linux-kernel - [PATCH 02/25] Do not sanity check order in the fast path

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Message-Id: <1237543392-11797-3-git-send-email-mel@csn.ul.ie>
Date:	Fri, 20 Mar 2009 10:02:49 +0000
From:	Mel Gorman <mel@....ul.ie>
To:	Mel Gorman <mel@....ul.ie>,
	Linux Memory Management List <linux-mm@...ck.org>
Cc:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Nick Piggin <npiggin@...e.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Lin Ming <ming.m.lin@...el.com>,
	Zhang Yanmin <yanmin_zhang@...ux.intel.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH 02/25] Do not sanity check order in the fast path

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@....ul.ie>
Reviewed-by: Christoph Lameter <cl@...ux-foundation.org>
---
 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 dcf0ab8..8736047 100644
--- a/include/linux/gfp.h
+++ b/include/linux/gfp.h
@@ -181,9 +181,6 @@ __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();
@@ -197,9 +194,6 @@ 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 0671b3f..dd87dad 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1407,6 +1407,8 @@ 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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