ata fixes for 7.1-rc5

- Make sure that the issuing of a deferred non-NCQ command via
    workqueue feature is only used when mixing NCQ and non-NCQ commands
    to the same link (i.e. return value ATA_DEFER_LINK), and nothing
    else. This way we will not incorrectly try to use the feature for
    e.g. PATA drivers.
 
  - The deferred non-NCQ command was stored in a per-port struct.
    When using Port Multipliers with FIS-Based Switching, we would thus
    needlessly defer commands to all other links. Store the deferred QC
    in a per-link struct, such that Port Multipliers with FBS will get
    the same performance as before.
 
  - The issuing of a deferred non-NCQ command via workqueue feature
    broke support for Port Multipliers using Command-Based Switching.
    The issuing of a deferred non-NCQ command via workqueue feature is
    not compatible with the use of ap->excl_link, which PMPs with CBS
    use for fairness (using implicit round robin).
 -----BEGIN PGP SIGNATURE-----
 
 iHUEABYKAB0WIQRN+ES/c4tHlMch3DzJZDGjmcZNcgUCagyJuQAKCRDJZDGjmcZN
 clYrAP9WGyaktaHe8MVLFAOIvtj58qAyDGH5U9gqA/lc8MfFDQEAvC81OBtXkpP6
 WaZGuAw6eqja1KlSg6mzmfOLvVIHLwk=
 =MbtN
 -----END PGP SIGNATURE-----

Merge tag 'ata-7.1-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/libata/linux

Pull ata fixes from Niklas Cassel:

 - Make sure that the issuing of a deferred non-NCQ command via
   workqueue feature is only used when mixing NCQ and non-NCQ commands
   to the same link (i.e. return value ATA_DEFER_LINK), and nothing
   else. This way we will not incorrectly try to use the feature for
   e.g. PATA drivers

 - The deferred non-NCQ command was stored in a per-port struct. When
   using Port Multipliers with FIS-Based Switching, we would thus
   needlessly defer commands to all other links. Store the deferred QC
   in a per-link struct, such that Port Multipliers with FBS will get
   the same performance as before

 - The issuing of a deferred non-NCQ command via workqueue feature broke
   support for Port Multipliers using Command-Based Switching. The
   issuing of a deferred non-NCQ command via workqueue feature is not
   compatible with the use of ap->excl_link, which PMPs with CBS use for
   fairness (using implicit round robin)

* tag 'ata-7.1-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/libata/linux:
  ata: libata-scsi: do not needlessly defer commands when using PMP with FBS
  ata: libata-scsi: do not use the deferred QC feature on PMPs with CBS
  ata: libata-scsi: do not use the deferred QC feature for ATA_DEFER_PORT
  ata: libata-scsi: improve readability of ata_scsi_qc_issue()

drivers/ata/libata-core.c

@@ -5584,6 +5584,7 @@ void ata_link_init(struct ata_port *ap, struct ata_link *link, int pmp)
 	link->pmp = pmp;
 	link->active_tag = ATA_TAG_POISON;
 	link->hw_sata_spd_limit = UINT_MAX;
+	INIT_WORK(&link->deferred_qc_work, ata_scsi_deferred_qc_work);
 
 	/* can't use iterator, ap isn't initialized yet */
 	for (i = 0; i < ATA_MAX_DEVICES; i++) {
@@ -5666,7 +5667,6 @@ struct ata_port *ata_port_alloc(struct ata_host *host)
 	mutex_init(&ap->scsi_scan_mutex);
 	INIT_DELAYED_WORK(&ap->hotplug_task, ata_scsi_hotplug);
 	INIT_DELAYED_WORK(&ap->scsi_rescan_task, ata_scsi_dev_rescan);
-	INIT_WORK(&ap->deferred_qc_work, ata_scsi_deferred_qc_work);
 	INIT_LIST_HEAD(&ap->eh_done_q);
 	init_waitqueue_head(&ap->eh_wait_q);
 	init_completion(&ap->park_req_pending);
@@ -6291,12 +6291,15 @@ static void ata_port_detach(struct ata_port *ap)
 
 	/* It better be dead now and not have any remaining deferred qc. */
 	WARN_ON(!(ap->pflags & ATA_PFLAG_UNLOADED));
-	WARN_ON(ap->deferred_qc);
 
-	cancel_work_sync(&ap->deferred_qc_work);
 	cancel_delayed_work_sync(&ap->hotplug_task);
 	cancel_delayed_work_sync(&ap->scsi_rescan_task);
 
+	ata_for_each_link(link, ap, PMP_FIRST) {
+		WARN_ON(link->deferred_qc);
+		cancel_work_sync(&link->deferred_qc_work);
+	}
+
 	/* Delete port multiplier link transport devices */
 	if (ap->pmp_link) {
 		int i;

drivers/ata/libata-eh.c

@@ -651,11 +651,11 @@ int ata_scsi_cmd_error_handler(struct Scsi_Host *host, struct ata_port *ap,
 			if (qc->scsicmd != scmd)
 				continue;
 			if ((qc->flags & ATA_QCFLAG_ACTIVE) ||
-			    qc == ap->deferred_qc)
+			    qc == qc->dev->link->deferred_qc)
 				break;
 		}
 
-		if (i < ATA_MAX_QUEUE && qc == ap->deferred_qc) {
+		if (i < ATA_MAX_QUEUE && qc == qc->dev->link->deferred_qc) {
 			/*
 			 * This is a deferred command that timed out while
 			 * waiting for the command queue to drain. Since the qc
@@ -666,8 +666,8 @@ int ata_scsi_cmd_error_handler(struct Scsi_Host *host, struct ata_port *ap,
 			 * deferred qc work from issuing this qc.
 			 */
 			WARN_ON_ONCE(qc->flags & ATA_QCFLAG_ACTIVE);
-			ap->deferred_qc = NULL;
-			cancel_work(&ap->deferred_qc_work);
+			qc->dev->link->deferred_qc = NULL;
+			cancel_work(&qc->dev->link->deferred_qc_work);
 			set_host_byte(scmd, DID_TIME_OUT);
 			scsi_eh_finish_cmd(scmd, &ap->eh_done_q);
 		} else if (i < ATA_MAX_QUEUE) {

drivers/ata/libata-pmp.c

@@ -110,13 +110,24 @@ int sata_pmp_qc_defer_cmd_switch(struct ata_queued_cmd *qc)
 {
 	struct ata_link *link = qc->dev->link;
 	struct ata_port *ap = link->ap;
+	int ret;
 
 	if (ap->excl_link == NULL || ap->excl_link == link) {
 		if (ap->nr_active_links == 0 || ata_link_active(link)) {
 			qc->flags |= ATA_QCFLAG_CLEAR_EXCL;
-			return ata_std_qc_defer(qc);
+			ret = ata_std_qc_defer(qc);
+			if (ret == ATA_DEFER_LINK)
+				return ATA_DEFER_LINK_EXCL;
+			return ret;
 		}
 
+		/*
+		 * Note: ap->excl_link contains the link that is next in line,
+		 * i.e. implicit round robin. If there is only one link
+		 * dispatching, ap->excl_link will be left unclaimed, allowing
+		 * other links to set ap->excl_link, ensuring that the currently
+		 * active link cannot queue any more.
+		 */
 		ap->excl_link = link;
 	}
 
@@ -571,8 +582,11 @@ static void sata_pmp_detach(struct ata_device *dev)
 	if (ap->ops->pmp_detach)
 		ap->ops->pmp_detach(ap);
 
-	ata_for_each_link(tlink, ap, EDGE)
+	ata_for_each_link(tlink, ap, EDGE) {
+		WARN_ON(tlink->deferred_qc);
+		cancel_work_sync(&tlink->deferred_qc_work);
 		ata_eh_detach_dev(tlink->device);
+	}
 
 	spin_lock_irqsave(ap->lock, flags);
 	ap->nr_pmp_links = 0;

drivers/ata/libata-scsi.c

@@ -1664,8 +1664,9 @@ static void ata_scsi_qc_done(struct ata_queued_cmd *qc, bool set_result,
 
 void ata_scsi_deferred_qc_work(struct work_struct *work)
 {
-	struct ata_port *ap =
-		container_of(work, struct ata_port, deferred_qc_work);
+	struct ata_link *link =
+		container_of(work, struct ata_link, deferred_qc_work);
+	struct ata_port *ap = link->ap;
 	struct ata_queued_cmd *qc;
 	unsigned long flags;
 
@@ -1676,10 +1677,10 @@ void ata_scsi_deferred_qc_work(struct work_struct *work)
 	 * such case, we should not need any more deferring the qc, so warn if
 	 * qc_defer() says otherwise.
 	 */
-	qc = ap->deferred_qc;
+	qc = link->deferred_qc;
 	if (qc && !ata_port_eh_scheduled(ap)) {
 		WARN_ON_ONCE(ap->ops->qc_defer(qc));
-		ap->deferred_qc = NULL;
+		link->deferred_qc = NULL;
 		ata_qc_issue(qc);
 	}
 
@@ -1688,7 +1689,7 @@ void ata_scsi_deferred_qc_work(struct work_struct *work)
 
 void ata_scsi_requeue_deferred_qc(struct ata_port *ap)
 {
-	struct ata_queued_cmd *qc = ap->deferred_qc;
+	struct ata_link *link;
 
 	lockdep_assert_held(ap->lock);
 
@@ -1697,16 +1698,21 @@ void ata_scsi_requeue_deferred_qc(struct ata_port *ap)
 	 * do not try to be smart about what to do with this deferred command
 	 * and simply requeue it by completing it with DID_REQUEUE.
 	 */
-	if (qc) {
-		ap->deferred_qc = NULL;
-		cancel_work(&ap->deferred_qc_work);
-		ata_scsi_qc_done(qc, true, DID_REQUEUE << 16);
+	ata_for_each_link(link, ap, PMP_FIRST) {
+		struct ata_queued_cmd *qc = link->deferred_qc;
+
+		if (qc) {
+			link->deferred_qc = NULL;
+			cancel_work(&link->deferred_qc_work);
+			ata_scsi_qc_done(qc, true, DID_REQUEUE << 16);
+		}
 	}
 }
 
-static void ata_scsi_schedule_deferred_qc(struct ata_port *ap)
+static void ata_scsi_schedule_deferred_qc(struct ata_link *link)
 {
-	struct ata_queued_cmd *qc = ap->deferred_qc;
+	struct ata_queued_cmd *qc = link->deferred_qc;
+	struct ata_port *ap = link->ap;
 
 	lockdep_assert_held(ap->lock);
 
@@ -1723,12 +1729,12 @@ static void ata_scsi_schedule_deferred_qc(struct ata_port *ap)
 		return;
 	}
 	if (!ap->ops->qc_defer(qc))
-		queue_work(system_highpri_wq, &ap->deferred_qc_work);
+		queue_work(system_highpri_wq, &link->deferred_qc_work);
 }
 
 static void ata_scsi_qc_complete(struct ata_queued_cmd *qc)
 {
-	struct ata_port *ap = qc->ap;
+	struct ata_link *link = qc->dev->link;
 	struct scsi_cmnd *cmd = qc->scsicmd;
 	u8 *cdb = cmd->cmnd;
 	bool have_sense = qc->flags & ATA_QCFLAG_SENSE_VALID;
@@ -1759,22 +1765,23 @@ static void ata_scsi_qc_complete(struct ata_queued_cmd *qc)
 
 	ata_scsi_qc_done(qc, false, 0);
 
-	ata_scsi_schedule_deferred_qc(ap);
+	ata_scsi_schedule_deferred_qc(link);
 }
 
 static int ata_scsi_qc_issue(struct ata_port *ap, struct ata_queued_cmd *qc)
 {
+	struct ata_link *link = qc->dev->link;
 	int ret;
 
 	if (!ap->ops->qc_defer)
-		goto issue;
+		goto issue_qc;
 
 	/*
 	 * If we already have a deferred qc, then rely on the SCSI layer to
 	 * requeue and defer all incoming commands until the deferred qc is
 	 * processed, once all on-going commands complete.
 	 */
-	if (ap->deferred_qc) {
+	if (link->deferred_qc) {
 		ata_qc_free(qc);
 		return SCSI_MLQUEUE_DEVICE_BUSY;
 	}
@@ -1786,38 +1793,46 @@ static int ata_scsi_qc_issue(struct ata_port *ap, struct ata_queued_cmd *qc)
 		break;
 	case ATA_DEFER_LINK:
 		ret = SCSI_MLQUEUE_DEVICE_BUSY;
-		break;
+		goto defer_qc;
+	case ATA_DEFER_LINK_EXCL:
+		/*
+		 * Drivers making use of ap->excl_link cannot store the QC in
+		 * link->deferred_qc, because the ap->excl_link handling is
+		 * incompatible with the link->deferred_qc workqueue handling.
+		 */
+		ret = SCSI_MLQUEUE_DEVICE_BUSY;
+		goto free_qc;
 	case ATA_DEFER_PORT:
 		ret = SCSI_MLQUEUE_HOST_BUSY;
-		break;
+		goto free_qc;
 	default:
 		WARN_ON_ONCE(1);
 		ret = SCSI_MLQUEUE_HOST_BUSY;
-		break;
+		goto free_qc;
 	}
 
-	if (ret) {
-		/*
-		 * We must defer this qc: if this is not an NCQ command, keep
-		 * this qc as a deferred one and report to the SCSI layer that
-		 * we issued it so that it is not requeued. The deferred qc will
-		 * be issued with the port deferred_qc_work once all on-going
-		 * commands complete.
-		 */
-		if (!ata_is_ncq(qc->tf.protocol)) {
-			ap->deferred_qc = qc;
-			return 0;
-		}
-
-		/* Force a requeue of the command to defer its execution. */
-		ata_qc_free(qc);
-		return ret;
-	}
-
-issue:
+issue_qc:
 	ata_qc_issue(qc);
-
 	return 0;
+
+defer_qc:
+	/*
+	 * We must defer this qc: if this is not an NCQ command, keep
+	 * this qc as a deferred one and report to the SCSI layer that
+	 * we issued it so that it is not requeued. The deferred qc will
+	 * be issued with the port deferred_qc_work once all on-going
+	 * commands complete.
+	 */
+	if (!ata_is_ncq(qc->tf.protocol)) {
+		link->deferred_qc = qc;
+		return 0;
+	}
+
+free_qc:
+	/* Force a requeue of the command to defer its execution. */
+	ata_qc_free(qc);
+
+	return ret;
 }
 
 /**

drivers/ata/sata_sil24.c

@@ -789,6 +789,7 @@ static int sil24_qc_defer(struct ata_queued_cmd *qc)
 	struct ata_link *link = qc->dev->link;
 	struct ata_port *ap = link->ap;
 	u8 prot = qc->tf.protocol;
+	int ret;
 
 	/*
 	 * There is a bug in the chip:
@@ -826,7 +827,10 @@ static int sil24_qc_defer(struct ata_queued_cmd *qc)
 		qc->flags |= ATA_QCFLAG_CLEAR_EXCL;
 	}
 
-	return ata_std_qc_defer(qc);
+	ret = ata_std_qc_defer(qc);
+	if (ret == ATA_DEFER_LINK)
+		return ATA_DEFER_LINK_EXCL;
+	return ret;
 }
 
 static enum ata_completion_errors sil24_qc_prep(struct ata_queued_cmd *qc)

include/linux/libata.h

@@ -371,6 +371,7 @@ enum {
 	/* return values for ->qc_defer */
 	ATA_DEFER_LINK		= 1,
 	ATA_DEFER_PORT		= 2,
+	ATA_DEFER_LINK_EXCL	= 3,
 
 	/* desc_len for ata_eh_info and context */
 	ATA_EH_DESC_LEN		= 80,
@@ -854,6 +855,9 @@ struct ata_link {
 	unsigned int		sata_spd;	/* current SATA PHY speed */
 	enum ata_lpm_policy	lpm_policy;
 
+	struct work_struct	deferred_qc_work;
+	struct ata_queued_cmd	*deferred_qc;
+
 	/* record runtime error info, protected by host_set lock */
 	struct ata_eh_info	eh_info;
 	/* EH context */
@@ -899,9 +903,6 @@ struct ata_port {
 	u64			qc_active;
 	int			nr_active_links; /* #links with active qcs */
 
-	struct work_struct	deferred_qc_work;
-	struct ata_queued_cmd	*deferred_qc;
-
 	struct ata_link		link;		/* host default link */
 	struct ata_link		*slave_link;	/* see ata_slave_link_init() */