diff options
| author |   Tejun Heo <tj@kernel.org> | 2016-01-15 16:57:16 -0800 |
|---|---|---|
| committer |   Linus Torvalds <torvalds@linux-foundation.org> | 2016-01-15 17:56:32 -0800 |
| commit | 654a0dd0953fcd87ff7bbb468fb889f0eb67df33 (patch) | |
| tree | 790401b6c2c4cde86cf94a96823c6a9102781412 | |
| parent | mm/page_isolation: do some cleanup in "undo_isolate_page_range" (diff) | |
| download | linux-dev-654a0dd0953fcd87ff7bbb468fb889f0eb67df33.tar.xz linux-dev-654a0dd0953fcd87ff7bbb468fb889f0eb67df33.zip | |
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>
| -rw-r--r-- | fs/fs-writeback.c | 2 | ||||
| -rw-r--r-- | mm/memcontrol.c | 3 |
2 files changed, 0 insertions, 5 deletions
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index 023f6a1f23cd..6915c950e6e8 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -677,9 +677,7 @@ void wbc_account_io(struct writeback_control *wbc, struct page *page, if (!wbc->wb) return; - rcu_read_lock(); id = mem_cgroup_css_from_page(page)->id; - rcu_read_unlock(); if (id == wbc->wb_id) { wbc->wb_bytes += bytes; 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; } |