[PATCH] memcg: remove unnecessary thp check in mem_cgroup_update_page_stat()

[KAMEZAWA Hiroyuki]

commit 58b318ecf(memcg-devel)
    memcg: make mem_cgroup_split_huge_fixup() more efficient
removes move_lock_page_cgroup() in thp-split path.

So, We do not have to check PageTransHuge in mem_cgroup_update_page_stat
and fallback into the locked accounting because both move charge and thp
split up are done with compound_lock so they cannot race. update vs.
move is protected by the mem_cgroup_stealed sufficiently.

PageTransHuge pages shouldn't appear in this code path currently because
we are tracking only file pages at the moment but later we are planning
to track also other pages (e.g. mlocked ones).

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
---
 mm/memcontrol.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 5073474..fb2dfc3 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1801,7 +1801,7 @@ void mem_cgroup_update_page_stat(struct page *page,
 	if (unlikely(!memcg || !PageCgroupUsed(pc)))
 		goto out;
 	/* pc->mem_cgroup is unstable ? */
-	if (unlikely(mem_cgroup_stealed(memcg)) || PageTransHuge(page)) {
+	if (unlikely(mem_cgroup_stealed(memcg))) {
 		/* take a lock against to access pc->mem_cgroup */
 		move_lock_page_cgroup(pc, &flags);
 		need_unlock = true;
-- 
1.7.4.1


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