fuse: don't check_submounts_and_drop() in RCU walk

If revalidate finds an invalid dentry in RCU walk mode, let the VFS deal
with it instead of calling check_submounts_and_drop() which is not prepared
for being called from RCU walk.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: stable@vger.kernel.org

fs/fuse/dir.c

@@ -259,7 +259,8 @@ static int fuse_dentry_revalidate(struct dentry *entry, unsigned int flags)
 
 invalid:
 	ret = 0;
-	if (check_submounts_and_drop(entry) != 0)
+
+	if (!(flags & LOOKUP_RCU) && check_submounts_and_drop(entry) != 0)
 		ret = 1;
 	goto out;
 }