Commit 3168ecbe authored Oct 31, 2013 by Johannes Weiner Committed by Linus Torvalds Oct 31, 2013

mm: memcg: use proper memcg in limit bypass



Commit 84235de3 ("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.  But because the main test
case was on a 3.2-based system, the 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@cmpxchg.org>
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 12aee278

mm/memcontrol.c

+4 −4

Original line number	Diff line number	Diff line
		@@ -2765,10 +2765,10 @@ done:
		*ptr = memcg;
		return 0;
		nomem:
		if (!(gfp_mask & __GFP_NOFAIL)) {
		*ptr = NULL;
		if (gfp_mask & __GFP_NOFAIL)
		return 0;
		return -ENOMEM;
		}
		bypass:
		*ptr = root_mem_cgroup;
		return -EINTR;

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