From a8bbf72ab9b3072ece630d97689145b1a2f01221 Mon Sep 17 00:00:00 2001
From: Mel Gorman <mel@csn.ul.ie>
Date: Tue, 31 Jul 2007 00:37:30 -0700
Subject: [PATCH] Do not trigger OOM-killer for high-order allocation failures

out_of_memory() may be called when an allocation is failing and the direct
reclaim is not making any progress.  This does not take into account the
requested order of the allocation.  If the request if for an order larger
than PAGE_ALLOC_COSTLY_ORDER, it is reasonable to fail the allocation
because the kernel makes no guarantees about those allocations succeeding.

This false OOM situation can occur if a user is trying to grow the hugepage
pool in a script like;

#!/bin/bash
REQUIRED=$1
echo 1 > /proc/sys/vm/hugepages_treat_as_movable
echo $REQUIRED > /proc/sys/vm/nr_hugepages
ACTUAL=`cat /proc/sys/vm/nr_hugepages`
while [ $REQUIRED -ne $ACTUAL ]; do
	echo Huge page pool at $ACTUAL growing to $REQUIRED
	echo $REQUIRED > /proc/sys/vm/nr_hugepages
	ACTUAL=`cat /proc/sys/vm/nr_hugepages`
	sleep 1
done

This is a reasonable scenario when ZONE_MOVABLE is in use but triggers OOM
easily on 2.6.23-rc1. This patch will fail an allocation for an order above
PAGE_ALLOC_COSTLY_ORDER instead of killing processes and retrying.

Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Acked-by: Andy Whitcroft <apw@shadowen.org>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
 mm/page_alloc.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 0bd4d82ddfffb..3da85b81dabb3 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1350,6 +1350,10 @@ __alloc_pages(gfp_t gfp_mask, unsigned int order,
 		if (page)
 			goto got_pg;
 
+		/* The OOM killer will not help higher order allocs so fail */
+		if (order > PAGE_ALLOC_COSTLY_ORDER)
+			goto nopage;
+
 		out_of_memory(zonelist, gfp_mask, order);
 		goto restart;
 	}
-- 
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