[PATCH] autofs4: avoid panic on bind mount of autofs owned directory

While this is not a solution to bind and move mounts on autofs owned
directories it is necessary to fix the trady error handling.

At least it avoids the kernel panic I observed checking out bug #4589.

Signed-off-by: Ian Kent <raven@themaw.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/fs/autofs4/expire.c b/fs/autofs4/expire.c
index 500425e..feb6ac4 100644
--- a/fs/autofs4/expire.c
+++ b/fs/autofs4/expire.c
@@ -56,12 +56,9 @@
 	mntget(mnt);
 	dget(dentry);
 
-	if (!follow_down(&mnt, &dentry))
+	if (!autofs4_follow_mount(&mnt, &dentry))
 		goto done;
 
-	while (d_mountpoint(dentry) && follow_down(&mnt, &dentry))
-		;
-
 	/* This is an autofs submount, we can't expire it */
 	if (is_autofs4_dentry(dentry))
 		goto done;