On 2022/4/8 9:56, HORIGUCHI NAOYA(堀口 直也) wrote:
> On Thu, Apr 07, 2022 at 09:38:26PM +0800, Miaohe Lin wrote:
>> On 2022/4/7 19:29, Naoya Horiguchi wrote:
> ...
>>> +int __get_huge_page_for_hwpoison(unsigned long pfn, int flags)
>>> +{
>>> + struct page *page = pfn_to_page(pfn);
>>> + struct page *head = compound_head(page);
>>> + int ret = 2; /* fallback to normal page handling */
>>> + bool count_increased = false;
>>> +
>>> + if (!PageHeadHuge(head))
>>> + goto out;
>>> +
>>> + if (flags & MF_COUNT_INCREASED) {
>>> + ret = 1;
>>> + count_increased = true;
>>> + } else if (HPageFreed(head) || HPageMigratable(head)) {
>>> + ret = get_page_unless_zero(head);
>>> + if (ret)
>>> + count_increased = true;
>>> + } else {
>>> + ret = -EBUSY;
>>> + goto out;
>>> + }
>>> +
>>> + if (hwpoison_filter(page)) {
>>> + ret = -EOPNOTSUPP;
>>> + goto out;
>>> + }
>>
>> Now hwpoison_filter is done without lock_page + unlock_page. Is this ok or
>> lock_page + unlock_page pair is indeed required?
>
> Hmm, we had better call hwpoison_filter in page lock for hugepages.
> I'll move this too, thank you.
>
>>> +
>>> + if (TestSetPageHWPoison(head)) {
>>> + ret = -EHWPOISON;
>>> + goto out;
>>> + }
>>
>> Without this patch, page refcnt is not decremented if MF_COUNT_INCREASED is set in flags
>> when PageHWPoison is already set. So I think this patch also fixes that issue. Thanks!
>
> Good point, I even didn't notice that. And the issue still seems to exist
> for normal page's cases. Maybe encountering "already hwpoisoned" case from
> madvise_inject_error() is rare but could happen when the first call failed
> to contain the error (which is still accessible from the calling process).
Oh, I missed normal page's issue. :) Will you fix this issue kindly or am I supposed
to fix it?
Many thanks.
>
...
