page allocator: check only once if the zonelist is suitable for the allocation

It is possible with __GFP_THISNODE that no zones are suitable.  This patch
makes sure the check is only made once.

Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Reviewed-by: Christoph Lameter <cl@linux-foundation.org>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Reviewed-by: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Dave Hansen <dave@linux.vnet.ibm.com>
Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index bfbd95c0610fb8e6bad08ebada8c5966155efb61..6be8fcb6f74f8cfbed43e825fa4d9e006a4837d1 100644 (file)
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1483,9 +1483,8 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order,
        if (should_fail_alloc_page(gfp_mask, order))
                return NULL;
 
-restart:
-       z = zonelist->_zonerefs;  /* the list of zones suitable for gfp_mask */
-
+       /* the list of zones suitable for gfp_mask */
+       z = zonelist->_zonerefs;
        if (unlikely(!z->zone)) {
                /*
                 * Happens if we have an empty zonelist as a result of
@@ -1494,6 +1493,7 @@ restart:
                return NULL;
        }
 
+restart:
        page = get_page_from_freelist(gfp_mask|__GFP_HARDWALL, nodemask, order,
                        zonelist, high_zoneidx, ALLOC_WMARK_LOW|ALLOC_CPUSET);
        if (page)