[PATCH 02/22] Do not sanity check order in the fast path

[Mel Gorman <mel@csn.ul.ie>]

No user of the allocator API should be passing in an order >= MAX_ORDER
but we check for it on each and every allocation. Delete this check and
make it a VM_BUG_ON check further down the call path.

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>
---
 include/linux/gfp.h |    6 ------
 mm/page_alloc.c     |    2 ++
 2 files changed, 2 insertions(+), 6 deletions(-)

diff --git a/include/linux/gfp.h b/include/linux/gfp.h
index 556c840..760f6c0 100644
--- a/include/linux/gfp.h
+++ b/include/linux/gfp.h
@@ -182,9 +182,6 @@ __alloc_pages(gfp_t gfp_mask, unsigned int order,
 static inline struct page *alloc_pages_node(int nid, gfp_t gfp_mask,
 						unsigned int order)
 {
-	if (unlikely(order >= MAX_ORDER))
-		return NULL;
-
 	/* Unknown node is current node */
 	if (nid < 0)
 		nid = numa_node_id();
@@ -198,9 +195,6 @@ extern struct page *alloc_pages_current(gfp_t gfp_mask, unsigned order);
 static inline struct page *
 alloc_pages(gfp_t gfp_mask, unsigned int order)
 {
-	if (unlikely(order >= MAX_ORDER))
-		return NULL;
-
 	return alloc_pages_current(gfp_mask, order);
 }
 extern struct page *alloc_page_vma(gfp_t gfp_mask,
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index dcc4f05..5028f40 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1405,6 +1405,8 @@ get_page_from_freelist(gfp_t gfp_mask, nodemask_t *nodemask, unsigned int order,
 
 	classzone_idx = zone_idx(preferred_zone);
 
+	VM_BUG_ON(order >= MAX_ORDER);
+
 zonelist_scan:
 	/*
 	 * Scan zonelist, looking for a zone with enough free.
-- 
1.5.6.5

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