[PATCH v3 2/7] ata: libata-scsi: convert dev->sdev to per-LUN array

[Phil Pemberton <philpem@philpem.me.uk>]

Multi-LUN ATAPI devices (PD/CD combos, CD changers) share a single
ata_device but expose multiple scsi_devices.  The previous single
dev->sdev pointer could only track one LUN, making all other LUNs
invisible to code that operates on sdevs: port detach, suspend/resume,
ACPI uevent, ZPODD, media change notification, and EH teardown.

Replace the scalar struct scsi_device *sdev with a fixed-size array
dev->sdev[ATAPI_MAX_LUN] indexed by LUN number, where ATAPI_MAX_LUN
is 8 (the SCSI-2 ceiling, LUN values 0..7).

Key changes per call site:
  - ata_scsi_dev_config:  assign sdev to dev->sdev[sdev->lun]
  - ata_scsi_sdev_destroy: clear dev->sdev[sdev->lun]; only trigger
    ATA-level detach when LUN 0 is destroyed, since removing a higher
    LUN should not tear down the underlying ATA device
  - ata_port_detach:  iterate all LUN slots (high→low)
  - ata_scsi_offline_dev:  iterate all LUN slots
  - ata_scsi_remove_dev:  snapshot and remove all LUN slots, then
    scsi_remove_device each one outside the lock
  - ata_scsi_media_change_notify:  send event to all populated LUNs
  - ata_scsi_dev_rescan:  resume and rescan each populated LUN
  - ACPI, ZPODD, ofnode, door-lock:  use dev->sdev[0] (LUN 0 remains
    canonical for ATA-level operations)
  - ata_scsi_scan_host:  uses dev->sdev[0] for the existing LUN-0
    add/retry path

For single-LUN devices (the vast majority), only dev->sdev[0] is ever
populated and the additional slots remain NULL.

Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Phil Pemberton <philpem@philpem.me.uk>
---
 drivers/ata/libata-acpi.c  |   4 +-
 drivers/ata/libata-core.c  |  10 ++-
 drivers/ata/libata-scsi.c  | 146 ++++++++++++++++++-------------------
 drivers/ata/libata-zpodd.c |   6 +-
 include/linux/libata.h     |   2 +-
 5 files changed, 86 insertions(+), 82 deletions(-)

diff --git a/drivers/ata/libata-acpi.c b/drivers/ata/libata-acpi.c
index 4433f626246b..d07237f66d98 100644
--- a/drivers/ata/libata-acpi.c
+++ b/drivers/ata/libata-acpi.c
@@ -153,8 +153,8 @@ static void ata_acpi_uevent(struct ata_port *ap, struct ata_device *dev,
 	char *envp[] = { event_string, NULL };
 
 	if (dev) {
-		if (dev->sdev)
-			kobj = &dev->sdev->sdev_gendev.kobj;
+		if (dev->sdev[0])
+			kobj = &dev->sdev[0]->sdev_gendev.kobj;
 	} else
 		kobj = &ap->dev->kobj;
 
diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index 8c279b6eb1fb..f24d38f6ee73 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -6270,11 +6270,15 @@ static void ata_port_detach(struct ata_port *ap)
 	/* Remove scsi devices */
 	ata_for_each_link(link, ap, HOST_FIRST) {
 		ata_for_each_dev(dev, link, ALL) {
-			if (dev->sdev) {
+			int lun;
+
+			for (lun = ATAPI_MAX_LUN - 1; lun >= 0; lun--) {
+				if (!dev->sdev[lun])
+					continue;
 				spin_unlock_irqrestore(ap->lock, flags);
-				scsi_remove_device(dev->sdev);
+				scsi_remove_device(dev->sdev[lun]);
 				spin_lock_irqsave(ap->lock, flags);
-				dev->sdev = NULL;
+				dev->sdev[lun] = NULL;
 			}
 		}
 	}
diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
index d1665305b552..317883bac25f 100644
--- a/drivers/ata/libata-scsi.c
+++ b/drivers/ata/libata-scsi.c
@@ -1131,7 +1131,7 @@ int ata_scsi_dev_config(struct scsi_device *sdev, struct queue_limits *lim,
 	if (dev->flags & ATA_DFLAG_TRUSTED)
 		sdev->security_supported = 1;
 
-	dev->sdev = sdev;
+	dev->sdev[sdev->lun] = sdev;
 	return 0;
 }
 
@@ -1202,10 +1202,10 @@ EXPORT_SYMBOL_GPL(ata_scsi_sdev_configure);
  *
  *	@sdev is about to be destroyed for hot/warm unplugging.  If
  *	this unplugging was initiated by libata as indicated by NULL
- *	dev->sdev, this function doesn't have to do anything.
+ *	dev->sdev[], this function doesn't have to do anything.
  *	Otherwise, SCSI layer initiated warm-unplug is in progress.
- *	Clear dev->sdev, schedule the device for ATA detach and invoke
- *	EH.
+ *	Clear the per-LUN slot; when the last LUN (LUN 0) is destroyed,
+ *	schedule ATA-level detach via EH.
  *
  *	LOCKING:
  *	Defined by SCSI layer.  We don't really care.
@@ -1220,11 +1220,12 @@ void ata_scsi_sdev_destroy(struct scsi_device *sdev)
 
 	spin_lock_irqsave(ap->lock, flags);
 	dev = __ata_scsi_find_dev(ap, sdev);
-	if (dev && dev->sdev) {
-		/* SCSI device already in CANCEL state, no need to offline it */
-		dev->sdev = NULL;
-		dev->flags |= ATA_DFLAG_DETACH;
-		ata_port_schedule_eh(ap);
+	if (dev && dev->sdev[sdev->lun] == sdev) {
+		dev->sdev[sdev->lun] = NULL;
+		if (sdev->lun == 0) {
+			dev->flags |= ATA_DFLAG_DETACH;
+			ata_port_schedule_eh(ap);
+		}
 	}
 	spin_unlock_irqrestore(ap->lock, flags);
 
@@ -2912,10 +2913,10 @@ static void atapi_qc_complete(struct ata_queued_cmd *qc)
 		 * avoid this infinite loop.
 		 *
 		 * This may happen before SCSI scan is complete.  Make
-		 * sure qc->dev->sdev isn't NULL before dereferencing.
+		 * sure qc->dev->sdev[0] isn't NULL before dereferencing.
 		 */
-		if (qc->cdb[0] == ALLOW_MEDIUM_REMOVAL && qc->dev->sdev)
-			qc->dev->sdev->locked = 0;
+		if (qc->cdb[0] == ALLOW_MEDIUM_REMOVAL && qc->dev->sdev[0])
+			qc->dev->sdev[0]->locked = 0;
 
 		qc->scsicmd->result = SAM_STAT_CHECK_CONDITION;
 		ata_qc_done(qc);
@@ -4651,7 +4652,7 @@ int ata_scsi_add_hosts(struct ata_host *host, const struct scsi_host_template *s
 #ifdef CONFIG_OF
 static void ata_scsi_assign_ofnode(struct ata_device *dev, struct ata_port *ap)
 {
-	struct scsi_device *sdev = dev->sdev;
+	struct scsi_device *sdev = dev->sdev[0];
 	struct device *d = ap->host->dev;
 	struct device_node *np = d->of_node;
 	struct device_node *child;
@@ -4689,7 +4690,7 @@ void ata_scsi_scan_host(struct ata_port *ap, int sync)
 			struct scsi_device *sdev;
 			int channel = 0, id = 0;
 
-			if (dev->sdev)
+			if (dev->sdev[0])
 				continue;
 
 			if (ata_is_host_link(link))
@@ -4700,11 +4701,11 @@ void ata_scsi_scan_host(struct ata_port *ap, int sync)
 			sdev = __scsi_add_device(ap->scsi_host, channel, id, 0,
 						 NULL);
 			if (!IS_ERR(sdev)) {
-				dev->sdev = sdev;
+				dev->sdev[0] = sdev;
 				ata_scsi_assign_ofnode(dev, ap);
 				scsi_device_put(sdev);
 			} else {
-				dev->sdev = NULL;
+				dev->sdev[0] = NULL;
 			}
 		}
 	}
@@ -4715,7 +4716,7 @@ void ata_scsi_scan_host(struct ata_port *ap, int sync)
 	 */
 	ata_for_each_link(link, ap, EDGE) {
 		ata_for_each_dev(dev, link, ENABLED) {
-			if (!dev->sdev)
+			if (!dev->sdev[0])
 				goto exit_loop;
 		}
 	}
@@ -4756,7 +4757,7 @@ void ata_scsi_scan_host(struct ata_port *ap, int sync)
  *
  *	This function is called from ata_eh_detach_dev() and is responsible for
  *	taking the SCSI device attached to @dev offline.  This function is
- *	called with host lock which protects dev->sdev against clearing.
+ *	called with host lock which protects dev->sdev[] against clearing.
  *
  *	LOCKING:
  *	spin_lock_irqsave(host lock)
@@ -4766,11 +4767,16 @@ void ata_scsi_scan_host(struct ata_port *ap, int sync)
  */
 bool ata_scsi_offline_dev(struct ata_device *dev)
 {
-	if (dev->sdev) {
-		scsi_device_set_state(dev->sdev, SDEV_OFFLINE);
-		return true;
+	bool found = false;
+	int lun;
+
+	for (lun = ATAPI_MAX_LUN - 1; lun >= 0; lun--) {
+		if (dev->sdev[lun]) {
+			scsi_device_set_state(dev->sdev[lun], SDEV_OFFLINE);
+			found = true;
+		}
 	}
-	return false;
+	return found;
 }
 
 /**
@@ -4786,49 +4792,38 @@ bool ata_scsi_offline_dev(struct ata_device *dev)
 static void ata_scsi_remove_dev(struct ata_device *dev)
 {
 	struct ata_port *ap = dev->link->ap;
-	struct scsi_device *sdev;
+	struct scsi_device *sdevs[ATAPI_MAX_LUN] = {};
 	unsigned long flags;
+	int lun;
 
-	/* Alas, we need to grab scan_mutex to ensure SCSI device
-	 * state doesn't change underneath us and thus
-	 * scsi_device_get() always succeeds.  The mutex locking can
-	 * be removed if there is __scsi_device_get() interface which
-	 * increments reference counts regardless of device state.
-	 */
 	mutex_lock(&ap->scsi_host->scan_mutex);
 	spin_lock_irqsave(ap->lock, flags);
 
-	/* clearing dev->sdev is protected by host lock */
-	sdev = dev->sdev;
-	dev->sdev = NULL;
+	for (lun = ATAPI_MAX_LUN - 1; lun >= 0; lun--) {
+		struct scsi_device *sdev = dev->sdev[lun];
+
+		dev->sdev[lun] = NULL;
+		if (!sdev)
+			continue;
 
-	if (sdev) {
-		/* If user initiated unplug races with us, sdev can go
-		 * away underneath us after the host lock and
-		 * scan_mutex are released.  Hold onto it.
-		 */
 		if (scsi_device_get(sdev) == 0) {
-			/* The following ensures the attached sdev is
-			 * offline on return from ata_scsi_offline_dev()
-			 * regardless it wins or loses the race
-			 * against this function.
-			 */
 			scsi_device_set_state(sdev, SDEV_OFFLINE);
+			sdevs[lun] = sdev;
 		} else {
 			WARN_ON(1);
-			sdev = NULL;
 		}
 	}
 
 	spin_unlock_irqrestore(ap->lock, flags);
 	mutex_unlock(&ap->scsi_host->scan_mutex);
 
-	if (sdev) {
+	for (lun = ATAPI_MAX_LUN - 1; lun >= 0; lun--) {
+		if (!sdevs[lun])
+			continue;
 		ata_dev_info(dev, "detaching (SCSI %s)\n",
-			     dev_name(&sdev->sdev_gendev));
-
-		scsi_remove_device(sdev);
-		scsi_device_put(sdev);
+			     dev_name(&sdevs[lun]->sdev_gendev));
+		scsi_remove_device(sdevs[lun]);
+		scsi_device_put(sdevs[lun]);
 	}
 }
 
@@ -4865,9 +4860,12 @@ static void ata_scsi_handle_link_detach(struct ata_link *link)
  */
 void ata_scsi_media_change_notify(struct ata_device *dev)
 {
-	if (dev->sdev)
-		sdev_evt_send_simple(dev->sdev, SDEV_EVT_MEDIA_CHANGE,
-				     GFP_ATOMIC);
+	int lun;
+
+	for (lun = 0; lun < ATAPI_MAX_LUN; lun++)
+		if (dev->sdev[lun])
+			sdev_evt_send_simple(dev->sdev[lun],
+					     SDEV_EVT_MEDIA_CHANGE, GFP_ATOMIC);
 }
 
 /**
@@ -5000,37 +4998,39 @@ void ata_scsi_dev_rescan(struct work_struct *work)
 
 	ata_for_each_link(link, ap, EDGE) {
 		ata_for_each_dev(dev, link, ENABLED) {
-			struct scsi_device *sdev = dev->sdev;
+			int lun;
 
-			/*
-			 * If the port was suspended before this was scheduled,
-			 * bail out.
-			 */
 			if (ap->pflags & ATA_PFLAG_SUSPENDED)
 				goto unlock_ap;
 
-			if (!sdev)
-				continue;
-			if (scsi_device_get(sdev))
-				continue;
-
 			do_resume = dev->flags & ATA_DFLAG_RESUMING;
 
-			spin_unlock_irqrestore(ap->lock, flags);
-			if (do_resume) {
-				ret = scsi_resume_device(sdev);
-				if (ret == -EWOULDBLOCK) {
-					scsi_device_put(sdev);
-					goto unlock_scan;
+			for (lun = 0; lun < ATAPI_MAX_LUN; lun++) {
+				struct scsi_device *sdev = dev->sdev[lun];
+
+				if (!sdev)
+					continue;
+				if (scsi_device_get(sdev))
+					continue;
+
+				spin_unlock_irqrestore(ap->lock, flags);
+				if (do_resume) {
+					ret = scsi_resume_device(sdev);
+					if (ret == -EWOULDBLOCK) {
+						scsi_device_put(sdev);
+						goto unlock_scan;
+					}
 				}
-				dev->flags &= ~ATA_DFLAG_RESUMING;
+				ret = scsi_rescan_device(sdev);
+				scsi_device_put(sdev);
+				spin_lock_irqsave(ap->lock, flags);
+
+				if (ret)
+					goto unlock_ap;
 			}
-			ret = scsi_rescan_device(sdev);
-			scsi_device_put(sdev);
-			spin_lock_irqsave(ap->lock, flags);
 
-			if (ret)
-				goto unlock_ap;
+			if (do_resume)
+				dev->flags &= ~ATA_DFLAG_RESUMING;
 		}
 	}
 
diff --git a/drivers/ata/libata-zpodd.c b/drivers/ata/libata-zpodd.c
index 414e7c63bd85..116dd42f8232 100644
--- a/drivers/ata/libata-zpodd.c
+++ b/drivers/ata/libata-zpodd.c
@@ -185,7 +185,7 @@ void zpodd_enable_run_wake(struct ata_device *dev)
 {
 	struct zpodd *zpodd = dev->zpodd;
 
-	sdev_disable_disk_events(dev->sdev);
+	sdev_disable_disk_events(dev->sdev[0]);
 
 	zpodd->powered_off = true;
 	acpi_pm_set_device_wakeup(&dev->tdev, true);
@@ -233,14 +233,14 @@ void zpodd_post_poweron(struct ata_device *dev)
 	zpodd->zp_sampled = false;
 	zpodd->zp_ready = false;
 
-	sdev_enable_disk_events(dev->sdev);
+	sdev_enable_disk_events(dev->sdev[0]);
 }
 
 static void zpodd_wake_dev(acpi_handle handle, u32 event, void *context)
 {
 	struct ata_device *ata_dev = context;
 	struct zpodd *zpodd = ata_dev->zpodd;
-	struct device *dev = &ata_dev->sdev->sdev_gendev;
+	struct device *dev = &ata_dev->sdev[0]->sdev_gendev;
 
 	if (event == ACPI_NOTIFY_DEVICE_WAKE && pm_runtime_suspended(dev)) {
 		zpodd->from_notify = true;
diff --git a/include/linux/libata.h b/include/linux/libata.h
index 27b11577826e..e2e759d492c7 100644
--- a/include/linux/libata.h
+++ b/include/linux/libata.h
@@ -722,7 +722,7 @@ struct ata_device {
 	unsigned int		devno;		/* 0 or 1 */
 	u64			quirks;		/* List of broken features */
 	unsigned long		flags;		/* ATA_DFLAG_xxx */
-	struct scsi_device	*sdev;		/* attached SCSI device */
+	struct scsi_device	*sdev[ATAPI_MAX_LUN];	/* per-LUN SCSI devices */
 	void			*private_data;
 #ifdef CONFIG_ATA_ACPI
 	union acpi_object	*gtf_cache;
-- 
2.43.0