Merge mulgrave.(none):/home/jejb/BK/scsi-reject-zero-2.5

into mulgrave.(none):/home/jejb/BK/scsi-for-linus-2.5

drivers/scsi/hosts.c

@@ -209,8 +209,9 @@ 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;
 
-    retval->host_blocked = FALSE;
+    retval->host_blocked = 0;
     retval->host_self_blocked = FALSE;
 
 #ifdef DEBUG

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;
 
 /*
@@ -394,11 +407,6 @@ struct Scsi_Host
     unsigned highmem_io:1;
     unsigned use_blk_tcq:1;
 
-    /*
-     * Host has rejected a command because it was busy.
-     */
-    unsigned host_blocked:1;
-
     /*
      * Host has requested that no further requests come through for the
      * time being.
@@ -417,6 +425,16 @@ struct Scsi_Host
      */
     unsigned some_device_starved:1;
    
+    /*
+     * Host has rejected a command because it was busy.
+     */
+    unsigned int host_blocked;
+
+    /*
+     * Value host_blocked counts down from
+     */
+    unsigned int max_host_blocked;
+
     void (*select_queue_depths)(struct Scsi_Host *, Scsi_Device *);
 
     /*

drivers/scsi/scsi.c

@@ -616,25 +616,17 @@ static int scsi_mlqueue_insert(Scsi_Cmnd * cmd, int reason)
 	 * If the host/device isn't busy, assume that something actually
 	 * completed, and that we should be able to queue a command now.
 	 *
-	 * Note that there is an implicit assumption that every host can
-	 * always queue at least one command.  If a host is inactive and
-	 * cannot queue any commands, I don't see how things could
-	 * possibly work anyways.
+	 * Note that the prior mid-layer assumption that any host could
+	 * always queue at least one command is now broken.  The mid-layer
+	 * will implement a user specifiable stall (see
+	 * scsi_host.max_host_blocked and scsi_device.max_device_blocked)
+	 * if a command is requeued with no other commands outstanding
+	 * either for the device or for the host.
 	 */
 	if (reason == SCSI_MLQUEUE_HOST_BUSY) {
-		if (host->host_busy == 0) {
-			if (scsi_retry_command(cmd) == 0) {
-				return 0;
-			}
-		}
-		host->host_blocked = TRUE;
+		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 +785,7 @@ 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"));                                
 			}
@@ -1396,8 +1388,8 @@ void scsi_finish_command(Scsi_Cmnd * SCpnt)
          * for both the queue full condition on a device, and for a
          * host full condition on the host.
          */
-        host->host_blocked = FALSE;
-        device->device_blocked = FALSE;
+        host->host_blocked = 0;
+        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_error.c

@@ -1341,6 +1341,13 @@ int scsi_decide_disposition(Scsi_Cmnd *scmd)
 		 * the case of trying to send too many commands to a
 		 * tagged queueing device.
 		 */
+	case BUSY:
+		/*
+		 * device can't talk to us at the moment.  Should only
+		 * occur (SAM-3) when the task queue is empty, so will cause
+		 * the empty queue handling to trigger a stall in the
+		 * device.
+		 */
 		return ADD_TO_MLQUEUE;
 	case GOOD:
 	case COMMAND_TERMINATED:
@@ -1358,8 +1365,6 @@ int scsi_decide_disposition(Scsi_Cmnd *scmd)
 		 * who knows?  FIXME(eric)
 		 */
 		return SUCCESS;
-	case BUSY:
-		goto maybe_retry;
 
 	case RESERVATION_CONFLICT:
 		printk("scsi%d (%d,%d,%d) : reservation conflict\n", 

drivers/scsi/scsi_lib.c

@@ -754,6 +754,24 @@ void scsi_request_fn(request_queue_t * q)
 		if (SHpnt->in_recovery || blk_queue_plugged(q))
 			return;
 
+		if(SHpnt->host_busy == 0 && SHpnt->host_blocked) {
+			/* unblock after host_blocked iterates to zero */
+			if(--SHpnt->host_blocked == 0) {
+				SCSI_LOG_MLQUEUE(3, 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) {
+				SCSI_LOG_MLQUEUE(3, 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);