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Subject[PATCH] mm/THP: use hugepage_vma_check() in khugepaged_enter_vma_merge()
Date
khugepaged_enter_vma_merge() is using a different approach to check
whether a vma is valid for khugepaged_enter():

if (!vma->anon_vma)
/*
* Not yet faulted in so we will register later in the
* page fault if needed.
*/
return 0;
if (vma->vm_ops || (vm_flags & VM_NO_KHUGEPAGED))
/* khugepaged not yet working on file or special mappings */
return 0;

This check has some problems. One of the obvious problems is that
it doesn't check shmem_file(), so that vma backed with shmem files
will not call khugepaged_enter().

This patch fixes these problems by reusing hugepage_vma_check() in
khugepaged_enter_vma_merge().

Signed-off-by: Song Liu <songliubraving@fb.com>
---
mm/khugepaged.c | 12 ++++--------
1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index d7b2a4b..e50c2bd 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -430,18 +430,14 @@ int __khugepaged_enter(struct mm_struct *mm)
return 0;
}

+static bool hugepage_vma_check(struct vm_area_struct *vma);
+
int khugepaged_enter_vma_merge(struct vm_area_struct *vma,
unsigned long vm_flags)
{
unsigned long hstart, hend;
- if (!vma->anon_vma)
- /*
- * Not yet faulted in so we will register later in the
- * page fault if needed.
- */
- return 0;
- if (vma->vm_ops || (vm_flags & VM_NO_KHUGEPAGED))
- /* khugepaged not yet working on file or special mappings */
+
+ if (!hugepage_vma_check(vma))
return 0;
hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
hend = vma->vm_end & HPAGE_PMD_MASK;
--
2.9.5
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