linux-kernel - [PATCH v2 01/20] mm, hugetlb: protect reserved pages when soft offlining a hugepage

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Message-Id: <1376040398-11212-2-git-send-email-iamjoonsoo.kim@lge.com>
Date:	Fri,  9 Aug 2013 18:26:19 +0900
From:	Joonsoo Kim <iamjoonsoo.kim@....com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Rik van Riel <riel@...hat.com>, Mel Gorman <mgorman@...e.de>,
	Michal Hocko <mhocko@...e.cz>,
	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Hugh Dickins <hughd@...gle.com>,
	Davidlohr Bueso <davidlohr.bueso@...com>,
	David Gibson <david@...son.dropbear.id.au>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, Joonsoo Kim <js1304@...il.com>,
	Wanpeng Li <liwanp@...ux.vnet.ibm.com>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	Hillf Danton <dhillf@...il.com>,
	Joonsoo Kim <iamjoonsoo.kim@....com>
Subject: [PATCH v2 01/20] mm, hugetlb: protect reserved pages when soft offlining a hugepage

Don't use the reserve pool when soft offlining a hugepage.
Check we have free pages outside the reserve pool before we
dequeue the huge page. Otherwise, we can steal other's reserve page.

Reviewed-by: Aneesh Kumar <aneesh.kumar@...ux.vnet.ibm.com>
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@....com>

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 6782b41..d971233 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -935,10 +935,11 @@ static struct page *alloc_buddy_huge_page(struct hstate *h, int nid)
  */
 struct page *alloc_huge_page_node(struct hstate *h, int nid)
 {
-	struct page *page;
+	struct page *page = NULL;
 
 	spin_lock(&hugetlb_lock);
-	page = dequeue_huge_page_node(h, nid);
+	if (h->free_huge_pages - h->resv_huge_pages > 0)
+		page = dequeue_huge_page_node(h, nid);
 	spin_unlock(&hugetlb_lock);
 
 	if (!page)
-- 
1.7.9.5

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