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    Subject[PATCH 1/6] Revert "mm: mempolicy: Let vma_merge and vma_split handle vma->vm_policy linkages"
    Date
    From: KOSAKI Motohiro <kosaki.motohiro@gmail.com>

    commit 05f144a0d5 "mm: mempolicy: Let vma_merge and vma_split handle
    vma->vm_policy linkages" removed a vma->vm_policy updates. But it is
    a primary purpose of mbind_range(). Now, mbind(2) is no-op in several
    case unintentionally. It is not ideal fix. This patch reverts it.

    Cc: Dave Jones <davej@redhat.com>,
    Cc: Mel Gorman <mgorman@suse.de>
    Cc: Christoph Lameter <cl@linux.com>,
    Cc: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
    ---
    mm/mempolicy.c | 41 ++++++++++++++++++++++++-----------------
    1 files changed, 24 insertions(+), 17 deletions(-)

    diff --git a/mm/mempolicy.c b/mm/mempolicy.c
    index f15c1b2..0a60def 100644
    --- a/mm/mempolicy.c
    +++ b/mm/mempolicy.c
    @@ -607,6 +607,27 @@ check_range(struct mm_struct *mm, unsigned long start, unsigned long end,
    return first;
    }

    +/* Apply policy to a single VMA */
    +static int policy_vma(struct vm_area_struct *vma, struct mempolicy *new)
    +{
    + int err = 0;
    + struct mempolicy *old = vma->vm_policy;
    +
    + pr_debug("vma %lx-%lx/%lx vm_ops %p vm_file %p set_policy %p\n",
    + vma->vm_start, vma->vm_end, vma->vm_pgoff,
    + vma->vm_ops, vma->vm_file,
    + vma->vm_ops ? vma->vm_ops->set_policy : NULL);
    +
    + if (vma->vm_ops && vma->vm_ops->set_policy)
    + err = vma->vm_ops->set_policy(vma, new);
    + if (!err) {
    + mpol_get(new);
    + vma->vm_policy = new;
    + mpol_put(old);
    + }
    + return err;
    +}
    +
    /* Step 2: apply policy to a range and do splits. */
    static int mbind_range(struct mm_struct *mm, unsigned long start,
    unsigned long end, struct mempolicy *new_pol)
    @@ -655,23 +676,9 @@ static int mbind_range(struct mm_struct *mm, unsigned long start,
    if (err)
    goto out;
    }
    -
    - /*
    - * Apply policy to a single VMA. The reference counting of
    - * policy for vma_policy linkages has already been handled by
    - * vma_merge and split_vma as necessary. If this is a shared
    - * policy then ->set_policy will increment the reference count
    - * for an sp node.
    - */
    - pr_debug("vma %lx-%lx/%lx vm_ops %p vm_file %p set_policy %p\n",
    - vma->vm_start, vma->vm_end, vma->vm_pgoff,
    - vma->vm_ops, vma->vm_file,
    - vma->vm_ops ? vma->vm_ops->set_policy : NULL);
    - if (vma->vm_ops && vma->vm_ops->set_policy) {
    - err = vma->vm_ops->set_policy(vma, new_pol);
    - if (err)
    - goto out;
    - }
    + err = policy_vma(vma, new_pol);
    + if (err)
    + goto out;
    }

    out:
    --
    1.7.1


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