Re: [PATCH v2 2/4] mm: fail get_vaddr_frames() for filesystem-dax mappings

[Dan Williams]

On Mon, Nov 27, 2017 at 8:15 AM, Jan Kara <jack@xxxxxxx> wrote:
> On Tue 14-11-17 11:56:39, Dan Williams wrote:
>> Until there is a solution to the dma-to-dax vs truncate problem it is
>> not safe to allow V4L2, Exynos, and other frame vector users to create
>> long standing / irrevocable memory registrations against filesytem-dax
>> vmas.
>>
>> Cc: Inki Dae <inki.dae@xxxxxxxxxxx>
>> Cc: Seung-Woo Kim <sw0312.kim@xxxxxxxxxxx>
>> Cc: Joonyoung Shim <jy0922.shim@xxxxxxxxxxx>
>> Cc: Kyungmin Park <kyungmin.park@xxxxxxxxxxx>
>> Cc: Mauro Carvalho Chehab <mchehab@xxxxxxxxxx>
>> Cc: linux-media@xxxxxxxxxxxxxxx
>> Cc: Jan Kara <jack@xxxxxxx>
>> Cc: Mel Gorman <mgorman@xxxxxxx>
>> Cc: Vlastimil Babka <vbabka@xxxxxxx>
>> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
>> Cc: <stable@xxxxxxxxxxxxxxx>
>> Fixes: 3565fce3a659 ("mm, x86: get_user_pages() for dax mappings")
>> Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
>
> Makes sense. I'd just note that in principle get_vaddr_frames() is no more
> long-term than get_user_pages(). It is just so that all the users of
> get_vaddr_frames() currently want a long-term reference. Maybe could you
> add here also a comment that the vma_is_fsdax() check is there because all
> users of this function want a long term page reference? With that you can
> add:

Ok, will do.

> Reviewed-by: Jan Kara <jack@xxxxxxx>

Thanks.