On Thu, Jun 29, 2017 at 12:20 PM, Linda Knippers <linda.knippers@xxxxxxx> wrote: > On 06/29/2017 01:54 PM, Dan Williams wrote: >> Allow volatile nfit ranges to participate in all the same infrastructure >> provided for persistent memory regions. > > This seems to be a bit more than "other rework". It's part of the rationale for having a "write_cache" control attribute. There's only so much I can squeeze into the subject line, but it is mentioned in the cover letter. >> A resulting resulting namespace >> device will still be called "pmem", but the parent region type will be >> "nd_volatile". > > What does this look like to a user or admin? How does someone know that > /dev/pmemX is persistent memory and /dev/pmemY isn't? Someone shouldn't > have to weed through /sys or ndctl some other interface to figure that out > in the future if they don't have to do that today. We have different > names for BTT namespaces. Is there a different name for volatile ranges? No, the block device name is still /dev/pmem. It's already the case that you need to check behind just the name of the device to figure out if something is actually volatile or not (see memmap=ss!nn configurations), so I would not be in favor of changing the device name if we think the memory might not be persistent. Moreover, I think it was a mistake that we change the device name for btt or not, and I'm glad Matthew talked me out of making the same mistake with memory-mode vs raw-mode pmem namespaces. So, the block device name just reflects the driver of the block device, not the properties of the device, just like all other block device instances.
