Re: [PATCH v1 01/11] memory-failure: fetch compound_head after pgmap_pfn_valid()

Joao Martins
2021-04-24T19:01:31Z

On 4/24/21 1:12 AM, Dan Williams wrote:
> On Thu, Mar 25, 2021 at 4:10 PM Joao Martins <joao.m.martins@oracle.com> wrote:
>>
>> memory_failure_dev_pagemap() at the moment assumes base pages (e.g.
>> dax_lock_page()). For pagemap with compound pages fetch the
>> compound_head in case we are handling a tail page memory failure.
>>
>> Currently this is a nop, but in the advent of compound pages in
>> dev_pagemap it allows memory_failure_dev_pagemap() to keep working.
>>
>> Reported-by: Jane Chu <jane.chu@oracle.com>
>> Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
>> ---
>> mm/memory-failure.c | 2 ++
>> 1 file changed, 2 insertions(+)
>>
>> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
>> index 24210c9bd843..94240d772623 100644
>> --- a/mm/memory-failure.c
>> +++ b/mm/memory-failure.c
>> @@ -1318,6 +1318,8 @@ static int memory_failure_dev_pagemap(unsigned long pfn, int flags,
>> goto out;
>> }
>>
>> + page = compound_head(page);
>
> Unless / until we do compound pages for the filesystem-dax case, I
> would add a comment like:
>
> /* pages instantiated by device-dax (not filesystem-dax) may be
> compound pages */
>
I've fixed up with the comment.

Thanks!