3.2.81-rc1 review patch. If anyone has any objections, please let me know.
------------------ From: Konstantin Khlebnikov <[email protected]> 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+stkftqan9ydtge...@mail.gmail.com Fixes: 78f11a255749 ("mm: thp: fix /dev/zero MAP_PRIVATE and vm_flags cleanups") Signed-off-by: Konstantin Khlebnikov <[email protected]> Reported-by: Dmitry Vyukov <[email protected]> Acked-by: Vlastimil Babka <[email protected]> Acked-by: Kirill A. Shutemov <[email protected]> Cc: Dmitry Vyukov <[email protected]> Cc: Andrea Arcangeli <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]> [bwh: Backported to 3.2: - The assertions use VM_BUG_ON() and also check is_linear_pfn_mapping(); keep that check - Adjust context] Signed-off-by: Ben Hutchings <[email protected]> --- mm/huge_memory.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1635,14 +1635,14 @@ int khugepaged_enter_vma_merge(struct vm * 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; /* * If is_pfn_mapping() is true is_learn_pfn_mapping() must be * true too, verify it here. */ - VM_BUG_ON(is_linear_pfn_mapping(vma) || vm_flags & VM_NO_THP); + VM_BUG_ON(is_linear_pfn_mapping(vma)); hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; hend = vma->vm_end & HPAGE_PMD_MASK; if (hstart < hend) @@ -1831,8 +1831,8 @@ static bool hugepage_vma_check(struct vm * If is_pfn_mapping() is true is_learn_pfn_mapping() must be * true too, verify it here. */ - VM_BUG_ON(is_linear_pfn_mapping(vma) || vma->vm_flags & VM_NO_THP); - return true; + VM_BUG_ON(is_linear_pfn_mapping(vma)); + return !(vma->vm_flags & VM_NO_THP); } static void collapse_huge_page(struct mm_struct *mm,
