[PATCH] add per scsi-host workqueues for defered processing

Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>

drivers/scsi/hosts.c

@@ -129,6 +129,15 @@ int scsi_add_host(struct Scsi_Host *shost, struct device *dev)
 					 GFP_KERNEL)) == NULL)
 		goto out_del_classdev;
 
+	if (shost->transportt->create_work_queue) {
+		snprintf(shost->work_q_name, KOBJ_NAME_LEN, "scsi_wq_%d",
+			shost->host_no);
+		shost->work_q = create_singlethread_workqueue(
+					shost->work_q_name);
+		if (!shost->work_q)
+			goto out_free_shost_data;
+	}
+
 	error = scsi_sysfs_add_host(shost);
 	if (error)
 		goto out_destroy_host;
@@ -137,6 +146,10 @@ int scsi_add_host(struct Scsi_Host *shost, struct device *dev)
 	return error;
 
  out_destroy_host:
+	if (shost->work_q)
+		destroy_workqueue(shost->work_q);
+ out_free_shost_data:
+	kfree(shost->shost_data);
  out_del_classdev:
 	class_device_del(&shost->shost_classdev);
  out_del_gendev:
@@ -160,6 +173,9 @@ static void scsi_host_dev_release(struct device *dev)
 		shost->eh_notify = NULL;
 	}
 
+	if (shost->work_q)
+		destroy_workqueue(shost->work_q);
+
 	scsi_proc_hostdir_rm(shost->hostt);
 	scsi_destroy_command_freelist(shost);
 	kfree(shost->shost_data);
@@ -403,3 +419,27 @@ int scsi_is_host_device(const struct device *dev)
 	return dev->release == scsi_host_dev_release;
 }
 EXPORT_SYMBOL(scsi_is_host_device);
+
+/**
+ * scsi_queue_work - Queue work to the Scsi_Host workqueue.
+ * @shost:	Pointer to Scsi_Host.
+ * @work:	Work to queue for execution.
+ *
+ * Return value:
+ * 	0 on success / != 0 for error
+ **/
+int scsi_queue_work(struct Scsi_Host *shost, struct work_struct *work)
+{
+	if (unlikely(!shost->work_q)) {
+		printk(KERN_ERR
+			"ERROR: Scsi host '%s' attempted to queue scsi-work, "
+			"when no workqueue created.\n", shost->hostt->name);
+		dump_stack();
+
+		return -EINVAL;
+	}
+
+	return queue_work(shost->work_q, work);
+}
+EXPORT_SYMBOL_GPL(scsi_queue_work);
+

include/scsi/scsi_host.h

@@ -4,6 +4,7 @@
 #include <linux/device.h>
 #include <linux/list.h>
 #include <linux/types.h>
+#include <linux/workqueue.h>
 
 struct block_device;
 struct module;
@@ -519,6 +520,12 @@ struct Scsi_Host {
 	unsigned ordered_flush:1;
 	unsigned ordered_tag:1;
 
+	/*
+	 * Optional work queue to be utilized by the transport
+	 */
+	char work_q_name[KOBJ_NAME_LEN];
+	struct workqueue_struct *work_q;
+
 	/*
 	 * Host has rejected a command because it was busy.
 	 */
@@ -582,6 +589,8 @@ static inline struct Scsi_Host *dev_to_shost(struct device *dev)
 	return container_of(dev, struct Scsi_Host, shost_gendev);
 }
 
+extern int scsi_queue_work(struct Scsi_Host *, struct work_struct *);
+
 extern struct Scsi_Host *scsi_host_alloc(struct scsi_host_template *, int);
 extern int __must_check scsi_add_host(struct Scsi_Host *, struct device *);
 extern void scsi_scan_host(struct Scsi_Host *);

include/scsi/scsi_transport.h

@@ -34,6 +34,11 @@ struct scsi_transport_template {
 	int	device_size;
 	int	target_size;
 	int	host_size;
+
+	/*
+	 * True if the transport wants to use a host-based work-queue
+	 */
+	unsigned int create_work_queue : 1;
 };
 
 #define transport_class_to_shost(tc) \