[PATCH] Correct tag initialisation for commands

[Hannes Reinecke <hare@suse.de>]

Hi all,

currently the initialisation of scmd->tag seems to be wrong.
We have this lines from scsi_lib.c:scsi_get_cmd_from_req():

	/* pull a tag out of the request if we have one */
	cmd->tag = req->tag;

which are supposed to fill the tag value for a given command.
However, the function is called from the ->prep_fn callback,
invoked from elv_next_request() in scsi_request_fn().

In scsi_request_fn() we have:

	req = elv_next_request(q);
	if (!req || !scsi_dev_queue_ready(q, sdev))
		break;

	if (unlikely(!scsi_device_online(sdev))) {
		sdev_printk(KERN_ERR, sdev,
			    "rejecting I/O to offline device\n");
		scsi_kill_request(req, q);
		continue;
	}

	/*
	 * Remove the request from the request list.
	 */
	if (!(blk_queue_tagged(q) && !blk_queue_start_tag(q, req)))
		blkdev_dequeue_request(req);

ie the value of rq->tag is filled _after it has been copied
to scmd->tag.

A proposed patch would be:

--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -1055,8 +1055,6 @@ static struct scsi_cmnd *scsi_get_cmd_from_req(struct scsi_device *sdev,
 		cmd = req->special;
 	}
 
-	/* pull a tag out of the request if we have one */
-	cmd->tag = req->tag;
 	cmd->request = req;
 
 	return cmd;
@@ -1445,6 +1443,9 @@ static void scsi_request_fn(struct request_queue *q)
 			blk_dump_rq_flags(req, "foo");
 			BUG();
 		}
+		/* pull a tag out of the request if we have one */
+		cmd->tag = req->tag;
+
 		spin_lock(shost->host_lock);
 
 		if (!scsi_host_queue_ready(q, shost, sdev))

Comments?

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		      zSeries & Storage
hare@suse.de			      +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: Markus Rex, HRB 16746 (AG Nürnberg)
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