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| author | Hugh Dickins <hughd@google.com> | 2020-07-23 21:15:24 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2020-07-29 10:18:43 +0200 |
| commit | db949f60d98317bafaf3041976c9e63e600af793 (patch) | |
| tree | 781110afce344802274ebb7f375a7e291bb287ad | |
| parent | 549bfc14270681cd776c6d9b78fe544cbd21673a (diff) | |
| download | linux-stable-db949f60d98317bafaf3041976c9e63e600af793.tar.gz linux-stable-db949f60d98317bafaf3041976c9e63e600af793.tar.bz2 linux-stable-db949f60d98317bafaf3041976c9e63e600af793.zip | |
mm/memcg: fix refcount error while moving and swapping
commit 8d22a9351035ef2ff12ef163a1091b8b8cf1e49c upstream.
It was hard to keep a test running, moving tasks between memcgs with
move_charge_at_immigrate, while swapping: mem_cgroup_id_get_many()'s
refcount is discovered to be 0 (supposedly impossible), so it is then
forced to REFCOUNT_SATURATED, and after thousands of warnings in quick
succession, the test is at last put out of misery by being OOM killed.
This is because of the way moved_swap accounting was saved up until the
task move gets completed in __mem_cgroup_clear_mc(), deferred from when
mem_cgroup_move_swap_account() actually exchanged old and new ids.
Concurrent activity can free up swap quicker than the task is scanned,
bringing id refcount down 0 (which should only be possible when
offlining).
Just skip that optimization: do that part of the accounting immediately.
Fixes: 615d66c37c75 ("mm: memcontrol: fix memcg id ref counter on swap charge move")
Signed-off-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Alex Shi <alex.shi@linux.alibaba.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Alex Shi <alex.shi@linux.alibaba.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: <stable@vger.kernel.org>
Link: http://lkml.kernel.org/r/alpine.LSU.2.11.2007071431050.4726@eggly.anvils
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | mm/memcontrol.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c index a3f4c35bb5fa..402c8bc65e08 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -5770,7 +5770,6 @@ static void __mem_cgroup_clear_mc(void) if (!mem_cgroup_is_root(mc.to)) page_counter_uncharge(&mc.to->memory, mc.moved_swap); - mem_cgroup_id_get_many(mc.to, mc.moved_swap); css_put_many(&mc.to->css, mc.moved_swap); mc.moved_swap = 0; @@ -5961,7 +5960,8 @@ put: /* get_mctgt_type() gets the page */ ent = target.ent; if (!mem_cgroup_move_swap_account(ent, mc.from, mc.to)) { mc.precharge--; - /* we fixup refcnts and charges later. */ + mem_cgroup_id_get_many(mc.to, 1); + /* we fixup other refcnts and charges later. */ mc.moved_swap++; } break; |