scsi: core: Remove scsi_cmnd.tag

It is never read, so get rid of it.

Link: https://lore.kernel.org/r/1628862553-179450-4-git-send-email-john.garry@huawei.comReviewed-by: NHannes Reinecke <hare@suse.de>
Reviewed-by: NBart Van Assche <bvanassche@acm.org>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NJohn Garry <john.garry@huawei.com>
Signed-off-by: NMartin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/scsi_lib.c

@@ -1540,7 +1540,6 @@ static blk_status_t scsi_prepare_cmd(struct request *req)
 
 	scsi_init_command(sdev, cmd);
 
-	cmd->tag = req->tag;
 	cmd->prot_op = SCSI_PROT_NORMAL;
 	if (blk_rq_bytes(req))
 		cmd->sc_data_direction = rq_dma_dir(req);

include/scsi/scsi_cmnd.h

@@ -139,7 +139,6 @@ struct scsi_cmnd {
 	int flags;		/* Command flags */
 	unsigned long state;	/* Command completion state */
 
-	unsigned char tag;	/* SCSI-II queued command tag */
 	unsigned int extra_len;	/* length of alignment and padding */
 };