Commit c0bd3f63 authored Apr 30, 2009 by Daisuke Nishimura Committed by Linus Torvalds May 02, 2009

memcg: fix try_get_mem_cgroup_from_swapcache()



This is a bugfix for commit 3c776e64
("memcg: charge swapcache to proper memcg").

Used bit of swapcache is solid under page lock, but considering
move_account, pc->mem_cgroup is not.

We need lock_page_cgroup() anyway.

Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 1e50cc90

mm/memcontrol.c

+2 −3

Original line number	Diff line number	Diff line
		@@ -1024,9 +1024,7 @@ static struct mem_cgroup try_get_mem_cgroup_from_swapcache(struct page page)
		return NULL;

		pc = lookup_page_cgroup(page);
		/*
		* Used bit of swapcache is solid under page lock.
		*/
		lock_page_cgroup(pc);
		if (PageCgroupUsed(pc)) {
		mem = pc->mem_cgroup;
		if (mem && !css_tryget(&mem->css))
		@@ -1040,6 +1038,7 @@ static struct mem_cgroup try_get_mem_cgroup_from_swapcache(struct page page)
		mem = NULL;
		rcu_read_unlock();
		}
		unlock_page_cgroup(pc);
		return mem;
		}