From 65f3975f3584eee2da88b11f06f66e2d39fd30d0 Mon Sep 17 00:00:00 2001 From: Roman Gushchin Date: Wed, 6 Sep 2017 16:21:50 -0700 Subject: [PATCH] cgroup: revert fa06235b8eb0 ("cgroup: reset css on destruction") Commit fa06235b8eb0 ("cgroup: reset css on destruction") caused css_reset callback to be called from the offlining path. Although it solves the problem mentioned in the commit description ("For instance, memory cgroup needs to reset memory.low, otherwise pages charged to a dead cgroup might never get reclaimed."), generally speaking, it's not correct. An offline cgroup can still be a resource domain, and we shouldn't grant it more resources than it had before deletion. For instance, if an offline memory cgroup has dirty pages, we should still imply i/o limits during writeback. The css_reset callback is designed to return the cgroup state into the original state, that means reset all limits and counters. It's spomething different from the offlining, and we shouldn't use it from the offlining path. Instead, we should adjust necessary settings from the per-controller css_offline callbacks (e.g. reset memory.low). Link: http://lkml.kernel.org/r/20170727130428.28856-2-guro@fb.com Signed-off-by: Roman Gushchin Acked-by: Tejun Heo Acked-by: Johannes Weiner Cc: Vladimir Davydov Cc: Michal Hocko Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/cgroup/cgroup.c | 3 --- 1 file changed, 3 deletions(-) diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c index df2e0f1..f64fc96 100644 --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -4100,9 +4100,6 @@ static void offline_css(struct cgroup_subsys_state *css) if (!(css->flags & CSS_ONLINE)) return; - if (ss->css_reset) - ss->css_reset(css); - if (ss->css_offline) ss->css_offline(css); -- 2.7.4