On 6/17/21 5:21 AM, David Hildenbrand wrote:
> On 17.06.21 11:26, Naoya Horiguchi wrote:
>> From: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
>>
>> Recent changes by patch "mm/page_alloc: allow high-order pages to be
>> stored on the per-cpu lists" makes kernels determine whether to use pcp
>> by pcp_allowed_order(), which breaks soft-offline for hugetlb pages.
>>
>> Soft-offline dissolves a migration source page, then removes it from
>> buddy free list, so it's assumed that any subpage of the soft-offlined
>> hugepage are recognized as a buddy page just after returning from
>> dissolve_free_huge_page(). pcp_allowed_order() returns true for
>> hugetlb, so this assumption is no longer true.
>>
>> So disable pcp during dissolve_free_huge_page() and
>> take_page_off_buddy() to prevent soft-offlined hugepages from linking to
>> pcp lists. Soft-offline should not be common events so the impact on
>> performance should be minimal. And I think that the optimization of
>> Mel's patch could benefit to hugetlb so zone_pcp_disable() is called
>> only in hwpoison context.
>>
>> Signed-off-by: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
>> ---
>> mm/memory-failure.c | 19 ++++++++++++++++---
>> 1 file changed, 16 insertions(+), 3 deletions(-)
>>
>> diff --git v5.13-rc6-mmotm-2021-06-15-20-24/mm/memory-failure.c v5.13-rc6-mmotm-2021-06-15-20-24_patched/mm/memory-failure.c
>> index 1842822a10da..593079766655 100644
>> --- v5.13-rc6-mmotm-2021-06-15-20-24/mm/memory-failure.c
>> +++ v5.13-rc6-mmotm-2021-06-15-20-24_patched/mm/memory-failure.c
>> @@ -66,6 +66,19 @@ int sysctl_memory_failure_recovery __read_mostly = 1;
>> atomic_long_t num_poisoned_pages __read_mostly = ATOMIC_LONG_INIT(0);
>> +static bool __page_handle_poison(struct page *page)
>> +{
>> + bool ret;
>> +
>> + zone_pcp_disable(page_zone(page));
>> + ret = dissolve_free_huge_page(page);
>> + if (!ret)
>> + ret = take_page_off_buddy(page);
>> + zone_pcp_enable(page_zone(page));
>> +
>> + return ret;
>> +}
>> +
>> static bool page_handle_poison(struct page *page, bool hugepage_or_freepage, bool release)
>> {
>> if (hugepage_or_freepage) {
>> @@ -73,7 +86,7 @@ static bool page_handle_poison(struct page *page, bool hugepage_or_freepage, boo
>> * Doing this check for free pages is also fine since dissolve_free_huge_page
>> * returns 0 for non-hugetlb pages as well.
>> */
>> - if (dissolve_free_huge_page(page) || !take_page_off_buddy(page))
>> + if (!__page_handle_poison(page))
>> /*
>> * We could fail to take off the target page from buddy
>> * for example due to racy page allocation, but that's
>> @@ -986,7 +999,7 @@ static int me_huge_page(struct page *p, unsigned long pfn)
>> */
>> if (PageAnon(hpage))
>> put_page(hpage);
>> - if (!dissolve_free_huge_page(p) && take_page_off_buddy(p)) {
>> + if (__page_handle_poison(p)) {
>> page_ref_inc(p);
>> res = MF_RECOVERED;
>> }
>> @@ -1441,7 +1454,7 @@ static int memory_failure_hugetlb(unsigned long pfn, int flags)
>> res = get_hwpoison_page(p, flags);
>> if (!res) {
>> res = MF_FAILED;
>> - if (!dissolve_free_huge_page(p) && take_page_off_buddy(p)) {
>> + if (__page_handle_poison(p)) {
>> page_ref_inc(p);
>> res = MF_RECOVERED;
>> }
>>
>
> Just to make sure: all call paths are fine that we are taking a mutex, right?
>
That should be the case. dissolve_free_huge_page can sleep, so if not
we are already broken.
--
Mike Kravetz
