linux-kernel - Re: [PATCH 1/2] dax: hide block device code in #ifdef

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Date:   Tue, 16 May 2017 13:16:16 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     "Darrick J. Wong" <darrick.wong@...cle.com>
Cc:     Dan Williams <dan.j.williams@...el.com>, Jan Kara <jack@...e.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        linux-xfs@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] dax: hide block device code in #ifdef

On Mon, May 15, 2017 at 5:50 PM, Darrick J. Wong
<darrick.wong@...cle.com> wrote:
> On Mon, May 15, 2017 at 04:20:09PM +0200, Arnd Bergmann wrote:
>> On Mon, May 15, 2017 at 4:11 PM, Dan Williams <dan.j.williams@...el.com> wrote:
>> > On Mon, May 15, 2017 at 6:44 AM, Arnd Bergmann <arnd@...db.de> wrote:
>> >> We allow configurations with CONFIG_BLOCK=n and CONFIG_DAX=y, which now
>> >> results in a link error:
>> >>
>> >> drivers/dax/super.c: In function 'bdev_dax_pgoff':
>> >> drivers/dax/super.c:50:26: error: implicit declaration of function 'get_start_sect'; did you mean 'get_task_cred'? [-Werror=implicit-function-declaration]
>> >>
>> >> The two obvious ways to avoid the link error are to either add an #ifdef
>> >> around the code that was moved from fs/block_dev.c, or to disallow the
>> >> configuration. I could not see if there is or is not a reason to support
>> >> this combination of options, but in case there is, the #ifdef is the
>> >> safer choice.
>> >>
>> >> Fixes: ef51042472f5 ("block, dax: move "select DAX" from BLOCK to FS_DAX")
>> >> Signed-off-by: Arnd Bergmann <arnd@...db.de>
>> >
>> > Yup, the same one I came up with:
>> >
>> > https://patchwork.kernel.org/patch/9725513/
>> >
>> > If you have a a pull request coming up soon you can add my Acked-by to
>> > both of these patches, otherwise I'll send what I have along at the
>> > end of the week.
>>
>> I didn't plan to send a pull request, please use whatever you have.
>
> I don't mind pulling the (second) patch in via the xfs tree.
>
> Reviewed-by: Darrick J. Wong <darrick.wong@...cle.com>
>

I think Dan's "dax, xfs, ext4: compile out iomap-dax paths in the
FS_DAX=n case" handles this in a nicer way, so my patch 2/2 is not
needed any more.

      Arnd