From mboxrd@z Thu Jan  1 00:00:00 1970
From: John Hubbard <jhubbard@nvidia.com>
Subject: Re: [LSF/MM TOPIC] Discuss least bad options for resolving
 longterm-GUP usage by RDMA
Date: Tue, 12 Feb 2019 18:58:10 -0800
Message-ID: <b8794103-5ae1-ff8d-22be-d585d36e6310@nvidia.com>
References: <bfe0fdd5400d41d223d8d30142f56a9c8efc033d.camel@redhat.com>
 <01000168c8e2de6b-9ab820ed-38ad-469c-b210-60fcff8ea81c-000000@email.amazonses.com>
 <20190208044302.GA20493@dastard> <20190208111028.GD6353@quack2.suse.cz>
 <CAPcyv4iVtBfO8zWZU3LZXLqv-dha1NSG+2+7MvgNy9TibCy4Cw@mail.gmail.com>
 <20190211102402.GF19029@quack2.suse.cz>
 <CAPcyv4iHso+PqAm-4NfF0svoK4mELJMSWNp+vsG43UaW1S2eew@mail.gmail.com>
 <20190211180654.GB24692@ziepe.ca>
 <20190211181921.GA5526@iweiny-DESK2.sc.intel.com>
 <fb507b56-7f8f-cf2c-285c-bae3b2d72c4f@nvidia.com>
 <20190211221247.GI24692@ziepe.ca>
 <018c1a05-5fd8-886a-573b-42649949bba8@nvidia.com>
 <01000168e29418ba-81301f56-9370-4555-b70c-3ad51be84543-000000@email.amazonses.com>
Mime-Version: 1.0
Content-Type: text/plain; charset="utf-8"
Content-Transfer-Encoding: 7bit
Return-path: <linux-kernel-owner@vger.kernel.org>
In-Reply-To: <01000168e29418ba-81301f56-9370-4555-b70c-3ad51be84543-000000@email.amazonses.com>
Content-Language: en-US-large
Sender: linux-kernel-owner@vger.kernel.org
To: Christopher Lameter <cl@linux.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>, Ira Weiny <ira.weiny@intel.com>, Dan Williams <dan.j.williams@intel.com>, Jan Kara <jack@suse.cz>, Dave Chinner <david@fromorbit.com>, Doug Ledford <dledford@redhat.com>, Matthew Wilcox <willy@infradead.org>, lsf-pc@lists.linux-foundation.org, linux-rdma <linux-rdma@vger.kernel.org>, Linux MM <linux-mm@kvack.org>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, Jerome Glisse <jglisse@redhat.com>, Michal Hocko <mhocko@kernel.org>
List-Id: linux-rdma@vger.kernel.org

On 2/12/19 8:39 AM, Christopher Lameter wrote:
> On Mon, 11 Feb 2019, John Hubbard wrote:
> 
>> But anyway, Jan's proposal a bit earlier today [1] is finally sinking into
>> my head--if we actually go that way, and prevent the caller from setting up
>> a problematic gup pin in the first place, then that may make this point sort
>> of moot.
> 
> Ok well can be document how we think it would work somewhere? Long term
> mapping a page cache page could a problem and we need to explain that
> somewhere.
> 

Yes, once the dust settles, I think Documentation/vm/get_user_pages.rst is the
right place. I started to create that file, but someone observed that my initial
content was entirely backward-looking (described the original problem, instead 
of describing how the new system would work). So I'll use this opportunity for 
a do-over. :)

thanks,
-- 
John Hubbard
NVIDIA