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    SubjectRe: [PATCH 5/5] extend KSM refcounts to the anon_vma root
    On Wed, May 26, 2010 at 03:41:24PM -0400, Rik van Riel wrote:
    > Subject: extend KSM refcounts to the anon_vma root
    >
    > KSM reference counts can cause an anon_vma to exist after the processe
    > it belongs to have already exited. Because the anon_vma lock now lives
    > in the root anon_vma, we need to ensure that the root anon_vma stays
    > around until after all the "child" anon_vmas have been freed.
    >
    > The obvious way to do this is to have a "child" anon_vma take a
    > reference to the root in anon_vma_fork. When the anon_vma is freed
    > at munmap or process exit, we drop the refcount in anon_vma_unlink
    > and possibly free the root anon_vma.
    >
    > The KSM anon_vma reference count function also needs to be modified
    > to deal with the possibility of freeing 2 levels of anon_vma. The
    > easiest way to do this is to break out the KSM magic and make it
    > generic.
    >
    > When compiling without CONFIG_KSM, this code is compiled out.
    >
    > Signed-off-by: Rik van Riel <riel@redhat.com>

    Acked-by: Mel Gorman <mel@csn.ul.ie>

    --
    Mel Gorman
    Part-time Phd Student Linux Technology Center
    University of Limerick IBM Dublin Software Lab


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