Re: [PATCH 0/6] Support DAX for device-mapper dm-linear devices

[Dan Williams]

Thanks Toshi!

On Mon, Jun 13, 2016 at 3:21 PM, Toshi Kani <toshi.kani@xxxxxxx> wrote:
> This patch-set adds DAX support to device-mapper dm-linear devices
> used by LVM.  It works with LVM commands as follows:
>  - Creation of a logical volume with all DAX capable devices (such
>    as pmem) sets the logical volume DAX capable as well.
>  - Once a logical volume is set to DAX capable, the volume may not
>    be extended with non-DAX capable devices.

I don't mind this, but it seems a policy decision that the kernel does
not need to make.  A sufficiently sophisticated user could cope with
DAX being available at varying LBAs.  Would it be sufficient to move
this policy decision to userspace tooling?

> The direct_access interface is added to dm and dm-linear to map
> a request to a target device.

I had dm-linear and md-raid0 support on my list of things to look at,
did you have raid0 in your plans?