[PATCH] add back single_lun support

On Wed, Feb 05, 2003 at 05:14:00PM -0600, James Bottomley wrote:

> I don't see device_active getting set anywhere.
>
> shouldn't we just dump device_active in favour of a non-zero check of
> device_busy (it's all done under the queue lock, anyway).
>
> James

OK - once more.

This patch against the current scsi-misc-2.5 adds back the check for the
single_lun case and removes the unused device_active field.

I compiled and booted with this applied but don't have any devices (i.e.
CD ROM changer) for testing.

drivers/scsi/scsi.h

@@ -570,7 +570,6 @@ struct scsi_device {
 					   device is busy */
 	struct Scsi_Host *host;
 	request_queue_t *request_queue;
-        atomic_t                device_active; /* commands checked out for device */
 	volatile unsigned short device_busy;	/* commands actually active on low-level */
 	struct list_head free_cmnds;    /* list of available Scsi_Cmnd structs */
 	struct list_head busy_cmnds;    /* list of Scsi_Cmnd structs in use */

drivers/scsi/scsi_lib.c

@@ -787,6 +787,22 @@ static int scsi_init_io(Scsi_Cmnd *SCpnt)
 	return ret;
 }
 
+/*
+ * The target associated with myself can only handle one active command at
+ * a time. Scan through all of the luns on the same target as myself,
+ * return 1 if any are active.
+ */
+static int check_all_luns(struct scsi_device *myself)
+{
+	struct scsi_device *sdev;
+
+	list_for_each_entry(sdev, &myself->same_target_siblings,
+			    same_target_siblings)
+		if (sdev->device_busy)
+			return 1;
+	return 0;
+}
+
 int scsi_prep_fn(struct request_queue *q, struct request *req)
 {
 	struct Scsi_Device_Template *STpnt;
@@ -950,6 +966,9 @@ void scsi_request_fn(request_queue_t * q)
 		if (SDpnt->device_busy >= SDpnt->queue_depth)
 			break;
 
+		if (SDpnt->single_lun && check_all_luns(SDpnt))
+			break;
+
 		if(SHpnt->host_busy == 0 && SHpnt->host_blocked) {
 			/* unblock after host_blocked iterates to zero */
 			if(--SHpnt->host_blocked == 0) {