linux-kernel - Re: [RFC PATCH 2/2] mm/gup: introduce vaddr_pin_pages

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Message-ID: <a584cfbd-b458-dce9-4144-3b542bcf163d@nvidia.com>
Date:   Fri, 16 Aug 2019 11:50:09 -0700
From:   John Hubbard <jhubbard@...dia.com>
To:     Ira Weiny <ira.weiny@...el.com>, Jan Kara <jack@...e.cz>
CC:     Andrew Morton <akpm@...ux-foundation.org>,
        Christoph Hellwig <hch@...radead.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Dave Chinner <david@...morbit.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Jérôme Glisse <jglisse@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>,
        <linux-fsdevel@...r.kernel.org>, <linux-rdma@...r.kernel.org>
Subject: Re: [RFC PATCH 2/2] mm/gup: introduce vaddr_pin_pages_remote()

On 8/16/19 11:33 AM, Ira Weiny wrote:
> On Fri, Aug 16, 2019 at 05:41:08PM +0200, Jan Kara wrote:
>> On Thu 15-08-19 19:14:08, John Hubbard wrote:
>>> On 8/15/19 10:41 AM, John Hubbard wrote:
>>>> On 8/15/19 10:32 AM, Ira Weiny wrote:
>>>>> On Thu, Aug 15, 2019 at 03:35:10PM +0200, Jan Kara wrote:
>>>>>> On Thu 15-08-19 15:26:22, Jan Kara wrote:
>>>>>>> On Wed 14-08-19 20:01:07, John Hubbard wrote:
>>>>>>>> On 8/14/19 5:02 PM, John Hubbard wrote:
>>> ...
>>>
>>> OK, there was only process_vm_access.c, plus (sort of) Bharath's sgi-gru
>>> patch, maybe eventually [1].  But looking at process_vm_access.c, I think
>>> it is one of the patches that is no longer applicable, and I can just
>>> drop it entirely...I'd welcome a second opinion on that...
>>
>> I don't think you can drop the patch. process_vm_rw_pages() clearly touches
>> page contents and does not synchronize with page_mkclean(). So it is case
>> 1) and needs FOLL_PIN semantics.
> 
> John could you send a formal patch using vaddr_pin* and I'll add it to the
> tree?
> 

Yes...hints about which struct file to use here are very welcome, btw. This part
of mm is fairly new to me.

thanks,
-- 
John Hubbard
NVIDIA