4.20-stable review patch. If anyone has any objections, please let me know.
------------------ From: Michal Hocko <[email protected]> commit 7056d3a37d2c6aaaab10c13e8e69adc67ec1fc65 upstream. Burt Holzman has noticed that memcg v1 doesn't notify about OOM events via eventfd anymore. The reason is that 29ef680ae7c2 ("memcg, oom: move out_of_memory back to the charge path") has moved the oom handling back to the charge path. While doing so the notification was left behind in mem_cgroup_oom_synchronize. Fix the issue by replicating the oom hierarchy locking and the notification. Link: http://lkml.kernel.org/r/[email protected] Fixes: 29ef680ae7c2 ("memcg, oom: move out_of_memory back to the charge path") Signed-off-by: Michal Hocko <[email protected]> Reported-by: Burt Holzman <[email protected]> Acked-by: Johannes Weiner <[email protected]> Cc: Vladimir Davydov <[email protected] Cc: <[email protected]> [4.19+] Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- mm/memcontrol.c | 20 ++++++++++++++++++-- 1 file changed, 18 insertions(+), 2 deletions(-) --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -1666,6 +1666,9 @@ enum oom_status { static enum oom_status mem_cgroup_oom(struct mem_cgroup *memcg, gfp_t mask, int order) { + enum oom_status ret; + bool locked; + if (order > PAGE_ALLOC_COSTLY_ORDER) return OOM_SKIPPED; @@ -1700,10 +1703,23 @@ static enum oom_status mem_cgroup_oom(st return OOM_ASYNC; } + mem_cgroup_mark_under_oom(memcg); + + locked = mem_cgroup_oom_trylock(memcg); + + if (locked) + mem_cgroup_oom_notify(memcg); + + mem_cgroup_unmark_under_oom(memcg); if (mem_cgroup_out_of_memory(memcg, mask, order)) - return OOM_SUCCESS; + ret = OOM_SUCCESS; + else + ret = OOM_FAILED; + + if (locked) + mem_cgroup_oom_unlock(memcg); - return OOM_FAILED; + return ret; } /**
