3.16.36-rc1 review patch. If anyone has any objections, please let me know.
------------------ From: Konstantin Khlebnikov <koc...@gmail.com> 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 <koc...@gmail.com> Reported-by: Dmitry Vyukov <dvyu...@google.com> Acked-by: Vlastimil Babka <vba...@suse.cz> Acked-by: Kirill A. Shutemov <kirill.shute...@linux.intel.com> Cc: Dmitry Vyukov <dvyu...@google.com> Cc: Andrea Arcangeli <aarca...@redhat.com> Signed-off-by: Andrew Morton <a...@linux-foundation.org> Signed-off-by: Linus Torvalds <torva...@linux-foundation.org> [bwh: Backported to 3.16: deleted assertions used VM_BUG_ON()] Signed-off-by: Ben Hutchings <b...@decadent.org.uk> --- mm/huge_memory.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2068,10 +2068,9 @@ 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; - 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 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,
