- 根目录:
- drivers
- block
- sunvdc.c
/* sunvdc.c: Sun LDOM Virtual Disk Client.
*
* Copyright (C) 2007, 2008 David S. Miller <davem@davemloft.net>
*/
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/blkdev.h>
#include <linux/hdreg.h>
#include <linux/genhd.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/completion.h>
#include <linux/delay.h>
#include <linux/init.h>
#include <linux/list.h>
#include <linux/scatterlist.h>
#include <asm/vio.h>
#include <asm/ldc.h>
#define DRV_MODULE_NAME "sunvdc"
#define PFX DRV_MODULE_NAME ": "
#define DRV_MODULE_VERSION "1.0"
#define DRV_MODULE_RELDATE "June 25, 2007"
static char version[] __devinitdata =
DRV_MODULE_NAME ".c:v" DRV_MODULE_VERSION " (" DRV_MODULE_RELDATE ")\n";
MODULE_AUTHOR("David S. Miller (davem@davemloft.net)");
MODULE_DESCRIPTION("Sun LDOM virtual disk client driver");
MODULE_LICENSE("GPL");
MODULE_VERSION(DRV_MODULE_VERSION);
#define VDC_TX_RING_SIZE 256
#define WAITING_FOR_LINK_UP 0x01
#define WAITING_FOR_TX_SPACE 0x02
#define WAITING_FOR_GEN_CMD 0x04
#define WAITING_FOR_ANY -1
struct vdc_req_entry {
struct request *req;
};
struct vdc_port {
struct vio_driver_state vio;
struct gendisk *disk;
struct vdc_completion *cmp;
u64 req_id;
u64 seq;
struct vdc_req_entry rq_arr[VDC_TX_RING_SIZE];
unsigned long ring_cookies;
u64 max_xfer_size;
u32 vdisk_block_size;
/* The server fills these in for us in the disk attribute
* ACK packet.
*/
u64 operations;
u32 vdisk_size;
u8 vdisk_type;
char disk_name[32];
struct vio_disk_geom geom;
struct vio_disk_vtoc label;
};
static inline struct vdc_port *to_vdc_port(struct vio_driver_state *vio)
{
return container_of(vio, struct vdc_port, vio);
}
/* Ordered from largest major to lowest */
static struct vio_version vdc_versions[] = {
{ .major = 1, .minor = 0 },
};
#define VDCBLK_NAME "vdisk"
static int vdc_major;
#define PARTITION_SHIFT 3
static inline u32 vdc_tx_dring_avail(struct vio_dring_state *dr)
{
return vio_dring_avail(dr, VDC_TX_RING_SIZE);
}
static int vdc_getgeo(struct block_device *bdev, struct hd_geometry *geo)
{
struct gendisk *disk = bdev->bd_disk;
struct vdc_port *port = disk->private_data;
geo->heads = (u8) port->geom.num_hd;
geo->sectors = (u8) port->geom.num_sec;
geo->cylinders = port->geom.num_cyl;
return 0;
}
static const struct block_device_operations vdc_fops = {
.owner = THIS_MODULE,
.getgeo = vdc_getgeo,
};
static void vdc_finish(struct vio_driver_state *vio, int err, int waiting_for)
{
if (vio->cmp &&
(waiting_for == -1 ||
vio->cmp->waiting_for == waiting_for)) {
vio->cmp->err = err;
complete(&vio->cmp->com);
vio->cmp = NULL;
}
}
static void vdc_handshake_complete(struct vio_driver_state *vio)
{
vdc_finish(vio, 0, WAITING_FOR_LINK_UP);
}
static int vdc_handle_unknown(struct vdc_port *port, void *arg)
{
struct vio_msg_tag *pkt = arg;
printk(KERN_ERR PFX "Received unknown msg [%02x:%02x:%04x:%08x]\n",
pkt->type, pkt->stype, pkt->stype_env, pkt->sid);
printk(KERN_ERR PFX "Resetting connection.\n");
ldc_disconnect(port->vio.lp);
return -ECONNRESET;
}
static int vdc_send_attr(struct vio_driver_state *vio)
{
struct vdc_port *port = to_vdc_port(vio);
struct vio_disk_attr_info pkt;
memset(&pkt, 0, sizeof(pkt));
pkt.tag.type = VIO_TYPE_CTRL;
pkt.tag.stype = VIO_SUBTYPE_INFO;
pkt.tag.stype_env = VIO_ATTR_INFO;
pkt.tag.sid = vio_send_sid(vio);
pkt.xfer_mode = VIO_DRING_MODE;
pkt.vdisk_block_size = port->vdisk_block_size;
pkt.max_xfer_size = port->max_xfer_size;
viodbg(HS, "SEND ATTR xfer_mode[0x%x] blksz[%u] max_xfer[%llu]\n",
pkt.xfer_mode, pkt.vdisk_block_size, pkt.max_xfer_size);
return vio_ldc_send(&port->vio, &pkt, sizeof(pkt));
}
static int vdc_handle_attr(struct vio_driver_state *vio, void *arg)
{
struct vdc_port *port = to_vdc_port(vio);
struct vio_disk_attr_info *pkt = arg;
viodbg(HS, "GOT ATTR stype[0x%x] ops[%llx] disk_size[%llu] disk_type[%x] "
"xfer_mode[0x%x] blksz[%u] max_xfer[%llu]\n",
pkt->tag.stype, pkt->operations,
pkt->vdisk_size, pkt->vdisk_type,
pkt->xfer_mode, pkt->vdisk_block_size,
pkt->max_xfer_size);
if (pkt->tag.stype == VIO_SUBTYPE_ACK) {
switch (pkt->vdisk_type) {
case VD_DISK_TYPE_DISK:
case VD_DISK_TYPE_SLICE:
break;
default:
printk(KERN_ERR PFX "%s: Bogus vdisk_type 0x%x\n",
vio->name, pkt->vdisk_type);
return -ECONNRESET;
}
if (pkt->vdisk_block_size > port->vdisk_block_size) {
printk(KERN_ERR PFX "%s: BLOCK size increased "
"%u --> %u\n",
vio->name,
port->vdisk_block_size, pkt->vdisk_block_size);
return -ECONNRESET;
}
port->operations = pkt->operations;
port->vdisk_size = pkt->vdisk_size;
port->vdisk_type = pkt->vdisk_type;
if (pkt->max_xfer_size < port->max_xfer_size)
port->max_xfer_size = pkt->max_xfer_size;
port->vdisk_block_size = pkt->vdisk_block_size;
return 0;
} else {
printk(KERN_ERR PFX "%s: Attribute NACK\n", vio->name);
return -ECONNRESET;
}
}
static void vdc_end_special(struct vdc_port *port, struct vio_disk_desc *desc)
{
int err = desc->status;
vdc_finish(&port->vio, -err, WAITING_FOR_GEN_CMD);
}
static void vdc_end_one(struct vdc_port *port, struct vio_dring_state *dr,
unsigned int index)
{
struct vio_disk_desc *desc = vio_dring_entry(dr, index);
struct vdc_req_entry *rqe = &port->rq_arr[index];
struct request *req;
if (unlikely(desc->hdr.state != VIO_DESC_DONE))
return;
ldc_unmap(port->vio.lp, desc->cookies, desc->ncookies);
desc->hdr.state = VIO_DESC_FREE;
dr->cons = (index + 1) & (VDC_TX_RING_SIZE - 1);
req = rqe->req;
if (req == NULL) {
vdc_end_special(port, desc);
return;
}
rqe->req = NULL;
__blk_end_request(req, (desc->status ? -EIO : 0), desc->size);
if (blk_queue_stopped(port->disk->queue))
blk_start_queue(port->disk->queue);
}
static int vdc_ack(struct vdc_port *port, void *msgbuf)
{
struct vio_dring_state *dr = &port->vio.drings[VIO_DRIVER_TX_RING];
struct vio_dring_data *pkt = msgbuf;
if (unlikely(pkt->dring_ident != dr->ident ||
pkt->start_idx != pkt->end_idx ||
pkt->start_idx >= VDC_TX_RING_SIZE))
return 0;
vdc_end_one(port, dr, pkt->start_idx);
return 0;
}
static int vdc_nack(struct vdc_port *port, void *msgbuf)
{
/* XXX Implement me XXX */
return 0;
}
static void vdc_event(void *arg, int event)
{
struct vdc_port *port = arg;
struct vio_driver_state *vio = &port->vio;
unsigned long flags;
int err;
spin_lock_irqsave(&vio->lock, flags);
if (unlikely(event == LDC_EVENT_RESET ||
event == LDC_EVENT_UP)) {
vio_link_state_change(vio, event);
spin_unlock_irqrestore(&vio->lock, flags);
return;
}
if (unlikely(event != LDC_EVENT_DATA_READY)) {
printk(KERN_WARNING PFX "Unexpected LDC event %d\n", event);
spin_unlock_irqrestore(&vio->lock, flags);
return;
}
err = 0;
while (1) {
union {
struct vio_msg_tag tag;
u64 raw[8];
} msgbuf;
err = ldc_read(vio->lp, &msgbuf, sizeof(msgbuf));
if (unlikely(err < 0)) {
if (err == -ECONNRESET)
vio_conn_reset(vio);
break;
}
if (err == 0)
break;
viodbg(DATA, "TAG [%02x:%02x:%04x:%08x]\n",
msgbuf.tag.type,
msgbuf.tag.stype,
msgbuf.tag.stype_env,
msgbuf.tag.sid);
err = vio_validate_sid(vio, &msgbuf.tag);
if (err < 0)
break;
if (likely(msgbuf.tag.type == VIO_TYPE_DATA)) {
if (msgbuf.tag.stype == VIO_SUBTYPE_ACK)
err = vdc_ack(port, &msgbuf);
else if (msgbuf.tag.stype == VIO_SUBTYPE_NACK)
err = vdc_nack(port, &msgbuf);
else
err = vdc_handle_unknown(port, &msgbuf);
} else if (msgbuf.tag.type == VIO_TYPE_CTRL) {
err = vio_control_pkt_engine(vio, &msgbuf);
} else {
err = vdc_handle_unknown(port, &msgbuf);
}
if (err < 0)
break;
}
if (err < 0)
vdc_finish(&port->vio, err, WAITING_FOR_ANY);
spin_unlock_irqrestore(&vio->lock, flags);
}
static int __vdc_tx_trigger(struct vdc_port *port)
{
struct vio_dring_state *dr = &port->vio.drings[VIO_DRIVER_TX_RING];
struct vio_dring_data hdr = {
.tag = {
.type = VIO_TYPE_DATA,
.stype = VIO_SUBTYPE_INFO,
.stype_env = VIO_DRING_DATA,
.sid = vio_send_sid(&port->vio),
},
.dring_ident = dr->ident,
.start_idx = dr->prod,
.end_idx = dr->prod,
};
int err, delay;
hdr.seq = dr->snd_nxt;
delay = 1;
do {
err = vio_ldc_send(&port->vio, &hdr, sizeof(hdr));
if (err > 0) {
dr->snd_nxt++;
break;
}
udelay(delay);
if ((delay <<= 1) > 128)
delay = 128;
} while (err == -EAGAIN);
return err;
}
static int __send_request(struct request *req)
{
struct vdc_port *port = req->rq_disk->private_data;
struct vio_dring_state *dr = &port->vio.drings[VIO_DRIVER_TX_RING];
struct scatterlist sg[port->ring_cookies];
struct vdc_req_entry *rqe;
struct vio_disk_desc *desc;
unsigned int map_perm;
int nsg, err, i;
u64 len;
u8 op;
map_perm = LDC_MAP_SHADOW | LDC_MAP_DIRECT | LDC_MAP_IO;
if (rq_data_dir(req) == READ) {
map_perm |= LDC_MAP_W;
op = VD_OP_BREAD;
} else {
map_perm |= LDC_MAP_R;
op = VD_OP_BWRITE;
}
sg_init_table(sg, port->ring_cookies);
nsg = blk_rq_map_sg(req->q, req, sg);
len = 0;
for (i = 0; i < nsg; i++)
len += sg[i].length;
if (unlikely(vdc_tx_dring_avail(dr) < 1)) {
blk_stop_queue(port->disk->queue);
err = -ENOMEM;
goto out;
}
desc = vio_dring_cur(dr);
err = ldc_map_sg(port->vio.lp, sg, nsg,
desc->cookies, port->ring_cookies,
map_perm);
if (err < 0) {
printk(KERN_ERR PFX "ldc_map_sg() failure, err=%d.\n", err);
return err;
}
rqe = &port->rq_arr[dr->prod];
rqe->req = req;
desc->hdr.ack = VIO_ACK_ENABLE;
desc->req_id = port->req_id;
desc->operation = op;
if (port->vdisk_type == VD_DISK_TYPE_DISK) {
desc->slice = 0xff;
} else {
desc->slice = 0;
}
desc->status = ~0;
desc->offset = (blk_rq_pos(req) << 9) / port->vdisk_block_size;
desc->size = len;
desc->ncookies = err;
/* This has to be a non-SMP write barrier because we are writing
* to memory which is shared with the peer LDOM.
*/
wmb();
desc->hdr.state = VIO_DESC_READY;
err = __vdc_tx_trigger(port);
if (err < 0) {
printk(KERN_ERR PFX "vdc_tx_trigger() failure, err=%d\n", err);
} else {
port->req_id++;
dr->prod = (dr->prod + 1) & (VDC_TX_RING_SIZE - 1);
}
out:
return err;
}
static void do_vdc_request(struct request_queue *q)
{
while (1) {
struct request *req = blk_fetch_request(q);
if (!req)
break;
if (__send_request(req) < 0)
__blk_end_request_all(req, -EIO);
}
}
static int generic_request(struct vdc_port *port, u8 op, void *buf, int len)
{
struct vio_dring_state *dr;
struct vio_completion comp;
struct vio_disk_desc *desc;
unsigned int map_perm;
unsigned long flags;
int op_len, err;
void *req_buf;
if (!(((u64)1 << (u64)op) & port->operations))
return -EOPNOTSUPP;
switch (op) {
case VD_OP_BREAD:
case VD_OP_BWRITE:
default:
return -EINVAL;
case VD_OP_FLUSH:
op_len = 0;
map_perm = 0;
break;
case VD_OP_GET_WCE:
op_len = sizeof(u32);
map_perm = LDC_MAP_W;
break;
case VD_OP_SET_WCE:
op_len = sizeof(u32);
map_perm = LDC_MAP_R;
break;
case VD_OP_GET_VTOC:
op_len = sizeof(struct vio_disk_vtoc);
map_perm = LDC_MAP_W;
break;
case VD_OP_SET_VTOC:
op_len = sizeof(struct vio_disk_vtoc);
map_perm = LDC_MAP_R;
break;
case VD_OP_GET_DISKGEOM:
op_len = sizeof(struct vio_disk_geom);
map_perm = LDC_MAP_W;
break;
case VD_OP_SET_DISKGEOM:
op_len = sizeof(struct vio_disk_geom);
map_perm = LDC_MAP_R;
break;
case VD_OP_SCSICMD:
op_len = 16;
map_perm = LDC_MAP_RW;
break;
case VD_OP_GET_DEVID:
op_len = sizeof(struct vio_disk_devid);
map_perm = LDC_MAP_W;
break;
case VD_OP_GET_EFI:
case VD_OP_SET_EFI:
return -EOPNOTSUPP;
break;
};
map_perm |= LDC_MAP_SHADOW | LDC_MAP_DIRECT | LDC_MAP_IO;
op_len = (op_len + 7) & ~7;
req_buf = kzalloc(op_len, GFP_KERNEL);
if (!req_buf)
return -ENOMEM;
if (len > op_len)
len = op_len;
if (map_perm & LDC_MAP_R)
memcpy(req_buf, buf, len);
spin_lock_irqsave(&port->vio.lock, flags);
dr = &port->vio.drings[VIO_DRIVER_TX_RING];
/* XXX If we want to use this code generically we have to
* XXX handle TX ring exhaustion etc.
*/
desc = vio_dring_cur(dr);
err = ldc_map_single(port->vio.lp, req_buf, op_len,
desc->cookies, port->ring_cookies,
map_perm);
if (err < 0) {
spin_unlock_irqrestore(&port->vio.lock, flags);
kfree(req_buf);
return err;
}
init_completion(&comp.com);
comp.waiting_for = WAITING_FOR_GEN_CMD;
port->vio.cmp = ∁
desc->hdr.ack = VIO_ACK_ENABLE;
desc->req_id = port->req_id;
desc->operation = op;
desc->slice = 0;
desc->status = ~0;
desc->offset = 0;
desc->size = op_len;
desc->ncookies = err;
/* This has to be a non-SMP write barrier because we are writing
* to memory which is shared with the peer LDOM.
*/
wmb();
desc->hdr.state = VIO_DESC_READY;
err = __vdc_tx_trigger(port);
if (err >= 0) {
port->req_id++;
dr->prod = (dr->prod + 1) & (VDC_TX_RING_SIZE - 1);
spin_unlock_irqrestore(&port->vio.lock, flags);
wait_for_completion(&comp.com);
err = comp.err;
} else {
port->vio.cmp = NULL;
spin_unlock_irqrestore(&port->vio.lock, flags);
}
if (map_perm & LDC_MAP_W)
memcpy(buf, req_buf, len);
kfree(req_buf);
return err;
}
static int __devinit vdc_alloc_tx_ring(struct vdc_port *port)
{
struct vio_dring_state *dr = &port->vio.drings[VIO_DRIVER_TX_RING];
unsigned long len, entry_size;
int ncookies;
void *dring;
entry_size = sizeof(struct vio_disk_desc) +
(sizeof(struct ldc_trans_cookie) * port->ring_cookies);
len = (VDC_TX_RING_SIZE * entry_size);
ncookies = VIO_MAX_RING_COOKIES;
dring = ldc_alloc_exp_dring(port->vio.lp, len,
dr->cookies, &ncookies,
(LDC_MAP_SHADOW |
LDC_MAP_DIRECT |
LDC_MAP_RW));
if (IS_ERR(dring))
return PTR_ERR(dring);
dr->base = dring;
dr->entry_size = entry_size;
dr->num_entries = VDC_TX_RING_SIZE;
dr->prod = dr->cons = 0;
dr->pending = VDC_TX_RING_SIZE;
dr->ncookies = ncookies;
return 0;
}
static void vdc_free_tx_ring(struct vdc_port *port)
{
struct vio_dring_state *dr = &port->vio.drings[VIO_DRIVER_TX_RING];
if (dr->base) {
ldc_free_exp_dring(port->vio.lp, dr->base,
(dr->entry_size * dr->num_entries),
dr->cookies, dr->ncookies);
dr->base = NULL;
dr->entry_size = 0;
dr->num_entries = 0;
dr->pending = 0;
dr->ncookies = 0;
}
}
static int probe_disk(struct vdc_port *port)
{
struct vio_completion comp;
struct request_queue *q;
struct gendisk *g;
int err;
init_completion(&comp.com);
comp.err = 0;
comp.waiting_for = WAITING_FOR_LINK_UP;
port->vio.cmp = ∁
vio_port_up(&port->vio);
wait_for_completion(&comp.com);
if (comp.err)
return comp.err;
err = generic_request(port, VD_OP_GET_VTOC,
&port->label, sizeof(port->label));
if (err < 0) {
printk(KERN_ERR PFX "VD_OP_GET_VTOC returns error %d\n", err);
return err;
}
err = generic_request(port, VD_OP_GET_DISKGEOM,
&port->geom, sizeof(port->geom));
if (err < 0) {
printk(KERN_ERR PFX "VD_OP_GET_DISKGEOM returns "
"error %d\n", err);
return err;
}
port->vdisk_size = ((u64)port->geom.num_cyl *
(u64)port->geom.num_hd *
(u64)port->geom.num_sec);
q = blk_init_queue(do_vdc_request, &port->vio.lock);
if (!q) {
printk(KERN_ERR PFX "%s: Could not allocate queue.\n",
port->vio.name);
return -ENOMEM;
}
g = alloc_disk(1 << PARTITION_SHIFT);
if (!g) {
printk(KERN_ERR PFX "%s: Could not allocate gendisk.\n",
port->vio.name);
blk_cleanup_queue(q);
return -ENOMEM;
}
port->disk = g;
blk_queue_max_segments(q, port->ring_cookies);
blk_queue_max_hw_sectors(q, port->max_xfer_size);
g->major = vdc_major;
g->first_minor = port->vio.vdev->dev_no << PARTITION_SHIFT;
strcpy(g->disk_name, port->disk_name);
g->fops = &vdc_fops;
g->queue = q;
g->private_data = port;
g->driverfs_dev = &port->vio.vdev->dev;
set_capacity(g, port->vdisk_size);
printk(KERN_INFO PFX "%s: %u sectors (%u MB)\n",
g->disk_name,
port->vdisk_size, (port->vdisk_size >> (20 - 9)));
add_disk(g);
return 0;
}
static struct ldc_channel_config vdc_ldc_cfg = {
.event = vdc_event,
.mtu = 64,
.mode = LDC_MODE_UNRELIABLE,
};
static struct vio_driver_ops vdc_vio_ops = {
.send_attr = vdc_send_attr,
.handle_attr = vdc_handle_attr,
.handshake_complete = vdc_handshake_complete,
};
static void __devinit print_version(void)
{
static int version_printed;
if (version_printed++ == 0)
printk(KERN_INFO "%s", version);
}
static int __devinit vdc_port_probe(struct vio_dev *vdev,
const struct vio_device_id *id)
{
struct mdesc_handle *hp;
struct vdc_port *port;
int err;
print_version();
hp = mdesc_grab();
err = -ENODEV;
if ((vdev->dev_no << PARTITION_SHIFT) & ~(u64)MINORMASK) {
printk(KERN_ERR PFX "Port id [%llu] too large.\n",
vdev->dev_no);
goto err_out_release_mdesc;
}
port = kzalloc(sizeof(*port), GFP_KERNEL);
err = -ENOMEM;
if (!port) {
printk(KERN_ERR PFX "Cannot allocate vdc_port.\n");
goto err_out_release_mdesc;
}
if (vdev->dev_no >= 26)
snprintf(port->disk_name, sizeof(port->disk_name),
VDCBLK_NAME "%c%c",
'a' + ((int)vdev->dev_no / 26) - 1,
'a' + ((int)vdev->dev_no % 26));
else
snprintf(port->disk_name, sizeof(port->disk_name),
VDCBLK_NAME "%c", 'a' + ((int)vdev->dev_no % 26));
err = vio_driver_init(&port->vio, vdev, VDEV_DISK,
vdc_versions, ARRAY_SIZE(vdc_versions),
&vdc_vio_ops, port->disk_name);
if (err)
goto err_out_free_port;
port->vdisk_block_size = 512;
port->max_xfer_size = ((128 * 1024) / port->vdisk_block_size);
port->ring_cookies = ((port->max_xfer_size *
port->vdisk_block_size) / PAGE_SIZE) + 2;
err = vio_ldc_alloc(&port->vio, &vdc_ldc_cfg, port);
if (err)
goto err_out_free_port;
err = vdc_alloc_tx_ring(port);
if (err)
goto err_out_free_ldc;
err = probe_disk(port);
if (err)
goto err_out_free_tx_ring;
dev_set_drvdata(&vdev->dev, port);
mdesc_release(hp);
return 0;
err_out_free_tx_ring:
vdc_free_tx_ring(port);
err_out_free_ldc:
vio_ldc_free(&port->vio);
err_out_free_port:
kfree(port);
err_out_release_mdesc:
mdesc_release(hp);
return err;
}
static int vdc_port_remove(struct vio_dev *vdev)
{
struct vdc_port *port = dev_get_drvdata(&vdev->dev);
if (port) {
del_timer_sync(&port->vio.timer);
vdc_free_tx_ring(port);
vio_ldc_free(&port->vio);
dev_set_drvdata(&vdev->dev, NULL);
kfree(port);
}
return 0;
}
static const struct vio_device_id vdc_port_match[] = {
{
.type = "vdc-port",
},
{},
};
MODULE_DEVICE_TABLE(vio, vdc_port_match);
static struct vio_driver vdc_port_driver = {
.id_table = vdc_port_match,
.probe = vdc_port_probe,
.remove = vdc_port_remove,
.name = "vdc_port",
};
static int __init vdc_init(void)
{
int err;
err = register_blkdev(0, VDCBLK_NAME);
if (err < 0)
goto out_err;
vdc_major = err;
err = vio_register_driver(&vdc_port_driver);
if (err)
goto out_unregister_blkdev;
return 0;
out_unregister_blkdev:
unregister_blkdev(vdc_major, VDCBLK_NAME);
vdc_major = 0;
out_err:
return err;
}
static void __exit vdc_exit(void)
{
vio_unregister_driver(&vdc_port_driver);
unregister_blkdev(vdc_major, VDCBLK_NAME);
}
module_init(vdc_init);
module_exit(vdc_exit);