mm/memory-failure.c: recheck PageHuge() after hugetlb page migrate successfully

commit a49ecbcd7b0d5a1cda7d60e03df402dd0ef76ac8 upstream.

After a successful hugetlb page migration by soft offline, the source
page will either be freed into hugepage_freelists or buddy(over-commit
page).  If page is in buddy, page_hstate(page) will be NULL.  It will
hit a NULL pointer dereference in dequeue_hwpoisoned_huge_page().

  BUG: unable to handle kernel NULL pointer dereference at 0000000000000058
  IP: [<ffffffff81163761>] dequeue_hwpoisoned_huge_page+0x131/0x1d0
  PGD c23762067 PUD c24be2067 PMD 0
  Oops: 0000 [#1] SMP

So check PageHuge(page) after call migrate_pages() successfully.

Signed-off-by: Jianguo Wu <wujianguo@huawei.com>
Tested-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Reviewed-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
[wujg: backport to 3.4:
 - adjust context
 - s/num_poisoned_pages/mce_bad_pages/]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 1b038789a9d6d159c10cc0957ccf17d0c1a19249..96c4bcf188b1e7a7290beac0e90c9965f874df23 100644 (file)
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1441,10 +1441,18 @@ static int soft_offline_huge_page(struct page *page, int flags)
                return ret;
        }
 done:
-       if (!PageHWPoison(hpage))
-               atomic_long_add(1 << compound_trans_order(hpage), &mce_bad_pages);
-       set_page_hwpoison_huge_page(hpage);
-       dequeue_hwpoisoned_huge_page(hpage);
+       /* overcommit hugetlb page will be freed to buddy */
+       if (PageHuge(hpage)) {
+               if (!PageHWPoison(hpage))
+                       atomic_long_add(1 << compound_trans_order(hpage),
+                                       &mce_bad_pages);
+               set_page_hwpoison_huge_page(hpage);
+               dequeue_hwpoisoned_huge_page(hpage);
+       } else {
+               SetPageHWPoison(page);
+               atomic_long_inc(&mce_bad_pages);
+       }
+
        /* keep elevated page count for bad page */
        return ret;
 }