Re: [PATCH 3/6] nfit/ars: Allow root to busy-poll the ARS state machine

[Dan Williams <dan.j.williams@intel.com>]

On Thu, Feb 14, 2019 at 12:23 PM Dan Williams <dan.j.williams@intel.com> wrote:
>
> The ARS implementation implements exponential back-off on the poll
> interval to prevent high-frequency access to the DIMM / platform
> interface. Depending on when the ARS completes the poll interval may
> exceed the completion event by minutes. Allow root to reset the timeout
> each time it probes the status. A one-second timeout is still enforced,
> but root can otherwise can control the poll interval.
>
> Reported-by: Erwin Tsaur <erwin.tsaur@oracle.com>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
> ---
>  drivers/acpi/nfit/core.c |    6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/drivers/acpi/nfit/core.c b/drivers/acpi/nfit/core.c
> index 934be96dc149..5ec0e19760ea 100644
> --- a/drivers/acpi/nfit/core.c
> +++ b/drivers/acpi/nfit/core.c
> @@ -1328,6 +1328,12 @@ static ssize_t scrub_show(struct device *dev,
>                 rc = sprintf(buf, "%d%s", acpi_desc->scrub_count,
>                                 acpi_desc->scrub_busy
>                                 && !acpi_desc->cancel ? "+\n" : "\n");
> +               /* Allow an admin to poll the busy state at a higher rate */
> +               if (acpi_desc->scrub_busy && !acpi_desc->cancel
> +                               && capable(CAP_SYS_RAWIO)) {
> +                       acpi_desc->scrub_tmo = 1;
> +                       queue_delayed_work(nfit_wq, &acpi_desc->dwork, HZ);

Whoops, just realized this should be mod_delayed_work().
queue_delayed_work() is a nop if the work is already scheduled. v2
inbound.