USB: UB: Let cdrecord to see a device with media absent

The command "cdrecord dev=/dev/uba x.iso" prints nasty garbage if a blank
is not in the drive. This happens because drivers have to set req->errors
separately from just returning zero uptodate with end_that_request_first,
end_that_request_last. These functions only set error in BIO, but sg_io()
ignores it.

Since we're on it, let cdrecord access a device when ->changed is set.
It's useful if someone wants to know device capabilities without burning
anything.
Signed-Off-By: Pete Zaitcev <zaitcev@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/block/ub.c

@@ -358,7 +358,7 @@ static void ub_cmd_build_block(struct ub_dev *sc, struct ub_lun *lun,
 static void ub_cmd_build_packet(struct ub_dev *sc, struct ub_lun *lun,
     struct ub_scsi_cmd *cmd, struct ub_request *urq);
 static void ub_rw_cmd_done(struct ub_dev *sc, struct ub_scsi_cmd *cmd);
-static void ub_end_rq(struct request *rq, int uptodate);
+static void ub_end_rq(struct request *rq, unsigned int status);
 static int ub_rw_cmd_retry(struct ub_dev *sc, struct ub_lun *lun,
     struct ub_request *urq, struct ub_scsi_cmd *cmd);
 static int ub_submit_scsi(struct ub_dev *sc, struct ub_scsi_cmd *cmd);
@@ -639,9 +639,15 @@ static int ub_request_fn_1(struct ub_lun *lun, struct request *rq)
 	struct ub_request *urq;
 	int n_elem;
 
-	if (atomic_read(&sc->poison) || lun->changed) {
+	if (atomic_read(&sc->poison)) {
+		blkdev_dequeue_request(rq);
+		ub_end_rq(rq, DID_NO_CONNECT << 16);
+		return 0;
+	}
+
+	if (lun->changed && !blk_pc_request(rq)) {
 		blkdev_dequeue_request(rq);
-		ub_end_rq(rq, 0);
+		ub_end_rq(rq, SAM_STAT_CHECK_CONDITION);
 		return 0;
 	}
 
@@ -693,7 +699,7 @@ static int ub_request_fn_1(struct ub_lun *lun, struct request *rq)
 
 drop:
 	ub_put_cmd(lun, cmd);
-	ub_end_rq(rq, 0);
+	ub_end_rq(rq, DID_ERROR << 16);
 	return 0;
 }
 
@@ -761,47 +767,53 @@ static void ub_rw_cmd_done(struct ub_dev *sc, struct ub_scsi_cmd *cmd)
 	struct ub_lun *lun = cmd->lun;
 	struct ub_request *urq = cmd->back;
 	struct request *rq;
-	int uptodate;
+	unsigned int scsi_status;
 
 	rq = urq->rq;
 
 	if (cmd->error == 0) {
-		uptodate = 1;
-
 		if (blk_pc_request(rq)) {
 			if (cmd->act_len >= rq->data_len)
 				rq->data_len = 0;
 			else
 				rq->data_len -= cmd->act_len;
 		}
+		scsi_status = 0;
 	} else {
-		uptodate = 0;
-
 		if (blk_pc_request(rq)) {
 			/* UB_SENSE_SIZE is smaller than SCSI_SENSE_BUFFERSIZE */
 			memcpy(rq->sense, sc->top_sense, UB_SENSE_SIZE);
 			rq->sense_len = UB_SENSE_SIZE;
 			if (sc->top_sense[0] != 0)
-				rq->errors = SAM_STAT_CHECK_CONDITION;
+				scsi_status = SAM_STAT_CHECK_CONDITION;
 			else
-				rq->errors = DID_ERROR << 16;
+				scsi_status = DID_ERROR << 16;
 		} else {
 			if (cmd->error == -EIO) {
 				if (ub_rw_cmd_retry(sc, lun, urq, cmd) == 0)
 					return;
 			}
+			scsi_status = SAM_STAT_CHECK_CONDITION;
 		}
 	}
 
 	urq->rq = NULL;
 
 	ub_put_cmd(lun, cmd);
-	ub_end_rq(rq, uptodate);
+	ub_end_rq(rq, scsi_status);
 	blk_start_queue(lun->disk->queue);
 }
 
-static void ub_end_rq(struct request *rq, int uptodate)
+static void ub_end_rq(struct request *rq, unsigned int scsi_status)
 {
+	int uptodate;
+
+	if (scsi_status == 0) {
+		uptodate = 1;
+	} else {
+		uptodate = 0;
+		rq->errors = scsi_status;
+	}
 	end_that_request_first(rq, uptodate, rq->hard_nr_sectors);
 	end_that_request_last(rq, uptodate);
 }