NFS: Ensure that we update the sequence id under the slot table lock

Fix a callback slot table regression.

Fixes: e937ee71 ("nfs: Only update callback sequnce id when CB_SEQUENCE success")
Cc: Kinglong Mee <kinglongmee@gmail.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

fs/nfs/callback_proc.c

@@ -435,14 +435,13 @@ __be32 nfs4_callback_sequence(struct cb_sequenceargs *args,
 	spin_lock(&tbl->slot_tbl_lock);
 	/* state manager is resetting the session */
 	if (test_bit(NFS4_SLOT_TBL_DRAINING, &tbl->slot_tbl_state)) {
-		spin_unlock(&tbl->slot_tbl_lock);
 		status = htonl(NFS4ERR_DELAY);
 		/* Return NFS4ERR_BADSESSION if we're draining the session
 		 * in order to reset it.
 		 */
 		if (test_bit(NFS4CLNT_SESSION_RESET, &clp->cl_state))
 			status = htonl(NFS4ERR_BADSESSION);
-		goto out;
+		goto out_unlock;
 	}
 
 	memcpy(&res->csr_sessionid, &args->csa_sessionid,
@@ -453,9 +452,8 @@ __be32 nfs4_callback_sequence(struct cb_sequenceargs *args,
 	res->csr_target_highestslotid = NFS41_BC_MAX_CALLBACKS - 1;
 
 	status = validate_seqid(tbl, args);
-	spin_unlock(&tbl->slot_tbl_lock);
 	if (status)
-		goto out;
+		goto out_unlock;
 
 	cps->slotid = args->csa_slotid;
 
@@ -466,7 +464,7 @@ __be32 nfs4_callback_sequence(struct cb_sequenceargs *args,
 	 */
 	if (referring_call_exists(clp, args->csa_nrclists, args->csa_rclists)) {
 		status = htonl(NFS4ERR_DELAY);
-		goto out;
+		goto out_unlock;
 	}
 
 	/*
@@ -475,6 +473,8 @@ __be32 nfs4_callback_sequence(struct cb_sequenceargs *args,
 	 * (sequence ID, cached reply) MUST NOT change.
 	 */
 	slot->seq_nr++;
+out_unlock:
+	spin_unlock(&tbl->slot_tbl_lock);
 
 out:
 	cps->clp = clp; /* put in nfs4_callback_compound */