Vlastimil noted[1] that pmd can be no longer valid after we drop mmap_sem. We need recheck it once mmap_sem taken again.
[1] http://lkml.kernel.org/r/12918dcd-a695-c6f4-e06f-69141c5f3...@suse.cz Signed-off-by: Kirill A. Shutemov <kirill.shute...@linux.intel.com> --- mm/huge_memory.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index d7ccc8558187..0efdad975659 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2437,6 +2437,9 @@ static bool __collapse_huge_page_swapin(struct mm_struct *mm, /* vma is no longer available, don't continue to swapin */ if (hugepage_vma_revalidate(mm, address)) return false; + /* check if the pmd is still valid */ + if (mm_find_pmd(mm, address) != pmd) + return false; } if (ret & VM_FAULT_ERROR) { trace_mm_collapse_huge_page_swapin(mm, swapped_in, 0); @@ -2522,6 +2525,9 @@ static void collapse_huge_page(struct mm_struct *mm, result = hugepage_vma_revalidate(mm, address); if (result) goto out; + /* check if the pmd is still valid */ + if (mm_find_pmd(mm, address) != pmd) + goto out; anon_vma_lock_write(vma->anon_vma); -- 2.8.1
