Re: [PATCH v4 12/16] libnvdimm, nfit: enable support for volatile ranges

From: hch@xxxxxx
Date: Wed Jul 05 2017 - 22:11:24 EST

On Wed, Jul 05, 2017 at 07:08:54PM -0700, Dan Williams wrote:
> [ adding Jeff, and Johannes ]
> On Wed, Jul 5, 2017 at 6:17 PM, Kani, Toshimitsu <toshi.kani@xxxxxxx> wrote:
> > On Wed, 2017-07-05 at 17:07 -0700, Dan Williams wrote:
> [..]
> >> We have symlinks in /dev/disk/by* to make it easier to identify
> >> storage devices, I think it makes sense to add udev rules for
> >> identifying volatile pmem and not try to differentiate this in the
> >> default kernel device name.
> >
> > I am not sure what might be a good way, but I am concerned because a
> > single block device naming do not represent both volatile and
> > persistent media today.
> We do have time to changes this if we find out this is critical. Maybe
> it's best to ask Linux distro folks what would be easier for them?

I'm not really concerned about it, because SCSI devices for example
might not be persistent as well with Ñcsi_debug, target_core_rd or
volatile qemu devices.

That being said I really don't understand the purpose of these volatile
nfit ranges. Are they seen in the wild? If yes what's the use case?
If not why do we even need to support them?