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    Subject[PATCHv11 33/37] migrate_pages: try to split pages on qeueuing
    Date
    We are not able to migrate THPs. It means it's not enough to split only
    PMD on migration -- we need to split compound page under it too.

    Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
    Tested-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
    Acked-by: Jerome Marchand <jmarchan@redhat.com>
    ---
    mm/mempolicy.c | 37 +++++++++++++++++++++++++++++++++----
    1 file changed, 33 insertions(+), 4 deletions(-)

    diff --git a/mm/mempolicy.c b/mm/mempolicy.c
    index 8102f30a3895..8f128379172e 100644
    --- a/mm/mempolicy.c
    +++ b/mm/mempolicy.c
    @@ -489,14 +489,31 @@ static int queue_pages_pte_range(pmd_t *pmd, unsigned long addr,
    struct page *page;
    struct queue_pages *qp = walk->private;
    unsigned long flags = qp->flags;
    - int nid;
    + int nid, ret;
    pte_t *pte;
    spinlock_t *ptl;

    - split_huge_pmd(vma, pmd, addr);
    - if (pmd_trans_unstable(pmd))
    - return 0;
    + if (pmd_trans_huge(*pmd)) {
    + ptl = pmd_lock(walk->mm, pmd);
    + if (pmd_trans_huge(*pmd)) {
    + page = pmd_page(*pmd);
    + if (is_huge_zero_page(page)) {
    + spin_unlock(ptl);
    + split_huge_pmd(vma, pmd, addr);
    + } else {
    + get_page(page);
    + spin_unlock(ptl);
    + lock_page(page);
    + ret = split_huge_page(page);
    + unlock_page(page);
    + put_page(page);
    + if (ret)
    + return 0;
    + }
    + }
    + }

    +retry:
    pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);
    for (; addr != end; pte++, addr += PAGE_SIZE) {
    if (!pte_present(*pte))
    @@ -513,6 +530,18 @@ static int queue_pages_pte_range(pmd_t *pmd, unsigned long addr,
    nid = page_to_nid(page);
    if (node_isset(nid, *qp->nmask) == !!(flags & MPOL_MF_INVERT))
    continue;
    + if (PageTail(page) && PageAnon(page)) {
    + get_page(page);
    + pte_unmap_unlock(pte - 1, ptl);
    + lock_page(page);
    + ret = split_huge_page(page);
    + unlock_page(page);
    + put_page(page);
    + /* Failed to split -- skip. */
    + if (ret)
    + continue;
    + goto retry;
    + }

    if (flags & (MPOL_MF_MOVE | MPOL_MF_MOVE_ALL))
    migrate_page_add(page, qp->pagelist, flags);
    --
    2.5.1


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