Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932413AbaGDHxK (ORCPT ); Fri, 4 Jul 2014 03:53:10 -0400 Received: from lgeamrelo01.lge.com ([156.147.1.125]:43455 "EHLO lgeamrelo01.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932082AbaGDHxD (ORCPT ); Fri, 4 Jul 2014 03:53:03 -0400 X-Original-SENDERIP: 10.177.220.145 X-Original-MAILFROM: iamjoonsoo.kim@lge.com From: Joonsoo Kim To: Andrew Morton Cc: "Kirill A. Shutemov" , Rik van Riel , Peter Zijlstra , Mel Gorman , Johannes Weiner , Minchan Kim , Yasuaki Ishimatsu , Zhang Yanfei , "Srivatsa S. Bhat" , Tang Chen , Naoya Horiguchi , Bartlomiej Zolnierkiewicz , Wen Congyang , Marek Szyprowski , Michal Nazarewicz , Laura Abbott , Heesub Shin , "Aneesh Kumar K.V" , Ritesh Harjani , t.stanislaws@samsung.com, Gioh Kim , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Joonsoo Kim Subject: [PATCH 04/10] mm/page_alloc: carefully free the page on isolate pageblock Date: Fri, 4 Jul 2014 16:57:49 +0900 Message-Id: <1404460675-24456-5-git-send-email-iamjoonsoo.kim@lge.com> X-Mailer: git-send-email 1.7.9.5 In-Reply-To: <1404460675-24456-1-git-send-email-iamjoonsoo.kim@lge.com> References: <1404460675-24456-1-git-send-email-iamjoonsoo.kim@lge.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org We got migratetype without holding the lock so it could be racy. If some pages go on the isolate migratetype buddy list by this race, we can't allocate this page anymore until next isolation attempt on this pageblock. Below is possible scenario of this race. pageblock 1 is isolate migratetype. CPU1 CPU2 - get_pfnblock_migratetype(pageblock 1), so MIGRATE_ISOLATE is returned - call free_one_page() with MIGRATE_ISOLATE - grab the zone lock - unisolate pageblock 1 - release the zone lock - grab the zone lock - call __free_one_page() with MIGRATE_ISOLATE - free page go into isolate buddy list and we can't use it anymore To prevent this possibility, re-check migratetype with holding the lock. Signed-off-by: Joonsoo Kim --- mm/page_alloc.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 99c05f7..d8feedc 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -743,6 +743,17 @@ static void free_one_page(struct zone *zone, spin_lock(&zone->lock); zone->pages_scanned = 0; + if (unlikely(is_migrate_isolate(migratetype))) { + /* + * We got migratetype without holding the lock so it could be + * racy. If some pages go on the isolate migratetype buddy list + * by this race, we can't allocate this page anymore until next + * isolation attempt on this pageblock. To prevent this + * possibility, re-check migratetype with holding the lock. + */ + migratetype = get_pfnblock_migratetype(page, pfn); + } + __free_one_page(page, pfn, zone, order, migratetype); if (!is_migrate_isolate(migratetype)) __mod_zone_freepage_state(zone, 1 << order, migratetype); -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/