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    Subject[PATCH 4.19 113/134] mm: mempolicy: make mbind() return -EIO when MPOL_MF_STRICT is specified
    Date
    4.19-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Yang Shi <yang.shi@linux.alibaba.com>

    commit a7f40cfe3b7ada57af9b62fd28430eeb4a7cfcb7 upstream.

    When MPOL_MF_STRICT was specified and an existing page was already on a
    node that does not follow the policy, mbind() should return -EIO. But
    commit 6f4576e3687b ("mempolicy: apply page table walker on
    queue_pages_range()") broke the rule.

    And commit c8633798497c ("mm: mempolicy: mbind and migrate_pages support
    thp migration") didn't return the correct value for THP mbind() too.

    If MPOL_MF_STRICT is set, ignore vma_migratable() to make sure it
    reaches queue_pages_to_pte_range() or queue_pages_pmd() to check if an
    existing page was already on a node that does not follow the policy.
    And, non-migratable vma may be used, return -EIO too if MPOL_MF_MOVE or
    MPOL_MF_MOVE_ALL was specified.

    Tested with https://github.com/metan-ucw/ltp/blob/master/testcases/kernel/syscalls/mbind/mbind02.c

    [akpm@linux-foundation.org: tweak code comment]
    Link: http://lkml.kernel.org/r/1553020556-38583-1-git-send-email-yang.shi@linux.alibaba.com
    Fixes: 6f4576e3687b ("mempolicy: apply page table walker on queue_pages_range()")
    Signed-off-by: Yang Shi <yang.shi@linux.alibaba.com>
    Signed-off-by: Oscar Salvador <osalvador@suse.de>
    Reported-by: Cyril Hrubis <chrubis@suse.cz>
    Suggested-by: Kirill A. Shutemov <kirill@shutemov.name>
    Acked-by: Rafael Aquini <aquini@redhat.com>
    Reviewed-by: Oscar Salvador <osalvador@suse.de>
    Acked-by: David Rientjes <rientjes@google.com>
    Cc: Vlastimil Babka <vbabka@suse.cz>
    Cc: <stable@vger.kernel.org>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    mm/mempolicy.c | 40 +++++++++++++++++++++++++++++++++-------
    1 file changed, 33 insertions(+), 7 deletions(-)

    --- a/mm/mempolicy.c
    +++ b/mm/mempolicy.c
    @@ -428,6 +428,13 @@ static inline bool queue_pages_required(
    return node_isset(nid, *qp->nmask) == !(flags & MPOL_MF_INVERT);
    }

    +/*
    + * queue_pages_pmd() has three possible return values:
    + * 1 - pages are placed on the right node or queued successfully.
    + * 0 - THP was split.
    + * -EIO - is migration entry or MPOL_MF_STRICT was specified and an existing
    + * page was already on a node that does not follow the policy.
    + */
    static int queue_pages_pmd(pmd_t *pmd, spinlock_t *ptl, unsigned long addr,
    unsigned long end, struct mm_walk *walk)
    {
    @@ -437,7 +444,7 @@ static int queue_pages_pmd(pmd_t *pmd, s
    unsigned long flags;

    if (unlikely(is_pmd_migration_entry(*pmd))) {
    - ret = 1;
    + ret = -EIO;
    goto unlock;
    }
    page = pmd_page(*pmd);
    @@ -454,8 +461,15 @@ static int queue_pages_pmd(pmd_t *pmd, s
    ret = 1;
    flags = qp->flags;
    /* go to thp migration */
    - if (flags & (MPOL_MF_MOVE | MPOL_MF_MOVE_ALL))
    + if (flags & (MPOL_MF_MOVE | MPOL_MF_MOVE_ALL)) {
    + if (!vma_migratable(walk->vma)) {
    + ret = -EIO;
    + goto unlock;
    + }
    +
    migrate_page_add(page, qp->pagelist, flags);
    + } else
    + ret = -EIO;
    unlock:
    spin_unlock(ptl);
    out:
    @@ -480,8 +494,10 @@ static int queue_pages_pte_range(pmd_t *
    ptl = pmd_trans_huge_lock(pmd, vma);
    if (ptl) {
    ret = queue_pages_pmd(pmd, ptl, addr, end, walk);
    - if (ret)
    + if (ret > 0)
    return 0;
    + else if (ret < 0)
    + return ret;
    }

    if (pmd_trans_unstable(pmd))
    @@ -502,11 +518,16 @@ static int queue_pages_pte_range(pmd_t *
    continue;
    if (!queue_pages_required(page, qp))
    continue;
    - migrate_page_add(page, qp->pagelist, flags);
    + if (flags & (MPOL_MF_MOVE | MPOL_MF_MOVE_ALL)) {
    + if (!vma_migratable(vma))
    + break;
    + migrate_page_add(page, qp->pagelist, flags);
    + } else
    + break;
    }
    pte_unmap_unlock(pte - 1, ptl);
    cond_resched();
    - return 0;
    + return addr != end ? -EIO : 0;
    }

    static int queue_pages_hugetlb(pte_t *pte, unsigned long hmask,
    @@ -576,7 +597,12 @@ static int queue_pages_test_walk(unsigne
    unsigned long endvma = vma->vm_end;
    unsigned long flags = qp->flags;

    - if (!vma_migratable(vma))
    + /*
    + * Need check MPOL_MF_STRICT to return -EIO if possible
    + * regardless of vma_migratable
    + */
    + if (!vma_migratable(vma) &&
    + !(flags & MPOL_MF_STRICT))
    return 1;

    if (endvma > end)
    @@ -603,7 +629,7 @@ static int queue_pages_test_walk(unsigne
    }

    /* queue pages from current vma */
    - if (flags & (MPOL_MF_MOVE | MPOL_MF_MOVE_ALL))
    + if (flags & MPOL_MF_VALID)
    return 0;
    return 1;
    }

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