Re: [PATCH] mm/gup: check page posion status for coredump.

David Hildenbrand
2021-03-18T08:15:40Z

On 18.03.21 05:46, Matthew Wilcox wrote:
> On Wed, Mar 17, 2021 at 10:12:02AM +0100, David Hildenbrand wrote:
>>> + if (IS_ENABLED(CONFIG_MEMORY_FAILURE) && ret == 1) {
>>> + if (unlikely(PageHuge(page) && PageHWPoison(compound_head(page))))
>>> + ret = 0;
>>> + else if (unlikely(PageHWPoison(page)))
>>> + ret = 0;
>>> + }
>>
>> I wonder if a simple
>>
>> if (PageHWPoison(compound_head(page)))
>> ret = 0;
>>
>> won't suffice. But I guess the "issue" is compound pages that are not huge
>> pages or transparent huge pages.
>
> THPs don't set the HWPoison bit on the head page.
>
> https://lore.kernel.org/linux-mm/20210316140947.GA3420@casper.infradead.org/

Oh, okay -- I was missing that we actually already set the HWPoison bit
before trying to split via TestSetPageHWPoison(). I thought for a second
that if splitting fails, we don't set any HWPoison bit.

--
Thanks,

David / dhildenb