pNFS: The client must not do I/O to the DS if it's lease has expired

Ensure that the client conforms to the normative behaviour described in
RFC5661 Section 12.7.2: "If a client believes its lease has expired,
it MUST NOT send I/O to the storage device until it has validated its
lease."

So ensure that we wait for the lease to be validated before using
the layout.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Cc: stable@vger.kernel.org # v3.20+

fs/nfs/pnfs.c

@@ -1555,6 +1555,7 @@ pnfs_update_layout(struct inode *ino,
 	}
 
 lookup_again:
+	nfs4_client_recover_expired_lease(clp);
 	first = false;
 	spin_lock(&ino->i_lock);
 	lo = pnfs_find_alloc_layout(ino, ctx, gfp_flags);