The patch titled
Subject: memcg: fix destination cgroup leak on task charges migration
has been added to the -mm tree. Its filename is
memcg-fix-destination-cgroup-leak-on-task-charges-migration.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/memcg-fix-destination-cgroup-leak-on-task-charges-migration.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/memcg-fix-destination-cgroup-leak-on-task-charges-migration.patch
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------------------------------------------------------
From: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx>
Subject: memcg: fix destination cgroup leak on task charges migration
We are supposed to take one css reference per each memory page and per
each swap entry accounted to a memory cgroup. However, during task
charges migration we take a reference to the destination cgroup twice per
each swap entry: first in mem_cgroup_do_precharge()->try_charge() and then
in mem_cgroup_move_swap_account(), permanently leaking the destination
cgroup.
The hunk taking the second reference seems to be a leftover from the
pre-00501b531c472 ("mm: memcontrol: rewrite charge API") era. Remove it
to fix the leak.
Signed-off-by: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memcontrol.c | 12 ------------
1 file changed, 12 deletions(-)
diff -puN mm/memcontrol.c~memcg-fix-destination-cgroup-leak-on-task-charges-migration mm/memcontrol.c
--- a/mm/memcontrol.c~memcg-fix-destination-cgroup-leak-on-task-charges-migration
+++ a/mm/memcontrol.c
@@ -3043,18 +3043,6 @@ static int mem_cgroup_move_swap_account(
if (swap_cgroup_cmpxchg(entry, old_id, new_id) == old_id) {
mem_cgroup_swap_statistics(from, false);
mem_cgroup_swap_statistics(to, true);
- /*
- * This function is only called from task migration context now.
- * It postpones page_counter and refcount handling till the end
- * of task migration(mem_cgroup_clear_mc()) for performance
- * improvement. But we cannot postpone css_get(to) because if
- * the process that has been moved to @to does swap-in, the
- * refcount of @to might be decreased to 0.
- *
- * We are in attach() phase, so the cgroup is guaranteed to be
- * alive, so we can just call css_get().
- */
- css_get(&to->css);
return 0;
}
return -EINVAL;
_
Patches currently in -mm which might be from vdavydov@xxxxxxxxxxxxx are
memcg-fix-destination-cgroup-leak-on-task-charges-migration.patch
memcg-zap-__memcg_chargeuncharge_slab.patch
memcg-zap-memcg_name-argument-of-memcg_create_kmem_cache.patch
memcg-zap-memcg_slab_caches-and-memcg_slab_mutex.patch
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