[PATCH] mm: mempolicy: skip non-migratable VMAs when setting MPOL_MF_LAZY

[PATCH] mm: mempolicy: skip non-migratable VMAs when setting MPOL_MF_LAZY

[Liang Chen]

MPOL_MF_LAZY is not visible from userspace since 'commit a720094ded8c
("mm: mempolicy: Hide MPOL_NOOP and MPOL_MF_LAZY from userspace for now")'
, but it should still skip non-migratable VMAs.

Signed-off-by: Liang Chen <liangchen.linux@gmail.com>
Signed-off-by: Gavin Guo <gavin.guo@canonical.com>
---
We have been evaluating the enablement of MPOL_MF_LAZY again, and found
this issue. And we decided to push this patch upstream no matter if we
finally determine to propose re-enablement of MPOL_MF_LAZY or not. Since
it can be a potential problem even if MPOL_MF_LAZY is not enabled this
time.

 mm/mempolicy.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 87a1779..436ff411 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -610,7 +610,8 @@ 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->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))
+		if (vma_migratable(vma) &&
+			vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))
 			change_prot_numa(vma, start, endvma);
 		return 1;
 	}
-- 
1.9.1

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Re: [PATCH] mm: mempolicy: skip non-migratable VMAs when setting MPOL_MF_LAZY

[Rik van Riel]

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On 01/06/2016 09:18 AM, Liang Chen wrote:
> MPOL_MF_LAZY is not visible from userspace since 'commit
> a720094ded8c ("mm: mempolicy: Hide MPOL_NOOP and MPOL_MF_LAZY from
> userspace for now")' , but it should still skip non-migratable
> VMAs.

The changelog could use a better description of exactly
what the issue is, and why calling change_prot_numa
on a non-migratable VMA is causing problems.

> Signed-off-by: Liang Chen <liangchen.linux@gmail.com> 
> Signed-off-by: Gavin Guo <gavin.guo@canonical.com>

For the code itself:

Acked-by: Rik van Riel <riel@redhat.com>

Please resubmit with a better changelog.
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