From: Johannes Weiner Date: Wed, 10 Dec 2014 23:44:08 +0000 (-0800) Subject: mm: memcontrol: don't pass a NULL memcg to mem_cgroup_end_move() X-Git-Tag: omap-for-v3.19/fixes-rc1~142^2~127 X-Git-Url: https://git.openpandora.org/cgi-bin/gitweb.cgi?p=pandora-kernel.git;a=commitdiff_plain;h=4e2f245d38ba86e3922c6c188fe4a0d0688aed88;hp=354a4783a2ee5ba1cb5a1442cca8ecd4c0ac6d66 mm: memcontrol: don't pass a NULL memcg to mem_cgroup_end_move() mem_cgroup_end_move() checks if the passed memcg is NULL, along with a lengthy comment to explain why this seemingly non-sensical situation is even possible. Check in cancel_attach() itself whether can_attach() set up the move context or not, it's a lot more obvious from there. Then remove the check and comment in mem_cgroup_end_move(). Signed-off-by: Johannes Weiner Acked-by: Vladimir Davydov Acked-by: Michal Hocko Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/mm/memcontrol.c b/mm/memcontrol.c index a5c9aa4688e8..3cd4f1e0bfb3 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -1469,12 +1469,7 @@ static void mem_cgroup_start_move(struct mem_cgroup *memcg) static void mem_cgroup_end_move(struct mem_cgroup *memcg) { - /* - * Now, mem_cgroup_clear_mc() may call this function with NULL. - * We check NULL in callee rather than caller. - */ - if (memcg) - atomic_dec(&memcg->moving_account); + atomic_dec(&memcg->moving_account); } /* @@ -5489,7 +5484,8 @@ static int mem_cgroup_can_attach(struct cgroup_subsys_state *css, static void mem_cgroup_cancel_attach(struct cgroup_subsys_state *css, struct cgroup_taskset *tset) { - mem_cgroup_clear_mc(); + if (mc.to) + mem_cgroup_clear_mc(); } static int mem_cgroup_move_charge_pte_range(pmd_t *pmd,