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 #include <linux/types.h>
  36
  37 #include <asm/uaccess.h>
  38 #include <asm/types.h>
  39
  40 #include <linux/nbd.h>
  41
  42 struct nbd_device {
  43         int flags;
  44         int harderror;          /* Code of hard error                   */
  45         struct socket * sock;   /* If == NULL, device is not ready, yet */
  46         int magic;
  47
  48         spinlock_t queue_lock;
  49         struct list_head queue_head;    /* Requests waiting result */
  50         struct request *active_req;
  51         wait_queue_head_t active_wq;
  52         struct list_head waiting_queue; /* Requests to be sent */
  53         wait_queue_head_t waiting_wq;
  54
  55         struct mutex tx_lock;
  56         struct gendisk *disk;
  57         int blksize;
  58         loff_t bytesize;
  59         pid_t pid; /* pid of nbd-client, if attached */
  60         int xmit_timeout;
  61         int disconnect; /* a disconnect has been requested by user */
  62 };
  63
  64 #define NBD_MAGIC 0x68797548
  65
  66 static unsigned int nbds_max = 16;
  67 static struct nbd_device *nbd_dev;
  68 static int max_part;
  69
  70 /*
  71  * Use just one lock (or at most 1 per NIC). Two arguments for this:
  72  * 1. Each NIC is essentially a synchronization point for all servers
  73  *    accessed through that NIC so there's no need to have more locks
  74  *    than NICs anyway.
  75  * 2. More locks lead to more "Dirty cache line bouncing" which will slow
  76  *    down each lock to the point where they're actually slower than just
  77  *    a single lock.
  78  * Thanks go to Jens Axboe and Al Viro for their LKML emails explaining this!
  79  */
  80 static DEFINE_SPINLOCK(nbd_lock);
  81
  82 static inline struct device *nbd_to_dev(struct nbd_device *nbd)
  83 {
  84         return disk_to_dev(nbd->disk);
  85 }
  86
  87 static const char *nbdcmd_to_ascii(int cmd)
  88 {
  89         switch (cmd) {
  90         case  NBD_CMD_READ: return "read";
  91         case NBD_CMD_WRITE: return "write";
  92         case  NBD_CMD_DISC: return "disconnect";
  93         case NBD_CMD_FLUSH: return "flush";
  94         case  NBD_CMD_TRIM: return "trim/discard";
  95         }
  96         return "invalid";
  97 }
  98
  99 static void nbd_end_request(struct nbd_device *nbd, struct request *req)
 100 {
 101         int error = req->errors ? -EIO : 0;
 102         struct request_queue *q = req->q;
 103         unsigned long flags;
 104
 105         dev_dbg(nbd_to_dev(nbd), "request %p: %s\n", req,
 106                 error ? "failed" : "done");
 107
 108         spin_lock_irqsave(q->queue_lock, flags);
 109         __blk_end_request_all(req, error);
 110         spin_unlock_irqrestore(q->queue_lock, flags);
 111 }
 112
 113 /*
 114  * Forcibly shutdown the socket causing all listeners to error
 115  */
 116 static void sock_shutdown(struct nbd_device *nbd, int lock)
 117 {
 118         if (lock)
 119                 mutex_lock(&nbd->tx_lock);
 120         if (nbd->sock) {
 121                 dev_warn(disk_to_dev(nbd->disk), "shutting down socket\n");
 122                 kernel_sock_shutdown(nbd->sock, SHUT_RDWR);
 123                 nbd->sock = NULL;
 124         }
 125         if (lock)
 126                 mutex_unlock(&nbd->tx_lock);
 127 }
 128
 129 static void nbd_xmit_timeout(unsigned long arg)
 130 {
 131         struct task_struct *task = (struct task_struct *)arg;
 132
 133         printk(KERN_WARNING "nbd: killing hung xmit (%s, pid: %d)\n",
 134                 task->comm, task->pid);
 135         force_sig(SIGKILL, task);
 136 }
 137
 138 /*
 139  *  Send or receive packet.
 140  */
 141 static int sock_xmit(struct nbd_device *nbd, int send, void *buf, int size,
 142                 int msg_flags)
 143 {
 144         struct socket *sock = nbd->sock;
 145         int result;
 146         struct msghdr msg;
 147         struct kvec iov;
 148         sigset_t blocked, oldset;
 149         unsigned long pflags = current->flags;
 150
 151         if (unlikely(!sock)) {
 152                 dev_err(disk_to_dev(nbd->disk),
 153                         "Attempted %s on closed socket in sock_xmit\n",
 154                         (send ? "send" : "recv"));
 155                 return -EINVAL;
 156         }
 157
 158         /* Allow interception of SIGKILL only
 159          * Don't allow other signals to interrupt the transmission */
 160         siginitsetinv(&blocked, sigmask(SIGKILL));
 161         sigprocmask(SIG_SETMASK, &blocked, &oldset);
 162
 163         current->flags |= PF_MEMALLOC;
 164         do {
 165                 sock->sk->sk_allocation = GFP_NOIO | __GFP_MEMALLOC;
 166                 iov.iov_base = buf;
 167                 iov.iov_len = size;
 168                 msg.msg_name = NULL;
 169                 msg.msg_namelen = 0;
 170                 msg.msg_control = NULL;
 171                 msg.msg_controllen = 0;
 172                 msg.msg_flags = msg_flags | MSG_NOSIGNAL;
 173
 174                 if (send) {
 175                         struct timer_list ti;
 176
 177                         if (nbd->xmit_timeout) {
 178                                 init_timer(&ti);
 179                                 ti.function = nbd_xmit_timeout;
 180                                 ti.data = (unsigned long)current;
 181                                 ti.expires = jiffies + nbd->xmit_timeout;
 182                                 add_timer(&ti);
 183                         }
 184                         result = kernel_sendmsg(sock, &msg, &iov, 1, size);
 185                         if (nbd->xmit_timeout)
 186                                 del_timer_sync(&ti);
 187                 } else
 188                         result = kernel_recvmsg(sock, &msg, &iov, 1, size,
 189                                                 msg.msg_flags);
 190
 191                 if (signal_pending(current)) {
 192                         siginfo_t info;
 193                         printk(KERN_WARNING "nbd (pid %d: %s) got signal %d\n",
 194                                 task_pid_nr(current), current->comm,
 195                                 dequeue_signal_lock(current, &current->blocked, &info));
 196                         result = -EINTR;
 197                         sock_shutdown(nbd, !send);
 198                         break;
 199                 }
 200
 201                 if (result <= 0) {
 202                         if (result == 0)
 203                                 result = -EPIPE; /* short read */
 204                         break;
 205                 }
 206                 size -= result;
 207                 buf += result;
 208         } while (size > 0);
 209
 210         sigprocmask(SIG_SETMASK, &oldset, NULL);
 211         tsk_restore_flags(current, pflags, PF_MEMALLOC);
 212
 213         return result;
 214 }
 215
 216 static inline int sock_send_bvec(struct nbd_device *nbd, struct bio_vec *bvec,
 217                 int flags)
 218 {
 219         int result;
 220         void *kaddr = kmap(bvec->bv_page);
 221         result = sock_xmit(nbd, 1, kaddr + bvec->bv_offset,
 222                            bvec->bv_len, flags);
 223         kunmap(bvec->bv_page);
 224         return result;
 225 }
 226
 227 /* always call with the tx_lock held */
 228 static int nbd_send_req(struct nbd_device *nbd, struct request *req)
 229 {
 230         int result, flags;
 231         struct nbd_request request;
 232         unsigned long size = blk_rq_bytes(req);
 233         u32 type;
 234
 235         if (req->cmd_type == REQ_TYPE_DRV_PRIV)
 236                 type = NBD_CMD_DISC;
 237         else if (req->cmd_flags & REQ_DISCARD)
 238                 type = NBD_CMD_TRIM;
 239         else if (req->cmd_flags & REQ_FLUSH)
 240                 type = NBD_CMD_FLUSH;
 241         else if (rq_data_dir(req) == WRITE)
 242                 type = NBD_CMD_WRITE;
 243         else
 244                 type = NBD_CMD_READ;
 245
 246         memset(&request, 0, sizeof(request));
 247         request.magic = htonl(NBD_REQUEST_MAGIC);
 248         request.type = htonl(type);
 249         if (type != NBD_CMD_FLUSH && type != NBD_CMD_DISC) {
 250                 request.from = cpu_to_be64((u64)blk_rq_pos(req) << 9);
 251                 request.len = htonl(size);
 252         }
 253         memcpy(request.handle, &req, sizeof(req));
 254
 255         dev_dbg(nbd_to_dev(nbd), "request %p: sending control (%s@%llu,%uB)\n",
 256                 req, nbdcmd_to_ascii(type),
 257                 (unsigned long long)blk_rq_pos(req) << 9, blk_rq_bytes(req));
 258         result = sock_xmit(nbd, 1, &request, sizeof(request),
 259                         (type == NBD_CMD_WRITE) ? MSG_MORE : 0);
 260         if (result <= 0) {
 261                 dev_err(disk_to_dev(nbd->disk),
 262                         "Send control failed (result %d)\n", result);
 263                 return -EIO;
 264         }
 265
 266         if (type == NBD_CMD_WRITE) {
 267                 struct req_iterator iter;
 268                 struct bio_vec bvec;
 269                 /*
 270                  * we are really probing at internals to determine
 271                  * whether to set MSG_MORE or not...
 272                  */
 273                 rq_for_each_segment(bvec, req, iter) {
 274                         flags = 0;
 275                         if (!rq_iter_last(bvec, iter))
 276                                 flags = MSG_MORE;
 277                         dev_dbg(nbd_to_dev(nbd), "request %p: sending %d bytes data\n",
 278                                 req, bvec.bv_len);
 279                         result = sock_send_bvec(nbd, &bvec, flags);
 280                         if (result <= 0) {
 281                                 dev_err(disk_to_dev(nbd->disk),
 282                                         "Send data failed (result %d)\n",
 283                                         result);
 284                                 return -EIO;
 285                         }
 286                 }
 287         }
 288         return 0;
 289 }
 290
 291 static struct request *nbd_find_request(struct nbd_device *nbd,
 292                                         struct request *xreq)
 293 {
 294         struct request *req, *tmp;
 295         int err;
 296
 297         err = wait_event_interruptible(nbd->active_wq, nbd->active_req != xreq);
 298         if (unlikely(err))
 299                 return ERR_PTR(err);
 300
 301         spin_lock(&nbd->queue_lock);
 302         list_for_each_entry_safe(req, tmp, &nbd->queue_head, queuelist) {
 303                 if (req != xreq)
 304                         continue;
 305                 list_del_init(&req->queuelist);
 306                 spin_unlock(&nbd->queue_lock);
 307                 return req;
 308         }
 309         spin_unlock(&nbd->queue_lock);
 310
 311         return ERR_PTR(-ENOENT);
 312 }
 313
 314 static inline int sock_recv_bvec(struct nbd_device *nbd, struct bio_vec *bvec)
 315 {
 316         int result;
 317         void *kaddr = kmap(bvec->bv_page);
 318         result = sock_xmit(nbd, 0, kaddr + bvec->bv_offset, bvec->bv_len,
 319                         MSG_WAITALL);
 320         kunmap(bvec->bv_page);
 321         return result;
 322 }
 323
 324 /* NULL returned = something went wrong, inform userspace */
 325 static struct request *nbd_read_stat(struct nbd_device *nbd)
 326 {
 327         int result;
 328         struct nbd_reply reply;
 329         struct request *req;
 330
 331         reply.magic = 0;
 332         result = sock_xmit(nbd, 0, &reply, sizeof(reply), MSG_WAITALL);
 333         if (result <= 0) {
 334                 dev_err(disk_to_dev(nbd->disk),
 335                         "Receive control failed (result %d)\n", result);
 336                 goto harderror;
 337         }
 338
 339         if (ntohl(reply.magic) != NBD_REPLY_MAGIC) {
 340                 dev_err(disk_to_dev(nbd->disk), "Wrong magic (0x%lx)\n",
 341                                 (unsigned long)ntohl(reply.magic));
 342                 result = -EPROTO;
 343                 goto harderror;
 344         }
 345
 346         req = nbd_find_request(nbd, *(struct request **)reply.handle);
 347         if (IS_ERR(req)) {
 348                 result = PTR_ERR(req);
 349                 if (result != -ENOENT)
 350                         goto harderror;
 351
 352                 dev_err(disk_to_dev(nbd->disk), "Unexpected reply (%p)\n",
 353                         reply.handle);
 354                 result = -EBADR;
 355                 goto harderror;
 356         }
 357
 358         if (ntohl(reply.error)) {
 359                 dev_err(disk_to_dev(nbd->disk), "Other side returned error (%d)\n",
 360                         ntohl(reply.error));
 361                 req->errors++;
 362                 return req;
 363         }
 364
 365         dev_dbg(nbd_to_dev(nbd), "request %p: got reply\n", req);
 366         if (rq_data_dir(req) != WRITE) {
 367                 struct req_iterator iter;
 368                 struct bio_vec bvec;
 369
 370                 rq_for_each_segment(bvec, req, iter) {
 371                         result = sock_recv_bvec(nbd, &bvec);
 372                         if (result <= 0) {
 373                                 dev_err(disk_to_dev(nbd->disk), "Receive data failed (result %d)\n",
 374                                         result);
 375                                 req->errors++;
 376                                 return req;
 377                         }
 378                         dev_dbg(nbd_to_dev(nbd), "request %p: got %d bytes data\n",
 379                                 req, bvec.bv_len);
 380                 }
 381         }
 382         return req;
 383 harderror:
 384         nbd->harderror = result;
 385         return NULL;
 386 }
 387
 388 static ssize_t pid_show(struct device *dev,
 389                         struct device_attribute *attr, char *buf)
 390 {
 391         struct gendisk *disk = dev_to_disk(dev);
 392
 393         return sprintf(buf, "%ld\n",
 394                 (long) ((struct nbd_device *)disk->private_data)->pid);
 395 }
 396
 397 static struct device_attribute pid_attr = {
 398         .attr = { .name = "pid", .mode = S_IRUGO},
 399         .show = pid_show,
 400 };
 401
 402 static int nbd_do_it(struct nbd_device *nbd)
 403 {
 404         struct request *req;
 405         int ret;
 406
 407         BUG_ON(nbd->magic != NBD_MAGIC);
 408
 409         sk_set_memalloc(nbd->sock->sk);
 410         nbd->pid = task_pid_nr(current);
 411         ret = device_create_file(disk_to_dev(nbd->disk), &pid_attr);
 412         if (ret) {
 413                 dev_err(disk_to_dev(nbd->disk), "device_create_file failed!\n");
 414                 nbd->pid = 0;
 415                 return ret;
 416         }
 417
 418         while ((req = nbd_read_stat(nbd)) != NULL)
 419                 nbd_end_request(nbd, req);
 420
 421         device_remove_file(disk_to_dev(nbd->disk), &pid_attr);
 422         nbd->pid = 0;
 423         return 0;
 424 }
 425
 426 static void nbd_clear_que(struct nbd_device *nbd)
 427 {
 428         struct request *req;
 429
 430         BUG_ON(nbd->magic != NBD_MAGIC);
 431
 432         /*
 433          * Because we have set nbd->sock to NULL under the tx_lock, all
 434          * modifications to the list must have completed by now.  For
 435          * the same reason, the active_req must be NULL.
 436          *
 437          * As a consequence, we don't need to take the spin lock while
 438          * purging the list here.
 439          */
 440         BUG_ON(nbd->sock);
 441         BUG_ON(nbd->active_req);
 442
 443         while (!list_empty(&nbd->queue_head)) {
 444                 req = list_entry(nbd->queue_head.next, struct request,
 445                                  queuelist);
 446                 list_del_init(&req->queuelist);
 447                 req->errors++;
 448                 nbd_end_request(nbd, req);
 449         }
 450
 451         while (!list_empty(&nbd->waiting_queue)) {
 452                 req = list_entry(nbd->waiting_queue.next, struct request,
 453                                  queuelist);
 454                 list_del_init(&req->queuelist);
 455                 req->errors++;
 456                 nbd_end_request(nbd, req);
 457         }
 458 }
 459
 460
 461 static void nbd_handle_req(struct nbd_device *nbd, struct request *req)
 462 {
 463         if (req->cmd_type != REQ_TYPE_FS)
 464                 goto error_out;
 465
 466         if (rq_data_dir(req) == WRITE &&
 467             (nbd->flags & NBD_FLAG_READ_ONLY)) {
 468                 dev_err(disk_to_dev(nbd->disk),
 469                         "Write on read-only\n");
 470                 goto error_out;
 471         }
 472
 473         req->errors = 0;
 474
 475         mutex_lock(&nbd->tx_lock);
 476         if (unlikely(!nbd->sock)) {
 477                 mutex_unlock(&nbd->tx_lock);
 478                 dev_err(disk_to_dev(nbd->disk),
 479                         "Attempted send on closed socket\n");
 480                 goto error_out;
 481         }
 482
 483         nbd->active_req = req;
 484
 485         if (nbd_send_req(nbd, req) != 0) {
 486                 dev_err(disk_to_dev(nbd->disk), "Request send failed\n");
 487                 req->errors++;
 488                 nbd_end_request(nbd, req);
 489         } else {
 490                 spin_lock(&nbd->queue_lock);
 491                 list_add_tail(&req->queuelist, &nbd->queue_head);
 492                 spin_unlock(&nbd->queue_lock);
 493         }
 494
 495         nbd->active_req = NULL;
 496         mutex_unlock(&nbd->tx_lock);
 497         wake_up_all(&nbd->active_wq);
 498
 499         return;
 500
 501 error_out:
 502         req->errors++;
 503         nbd_end_request(nbd, req);
 504 }
 505
 506 static int nbd_thread(void *data)
 507 {
 508         struct nbd_device *nbd = data;
 509         struct request *req;
 510
 511         set_user_nice(current, MIN_NICE);
 512         while (!kthread_should_stop() || !list_empty(&nbd->waiting_queue)) {
 513                 /* wait for something to do */
 514                 wait_event_interruptible(nbd->waiting_wq,
 515                                          kthread_should_stop() ||
 516                                          !list_empty(&nbd->waiting_queue));
 517
 518                 /* extract request */
 519                 if (list_empty(&nbd->waiting_queue))
 520                         continue;
 521
 522                 spin_lock_irq(&nbd->queue_lock);
 523                 req = list_entry(nbd->waiting_queue.next, struct request,
 524                                  queuelist);
 525                 list_del_init(&req->queuelist);
 526                 spin_unlock_irq(&nbd->queue_lock);
 527
 528                 /* handle request */
 529                 nbd_handle_req(nbd, req);
 530         }
 531         return 0;
 532 }
 533
 534 /*
 535  * We always wait for result of write, for now. It would be nice to make it optional
 536  * in future
 537  * if ((rq_data_dir(req) == WRITE) && (nbd->flags & NBD_WRITE_NOCHK))
 538  *   { printk( "Warning: Ignoring result!\n"); nbd_end_request( req ); }
 539  */
 540
 541 static void do_nbd_request(struct request_queue *q)
 542                 __releases(q->queue_lock) __acquires(q->queue_lock)
 543 {
 544         struct request *req;
 545
 546         while ((req = blk_fetch_request(q)) != NULL) {
 547                 struct nbd_device *nbd;
 548
 549                 spin_unlock_irq(q->queue_lock);
 550
 551                 nbd = req->rq_disk->private_data;
 552
 553                 BUG_ON(nbd->magic != NBD_MAGIC);
 554
 555                 dev_dbg(nbd_to_dev(nbd), "request %p: dequeued (flags=%x)\n",
 556                         req, req->cmd_type);
 557
 558                 if (unlikely(!nbd->sock)) {
 559                         dev_err(disk_to_dev(nbd->disk),
 560                                 "Attempted send on closed socket\n");
 561                         req->errors++;
 562                         nbd_end_request(nbd, req);
 563                         spin_lock_irq(q->queue_lock);
 564                         continue;
 565                 }
 566
 567                 spin_lock_irq(&nbd->queue_lock);
 568                 list_add_tail(&req->queuelist, &nbd->waiting_queue);
 569                 spin_unlock_irq(&nbd->queue_lock);
 570
 571                 wake_up(&nbd->waiting_wq);
 572
 573                 spin_lock_irq(q->queue_lock);
 574         }
 575 }
 576
 577 /* Must be called with tx_lock held */
 578
 579 static int __nbd_ioctl(struct block_device *bdev, struct nbd_device *nbd,
 580                        unsigned int cmd, unsigned long arg)
 581 {
 582         switch (cmd) {
 583         case NBD_DISCONNECT: {
 584                 struct request sreq;
 585
 586                 dev_info(disk_to_dev(nbd->disk), "NBD_DISCONNECT\n");
 587                 if (!nbd->sock)
 588                         return -EINVAL;
 589
 590                 mutex_unlock(&nbd->tx_lock);
 591                 fsync_bdev(bdev);
 592                 mutex_lock(&nbd->tx_lock);
 593                 blk_rq_init(NULL, &sreq);
 594                 sreq.cmd_type = REQ_TYPE_DRV_PRIV;
 595
 596                 /* Check again after getting mutex back.  */
 597                 if (!nbd->sock)
 598                         return -EINVAL;
 599
 600                 nbd->disconnect = 1;
 601
 602                 nbd_send_req(nbd, &sreq);
 603                 return 0;
 604         }
 605
 606         case NBD_CLEAR_SOCK: {
 607                 struct socket *sock = nbd->sock;
 608                 nbd->sock = NULL;
 609                 nbd_clear_que(nbd);
 610                 BUG_ON(!list_empty(&nbd->queue_head));
 611                 BUG_ON(!list_empty(&nbd->waiting_queue));
 612                 kill_bdev(bdev);
 613                 if (sock)
 614                         sockfd_put(sock);
 615                 return 0;
 616         }
 617
 618         case NBD_SET_SOCK: {
 619                 struct socket *sock;
 620                 int err;
 621                 if (nbd->sock)
 622                         return -EBUSY;
 623                 sock = sockfd_lookup(arg, &err);
 624                 if (sock) {
 625                         nbd->sock = sock;
 626                         if (max_part > 0)
 627                                 bdev->bd_invalidated = 1;
 628                         nbd->disconnect = 0; /* we're connected now */
 629                         return 0;
 630                 }
 631                 return -EINVAL;
 632         }
 633
 634         case NBD_SET_BLKSIZE:
 635                 nbd->blksize = arg;
 636                 nbd->bytesize &= ~(nbd->blksize-1);
 637                 bdev->bd_inode->i_size = nbd->bytesize;
 638                 set_blocksize(bdev, nbd->blksize);
 639                 set_capacity(nbd->disk, nbd->bytesize >> 9);
 640                 return 0;
 641
 642         case NBD_SET_SIZE:
 643                 nbd->bytesize = arg & ~(nbd->blksize-1);
 644                 bdev->bd_inode->i_size = nbd->bytesize;
 645                 set_blocksize(bdev, nbd->blksize);
 646                 set_capacity(nbd->disk, nbd->bytesize >> 9);
 647                 return 0;
 648
 649         case NBD_SET_TIMEOUT:
 650                 nbd->xmit_timeout = arg * HZ;
 651                 return 0;
 652
 653         case NBD_SET_FLAGS:
 654                 nbd->flags = arg;
 655                 return 0;
 656
 657         case NBD_SET_SIZE_BLOCKS:
 658                 nbd->bytesize = ((u64) arg) * nbd->blksize;
 659                 bdev->bd_inode->i_size = nbd->bytesize;
 660                 set_blocksize(bdev, nbd->blksize);
 661                 set_capacity(nbd->disk, nbd->bytesize >> 9);
 662                 return 0;
 663
 664         case NBD_DO_IT: {
 665                 struct task_struct *thread;
 666                 struct socket *sock;
 667                 int error;
 668
 669                 if (nbd->pid)
 670                         return -EBUSY;
 671                 if (!nbd->sock)
 672                         return -EINVAL;
 673
 674                 mutex_unlock(&nbd->tx_lock);
 675
 676                 if (nbd->flags & NBD_FLAG_READ_ONLY)
 677                         set_device_ro(bdev, true);
 678                 if (nbd->flags & NBD_FLAG_SEND_TRIM)
 679                         queue_flag_set_unlocked(QUEUE_FLAG_DISCARD,
 680                                 nbd->disk->queue);
 681                 if (nbd->flags & NBD_FLAG_SEND_FLUSH)
 682                         blk_queue_flush(nbd->disk->queue, REQ_FLUSH);
 683                 else
 684                         blk_queue_flush(nbd->disk->queue, 0);
 685
 686                 thread = kthread_run(nbd_thread, nbd, "%s",
 687                                      nbd->disk->disk_name);
 688                 if (IS_ERR(thread)) {
 689                         mutex_lock(&nbd->tx_lock);
 690                         return PTR_ERR(thread);
 691                 }
 692
 693                 error = nbd_do_it(nbd);
 694                 kthread_stop(thread);
 695
 696                 mutex_lock(&nbd->tx_lock);
 697                 if (error)
 698                         return error;
 699                 sock_shutdown(nbd, 0);
 700                 sock = nbd->sock;
 701                 nbd->sock = NULL;
 702                 nbd_clear_que(nbd);
 703                 dev_warn(disk_to_dev(nbd->disk), "queue cleared\n");
 704                 kill_bdev(bdev);
 705                 queue_flag_clear_unlocked(QUEUE_FLAG_DISCARD, nbd->disk->queue);
 706                 set_device_ro(bdev, false);
 707                 if (sock)
 708                         sockfd_put(sock);
 709                 nbd->flags = 0;
 710                 nbd->bytesize = 0;
 711                 bdev->bd_inode->i_size = 0;
 712                 set_capacity(nbd->disk, 0);
 713                 if (max_part > 0)
 714                         blkdev_reread_part(bdev);
 715                 if (nbd->disconnect) /* user requested, ignore socket errors */
 716                         return 0;
 717                 return nbd->harderror;
 718         }
 719
 720         case NBD_CLEAR_QUE:
 721                 /*
 722                  * This is for compatibility only.  The queue is always cleared
 723                  * by NBD_DO_IT or NBD_CLEAR_SOCK.
 724                  */
 725                 return 0;
 726
 727         case NBD_PRINT_DEBUG:
 728                 dev_info(disk_to_dev(nbd->disk),
 729                         "next = %p, prev = %p, head = %p\n",
 730                         nbd->queue_head.next, nbd->queue_head.prev,
 731                         &nbd->queue_head);
 732                 return 0;
 733         }
 734         return -ENOTTY;
 735 }
 736
 737 static int nbd_ioctl(struct block_device *bdev, fmode_t mode,
 738                      unsigned int cmd, unsigned long arg)
 739 {
 740         struct nbd_device *nbd = bdev->bd_disk->private_data;
 741         int error;
 742
 743         if (!capable(CAP_SYS_ADMIN))
 744                 return -EPERM;
 745
 746         BUG_ON(nbd->magic != NBD_MAGIC);
 747
 748         mutex_lock(&nbd->tx_lock);
 749         error = __nbd_ioctl(bdev, nbd, cmd, arg);
 750         mutex_unlock(&nbd->tx_lock);
 751
 752         return error;
 753 }
 754
 755 static const struct block_device_operations nbd_fops =
 756 {
 757         .owner =        THIS_MODULE,
 758         .ioctl =        nbd_ioctl,
 759 };
 760
 761 /*
 762  * And here should be modules and kernel interface
 763  *  (Just smiley confuses emacs :-)
 764  */
 765
 766 static int __init nbd_init(void)
 767 {
 768         int err = -ENOMEM;
 769         int i;
 770         int part_shift;
 771
 772         BUILD_BUG_ON(sizeof(struct nbd_request) != 28);
 773
 774         if (max_part < 0) {
 775                 printk(KERN_ERR "nbd: max_part must be >= 0\n");
 776                 return -EINVAL;
 777         }
 778
 779         part_shift = 0;
 780         if (max_part > 0) {
 781                 part_shift = fls(max_part);
 782
 783                 /*
 784                  * Adjust max_part according to part_shift as it is exported
 785                  * to user space so that user can know the max number of
 786                  * partition kernel should be able to manage.
 787                  *
 788                  * Note that -1 is required because partition 0 is reserved
 789                  * for the whole disk.
 790                  */
 791                 max_part = (1UL << part_shift) - 1;
 792         }
 793
 794         if ((1UL << part_shift) > DISK_MAX_PARTS)
 795                 return -EINVAL;
 796
 797         if (nbds_max > 1UL << (MINORBITS - part_shift))
 798                 return -EINVAL;
 799
 800         nbd_dev = kcalloc(nbds_max, sizeof(*nbd_dev), GFP_KERNEL);
 801         if (!nbd_dev)
 802                 return -ENOMEM;
 803
 804         for (i = 0; i < nbds_max; i++) {
 805                 struct gendisk *disk = alloc_disk(1 << part_shift);
 806                 if (!disk)
 807                         goto out;
 808                 nbd_dev[i].disk = disk;
 809                 /*
 810                  * The new linux 2.5 block layer implementation requires
 811                  * every gendisk to have its very own request_queue struct.
 812                  * These structs are big so we dynamically allocate them.
 813                  */
 814                 disk->queue = blk_init_queue(do_nbd_request, &nbd_lock);
 815                 if (!disk->queue) {
 816                         put_disk(disk);
 817                         goto out;
 818                 }
 819                 /*
 820                  * Tell the block layer that we are not a rotational device
 821                  */
 822                 queue_flag_set_unlocked(QUEUE_FLAG_NONROT, disk->queue);
 823                 queue_flag_clear_unlocked(QUEUE_FLAG_ADD_RANDOM, disk->queue);
 824                 disk->queue->limits.discard_granularity = 512;
 825                 disk->queue->limits.max_discard_sectors = UINT_MAX;
 826                 disk->queue->limits.discard_zeroes_data = 0;
 827                 blk_queue_max_hw_sectors(disk->queue, 65536);
 828                 disk->queue->limits.max_sectors = 256;
 829         }
 830
 831         if (register_blkdev(NBD_MAJOR, "nbd")) {
 832                 err = -EIO;
 833                 goto out;
 834         }
 835
 836         printk(KERN_INFO "nbd: registered device at major %d\n", NBD_MAJOR);
 837
 838         for (i = 0; i < nbds_max; i++) {
 839                 struct gendisk *disk = nbd_dev[i].disk;
 840                 nbd_dev[i].magic = NBD_MAGIC;
 841                 INIT_LIST_HEAD(&nbd_dev[i].waiting_queue);
 842                 spin_lock_init(&nbd_dev[i].queue_lock);
 843                 INIT_LIST_HEAD(&nbd_dev[i].queue_head);
 844                 mutex_init(&nbd_dev[i].tx_lock);
 845                 init_waitqueue_head(&nbd_dev[i].active_wq);
 846                 init_waitqueue_head(&nbd_dev[i].waiting_wq);
 847                 nbd_dev[i].blksize = 1024;
 848                 nbd_dev[i].bytesize = 0;
 849                 disk->major = NBD_MAJOR;
 850                 disk->first_minor = i << part_shift;
 851                 disk->fops = &nbd_fops;
 852                 disk->private_data = &nbd_dev[i];
 853                 sprintf(disk->disk_name, "nbd%d", i);
 854                 set_capacity(disk, 0);
 855                 add_disk(disk);
 856         }
 857
 858         return 0;
 859 out:
 860         while (i--) {
 861                 blk_cleanup_queue(nbd_dev[i].disk->queue);
 862                 put_disk(nbd_dev[i].disk);
 863         }
 864         kfree(nbd_dev);
 865         return err;
 866 }
 867
 868 static void __exit nbd_cleanup(void)
 869 {
 870         int i;
 871         for (i = 0; i < nbds_max; i++) {
 872                 struct gendisk *disk = nbd_dev[i].disk;
 873                 nbd_dev[i].magic = 0;
 874                 if (disk) {
 875                         del_gendisk(disk);
 876                         blk_cleanup_queue(disk->queue);
 877                         put_disk(disk);
 878                 }
 879         }
 880         unregister_blkdev(NBD_MAJOR, "nbd");
 881         kfree(nbd_dev);
 882         printk(KERN_INFO "nbd: unregistered device at major %d\n", NBD_MAJOR);
 883 }
 884
 885 module_init(nbd_init);
 886 module_exit(nbd_cleanup);
 887
 888 MODULE_DESCRIPTION("Network Block Device");
 889 MODULE_LICENSE("GPL");
 890
 891 module_param(nbds_max, int, 0444);
 892 MODULE_PARM_DESC(nbds_max, "number of network block devices to initialize (default: 16)");
 893 module_param(max_part, int, 0444);
 894 MODULE_PARM_DESC(max_part, "number of partitions per device (default: 0)");