NFSv4.1: Fix a potential layoutget/layoutrecall deadlock

If the client is sending a layoutget, but the server issues a callback
to recall what it thinks may be an outstanding layout, then we may find
an uninitialised layout attached to the inode due to the layoutget.
In that case, it is appropriate to return NFS4ERR_NOMATCHING_LAYOUT
rather than NFS4ERR_DELAY, as the latter can end up deadlocking.
Signed-off-by: NTrond Myklebust <trond.myklebust@hammerspace.com>

fs/nfs/callback_proc.c

@@ -215,9 +215,9 @@ static u32 pnfs_check_callback_stateid(struct pnfs_layout_hdr *lo,
 {
 	u32 oldseq, newseq;
 
-	/* Is the stateid still not initialised? */
+	/* Is the stateid not initialised? */
 	if (!pnfs_layout_is_valid(lo))
-		return NFS4ERR_DELAY;
+		return NFS4ERR_NOMATCHING_LAYOUT;
 
 	/* Mismatched stateid? */
 	if (!nfs4_stateid_match_other(&lo->plh_stateid, new))