On Fri, Dec 13, 2013 at 09:09:52AM +0800, Jianguo Wu wrote:
> 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-horiguchi@xxxxxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Jianguo Wu <wujianguo@xxxxxxxxxx>
> ---
> mm/memory-failure.c | 19 ++++++++++++++-----
> 1 file changed, 14 insertions(+), 5 deletions(-)
>
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index b7c1716..e5567f2 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -1471,7 +1471,8 @@ static int get_any_page(struct page *page, unsigned long pfn, int flags)
>
> static int soft_offline_huge_page(struct page *page, int flags)
> {
> - int ret;
> + int ret, i;
> + unsigned long nr_pages;
> unsigned long pfn = page_to_pfn(page);
> struct page *hpage = compound_head(page);
> LIST_HEAD(pagelist);
> @@ -1489,6 +1490,8 @@ static int soft_offline_huge_page(struct page *page, int flags)
> }
> unlock_page(hpage);
>
> + nr_pages = 1 << compound_order(hpage);
> +
> /* Keep page count to indicate a given hugepage is isolated. */
> list_move(&hpage->lru, &pagelist);
> ret = migrate_pages(&pagelist, new_page, MPOL_MF_MOVE_ALL,
> @@ -1505,10 +1508,16 @@ 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);
> + } else {
> + for (i = 0; i < nr_pages; i++)
> + SetPageHWPoison(hpage + i);
Why don't you set PageHWPoison only on the error raw page instead
of the whole error hugepage, or is there some problem of doing so?
Thanks,
Naoya
> + }
> +
> + atomic_long_add(nr_pages, &num_poisoned_pages);
> }
> return ret;
> }
> --
> 1.8.2.2
>
>
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