diff options
authorYisheng Xie <xieyisheng1@huawei.com>2017-06-02 14:46:43 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2017-06-02 15:07:38 -0700
commit70feee0e1ef331b22cc51f383d532a0d043fbdcc (patch)
parent30809f559a0d348c2dfd7ab05e9a451e2384962e (diff)
mlock: fix mlock count can not decrease in race condition
Kefeng reported that when running the follow test, the mlock count in meminfo will increase permanently: [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 <sys/mman.h> #include <stdlib.h> #include <stdio.h> #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; } In __munlock_pagevec() we should decrement NR_MLOCK for each page where we clear the PageMlocked flag. Commit 1ebb7cc6a583 ("mm: munlock: batch NR_MLOCK zone state updates") has introduced a bug where we don't decrement NR_MLOCK for pages where we clear the flag, but fail to isolate them from the lru list (e.g. when the pages are on some other cpu's percpu pagevec). Since PageMlocked stays cleared, the NR_MLOCK accounting gets permanently disrupted by this. Fix it by counting the number of page whose PageMlock flag is cleared. Fixes: 1ebb7cc6a583 (" mm: munlock: batch NR_MLOCK zone state updates") Link: http://lkml.kernel.org/r/1495678405-54569-1-git-send-email-xieyisheng1@huawei.com Signed-off-by: Yisheng Xie <xieyisheng1@huawei.com> Reported-by: Kefeng Wang <wangkefeng.wang@huawei.com> Tested-by: Kefeng Wang <wangkefeng.wang@huawei.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Joern Engel <joern@logfs.org> Cc: Mel Gorman <mgorman@suse.de> Cc: Michel Lespinasse <walken@google.com> Cc: Hugh Dickins <hughd@google.com> Cc: Rik van Riel <riel@redhat.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@suse.cz> Cc: Xishi Qiu <qiuxishi@huawei.com> Cc: zhongjiang <zhongjiang@huawei.com> Cc: Hanjun Guo <guohanjun@huawei.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 files changed, 3 insertions, 2 deletions
diff --git a/mm/mlock.c b/mm/mlock.c
index c483c5c20b4b..b562b5523a65 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)
+ } 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);