Commit 65f3975f authored by Roman Gushchin's avatar Roman Gushchin Committed by Linus Torvalds

cgroup: revert fa06235b ("cgroup: reset css on destruction")

Commit fa06235b ("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.comSigned-off-by: default avatarRoman Gushchin <guro@fb.com>
Acked-by: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 63677c74
......@@ -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);
......
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