nfit/ars: Allow root to busy-poll the ARS state machine

djbw · djbw · commit 5479b2757f26 · 2019-02-20T14:18:59.000-08:00
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. Fixes: bc6ba80 ("nfit, address-range-scrub: rework and simplify ARS...") Cc: <stable@vger.kernel.org> Reported-by: Erwin Tsaur <erwin.tsaur@oracle.com> Reviewed-by: Toshi Kani <toshi.kani@hpe.com> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
diff --git a/drivers/acpi/nfit/core.c b/drivers/acpi/nfit/core.c
@@ -1333,6 +1333,13 @@ static ssize_t scrub_show(struct device *dev,
 	busy = test_bit(ARS_BUSY, &acpi_desc->scrub_flags)
 		&& !test_bit(ARS_CANCEL, &acpi_desc->scrub_flags);
 	rc = sprintf(buf, "%d%s", acpi_desc->scrub_count, busy ? "+\n" : "\n");
+	/* Allow an admin to poll the busy state at a higher rate */
+	if (busy && capable(CAP_SYS_RAWIO) && !test_and_set_bit(ARS_POLL,
+				&acpi_desc->scrub_flags)) {
+		acpi_desc->scrub_tmo = 1;
+		mod_delayed_work(nfit_wq, &acpi_desc->dwork, HZ);
+	}
+
 	mutex_unlock(&acpi_desc->init_mutex);
 	device_unlock(dev);
 	return rc;
@@ -3187,6 +3194,7 @@ static void acpi_nfit_scrub(struct work_struct *work)
 	else
 		notify_ars_done(acpi_desc);
 	memset(acpi_desc->ars_status, 0, acpi_desc->max_ars);
+	clear_bit(ARS_POLL, &acpi_desc->scrub_flags);
 	mutex_unlock(&acpi_desc->init_mutex);
 }
 
diff --git a/drivers/acpi/nfit/nfit.h b/drivers/acpi/nfit/nfit.h
@@ -213,6 +213,7 @@ struct nfit_mem {
 enum scrub_flags {
 	ARS_BUSY,
 	ARS_CANCEL,
+	ARS_POLL,
 };
 
 struct acpi_nfit_desc {
