From 6d50e60cd2edb5a57154db5a6f64eef5aa59b751 Mon Sep 17 00:00:00 2001 From: David Rientjes Date: Wed, 29 Oct 2014 14:50:31 -0700 Subject: mm, thp: fix collapsing of hugepages on madvise If an anonymous mapping is not allowed to fault thp memory and then madvise(MADV_HUGEPAGE) is used after fault, khugepaged will never collapse this memory into thp memory. This occurs because the madvise(2) handler for thp, hugepage_madvise(), clears VM_NOHUGEPAGE on the stack and it isn't stored in vma->vm_flags until the final action of madvise_behavior(). This causes the khugepaged_enter_vma_merge() to be a no-op in hugepage_madvise() when the vma had previously had VM_NOHUGEPAGE set. Fix this by passing the correct vma flags to the khugepaged mm slot handler. There's no chance khugepaged can run on this vma until after madvise_behavior() returns since we hold mm->mmap_sem. It would be possible to clear VM_NOHUGEPAGE directly from vma->vm_flags in hugepage_advise(), but I didn't want to introduce special case behavior into madvise_behavior(). I think it's best to just let it always set vma->vm_flags itself. Signed-off-by: David Rientjes Reported-by: Suleiman Souhlal Cc: "Kirill A. Shutemov" Cc: Andrea Arcangeli Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/mmap.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) (limited to 'mm/mmap.c') diff --git a/mm/mmap.c b/mm/mmap.c index 7f855206e7fb..87e82b38453c 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -1080,7 +1080,7 @@ struct vm_area_struct *vma_merge(struct mm_struct *mm, end, prev->vm_pgoff, NULL); if (err) return NULL; - khugepaged_enter_vma_merge(prev); + khugepaged_enter_vma_merge(prev, vm_flags); return prev; } @@ -1099,7 +1099,7 @@ struct vm_area_struct *vma_merge(struct mm_struct *mm, next->vm_pgoff - pglen, NULL); if (err) return NULL; - khugepaged_enter_vma_merge(area); + khugepaged_enter_vma_merge(area, vm_flags); return area; } @@ -2208,7 +2208,7 @@ int expand_upwards(struct vm_area_struct *vma, unsigned long address) } } vma_unlock_anon_vma(vma); - khugepaged_enter_vma_merge(vma); + khugepaged_enter_vma_merge(vma, vma->vm_flags); validate_mm(vma->vm_mm); return error; } @@ -2277,7 +2277,7 @@ int expand_downwards(struct vm_area_struct *vma, } } vma_unlock_anon_vma(vma); - khugepaged_enter_vma_merge(vma); + khugepaged_enter_vma_merge(vma, vma->vm_flags); validate_mm(vma->vm_mm); return error; } -- cgit v1.2.3-59-g8ed1b