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Date: Fri, 02 Oct 2015 16:42:28 -0600
From: Logan Gunthorpe <logang@deltatee.com>
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Subject: Re: [PATCH 14/15] mm, dax, pmem: introduce {get|put}_dev_pagemap()
 for dax-gup
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To: Dan Williams <dan.j.williams@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>, Dave Hansen <dave@sr71.net>, "linux-nvdimm@lists.01.org" <linux-nvdimm@lists.01.org>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, Linux MM <linux-mm@kvack.org>, Alexander Viro <viro@zeniv.linux.org.uk>, linux-fsdevel <linux-fsdevel@vger.kernel.org>, Matthew Wilcox <willy@linux.intel.com>, Ross Zwisler <ross.zwisler@linux.intel.com>, Stephen Bates <Stephen.Bates@pmcs.com>



On 02/10/15 03:53 PM, Dan Williams wrote:
> Yes, this location for dev_pagemap will not work.  I've since moved it
> to a union with the lru list_head since ZONE_DEVICE pages memory
> should always have an elevated page count and never land on a slab
> allocator lru.

Oh, also, I was actually hoping to make use of the lru list_head in the 
future with ZONE_DEVICE memory. One thought I had was once we have a 
PCIe device with a BAR space, we'd then need to have a way of allocating 
these buffers when user space needs them. The simple way I was thinking 
was to just use the lru list head to store lists of used and unused 
pages -- though there are probably other solutions to this that don't 
require using struct pages.

Thanks,

Logan

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