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OpenCloudOS-Kernel/drivers/block/nbd.c

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/*
* Network block device - make block devices work over TCP
*
* Note that you can not swap over this thing, yet. Seems to work but
* deadlocks sometimes - you can not swap over TCP in general.
*
* Copyright 1997-2000, 2008 Pavel Machek <pavel@ucw.cz>
* Parts copyright 2001 Steven Whitehouse <steve@chygwyn.com>
*
* This file is released under GPLv2 or later.
*
* (part of code stolen from loop.c)
*/
#include <linux/major.h>
#include <linux/blkdev.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/fs.h>
#include <linux/bio.h>
#include <linux/stat.h>
#include <linux/errno.h>
#include <linux/file.h>
#include <linux/ioctl.h>
#include <linux/mutex.h>
#include <linux/compiler.h>
#include <linux/err.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <net/sock.h>
#include <linux/net.h>
#include <linux/kthread.h>
#include <asm/uaccess.h>
#include <asm/types.h>
#include <linux/nbd.h>
#define NBD_MAGIC 0x68797548
#ifdef NDEBUG
#define dprintk(flags, fmt...)
#else /* NDEBUG */
#define dprintk(flags, fmt...) do { \
if (debugflags & (flags)) printk(KERN_DEBUG fmt); \
} while (0)
#define DBG_IOCTL 0x0004
#define DBG_INIT 0x0010
#define DBG_EXIT 0x0020
#define DBG_BLKDEV 0x0100
#define DBG_RX 0x0200
#define DBG_TX 0x0400
static unsigned int debugflags;
#endif /* NDEBUG */
static unsigned int nbds_max = 16;
static struct nbd_device *nbd_dev;
static int max_part;
/*
* Use just one lock (or at most 1 per NIC). Two arguments for this:
* 1. Each NIC is essentially a synchronization point for all servers
* accessed through that NIC so there's no need to have more locks
* than NICs anyway.
* 2. More locks lead to more "Dirty cache line bouncing" which will slow
* down each lock to the point where they're actually slower than just
* a single lock.
* Thanks go to Jens Axboe and Al Viro for their LKML emails explaining this!
*/
static DEFINE_SPINLOCK(nbd_lock);
#ifndef NDEBUG
static const char *ioctl_cmd_to_ascii(int cmd)
{
switch (cmd) {
case NBD_SET_SOCK: return "set-sock";
case NBD_SET_BLKSIZE: return "set-blksize";
case NBD_SET_SIZE: return "set-size";
case NBD_DO_IT: return "do-it";
case NBD_CLEAR_SOCK: return "clear-sock";
case NBD_CLEAR_QUE: return "clear-que";
case NBD_PRINT_DEBUG: return "print-debug";
case NBD_SET_SIZE_BLOCKS: return "set-size-blocks";
case NBD_DISCONNECT: return "disconnect";
case BLKROSET: return "set-read-only";
case BLKFLSBUF: return "flush-buffer-cache";
}
return "unknown";
}
static const char *nbdcmd_to_ascii(int cmd)
{
switch (cmd) {
case NBD_CMD_READ: return "read";
case NBD_CMD_WRITE: return "write";
case NBD_CMD_DISC: return "disconnect";
}
return "invalid";
}
#endif /* NDEBUG */
static void nbd_end_request(struct request *req)
{
int error = req->errors ? -EIO : 0;
struct request_queue *q = req->q;
unsigned long flags;
dprintk(DBG_BLKDEV, "%s: request %p: %s\n", req->rq_disk->disk_name,
req, error ? "failed" : "done");
spin_lock_irqsave(q->queue_lock, flags);
__blk_end_request_all(req, error);
spin_unlock_irqrestore(q->queue_lock, flags);
}
static void sock_shutdown(struct nbd_device *nbd, int lock)
{
/* Forcibly shutdown the socket causing all listeners
* to error
*
* FIXME: This code is duplicated from sys_shutdown, but
* there should be a more generic interface rather than
* calling socket ops directly here */
if (lock)
mutex_lock(&nbd->tx_lock);
if (nbd->sock) {
dev_warn(disk_to_dev(nbd->disk), "shutting down socket\n");
kernel_sock_shutdown(nbd->sock, SHUT_RDWR);
nbd->sock = NULL;
}
if (lock)
mutex_unlock(&nbd->tx_lock);
}
static void nbd_xmit_timeout(unsigned long arg)
{
struct task_struct *task = (struct task_struct *)arg;
printk(KERN_WARNING "nbd: killing hung xmit (%s, pid: %d)\n",
task->comm, task->pid);
force_sig(SIGKILL, task);
}
/*
* Send or receive packet.
*/
static int sock_xmit(struct nbd_device *nbd, int send, void *buf, int size,
int msg_flags)
{
struct socket *sock = nbd->sock;
int result;
struct msghdr msg;
struct kvec iov;
sigset_t blocked, oldset;
if (unlikely(!sock)) {
dev_err(disk_to_dev(nbd->disk),
"Attempted %s on closed socket in sock_xmit\n",
(send ? "send" : "recv"));
return -EINVAL;
}
/* Allow interception of SIGKILL only
* Don't allow other signals to interrupt the transmission */
siginitsetinv(&blocked, sigmask(SIGKILL));
sigprocmask(SIG_SETMASK, &blocked, &oldset);
do {
sock->sk->sk_allocation = GFP_NOIO;
iov.iov_base = buf;
iov.iov_len = size;
msg.msg_name = NULL;
msg.msg_namelen = 0;
msg.msg_control = NULL;
msg.msg_controllen = 0;
msg.msg_flags = msg_flags | MSG_NOSIGNAL;
if (send) {
struct timer_list ti;
if (nbd->xmit_timeout) {
init_timer(&ti);
ti.function = nbd_xmit_timeout;
ti.data = (unsigned long)current;
ti.expires = jiffies + nbd->xmit_timeout;
add_timer(&ti);
}
result = kernel_sendmsg(sock, &msg, &iov, 1, size);
if (nbd->xmit_timeout)
del_timer_sync(&ti);
} else
result = kernel_recvmsg(sock, &msg, &iov, 1, size,
msg.msg_flags);
if (signal_pending(current)) {
siginfo_t info;
printk(KERN_WARNING "nbd (pid %d: %s) got signal %d\n",
task_pid_nr(current), current->comm,
dequeue_signal_lock(current, &current->blocked, &info));
result = -EINTR;
sock_shutdown(nbd, !send);
break;
}
if (result <= 0) {
if (result == 0)
result = -EPIPE; /* short read */
break;
}
size -= result;
buf += result;
} while (size > 0);
sigprocmask(SIG_SETMASK, &oldset, NULL);
return result;
}
static inline int sock_send_bvec(struct nbd_device *nbd, struct bio_vec *bvec,
int flags)
{
int result;
void *kaddr = kmap(bvec->bv_page);
result = sock_xmit(nbd, 1, kaddr + bvec->bv_offset,
bvec->bv_len, flags);
kunmap(bvec->bv_page);
return result;
}
/* always call with the tx_lock held */
static int nbd_send_req(struct nbd_device *nbd, struct request *req)
{
int result, flags;
struct nbd_request request;
unsigned long size = blk_rq_bytes(req);
request.magic = htonl(NBD_REQUEST_MAGIC);
request.type = htonl(nbd_cmd(req));
request.from = cpu_to_be64((u64)blk_rq_pos(req) << 9);
request.len = htonl(size);
memcpy(request.handle, &req, sizeof(req));
dprintk(DBG_TX, "%s: request %p: sending control (%s@%llu,%uB)\n",
nbd->disk->disk_name, req,
nbdcmd_to_ascii(nbd_cmd(req)),
(unsigned long long)blk_rq_pos(req) << 9,
blk_rq_bytes(req));
result = sock_xmit(nbd, 1, &request, sizeof(request),
(nbd_cmd(req) == NBD_CMD_WRITE) ? MSG_MORE : 0);
if (result <= 0) {
dev_err(disk_to_dev(nbd->disk),
"Send control failed (result %d)\n", result);
goto error_out;
}
if (nbd_cmd(req) == NBD_CMD_WRITE) {
struct req_iterator iter;
struct bio_vec *bvec;
/*
* we are really probing at internals to determine
* whether to set MSG_MORE or not...
*/
rq_for_each_segment(bvec, req, iter) {
flags = 0;
if (!rq_iter_last(req, iter))
flags = MSG_MORE;
dprintk(DBG_TX, "%s: request %p: sending %d bytes data\n",
nbd->disk->disk_name, req, bvec->bv_len);
result = sock_send_bvec(nbd, bvec, flags);
if (result <= 0) {
dev_err(disk_to_dev(nbd->disk),
"Send data failed (result %d)\n",
result);
goto error_out;
}
}
}
return 0;
error_out:
return -EIO;
}
static struct request *nbd_find_request(struct nbd_device *nbd,
struct request *xreq)
{
struct request *req, *tmp;
int err;
err = wait_event_interruptible(nbd->active_wq, nbd->active_req != xreq);
if (unlikely(err))
goto out;
spin_lock(&nbd->queue_lock);
list_for_each_entry_safe(req, tmp, &nbd->queue_head, queuelist) {
if (req != xreq)
continue;
list_del_init(&req->queuelist);
spin_unlock(&nbd->queue_lock);
return req;
}
spin_unlock(&nbd->queue_lock);
err = -ENOENT;
out:
return ERR_PTR(err);
}
static inline int sock_recv_bvec(struct nbd_device *nbd, struct bio_vec *bvec)
{
int result;
void *kaddr = kmap(bvec->bv_page);
result = sock_xmit(nbd, 0, kaddr + bvec->bv_offset, bvec->bv_len,
MSG_WAITALL);
kunmap(bvec->bv_page);
return result;
}
/* NULL returned = something went wrong, inform userspace */
static struct request *nbd_read_stat(struct nbd_device *nbd)
{
int result;
struct nbd_reply reply;
struct request *req;
reply.magic = 0;
result = sock_xmit(nbd, 0, &reply, sizeof(reply), MSG_WAITALL);
if (result <= 0) {
dev_err(disk_to_dev(nbd->disk),
"Receive control failed (result %d)\n", result);
goto harderror;
}
if (ntohl(reply.magic) != NBD_REPLY_MAGIC) {
dev_err(disk_to_dev(nbd->disk), "Wrong magic (0x%lx)\n",
(unsigned long)ntohl(reply.magic));
result = -EPROTO;
goto harderror;
}
req = nbd_find_request(nbd, *(struct request **)reply.handle);
if (IS_ERR(req)) {
result = PTR_ERR(req);
if (result != -ENOENT)
goto harderror;
dev_err(disk_to_dev(nbd->disk), "Unexpected reply (%p)\n",
reply.handle);
result = -EBADR;
goto harderror;
}
if (ntohl(reply.error)) {
dev_err(disk_to_dev(nbd->disk), "Other side returned error (%d)\n",
ntohl(reply.error));
req->errors++;
return req;
}
dprintk(DBG_RX, "%s: request %p: got reply\n",
nbd->disk->disk_name, req);
if (nbd_cmd(req) == NBD_CMD_READ) {
struct req_iterator iter;
struct bio_vec *bvec;
rq_for_each_segment(bvec, req, iter) {
result = sock_recv_bvec(nbd, bvec);
if (result <= 0) {
dev_err(disk_to_dev(nbd->disk), "Receive data failed (result %d)\n",
result);
req->errors++;
return req;
}
dprintk(DBG_RX, "%s: request %p: got %d bytes data\n",
nbd->disk->disk_name, req, bvec->bv_len);
}
}
return req;
harderror:
nbd->harderror = result;
return NULL;
}
static ssize_t pid_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
struct gendisk *disk = dev_to_disk(dev);
return sprintf(buf, "%ld\n",
(long) ((struct nbd_device *)disk->private_data)->pid);
}
static struct device_attribute pid_attr = {
.attr = { .name = "pid", .mode = S_IRUGO},
.show = pid_show,
};
static int nbd_do_it(struct nbd_device *nbd)
{
struct request *req;
int ret;
BUG_ON(nbd->magic != NBD_MAGIC);
nbd->pid = task_pid_nr(current);
ret = device_create_file(disk_to_dev(nbd->disk), &pid_attr);
if (ret) {
dev_err(disk_to_dev(nbd->disk), "device_create_file failed!\n");
nbd->pid = 0;
return ret;
}
while ((req = nbd_read_stat(nbd)) != NULL)
nbd_end_request(req);
device_remove_file(disk_to_dev(nbd->disk), &pid_attr);
nbd->pid = 0;
return 0;
}
static void nbd_clear_que(struct nbd_device *nbd)
{
struct request *req;
BUG_ON(nbd->magic != NBD_MAGIC);
/*
* Because we have set nbd->sock to NULL under the tx_lock, all
* modifications to the list must have completed by now. For
* the same reason, the active_req must be NULL.
*
* As a consequence, we don't need to take the spin lock while
* purging the list here.
*/
BUG_ON(nbd->sock);
BUG_ON(nbd->active_req);
while (!list_empty(&nbd->queue_head)) {
req = list_entry(nbd->queue_head.next, struct request,
queuelist);
list_del_init(&req->queuelist);
req->errors++;
nbd_end_request(req);
}
}
static void nbd_handle_req(struct nbd_device *nbd, struct request *req)
{
if (req->cmd_type != REQ_TYPE_FS)
goto error_out;
nbd_cmd(req) = NBD_CMD_READ;
if (rq_data_dir(req) == WRITE) {
nbd_cmd(req) = NBD_CMD_WRITE;
if (nbd->flags & NBD_READ_ONLY) {
dev_err(disk_to_dev(nbd->disk),
"Write on read-only\n");
goto error_out;
}
}
req->errors = 0;
mutex_lock(&nbd->tx_lock);
if (unlikely(!nbd->sock)) {
mutex_unlock(&nbd->tx_lock);
dev_err(disk_to_dev(nbd->disk),
"Attempted send on closed socket\n");
goto error_out;
}
nbd->active_req = req;
if (nbd_send_req(nbd, req) != 0) {
dev_err(disk_to_dev(nbd->disk), "Request send failed\n");
req->errors++;
nbd_end_request(req);
} else {
spin_lock(&nbd->queue_lock);
list_add(&req->queuelist, &nbd->queue_head);
spin_unlock(&nbd->queue_lock);
}
nbd->active_req = NULL;
mutex_unlock(&nbd->tx_lock);
wake_up_all(&nbd->active_wq);
return;
error_out:
req->errors++;
nbd_end_request(req);
}
static int nbd_thread(void *data)
{
struct nbd_device *nbd = data;
struct request *req;
set_user_nice(current, -20);
while (!kthread_should_stop() || !list_empty(&nbd->waiting_queue)) {
/* wait for something to do */
wait_event_interruptible(nbd->waiting_wq,
kthread_should_stop() ||
!list_empty(&nbd->waiting_queue));
/* extract request */
if (list_empty(&nbd->waiting_queue))
continue;
spin_lock_irq(&nbd->queue_lock);
req = list_entry(nbd->waiting_queue.next, struct request,
queuelist);
list_del_init(&req->queuelist);
spin_unlock_irq(&nbd->queue_lock);
/* handle request */
nbd_handle_req(nbd, req);
}
return 0;
}
/*
* We always wait for result of write, for now. It would be nice to make it optional
* in future
* if ((rq_data_dir(req) == WRITE) && (nbd->flags & NBD_WRITE_NOCHK))
* { printk( "Warning: Ignoring result!\n"); nbd_end_request( req ); }
*/
static void do_nbd_request(struct request_queue *q)
{
struct request *req;
while ((req = blk_fetch_request(q)) != NULL) {
struct nbd_device *nbd;
spin_unlock_irq(q->queue_lock);
dprintk(DBG_BLKDEV, "%s: request %p: dequeued (flags=%x)\n",
req->rq_disk->disk_name, req, req->cmd_type);
nbd = req->rq_disk->private_data;
BUG_ON(nbd->magic != NBD_MAGIC);
if (unlikely(!nbd->sock)) {
dev_err(disk_to_dev(nbd->disk),
"Attempted send on closed socket\n");
req->errors++;
nbd_end_request(req);
spin_lock_irq(q->queue_lock);
continue;
}
spin_lock_irq(&nbd->queue_lock);
list_add_tail(&req->queuelist, &nbd->waiting_queue);
spin_unlock_irq(&nbd->queue_lock);
wake_up(&nbd->waiting_wq);
spin_lock_irq(q->queue_lock);
}
}
/* Must be called with tx_lock held */
static int __nbd_ioctl(struct block_device *bdev, struct nbd_device *nbd,
unsigned int cmd, unsigned long arg)
{
switch (cmd) {
case NBD_DISCONNECT: {
struct request sreq;
dev_info(disk_to_dev(nbd->disk), "NBD_DISCONNECT\n");
blk_rq_init(NULL, &sreq);
sreq.cmd_type = REQ_TYPE_SPECIAL;
nbd_cmd(&sreq) = NBD_CMD_DISC;
if (!nbd->sock)
return -EINVAL;
nbd_send_req(nbd, &sreq);
return 0;
}
case NBD_CLEAR_SOCK: {
struct file *file;
nbd->sock = NULL;
file = nbd->file;
nbd->file = NULL;
nbd_clear_que(nbd);
BUG_ON(!list_empty(&nbd->queue_head));
if (file)
fput(file);
return 0;
}
case NBD_SET_SOCK: {
struct file *file;
if (nbd->file)
return -EBUSY;
file = fget(arg);
if (file) {
struct inode *inode = file->f_path.dentry->d_inode;
if (S_ISSOCK(inode->i_mode)) {
nbd->file = file;
nbd->sock = SOCKET_I(inode);
if (max_part > 0)
bdev->bd_invalidated = 1;
return 0;
} else {
fput(file);
}
}
return -EINVAL;
}
case NBD_SET_BLKSIZE:
nbd->blksize = arg;
nbd->bytesize &= ~(nbd->blksize-1);
bdev->bd_inode->i_size = nbd->bytesize;
set_blocksize(bdev, nbd->blksize);
set_capacity(nbd->disk, nbd->bytesize >> 9);
return 0;
case NBD_SET_SIZE:
nbd->bytesize = arg & ~(nbd->blksize-1);
bdev->bd_inode->i_size = nbd->bytesize;
set_blocksize(bdev, nbd->blksize);
set_capacity(nbd->disk, nbd->bytesize >> 9);
return 0;
case NBD_SET_TIMEOUT:
nbd->xmit_timeout = arg * HZ;
return 0;
case NBD_SET_SIZE_BLOCKS:
nbd->bytesize = ((u64) arg) * nbd->blksize;
bdev->bd_inode->i_size = nbd->bytesize;
set_blocksize(bdev, nbd->blksize);
set_capacity(nbd->disk, nbd->bytesize >> 9);
return 0;
case NBD_DO_IT: {
struct task_struct *thread;
struct file *file;
int error;
if (nbd->pid)
return -EBUSY;
if (!nbd->file)
return -EINVAL;
mutex_unlock(&nbd->tx_lock);
thread = kthread_create(nbd_thread, nbd, nbd->disk->disk_name);
if (IS_ERR(thread)) {
mutex_lock(&nbd->tx_lock);
return PTR_ERR(thread);
}
wake_up_process(thread);
error = nbd_do_it(nbd);
kthread_stop(thread);
mutex_lock(&nbd->tx_lock);
if (error)
return error;
sock_shutdown(nbd, 0);
file = nbd->file;
nbd->file = NULL;
nbd_clear_que(nbd);
dev_warn(disk_to_dev(nbd->disk), "queue cleared\n");
if (file)
fput(file);
nbd->bytesize = 0;
bdev->bd_inode->i_size = 0;
set_capacity(nbd->disk, 0);
if (max_part > 0)
ioctl_by_bdev(bdev, BLKRRPART, 0);
return nbd->harderror;
}
case NBD_CLEAR_QUE:
/*
* This is for compatibility only. The queue is always cleared
* by NBD_DO_IT or NBD_CLEAR_SOCK.
*/
BUG_ON(!nbd->sock && !list_empty(&nbd->queue_head));
return 0;
case NBD_PRINT_DEBUG:
dev_info(disk_to_dev(nbd->disk),
"next = %p, prev = %p, head = %p\n",
nbd->queue_head.next, nbd->queue_head.prev,
&nbd->queue_head);
return 0;
}
return -ENOTTY;
}
static int nbd_ioctl(struct block_device *bdev, fmode_t mode,
unsigned int cmd, unsigned long arg)
{
struct nbd_device *nbd = bdev->bd_disk->private_data;
int error;
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
BUG_ON(nbd->magic != NBD_MAGIC);
/* Anyone capable of this syscall can do *real bad* things */
dprintk(DBG_IOCTL, "%s: nbd_ioctl cmd=%s(0x%x) arg=%lu\n",
nbd->disk->disk_name, ioctl_cmd_to_ascii(cmd), cmd, arg);
mutex_lock(&nbd->tx_lock);
error = __nbd_ioctl(bdev, nbd, cmd, arg);
mutex_unlock(&nbd->tx_lock);
return error;
}
static const struct block_device_operations nbd_fops =
{
.owner = THIS_MODULE,
.ioctl = nbd_ioctl,
};
/*
* And here should be modules and kernel interface
* (Just smiley confuses emacs :-)
*/
static int __init nbd_init(void)
{
int err = -ENOMEM;
int i;
int part_shift;
BUILD_BUG_ON(sizeof(struct nbd_request) != 28);
if (max_part < 0) {
printk(KERN_ERR "nbd: max_part must be >= 0\n");
return -EINVAL;
}
nbd_dev = kcalloc(nbds_max, sizeof(*nbd_dev), GFP_KERNEL);
if (!nbd_dev)
return -ENOMEM;
part_shift = 0;
if (max_part > 0) {
part_shift = fls(max_part);
/*
* Adjust max_part according to part_shift as it is exported
* to user space so that user can know the max number of
* partition kernel should be able to manage.
*
* Note that -1 is required because partition 0 is reserved
* for the whole disk.
*/
max_part = (1UL << part_shift) - 1;
}
if ((1UL << part_shift) > DISK_MAX_PARTS)
return -EINVAL;
if (nbds_max > 1UL << (MINORBITS - part_shift))
return -EINVAL;
for (i = 0; i < nbds_max; i++) {
struct gendisk *disk = alloc_disk(1 << part_shift);
if (!disk)
goto out;
nbd_dev[i].disk = disk;
/*
* The new linux 2.5 block layer implementation requires
* every gendisk to have its very own request_queue struct.
* These structs are big so we dynamically allocate them.
*/
disk->queue = blk_init_queue(do_nbd_request, &nbd_lock);
if (!disk->queue) {
put_disk(disk);
goto out;
}
/*
* Tell the block layer that we are not a rotational device
*/
queue_flag_set_unlocked(QUEUE_FLAG_NONROT, disk->queue);
}
if (register_blkdev(NBD_MAJOR, "nbd")) {
err = -EIO;
goto out;
}
printk(KERN_INFO "nbd: registered device at major %d\n", NBD_MAJOR);
dprintk(DBG_INIT, "nbd: debugflags=0x%x\n", debugflags);
for (i = 0; i < nbds_max; i++) {
struct gendisk *disk = nbd_dev[i].disk;
nbd_dev[i].file = NULL;
nbd_dev[i].magic = NBD_MAGIC;
nbd_dev[i].flags = 0;
INIT_LIST_HEAD(&nbd_dev[i].waiting_queue);
spin_lock_init(&nbd_dev[i].queue_lock);
INIT_LIST_HEAD(&nbd_dev[i].queue_head);
mutex_init(&nbd_dev[i].tx_lock);
init_waitqueue_head(&nbd_dev[i].active_wq);
init_waitqueue_head(&nbd_dev[i].waiting_wq);
nbd_dev[i].blksize = 1024;
nbd_dev[i].bytesize = 0;
disk->major = NBD_MAJOR;
disk->first_minor = i << part_shift;
disk->fops = &nbd_fops;
disk->private_data = &nbd_dev[i];
sprintf(disk->disk_name, "nbd%d", i);
set_capacity(disk, 0);
add_disk(disk);
}
return 0;
out:
while (i--) {
blk_cleanup_queue(nbd_dev[i].disk->queue);
put_disk(nbd_dev[i].disk);
}
kfree(nbd_dev);
return err;
}
static void __exit nbd_cleanup(void)
{
int i;
for (i = 0; i < nbds_max; i++) {
struct gendisk *disk = nbd_dev[i].disk;
nbd_dev[i].magic = 0;
if (disk) {
del_gendisk(disk);
blk_cleanup_queue(disk->queue);
put_disk(disk);
}
}
unregister_blkdev(NBD_MAJOR, "nbd");
kfree(nbd_dev);
printk(KERN_INFO "nbd: unregistered device at major %d\n", NBD_MAJOR);
}
module_init(nbd_init);
module_exit(nbd_cleanup);
MODULE_DESCRIPTION("Network Block Device");
MODULE_LICENSE("GPL");
module_param(nbds_max, int, 0444);
MODULE_PARM_DESC(nbds_max, "number of network block devices to initialize (default: 16)");
module_param(max_part, int, 0444);
MODULE_PARM_DESC(max_part, "number of partitions per device (default: 0)");
#ifndef NDEBUG
module_param(debugflags, int, 0644);
MODULE_PARM_DESC(debugflags, "flags for controlling debug output");
#endif
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