From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f199.google.com (mail-pf0-f199.google.com [209.85.192.199]) by kanga.kvack.org (Postfix) with ESMTP id 856AF6B0279 for ; Wed, 24 May 2017 22:20:21 -0400 (EDT) Received: by mail-pf0-f199.google.com with SMTP id e7so205768546pfk.9 for ; Wed, 24 May 2017 19:20:21 -0700 (PDT) Received: from szxga01-in.huawei.com (szxga01-in.huawei.com. [45.249.212.187]) by mx.google.com with ESMTPS id e19si26270903pgk.199.2017.05.24.19.20.20 for (version=TLS1 cipher=AES128-SHA bits=128/128); Wed, 24 May 2017 19:20:20 -0700 (PDT) From: Yisheng Xie Subject: [PATCH v2] mlock: fix mlock count can not decrease in race condition Date: Thu, 25 May 2017 10:13:25 +0800 Message-ID: <1495678405-54569-1-git-send-email-xieyisheng1@huawei.com> MIME-Version: 1.0 Content-Type: text/plain Sender: owner-linux-mm@kvack.org List-ID: To: akpm@linux-foundation.org Cc: vbabka@suse.cz, joern@logfs.org, mgorman@suse.de, walken@google.com, hughd@google.com, riel@redhat.com, hannes@cmpxchg.org, mhocko@suse.cz, qiuxishi@huawei.com, zhongjiang@huawei.com, guohanjun@huawei.com, wangkefeng.wang@huawei.com, stable@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Kefeng reported that when run the follow test the mlock count in meminfo cannot be decreased: [1] testcase linux:~ # cat test_mlockal grep Mlocked /proc/meminfo for j in `seq 0 10` do for i in `seq 4 15` do ./p_mlockall >> log & done sleep 0.2 done # wait some time to let mlock counter decrease and 5s may not enough sleep 5 grep Mlocked /proc/meminfo linux:~ # cat p_mlockall.c #include #include #include #define SPACE_LEN 4096 int main(int argc, char ** argv) { int ret; void *adr = malloc(SPACE_LEN); if (!adr) return -1; ret = mlockall(MCL_CURRENT | MCL_FUTURE); printf("mlcokall ret = %d\n", ret); ret = munlockall(); printf("munlcokall ret = %d\n", ret); free(adr); return 0; } When __munlock_pagevec, we ClearPageMlock but isolation_failed in race condition, and we do not count these page into delta_munlocked, which cause mlock counter incorrect for we had Clear the PageMlock and cannot count down the number in the feture. Fix it by count the number of page whoes PageMlock flag is cleared. Fixes: 1ebb7cc6a583 (" mm: munlock: batch NR_MLOCK zone state updates") Signed-off-by: Yisheng Xie Reported-by: Kefeng Wang Tested-by: Kefeng Wang Cc: Vlastimil Babka Cc: Joern Engel Cc: Mel Gorman Cc: Michel Lespinasse Cc: Hugh Dickins Cc: Rik van Riel Cc: Johannes Weiner Cc: Michal Hocko Cc: Xishi Qiu CC: zhongjiang Cc: Hanjun Guo Cc: --- v2: - use delta_munlocked for it doesn't do the increment in fastpath - Vlastimil Hi Andrew: Could you please help to fold this? Thanks Yisheng Xie mm/mlock.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/mm/mlock.c b/mm/mlock.c index c483c5c..b562b55 100644 --- a/mm/mlock.c +++ b/mm/mlock.c @@ -284,7 +284,7 @@ static void __munlock_pagevec(struct pagevec *pvec, struct zone *zone) { int i; int nr = pagevec_count(pvec); - int delta_munlocked; + int delta_munlocked = -nr; struct pagevec pvec_putback; int pgrescued = 0; @@ -304,6 +304,8 @@ static void __munlock_pagevec(struct pagevec *pvec, struct zone *zone) continue; else __munlock_isolation_failed(page); + } else { + delta_munlocked++; } /* @@ -315,7 +317,6 @@ static void __munlock_pagevec(struct pagevec *pvec, struct zone *zone) pagevec_add(&pvec_putback, pvec->pages[i]); pvec->pages[i] = NULL; } - delta_munlocked = -nr + pagevec_count(&pvec_putback); __mod_zone_page_state(zone, NR_MLOCK, delta_munlocked); spin_unlock_irq(zone_lru_lock(zone)); -- 1.7.12.4 -- 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: email@kvack.org