hugetlb: abstract numa round robin selection

Need this as a separate function for a future patch.

No behaviour change.
Acked-by: Adam Litke <agl@us.ibm.com>
Acked-by: Nishanth Aravamudan <nacc@us.ibm.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/hugetlb.c

@@ -565,20 +565,7 @@ static struct page *alloc_fresh_huge_page_node(struct hstate *h, int nid)
 	return page;
 }
 
-static int alloc_fresh_huge_page(struct hstate *h)
-{
-	struct page *page;
-	int start_nid;
-	int next_nid;
-	int ret = 0;
-
-	start_nid = h->hugetlb_next_nid;
-
-	do {
-		page = alloc_fresh_huge_page_node(h, h->hugetlb_next_nid);
-		if (page)
-			ret = 1;
-		/*
+/*
  * Use a helper variable to find the next node and then
  * copy it back to hugetlb_next_nid afterwards:
  * otherwise there's a window in which a racer might
@@ -589,10 +576,30 @@ static int alloc_fresh_huge_page(struct hstate *h)
  * if we just successfully allocated a hugepage so that
  * the next caller gets hugepages on the next node.
  */
+static int hstate_next_node(struct hstate *h)
+{
+	int next_nid;
 	next_nid = next_node(h->hugetlb_next_nid, node_online_map);
 	if (next_nid == MAX_NUMNODES)
 		next_nid = first_node(node_online_map);
 	h->hugetlb_next_nid = next_nid;
+	return next_nid;
+}
+
+static int alloc_fresh_huge_page(struct hstate *h)
+{
+	struct page *page;
+	int start_nid;
+	int next_nid;
+	int ret = 0;
+
+	start_nid = h->hugetlb_next_nid;
+
+	do {
+		page = alloc_fresh_huge_page_node(h, h->hugetlb_next_nid);
+		if (page)
+			ret = 1;
+		next_nid = hstate_next_node(h);
 	} while (!page && h->hugetlb_next_nid != start_nid);
 
 	if (ret)