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Date: Sat, 02 Apr 2016 18:37:44 +0300 From: Konstantin Khlebnikov <koct9i@...il.com> To: linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org> Cc: Dmitry Vyukov <dvyukov@...gle.com>, Andrea Arcangeli <aarcange@...hat.com>, linux-kernel@...r.kernel.org, stable <stable@...r.kernel.org> Subject: [PATCH] mm/huge_memory: replace VM_NO_THP VM_BUG_ON with actual VMA check Khugepaged detects own VMAs by checking vm_file and vm_ops but this way it cannot distinguish private /dev/zero mappings from other special mappings like /dev/hpet which has no vm_ops and popultes PTEs in mmap. This fixes false-positive VM_BUG_ON and prevents installing THP where they are not expected. Signed-off-by: Konstantin Khlebnikov <koct9i@...il.com> Reported-by: Dmitry Vyukov <dvyukov@...gle.com> Link: http://lkml.kernel.org/r/CACT4Y+ZmuZMV5CjSFOeXviwQdABAgT7T+StKfTqan9YDtgEi5g@mail.gmail.com Fixes: 78f11a255749 ("mm: thp: fix /dev/zero MAP_PRIVATE and vm_flags cleanups") Cc: stable <stable@...r.kernel.org> --- mm/huge_memory.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 86f9f8b82f8e..93de199ba0f1 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1960,10 +1960,9 @@ int khugepaged_enter_vma_merge(struct vm_area_struct *vma, * page fault if needed. */ return 0; - if (vma->vm_ops) + if (vma->vm_ops || (vm_flags & VM_NO_THP)) /* khugepaged not yet working on file or special mappings */ return 0; - VM_BUG_ON_VMA(vm_flags & VM_NO_THP, vma); hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; hend = vma->vm_end & HPAGE_PMD_MASK; if (hstart < hend) @@ -2352,8 +2351,7 @@ static bool hugepage_vma_check(struct vm_area_struct *vma) return false; if (is_vma_temporary_stack(vma)) return false; - VM_BUG_ON_VMA(vma->vm_flags & VM_NO_THP, vma); - return true; + return !(vma->vm_flags & VM_NO_THP); } static void collapse_huge_page(struct mm_struct *mm,
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