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authorTejun Heo <tj@kernel.org>2016-01-16 03:57:16 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2016-01-16 04:56:32 +0300
commit654a0dd0953fcd87ff7bbb468fb889f0eb67df33 (patch)
tree790401b6c2c4cde86cf94a96823c6a9102781412 /mm
parent6f8d2b8a262c6b71e1464d488f41cccf9aafbc07 (diff)
downloadlinux-654a0dd0953fcd87ff7bbb468fb889f0eb67df33.tar.xz
cgroup, memcg, writeback: drop spurious rcu locking around mem_cgroup_css_from_page()
In earlier versions, mem_cgroup_css_from_page() could return non-root css on a legacy hierarchy which can go away and required rcu locking; however, the eventual version simply returns the root cgroup if memcg is on a legacy hierarchy and thus doesn't need rcu locking around or in it. Remove spurious rcu lockings. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@kernel.org> Cc: Vladimir Davydov <vdavydov@virtuozzo.com> Cc: Jens Axboe <axboe@kernel.dk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/memcontrol.c3
1 files changed, 0 insertions, 3 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index bee6b1c9fdce..23d8cf5a86c3 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -382,14 +382,11 @@ struct cgroup_subsys_state *mem_cgroup_css_from_page(struct page *page)
{
struct mem_cgroup *memcg;
- rcu_read_lock();
-
memcg = page->mem_cgroup;
if (!memcg || !cgroup_subsys_on_dfl(memory_cgrp_subsys))
memcg = root_mem_cgroup;
- rcu_read_unlock();
return &memcg->css;
}