From: Johannes Weiner <hannes@cmpxchg.org>
Date: Wed, 10 Dec 2014 23:43:43 +0000 (-0800)
Subject: mm: memcontrol: update mem_cgroup_page_lruvec() documentation
X-Git-Tag: omap-for-v3.20/drop-legacy-3517~139^2~136
X-Git-Url: https://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=dfe0e773d0258a4d7dfd763e1fda04aa27680b90;p=pandora-kernel.git

mm: memcontrol: update mem_cgroup_page_lruvec() documentation

Commit 7512102cf64d ("memcg: fix GPF when cgroup removal races with last
exit") added a pc->mem_cgroup reset into mem_cgroup_page_lruvec() to
prevent a crash where an anon page gets uncharged on unmap, the memcg is
released, and then the final LRU isolation on free dereferences the
stale pc->mem_cgroup pointer.

But since commit 0a31bc97c80c ("mm: memcontrol: rewrite uncharge API"),
pages are only uncharged AFTER that final LRU isolation, which
guarantees the memcg's lifetime until then.  pc->mem_cgroup now only
needs to be reset for swapcache readahead pages.

Update the comment and callsite requirements accordingly.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Hugh Dickins <hughd@google.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>
---

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