On Fri, Dec 13, 2013 at 11:36:36AM +0800, Jianguo Wu wrote:
> Changelog:
> - Only set PageHWPoison on the error raw page if page is freed into buddy
>
> 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().
>
> [ 890.677918] BUG: unable to handle kernel NULL pointer dereference at
> 0000000000000058
> [ 890.685741] IP: [<ffffffff81163761>]
> dequeue_hwpoisoned_huge_page+0x131/0x1d0
> [ 890.692861] PGD c23762067 PUD c24be2067 PMD 0
> [ 890.697314] Oops: 0000 [#1] SMP
>
> So check PageHuge(page) after call migrate_pages() successfully.
>
> Tested-by: Naoya Horiguchi <n-horigu...@ah.jp.nec.com>
> Cc: sta...@vger.kernel.org
> Signed-off-by: Jianguo Wu <wujian...@huawei.com>
Thanks!
Reviewed-by: Naoya Horiguchi <n-horigu...@ah.jp.nec.com>
> ---
> mm/memory-failure.c | 14 ++++++++++----
> 1 files changed, 10 insertions(+), 4 deletions(-)
>
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index b7c1716..db08af9 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -1505,10 +1505,16 @@ static int soft_offline_huge_page(struct page *page,
> int flags)
> if (ret > 0)
> ret = -EIO;
> } else {
> - set_page_hwpoison_huge_page(hpage);
> - dequeue_hwpoisoned_huge_page(hpage);
> - atomic_long_add(1 << compound_order(hpage),
> - &num_poisoned_pages);
> + /* 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;
> }
> --
> 1.7.1
>
>
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