nfit, address-range-scrub: rework and simplify ARS state machine

ARS is an operation that can take 10s to 100s of seconds to find media
errors that should rarely be present. If the platform crashes due to
media errors in persistent memory, the expectation is that the BIOS will
report those known errors in a 'short' ARS request.

A 'short' ARS request asks platform firmware to return an ARS payload
with all known errors, but without issuing a 'long' scrub. At driver
init a short request is issued to all PMEM ranges before registering
regions. Then, in the background, a long ARS is scheduled for each
region.

The ARS implementation is simplified to centralize ARS completion work
in the ars_complete() helper. The timeout is removed since there is no
facility to cancel ARS, and this otherwise arranges for system init to
never be blocked waiting for a 'long' ARS. The ars_state flags are used
to coordinate ARS requests from driver init, ARS requests from
userspace, and ARS requests in response to media error notifications.

Given that there is no notification of ARS completion the implementation
still needs to poll. It backs off exponentially to a maximum poll period
of 30 minutes.
Suggested-by: Toshi Kani <toshi.kani@hpe.com>
Co-developed-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

drivers/acpi/nfit/core.c

@@ -35,16 +35,6 @@ static bool force_enable_dimms;
 module_param(force_enable_dimms, bool, S_IRUGO|S_IWUSR);
 MODULE_PARM_DESC(force_enable_dimms, "Ignore _STA (ACPI DIMM device) status");
 
-static unsigned int scrub_timeout = NFIT_ARS_TIMEOUT;
-module_param(scrub_timeout, uint, S_IRUGO|S_IWUSR);
-MODULE_PARM_DESC(scrub_timeout, "Initial scrub timeout in seconds");
-
-/* after three payloads of overflow, it's dead jim */
-static unsigned int scrub_overflow_abort = 3;
-module_param(scrub_overflow_abort, uint, S_IRUGO|S_IWUSR);
-MODULE_PARM_DESC(scrub_overflow_abort,
-		"Number of times we overflow ARS results before abort");
-
 static bool disable_vendor_specific;
 module_param(disable_vendor_specific, bool, S_IRUGO);
 MODULE_PARM_DESC(disable_vendor_specific,
@@ -1251,7 +1241,7 @@ static ssize_t scrub_show(struct device *dev,
 
 		mutex_lock(&acpi_desc->init_mutex);
 		rc = sprintf(buf, "%d%s", acpi_desc->scrub_count,
-				work_busy(&acpi_desc->work)
+				work_busy(&acpi_desc->dwork.work)
 				&& !acpi_desc->cancel ? "+\n" : "\n");
 		mutex_unlock(&acpi_desc->init_mutex);
 	}
@@ -2452,7 +2442,8 @@ static int ars_start(struct acpi_nfit_desc *acpi_desc, struct nfit_spa *nfit_spa
 	memset(&ars_start, 0, sizeof(ars_start));
 	ars_start.address = spa->address;
 	ars_start.length = spa->length;
-	ars_start.flags = acpi_desc->ars_start_flags;
+	if (test_bit(ARS_SHORT, &nfit_spa->ars_state))
+		ars_start.flags = ND_ARS_RETURN_PREV_DATA;
 	if (nfit_spa_type(spa) == NFIT_SPA_PM)
 		ars_start.type = ND_ARS_PERSISTENT;
 	else if (nfit_spa_type(spa) == NFIT_SPA_VOLATILE)
@@ -2500,6 +2491,52 @@ static int ars_get_status(struct acpi_nfit_desc *acpi_desc)
 	return cmd_rc;
 }
 
+static void ars_complete(struct acpi_nfit_desc *acpi_desc,
+		struct nfit_spa *nfit_spa)
+{
+	struct nd_cmd_ars_status *ars_status = acpi_desc->ars_status;
+	struct acpi_nfit_system_address *spa = nfit_spa->spa;
+	struct nd_region *nd_region = nfit_spa->nd_region;
+	struct device *dev;
+
+	if ((ars_status->address >= spa->address && ars_status->address
+				< spa->address + spa->length)
+			|| (ars_status->address < spa->address)) {
+		/*
+		 * Assume that if a scrub starts at an offset from the
+		 * start of nfit_spa that we are in the continuation
+		 * case.
+		 *
+		 * Otherwise, if the scrub covers the spa range, mark
+		 * any pending request complete.
+		 */
+		if (ars_status->address + ars_status->length
+				>= spa->address + spa->length)
+				/* complete */;
+		else
+			return;
+	} else
+		return;
+
+	if (test_bit(ARS_DONE, &nfit_spa->ars_state))
+		return;
+
+	if (!test_and_clear_bit(ARS_REQ, &nfit_spa->ars_state))
+		return;
+
+	if (nd_region) {
+		dev = nd_region_dev(nd_region);
+		nvdimm_region_notify(nd_region, NVDIMM_REVALIDATE_POISON);
+	} else
+		dev = acpi_desc->dev;
+
+	dev_dbg(dev, "ARS: range %d %s complete\n", spa->range_index,
+			test_bit(ARS_SHORT, &nfit_spa->ars_state)
+			? "short" : "long");
+	clear_bit(ARS_SHORT, &nfit_spa->ars_state);
+	set_bit(ARS_DONE, &nfit_spa->ars_state);
+}
+
 static int ars_status_process_records(struct acpi_nfit_desc *acpi_desc)
 {
 	struct nvdimm_bus *nvdimm_bus = acpi_desc->nvdimm_bus;
@@ -2764,6 +2801,7 @@ static int acpi_nfit_query_poison(struct acpi_nfit_desc *acpi_desc)
 		return -ENOMEM;
 
 	rc = ars_get_status(acpi_desc);
+
 	if (rc < 0 && rc != -ENOSPC)
 		return rc;
 
@@ -2773,223 +2811,125 @@ static int acpi_nfit_query_poison(struct acpi_nfit_desc *acpi_desc)
 	return 0;
 }
 
-static void acpi_nfit_async_scrub(struct acpi_nfit_desc *acpi_desc,
-		struct nfit_spa *nfit_spa)
+static int ars_register(struct acpi_nfit_desc *acpi_desc, struct nfit_spa *nfit_spa,
+		int *query_rc)
 {
-	struct acpi_nfit_system_address *spa = nfit_spa->spa;
-	unsigned int overflow_retry = scrub_overflow_abort;
-	u64 init_ars_start = 0, init_ars_len = 0;
-	struct device *dev = acpi_desc->dev;
-	unsigned int tmo = scrub_timeout;
-	int rc;
-
-	if (!test_bit(ARS_REQ, &nfit_spa->ars_state) || !nfit_spa->nd_region)
-		return;
-
-	rc = ars_start(acpi_desc, nfit_spa);
-	/*
-	 * If we timed out the initial scan we'll still be busy here,
-	 * and will wait another timeout before giving up permanently.
-	 */
-	if (rc < 0 && rc != -EBUSY)
-		return;
+	int rc = *query_rc;
 
-	do {
-		u64 ars_start, ars_len;
-
-		if (acpi_desc->cancel)
-			break;
-		rc = acpi_nfit_query_poison(acpi_desc);
-		if (rc == -ENOTTY)
-			break;
-		if (rc == -EBUSY && !tmo) {
-			dev_warn(dev, "range %d ars timeout, aborting\n",
-					spa->range_index);
-			break;
-		}
+	set_bit(ARS_REQ, &nfit_spa->ars_state);
+	set_bit(ARS_SHORT, &nfit_spa->ars_state);
 
+	switch (rc) {
+	case 0:
+	case -EAGAIN:
+		rc = ars_start(acpi_desc, nfit_spa);
 		if (rc == -EBUSY) {
-			/*
-			 * Note, entries may be appended to the list
-			 * while the lock is dropped, but the workqueue
-			 * being active prevents entries being deleted /
-			 * freed.
-			 */
-			mutex_unlock(&acpi_desc->init_mutex);
-			ssleep(1);
-			tmo--;
-			mutex_lock(&acpi_desc->init_mutex);
-			continue;
-		}
-
-		/* we got some results, but there are more pending... */
-		if (rc == -ENOSPC && overflow_retry--) {
-			if (!init_ars_len) {
-				init_ars_len = acpi_desc->ars_status->length;
-				init_ars_start = acpi_desc->ars_status->address;
-			}
-			rc = ars_continue(acpi_desc);
-		}
-
-		if (rc < 0) {
-			dev_warn(dev, "range %d ars continuation failed\n",
-					spa->range_index);
+			*query_rc = rc;
 			break;
-		}
-
-		if (init_ars_len) {
-			ars_start = init_ars_start;
-			ars_len = init_ars_len;
+		} else if (rc == 0) {
+			rc = acpi_nfit_query_poison(acpi_desc);
 		} else {
-			ars_start = acpi_desc->ars_status->address;
-			ars_len = acpi_desc->ars_status->length;
+			set_bit(ARS_FAILED, &nfit_spa->ars_state);
+			break;
 		}
-		dev_dbg(dev, "spa range: %d ars from %#llx + %#llx complete\n",
-				spa->range_index, ars_start, ars_len);
-		/* notify the region about new poison entries */
-		nvdimm_region_notify(nfit_spa->nd_region,
-				NVDIMM_REVALIDATE_POISON);
+		if (rc == -EAGAIN)
+			clear_bit(ARS_SHORT, &nfit_spa->ars_state);
+		else if (rc == 0)
+			ars_complete(acpi_desc, nfit_spa);
+		break;
+	case -EBUSY:
+	case -ENOSPC:
 		break;
-	} while (1);
+	default:
+		set_bit(ARS_FAILED, &nfit_spa->ars_state);
+		break;
+	}
+
+	if (test_and_clear_bit(ARS_DONE, &nfit_spa->ars_state))
+		set_bit(ARS_REQ, &nfit_spa->ars_state);
+
+	return acpi_nfit_register_region(acpi_desc, nfit_spa);
 }
 
-static void acpi_nfit_scrub(struct work_struct *work)
+static void ars_complete_all(struct acpi_nfit_desc *acpi_desc)
 {
-	struct device *dev;
-	u64 init_scrub_length = 0;
 	struct nfit_spa *nfit_spa;
-	u64 init_scrub_address = 0;
-	bool init_ars_done = false;
-	struct acpi_nfit_desc *acpi_desc;
-	unsigned int tmo = scrub_timeout;
-	unsigned int overflow_retry = scrub_overflow_abort;
-
-	acpi_desc = container_of(work, typeof(*acpi_desc), work);
-	dev = acpi_desc->dev;
-
-	/*
-	 * We scrub in 2 phases.  The first phase waits for any platform
-	 * firmware initiated scrubs to complete and then we go search for the
-	 * affected spa regions to mark them scanned.  In the second phase we
-	 * initiate a directed scrub for every range that was not scrubbed in
-	 * phase 1. If we're called for a 'rescan', we harmlessly pass through
-	 * the first phase, but really only care about running phase 2, where
-	 * regions can be notified of new poison.
-	 */
 
-	/* process platform firmware initiated scrubs */
- retry:
-	mutex_lock(&acpi_desc->init_mutex);
 	list_for_each_entry(nfit_spa, &acpi_desc->spas, list) {
-		struct nd_cmd_ars_status *ars_status;
-		struct acpi_nfit_system_address *spa;
-		u64 ars_start, ars_len;
-		int rc;
-
-		if (acpi_desc->cancel)
-			break;
-
-		if (nfit_spa->nd_region)
-			continue;
-
-		if (init_ars_done) {
-			/*
-			 * No need to re-query, we're now just
-			 * reconciling all the ranges covered by the
-			 * initial scrub
-			 */
-			rc = 0;
-		} else
-			rc = acpi_nfit_query_poison(acpi_desc);
-
-		if (rc == -ENOTTY) {
-			/* no ars capability, just register spa and move on */
-			acpi_nfit_register_region(acpi_desc, nfit_spa);
+		if (test_bit(ARS_FAILED, &nfit_spa->ars_state))
 			continue;
-		}
-
-		if (rc == -EBUSY && !tmo) {
-			/* fallthrough to directed scrub in phase 2 */
-			dev_warn(dev, "timeout awaiting ars results, continuing...\n");
-			break;
-		} else if (rc == -EBUSY) {
-			mutex_unlock(&acpi_desc->init_mutex);
-			ssleep(1);
-			tmo--;
-			goto retry;
-		}
+		ars_complete(acpi_desc, nfit_spa);
+	}
+}
 
-		/* we got some results, but there are more pending... */
-		if (rc == -ENOSPC && overflow_retry--) {
-			ars_status = acpi_desc->ars_status;
-			/*
-			 * Record the original scrub range, so that we
-			 * can recall all the ranges impacted by the
-			 * initial scrub.
-			 */
-			if (!init_scrub_length) {
-				init_scrub_length = ars_status->length;
-				init_scrub_address = ars_status->address;
-			}
-			rc = ars_continue(acpi_desc);
-			if (rc == 0) {
-				mutex_unlock(&acpi_desc->init_mutex);
-				goto retry;
-			}
-		}
+static unsigned int __acpi_nfit_scrub(struct acpi_nfit_desc *acpi_desc,
+		int query_rc)
+{
+	unsigned int tmo = acpi_desc->scrub_tmo;
+	struct device *dev = acpi_desc->dev;
+	struct nfit_spa *nfit_spa;
 
-		if (rc < 0) {
-			/*
-			 * Initial scrub failed, we'll give it one more
-			 * try below...
-			 */
-			break;
-		}
+	if (acpi_desc->cancel)
+		return 0;
 
-		/* We got some final results, record completed ranges */
-		ars_status = acpi_desc->ars_status;
-		if (init_scrub_length) {
-			ars_start = init_scrub_address;
-			ars_len = ars_start + init_scrub_length;
-		} else {
-			ars_start = ars_status->address;
-			ars_len = ars_status->length;
-		}
-		spa = nfit_spa->spa;
+	if (query_rc == -EBUSY) {
+		dev_dbg(dev, "ARS: ARS busy\n");
+		return min(30U * 60U, tmo * 2);
+	}
+	if (query_rc == -ENOSPC) {
+		dev_dbg(dev, "ARS: ARS continue\n");
+		ars_continue(acpi_desc);
+		return 1;
+	}
+	if (query_rc && query_rc != -EAGAIN) {
+		unsigned long long addr, end;
 
-		if (!init_ars_done) {
-			init_ars_done = true;
-			dev_dbg(dev, "init scrub %#llx + %#llx complete\n",
-					ars_start, ars_len);
-		}
-		if (ars_start <= spa->address && ars_start + ars_len
-				>= spa->address + spa->length)
-			acpi_nfit_register_region(acpi_desc, nfit_spa);
+		addr = acpi_desc->ars_status->address;
+		end = addr + acpi_desc->ars_status->length;
+		dev_dbg(dev, "ARS: %llx-%llx failed (%d)\n", addr, end,
+				query_rc);
 	}
 
-	/*
-	 * For all the ranges not covered by an initial scrub we still
-	 * want to see if there are errors, but it's ok to discover them
-	 * asynchronously.
-	 */
+	ars_complete_all(acpi_desc);
 	list_for_each_entry(nfit_spa, &acpi_desc->spas, list) {
-		/*
-		 * Flag all the ranges that still need scrubbing, but
-		 * register them now to make data available.
-		 */
-		if (!nfit_spa->nd_region) {
-			set_bit(ARS_REQ, &nfit_spa->ars_state);
-			acpi_nfit_register_region(acpi_desc, nfit_spa);
+		if (test_bit(ARS_FAILED, &nfit_spa->ars_state))
+			continue;
+		if (test_bit(ARS_REQ, &nfit_spa->ars_state)) {
+			int rc = ars_start(acpi_desc, nfit_spa);
+
+			clear_bit(ARS_DONE, &nfit_spa->ars_state);
+			dev = nd_region_dev(nfit_spa->nd_region);
+			dev_dbg(dev, "ARS: range %d ARS start (%d)\n",
+					nfit_spa->spa->range_index, rc);
+			if (rc == 0 || rc == -EBUSY)
+				return 1;
+			dev_err(dev, "ARS: range %d ARS failed (%d)\n",
+					nfit_spa->spa->range_index, rc);
+			set_bit(ARS_FAILED, &nfit_spa->ars_state);
 		}
 	}
-	acpi_desc->init_complete = 1;
+	return 0;
+}
 
-	list_for_each_entry(nfit_spa, &acpi_desc->spas, list)
-		acpi_nfit_async_scrub(acpi_desc, nfit_spa);
-	acpi_desc->scrub_count++;
-	acpi_desc->ars_start_flags = 0;
-	if (acpi_desc->scrub_count_state)
-		sysfs_notify_dirent(acpi_desc->scrub_count_state);
+static void acpi_nfit_scrub(struct work_struct *work)
+{
+	struct acpi_nfit_desc *acpi_desc;
+	unsigned int tmo;
+	int query_rc;
+
+	acpi_desc = container_of(work, typeof(*acpi_desc), dwork.work);
+	mutex_lock(&acpi_desc->init_mutex);
+	query_rc = acpi_nfit_query_poison(acpi_desc);
+	tmo = __acpi_nfit_scrub(acpi_desc, query_rc);
+	if (tmo) {
+		queue_delayed_work(nfit_wq, &acpi_desc->dwork, tmo * HZ);
+		acpi_desc->scrub_tmo = tmo;
+	} else {
+		acpi_desc->scrub_count++;
+		if (acpi_desc->scrub_count_state)
+			sysfs_notify_dirent(acpi_desc->scrub_count_state);
+	}
+	memset(acpi_desc->ars_status, 0, acpi_desc->max_ars);
 	mutex_unlock(&acpi_desc->init_mutex);
 }
 
@@ -3015,33 +2955,61 @@ static void acpi_nfit_init_ars(struct acpi_nfit_desc *acpi_desc,
 	nfit_spa->max_ars = ars_cap.max_ars_out;
 	nfit_spa->clear_err_unit = ars_cap.clear_err_unit;
 	acpi_desc->max_ars = max(nfit_spa->max_ars, acpi_desc->max_ars);
+	clear_bit(ARS_FAILED, &nfit_spa->ars_state);
+	set_bit(ARS_REQ, &nfit_spa->ars_state);
 }
 
-
 static int acpi_nfit_register_regions(struct acpi_nfit_desc *acpi_desc)
 {
 	struct nfit_spa *nfit_spa;
+	int rc, query_rc;
 
 	list_for_each_entry(nfit_spa, &acpi_desc->spas, list) {
-		int rc, type = nfit_spa_type(nfit_spa->spa);
-
-		/* PMEM and VMEM will be registered by the ARS workqueue */
-		if (type == NFIT_SPA_PM || type == NFIT_SPA_VOLATILE) {
+		set_bit(ARS_FAILED, &nfit_spa->ars_state);
+		switch (nfit_spa_type(nfit_spa->spa)) {
+		case NFIT_SPA_VOLATILE:
+		case NFIT_SPA_PM:
 			acpi_nfit_init_ars(acpi_desc, nfit_spa);
-			continue;
+			break;
 		}
-		/* BLK apertures belong to BLK region registration below */
-		if (type == NFIT_SPA_BDW)
-			continue;
-		/* BLK regions don't need to wait for ARS results */
-		rc = acpi_nfit_register_region(acpi_desc, nfit_spa);
-		if (rc)
-			return rc;
 	}
 
-	acpi_desc->ars_start_flags = 0;
-	if (!acpi_desc->cancel)
-		queue_work(nfit_wq, &acpi_desc->work);
+	/*
+	 * Reap any results that might be pending before starting new
+	 * short requests.
+	 */
+	query_rc = acpi_nfit_query_poison(acpi_desc);
+	if (query_rc == 0)
+		ars_complete_all(acpi_desc);
+
+	list_for_each_entry(nfit_spa, &acpi_desc->spas, list)
+		switch (nfit_spa_type(nfit_spa->spa)) {
+		case NFIT_SPA_VOLATILE:
+		case NFIT_SPA_PM:
+			/* register regions and kick off initial ARS run */
+			rc = ars_register(acpi_desc, nfit_spa, &query_rc);
+			if (rc)
+				return rc;
+			break;
+		case NFIT_SPA_BDW:
+			/* nothing to register */
+			break;
+		case NFIT_SPA_DCR:
+		case NFIT_SPA_VDISK:
+		case NFIT_SPA_VCD:
+		case NFIT_SPA_PDISK:
+		case NFIT_SPA_PCD:
+			/* register known regions that don't support ARS */
+			rc = acpi_nfit_register_region(acpi_desc, nfit_spa);
+			if (rc)
+				return rc;
+			break;
+		default:
+			/* don't register unknown regions */
+			break;
+		}
+
+	queue_delayed_work(nfit_wq, &acpi_desc->dwork, 0);
 	return 0;
 }
 
@@ -3176,49 +3144,20 @@ int acpi_nfit_init(struct acpi_nfit_desc *acpi_desc, void *data, acpi_size sz)
 }
 EXPORT_SYMBOL_GPL(acpi_nfit_init);
 
-struct acpi_nfit_flush_work {
-	struct work_struct work;
-	struct completion cmp;
-};
-
-static void flush_probe(struct work_struct *work)
-{
-	struct acpi_nfit_flush_work *flush;
-
-	flush = container_of(work, typeof(*flush), work);
-	complete(&flush->cmp);
-}
-
 static int acpi_nfit_flush_probe(struct nvdimm_bus_descriptor *nd_desc)
 {
 	struct acpi_nfit_desc *acpi_desc = to_acpi_nfit_desc(nd_desc);
 	struct device *dev = acpi_desc->dev;
-	struct acpi_nfit_flush_work flush;
-	int rc;
 
-	/* bounce the device lock to flush acpi_nfit_add / acpi_nfit_notify */
+	/* Bounce the device lock to flush acpi_nfit_add / acpi_nfit_notify */
 	device_lock(dev);
 	device_unlock(dev);
 
-	/* bounce the init_mutex to make init_complete valid */
+	/* Bounce the init_mutex to complete initial registration */
 	mutex_lock(&acpi_desc->init_mutex);
-	if (acpi_desc->cancel || acpi_desc->init_complete) {
-		mutex_unlock(&acpi_desc->init_mutex);
-		return 0;
-	}
-
-	/*
-	 * Scrub work could take 10s of seconds, userspace may give up so we
-	 * need to be interruptible while waiting.
-	 */
-	INIT_WORK_ONSTACK(&flush.work, flush_probe);
-	init_completion(&flush.cmp);
-	queue_work(nfit_wq, &flush.work);
 	mutex_unlock(&acpi_desc->init_mutex);
 
-	rc = wait_for_completion_interruptible(&flush.cmp);
-	cancel_work_sync(&flush.work);
-	return rc;
+	return 0;
 }
 
 static int acpi_nfit_clear_to_send(struct nvdimm_bus_descriptor *nd_desc,
@@ -3237,7 +3176,7 @@ static int acpi_nfit_clear_to_send(struct nvdimm_bus_descriptor *nd_desc,
 	 * just needs guarantees that any ars it initiates are not
 	 * interrupted by any intervening start reqeusts from userspace.
 	 */
-	if (work_busy(&acpi_desc->work))
+	if (work_busy(&acpi_desc->dwork.work))
 		return -EBUSY;
 
 	return 0;
@@ -3246,11 +3185,9 @@ static int acpi_nfit_clear_to_send(struct nvdimm_bus_descriptor *nd_desc,
 int acpi_nfit_ars_rescan(struct acpi_nfit_desc *acpi_desc, unsigned long flags)
 {
 	struct device *dev = acpi_desc->dev;
+	int scheduled = 0, busy = 0;
 	struct nfit_spa *nfit_spa;
 
-	if (work_busy(&acpi_desc->work))
-		return -EBUSY;
-
 	mutex_lock(&acpi_desc->init_mutex);
 	if (acpi_desc->cancel) {
 		mutex_unlock(&acpi_desc->init_mutex);
@@ -3258,21 +3195,32 @@ int acpi_nfit_ars_rescan(struct acpi_nfit_desc *acpi_desc, unsigned long flags)
 	}
 
 	list_for_each_entry(nfit_spa, &acpi_desc->spas, list) {
-		struct acpi_nfit_system_address *spa = nfit_spa->spa;
+		int type = nfit_spa_type(nfit_spa->spa);
 
-		if (nfit_spa_type(spa) != NFIT_SPA_PM)
+		if (type != NFIT_SPA_PM && type != NFIT_SPA_VOLATILE)
+			continue;
+		if (test_bit(ARS_FAILED, &nfit_spa->ars_state))
 			continue;
 
-		set_bit(ARS_REQ, &nfit_spa->ars_state);
+		if (test_and_set_bit(ARS_REQ, &nfit_spa->ars_state))
+			busy++;
+		else {
+			if (test_bit(ARS_SHORT, &flags))
+				set_bit(ARS_SHORT, &nfit_spa->ars_state);
+			scheduled++;
+		}
+	}
+	if (scheduled) {
+		queue_delayed_work(nfit_wq, &acpi_desc->dwork, 0);
+		dev_dbg(dev, "ars_scan triggered\n");
 	}
-	acpi_desc->ars_start_flags = 0;
-	if (test_bit(ARS_SHORT, &flags))
-		acpi_desc->ars_start_flags |= ND_ARS_RETURN_PREV_DATA;
-	queue_work(nfit_wq, &acpi_desc->work);
-	dev_dbg(dev, "ars_scan triggered\n");
 	mutex_unlock(&acpi_desc->init_mutex);
 
-	return 0;
+	if (scheduled)
+		return 0;
+	if (busy)
+		return -EBUSY;
+	return -ENOTTY;
 }
 
 void acpi_nfit_desc_init(struct acpi_nfit_desc *acpi_desc, struct device *dev)
@@ -3299,7 +3247,8 @@ void acpi_nfit_desc_init(struct acpi_nfit_desc *acpi_desc, struct device *dev)
 	INIT_LIST_HEAD(&acpi_desc->dimms);
 	INIT_LIST_HEAD(&acpi_desc->list);
 	mutex_init(&acpi_desc->init_mutex);
-	INIT_WORK(&acpi_desc->work, acpi_nfit_scrub);
+	acpi_desc->scrub_tmo = 1;
+	INIT_DELAYED_WORK(&acpi_desc->dwork, acpi_nfit_scrub);
 }
 EXPORT_SYMBOL_GPL(acpi_nfit_desc_init);
 
@@ -3323,6 +3272,7 @@ void acpi_nfit_shutdown(void *data)
 
 	mutex_lock(&acpi_desc->init_mutex);
 	acpi_desc->cancel = 1;
+	cancel_delayed_work_sync(&acpi_desc->dwork);
 	mutex_unlock(&acpi_desc->init_mutex);
 
 	/*

drivers/acpi/nfit/nfit.h

@@ -197,18 +197,18 @@ struct acpi_nfit_desc {
 	struct device *dev;
 	u8 ars_start_flags;
 	struct nd_cmd_ars_status *ars_status;
-	struct work_struct work;
+	struct delayed_work dwork;
 	struct list_head list;
 	struct kernfs_node *scrub_count_state;
 	unsigned int max_ars;
 	unsigned int scrub_count;
 	unsigned int scrub_mode;
 	unsigned int cancel:1;
-	unsigned int init_complete:1;
 	unsigned long dimm_cmd_force_en;
 	unsigned long bus_cmd_force_en;
 	unsigned long bus_nfit_cmd_force_en;
 	unsigned int platform_cap;
+	unsigned int scrub_tmo;
 	int (*blk_do_io)(struct nd_blk_region *ndbr, resource_size_t dpa,
 			void *iobuf, u64 len, int rw);
 };