Re: [PATCH v4 5/5] mm: Fix memory_failure() handling of dax-namespace metadata

[HORIGUCHI NAOYA(堀口 直也)]

On Wed, Jan 13, 2021 at 04:43:37PM -0800, Dan Williams wrote:
> Given 'struct dev_pagemap' spans both data pages and metadata pages be
> careful to consult the altmap if present to delineate metadata. In fact
> the pfn_first() helper already identifies the first valid data pfn, so
> export that helper for other code paths via pgmap_pfn_valid().
> 
> Other usage of get_dev_pagemap() are not a concern because those are
> operating on known data pfns having been looked up by get_user_pages().
> I.e. metadata pfns are never user mapped.
> 
> Fixes: 6100e34b2526 ("mm, memory_failure: Teach memory_failure() about dev_pagemap pages")
> Cc: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Reported-by: David Hildenbrand <david@xxxxxxxxxx>
> Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
> Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>

Looks fine to me.

Reviewed-by: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>