drivers/block/nbd.c

   1 /*
   2  * Network block device - make block devices work over TCP
   3  *
   4  * Note that you can not swap over this thing, yet. Seems to work but
   5  * deadlocks sometimes - you can not swap over TCP in general.
   6  *
   7  * Copyright 1997-2000, 2008 Pavel Machek <pavel@ucw.cz>
   8  * Parts copyright 2001 Steven Whitehouse <steve@chygwyn.com>
   9  *
  10  * This file is released under GPLv2 or later.
  11  *
  12  * (part of code stolen from loop.c)
  13  */
  14
  15 #include <linux/major.h>
  16
  17 #include <linux/blkdev.h>
  18 #include <linux/module.h>
  19 #include <linux/init.h>
  20 #include <linux/sched.h>
  21 #include <linux/fs.h>
  22 #include <linux/bio.h>
  23 #include <linux/stat.h>
  24 #include <linux/errno.h>
  25 #include <linux/file.h>
  26 #include <linux/ioctl.h>
  27 #include <linux/mutex.h>
  28 #include <linux/compiler.h>
  29 #include <linux/err.h>
  30 #include <linux/kernel.h>
  31 #include <linux/slab.h>
  32 #include <net/sock.h>
  33 #include <linux/net.h>
  34 #include <linux/kthread.h>
  35
  36 #include <asm/uaccess.h>
  37 #include <asm/types.h>
  38
  39 #include <linux/nbd.h>
  40
  41 #define NBD_MAGIC 0x68797548
  42
  43 #ifdef NDEBUG
  44 #define dprintk(flags, fmt...)
  45 #else /* NDEBUG */
  46 #define dprintk(flags, fmt...) do { \
  47         if (debugflags & (flags)) printk(KERN_DEBUG fmt); \
  48 } while (0)
  49 #define DBG_IOCTL       0x0004
  50 #define DBG_INIT        0x0010
  51 #define DBG_EXIT        0x0020
  52 #define DBG_BLKDEV      0x0100
  53 #define DBG_RX          0x0200
  54 #define DBG_TX          0x0400
  55 static unsigned int debugflags;
  56 #endif /* NDEBUG */
  57
  58 static unsigned int nbds_max = 16;
  59 static struct nbd_device *nbd_dev;
  60 static int max_part;
  61
  62 /*
  63  * Use just one lock (or at most 1 per NIC). Two arguments for this:
  64  * 1. Each NIC is essentially a synchronization point for all servers
  65  *    accessed through that NIC so there's no need to have more locks
  66  *    than NICs anyway.
  67  * 2. More locks lead to more "Dirty cache line bouncing" which will slow
  68  *    down each lock to the point where they're actually slower than just
  69  *    a single lock.
  70  * Thanks go to Jens Axboe and Al Viro for their LKML emails explaining this!
  71  */
  72 static DEFINE_SPINLOCK(nbd_lock);
  73
  74 #ifndef NDEBUG
  75 static const char *ioctl_cmd_to_ascii(int cmd)
  76 {
  77         switch (cmd) {
  78         case NBD_SET_SOCK: return "set-sock";
  79         case NBD_SET_BLKSIZE: return "set-blksize";
  80         case NBD_SET_SIZE: return "set-size";
  81         case NBD_DO_IT: return "do-it";
  82         case NBD_CLEAR_SOCK: return "clear-sock";
  83         case NBD_CLEAR_QUE: return "clear-que";
  84         case NBD_PRINT_DEBUG: return "print-debug";
  85         case NBD_SET_SIZE_BLOCKS: return "set-size-blocks";
  86         case NBD_DISCONNECT: return "disconnect";
  87         case BLKROSET: return "set-read-only";
  88         case BLKFLSBUF: return "flush-buffer-cache";
  89         }
  90         return "unknown";
  91 }
  92
  93 static const char *nbdcmd_to_ascii(int cmd)
  94 {
  95         switch (cmd) {
  96         case  NBD_CMD_READ: return "read";
  97         case NBD_CMD_WRITE: return "write";
  98         case  NBD_CMD_DISC: return "disconnect";
  99         }
 100         return "invalid";
 101 }
 102 #endif /* NDEBUG */
 103
 104 static void nbd_end_request(struct request *req)
 105 {
 106         int error = req->errors ? -EIO : 0;
 107         struct request_queue *q = req->q;
 108         unsigned long flags;
 109
 110         dprintk(DBG_BLKDEV, "%s: request %p: %s\n", req->rq_disk->disk_name,
 111                         req, error ? "failed" : "done");
 112
 113         spin_lock_irqsave(q->queue_lock, flags);
 114         __blk_end_request_all(req, error);
 115         spin_unlock_irqrestore(q->queue_lock, flags);
 116 }
 117
 118 static void sock_shutdown(struct nbd_device *nbd, int lock)
 119 {
 120         /* Forcibly shutdown the socket causing all listeners
 121          * to error
 122          *
 123          * FIXME: This code is duplicated from sys_shutdown, but
 124          * there should be a more generic interface rather than
 125          * calling socket ops directly here */
 126         if (lock)
 127                 mutex_lock(&nbd->tx_lock);
 128         if (nbd->sock) {
 129                 dev_warn(disk_to_dev(nbd->disk), "shutting down socket\n");
 130                 kernel_sock_shutdown(nbd->sock, SHUT_RDWR);
 131                 nbd->sock = NULL;
 132         }
 133         if (lock)
 134                 mutex_unlock(&nbd->tx_lock);
 135 }
 136
 137 static void nbd_xmit_timeout(unsigned long arg)
 138 {
 139         struct task_struct *task = (struct task_struct *)arg;
 140
 141         printk(KERN_WARNING "nbd: killing hung xmit (%s, pid: %d)\n",
 142                 task->comm, task->pid);
 143         force_sig(SIGKILL, task);
 144 }
 145
 146 /*
 147  *  Send or receive packet.
 148  */
 149 static int sock_xmit(struct nbd_device *nbd, int send, void *buf, int size,
 150                 int msg_flags)
 151 {
 152         struct socket *sock = nbd->sock;
 153         int result;
 154         struct msghdr msg;
 155         struct kvec iov;
 156         sigset_t blocked, oldset;
 157         unsigned long pflags = current->flags;
 158
 159         if (unlikely(!sock)) {
 160                 dev_err(disk_to_dev(nbd->disk),
 161                         "Attempted %s on closed socket in sock_xmit\n",
 162                         (send ? "send" : "recv"));
 163                 return -EINVAL;
 164         }
 165
 166         /* Allow interception of SIGKILL only
 167          * Don't allow other signals to interrupt the transmission */
 168         siginitsetinv(&blocked, sigmask(SIGKILL));
 169         sigprocmask(SIG_SETMASK, &blocked, &oldset);
 170
 171         current->flags |= PF_MEMALLOC;
 172         do {
 173                 sock->sk->sk_allocation = GFP_NOIO | __GFP_MEMALLOC;
 174                 iov.iov_base = buf;
 175                 iov.iov_len = size;
 176                 msg.msg_name = NULL;
 177                 msg.msg_namelen = 0;
 178                 msg.msg_control = NULL;
 179                 msg.msg_controllen = 0;
 180                 msg.msg_flags = msg_flags | MSG_NOSIGNAL;
 181
 182                 if (send) {
 183                         struct timer_list ti;
 184
 185                         if (nbd->xmit_timeout) {
 186                                 init_timer(&ti);
 187                                 ti.function = nbd_xmit_timeout;
 188                                 ti.data = (unsigned long)current;
 189                                 ti.expires = jiffies + nbd->xmit_timeout;
 190                                 add_timer(&ti);
 191                         }
 192                         result = kernel_sendmsg(sock, &msg, &iov, 1, size);
 193                         if (nbd->xmit_timeout)
 194                                 del_timer_sync(&ti);
 195                 } else
 196                         result = kernel_recvmsg(sock, &msg, &iov, 1, size,
 197                                                 msg.msg_flags);
 198
 199                 if (signal_pending(current)) {
 200                         siginfo_t info;
 201                         printk(KERN_WARNING "nbd (pid %d: %s) got signal %d\n",
 202                                 task_pid_nr(current), current->comm,
 203                                 dequeue_signal_lock(current, &current->blocked, &info));
 204                         result = -EINTR;
 205                         sock_shutdown(nbd, !send);
 206                         break;
 207                 }
 208
 209                 if (result <= 0) {
 210                         if (result == 0)
 211                                 result = -EPIPE; /* short read */
 212                         break;
 213                 }
 214                 size -= result;
 215                 buf += result;
 216         } while (size > 0);
 217
 218         sigprocmask(SIG_SETMASK, &oldset, NULL);
 219         tsk_restore_flags(current, pflags, PF_MEMALLOC);
 220
 221         return result;
 222 }
 223
 224 static inline int sock_send_bvec(struct nbd_device *nbd, struct bio_vec *bvec,
 225                 int flags)
 226 {
 227         int result;
 228         void *kaddr = kmap(bvec->bv_page);
 229         result = sock_xmit(nbd, 1, kaddr + bvec->bv_offset,
 230                            bvec->bv_len, flags);
 231         kunmap(bvec->bv_page);
 232         return result;
 233 }
 234
 235 /* always call with the tx_lock held */
 236 static int nbd_send_req(struct nbd_device *nbd, struct request *req)
 237 {
 238         int result, flags;
 239         struct nbd_request request;
 240         unsigned long size = blk_rq_bytes(req);
 241
 242         request.magic = htonl(NBD_REQUEST_MAGIC);
 243         request.type = htonl(nbd_cmd(req));
 244         request.from = cpu_to_be64((u64)blk_rq_pos(req) << 9);
 245         request.len = htonl(size);
 246         memcpy(request.handle, &req, sizeof(req));
 247
 248         dprintk(DBG_TX, "%s: request %p: sending control (%s@%llu,%uB)\n",
 249                         nbd->disk->disk_name, req,
 250                         nbdcmd_to_ascii(nbd_cmd(req)),
 251                         (unsigned long long)blk_rq_pos(req) << 9,
 252                         blk_rq_bytes(req));
 253         result = sock_xmit(nbd, 1, &request, sizeof(request),
 254                         (nbd_cmd(req) == NBD_CMD_WRITE) ? MSG_MORE : 0);
 255         if (result <= 0) {
 256                 dev_err(disk_to_dev(nbd->disk),
 257                         "Send control failed (result %d)\n", result);
 258                 goto error_out;
 259         }
 260
 261         if (nbd_cmd(req) == NBD_CMD_WRITE) {
 262                 struct req_iterator iter;
 263                 struct bio_vec *bvec;
 264                 /*
 265                  * we are really probing at internals to determine
 266                  * whether to set MSG_MORE or not...
 267                  */
 268                 rq_for_each_segment(bvec, req, iter) {
 269                         flags = 0;
 270                         if (!rq_iter_last(req, iter))
 271                                 flags = MSG_MORE;
 272                         dprintk(DBG_TX, "%s: request %p: sending %d bytes data\n",
 273                                         nbd->disk->disk_name, req, bvec->bv_len);
 274                         result = sock_send_bvec(nbd, bvec, flags);
 275                         if (result <= 0) {
 276                                 dev_err(disk_to_dev(nbd->disk),
 277                                         "Send data failed (result %d)\n",
 278                                         result);
 279                                 goto error_out;
 280                         }
 281                 }
 282         }
 283         return 0;
 284
 285 error_out:
 286         return -EIO;
 287 }
 288
 289 static struct request *nbd_find_request(struct nbd_device *nbd,
 290                                         struct request *xreq)
 291 {
 292         struct request *req, *tmp;
 293         int err;
 294
 295         err = wait_event_interruptible(nbd->active_wq, nbd->active_req != xreq);
 296         if (unlikely(err))
 297                 goto out;
 298
 299         spin_lock(&nbd->queue_lock);
 300         list_for_each_entry_safe(req, tmp, &nbd->queue_head, queuelist) {
 301                 if (req != xreq)
 302                         continue;
 303                 list_del_init(&req->queuelist);
 304                 spin_unlock(&nbd->queue_lock);
 305                 return req;
 306         }
 307         spin_unlock(&nbd->queue_lock);
 308
 309         err = -ENOENT;
 310
 311 out:
 312         return ERR_PTR(err);
 313 }
 314
 315 static inline int sock_recv_bvec(struct nbd_device *nbd, struct bio_vec *bvec)
 316 {
 317         int result;
 318         void *kaddr = kmap(bvec->bv_page);
 319         result = sock_xmit(nbd, 0, kaddr + bvec->bv_offset, bvec->bv_len,
 320                         MSG_WAITALL);
 321         kunmap(bvec->bv_page);
 322         return result;
 323 }
 324
 325 /* NULL returned = something went wrong, inform userspace */
 326 static struct request *nbd_read_stat(struct nbd_device *nbd)
 327 {
 328         int result;
 329         struct nbd_reply reply;
 330         struct request *req;
 331
 332         reply.magic = 0;
 333         result = sock_xmit(nbd, 0, &reply, sizeof(reply), MSG_WAITALL);
 334         if (result <= 0) {
 335                 dev_err(disk_to_dev(nbd->disk),
 336                         "Receive control failed (result %d)\n", result);
 337                 goto harderror;
 338         }
 339
 340         if (ntohl(reply.magic) != NBD_REPLY_MAGIC) {
 341                 dev_err(disk_to_dev(nbd->disk), "Wrong magic (0x%lx)\n",
 342                                 (unsigned long)ntohl(reply.magic));
 343                 result = -EPROTO;
 344                 goto harderror;
 345         }
 346
 347         req = nbd_find_request(nbd, *(struct request **)reply.handle);
 348         if (IS_ERR(req)) {
 349                 result = PTR_ERR(req);
 350                 if (result != -ENOENT)
 351                         goto harderror;
 352
 353                 dev_err(disk_to_dev(nbd->disk), "Unexpected reply (%p)\n",
 354                         reply.handle);
 355                 result = -EBADR;
 356                 goto harderror;
 357         }
 358
 359         if (ntohl(reply.error)) {
 360                 dev_err(disk_to_dev(nbd->disk), "Other side returned error (%d)\n",
 361                         ntohl(reply.error));
 362                 req->errors++;
 363                 return req;
 364         }
 365
 366         dprintk(DBG_RX, "%s: request %p: got reply\n",
 367                         nbd->disk->disk_name, req);
 368         if (nbd_cmd(req) == NBD_CMD_READ) {
 369                 struct req_iterator iter;
 370                 struct bio_vec *bvec;
 371
 372                 rq_for_each_segment(bvec, req, iter) {
 373                         result = sock_recv_bvec(nbd, bvec);
 374                         if (result <= 0) {
 375                                 dev_err(disk_to_dev(nbd->disk), "Receive data failed (result %d)\n",
 376                                         result);
 377                                 req->errors++;
 378                                 return req;
 379                         }
 380                         dprintk(DBG_RX, "%s: request %p: got %d bytes data\n",
 381                                 nbd->disk->disk_name, req, bvec->bv_len);
 382                 }
 383         }
 384         return req;
 385 harderror:
 386         nbd->harderror = result;
 387         return NULL;
 388 }
 389
 390 static ssize_t pid_show(struct device *dev,
 391                         struct device_attribute *attr, char *buf)
 392 {
 393         struct gendisk *disk = dev_to_disk(dev);
 394
 395         return sprintf(buf, "%ld\n",
 396                 (long) ((struct nbd_device *)disk->private_data)->pid);
 397 }
 398
 399 static struct device_attribute pid_attr = {
 400         .attr = { .name = "pid", .mode = S_IRUGO},
 401         .show = pid_show,
 402 };
 403
 404 static int nbd_do_it(struct nbd_device *nbd)
 405 {
 406         struct request *req;
 407         int ret;
 408
 409         BUG_ON(nbd->magic != NBD_MAGIC);
 410
 411         sk_set_memalloc(nbd->sock->sk);
 412         nbd->pid = task_pid_nr(current);
 413         ret = device_create_file(disk_to_dev(nbd->disk), &pid_attr);
 414         if (ret) {
 415                 dev_err(disk_to_dev(nbd->disk), "device_create_file failed!\n");
 416                 nbd->pid = 0;
 417                 return ret;
 418         }
 419
 420         while ((req = nbd_read_stat(nbd)) != NULL)
 421                 nbd_end_request(req);
 422
 423         device_remove_file(disk_to_dev(nbd->disk), &pid_attr);
 424         nbd->pid = 0;
 425         return 0;
 426 }
 427
 428 static void nbd_clear_que(struct nbd_device *nbd)
 429 {
 430         struct request *req;
 431
 432         BUG_ON(nbd->magic != NBD_MAGIC);
 433
 434         /*
 435          * Because we have set nbd->sock to NULL under the tx_lock, all
 436          * modifications to the list must have completed by now.  For
 437          * the same reason, the active_req must be NULL.
 438          *
 439          * As a consequence, we don't need to take the spin lock while
 440          * purging the list here.
 441          */
 442         BUG_ON(nbd->sock);
 443         BUG_ON(nbd->active_req);
 444
 445         while (!list_empty(&nbd->queue_head)) {
 446                 req = list_entry(nbd->queue_head.next, struct request,
 447                                  queuelist);
 448                 list_del_init(&req->queuelist);
 449                 req->errors++;
 450                 nbd_end_request(req);
 451         }
 452 }
 453
 454
 455 static void nbd_handle_req(struct nbd_device *nbd, struct request *req)
 456 {
 457         if (req->cmd_type != REQ_TYPE_FS)
 458                 goto error_out;
 459
 460         nbd_cmd(req) = NBD_CMD_READ;
 461         if (rq_data_dir(req) == WRITE) {
 462                 nbd_cmd(req) = NBD_CMD_WRITE;
 463                 if (nbd->flags & NBD_READ_ONLY) {
 464                         dev_err(disk_to_dev(nbd->disk),
 465                                 "Write on read-only\n");
 466                         goto error_out;
 467                 }
 468         }
 469
 470         req->errors = 0;
 471
 472         mutex_lock(&nbd->tx_lock);
 473         if (unlikely(!nbd->sock)) {
 474                 mutex_unlock(&nbd->tx_lock);
 475                 dev_err(disk_to_dev(nbd->disk),
 476                         "Attempted send on closed socket\n");
 477                 goto error_out;
 478         }
 479
 480         nbd->active_req = req;
 481
 482         if (nbd_send_req(nbd, req) != 0) {
 483                 dev_err(disk_to_dev(nbd->disk), "Request send failed\n");
 484                 req->errors++;
 485                 nbd_end_request(req);
 486         } else {
 487                 spin_lock(&nbd->queue_lock);
 488                 list_add_tail(&req->queuelist, &nbd->queue_head);
 489                 spin_unlock(&nbd->queue_lock);
 490         }
 491
 492         nbd->active_req = NULL;
 493         mutex_unlock(&nbd->tx_lock);
 494         wake_up_all(&nbd->active_wq);
 495
 496         return;
 497
 498 error_out:
 499         req->errors++;
 500         nbd_end_request(req);
 501 }
 502
 503 static int nbd_thread(void *data)
 504 {
 505         struct nbd_device *nbd = data;
 506         struct request *req;
 507
 508         set_user_nice(current, -20);
 509         while (!kthread_should_stop() || !list_empty(&nbd->waiting_queue)) {
 510                 /* wait for something to do */
 511                 wait_event_interruptible(nbd->waiting_wq,
 512                                          kthread_should_stop() ||
 513                                          !list_empty(&nbd->waiting_queue));
 514
 515                 /* extract request */
 516                 if (list_empty(&nbd->waiting_queue))
 517                         continue;
 518
 519                 spin_lock_irq(&nbd->queue_lock);
 520                 req = list_entry(nbd->waiting_queue.next, struct request,
 521                                  queuelist);
 522                 list_del_init(&req->queuelist);
 523                 spin_unlock_irq(&nbd->queue_lock);
 524
 525                 /* handle request */
 526                 nbd_handle_req(nbd, req);
 527         }
 528         return 0;
 529 }
 530
 531 /*
 532  * We always wait for result of write, for now. It would be nice to make it optional
 533  * in future
 534  * if ((rq_data_dir(req) == WRITE) && (nbd->flags & NBD_WRITE_NOCHK))
 535  *   { printk( "Warning: Ignoring result!\n"); nbd_end_request( req ); }
 536  */
 537
 538 static void do_nbd_request(struct request_queue *q)
 539 {
 540         struct request *req;
 541
 542         while ((req = blk_fetch_request(q)) != NULL) {
 543                 struct nbd_device *nbd;
 544
 545                 spin_unlock_irq(q->queue_lock);
 546
 547                 dprintk(DBG_BLKDEV, "%s: request %p: dequeued (flags=%x)\n",
 548                                 req->rq_disk->disk_name, req, req->cmd_type);
 549
 550                 nbd = req->rq_disk->private_data;
 551
 552                 BUG_ON(nbd->magic != NBD_MAGIC);
 553
 554                 if (unlikely(!nbd->sock)) {
 555                         dev_err(disk_to_dev(nbd->disk),
 556                                 "Attempted send on closed socket\n");
 557                         req->errors++;
 558                         nbd_end_request(req);
 559                         spin_lock_irq(q->queue_lock);
 560                         continue;
 561                 }
 562
 563                 spin_lock_irq(&nbd->queue_lock);
 564                 list_add_tail(&req->queuelist, &nbd->waiting_queue);
 565                 spin_unlock_irq(&nbd->queue_lock);
 566
 567                 wake_up(&nbd->waiting_wq);
 568
 569                 spin_lock_irq(q->queue_lock);
 570         }
 571 }
 572
 573 /* Must be called with tx_lock held */
 574
 575 static int __nbd_ioctl(struct block_device *bdev, struct nbd_device *nbd,
 576                        unsigned int cmd, unsigned long arg)
 577 {
 578         switch (cmd) {
 579         case NBD_DISCONNECT: {
 580                 struct request sreq;
 581
 582                 dev_info(disk_to_dev(nbd->disk), "NBD_DISCONNECT\n");
 583
 584                 blk_rq_init(NULL, &sreq);
 585                 sreq.cmd_type = REQ_TYPE_SPECIAL;
 586                 nbd_cmd(&sreq) = NBD_CMD_DISC;
 587                 if (!nbd->sock)
 588                         return -EINVAL;
 589                 nbd_send_req(nbd, &sreq);
 590                 return 0;
 591         }
 592
 593         case NBD_CLEAR_SOCK: {
 594                 struct file *file;
 595
 596                 nbd->sock = NULL;
 597                 file = nbd->file;
 598                 nbd->file = NULL;
 599                 nbd_clear_que(nbd);
 600                 BUG_ON(!list_empty(&nbd->queue_head));
 601                 if (file)
 602                         fput(file);
 603                 return 0;
 604         }
 605
 606         case NBD_SET_SOCK: {
 607                 struct file *file;
 608                 if (nbd->file)
 609                         return -EBUSY;
 610                 file = fget(arg);
 611                 if (file) {
 612                         struct inode *inode = file->f_path.dentry->d_inode;
 613                         if (S_ISSOCK(inode->i_mode)) {
 614                                 nbd->file = file;
 615                                 nbd->sock = SOCKET_I(inode);
 616                                 if (max_part > 0)
 617                                         bdev->bd_invalidated = 1;
 618                                 return 0;
 619                         } else {
 620                                 fput(file);
 621                         }
 622                 }
 623                 return -EINVAL;
 624         }
 625
 626         case NBD_SET_BLKSIZE:
 627                 nbd->blksize = arg;
 628                 nbd->bytesize &= ~(nbd->blksize-1);
 629                 bdev->bd_inode->i_size = nbd->bytesize;
 630                 set_blocksize(bdev, nbd->blksize);
 631                 set_capacity(nbd->disk, nbd->bytesize >> 9);
 632                 return 0;
 633
 634         case NBD_SET_SIZE:
 635                 nbd->bytesize = arg & ~(nbd->blksize-1);
 636                 bdev->bd_inode->i_size = nbd->bytesize;
 637                 set_blocksize(bdev, nbd->blksize);
 638                 set_capacity(nbd->disk, nbd->bytesize >> 9);
 639                 return 0;
 640
 641         case NBD_SET_TIMEOUT:
 642                 nbd->xmit_timeout = arg * HZ;
 643                 return 0;
 644
 645         case NBD_SET_SIZE_BLOCKS:
 646                 nbd->bytesize = ((u64) arg) * nbd->blksize;
 647                 bdev->bd_inode->i_size = nbd->bytesize;
 648                 set_blocksize(bdev, nbd->blksize);
 649                 set_capacity(nbd->disk, nbd->bytesize >> 9);
 650                 return 0;
 651
 652         case NBD_DO_IT: {
 653                 struct task_struct *thread;
 654                 struct file *file;
 655                 int error;
 656
 657                 if (nbd->pid)
 658                         return -EBUSY;
 659                 if (!nbd->file)
 660                         return -EINVAL;
 661
 662                 mutex_unlock(&nbd->tx_lock);
 663
 664                 thread = kthread_create(nbd_thread, nbd, nbd->disk->disk_name);
 665                 if (IS_ERR(thread)) {
 666                         mutex_lock(&nbd->tx_lock);
 667                         return PTR_ERR(thread);
 668                 }
 669                 wake_up_process(thread);
 670                 error = nbd_do_it(nbd);
 671                 kthread_stop(thread);
 672
 673                 mutex_lock(&nbd->tx_lock);
 674                 if (error)
 675                         return error;
 676                 sock_shutdown(nbd, 0);
 677                 file = nbd->file;
 678                 nbd->file = NULL;
 679                 nbd_clear_que(nbd);
 680                 dev_warn(disk_to_dev(nbd->disk), "queue cleared\n");
 681                 if (file)
 682                         fput(file);
 683                 nbd->bytesize = 0;
 684                 bdev->bd_inode->i_size = 0;
 685                 set_capacity(nbd->disk, 0);
 686                 if (max_part > 0)
 687                         ioctl_by_bdev(bdev, BLKRRPART, 0);
 688                 return nbd->harderror;
 689         }
 690
 691         case NBD_CLEAR_QUE:
 692                 /*
 693                  * This is for compatibility only.  The queue is always cleared
 694                  * by NBD_DO_IT or NBD_CLEAR_SOCK.
 695                  */
 696                 BUG_ON(!nbd->sock && !list_empty(&nbd->queue_head));
 697                 return 0;
 698
 699         case NBD_PRINT_DEBUG:
 700                 dev_info(disk_to_dev(nbd->disk),
 701                         "next = %p, prev = %p, head = %p\n",
 702                         nbd->queue_head.next, nbd->queue_head.prev,
 703                         &nbd->queue_head);
 704                 return 0;
 705         }
 706         return -ENOTTY;
 707 }
 708
 709 static int nbd_ioctl(struct block_device *bdev, fmode_t mode,
 710                      unsigned int cmd, unsigned long arg)
 711 {
 712         struct nbd_device *nbd = bdev->bd_disk->private_data;
 713         int error;
 714
 715         if (!capable(CAP_SYS_ADMIN))
 716                 return -EPERM;
 717
 718         BUG_ON(nbd->magic != NBD_MAGIC);
 719
 720         /* Anyone capable of this syscall can do *real bad* things */
 721         dprintk(DBG_IOCTL, "%s: nbd_ioctl cmd=%s(0x%x) arg=%lu\n",
 722                 nbd->disk->disk_name, ioctl_cmd_to_ascii(cmd), cmd, arg);
 723
 724         mutex_lock(&nbd->tx_lock);
 725         error = __nbd_ioctl(bdev, nbd, cmd, arg);
 726         mutex_unlock(&nbd->tx_lock);
 727
 728         return error;
 729 }
 730
 731 static const struct block_device_operations nbd_fops =
 732 {
 733         .owner =        THIS_MODULE,
 734         .ioctl =        nbd_ioctl,
 735 };
 736
 737 /*
 738  * And here should be modules and kernel interface
 739  *  (Just smiley confuses emacs :-)
 740  */
 741
 742 static int __init nbd_init(void)
 743 {
 744         int err = -ENOMEM;
 745         int i;
 746         int part_shift;
 747
 748         BUILD_BUG_ON(sizeof(struct nbd_request) != 28);
 749
 750         if (max_part < 0) {
 751                 printk(KERN_ERR "nbd: max_part must be >= 0\n");
 752                 return -EINVAL;
 753         }
 754
 755         nbd_dev = kcalloc(nbds_max, sizeof(*nbd_dev), GFP_KERNEL);
 756         if (!nbd_dev)
 757                 return -ENOMEM;
 758
 759         part_shift = 0;
 760         if (max_part > 0) {
 761                 part_shift = fls(max_part);
 762
 763                 /*
 764                  * Adjust max_part according to part_shift as it is exported
 765                  * to user space so that user can know the max number of
 766                  * partition kernel should be able to manage.
 767                  *
 768                  * Note that -1 is required because partition 0 is reserved
 769                  * for the whole disk.
 770                  */
 771                 max_part = (1UL << part_shift) - 1;
 772         }
 773
 774         if ((1UL << part_shift) > DISK_MAX_PARTS)
 775                 return -EINVAL;
 776
 777         if (nbds_max > 1UL << (MINORBITS - part_shift))
 778                 return -EINVAL;
 779
 780         for (i = 0; i < nbds_max; i++) {
 781                 struct gendisk *disk = alloc_disk(1 << part_shift);
 782                 if (!disk)
 783                         goto out;
 784                 nbd_dev[i].disk = disk;
 785                 /*
 786                  * The new linux 2.5 block layer implementation requires
 787                  * every gendisk to have its very own request_queue struct.
 788                  * These structs are big so we dynamically allocate them.
 789                  */
 790                 disk->queue = blk_init_queue(do_nbd_request, &nbd_lock);
 791                 if (!disk->queue) {
 792                         put_disk(disk);
 793                         goto out;
 794                 }
 795                 /*
 796                  * Tell the block layer that we are not a rotational device
 797                  */
 798                 queue_flag_set_unlocked(QUEUE_FLAG_NONROT, disk->queue);
 799         }
 800
 801         if (register_blkdev(NBD_MAJOR, "nbd")) {
 802                 err = -EIO;
 803                 goto out;
 804         }
 805
 806         printk(KERN_INFO "nbd: registered device at major %d\n", NBD_MAJOR);
 807         dprintk(DBG_INIT, "nbd: debugflags=0x%x\n", debugflags);
 808
 809         for (i = 0; i < nbds_max; i++) {
 810                 struct gendisk *disk = nbd_dev[i].disk;
 811                 nbd_dev[i].file = NULL;
 812                 nbd_dev[i].magic = NBD_MAGIC;
 813                 nbd_dev[i].flags = 0;
 814                 INIT_LIST_HEAD(&nbd_dev[i].waiting_queue);
 815                 spin_lock_init(&nbd_dev[i].queue_lock);
 816                 INIT_LIST_HEAD(&nbd_dev[i].queue_head);
 817                 mutex_init(&nbd_dev[i].tx_lock);
 818                 init_waitqueue_head(&nbd_dev[i].active_wq);
 819                 init_waitqueue_head(&nbd_dev[i].waiting_wq);
 820                 nbd_dev[i].blksize = 1024;
 821                 nbd_dev[i].bytesize = 0;
 822                 disk->major = NBD_MAJOR;
 823                 disk->first_minor = i << part_shift;
 824                 disk->fops = &nbd_fops;
 825                 disk->private_data = &nbd_dev[i];
 826                 sprintf(disk->disk_name, "nbd%d", i);
 827                 set_capacity(disk, 0);
 828                 add_disk(disk);
 829         }
 830
 831         return 0;
 832 out:
 833         while (i--) {
 834                 blk_cleanup_queue(nbd_dev[i].disk->queue);
 835                 put_disk(nbd_dev[i].disk);
 836         }
 837         kfree(nbd_dev);
 838         return err;
 839 }
 840
 841 static void __exit nbd_cleanup(void)
 842 {
 843         int i;
 844         for (i = 0; i < nbds_max; i++) {
 845                 struct gendisk *disk = nbd_dev[i].disk;
 846                 nbd_dev[i].magic = 0;
 847                 if (disk) {
 848                         del_gendisk(disk);
 849                         blk_cleanup_queue(disk->queue);
 850                         put_disk(disk);
 851                 }
 852         }
 853         unregister_blkdev(NBD_MAJOR, "nbd");
 854         kfree(nbd_dev);
 855         printk(KERN_INFO "nbd: unregistered device at major %d\n", NBD_MAJOR);
 856 }
 857
 858 module_init(nbd_init);
 859 module_exit(nbd_cleanup);
 860
 861 MODULE_DESCRIPTION("Network Block Device");
 862 MODULE_LICENSE("GPL");
 863
 864 module_param(nbds_max, int, 0444);
 865 MODULE_PARM_DESC(nbds_max, "number of network block devices to initialize (default: 16)");
 866 module_param(max_part, int, 0444);
 867 MODULE_PARM_DESC(max_part, "number of partitions per device (default: 0)");
 868 #ifndef NDEBUG
 869 module_param(debugflags, int, 0644);
 870 MODULE_PARM_DESC(debugflags, "flags for controlling debug output");
 871 #endif