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

From: Linda Knippers
Date: Thu Jul 21 2016 - 16:11:10 EST

On 7/21/2016 3:46 PM, Dan Williams wrote:
> 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?

It's also possible that a platform might only support ARS at boot time
so subsequent scrubs would fail or not return any new information.
I don't think there's a way to know that in advice though.

-- ljk