Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory

[Dan Williams]

On Wed, Apr 19, 2017 at 11:41 AM, Logan Gunthorpe <logang@xxxxxxxxxxxx> wrote:
>
>
> On 19/04/17 12:30 PM, Dan Williams wrote:
>> Letting others users do the container_of() arrangement means that
>> struct page_map needs to become public and move into struct
>> dev_pagemap directly.
>
> Ah, yes, I got a bit turned around by that and failed to notice that
> page_map and dev_pagemap are different. Why is it that dev_pagemap
> contains pretty much the exact same information as page_map? The only
> thing gained that I can see is that the struct resource gains const
> protection...
>
>> ...I think that encapsulation loss is worth it for the gain of clearly
>> separating the HMM-case from the base case.
>
> Agreed.
>

Yeah, I forgot that dev_pagemap grew those fields, so we don't have
any real encapsulation today. So this would just be a pure cleanup to
kill struct page_map.