[PATCH] Fix BUG at drivers/scsi/scsi_lib.c:1118 caused by "pktsetup dvd /dev/sr0"

 */

static int pkt_generic_packet(struct pktcdvd_device *pd, struct packet_command *cgc)

{

	char sense[SCSI_SENSE_BUFFERSIZE];

	request_queue_t *q;

	request_queue_t *q = bdev_get_queue(pd->bdev);

	struct request *rq;

	DECLARE_COMPLETION_ONSTACK(wait);

	int err = 0;

	int ret = 0;

	q = bdev_get_queue(pd->bdev);

	rq = blk_get_request(q, (cgc->data_direction == CGC_DATA_WRITE) ?

			     WRITE : READ, __GFP_WAIT);

	if (cgc->buflen) {

		if (blk_rq_map_kern(q, rq, cgc->buffer, cgc->buflen, __GFP_WAIT))

			goto out;

	}

	rq->cmd_len = COMMAND_SIZE(rq->cmd[0]);

	memcpy(rq->cmd, cgc->cmd, CDROM_PACKET_SIZE);

	if (sizeof(rq->cmd) > CDROM_PACKET_SIZE)

		memset(rq->cmd + CDROM_PACKET_SIZE, 0, sizeof(rq->cmd) - CDROM_PACKET_SIZE);

	rq = blk_get_request(q, (cgc->data_direction == CGC_DATA_WRITE) ? WRITE : READ,

			     __GFP_WAIT);

	rq->errors = 0;

	rq->rq_disk = pd->bdev->bd_disk;

	rq->bio = NULL;

	rq->buffer = NULL;

	rq->timeout = 60*HZ;

	rq->data = cgc->buffer;

	rq->data_len = cgc->buflen;

	rq->sense = sense;

	memset(sense, 0, sizeof(sense));

	rq->sense_len = 0;

	rq->cmd_type = REQ_TYPE_BLOCK_PC;

	rq->cmd_flags |= REQ_HARDBARRIER;

	if (cgc->quiet)

		rq->cmd_flags |= REQ_QUIET;

	memcpy(rq->cmd, cgc->cmd, CDROM_PACKET_SIZE);

	if (sizeof(rq->cmd) > CDROM_PACKET_SIZE)

		memset(rq->cmd + CDROM_PACKET_SIZE, 0, sizeof(rq->cmd) - CDROM_PACKET_SIZE);

	rq->cmd_len = COMMAND_SIZE(rq->cmd[0]);

	rq->ref_count++;

	rq->end_io_data = &wait;

	rq->end_io = blk_end_sync_rq;

	elv_add_request(q, rq, ELEVATOR_INSERT_BACK, 1);

	generic_unplug_device(q);

	wait_for_completion(&wait);

	if (rq->errors)

		err = -EIO;

	blk_execute_rq(rq->q, pd->bdev->bd_disk, rq, 0);

	ret = rq->errors;

out:

	blk_put_request(rq);

	return err;

	return ret;

}

/*