[PATCH mmotm/next] memcg-mm-introduce-lowlimit-reclaim-fix2.patch

[Hugh Dickins <hughd@google.com>]

mem_cgroup_within_guarantee() oopses in _raw_spin_lock_irqsave() when
booted with cgroup_disable=memory.  Fix that in the obvious inelegant
way for now - though I hope we are moving towards a world in which
almost all of the mem_cgroup_disabled() tests will vanish, with a
root_mem_cgroup which can handle the basics even when disabled.

I bet there's a neater way of doing this, rearranging the loop (and we
shall want to avoid spinlocking on root_mem_cgroup when we reach that
new world), but that's the kind of thing I'd get wrong in a hurry!

Signed-off-by: Hugh Dickins <hughd@google.com>
---

 mm/memcontrol.c |    3 +++
 1 file changed, 3 insertions(+)

--- mmotm/mm/memcontrol.c	2014-05-21 18:12:18.072022438 -0700
+++ linux/mm/memcontrol.c	2014-05-21 19:34:30.608546905 -0700
@@ -2793,6 +2793,9 @@ static struct mem_cgroup *mem_cgroup_loo
 bool mem_cgroup_within_guarantee(struct mem_cgroup *memcg,
 		struct mem_cgroup *root)
 {
+	if (mem_cgroup_disabled())
+		return false;
+
 	do {
 		if (!res_counter_low_limit_excess(&memcg->res))
 			return true;

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