Commit a49ecbcd authored Dec 18, 2013 by Jianguo Wu Committed by Linus Torvalds Dec 18, 2013

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



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>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 6815bf3f

mm/memory-failure.c

+10 −4

Original line number	Diff line number	Diff line
		@@ -1505,10 +1505,16 @@ static int soft_offline_huge_page(struct page *page, int flags)
		if (ret > 0)
		ret = -EIO;
		} else {
		/* overcommit hugetlb page will be freed to buddy */
		if (PageHuge(page)) {
		set_page_hwpoison_huge_page(hpage);
		dequeue_hwpoisoned_huge_page(hpage);
		atomic_long_add(1 << compound_order(hpage),
		&num_poisoned_pages);
		} else {
		SetPageHWPoison(page);
		atomic_long_inc(&num_poisoned_pages);
		}
		}
		return ret;
		}

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