Re: [PATCH] mm: mempolicy: make mbind() return -EIO when MPOL_MF_STRICT is specified

On Wed, Mar 20, 2019 at 12:06 AM Yang Shi yang.shi@linux.alibaba.com wrote:

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...

Fixes: 6f4576e3687b ("mempolicy: apply page table walker on queue_pages_range()") Reported-by: Cyril Hrubis chrubis@suse.cz Cc: Vlastimil Babka vbabka@suse.cz Cc: stable@vger.kernel.org Suggested-by: Kirill A. Shutemov kirill@shutemov.name Signed-off-by: Yang Shi yang.shi@linux.alibaba.com Signed-off-by: Oscar Salvador osalvador@suse.de

---

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

diff --git a/mm/mempolicy.c b/mm/mempolicy.c index abe7a67..401c817 100644 --- a/mm/mempolicy.c +++ b/mm/mempolicy.c @@ -447,6 +447,13 @@ static inline bool queue_pages_required(struct page *page, return node_isset(nid, *qp->nmask) == !(flags & MPOL_MF_INVERT); }

+/*

• • The queue_pages_pmd() may have three kind of return value.
• • 1 - pages are placed on he right node or queued successfully.

Minor typo -> s/he/the ?

• • 0 - THP get 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) { @@ -456,7 +463,7 @@ static int queue_pages_pmd(pmd_t *pmd, spinlock_t *ptl, unsigned long addr, unsigned long flags;

    if (unlikely(is_pmd_migration_entry(*pmd))) {

•           ret = 1;
  

•           ret = -EIO;
            goto unlock;
    }
    page = pmd_page(*pmd);
  

@@ -473,8 +480,15 @@ static int queue_pages_pmd(pmd_t *pmd, spinlock_t *ptl, unsigned long addr, 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: @@ -499,8 +513,10 @@ static int queue_pages_pte_range(pmd_t *pmd, unsigned long addr, 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))
  

@@ -521,11 +537,16 @@ static int queue_pages_pte_range(pmd_t *pmd, unsigned long addr, 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, @@ -595,7 +616,12 @@ static int queue_pages_test_walk(unsigned long start, unsigned long end, 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)
  

@@ -622,7 +648,7 @@ static int queue_pages_test_walk(unsigned long start, unsigned long end, }

    /* queue pages from current vma */

•   if (flags & (MPOL_MF_MOVE | MPOL_MF_MOVE_ALL))
  

•   if (flags & MPOL_MF_VALID)
            return 0;
    return 1;
  

}

1.8.3.1