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From: Michael Ellerman <mpe@ellerman.id.au>
Subject: Re: [PATCH 02/15] mm, dax: introduce pfn_t_special()
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Date: Fri, 03 Nov 2017 13:32:44 +1100
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To: Dan Williams <dan.j.williams@intel.com>, linux-nvdimm@lists.01.org
Cc: Arnd Bergmann <arnd@arndb.de>, Benjamin Herrenschmidt <benh@kernel.crashing.org>, Heiko Carstens <heiko.carstens@de.ibm.com>, linux-kernel@vger.kernel.org, linux-xfs@vger.kernel.org, linux-mm@kvack.org, Paul Mackerras <paulus@samba.org>, Martin Schwidefsky <schwidefsky@de.ibm.com>, linux-fsdevel@vger.kernel.org, akpm@linux-foundation.org, hch@lst.de
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Dan Williams <dan.j.williams@intel.com> writes:

> In support of removing the VM_MIXEDMAP indication from DAX VMAs,
> introduce pfn_t_special() for drivers to indicate that _PAGE_SPECIAL
> should be used for DAX ptes. This also helps identify drivers like
> dccssblk that only want to use DAX in a read-only fashion without
> get_user_pages() support.
>
> Ideally we could delete axonram and dcssblk DAX support, but if we need
> to keep it better make it explicit that axonram and dcssblk only support
> a sub-set of DAX due to missing _PAGE_DEVMAP support.

I sent a patch to remove axonram (sorry meant to Cc you):

  http://patchwork.ozlabs.org/patch/833588/

Will see if there's any feedback.

cheers
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