On Fri, Jan 29, 2016 at 1:35 PM, Kirill A. Shutemov
<kirill.shutemov@xxxxxxxxxxxxxxx> wrote:
> From 691a961bb401c5815ed741dac63591efbc6027e3 Mon Sep 17 00:00:00 2001
> From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
> Date: Fri, 29 Jan 2016 15:06:17 +0300
> Subject: [PATCH 2/2] mempolicy: do not try to queue pages from
> !vma_migratable()
>
> Maybe I miss some point, but I don't see a reason why we try to queue
> pages from non migratable VMAs.
>
> The only case when we can queue pages from such VMA is MPOL_MF_STRICT
> plus MPOL_MF_MOVE or MPOL_MF_MOVE_ALL for VMA which has pages on LRU,
> but gfp mask is not sutable for migaration (see mapping_gfp_mask() check
> in vma_migratable()). That's looks like a bug to me.
>
> Let's filter out non-migratable vma at start of queue_pages_test_walk()
> and go to queue_pages_pte_range() only if MPOL_MF_MOVE or
> MPOL_MF_MOVE_ALL flag is set.
I've run the fuzzer with these two patches for the weekend and seen no crashes.
I guess we can consider this as fixed.
Thanks!
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
> ---
> mm/mempolicy.c | 14 +++++---------
> 1 file changed, 5 insertions(+), 9 deletions(-)
>
> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> index 27d135408a22..4c4187c0e1de 100644
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -548,8 +548,7 @@ retry:
> goto retry;
> }
>
> - if (flags & (MPOL_MF_MOVE | MPOL_MF_MOVE_ALL))
> - migrate_page_add(page, qp->pagelist, flags);
> + migrate_page_add(page, qp->pagelist, flags);
> }
> pte_unmap_unlock(pte - 1, ptl);
> cond_resched();
> @@ -625,7 +624,7 @@ 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->vm_flags & VM_PFNMAP)
> + if (!vma_migratable(vma))
> return 1;
>
> if (endvma > end)
> @@ -644,16 +643,13 @@ static int queue_pages_test_walk(unsigned long start, unsigned long end,
>
> if (flags & MPOL_MF_LAZY) {
> /* Similar to task_numa_work, skip inaccessible VMAs */
> - if (vma_migratable(vma) &&
> - vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))
> + if (vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))
> change_prot_numa(vma, start, endvma);
> return 1;
> }
>
> - if ((flags & MPOL_MF_STRICT) ||
> - ((flags & (MPOL_MF_MOVE | MPOL_MF_MOVE_ALL)) &&
> - vma_migratable(vma)))
> - /* queue pages from current vma */
> + /* queue pages from current vma */
> + if (flags & (MPOL_MF_MOVE | MPOL_MF_MOVE_ALL))
> return 0;
> return 1;
> }
> --
> 2.7.0.rc3
>
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