SUNRPC: refresh rq_pages using a bulk page allocator

Reduce the rate at which nfsd threads hammer on the page allocator.  This
improves throughput scalability by enabling the threads to run more
independently of each other.

[mgorman: Update interpretation of alloc_pages_bulk return value]

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Chuck Lever <[email protected]>
Signed-off-by: Mel Gorman <[email protected]>
Reviewed-by: Alexander Lobakin <[email protected]>
Cc: Alexander Duyck <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Cc: David Miller <[email protected]>
Cc: Ilias Apalodimas <[email protected]>
Cc: Jesper Dangaard Brouer <[email protected]>
Cc: Matthew Wilcox (Oracle) <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

net/sunrpc/svc_xprt.c

@@ -662,30 +662,29 @@ static int svc_alloc_arg(struct svc_rqst *rqstp)
 {
 	struct svc_serv *serv = rqstp->rq_server;
 	struct xdr_buf *arg = &rqstp->rq_arg;
-	int pages;
-	int i;
+	unsigned long pages, filled;
 
-	/* now allocate needed pages.  If we get a failure, sleep briefly */
 	pages = (serv->sv_max_mesg + 2 * PAGE_SIZE) >> PAGE_SHIFT;
 	if (pages > RPCSVC_MAXPAGES) {
-		pr_warn_once("svc: warning: pages=%u > RPCSVC_MAXPAGES=%lu\n",
+		pr_warn_once("svc: warning: pages=%lu > RPCSVC_MAXPAGES=%lu\n",
 			     pages, RPCSVC_MAXPAGES);
 		/* use as many pages as possible */
 		pages = RPCSVC_MAXPAGES;
 	}
-	for (i = 0; i < pages ; i++)
-		while (rqstp->rq_pages[i] == NULL) {
-			struct page *p = alloc_page(GFP_KERNEL);
-			if (!p) {
-				set_current_state(TASK_INTERRUPTIBLE);
-				if (signalled() || kthread_should_stop()) {
-					set_current_state(TASK_RUNNING);
-					return -EINTR;
-				}
-				schedule_timeout(msecs_to_jiffies(500));
-			}
-			rqstp->rq_pages[i] = p;
+
+	for (;;) {
+		filled = alloc_pages_bulk_array(GFP_KERNEL, pages,
+						rqstp->rq_pages);
+		if (filled == pages)
+			break;
+
+		set_current_state(TASK_INTERRUPTIBLE);
+		if (signalled() || kthread_should_stop()) {
+			set_current_state(TASK_RUNNING);
+			return -EINTR;
 		}
+		schedule_timeout(msecs_to_jiffies(500));
+	}
 	rqstp->rq_page_end = &rqstp->rq_pages[pages];
 	rqstp->rq_pages[pages] = NULL; /* this might be seen in nfsd_splice_actor() */