acpi, nfit: Fix Address Range Scrub completion tracking

The Address Range Scrub implementation tried to skip running scrubs
against ranges that were already scrubbed by the BIOS. Unfortunately
that support also resulted in early scrub completions as evidenced by
this debug output from nfit_test:

    nd_region region9: ARS: range 1 short complete
    nd_region region3: ARS: range 1 short complete
    nd_region region4: ARS: range 2 ARS start (0)
    nd_region region4: ARS: range 2 short complete

...i.e. completions without any indications that the scrub was started.

This state of affairs was hard to see in the code due to the
proliferation of state bits and mistakenly trying to track done state
per-range when the completion is a global property of the bus.

So, kill the four ARS state bits (ARS_REQ, ARS_REQ_REDO, ARS_DONE, and
ARS_SHORT), and replace them with just 2 request flags ARS_REQ_SHORT and
ARS_REQ_LONG. The implementation will still complete and reap the
results of BIOS initiated ARS, but it will not attempt to use that
information to affect the completion status of scrubbing the ranges from
a Linux perspective.

Instead, try to synchronously run a short ARS per range at init time and
schedule a long scrub in the background. If ARS is busy with an ARS
request, schedule both a short and a long scrub for when ARS returns to
idle. This logic also satisfies the intent of what ARS_REQ_REDO was
trying to achieve. The new rule is that the REQ flag stays set until the
next successful ars_start() for that range.

With the new policy that the REQ flags are not cleared until the next
start, the implementation no longer loses requests as can be seen from
the following log:

    nd_region region3: ARS: range 1 ARS start short (0)
    nd_region region9: ARS: range 1 ARS start short (0)
    nd_region region3: ARS: range 1 complete
    nd_region region4: ARS: range 2 ARS start short (0)
    nd_region region9: ARS: range 1 complete
    nd_region region9: ARS: range 1 ARS start long (0)
    nd_region region4: ARS: range 2 complete
    nd_region region3: ARS: range 1 ARS start long (0)
    nd_region region9: ARS: range 1 complete
    nd_region region3: ARS: range 1 complete
    nd_region region4: ARS: range 2 ARS start long (0)
    nd_region region4: ARS: range 2 complete

...note that the nfit_test emulated driver provides 2 buses, that is why
some of the range indices are duplicated. Notice that each range
now successfully completes a short and long scrub.

Cc: <stable@vger.kernel.org>
Fixes: 14c73f99 ("nfit, address-range-scrub: introduce nfit_spa->ars_state")
Fixes: cc3d3458 ("acpi/nfit: queue issuing of ars when an uc error...")
Reported-by: Jacek Zloch <jacek.zloch@intel.com>
Reported-by: Krzysztof Rusocki <krzysztof.rusocki@intel.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

drivers/acpi/nfit/core.c

@@ -2549,7 +2549,8 @@ static int ars_get_cap(struct acpi_nfit_desc *acpi_desc,
 	return cmd_rc;
 }
 
-static int ars_start(struct acpi_nfit_desc *acpi_desc, struct nfit_spa *nfit_spa)
+static int ars_start(struct acpi_nfit_desc *acpi_desc,
+		struct nfit_spa *nfit_spa, enum nfit_ars_state req_type)
 {
 	int rc;
 	int cmd_rc;
@@ -2560,7 +2561,7 @@ 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;
-	if (test_bit(ARS_SHORT, &nfit_spa->ars_state))
+	if (req_type == ARS_REQ_SHORT)
 		ars_start.flags = ND_ARS_RETURN_PREV_DATA;
 	if (nfit_spa_type(spa) == NFIT_SPA_PM)
 		ars_start.type = ND_ARS_PERSISTENT;
@@ -2617,6 +2618,15 @@ static void ars_complete(struct acpi_nfit_desc *acpi_desc,
 	struct nd_region *nd_region = nfit_spa->nd_region;
 	struct device *dev;
 
+	lockdep_assert_held(&acpi_desc->init_mutex);
+	/*
+	 * Only advance the ARS state for ARS runs initiated by the
+	 * kernel, ignore ARS results from BIOS initiated runs for scrub
+	 * completion tracking.
+	 */
+	if (acpi_desc->scrub_spa != nfit_spa)
+		return;
+
 	if ((ars_status->address >= spa->address && ars_status->address
 				< spa->address + spa->length)
 			|| (ars_status->address < spa->address)) {
@@ -2636,28 +2646,13 @@ static void ars_complete(struct acpi_nfit_desc *acpi_desc,
 	} else
 		return;
 
-	if (test_bit(ARS_DONE, &nfit_spa->ars_state))
-		return;
-
-	if (!test_and_clear_bit(ARS_REQ, &nfit_spa->ars_state))
-		return;
-
+	acpi_desc->scrub_spa = NULL;
 	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);
-	if (test_and_clear_bit(ARS_REQ_REDO, &nfit_spa->ars_state)) {
-		set_bit(ARS_SHORT, &nfit_spa->ars_state);
-		set_bit(ARS_REQ, &nfit_spa->ars_state);
-		dev_dbg(dev, "ARS: processing scrub request received while in progress\n");
-	} else
-		set_bit(ARS_DONE, &nfit_spa->ars_state);
+	dev_dbg(dev, "ARS: range %d complete\n", spa->range_index);
 }
 
 static int ars_status_process_records(struct acpi_nfit_desc *acpi_desc)
@@ -2938,46 +2933,55 @@ static int acpi_nfit_query_poison(struct acpi_nfit_desc *acpi_desc)
 	return 0;
 }
 
-static int ars_register(struct acpi_nfit_desc *acpi_desc, struct nfit_spa *nfit_spa,
-		int *query_rc)
+static int ars_register(struct acpi_nfit_desc *acpi_desc,
+		struct nfit_spa *nfit_spa)
 {
-	int rc = *query_rc;
+	int rc;
 
-	if (no_init_ars)
+	if (no_init_ars || test_bit(ARS_FAILED, &nfit_spa->ars_state))
 		return acpi_nfit_register_region(acpi_desc, nfit_spa);
 
-	set_bit(ARS_REQ, &nfit_spa->ars_state);
-	set_bit(ARS_SHORT, &nfit_spa->ars_state);
+	set_bit(ARS_REQ_SHORT, &nfit_spa->ars_state);
+	set_bit(ARS_REQ_LONG, &nfit_spa->ars_state);
 
-	switch (rc) {
+	switch (acpi_nfit_query_poison(acpi_desc)) {
 	case 0:
 	case -EAGAIN:
-		rc = ars_start(acpi_desc, nfit_spa);
-		if (rc == -EBUSY) {
-			*query_rc = rc;
+		rc = ars_start(acpi_desc, nfit_spa, ARS_REQ_SHORT);
+		/* shouldn't happen, try again later */
+		if (rc == -EBUSY)
 			break;
-		} else if (rc == 0) {
-			rc = acpi_nfit_query_poison(acpi_desc);
-		} else {
+		if (rc) {
 			set_bit(ARS_FAILED, &nfit_spa->ars_state);
 			break;
 		}
-		if (rc == -EAGAIN)
-			clear_bit(ARS_SHORT, &nfit_spa->ars_state);
-		else if (rc == 0)
-			ars_complete(acpi_desc, nfit_spa);
+		clear_bit(ARS_REQ_SHORT, &nfit_spa->ars_state);
+		rc = acpi_nfit_query_poison(acpi_desc);
+		if (rc)
+			break;
+		acpi_desc->scrub_spa = nfit_spa;
+		ars_complete(acpi_desc, nfit_spa);
+		/*
+		 * If ars_complete() says we didn't complete the
+		 * short scrub, we'll try again with a long
+		 * request.
+		 */
+		acpi_desc->scrub_spa = NULL;
 		break;
 	case -EBUSY:
+	case -ENOMEM:
 	case -ENOSPC:
+		/*
+		 * BIOS was using ARS, wait for it to complete (or
+		 * resources to become available) and then perform our
+		 * own scrubs.
+		 */
 		break;
 	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);
 }
 
@@ -2999,6 +3003,8 @@ static unsigned int __acpi_nfit_scrub(struct acpi_nfit_desc *acpi_desc,
 	struct device *dev = acpi_desc->dev;
 	struct nfit_spa *nfit_spa;
 
+	lockdep_assert_held(&acpi_desc->init_mutex);
+
 	if (acpi_desc->cancel)
 		return 0;
 
@@ -3022,21 +3028,49 @@ static unsigned int __acpi_nfit_scrub(struct acpi_nfit_desc *acpi_desc,
 
 	ars_complete_all(acpi_desc);
 	list_for_each_entry(nfit_spa, &acpi_desc->spas, list) {
+		enum nfit_ars_state req_type;
+		int rc;
+
 		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);
+
+		/* prefer short ARS requests first */
+		if (test_bit(ARS_REQ_SHORT, &nfit_spa->ars_state))
+			req_type = ARS_REQ_SHORT;
+		else if (test_bit(ARS_REQ_LONG, &nfit_spa->ars_state))
+			req_type = ARS_REQ_LONG;
+		else
+			continue;
+		rc = ars_start(acpi_desc, nfit_spa, req_type);
+
+		dev = nd_region_dev(nfit_spa->nd_region);
+		dev_dbg(dev, "ARS: range %d ARS start %s (%d)\n",
+				nfit_spa->spa->range_index,
+				req_type == ARS_REQ_SHORT ? "short" : "long",
+				rc);
+		/*
+		 * Hmm, we raced someone else starting ARS? Try again in
+		 * a bit.
+		 */
+		if (rc == -EBUSY)
+			return 1;
+		if (rc == 0) {
+			dev_WARN_ONCE(dev, acpi_desc->scrub_spa,
+					"scrub start while range %d active\n",
+					acpi_desc->scrub_spa->spa->range_index);
+			clear_bit(req_type, &nfit_spa->ars_state);
+			acpi_desc->scrub_spa = nfit_spa;
+			/*
+			 * Consider this spa last for future scrub
+			 * requests
+			 */
+			list_move_tail(&nfit_spa->list, &acpi_desc->spas);
+			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);
 	}
 	return 0;
 }
@@ -3092,6 +3126,7 @@ static void acpi_nfit_init_ars(struct acpi_nfit_desc *acpi_desc,
 	struct nd_cmd_ars_cap ars_cap;
 	int rc;
 
+	set_bit(ARS_FAILED, &nfit_spa->ars_state);
 	memset(&ars_cap, 0, sizeof(ars_cap));
 	rc = ars_get_cap(acpi_desc, &ars_cap, nfit_spa);
 	if (rc < 0)
@@ -3108,16 +3143,14 @@ static void acpi_nfit_init_ars(struct acpi_nfit_desc *acpi_desc,
 	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;
+	int rc;
 
 	list_for_each_entry(nfit_spa, &acpi_desc->spas, list) {
-		set_bit(ARS_FAILED, &nfit_spa->ars_state);
 		switch (nfit_spa_type(nfit_spa->spa)) {
 		case NFIT_SPA_VOLATILE:
 		case NFIT_SPA_PM:
@@ -3126,20 +3159,12 @@ static int acpi_nfit_register_regions(struct acpi_nfit_desc *acpi_desc)
 		}
 	}
 
-	/*
-	 * 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);
+			rc = ars_register(acpi_desc, nfit_spa);
 			if (rc)
 				return rc;
 			break;
@@ -3334,7 +3359,8 @@ static int acpi_nfit_clear_to_send(struct nvdimm_bus_descriptor *nd_desc,
 	return 0;
 }
 
-int acpi_nfit_ars_rescan(struct acpi_nfit_desc *acpi_desc, unsigned long flags)
+int acpi_nfit_ars_rescan(struct acpi_nfit_desc *acpi_desc,
+		enum nfit_ars_state req_type)
 {
 	struct device *dev = acpi_desc->dev;
 	int scheduled = 0, busy = 0;
@@ -3354,14 +3380,10 @@ int acpi_nfit_ars_rescan(struct acpi_nfit_desc *acpi_desc, unsigned long flags)
 		if (test_bit(ARS_FAILED, &nfit_spa->ars_state))
 			continue;
 
-		if (test_and_set_bit(ARS_REQ, &nfit_spa->ars_state)) {
+		if (test_and_set_bit(req_type, &nfit_spa->ars_state))
 			busy++;
-			set_bit(ARS_REQ_REDO, &nfit_spa->ars_state);
-		} else {
-			if (test_bit(ARS_SHORT, &flags))
-				set_bit(ARS_SHORT, &nfit_spa->ars_state);
+		else
 			scheduled++;
-		}
 	}
 	if (scheduled) {
 		sched_ars(acpi_desc);
@@ -3547,10 +3569,11 @@ static void acpi_nfit_update_notify(struct device *dev, acpi_handle handle)
 static void acpi_nfit_uc_error_notify(struct device *dev, acpi_handle handle)
 {
 	struct acpi_nfit_desc *acpi_desc = dev_get_drvdata(dev);
-	unsigned long flags = (acpi_desc->scrub_mode == HW_ERROR_SCRUB_ON) ?
-			0 : 1 << ARS_SHORT;
 
-	acpi_nfit_ars_rescan(acpi_desc, flags);
+	if (acpi_desc->scrub_mode == HW_ERROR_SCRUB_ON)
+		acpi_nfit_ars_rescan(acpi_desc, ARS_REQ_LONG);
+	else
+		acpi_nfit_ars_rescan(acpi_desc, ARS_REQ_SHORT);
 }
 
 void __acpi_nfit_notify(struct device *dev, acpi_handle handle, u32 event)

drivers/acpi/nfit/nfit.h

@@ -118,10 +118,8 @@ enum nfit_dimm_notifiers {
 };
 
 enum nfit_ars_state {
-	ARS_REQ,
-	ARS_REQ_REDO,
-	ARS_DONE,
-	ARS_SHORT,
+	ARS_REQ_SHORT,
+	ARS_REQ_LONG,
 	ARS_FAILED,
 };
 
@@ -205,6 +203,7 @@ struct acpi_nfit_desc {
 	struct device *dev;
 	u8 ars_start_flags;
 	struct nd_cmd_ars_status *ars_status;
+	struct nfit_spa *scrub_spa;
 	struct delayed_work dwork;
 	struct list_head list;
 	struct kernfs_node *scrub_count_state;
@@ -259,7 +258,8 @@ struct nfit_blk {
 
 extern struct list_head acpi_descs;
 extern struct mutex acpi_desc_lock;
-int acpi_nfit_ars_rescan(struct acpi_nfit_desc *acpi_desc, unsigned long flags);
+int acpi_nfit_ars_rescan(struct acpi_nfit_desc *acpi_desc,
+		enum nfit_ars_state req_type);
 
 #ifdef CONFIG_X86_MCE
 void nfit_mce_register(void);