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Re: [resend PATCH v2 11/33] dm: add dax_device and dax_operations support

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  Re: [resend PATCH v2 11/33] dm: add dax_device and dax_operations  support Bart Van Assche <Bart.VanAssche@wdc.com> - 2017-07-28 18:20 +0200
    Re: [resend PATCH v2 11/33] dm: add dax_device and dax_operations  support Mike Snitzer <snitzer@redhat.com> - 2017-07-28 19:50 +0200
    Re: [resend PATCH v2 11/33] dm: add dax_device and dax_operations support Dan Williams <dan.j.williams@intel.com> - 2017-07-29 22:00 +0200
      Re: [resend PATCH v2 11/33] dm: add dax_device and dax_operations  support Bart Van Assche <Bart.VanAssche@wdc.com> - 2017-07-29 23:30 +0200

#1698925 — Re: [resend PATCH v2 11/33] dm: add dax_device and dax_operations support

On Mon, 2017-04-17 at 12:09 -0700, Dan Williams wrote:
> diff --git a/drivers/md/Kconfig b/drivers/md/Kconfig
> index b7767da50c26..1de8372d9459 100644
> --- a/drivers/md/Kconfig
> +++ b/drivers/md/Kconfig
> @@ -200,6 +200,7 @@ config BLK_DEV_DM_BUILTIN
>  config BLK_DEV_DM
>  	tristate "Device mapper support"
>  	select BLK_DEV_DM_BUILTIN
> +	select DAX
>  	---help---
>  	  Device-mapper is a low level volume manager.  It works by allowing
>  	  people to specify mappings for ranges of logical sectors.  Various

(replying to an e-mail of three months ago)

Hello Dan,

While building a v4.12 kernel I noticed that enabling device mapper support
now unconditionally enables DAX. I think there are plenty of systems that use
dm but do not need DAX. Have you considered to rework this such that instead
of dm selecting DAX that DAX support is only enabled in dm if CONFIG_DAX is
enabled?

Thanks,

Bart.

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#1698982

On Fri, Jul 28 2017 at 12:17pm -0400,
Bart Van Assche <Bart.VanAssche@wdc.com> wrote:

> On Mon, 2017-04-17 at 12:09 -0700, Dan Williams wrote:
> > diff --git a/drivers/md/Kconfig b/drivers/md/Kconfig
> > index b7767da50c26..1de8372d9459 100644
> > --- a/drivers/md/Kconfig
> > +++ b/drivers/md/Kconfig
> > @@ -200,6 +200,7 @@ config BLK_DEV_DM_BUILTIN
> >  config BLK_DEV_DM
> >  	tristate "Device mapper support"
> >  	select BLK_DEV_DM_BUILTIN
> > +	select DAX
> >  	---help---
> >  	  Device-mapper is a low level volume manager.  It works by allowing
> >  	  people to specify mappings for ranges of logical sectors.  Various
> 
> (replying to an e-mail of three months ago)
> 
> Hello Dan,
> 
> While building a v4.12 kernel I noticed that enabling device mapper support
> now unconditionally enables DAX. I think there are plenty of systems that use
> dm but do not need DAX. Have you considered to rework this such that instead
> of dm selecting DAX that DAX support is only enabled in dm if CONFIG_DAX is
> enabled?

I haven't but patches to do so would be welcomed.

Mike

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#1699360 — Re: [resend PATCH v2 11/33] dm: add dax_device and dax_operations support

On Fri, Jul 28, 2017 at 9:17 AM, Bart Van Assche <Bart.VanAssche@wdc.com> wrote:
> On Mon, 2017-04-17 at 12:09 -0700, Dan Williams wrote:
>> diff --git a/drivers/md/Kconfig b/drivers/md/Kconfig
>> index b7767da50c26..1de8372d9459 100644
>> --- a/drivers/md/Kconfig
>> +++ b/drivers/md/Kconfig
>> @@ -200,6 +200,7 @@ config BLK_DEV_DM_BUILTIN
>>  config BLK_DEV_DM
>>       tristate "Device mapper support"
>>       select BLK_DEV_DM_BUILTIN
>> +     select DAX
>>       ---help---
>>         Device-mapper is a low level volume manager.  It works by allowing
>>         people to specify mappings for ranges of logical sectors.  Various
>
> (replying to an e-mail of three months ago)
>
> Hello Dan,
>
> While building a v4.12 kernel I noticed that enabling device mapper support
> now unconditionally enables DAX. I think there are plenty of systems that use
> dm but do not need DAX. Have you considered to rework this such that instead
> of dm selecting DAX that DAX support is only enabled in dm if CONFIG_DAX is
> enabled?
>

I'd rather flip this around and add a CONFIG_DM_DAX that gates whether
DM enables / links to the DAX core. I'll take a look at a patch.

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#1699378

On Sat, 2017-07-29 at 12:57 -0700, Dan Williams wrote:
> On Fri, Jul 28, 2017 at 9:17 AM, Bart Van Assche <Bart.VanAssche@wdc.com> wrote:
> > On Mon, 2017-04-17 at 12:09 -0700, Dan Williams wrote:
> > > diff --git a/drivers/md/Kconfig b/drivers/md/Kconfig
> > > index b7767da50c26..1de8372d9459 100644
> > > --- a/drivers/md/Kconfig
> > > +++ b/drivers/md/Kconfig
> > > @@ -200,6 +200,7 @@ config BLK_DEV_DM_BUILTIN
> > >  config BLK_DEV_DM
> > >       tristate "Device mapper support"
> > >       select BLK_DEV_DM_BUILTIN
> > > +     select DAX
> > >       ---help---
> > >         Device-mapper is a low level volume manager.  It works by allowing
> > >         people to specify mappings for ranges of logical sectors.  Various
> > 
> > (replying to an e-mail of three months ago)
> > 
> > Hello Dan,
> > 
> > While building a v4.12 kernel I noticed that enabling device mapper support
> > now unconditionally enables DAX. I think there are plenty of systems that use
> > dm but do not need DAX. Have you considered to rework this such that instead
> > of dm selecting DAX that DAX support is only enabled in dm if CONFIG_DAX is
> > enabled?
> 
> I'd rather flip this around and add a CONFIG_DM_DAX that gates whether
> DM enables / links to the DAX core. I'll take a look at a patch.

Thanks! Please also consider to move all DAX-related dm code into a separate
source file such that the number of #ifdef CONFIG_DM_DAX statements can be
kept to an absolute minimum.

Bart.

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