SUNRPC: Adjust rpciod workqueue parameters

Increase the concurrency level for rpciod threads to allow for allocations
etc that happen in the RPCSEC_GSS layer. Also note that the NFSv4 byte range
locks may now need to allocate memory from inside rpciod.

Add the WQ_HIGHPRI flag to improve latency guarantees while we're at it.
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

net/sunrpc/sched.c

@@ -1069,7 +1069,8 @@ static int rpciod_start(void)
 	 * Create the rpciod thread and wait for it to start.
 	 */
 	dprintk("RPC:       creating workqueue rpciod\n");
-	wq = alloc_workqueue("rpciod", WQ_MEM_RECLAIM, 1);
+	/* Note: highpri because network receive is latency sensitive */
+	wq = alloc_workqueue("rpciod", WQ_MEM_RECLAIM | WQ_HIGHPRI, 0);
 	rpciod_workqueue = wq;
 	return rpciod_workqueue != NULL;
 }