[PATCH] autofs4: need to invalidate children on tree mount expire

I've found a case where invalid dentrys in a mount tree, waiting to be
cleaned up by d_invalidate, prevent the expected expire.

In this case dentrys created during a lookup for which a mount fails or has
no entry in the mount map contribute to the d_count of the parent dentry.
These dentrys may not be invalidated prior to comparing the interanl usage
count of valid autofs dentrys against the dentry d_count which makes a
mount tree appear busy so it doesn't expire.

Signed-off-by: Ian Kent <raven@themaw.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

fs/autofs4/expire.c

@@ -174,6 +174,12 @@ static int autofs4_tree_busy(struct vfsmount *mnt,
 			struct autofs_info *ino = autofs4_dentry_ino(p);
 			unsigned int ino_count = atomic_read(&ino->count);
 
+			/*
+			 * Clean stale dentries below that have not been
+			 * invalidated after a mount fail during lookup
+			 */
+			d_invalidate(p);
+
 			/* allow for dget above and top is already dgot */
 			if (p == top)
 				ino_count += 2;