+ * scsi_prep_async_scan - prepare for an async scan
+ * @shost: the host which will be scanned
+ * Returns: a cookie to be passed to scsi_finish_async_scan()
+ *
+ * Tells the midlayer this host is going to do an asynchronous scan.
+ * It reserves the host's position in the scanning list and ensures
+ * that other asynchronous scans started after this one won't affect the
+ * ordering of the discovered devices.
+ */
+static struct async_scan_data *scsi_prep_async_scan(struct Scsi_Host *shost)
+{
+ struct async_scan_data *data;
+ unsigned long flags;
+
+ if (strncmp(scsi_scan_type, "sync", 4) == 0)
+ return NULL;
+
+ if (shost->async_scan) {
+ printk("%s called twice for host %d", __func__,
+ shost->host_no);
+ dump_stack();
+ return NULL;
+ }
+
+ data = kmalloc(sizeof(*data), GFP_KERNEL);
+ if (!data)
+ goto err;
+ data->shost = scsi_host_get(shost);
+ if (!data->shost)
+ goto err;
+ init_completion(&data->prev_finished);
+
+ mutex_lock(&shost->scan_mutex);
+ spin_lock_irqsave(shost->host_lock, flags);
+ shost->async_scan = 1;
+ spin_unlock_irqrestore(shost->host_lock, flags);
+ mutex_unlock(&shost->scan_mutex);
+
+ spin_lock(&async_scan_lock);
+ if (list_empty(&scanning_hosts))
+ complete(&data->prev_finished);
+ list_add_tail(&data->list, &scanning_hosts);
+ spin_unlock(&async_scan_lock);
+
+ return data;
+
+ err:
+ kfree(data);
+ return NULL;
+}
+
+/**
+ * scsi_finish_async_scan - asynchronous scan has finished
+ * @data: cookie returned from earlier call to scsi_prep_async_scan()
+ *
+ * All the devices currently attached to this host have been found.
+ * This function announces all the devices it has found to the rest
+ * of the system.
+ */
+static void scsi_finish_async_scan(struct async_scan_data *data)
+{
+ struct Scsi_Host *shost;
+ unsigned long flags;
+
+ if (!data)
+ return;
+
+ shost = data->shost;
+
+ mutex_lock(&shost->scan_mutex);
+
+ if (!shost->async_scan) {
+ printk("%s called twice for host %d", __func__,
+ shost->host_no);
+ dump_stack();
+ mutex_unlock(&shost->scan_mutex);
+ return;
+ }
+
+ wait_for_completion(&data->prev_finished);
+
+ scsi_sysfs_add_devices(shost);
+
+ spin_lock_irqsave(shost->host_lock, flags);
+ shost->async_scan = 0;
+ spin_unlock_irqrestore(shost->host_lock, flags);
+
+ mutex_unlock(&shost->scan_mutex);
+
+ spin_lock(&async_scan_lock);
+ list_del(&data->list);
+ if (!list_empty(&scanning_hosts)) {
+ struct async_scan_data *next = list_entry(scanning_hosts.next,
+ struct async_scan_data, list);
+ complete(&next->prev_finished);
+ }
+ spin_unlock(&async_scan_lock);
+
+ scsi_host_put(shost);
+ kfree(data);
+}
+
+static void do_scsi_scan_host(struct Scsi_Host *shost)