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    SubjectRe: [PATCH 1/4] memcg: account swap cache under lock
    On Mon, 29 Sep 2008 19:21:23 +0900, KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:
    > While page-cache's charge/uncharge is done under page_lock(), swap-cache
    > isn't. (anonymous page is charged when it's newly allocated.)
    >
    > This patch moves do_swap_page()'s charge() call under lock.
    > I don't see any bad problem *now* but this fix will be good for future
    > for avoiding unneccesary racy state.
    >
    >
    > Changelog: (v5) -> (v6)
    > - mark_page_accessed() is moved before lock_page().
    > - fixed missing unlock_page()
    > (no changes in previous version)
    >
    > Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
    >
    Looks good to me.

    Reviewed-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>

    > mm/memory.c | 11 ++++++-----
    > 1 file changed, 6 insertions(+), 5 deletions(-)
    >
    > Index: mmotm-2.6.27-rc7+/mm/memory.c
    > ===================================================================
    > --- mmotm-2.6.27-rc7+.orig/mm/memory.c
    > +++ mmotm-2.6.27-rc7+/mm/memory.c
    > @@ -2326,16 +2326,17 @@ static int do_swap_page(struct mm_struct
    > count_vm_event(PGMAJFAULT);
    > }
    >
    > + mark_page_accessed(page);
    > +
    > + lock_page(page);
    > + delayacct_clear_flag(DELAYACCT_PF_SWAPIN);
    > +
    > if (mem_cgroup_charge(page, mm, GFP_KERNEL)) {
    > - delayacct_clear_flag(DELAYACCT_PF_SWAPIN);
    > ret = VM_FAULT_OOM;
    > + unlock_page(page);
    > goto out;
    > }
    >
    > - mark_page_accessed(page);
    > - lock_page(page);
    > - delayacct_clear_flag(DELAYACCT_PF_SWAPIN);
    > -
    > /*
    > * Back out if somebody else already faulted in this pte.
    > */
    >


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