mm, hugetlb: move up the code which check availability of free huge page

In this time we are holding a hugetlb_lock, so hstate values can't be
changed.  If we don't have any usable free huge page in this time, we
don't need to proceed with the processing.  So move this code up.

Signed-off-by: Joonsoo Kim <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Reviewed-by: Wanpeng Li <[email protected]>
Reviewed-by: Aneesh Kumar K.V <[email protected]>
Cc: Aneesh Kumar K.V <[email protected]>
Acked-by: Hillf Danton <[email protected]>
Cc: Naoya Horiguchi <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: KAMEZAWA Hiroyuki <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Davidlohr Bueso <[email protected]>
Cc: David Gibson <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

mm/hugetlb.c

@@ -539,10 +539,6 @@ static struct page *dequeue_huge_page_vma(struct hstate *h,
 	struct zoneref *z;
 	unsigned int cpuset_mems_cookie;
 
-retry_cpuset:
-	cpuset_mems_cookie = get_mems_allowed();
-	zonelist = huge_zonelist(vma, address,
-					htlb_alloc_mask, &mpol, &nodemask);
 	/*
 	 * A child process with MAP_PRIVATE mappings created by their parent
 	 * have no page reserves. This check ensures that reservations are
@@ -556,6 +552,11 @@ static struct page *dequeue_huge_page_vma(struct hstate *h,
 	if (avoid_reserve && h->free_huge_pages - h->resv_huge_pages == 0)
 		goto err;
 
+retry_cpuset:
+	cpuset_mems_cookie = get_mems_allowed();
+	zonelist = huge_zonelist(vma, address,
+					htlb_alloc_mask, &mpol, &nodemask);
+
 	for_each_zone_zonelist_nodemask(zone, z, zonelist,
 						MAX_NR_ZONES - 1, nodemask) {
 		if (cpuset_zone_allowed_softwall(zone, htlb_alloc_mask)) {
@@ -574,7 +575,6 @@ static struct page *dequeue_huge_page_vma(struct hstate *h,
 	return page;
 
 err:
-	mpol_cond_put(mpol);
 	return NULL;
 }