mm/hugetlb: add migration entry check in __unmap_hugepage_range

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@ah.jp.nec.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: James Hogan <james.hogan@imgtec.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Rik van Riel <riel@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
Cc: Nishanth Aravamudan <nacc@linux.vnet.ibm.com>
Cc: Lee Schermerhorn <lee.schermerhorn@hp.com>
Cc: Steve Capper <steve.capper@linaro.org>
Cc: <stable@vger.kernel.org>	[2.6.36+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 3 insertions, 2 deletions

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index c2970e7eb527..fd28d6ba5e5d 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -2657,9 +2657,10 @@ again:
                         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;
                 }