4 files changed, 66 insertions, 7 deletions

diff --git a/drivers/s390/scsi/zfcp_ext.h b/drivers/s390/scsi/zfcp_ext.h
index c6acca521ffe..31e8a7240fd7 100644
--- a/drivers/s390/scsi/zfcp_ext.h
+++ b/drivers/s390/scsi/zfcp_ext.h
@@ -167,6 +167,7 @@ extern const struct attribute_group *zfcp_port_attr_groups[];
 extern struct mutex zfcp_sysfs_port_units_mutex;
 extern struct device_attribute *zfcp_sysfs_sdev_attrs[];
 extern struct device_attribute *zfcp_sysfs_shost_attrs[];
+bool zfcp_sysfs_port_is_removing(const struct zfcp_port *const port);
 
 /* zfcp_unit.c */
 extern int zfcp_unit_add(struct zfcp_port *, u64);
diff --git a/drivers/s390/scsi/zfcp_scsi.c b/drivers/s390/scsi/zfcp_scsi.c
index 221d0dfb8493..e9ded2befa0d 100644
--- a/drivers/s390/scsi/zfcp_scsi.c
+++ b/drivers/s390/scsi/zfcp_scsi.c
@@ -129,6 +129,15 @@ static int zfcp_scsi_slave_alloc(struct scsi_device *sdev)
 
 	zfcp_sdev->erp_action.port = port;
 
+	mutex_lock(&zfcp_sysfs_port_units_mutex);
+	if (zfcp_sysfs_port_is_removing(port)) {
+		/* port is already gone */
+		mutex_unlock(&zfcp_sysfs_port_units_mutex);
+		put_device(&port->dev); /* undo zfcp_get_port_by_wwpn() */
+		return -ENXIO;
+	}
+	mutex_unlock(&zfcp_sysfs_port_units_mutex);
+
 	unit = zfcp_unit_find(port, zfcp_scsi_dev_lun(sdev));
 	if (unit)
 		put_device(&unit->dev);
diff --git a/drivers/s390/scsi/zfcp_sysfs.c b/drivers/s390/scsi/zfcp_sysfs.c
index b277be6f7611..af197e2b3e69 100644
--- a/drivers/s390/scsi/zfcp_sysfs.c
+++ b/drivers/s390/scsi/zfcp_sysfs.c
@@ -235,6 +235,53 @@ static ZFCP_DEV_ATTR(adapter, port_rescan, S_IWUSR, NULL,
 
 DEFINE_MUTEX(zfcp_sysfs_port_units_mutex);
 
+static void zfcp_sysfs_port_set_removing(struct zfcp_port *const port)
+{
+	lockdep_assert_held(&zfcp_sysfs_port_units_mutex);
+	atomic_set(&port->units, -1);
+}
+
+bool zfcp_sysfs_port_is_removing(const struct zfcp_port *const port)
+{
+	lockdep_assert_held(&zfcp_sysfs_port_units_mutex);
+	return atomic_read(&port->units) == -1;
+}
+
+static bool zfcp_sysfs_port_in_use(struct zfcp_port *const port)
+{
+	struct zfcp_adapter *const adapter = port->adapter;
+	unsigned long flags;
+	struct scsi_device *sdev;
+	bool in_use = true;
+
+	mutex_lock(&zfcp_sysfs_port_units_mutex);
+	if (atomic_read(&port->units) > 0)
+		goto unlock_port_units_mutex; /* zfcp_unit(s) under port */
+
+	spin_lock_irqsave(adapter->scsi_host->host_lock, flags);
+	__shost_for_each_device(sdev, adapter->scsi_host) {
+		const struct zfcp_scsi_dev *zsdev = sdev_to_zfcp(sdev);
+
+		if (sdev->sdev_state == SDEV_DEL ||
+		    sdev->sdev_state == SDEV_CANCEL)
+			continue;
+		if (zsdev->port != port)
+			continue;
+		/* alive scsi_device under port of interest */
+		goto unlock_host_lock;
+	}
+
+	/* port is about to be removed, so no more unit_add or slave_alloc */
+	zfcp_sysfs_port_set_removing(port);
+	in_use = false;
+
+unlock_host_lock:
+	spin_unlock_irqrestore(adapter->scsi_host->host_lock, flags);
+unlock_port_units_mutex:
+	mutex_unlock(&zfcp_sysfs_port_units_mutex);
+	return in_use;
+}
+
 static ssize_t zfcp_sysfs_port_remove_store(struct device *dev,
 					    struct device_attribute *attr,
 					    const char *buf, size_t count)
@@ -257,15 +304,11 @@ static ssize_t zfcp_sysfs_port_remove_store(struct device *dev,
 	else
 		retval = 0;
 
-	mutex_lock(&zfcp_sysfs_port_units_mutex);
-	if (atomic_read(&port->units) > 0) {
+	if (zfcp_sysfs_port_in_use(port)) {
 		retval = -EBUSY;
-		mutex_unlock(&zfcp_sysfs_port_units_mutex);
+		put_device(&port->dev); /* undo zfcp_get_port_by_wwpn() */
 		goto out;
 	}
-	/* port is about to be removed, so no more unit_add */
-	atomic_set(&port->units, -1);
-	mutex_unlock(&zfcp_sysfs_port_units_mutex);
 
 	write_lock_irq(&adapter->port_list_lock);
 	list_del(&port->list);
diff --git a/drivers/s390/scsi/zfcp_unit.c b/drivers/s390/scsi/zfcp_unit.c
index 1bf0a0984a09..e67bf7388cae 100644
--- a/drivers/s390/scsi/zfcp_unit.c
+++ b/drivers/s390/scsi/zfcp_unit.c
@@ -124,7 +124,7 @@ int zfcp_unit_add(struct zfcp_port *port, u64 fcp_lun)
 	int retval = 0;
 
 	mutex_lock(&zfcp_sysfs_port_units_mutex);
-	if (atomic_read(&port->units) == -1) {
+	if (zfcp_sysfs_port_is_removing(port)) {
 		/* port is already gone */
 		retval = -ENODEV;
 		goto out;
@@ -168,8 +168,14 @@ int zfcp_unit_add(struct zfcp_port *port, u64 fcp_lun)
 	write_lock_irq(&port->unit_list_lock);
 	list_add_tail(&unit->list, &port->unit_list);
 	write_unlock_irq(&port->unit_list_lock);
+	/*
+	 * lock order: shost->scan_mutex before zfcp_sysfs_port_units_mutex
+	 * due to      zfcp_unit_scsi_scan() => zfcp_scsi_slave_alloc()
+	 */
+	mutex_unlock(&zfcp_sysfs_port_units_mutex);
 
 	zfcp_unit_scsi_scan(unit);
+	return retval;
 
 out:
 	mutex_unlock(&zfcp_sysfs_port_units_mutex);