Hi,
On 2013/12/13 10:32, Naoya Horiguchi wrote:
> 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-horigu...@ah.jp.nec.com>
>> Cc: sta...@vger.kernel.org
>> Signed-off-by: Jianguo Wu <wujian...@huawei.com>
>> ---
>> 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?
>
Oh, yes, we should only poison the error raw page. I will resend a new version.
Thanks,
Jianguo Wu
> Thanks,
> Naoya
>
>> + }
>> +
>> + atomic_long_add(nr_pages, &num_poisoned_pages);
>> }
>> return ret;
>> }
>> --
>> 1.8.2.2
>>
>>
>> --
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>
> .
>
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