

We fix the problem by making sure all group marks are properly freed
while destroying inotify instance.  We wait for SRCU period to end in
that path anyway since we have to make sure there is no event being
added to the instance while we are tearing down the instance.  So it
takes only some plumbing to allow for marks to be destroyed in that path
as well and not from a dedicated work item.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Jan Kara <jack@suse.cz>
Reported-by: Xiaoguang Wang <wangxg.fnst@cn.fujitsu.com>
Tested-by: Xiaoguang Wang <wangxg.fnst@cn.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-05-19 19:12:14 -07:00
..
dnotify fsnotify: get rid of fsnotify_destroy_mark_locked() 2015-09-04 16:54:41 -07:00
fanotify fsnotify: get rid of fsnotify_destroy_mark_locked() 2015-09-04 16:54:41 -07:00
inotify inotify: actually check for invalid bits in sys_inotify_add_watch() 2015-11-05 19:34:48 -08:00
Kconfig rcu: Make SRCU optional by using CONFIG_SRCU 2015-01-06 11:04:29 -08:00
Makefile fs, notify: add procfs fdinfo helper 2012-12-17 17:15:28 -08:00
fdinfo.c inotify: hide internal kernel bits from fdinfo 2015-11-05 19:34:48 -08:00
fdinfo.h fs: Convert show_fdinfo functions to void 2014-11-05 14:13:23 -05:00
fsnotify.c fsnotify: remove mark->free_list 2015-09-04 16:54:41 -07:00
fsnotify.h fsnotify: avoid spurious EMFILE errors from inotify_init() 2016-05-19 19:12:14 -07:00
group.c fsnotify: avoid spurious EMFILE errors from inotify_init() 2016-05-19 19:12:14 -07:00
inode_mark.c fs/notify/inode_mark.c: use list_next_entry in fsnotify_unmount_inodes 2016-01-14 16:00:49 -08:00
mark.c fsnotify: avoid spurious EMFILE errors from inotify_init() 2016-05-19 19:12:14 -07:00
notification.c fanotify: fix double free of pending permission events 2014-08-06 18:01:12 -07:00
vfsmount_mark.c fsnotify: remove mark->free_list 2015-09-04 16:54:41 -07:00