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    SubjectRe: [PATCH 2/2] [PATCH] Align faulting address to a hugepage boundary before unmapping
    On Thu, Jul 10, 2008 at 06:30:41PM +0100, Mel Gorman wrote:
    >
    > When taking a fault for COW on a private mapping it is possible that the
    > parent will have to steal the original page from its children due to an
    > insufficient hugepage pool. In this case, unmap_ref_private() is called
    > for the faulting address to unmap via unmap_hugepage_range(). This patch
    > ensures that the address used for unmapping is hugepage-aligned.
    >
    > Signed-off-by: Mel Gorman <mel@csn.ul.ie>

    Acked-by: Andy Whitcroft <apw@shadowen.org>

    Clearly far too many of our tests use page aligned accesss to trigger
    behaviour.

    > mm/hugetlb.c | 1 +
    > 1 file changed, 1 insertion(+)
    >
    > diff -rup -X /usr/src/patchset-0.6/bin//dontdiff linux-2.6.26-rc8-mm1-clean/mm/hugetlb.c linux-2.6.26-rc8-mm1-fix-needsreserve-check/mm/hugetlb.c
    > --- linux-2.6.26-rc8-mm1-clean/mm/hugetlb.c 2008-07-08 11:54:34.000000000 -0700
    > +++ linux-2.6.26-rc8-mm1-fix-needsreserve-check/mm/hugetlb.c 2008-07-08 15:50:00.000000000 -0700
    > @@ -1767,6 +1767,7 @@ int unmap_ref_private(struct mm_struct *
    > * vm_pgoff is in PAGE_SIZE units, hence the different calculation
    > * from page cache lookup which is in HPAGE_SIZE units.
    > */
    > + address = address & huge_page_mask(hstate_vma(vma));
    > pgoff = ((address - vma->vm_start) >> PAGE_SHIFT)
    > + (vma->vm_pgoff >> PAGE_SHIFT);
    > mapping = (struct address_space *)page_private(page);

    -apw


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