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    SubjectRe: [-mm][PATCH 8/10] fix shmem page migration incorrectness on memcgroup
    On Fri, Jun 27, 2008 at 2:41 PM, KOSAKI Motohiro
    <kosaki.motohiro@jp.fujitsu.com> wrote:
    >> > mem_cgroup_uncharge() against old page is done after radix-tree-replacement.
    >> > And there were special handling to ingore swap-cache page. But, shmem can
    >> > be swap-cache and file-cache at the same time. Chekcing PageSwapCache() is
    >> > not correct here. Check PageAnon() instead.
    >>
    >> When/How shmem can be both swap-cache and file-cache ?
    >> I can't understand that situation.
    >
    > Hi
    >
    > see,
    >
    > shmem_writepage()
    > -> add_to_swap_cache()
    > -> SetPageSwapCache()
    >
    >
    > BTW: his file-cache mean !Anon, not mean !SwapBacked.

    Hi KOSAKI-san.
    Thanks for explaining.

    In the migrate_page_move_mapping, the page was already locked in unmap_and_move.
    Also, we have a lock for that page for calling shmem_writepage.

    So I think race problem between shmem_writepage and
    migrate_page_move_mapping don't occur.
    But I am not sure I am right.

    If I am wrong, could you tell me when race problem happen ? :)


    >
    >



    --
    Kinds regards,
    MinChan Kim


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