memcg: swapout refcnt fix
css's refcnt is dropped before end of following access.
Hold it until end of access.
Reported-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: Hugh Dickins <hugh@veritas.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 6ad309e..964a700 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1171,7 +1171,9 @@
mz = page_cgroup_zoneinfo(pc);
unlock_page_cgroup(pc);
- css_put(&mem->css);
+ /* at swapout, this memcg will be accessed to record to swap */
+ if (ctype != MEM_CGROUP_CHARGE_TYPE_SWAPOUT)
+ css_put(&mem->css);
return mem;
@@ -1212,6 +1214,8 @@
swap_cgroup_record(ent, memcg);
mem_cgroup_get(memcg);
}
+ if (memcg)
+ css_put(&memcg->css);
}
#ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP