[patch 1/3] mm: memcg: use proper memcg in limit bypass

From: Johannes Weiner
Date: Wed Oct 30 2013 - 17:58:21 EST

84235de ("fs: buffer: move allocation failure loop into the
allocator") allowed __GFP_NOFAIL allocations to bypass the limit if
they fail to reclaim enough memory for the charge. Because the main
test case was on a 3.2-based system, this patch missed the fact that
on newer kernels the charge function needs to return root_mem_cgroup
when bypassing the limit, and not NULL. This will corrupt whatever
memory is at NULL + percpu pointer offset. Fix this quickly before
problems are reported.

Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx>
mm/memcontrol.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 34d3ca9572d6..13a9c80d5708 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2765,10 +2765,10 @@ static int __mem_cgroup_try_charge(struct mm_struct *mm,
*ptr = memcg;
return 0;
- *ptr = NULL;
- if (gfp_mask & __GFP_NOFAIL)
- return 0;
- return -ENOMEM;
+ if (!(gfp_mask & __GFP_NOFAIL)) {
+ *ptr = NULL;
+ return -ENOMEM;
+ }
*ptr = root_mem_cgroup;
return -EINTR;

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