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[PATCHv2 18/28] thp: prepare change_huge_pmd() for file thp

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  [PATCHv2 18/28] thp: prepare change_huge_pmd() for file thp "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-02-11 15:30 +0100
    Re: [PATCHv2 18/28] thp: prepare change_huge_pmd() for file thp Dave Hansen <dave.hansen@intel.com> - 2016-02-12 19:50 +0100
      Re: [PATCHv2 18/28] thp: prepare change_huge_pmd() for file thp "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-02-16 11:20 +0100

#1332062 — [PATCHv2 18/28] thp: prepare change_huge_pmd() for file thp

change_huge_pmd() has assert which is not relvant for file page.
For shared mapping it's perfectly fine to have page table entry
writable, without explicit mkwrite.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
 mm/huge_memory.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 00f10d323039..8e2d84698c15 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1756,7 +1756,6 @@ int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
 				entry = pmd_mkwrite(entry);
 			ret = HPAGE_PMD_NR;
 			set_pmd_at(mm, addr, pmd, entry);
-			BUG_ON(!preserve_write && pmd_write(entry));
 		}
 		spin_unlock(ptl);
 	}
-- 
2.7.0

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#1333028

On 02/11/2016 06:21 AM, Kirill A. Shutemov wrote:
> change_huge_pmd() has assert which is not relvant for file page.
> For shared mapping it's perfectly fine to have page table entry
> writable, without explicit mkwrite.

Should we have the bug only trigger on anonymous VMAs instead of
removing it?

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#1335253

On Fri, Feb 12, 2016 at 10:48:59AM -0800, Dave Hansen wrote:
> On 02/11/2016 06:21 AM, Kirill A. Shutemov wrote:
> > change_huge_pmd() has assert which is not relvant for file page.
> > For shared mapping it's perfectly fine to have page table entry
> > writable, without explicit mkwrite.
> 
> Should we have the bug only trigger on anonymous VMAs instead of
> removing it?

Makes sense.

-- 
 Kirill A. Shutemov

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