ub.c

Linux块设备驱动源码

static ssize_t ub_diag_show(struct device *dev, struct device_attribute *attr,
    char *page)
{
	struct usb_interface *intf;
	struct ub_dev *sc;
	struct list_head *p;
	struct ub_lun *lun;
	int cnt;
	unsigned long flags;
	int nc, nh;
	int i, j;
	struct ub_scsi_cmd_trace *t;

	intf = to_usb_interface(dev);
	sc = usb_get_intfdata(intf);
	if (sc == NULL)
		return 0;

	cnt = 0;
	spin_lock_irqsave(&sc->lock, flags);

	cnt += sprintf(page + cnt,
	    "qlen %d qmax %d\n",
	    sc->cmd_queue.qlen, sc->cmd_queue.qmax);
	cnt += sprintf(page + cnt,
	    "sg %d %d %d %d %d .. %d\n",
	    sc->sg_stat[0],
	    sc->sg_stat[1],
	    sc->sg_stat[2],
	    sc->sg_stat[3],
	    sc->sg_stat[4],
	    sc->sg_stat[5]);

	list_for_each (p, &sc->luns) {
		lun = list_entry(p, struct ub_lun, link);
		cnt += sprintf(page + cnt,
		    "lun %u changed %d removable %d readonly %d\n",
		    lun->num, lun->changed, lun->removable, lun->readonly);
	}

	if ((nc = sc->tr.cur + 1) == SCMD_TRACE_SZ) nc = 0;
	for (j = 0; j < SCMD_TRACE_SZ; j++) {
		t = &sc->tr.vec[nc];

		cnt += sprintf(page + cnt, "%08x %02x", t->tag, t->op);
		if (t->op == REQUEST_SENSE) {
			cnt += sprintf(page + cnt, " [sense %x %02x %02x]",
					t->key, t->asc, t->ascq);
		} else {
			cnt += sprintf(page + cnt, " %c", UB_DIR_CHAR(t->dir));
			cnt += sprintf(page + cnt, " [%5d %5d]",
					t->req_size, t->act_size);
		}
		if ((nh = t->hcur + 1) == SCMD_ST_HIST_SZ) nh = 0;
		for (i = 0; i < SCMD_ST_HIST_SZ; i++) {
			cnt += sprintf(page + cnt, " %s",
					ub_scsi_cmd_stname[(int)t->st_hst[nh]]);
			if (++nh == SCMD_ST_HIST_SZ) nh = 0;
		}
		cnt += sprintf(page + cnt, "\n");

		if (++nc == SCMD_TRACE_SZ) nc = 0;
	}

	spin_unlock_irqrestore(&sc->lock, flags);
	return cnt;
}

static DEVICE_ATTR(diag, S_IRUGO, ub_diag_show, NULL); /* N.B. World readable */

/*
 * The id allocator.
 *
 * This also stores the host for indexing by minor, which is somewhat dirty.
 */
static int ub_id_get(void)
{
	unsigned long flags;
	int i;

	spin_lock_irqsave(&ub_lock, flags);
	for (i = 0; i < UB_MAX_HOSTS; i++) {
		if (ub_hostv[i] == 0) {
			ub_hostv[i] = 1;
			spin_unlock_irqrestore(&ub_lock, flags);
			return i;
		}
	}
	spin_unlock_irqrestore(&ub_lock, flags);
	return -1;
}

static void ub_id_put(int id)
{
	unsigned long flags;

	if (id < 0 || id >= UB_MAX_HOSTS) {
		printk(KERN_ERR DRV_NAME ": bad host ID %d\n", id);
		return;
	}

	spin_lock_irqsave(&ub_lock, flags);
	if (ub_hostv[id] == 0) {
		spin_unlock_irqrestore(&ub_lock, flags);
		printk(KERN_ERR DRV_NAME ": freeing free host ID %d\n", id);
		return;
	}
	ub_hostv[id] = 0;
	spin_unlock_irqrestore(&ub_lock, flags);
}

/*
 * Downcount for deallocation. This rides on two assumptions:
 *  - once something is poisoned, its refcount cannot grow
 *  - opens cannot happen at this time (del_gendisk was done)
 * If the above is true, we can drop the lock, which we need for
 * blk_cleanup_queue(): the silly thing may attempt to sleep.
 * [Actually, it never needs to sleep for us, but it calls might_sleep()]
 */
static void ub_put(struct ub_dev *sc)
{
	unsigned long flags;

	spin_lock_irqsave(&ub_lock, flags);
	--sc->openc;
	if (sc->openc == 0 && atomic_read(&sc->poison)) {
		spin_unlock_irqrestore(&ub_lock, flags);
		ub_cleanup(sc);
	} else {
		spin_unlock_irqrestore(&ub_lock, flags);
	}
}

/*
 * Final cleanup and deallocation.
 */
static void ub_cleanup(struct ub_dev *sc)
{
	struct list_head *p;
	struct ub_lun *lun;
	request_queue_t *q;

	while (!list_empty(&sc->luns)) {
		p = sc->luns.next;
		lun = list_entry(p, struct ub_lun, link);
		list_del(p);

		/* I don't think queue can be NULL. But... Stolen from sx8.c */
		if ((q = lun->disk->queue) != NULL)
			blk_cleanup_queue(q);
		/*
		 * If we zero disk->private_data BEFORE put_disk, we have
		 * to check for NULL all over the place in open, release,
		 * check_media and revalidate, because the block level
		 * semaphore is well inside the put_disk.
		 * But we cannot zero after the call, because *disk is gone.
		 * The sd.c is blatantly racy in this area.
		 */
		/* disk->private_data = NULL; */
		put_disk(lun->disk);
		lun->disk = NULL;

		ub_id_put(lun->id);
		kfree(lun);
	}

	kfree(sc);
}

/*
 * The "command allocator".
 */
static struct ub_scsi_cmd *ub_get_cmd(struct ub_lun *lun)
{
	struct ub_scsi_cmd *ret;

	if (lun->cmda[0])
		return NULL;
	ret = &lun->cmdv[0];
	lun->cmda[0] = 1;
	return ret;
}

static void ub_put_cmd(struct ub_lun *lun, struct ub_scsi_cmd *cmd)
{
	if (cmd != &lun->cmdv[0]) {
		printk(KERN_WARNING "%s: releasing a foreign cmd %p\n",
		    lun->name, cmd);
		return;
	}
	if (!lun->cmda[0]) {
		printk(KERN_WARNING "%s: releasing a free cmd\n", lun->name);
		return;
	}
	lun->cmda[0] = 0;
}

/*
 * The command queue.
 */
static void ub_cmdq_add(struct ub_dev *sc, struct ub_scsi_cmd *cmd)
{
	struct ub_scsi_cmd_queue *t = &sc->cmd_queue;

	if (t->qlen++ == 0) {
		t->head = cmd;
		t->tail = cmd;
	} else {
		t->tail->next = cmd;
		t->tail = cmd;
	}

	if (t->qlen > t->qmax)
		t->qmax = t->qlen;
}

static void ub_cmdq_insert(struct ub_dev *sc, struct ub_scsi_cmd *cmd)
{
	struct ub_scsi_cmd_queue *t = &sc->cmd_queue;

	if (t->qlen++ == 0) {
		t->head = cmd;
		t->tail = cmd;
	} else {
		cmd->next = t->head;
		t->head = cmd;
	}

	if (t->qlen > t->qmax)
		t->qmax = t->qlen;
}

static struct ub_scsi_cmd *ub_cmdq_pop(struct ub_dev *sc)
{
	struct ub_scsi_cmd_queue *t = &sc->cmd_queue;
	struct ub_scsi_cmd *cmd;

	if (t->qlen == 0)
		return NULL;
	if (--t->qlen == 0)
		t->tail = NULL;
	cmd = t->head;
	t->head = cmd->next;
	cmd->next = NULL;
	return cmd;
}

#define ub_cmdq_peek(sc)  ((sc)->cmd_queue.head)

/*
 * The request function is our main entry point
 */

static void ub_request_fn(request_queue_t *q)
{
	struct ub_lun *lun = q->queuedata;
	struct request *rq;

	while ((rq = elv_next_request(q)) != NULL) {
		if (ub_request_fn_1(lun, rq) != 0) {
			blk_stop_queue(q);
			break;
		}
	}
}

static int ub_request_fn_1(struct ub_lun *lun, struct request *rq)
{
	struct ub_dev *sc = lun->udev;
	struct ub_scsi_cmd *cmd;
	int rc;

	if (atomic_read(&sc->poison) || lun->changed) {
		blkdev_dequeue_request(rq);
		ub_end_rq(rq, 0);
		return 0;
	}

	if ((cmd = ub_get_cmd(lun)) == NULL)
		return -1;
	memset(cmd, 0, sizeof(struct ub_scsi_cmd));

	blkdev_dequeue_request(rq);
	if (blk_pc_request(rq)) {
		rc = ub_cmd_build_packet(sc, lun, cmd, rq);
	} else {
		rc = ub_cmd_build_block(sc, lun, cmd, rq);
	}
	if (rc != 0) {
		ub_put_cmd(lun, cmd);
		ub_end_rq(rq, 0);
		return 0;
	}
	cmd->state = UB_CMDST_INIT;
	cmd->lun = lun;
	cmd->done = ub_rw_cmd_done;
	cmd->back = rq;

	cmd->tag = sc->tagcnt++;
	if (ub_submit_scsi(sc, cmd) != 0) {
		ub_put_cmd(lun, cmd);
		ub_end_rq(rq, 0);
		return 0;
	}

	return 0;
}

static int ub_cmd_build_block(struct ub_dev *sc, struct ub_lun *lun,
    struct ub_scsi_cmd *cmd, struct request *rq)
{
	int ub_dir;
	int n_elem;
	unsigned int block, nblks;

	if (rq_data_dir(rq) == WRITE)
		ub_dir = UB_DIR_WRITE;
	else
		ub_dir = UB_DIR_READ;
	cmd->dir = ub_dir;

	/*
	 * get scatterlist from block layer
	 */
	n_elem = blk_rq_map_sg(lun->disk->queue, rq, &cmd->sgv[0]);
	if (n_elem <= 0) {
		printk(KERN_INFO "%s: failed request map (%d)\n",
		    sc->name, n_elem); /* P3 */
		return -1;		/* request with no s/g entries? */
	}
	if (n_elem > UB_MAX_REQ_SG) {	/* Paranoia */
		printk(KERN_WARNING "%s: request with %d segments\n",
		    sc->name, n_elem);
		return -1;
	}
	cmd->nsg = n_elem;
	sc->sg_stat[n_elem < 5 ? n_elem : 5]++;

	/*
	 * build the command
	 *
	 * The call to blk_queue_hardsect_size() guarantees that request
	 * is aligned, but it is given in terms of 512 byte units, always.
	 */
	block = rq->sector >> lun->capacity.bshift;
	nblks = rq->nr_sectors >> lun->capacity.bshift;

	cmd->cdb[0] = (ub_dir == UB_DIR_READ)? READ_10: WRITE_10;
	/* 10-byte uses 4 bytes of LBA: 2147483648KB, 2097152MB, 2048GB */
	cmd->cdb[2] = block >> 24;
	cmd->cdb[3] = block >> 16;
	cmd->cdb[4] = block >> 8;
	cmd->cdb[5] = block;
	cmd->cdb[7] = nblks >> 8;
	cmd->cdb[8] = nblks;
	cmd->cdb_len = 10;

	cmd->len = rq->nr_sectors * 512;

	return 0;
}

static int ub_cmd_build_packet(struct ub_dev *sc, struct ub_lun *lun,
    struct ub_scsi_cmd *cmd, struct request *rq)
{
	int n_elem;

	if (rq->data_len == 0) {
		cmd->dir = UB_DIR_NONE;
	} else {
		if (rq_data_dir(rq) == WRITE)
			cmd->dir = UB_DIR_WRITE;
		else
			cmd->dir = UB_DIR_READ;

	}

	/*
	 * get scatterlist from block layer
	 */
	n_elem = blk_rq_map_sg(lun->disk->queue, rq, &cmd->sgv[0]);
	if (n_elem < 0) {
		printk(KERN_INFO "%s: failed request map (%d)\n",
		    sc->name, n_elem); /* P3 */
		return -1;
	}
	if (n_elem > UB_MAX_REQ_SG) {	/* Paranoia */
		printk(KERN_WARNING "%s: request with %d segments\n",
		    sc->name, n_elem);
		return -1;
	}
	cmd->nsg = n_elem;
	sc->sg_stat[n_elem < 5 ? n_elem : 5]++;

	memcpy(&cmd->cdb, rq->cmd, rq->cmd_len);
	cmd->cdb_len = rq->cmd_len;

	cmd->len = rq->data_len;

	return 0;
}

static void ub_rw_cmd_done(struct ub_dev *sc, struct ub_scsi_cmd *cmd)
{
	struct request *rq = cmd->back;
	struct ub_lun *lun = cmd->lun;
	int uptodate;

	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;
		}
	} 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;
			else
				rq->errors = DID_ERROR << 16;
		}
	}

	ub_put_cmd(lun, cmd);
	ub_end_rq(rq, uptodate);
	blk_start_queue(lun->disk->queue);
}

static void ub_end_rq(struct request *rq, int uptodate)
{
	int rc;

	rc = end_that_request_first(rq, uptodate, rq->hard_nr_sectors);
	// assert(rc == 0);
	end_that_request_last(rq);
}

/*
 * Submit a regular SCSI operation (not an auto-sense).
 *
 * The Iron Law of Good Submit Routine is:
 * Zero return - callback is done, Nonzero return - callback is not done.
 * No exceptions.
 *
 * Host is assumed locked.
 *
 * XXX We only support Bulk for the moment.
 */
static int ub_submit_scsi(struct ub_dev *sc, struct ub_scsi_cmd *cmd)
{

	if (cmd->state != UB_CMDST_INIT ||
	    (cmd->dir != UB_DIR_NONE && cmd->len == 0)) {
		return -EINVAL;
	}

	ub_cmdq_add(sc, cmd);
	/*
	 * We can call ub_scsi_dispatch(sc) right away here, but it's a little
	 * safer to jump to a tasklet, in case upper layers do something silly.
	 */
	tasklet_schedule(&sc->tasklet);
	return 0;
}

/*
 * Submit the first URB for the queued command.
 * This function does not deal with queueing in any way.
 */
static int ub_scsi_cmd_start(struct ub_dev *sc, struct ub_scsi_cmd *cmd)
{
	struct bulk_cb_wrap *bcb;
	int rc;

	bcb = &sc->work_bcb;

	/*
	 * ``If the allocation length is eighteen or greater, and a device
	 * server returns less than eithteen bytes of data, the application
	 * client should assume that the bytes not transferred would have been
	 * zeroes had the device server returned those bytes.''
	 *
	 * We zero sense for all commands so that when a packet request
	 * fails it does not return a stale sense.
	 */
	memset(&sc->top_sense, 0, UB_SENSE_SIZE);

	/* set up the command wrapper */
	bcb->Signature = cpu_to_le32(US_BULK_CB_SIGN);
	bcb->Tag = cmd->tag;		/* Endianness is not important */
	bcb->DataTransferLength = cpu_to_le32(cmd->len);
	bcb->Flags = (cmd->dir == UB_DIR_READ) ? 0x80 : 0;