[PATCHv9-rebased2 05/37] khugepaged: recheck pmd after mmap_sem re-acquired
From: Kirill A. Shutemov <hidden>
Date: 2016-06-15 20:06:10
Also in:
linux-fsdevel, lkml
Subsystem:
memory management, memory management - thp (transparent huge page), the rest · Maintainers:
Andrew Morton, David Hildenbrand, Lorenzo Stoakes, Linus Torvalds
Vlastimil noted[1] that pmd can be no longer valid after we drop mmap_sem.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-69141c5f357f@suse.cz Signed-off-by: Kirill A. Shutemov <redacted> --- 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
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