[PATCH v3 5/6] mm/hugetlb: add migration entry check in __unmap_hugepage_range

[Naoya Horiguchi]

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 calls pte_to_swp_entry() and
migration_entry_to_page() to get the right page for migration entries.

Signed-off-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>  # [2.6.36+]
---
 mm/hugetlb.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git mmotm-2014-08-25-16-52.orig/mm/hugetlb.c mmotm-2014-08-25-16-52/mm/hugetlb.c
index 1ed9df6def54..0a4511115ee0 100644
--- mmotm-2014-08-25-16-52.orig/mm/hugetlb.c
+++ mmotm-2014-08-25-16-52/mm/hugetlb.c
@@ -2652,6 +2652,13 @@ void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct *vma,
 		if (huge_pte_none(pte))
 			goto unlock;
 
+		if (unlikely(is_hugetlb_entry_migration(pte))) {
+			swp_entry_t entry = pte_to_swp_entry(pte);
+
+			page = migration_entry_to_page(entry);
+			goto clear;
+		}
+
 		/*
 		 * HWPoisoned hugepage is already unmapped and dropped reference
 		 */
@@ -2677,7 +2684,7 @@ void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct *vma,
 			 */
 			set_vma_resv_flags(vma, HPAGE_RESV_UNMAPPED);
 		}
-
+clear:
 		pte = huge_ptep_get_and_clear(mm, address, ptep);
 		tlb_remove_tlb_entry(tlb, ptep, address);
 		if (huge_pte_dirty(pte))
-- 
1.9.3

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