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    SubjectRe: [PATCH 1/9] ksm: fix mlockfreed to munlocked
    On Thu, 26 Nov 2009, Mel Gorman wrote:
    > On Tue, Nov 24, 2009 at 04:40:55PM +0000, Hugh Dickins wrote:
    > > When KSM merges an mlocked page, it has been forgetting to munlock it:
    > > that's been left to free_page_mlock(), which reports it in /proc/vmstat
    > > as unevictable_pgs_mlockfreed instead of unevictable_pgs_munlocked (and
    > > whinges "Page flag mlocked set for process" in mmotm, whereas mainline
    > > is silently forgiving). Call munlock_vma_page() to fix that.
    > >
    > > Signed-off-by: Hugh Dickins <>
    > Acked-by: Mel Gorman <>

    Rik & Mel, thanks for the Acks.

    But please clarify: that patch was for mmotm and hopefully 2.6.33,
    but the vmstat issue (minus warning message) is there in 2.6.32-rc.
    Should I

    (a) forget it for 2.6.32
    (b) rush Linus a patch for 2.6.32 final
    (c) send a patch for 2.6.32.stable later on

    ? I just don't have a feel for how important this is.

    Typically, these pages are immediately freed, and the only issue is
    which stats they get added to; but if fork has copied them into other
    mms, then such pages might stay unevictable indefinitely, despite no
    longer being in any mlocked vma.

    There's a remark in munlock_vma_page(), apropos a different issue,
    * We lost the race. let try_to_unmap() deal
    * with it. At least we get the page state and
    * mlock stats right. However, page is still on
    * the noreclaim list. We'll fix that up when
    * the page is eventually freed or we scan the
    * noreclaim list.
    which implies that sometimes we scan the unevictable list and resolve
    such cases. But I wonder if that's nowadays the case?

    > > ---
    > > Is this a fix that I ought to backport to 2.6.32? It does rely on part of
    > > an earlier patch (moved unlock_page down), so does not apply cleanly as is.


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