[PATCH 2/2] mm: page_alloc: avoid slowpath for more than MAX_ORDERallocation.

[Pintu Kumar]

It was observed that if order is passed as more than MAX_ORDER
allocation in __alloc_pages_nodemask, it will unnecessarily go to
slowpath and then return failure.
Since we know that more than MAX_ORDER will anyways fail, we can
avoid slowpath by returning failure in nodemask itself.

Signed-off-by: Pintu Kumar <pintu.k@xxxxxxxxxxx>
---
 mm/page_alloc.c |    4 ++++
 1 file changed, 4 insertions(+)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 202ab58..6d38e75 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1564,6 +1564,10 @@ __setup("fail_page_alloc=", setup_fail_page_alloc);
 
 static bool should_fail_alloc_page(gfp_t gfp_mask, unsigned int order)
 {
+	if (order >= MAX_ORDER) {
+		WARN_ON(!(gfp_mask & __GFP_NOWARN));
+		return false;
+	}
 	if (order < fail_page_alloc.min_order)
 		return false;
 	if (gfp_mask & __GFP_NOFAIL)
-- 
1.7.9.5

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