NFS: Add timeout to submounts

Make automounted partitions expire using the mark_mounts_for_expiry()
function. The timeout is controlled via a sysctl.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
index 47167ab..3eea556 100644
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -167,6 +167,7 @@
 	struct nfs_server *server;
 	struct rpc_clnt	*rpc;
 
+	shrink_submounts(vfsmnt, &nfs_automount_list);
 	if (!(flags & MNT_FORCE))
 		return;
 	/* -EIO all pending I/O */
@@ -1943,6 +1944,7 @@
 	nfs_free_iostats(server->io_stats);
 	kfree(server->hostname);
 	kfree(server);
+	nfs_release_automount_timer();
 }
 
 static struct file_system_type nfs_fs_type = {
@@ -2288,6 +2290,7 @@
 	nfs_free_iostats(server->io_stats);
 	kfree(server->hostname);
 	kfree(server);
+	nfs_release_automount_timer();
 }
 
 static struct file_system_type nfs4_fs_type = {