[PATCH v5 6/8] mm/hugetlb: add migration entry check in __unmap_hugepage_range

From: Naoya Horiguchi
Date: Tue Dec 02 2014 - 03:31:33 EST

If __unmap_hugepage_range() tries to unmap the address range over which
hugepage migration is on the way, we get the wrong page because pte_page()
doesn't work for migration entries. This patch simply clears the pte for
migration entries as we do for hwpoison entries.

Fixes: 290408d4a2 ("hugetlb: hugepage migration core")
Signed-off-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> # [2.6.36+]
ChangeLog v4:
- check hwpoisoned hugepage and migrating hugepage with the same check
instead of doing separately
mm/hugetlb.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git mmotm-2014-11-26-15-45.orig/mm/hugetlb.c mmotm-2014-11-26-15-45/mm/hugetlb.c
index 2807be3f260d..a2bfd02e289f 100644
--- mmotm-2014-11-26-15-45.orig/mm/hugetlb.c
+++ mmotm-2014-11-26-15-45/mm/hugetlb.c
@@ -2657,9 +2657,10 @@ void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct *vma,
goto unlock;

- * HWPoisoned hugepage is already unmapped and dropped reference
+ * Migrating hugepage or HWPoisoned hugepage is already
+ * unmapped and its refcount is dropped, so just clear pte here.
- if (unlikely(is_hugetlb_entry_hwpoisoned(pte))) {
+ if (unlikely(!pte_present(pte))) {
huge_pte_clear(mm, address, ptep);
goto unlock;
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