linux-kernel - Re: [PATCH 02/15] mm, dax: introduce pfn_t

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Message-ID: <87ines6qib.fsf@concordia.ellerman.id.au>
Date:   Fri, 03 Nov 2017 13:32:44 +1100
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Dan Williams <dan.j.williams@...el.com>, linux-nvdimm@...ts.01.org
Cc:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        linux-kernel@...r.kernel.org, linux-xfs@...r.kernel.org,
        linux-mm@...ck.org, Paul Mackerras <paulus@...ba.org>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        linux-fsdevel@...r.kernel.org, akpm@...ux-foundation.org,
        hch@....de, Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH 02/15] mm, dax: introduce pfn_t_special()

Dan Williams <dan.j.williams@...el.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