* [PATCH] mm/THP: Use the right function when updating access flags
@ 2013-05-06 20:49 Aneesh Kumar K.V
2013-05-08 20:04 ` Andrew Morton
0 siblings, 1 reply; 3+ messages in thread
From: Aneesh Kumar K.V @ 2013-05-06 20:49 UTC (permalink / raw)
To: aarcange, akpm; +Cc: linux-mm, Aneesh Kumar K.V
From: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
We should use pmdp_set_access_flags to update access flags. Archs like powerpc
use extra checks(_PAGE_BUSY) when updating a hugepage PTE. A set_pmd_at doesn't
do those checks. We should use set_pmd_at only when updating a none hugepage PTE.
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
---
mm/huge_memory.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index d1cecb9..af20bb1 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1265,7 +1265,9 @@ struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
* young bit, instead of the current set_pmd_at.
*/
_pmd = pmd_mkyoung(pmd_mkdirty(*pmd));
- set_pmd_at(mm, addr & HPAGE_PMD_MASK, pmd, _pmd);
+ if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK,
+ pmd, _pmd, 1))
+ update_mmu_cache_pmd(vma, addr, pmd);
}
if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
if (page->mapping && trylock_page(page)) {
--
1.8.1.2
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^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] mm/THP: Use the right function when updating access flags
2013-05-06 20:49 [PATCH] mm/THP: Use the right function when updating access flags Aneesh Kumar K.V
@ 2013-05-08 20:04 ` Andrew Morton
2013-05-12 8:37 ` Aneesh Kumar K.V
0 siblings, 1 reply; 3+ messages in thread
From: Andrew Morton @ 2013-05-08 20:04 UTC (permalink / raw)
To: Aneesh Kumar K.V; +Cc: aarcange, linux-mm
On Tue, 7 May 2013 02:19:48 +0530 "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com> wrote:
> From: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
>
> We should use pmdp_set_access_flags to update access flags. Archs like powerpc
> use extra checks(_PAGE_BUSY) when updating a hugepage PTE. A set_pmd_at doesn't
> do those checks. We should use set_pmd_at only when updating a none hugepage PTE.
>
> ...
>
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -1265,7 +1265,9 @@ struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
> * young bit, instead of the current set_pmd_at.
> */
> _pmd = pmd_mkyoung(pmd_mkdirty(*pmd));
> - set_pmd_at(mm, addr & HPAGE_PMD_MASK, pmd, _pmd);
> + if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK,
> + pmd, _pmd, 1))
> + update_mmu_cache_pmd(vma, addr, pmd);
> }
> if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
> if (page->mapping && trylock_page(page)) {
<canned message>
When writing a changelog, please describe the end-user-visible effects
of the bug, so that others can more easily decide which kernel
version(s) should be fixed, and so that downstream kernel maintainers
can more easily work out whether this patch will fix a problem which
they or their customers are observing.
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^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] mm/THP: Use the right function when updating access flags
2013-05-08 20:04 ` Andrew Morton
@ 2013-05-12 8:37 ` Aneesh Kumar K.V
0 siblings, 0 replies; 3+ messages in thread
From: Aneesh Kumar K.V @ 2013-05-12 8:37 UTC (permalink / raw)
To: Andrew Morton; +Cc: aarcange, linux-mm
Andrew Morton <akpm@linux-foundation.org> writes:
> On Tue, 7 May 2013 02:19:48 +0530 "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com> wrote:
>
>> From: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
>>
>> We should use pmdp_set_access_flags to update access flags. Archs like powerpc
>> use extra checks(_PAGE_BUSY) when updating a hugepage PTE. A set_pmd_at doesn't
>> do those checks. We should use set_pmd_at only when updating a none hugepage PTE.
>>
>> ...
>>
>> --- a/mm/huge_memory.c
>> +++ b/mm/huge_memory.c
>> @@ -1265,7 +1265,9 @@ struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
>> * young bit, instead of the current set_pmd_at.
>> */
>> _pmd = pmd_mkyoung(pmd_mkdirty(*pmd));
>> - set_pmd_at(mm, addr & HPAGE_PMD_MASK, pmd, _pmd);
>> + if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK,
>> + pmd, _pmd, 1))
>> + update_mmu_cache_pmd(vma, addr, pmd);
>> }
>> if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
>> if (page->mapping && trylock_page(page)) {
>
> <canned message>
> When writing a changelog, please describe the end-user-visible effects
> of the bug, so that others can more easily decide which kernel
> version(s) should be fixed, and so that downstream kernel maintainers
> can more easily work out whether this patch will fix a problem which
> they or their customers are observing.
I found that reading code while debugging some crashes with THP on
ppc64. So user visible effects would mostly be some random crashes.
I will make sure to document the user visible effects next time.
-aneesh
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^ permalink raw reply [flat|nested] 3+ messages in thread
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2013-05-06 20:49 [PATCH] mm/THP: Use the right function when updating access flags Aneesh Kumar K.V
2013-05-08 20:04 ` Andrew Morton
2013-05-12 8:37 ` Aneesh Kumar K.V
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