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Commit 40221d56 authored by Dan Williams's avatar Dan Williams Committed by Greg Kroah-Hartman
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nfit/ars: Allow root to busy-poll the ARS state machine 



commit 5479b2757f26fe9908fc341d105b2097fe820b6f upstream.

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: bc6ba808 ("nfit, address-range-scrub: rework and simplify ARS...")
Cc: <stable@vger.kernel.org>
Reported-by: default avatarErwin Tsaur <erwin.tsaur@oracle.com>
Reviewed-by: default avatarToshi Kani <toshi.kani@hpe.com>
Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent bc18c259

drivers/acpi/nfit/core.c

+8 −0
Original line number Diff line number Diff line
@@ -1314,6 +1314,13 @@ 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;
@@ -3075,6 +3082,7 @@ 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);

}

drivers/acpi/nfit/nfit.h

+1 −0
Original line number Diff line number Diff line
@@ -184,6 +184,7 @@ struct nfit_mem { 
enum scrub_flags {

	ARS_BUSY,

	ARS_CANCEL,

	ARS_POLL,

};



struct acpi_nfit_desc {