Re: [PATCH 3/3] memcg: fix race at move_parent aroundcompound_order()

From: Daisuke Nishimura
Date: Tue Jan 25 2011 - 03:33:13 EST


On Tue, 25 Jan 2011 15:05:16 +0900
KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote:

> Based on
> 2.6.38-rc2 +
> mm-memcontrolc-fix-uninitialized-variable-use-in-mem_cgroup_move_parent.patch
> ==
> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
>
> A fix up mem_cgroup_move_parent() which use compound_order() in
> asynchrnous manner. This compound_order() may return unknown value
> because we don't take lock. Use PageTransHuge() and HPAGE_SIZE instead of
> it.
>
> Also clean up for mem_cgroup_move_parent().
> - remove unnecessary initialization of local variable.
> - rename charge_size -> page_size
> - remove unnecessary (wrong) comment.
> - added a comment about THP.
>
> Changelog:
> - fixed page size calculation for avoiding race.
>
> Note:
> Current design take compound_page_lock() in caller of move_account().
> This should be revisited when we implement direct move_task of hugepage
> without splitting.
>
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>

Acked-by: Daisuke Nishimura <nishimura@xxxxxxxxxxxxxxxxx>
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