block: unify request timeout handling

Right now SCSI and others do their own command timeout handling.
Move those bits to the block layer.

Instead of having a timer per command, we try to be a bit more clever
and simply have one per-queue. This avoids the overhead of having to
tear down and setup a timer for each command, so it will result in a lot
less timer fiddling.

Signed-off-by: Mike Anderson <andmike@linux.vnet.ibm.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

drivers/scsi/scsi.c

@@ -291,7 +291,6 @@ struct scsi_cmnd *scsi_get_command(struct scsi_device *dev, gfp_t gfp_mask)
 		unsigned long flags;
 
 		cmd->device = dev;
-		init_timer(&cmd->eh_timeout);
 		INIT_LIST_HEAD(&cmd->list);
 		spin_lock_irqsave(&dev->list_lock, flags);
 		list_add_tail(&cmd->list, &dev->cmd_list);
@@ -652,14 +651,19 @@ int scsi_dispatch_cmd(struct scsi_cmnd *cmd)
 	unsigned long timeout;
 	int rtn = 0;
 
+	/*
+	 * We will use a queued command if possible, otherwise we will
+	 * emulate the queuing and calling of completion function ourselves.
+	 */
+	atomic_inc(&cmd->device->iorequest_cnt);
+
 	/* check if the device is still usable */
 	if (unlikely(cmd->device->sdev_state == SDEV_DEL)) {
 		/* in SDEV_DEL we error all commands. DID_NO_CONNECT
 		 * returns an immediate error upwards, and signals
 		 * that the device is no longer present */
 		cmd->result = DID_NO_CONNECT << 16;
-		atomic_inc(&cmd->device->iorequest_cnt);
-		__scsi_done(cmd);
+		scsi_done(cmd);
 		/* return 0 (because the command has been processed) */
 		goto out;
 	}
@@ -672,6 +676,7 @@ int scsi_dispatch_cmd(struct scsi_cmnd *cmd)
 		 * future requests should not occur until the device 
 		 * transitions out of the suspend state.
 		 */
+
 		scsi_queue_insert(cmd, SCSI_MLQUEUE_DEVICE_BUSY);
 
 		SCSI_LOG_MLQUEUE(3, printk("queuecommand : device blocked \n"));
@@ -714,20 +719,8 @@ int scsi_dispatch_cmd(struct scsi_cmnd *cmd)
 		host->resetting = 0;
 	}
 
-	/* 
-	 * AK: unlikely race here: for some reason the timer could
-	 * expire before the serial number is set up below.
-	 */
-	scsi_add_timer(cmd, cmd->timeout_per_command, scsi_times_out);
-
 	scsi_log_send(cmd);
 
-	/*
-	 * We will use a queued command if possible, otherwise we will
-	 * emulate the queuing and calling of completion function ourselves.
-	 */
-	atomic_inc(&cmd->device->iorequest_cnt);
-
 	/*
 	 * Before we queue this command, check if the command
 	 * length exceeds what the host adapter can handle.
@@ -744,6 +737,12 @@ int scsi_dispatch_cmd(struct scsi_cmnd *cmd)
 	}
 
 	spin_lock_irqsave(host->host_lock, flags);
+	/*
+	 * AK: unlikely race here: for some reason the timer could
+	 * expire before the serial number is set up below.
+	 *
+	 * TODO: kill serial or move to blk layer
+	 */
 	scsi_cmd_get_serial(host, cmd); 
 
 	if (unlikely(host->shost_state == SHOST_DEL)) {
@@ -754,12 +753,8 @@ int scsi_dispatch_cmd(struct scsi_cmnd *cmd)
 	}
 	spin_unlock_irqrestore(host->host_lock, flags);
 	if (rtn) {
-		if (scsi_delete_timer(cmd)) {
-			atomic_inc(&cmd->device->iodone_cnt);
-			scsi_queue_insert(cmd,
-					  (rtn == SCSI_MLQUEUE_DEVICE_BUSY) ?
-					  rtn : SCSI_MLQUEUE_HOST_BUSY);
-		}
+		scsi_queue_insert(cmd, (rtn == SCSI_MLQUEUE_DEVICE_BUSY) ?
+						rtn : SCSI_MLQUEUE_HOST_BUSY);
 		SCSI_LOG_MLQUEUE(3,
 		    printk("queuecommand : request rejected\n"));
 	}
@@ -769,24 +764,6 @@ int scsi_dispatch_cmd(struct scsi_cmnd *cmd)
 	return rtn;
 }
 
-/**
- * scsi_req_abort_cmd -- Request command recovery for the specified command
- * @cmd: pointer to the SCSI command of interest
- *
- * This function requests that SCSI Core start recovery for the
- * command by deleting the timer and adding the command to the eh
- * queue.  It can be called by either LLDDs or SCSI Core.  LLDDs who
- * implement their own error recovery MAY ignore the timeout event if
- * they generated scsi_req_abort_cmd.
- */
-void scsi_req_abort_cmd(struct scsi_cmnd *cmd)
-{
-	if (!scsi_delete_timer(cmd))
-		return;
-	scsi_times_out(cmd);
-}
-EXPORT_SYMBOL(scsi_req_abort_cmd);
-
 /**
  * scsi_done - Enqueue the finished SCSI command into the done queue.
  * @cmd: The SCSI Command for which a low-level device driver (LLDD) gives
@@ -802,42 +779,7 @@ EXPORT_SYMBOL(scsi_req_abort_cmd);
  */
 static void scsi_done(struct scsi_cmnd *cmd)
 {
-	/*
-	 * We don't have to worry about this one timing out anymore.
-	 * If we are unable to remove the timer, then the command
-	 * has already timed out.  In which case, we have no choice but to
-	 * let the timeout function run, as we have no idea where in fact
-	 * that function could really be.  It might be on another processor,
-	 * etc, etc.
-	 */
-	if (!scsi_delete_timer(cmd))
-		return;
-	__scsi_done(cmd);
-}
-
-/* Private entry to scsi_done() to complete a command when the timer
- * isn't running --- used by scsi_times_out */
-void __scsi_done(struct scsi_cmnd *cmd)
-{
-	struct request *rq = cmd->request;
-
-	/*
-	 * Set the serial numbers back to zero
-	 */
-	cmd->serial_number = 0;
-
-	atomic_inc(&cmd->device->iodone_cnt);
-	if (cmd->result)
-		atomic_inc(&cmd->device->ioerr_cnt);
-
-	BUG_ON(!rq);
-
-	/*
-	 * The uptodate/nbytes values don't matter, as we allow partial
-	 * completes and thus will check this in the softirq callback
-	 */
-	rq->completion_data = cmd;
-	blk_complete_request(rq);
+	blk_complete_request(cmd->request);
 }
 
 /* Move this to a header if it becomes more generally useful */