From: Konstantin Khlebnikov Date: Thu, 28 Apr 2016 23:18:32 +0000 (-0700) Subject: mm/huge_memory: replace VM_NO_THP VM_BUG_ON with actual VMA check X-Git-Tag: v3.16.36~57 X-Git-Url: http://git.hungrycats.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=1ec1d7466f9f21b243e0f96c47a3bcace44b993d;p=linux mm/huge_memory: replace VM_NO_THP VM_BUG_ON with actual VMA check commit 3486b85a29c1741db99d0c522211c82d2b7a56d0 upstream. 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. 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") Signed-off-by: Konstantin Khlebnikov Reported-by: Dmitry Vyukov Acked-by: Vlastimil Babka Acked-by: Kirill A. Shutemov Cc: Dmitry Vyukov Cc: Andrea Arcangeli Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds [bwh: Backported to 3.16: deleted assertions used VM_BUG_ON()] Signed-off-by: Ben Hutchings --- diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 479b57cc5195..dc528a51ccbf 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2068,10 +2068,9 @@ 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(vm_flags & VM_NO_THP); hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; hend = vma->vm_end & HPAGE_PMD_MASK; if (hstart < hend) @@ -2376,8 +2375,7 @@ static bool hugepage_vma_check(struct vm_area_struct *vma) return false; if (is_vma_temporary_stack(vma)) return false; - VM_BUG_ON(vma->vm_flags & VM_NO_THP); - return true; + return !(vma->vm_flags & VM_NO_THP); } static void collapse_huge_page(struct mm_struct *mm,