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Subject: Re: [PATCH 2/2] mm: set PG_dma_pinned on get_user_pages*()
References: <20180617012510.20139-1-jhubbard@nvidia.com>
 <20180617012510.20139-3-jhubbard@nvidia.com>
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 <311eba48-60f1-b6cc-d001-5cc3ed4d76a9@nvidia.com>
 <20180618081258.GB16991@lst.de>
From: John Hubbard <jhubbard@nvidia.com>
Message-ID: <d4817192-6db0-2f3f-7c67-6078b69686d3@nvidia.com>
Date: Mon, 18 Jun 2018 10:50:57 -0700
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To: Christoph Hellwig <hch@lst.de>
Cc: Dan Williams <dan.j.williams@intel.com>, Jason Gunthorpe <jgg@ziepe.ca>, john.hubbard@gmail.com, Matthew Wilcox <willy@infradead.org>, Michal Hocko <mhocko@kernel.org>, Christopher Lameter <cl@linux.com>, Jan Kara <jack@suse.cz>, Linux MM <linux-mm@kvack.org>, LKML <linux-kernel@vger.kernel.org>, linux-rdma <linux-rdma@vger.kernel.org>

On 06/18/2018 01:12 AM, Christoph Hellwig wrote:
> On Sun, Jun 17, 2018 at 01:28:18PM -0700, John Hubbard wrote:
>> Yes. However, my thinking was: get_user_pages() can become a way to indicate that 
>> these pages are going to be treated specially. In particular, the caller
>> does not really want or need to support certain file operations, while the
>> page is flagged this way.
>>
>> If necessary, we could add a new API call.
> 
> That API call is called get_user_pages_longterm.

OK...I had the impression that this was just semi-temporary API for dax, but
given that it's an exported symbol, I guess it really is here to stay.

Anyway, are you thinking that we could set the new page flag here? Or just pointing
out that the other get_user_pages* variants are the wrong place?