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page_cgroup: fix horrid swap accounting regression

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Why is memcg's swap accounting so broken? Insane counts, wrong
ownership, unfreeable structures, which later get freed and then
accessed after free.

Turns out to be a tiny a little 3.3-rc1 regression in 9fb4b7cc07
"page_cgroup: add helper function to get swap_cgroup": the helper
function (actually named lookup_swap_cgroup()) returns an address using
void* arithmetic, but the structure in question is a short.

Signed-off-by: Hugh Dickins <hughd@google.com>
Reviewed-by: Bob Liu <lliubbo@gmail.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Johannes Weiner <jweiner@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Hugh Dickins 2012-03-05 20:52:55 -08:00 committed by Linus Torvalds
parent f3969bf78f
commit c09ff089aa
1 changed files with 3 additions and 1 deletions
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4
mm/page_cgroup.c
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@ -379,13 +379,15 @@ static struct swap_cgroup *lookup_swap_cgroup(swp_entry_t ent,
pgoff_t offset = swp_offset(ent);
struct swap_cgroup_ctrl *ctrl;
struct page *mappage;
struct swap_cgroup *sc;
ctrl = &swap_cgroup_ctrl[swp_type(ent)];
if (ctrlp)
*ctrlp = ctrl;
mappage = ctrl->map[offset / SC_PER_PAGE];
return page_address(mappage) + offset % SC_PER_PAGE;
sc = page_address(mappage);
return sc + offset % SC_PER_PAGE;
}
/**