[PATCH] remove mid-layer assumption that devices must be able to queue at least one command

This allows the request_fn() to recover properly from either host_blocked
or device_blocked at zero command depth.

Also adds the facility for queuecommand() to tell us whether it wants
the host or only the device blocked

drivers/scsi/hosts.c

@@ -209,6 +209,10 @@ struct Scsi_Host * scsi_register(Scsi_Host_Template * tpnt, int j)
     retval->ehandler = NULL;    /* Initial value until the thing starts up. */
     retval->eh_notify   = NULL;    /* Who we notify when we exit. */
 
+    retval->max_host_blocked = tpnt->max_host_blocked ? tpnt->max_host_blocked : SCSI_DEFAULT_HOST_BLOCKED;
+
+    printk("scsi%d: max_host_blocked set to %d\n", retval->host_no, retval->max_host_blocked);
+            
 
     retval->host_blocked = 0;
     retval->host_self_blocked = FALSE;

drivers/scsi/hosts.h

@@ -297,6 +297,19 @@ typedef struct	SHT
      */
     char *proc_name;
 
+    /*
+     * countdown for host blocking with no commands outstanding
+     */
+    unsigned int max_host_blocked;
+
+    /*
+     * Default value for the blocking.  If the queue is empty, host_blocked
+     * counts down in the request_fn until it restarts host operations as
+     * zero is reached.  
+     *
+     * FIXME: This should probably be a value in the template */
+    #define SCSI_DEFAULT_HOST_BLOCKED	7
+
 } Scsi_Host_Template;
 
 /*
@@ -418,12 +431,9 @@ struct Scsi_Host
     unsigned int host_blocked;
 
     /*
-     * Initial value for the blocking.  If the queue is empty, host_blocked
-     * counts down in the request_fn until it restarts host operations as
-     * zero is reached.  
-     *
-     * FIXME: This should probably be a value in the template */
-    #define SCSI_START_HOST_BLOCKED	7
+     * Value host_blocked counts down from
+     */
+    unsigned int max_host_blocked;
 
     void (*select_queue_depths)(struct Scsi_Host *, Scsi_Device *);
 

drivers/scsi/scsi.c

@@ -622,19 +622,9 @@ static int scsi_mlqueue_insert(Scsi_Cmnd * cmd, int reason)
 	 * possibly work anyways.
 	 */
 	if (reason == SCSI_MLQUEUE_HOST_BUSY) {
-		if (host->host_busy == 0) {
-			if (scsi_retry_command(cmd) == 0) {
-				return 0;
-			}
-		}
-		host->host_blocked = SCSI_START_HOST_BLOCKED;
+		host->host_blocked = host->max_host_blocked;
 	} else {
-		if (cmd->device->device_busy == 0) {
-			if (scsi_retry_command(cmd) == 0) {
-				return 0;
-			}
-		}
-		cmd->device->device_blocked = TRUE;
+                cmd->device->device_blocked = cmd->device->max_device_blocked;
 	}
 
 	/*
@@ -793,7 +783,7 @@ int scsi_dispatch_cmd(Scsi_Cmnd * SCpnt)
 			spin_unlock_irqrestore(host->host_lock, flags);
 			if (rtn != 0) {
 				scsi_delete_timer(SCpnt);
-				scsi_mlqueue_insert(SCpnt, SCSI_MLQUEUE_HOST_BUSY);
+				scsi_mlqueue_insert(SCpnt, rtn == SCSI_MLQUEUE_DEVICE_BUSY ? rtn : SCSI_MLQUEUE_HOST_BUSY);
 				SCSI_LOG_MLQUEUE(3,
 				   printk("queuecommand : request rejected\n"));                                
 			}
@@ -1397,7 +1387,7 @@ void scsi_finish_command(Scsi_Cmnd * SCpnt)
          * host full condition on the host.
          */
         host->host_blocked = 0;
-        device->device_blocked = FALSE;
+        device->device_blocked = 0;
 
 	/*
 	 * If we have valid sense information, then some kind of recovery

drivers/scsi/scsi.h

@@ -611,12 +611,18 @@ struct scsi_device {
 				 * this device */
 	unsigned expecting_cc_ua:1;	/* Expecting a CHECK_CONDITION/UNIT_ATTN
 					 * because we did a bus reset. */
-	unsigned device_blocked:1;	/* Device returned QUEUE_FULL. */
 	unsigned ten:1;		/* support ten byte read / write */
 	unsigned remap:1;	/* support remapping  */
 	unsigned starved:1;	/* unable to process commands because
 				   host busy */
 
+	unsigned int device_blocked;	/* Device returned QUEUE_FULL. */
+
+	unsigned int max_device_blocked; /* what device_blocked counts down from  */
+  	/* default value if the device doesn't override */
+	#define SCSI_DEFAULT_DEVICE_BLOCKED	3
+
+
 	// Flag to allow revalidate to succeed in sd_open
 	int allow_revalidate;
 	struct device sdev_driverfs_dev;

drivers/scsi/scsi_lib.c

@@ -756,14 +756,22 @@ void scsi_request_fn(request_queue_t * q)
 
 		if(SHpnt->host_busy == 0 && SHpnt->host_blocked) {
 			/* unblock after host_blocked iterates to zero */
-			if(--host_blocked == 0) {
+			if(--SHpnt->host_blocked == 0) {
 				printk("scsi%d unblocking host at zero depth\n", SHpnt->host_no);
 			} else {
 				blk_plug_device(q);
 				break;
 			}
 		}
-				
+		if(SDpnt->device_busy == 0 && SDpnt->device_blocked) {
+			/* unblock after device_blocked iterates to zero */
+			if(--SDpnt->device_blocked == 0) {
+				printk("scsi%d (%d:%d) unblocking device at zero depth\n", SHpnt->host_no, SDpnt->id, SDpnt->lun);
+			} else {
+				blk_plug_device(q);
+				break;
+			}
+		}
 		/*
 		 * If the device cannot accept another request, then quit.
 		 */

drivers/scsi/scsi_scan.c

@@ -1461,6 +1461,10 @@ static int scsi_add_lun(Scsi_Device *sdevscan, Scsi_Device **sdevnew,
 	if (*bflags & BLIST_SINGLELUN)
 		sdev->single_lun = 1;
 
+	/* if the device needs this changing, it may do so in the detect
+	 * function */
+	sdev->max_device_blocked = SCSI_DEFAULT_DEVICE_BLOCKED;
+
 	for (sdt = scsi_devicelist; sdt; sdt = sdt->next)
 		if (sdt->detect)
 			sdev->attached += (*sdt->detect) (sdev);