Commit 6568d4a9 authored by Johannes Weiner's avatar Johannes Weiner Committed by Linus Torvalds

mm: memcg: update the correct soft limit tree during migration

end_migration() passes the old page instead of the new page to commit
the charge.  This page descriptor is not used for committing itself,
though, since we also pass the (correct) page_cgroup descriptor.  But
it's used to find the soft limit tree through the page's zone, so the
soft limit tree of the old page's zone is updated instead of that of the
new page's, which might get slightly out of date until the next charge
reaches the ratelimit point.

This glitch has been present since 5564e88b ("memcg: condense
page_cgroup-to-page lookup points").

This fixes a bug that I introduced in 2.6.38.  It's benign enough (to my
knowledge) that we probably don't want this for stable.
Reported-by: default avatarHugh Dickins <>
Signed-off-by: default avatarJohannes Weiner <>
Acked-by: default avatarKAMEZAWA Hiroyuki <>
Acked-by: default avatarMichal Hocko <>
Acked-by: default avatarKirill A. Shutemov <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 85e72aa5
......@@ -3247,7 +3247,7 @@ int mem_cgroup_prepare_migration(struct page *page,
__mem_cgroup_commit_charge(memcg, page, 1, pc, ctype);
__mem_cgroup_commit_charge(memcg, newpage, 1, pc, ctype);
return ret;
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