Re: [PATCH v2 2/3] nfit, libnvdimm: allow an ARS scrub to be triggered on demand

From: Dan Williams
Date: Thu Jul 21 2016 - 15:46:22 EST

On Thu, Jul 21, 2016 at 12:40 PM, Linda Knippers <linda.knippers@xxxxxxx> wrote:
> On 07/20/2016 09:50 PM, Vishal Verma wrote:
>> Normally, an ARS (Address Range Scrub) only happens at
>> boot/initialization time. There can however arise situations where a
>> bus-wide rescan is needed - notably, in the case of discovering a latent
>> media error, we should do a full rescan to figure out what other sectors
>> are bad, and thus potentially avoid triggering an mce on them in the
>> future. Also provide a sysfs trigger to start a bus-wide scrub.
> I don't see anything in here that checks to see if the platform actually
> supports ARS before setting all this stuff up. Setting up an MCE handler
> and exposing a sysfs trigger for something that is optional and perhaps
> not implemented doesn't seem helpful. Or is there a check that I missed?

We'll get -ENOTTY to ars_start(), but you're right it's a good idea to
hide the scrub attribute if a platform does not have ars support.

Vishal, can you add an is_visible() routine to
acpi_nfit_attribute_group() to hide 'scrub' on platforms that do not
implement the ARS commands?