Commit 4e2f245d authored Dec 10, 2014 by Johannes Weiner Committed by Linus Torvalds Dec 10, 2014

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 <hannes@cmpxchg.org>
Acked-by: Vladimir Davydov <vdavydov@parallels.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 354a4783

mm/memcontrol.c

+3 −7

Original line number	Diff line number	Diff line
		@@ -1469,11 +1469,6 @@ 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);
		}

		@@ -5489,6 +5484,7 @@ 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)
		{
		if (mc.to)
		mem_cgroup_clear_mc();
		}