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Ian Kent 7cbdb4a286 autofs: use dentry flags to block walks during expire 
Somewhere along the way the autofs expire operation has changed to hold
a spin lock over expired dentry selection.  The autofs indirect mount
expired dentry selection is complicated and quite lengthy so it isn't
appropriate to hold a spin lock over the operation.

Commit 47be61845c ("fs/dcache.c: avoid soft-lockup in dput()") added a
might_sleep() to dput() causing a WARN_ONCE() about this usage to be
issued.

But the spin lock doesn't need to be held over this check, the autofs
dentry info.  flags are enough to block walks into dentrys during the
expire.

I've left the direct mount expire as it is (for now) because it is much
simpler and quicker than the indirect mount expire and adding spin lock
release and re-aquires would do nothing more than add overhead.

Fixes: 47be61845c ("fs/dcache.c: avoid soft-lockup in dput()")
Link: http://lkml.kernel.org/r/20160912014017.1773.73060.stgit@pluto.themaw.net
Signed-off-by: Ian Kent <raven@themaw.net>
Reported-by: Takashi Iwai <tiwai@suse.de>
Tested-by: Takashi Iwai <tiwai@suse.de>
Cc: Takashi Iwai <tiwai@suse.de>
Cc: NeilBrown <neilb@suse.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 		2016-09-19 15:36:17 -07:00
..
Kconfig fs/Kconfig: move autofs, autofs4 out 2009-01-22 13:15:54 +03:00
Makefile autofs4: add miscellaneous device for ioctls 2008-10-16 11:21:39 -07:00
autofs_i.h autofs races 2016-06-12 11:24:46 -04:00
dev-ioctl.c autofs4: use pr_xxx() macros directly for logging 2016-03-15 16:55:16 -07:00
expire.c autofs: use dentry flags to block walks during expire 2016-09-19 15:36:17 -07:00
init.c autofs4: coding style fixes 2016-03-15 16:55:16 -07:00
inode.c autofs4: use pr_xxx() macros directly for logging 2016-03-15 16:55:16 -07:00
root.c qstr: constify instances in autofs4 2016-07-20 23:30:06 -04:00
symlink.c autofs4: coding style fixes 2016-03-15 16:55:16 -07:00
waitq.c Merge branch 'work.const-qstr' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-08-06 09:49:02 -04:00