NLM: Ensure that we resend all pending blocking locks after a reclaim

commit 666b3d80 upstream.

Currently, nlmclnt_lock will break out of the for(;;) loop when
the reclaimer wakes up the blocking lock thread by setting
nlm_lck_denied_grace_period. This causes the lock request to fail
with an ENOLCK error.
The intention was always to ensure that we resend the lock request
after the grace period has expired.
Reported-by: Wangyuan Zhang <Wangyuan.Zhang@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

fs/lockd/clntproc.c

@@ -551,6 +551,9 @@ nlmclnt_lock(struct nlm_rqst *req, struct file_lock *fl)
 		status = nlmclnt_block(block, req, NLMCLNT_POLL_TIMEOUT);
 		if (status < 0)
 			break;
+		/* Resend the blocking lock request after a server reboot */
+		if (resp->status ==  nlm_lck_denied_grace_period)
+			continue;
 		if (resp->status != nlm_lck_blocked)
 			break;
 	}