From: Minchan Kim <minchan@kernel.org> To: Andrew Morton <akpm@linux-foundation.org> Cc: Mel Gorman <mgorman@techsingularity.net>, Vlastimil Babka <vbabka@suse.cz>, Joonsoo Kim <iamjoonsoo.kim@lge.com>, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Sangseok Lee <sangseok.lee@lge.com>, Minchan Kim <minchan@kernel.org> Subject: [PATCH 2/4] mm: prevent double decrease of nr_reserved_highatomic Date: Fri, 7 Oct 2016 14:45:34 +0900 [thread overview] Message-ID: <1475819136-24358-3-git-send-email-minchan@kernel.org> (raw) In-Reply-To: <1475819136-24358-1-git-send-email-minchan@kernel.org> There is race between page freeing and unreserved highatomic. CPU 0 CPU 1 free_hot_cold_page mt = get_pfnblock_migratetype set_pcppage_migratetype(page, mt) unreserve_highatomic_pageblock spin_lock_irqsave(&zone->lock) move_freepages_block set_pageblock_migratetype(page) spin_unlock_irqrestore(&zone->lock) free_pcppages_bulk __free_one_page(mt) <- mt is stale By above race, a page on CPU 0 could go non-highorderatomic free list since the pageblock's type is changed. By that, unreserve logic of highorderatomic can decrease reserved count on a same pageblock several times and then it will make mismatch between nr_reserved_highatomic and the number of reserved pageblock. So, this patch verifies whether the pageblock is highatomic or not and decrease the count only if the pageblock is highatomic. Signed-off-by: Minchan Kim <minchan@kernel.org> --- mm/page_alloc.c | 24 ++++++++++++++++++------ 1 file changed, 18 insertions(+), 6 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index e7cbb3cc22fa..d110cd640264 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -2133,13 +2133,25 @@ static void unreserve_highatomic_pageblock(const struct alloc_context *ac) continue; /* - * It should never happen but changes to locking could - * inadvertently allow a per-cpu drain to add pages - * to MIGRATE_HIGHATOMIC while unreserving so be safe - * and watch for underflows. + * In page freeing path, migratetype change is racy so + * we can counter several free pages in a pageblock + * in this loop althoug we changed the pageblock type + * from highatomic to ac->migratetype. So we should + * adjust the count once. */ - zone->nr_reserved_highatomic -= min(pageblock_nr_pages, - zone->nr_reserved_highatomic); + if (get_pageblock_migratetype(page) == + MIGRATE_HIGHATOMIC) { + /* + * It should never happen but changes to + * locking could inadvertently allow a per-cpu + * drain to add pages to MIGRATE_HIGHATOMIC + * while unreserving so be safe and watch for + * underflows. + */ + zone->nr_reserved_highatomic -= min( + pageblock_nr_pages, + zone->nr_reserved_highatomic); + } /* * Convert to ac->migratetype and avoid the normal -- 2.7.4
WARNING: multiple messages have this Message-ID (diff)
From: Minchan Kim <minchan@kernel.org> To: Andrew Morton <akpm@linux-foundation.org> Cc: Mel Gorman <mgorman@techsingularity.net>, Vlastimil Babka <vbabka@suse.cz>, Joonsoo Kim <iamjoonsoo.kim@lge.com>, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Sangseok Lee <sangseok.lee@lge.com>, Minchan Kim <minchan@kernel.org> Subject: [PATCH 2/4] mm: prevent double decrease of nr_reserved_highatomic Date: Fri, 7 Oct 2016 14:45:34 +0900 [thread overview] Message-ID: <1475819136-24358-3-git-send-email-minchan@kernel.org> (raw) In-Reply-To: <1475819136-24358-1-git-send-email-minchan@kernel.org> There is race between page freeing and unreserved highatomic. CPU 0 CPU 1 free_hot_cold_page mt = get_pfnblock_migratetype set_pcppage_migratetype(page, mt) unreserve_highatomic_pageblock spin_lock_irqsave(&zone->lock) move_freepages_block set_pageblock_migratetype(page) spin_unlock_irqrestore(&zone->lock) free_pcppages_bulk __free_one_page(mt) <- mt is stale By above race, a page on CPU 0 could go non-highorderatomic free list since the pageblock's type is changed. By that, unreserve logic of highorderatomic can decrease reserved count on a same pageblock several times and then it will make mismatch between nr_reserved_highatomic and the number of reserved pageblock. So, this patch verifies whether the pageblock is highatomic or not and decrease the count only if the pageblock is highatomic. Signed-off-by: Minchan Kim <minchan@kernel.org> --- mm/page_alloc.c | 24 ++++++++++++++++++------ 1 file changed, 18 insertions(+), 6 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index e7cbb3cc22fa..d110cd640264 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -2133,13 +2133,25 @@ static void unreserve_highatomic_pageblock(const struct alloc_context *ac) continue; /* - * It should never happen but changes to locking could - * inadvertently allow a per-cpu drain to add pages - * to MIGRATE_HIGHATOMIC while unreserving so be safe - * and watch for underflows. + * In page freeing path, migratetype change is racy so + * we can counter several free pages in a pageblock + * in this loop althoug we changed the pageblock type + * from highatomic to ac->migratetype. So we should + * adjust the count once. */ - zone->nr_reserved_highatomic -= min(pageblock_nr_pages, - zone->nr_reserved_highatomic); + if (get_pageblock_migratetype(page) == + MIGRATE_HIGHATOMIC) { + /* + * It should never happen but changes to + * locking could inadvertently allow a per-cpu + * drain to add pages to MIGRATE_HIGHATOMIC + * while unreserving so be safe and watch for + * underflows. + */ + zone->nr_reserved_highatomic -= min( + pageblock_nr_pages, + zone->nr_reserved_highatomic); + } /* * Convert to ac->migratetype and avoid the normal -- 2.7.4 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2016-10-07 5:46 UTC|newest] Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top 2016-10-07 5:45 [PATCH 0/4] use up highorder free pages before OOM Minchan Kim 2016-10-07 5:45 ` Minchan Kim 2016-10-07 5:45 ` [PATCH 1/4] mm: adjust reserved highatomic count Minchan Kim 2016-10-07 5:45 ` Minchan Kim 2016-10-07 12:30 ` Vlastimil Babka 2016-10-07 12:30 ` Vlastimil Babka 2016-10-07 14:29 ` Minchan Kim 2016-10-07 14:29 ` Minchan Kim 2016-10-10 6:57 ` Vlastimil Babka 2016-10-10 6:57 ` Vlastimil Babka 2016-10-11 4:19 ` Minchan Kim 2016-10-11 4:19 ` Minchan Kim 2016-10-11 9:40 ` Vlastimil Babka 2016-10-11 9:40 ` Vlastimil Babka 2016-10-12 5:36 ` Mel Gorman 2016-10-12 5:36 ` Mel Gorman 2016-10-07 5:45 ` Minchan Kim [this message] 2016-10-07 5:45 ` [PATCH 2/4] mm: prevent double decrease of nr_reserved_highatomic Minchan Kim 2016-10-07 12:44 ` Vlastimil Babka 2016-10-07 12:44 ` Vlastimil Babka 2016-10-07 14:30 ` Minchan Kim 2016-10-07 14:30 ` Minchan Kim 2016-10-12 5:36 ` Mel Gorman 2016-10-12 5:36 ` Mel Gorman 2016-10-07 5:45 ` [PATCH 3/4] mm: unreserve highatomic free pages fully before OOM Minchan Kim 2016-10-07 5:45 ` Minchan Kim 2016-10-07 9:09 ` Michal Hocko 2016-10-07 9:09 ` Michal Hocko 2016-10-07 14:43 ` Minchan Kim 2016-10-07 14:43 ` Minchan Kim 2016-10-10 7:41 ` Michal Hocko 2016-10-10 7:41 ` Michal Hocko 2016-10-11 5:01 ` Minchan Kim 2016-10-11 5:01 ` Minchan Kim 2016-10-11 6:50 ` Michal Hocko 2016-10-11 6:50 ` Michal Hocko 2016-10-11 7:09 ` Minchan Kim 2016-10-11 7:09 ` Minchan Kim 2016-10-11 7:26 ` Michal Hocko 2016-10-11 7:26 ` Michal Hocko 2016-10-11 7:37 ` Minchan Kim 2016-10-11 7:37 ` Minchan Kim 2016-10-11 8:01 ` Michal Hocko 2016-10-11 8:01 ` Michal Hocko 2016-10-07 5:45 ` [PATCH 4/4] mm: skip to reserve pageblock crossed zone boundary for HIGHATOMIC Minchan Kim 2016-10-07 5:45 ` Minchan Kim 2016-10-07 9:16 ` [PATCH 0/4] use up highorder free pages before OOM Michal Hocko 2016-10-07 9:16 ` Michal Hocko 2016-10-07 15:04 ` Minchan Kim 2016-10-07 15:04 ` Minchan Kim 2016-10-10 7:47 ` Michal Hocko 2016-10-10 7:47 ` Michal Hocko 2016-10-11 5:06 ` Minchan Kim 2016-10-11 5:06 ` Minchan Kim 2016-10-11 6:53 ` Michal Hocko 2016-10-11 6:53 ` Michal Hocko
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