staging: lustre: use explicit poll loop in ptlrpc_unregister_reply

replace l_wait_event() with wait_event_idle_timeout() and explicit
loop.  This approach is easier to understand.
Reviewed-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: NeilBrown <neilb@suse.com>
Reviewed-by: Patrick Farrell <paf@cray.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/lustre/lustre/ptlrpc/client.c

@@ -2500,7 +2500,6 @@ static int ptlrpc_unregister_reply(struct ptlrpc_request *request, int async)
 {
 	int rc;
 	wait_queue_head_t *wq;
-	struct l_wait_info lwi;
 
 	/* Might sleep. */
 	LASSERT(!in_interrupt());
@@ -2543,16 +2542,17 @@ static int ptlrpc_unregister_reply(struct ptlrpc_request *request, int async)
 		 * Network access will complete in finite time but the HUGE
 		 * timeout lets us CWARN for visibility of sluggish NALs
 		 */
-		lwi = LWI_TIMEOUT_INTERVAL(LONG_UNLINK * HZ,
-					   HZ, NULL, NULL);
-		rc = l_wait_event(*wq, !ptlrpc_client_recv_or_unlink(request),
-				  &lwi);
-		if (rc == 0) {
+		int cnt = 0;
+		while (cnt < LONG_UNLINK &&
+		       (rc = wait_event_idle_timeout(*wq,
+						     !ptlrpc_client_recv_or_unlink(request),
+						     HZ)) == 0)
+			cnt += 1;
+		if (rc > 0) {
 			ptlrpc_rqphase_move(request, request->rq_next_phase);
 			return 1;
 		}
 
-		LASSERT(rc == -ETIMEDOUT);
 		DEBUG_REQ(D_WARNING, request,
 			  "Unexpectedly long timeout receiving_reply=%d req_ulinked=%d reply_unlinked=%d",
 			  request->rq_receiving_reply,