kernel/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
 234         memset(&request, 0, sizeof(request));
 235         request.magic = htonl(NBD_REQUEST_MAGIC);
 236         request.type = htonl(nbd_cmd(req));
 237
 238         if (nbd_cmd(req) != NBD_CMD_FLUSH && nbd_cmd(req) != NBD_CMD_DISC) {
 239                 request.from = cpu_to_be64((u64)blk_rq_pos(req) << 9);
 240                 request.len = htonl(size);
 241         }
 242         memcpy(request.handle, &req, sizeof(req));
 243
 244         dev_dbg(nbd_to_dev(nbd), "request %p: sending control (%s@%llu,%uB)\n",
 245                 req, nbdcmd_to_ascii(nbd_cmd(req)),
 246                 (unsigned long long)blk_rq_pos(req) << 9, blk_rq_bytes(req));
 247         result = sock_xmit(nbd, 1, &request, sizeof(request),
 248                         (nbd_cmd(req) == NBD_CMD_WRITE) ? MSG_MORE : 0);
 249         if (result <= 0) {
 250                 dev_err(disk_to_dev(nbd->disk),
 251                         "Send control failed (result %d)\n", result);
 252                 return -EIO;
 253         }
 254
 255         if (nbd_cmd(req) == NBD_CMD_WRITE) {
 256                 struct req_iterator iter;
 257                 struct bio_vec bvec;
 258                 /*
 259                  * we are really probing at internals to determine
 260                  * whether to set MSG_MORE or not...
 261                  */
 262                 rq_for_each_segment(bvec, req, iter) {
 263                         flags = 0;
 264                         if (!rq_iter_last(bvec, iter))
 265                                 flags = MSG_MORE;
 266                         dev_dbg(nbd_to_dev(nbd), "request %p: sending %d bytes data\n",
 267                                 req, bvec.bv_len);
 268                         result = sock_send_bvec(nbd, &bvec, flags);
 269                         if (result <= 0) {
 270                                 dev_err(disk_to_dev(nbd->disk),
 271                                         "Send data failed (result %d)\n",
 272                                         result);
 273                                 return -EIO;
 274                         }
 275                 }
 276         }
 277         return 0;
 278 }
 279
 280 static struct request *nbd_find_request(struct nbd_device *nbd,
 281                                         struct request *xreq)
 282 {
 283         struct request *req, *tmp;
 284         int err;
 285
 286         err = wait_event_interruptible(nbd->active_wq, nbd->active_req != xreq);
 287         if (unlikely(err))
 288                 return ERR_PTR(err);
 289
 290         spin_lock(&nbd->queue_lock);
 291         list_for_each_entry_safe(req, tmp, &nbd->queue_head, queuelist) {
 292                 if (req != xreq)
 293                         continue;
 294                 list_del_init(&req->queuelist);
 295                 spin_unlock(&nbd->queue_lock);
 296                 return req;
 297         }
 298         spin_unlock(&nbd->queue_lock);
 299
 300         return ERR_PTR(-ENOENT);
 301 }
 302
 303 static inline int sock_recv_bvec(struct nbd_device *nbd, struct bio_vec *bvec)
 304 {
 305         int result;
 306         void *kaddr = kmap(bvec->bv_page);
 307         result = sock_xmit(nbd, 0, kaddr + bvec->bv_offset, bvec->bv_len,
 308                         MSG_WAITALL);
 309         kunmap(bvec->bv_page);
 310         return result;
 311 }
 312
 313 /* NULL returned = something went wrong, inform userspace */
 314 static struct request *nbd_read_stat(struct nbd_device *nbd)
 315 {
 316         int result;
 317         struct nbd_reply reply;
 318         struct request *req;
 319
 320         reply.magic = 0;
 321         result = sock_xmit(nbd, 0, &reply, sizeof(reply), MSG_WAITALL);
 322         if (result <= 0) {
 323                 dev_err(disk_to_dev(nbd->disk),
 324                         "Receive control failed (result %d)\n", result);
 325                 goto harderror;
 326         }
 327
 328         if (ntohl(reply.magic) != NBD_REPLY_MAGIC) {
 329                 dev_err(disk_to_dev(nbd->disk), "Wrong magic (0x%lx)\n",
 330                                 (unsigned long)ntohl(reply.magic));
 331                 result = -EPROTO;
 332                 goto harderror;
 333         }
 334
 335         req = nbd_find_request(nbd, *(struct request **)reply.handle);
 336         if (IS_ERR(req)) {
 337                 result = PTR_ERR(req);
 338                 if (result != -ENOENT)
 339                         goto harderror;
 340
 341                 dev_err(disk_to_dev(nbd->disk), "Unexpected reply (%p)\n",
 342                         reply.handle);
 343                 result = -EBADR;
 344                 goto harderror;
 345         }
 346
 347         if (ntohl(reply.error)) {
 348                 dev_err(disk_to_dev(nbd->disk), "Other side returned error (%d)\n",
 349                         ntohl(reply.error));
 350                 req->errors++;
 351                 return req;
 352         }
 353
 354         dev_dbg(nbd_to_dev(nbd), "request %p: got reply\n", req);
 355         if (nbd_cmd(req) == NBD_CMD_READ) {
 356                 struct req_iterator iter;
 357                 struct bio_vec bvec;
 358
 359                 rq_for_each_segment(bvec, req, iter) {
 360                         result = sock_recv_bvec(nbd, &bvec);
 361                         if (result <= 0) {
 362                                 dev_err(disk_to_dev(nbd->disk), "Receive data failed (result %d)\n",
 363                                         result);
 364                                 req->errors++;
 365                                 return req;
 366                         }
 367                         dev_dbg(nbd_to_dev(nbd), "request %p: got %d bytes data\n",
 368                                 req, bvec.bv_len);
 369                 }
 370         }
 371         return req;
 372 harderror:
 373         nbd->harderror = result;
 374         return NULL;
 375 }
 376
 377 static ssize_t pid_show(struct device *dev,
 378                         struct device_attribute *attr, char *buf)
 379 {
 380         struct gendisk *disk = dev_to_disk(dev);
 381
 382         return sprintf(buf, "%ld\n",
 383                 (long) ((struct nbd_device *)disk->private_data)->pid);
 384 }
 385
 386 static struct device_attribute pid_attr = {
 387         .attr = { .name = "pid", .mode = S_IRUGO},
 388         .show = pid_show,
 389 };
 390
 391 static int nbd_do_it(struct nbd_device *nbd)
 392 {
 393         struct request *req;
 394         int ret;
 395
 396         BUG_ON(nbd->magic != NBD_MAGIC);
 397
 398         sk_set_memalloc(nbd->sock->sk);
 399         nbd->pid = task_pid_nr(current);
 400         ret = device_create_file(disk_to_dev(nbd->disk), &pid_attr);
 401         if (ret) {
 402                 dev_err(disk_to_dev(nbd->disk), "device_create_file failed!\n");
 403                 nbd->pid = 0;
 404                 return ret;
 405         }
 406
 407         while ((req = nbd_read_stat(nbd)) != NULL)
 408                 nbd_end_request(nbd, req);
 409
 410         device_remove_file(disk_to_dev(nbd->disk), &pid_attr);
 411         nbd->pid = 0;
 412         return 0;
 413 }
 414
 415 static void nbd_clear_que(struct nbd_device *nbd)
 416 {
 417         struct request *req;
 418
 419         BUG_ON(nbd->magic != NBD_MAGIC);
 420
 421         /*
 422          * Because we have set nbd->sock to NULL under the tx_lock, all
 423          * modifications to the list must have completed by now.  For
 424          * the same reason, the active_req must be NULL.
 425          *
 426          * As a consequence, we don't need to take the spin lock while
 427          * purging the list here.
 428          */
 429         BUG_ON(nbd->sock);
 430         BUG_ON(nbd->active_req);
 431
 432         while (!list_empty(&nbd->queue_head)) {
 433                 req = list_entry(nbd->queue_head.next, struct request,
 434                                  queuelist);
 435                 list_del_init(&req->queuelist);
 436                 req->errors++;
 437                 nbd_end_request(nbd, req);
 438         }
 439
 440         while (!list_empty(&nbd->waiting_queue)) {
 441                 req = list_entry(nbd->waiting_queue.next, struct request,
 442                                  queuelist);
 443                 list_del_init(&req->queuelist);
 444                 req->errors++;
 445                 nbd_end_request(nbd, req);
 446         }
 447 }
 448
 449
 450 static void nbd_handle_req(struct nbd_device *nbd, struct request *req)
 451 {
 452         if (req->cmd_type != REQ_TYPE_FS)
 453                 goto error_out;
 454
 455         nbd_cmd(req) = NBD_CMD_READ;
 456         if (rq_data_dir(req) == WRITE) {
 457                 if ((req->cmd_flags & REQ_DISCARD)) {
 458                         WARN_ON(!(nbd->flags & NBD_FLAG_SEND_TRIM));
 459                         nbd_cmd(req) = NBD_CMD_TRIM;
 460                 } else
 461                         nbd_cmd(req) = NBD_CMD_WRITE;
 462                 if (nbd->flags & NBD_FLAG_READ_ONLY) {
 463                         dev_err(disk_to_dev(nbd->disk),
 464                                 "Write on read-only\n");
 465                         goto error_out;
 466                 }
 467         }
 468
 469         if (req->cmd_flags & REQ_FLUSH) {
 470                 BUG_ON(unlikely(blk_rq_sectors(req)));
 471                 nbd_cmd(req) = NBD_CMD_FLUSH;
 472         }
 473
 474         req->errors = 0;
 475
 476         mutex_lock(&nbd->tx_lock);
 477         if (unlikely(!nbd->sock)) {
 478                 mutex_unlock(&nbd->tx_lock);
 479                 dev_err(disk_to_dev(nbd->disk),
 480                         "Attempted send on closed socket\n");
 481                 goto error_out;
 482         }
 483
 484         nbd->active_req = req;
 485
 486         if (nbd_send_req(nbd, req) != 0) {
 487                 dev_err(disk_to_dev(nbd->disk), "Request send failed\n");
 488                 req->errors++;
 489                 nbd_end_request(nbd, req);
 490         } else {
 491                 spin_lock(&nbd->queue_lock);
 492                 list_add_tail(&req->queuelist, &nbd->queue_head);
 493                 spin_unlock(&nbd->queue_lock);
 494         }
 495
 496         nbd->active_req = NULL;
 497         mutex_unlock(&nbd->tx_lock);
 498         wake_up_all(&nbd->active_wq);
 499
 500         return;
 501
 502 error_out:
 503         req->errors++;
 504         nbd_end_request(nbd, req);
 505 }
 506
 507 static int nbd_thread(void *data)
 508 {
 509         struct nbd_device *nbd = data;
 510         struct request *req;
 511
 512         set_user_nice(current, MIN_NICE);
 513         while (!kthread_should_stop() || !list_empty(&nbd->waiting_queue)) {
 514                 /* wait for something to do */
 515                 wait_event_interruptible(nbd->waiting_wq,
 516                                          kthread_should_stop() ||
 517                                          !list_empty(&nbd->waiting_queue));
 518
 519                 /* extract request */
 520                 if (list_empty(&nbd->waiting_queue))
 521                         continue;
 522
 523                 spin_lock_irq(&nbd->queue_lock);
 524                 req = list_entry(nbd->waiting_queue.next, struct request,
 525                                  queuelist);
 526                 list_del_init(&req->queuelist);
 527                 spin_unlock_irq(&nbd->queue_lock);
 528
 529                 /* handle request */
 530                 nbd_handle_req(nbd, req);
 531         }
 532         return 0;
 533 }
 534
 535 /*
 536  * We always wait for result of write, for now. It would be nice to make it optional
 537  * in future
 538  * if ((rq_data_dir(req) == WRITE) && (nbd->flags & NBD_WRITE_NOCHK))
 539  *   { printk( "Warning: Ignoring result!\n"); nbd_end_request( req ); }
 540  */
 541
 542 static void do_nbd_request(struct request_queue *q)
 543                 __releases(q->queue_lock) __acquires(q->queue_lock)
 544 {
 545         struct request *req;
 546
 547         while ((req = blk_fetch_request(q)) != NULL) {
 548                 struct nbd_device *nbd;
 549
 550                 spin_unlock_irq(q->queue_lock);
 551
 552                 nbd = req->rq_disk->private_data;
 553
 554                 BUG_ON(nbd->magic != NBD_MAGIC);
 555
 556                 dev_dbg(nbd_to_dev(nbd), "request %p: dequeued (flags=%x)\n",
 557                         req, req->cmd_type);
 558
 559                 if (unlikely(!nbd->sock)) {
 560                         dev_err(disk_to_dev(nbd->disk),
 561                                 "Attempted send on closed socket\n");
 562                         req->errors++;
 563                         nbd_end_request(nbd, req);
 564                         spin_lock_irq(q->queue_lock);
 565                         continue;
 566                 }
 567
 568                 spin_lock_irq(&nbd->queue_lock);
 569                 list_add_tail(&req->queuelist, &nbd->waiting_queue);
 570                 spin_unlock_irq(&nbd->queue_lock);
 571
 572                 wake_up(&nbd->waiting_wq);
 573
 574                 spin_lock_irq(q->queue_lock);
 575         }
 576 }
 577
 578 /* Must be called with tx_lock held */
 579
 580 static int __nbd_ioctl(struct block_device *bdev, struct nbd_device *nbd,
 581                        unsigned int cmd, unsigned long arg)
 582 {
 583         switch (cmd) {
 584         case NBD_DISCONNECT: {
 585                 struct request sreq;
 586
 587                 dev_info(disk_to_dev(nbd->disk), "NBD_DISCONNECT\n");
 588                 if (!nbd->sock)
 589                         return -EINVAL;
 590
 591                 mutex_unlock(&nbd->tx_lock);
 592                 fsync_bdev(bdev);
 593                 mutex_lock(&nbd->tx_lock);
 594                 blk_rq_init(NULL, &sreq);
 595                 sreq.cmd_type = REQ_TYPE_SPECIAL;
 596                 nbd_cmd(&sreq) = NBD_CMD_DISC;
 597
 598                 /* Check again after getting mutex back.  */
 599                 if (!nbd->sock)
 600                         return -EINVAL;
 601
 602                 nbd->disconnect = 1;
 603
 604                 nbd_send_req(nbd, &sreq);
 605                 return 0;
 606         }
 607
 608         case NBD_CLEAR_SOCK: {
 609                 struct socket *sock = nbd->sock;
 610                 nbd->sock = NULL;
 611                 nbd_clear_que(nbd);
 612                 BUG_ON(!list_empty(&nbd->queue_head));
 613                 BUG_ON(!list_empty(&nbd->waiting_queue));
 614                 kill_bdev(bdev);
 615                 if (sock)
 616                         sockfd_put(sock);
 617                 return 0;
 618         }
 619
 620         case NBD_SET_SOCK: {
 621                 struct socket *sock;
 622                 int err;
 623                 if (nbd->sock)
 624                         return -EBUSY;
 625                 sock = sockfd_lookup(arg, &err);
 626                 if (sock) {
 627                         nbd->sock = sock;
 628                         if (max_part > 0)
 629                                 bdev->bd_invalidated = 1;
 630                         nbd->disconnect = 0; /* we're connected now */
 631                         return 0;
 632                 }
 633                 return -EINVAL;
 634         }
 635
 636         case NBD_SET_BLKSIZE:
 637                 nbd->blksize = arg;
 638                 nbd->bytesize &= ~(nbd->blksize-1);
 639                 bdev->bd_inode->i_size = nbd->bytesize;
 640                 set_blocksize(bdev, nbd->blksize);
 641                 set_capacity(nbd->disk, nbd->bytesize >> 9);
 642                 return 0;
 643
 644         case NBD_SET_SIZE:
 645                 nbd->bytesize = arg & ~(nbd->blksize-1);
 646                 bdev->bd_inode->i_size = nbd->bytesize;
 647                 set_blocksize(bdev, nbd->blksize);
 648                 set_capacity(nbd->disk, nbd->bytesize >> 9);
 649                 return 0;
 650
 651         case NBD_SET_TIMEOUT:
 652                 nbd->xmit_timeout = arg * HZ;
 653                 return 0;
 654
 655         case NBD_SET_FLAGS:
 656                 nbd->flags = arg;
 657                 return 0;
 658
 659         case NBD_SET_SIZE_BLOCKS:
 660                 nbd->bytesize = ((u64) arg) * nbd->blksize;
 661                 bdev->bd_inode->i_size = nbd->bytesize;
 662                 set_blocksize(bdev, nbd->blksize);
 663                 set_capacity(nbd->disk, nbd->bytesize >> 9);
 664                 return 0;
 665
 666         case NBD_DO_IT: {
 667                 struct task_struct *thread;
 668                 struct socket *sock;
 669                 int error;
 670
 671                 if (nbd->pid)
 672                         return -EBUSY;
 673                 if (!nbd->sock)
 674                         return -EINVAL;
 675
 676                 mutex_unlock(&nbd->tx_lock);
 677
 678                 if (nbd->flags & NBD_FLAG_READ_ONLY)
 679                         set_device_ro(bdev, true);
 680                 if (nbd->flags & NBD_FLAG_SEND_TRIM)
 681                         queue_flag_set_unlocked(QUEUE_FLAG_DISCARD,
 682                                 nbd->disk->queue);
 683                 if (nbd->flags & NBD_FLAG_SEND_FLUSH)
 684                         blk_queue_flush(nbd->disk->queue, REQ_FLUSH);
 685                 else
 686                         blk_queue_flush(nbd->disk->queue, 0);
 687
 688                 thread = kthread_run(nbd_thread, nbd, "%s",
 689                                      nbd->disk->disk_name);
 690                 if (IS_ERR(thread)) {
 691                         mutex_lock(&nbd->tx_lock);
 692                         return PTR_ERR(thread);
 693                 }
 694
 695                 error = nbd_do_it(nbd);
 696                 kthread_stop(thread);
 697
 698                 mutex_lock(&nbd->tx_lock);
 699                 if (error)
 700                         return error;
 701                 sock_shutdown(nbd, 0);
 702                 sock = nbd->sock;
 703                 nbd->sock = NULL;
 704                 nbd_clear_que(nbd);
 705                 dev_warn(disk_to_dev(nbd->disk), "queue cleared\n");
 706                 kill_bdev(bdev);
 707                 queue_flag_clear_unlocked(QUEUE_FLAG_DISCARD, nbd->disk->queue);
 708                 set_device_ro(bdev, false);
 709                 if (sock)
 710                         sockfd_put(sock);
 711                 nbd->flags = 0;
 712                 nbd->bytesize = 0;
 713                 bdev->bd_inode->i_size = 0;
 714                 set_capacity(nbd->disk, 0);
 715                 if (max_part > 0)
 716                         ioctl_by_bdev(bdev, BLKRRPART, 0);
 717                 if (nbd->disconnect) /* user requested, ignore socket errors */
 718                         return 0;
 719                 return nbd->harderror;
 720         }
 721
 722         case NBD_CLEAR_QUE:
 723                 /*
 724                  * This is for compatibility only.  The queue is always cleared
 725                  * by NBD_DO_IT or NBD_CLEAR_SOCK.
 726                  */
 727                 return 0;
 728
 729         case NBD_PRINT_DEBUG:
 730                 dev_info(disk_to_dev(nbd->disk),
 731                         "next = %p, prev = %p, head = %p\n",
 732                         nbd->queue_head.next, nbd->queue_head.prev,
 733                         &nbd->queue_head);
 734                 return 0;
 735         }
 736         return -ENOTTY;
 737 }
 738
 739 static int nbd_ioctl(struct block_device *bdev, fmode_t mode,
 740                      unsigned int cmd, unsigned long arg)
 741 {
 742         struct nbd_device *nbd = bdev->bd_disk->private_data;
 743         int error;
 744
 745         if (!capable(CAP_SYS_ADMIN))
 746                 return -EPERM;
 747
 748         BUG_ON(nbd->magic != NBD_MAGIC);
 749
 750         mutex_lock(&nbd->tx_lock);
 751         error = __nbd_ioctl(bdev, nbd, cmd, arg);
 752         mutex_unlock(&nbd->tx_lock);
 753
 754         return error;
 755 }
 756
 757 static const struct block_device_operations nbd_fops =
 758 {
 759         .owner =        THIS_MODULE,
 760         .ioctl =        nbd_ioctl,
 761 };
 762
 763 /*
 764  * And here should be modules and kernel interface
 765  *  (Just smiley confuses emacs :-)
 766  */
 767
 768 static int __init nbd_init(void)
 769 {
 770         int err = -ENOMEM;
 771         int i;
 772         int part_shift;
 773
 774         BUILD_BUG_ON(sizeof(struct nbd_request) != 28);
 775
 776         if (max_part < 0) {
 777                 printk(KERN_ERR "nbd: max_part must be >= 0\n");
 778                 return -EINVAL;
 779         }
 780
 781         part_shift = 0;
 782         if (max_part > 0) {
 783                 part_shift = fls(max_part);
 784
 785                 /*
 786                  * Adjust max_part according to part_shift as it is exported
 787                  * to user space so that user can know the max number of
 788                  * partition kernel should be able to manage.
 789                  *
 790                  * Note that -1 is required because partition 0 is reserved
 791                  * for the whole disk.
 792                  */
 793                 max_part = (1UL << part_shift) - 1;
 794         }
 795
 796         if ((1UL << part_shift) > DISK_MAX_PARTS)
 797                 return -EINVAL;
 798
 799         if (nbds_max > 1UL << (MINORBITS - part_shift))
 800                 return -EINVAL;
 801
 802         nbd_dev = kcalloc(nbds_max, sizeof(*nbd_dev), GFP_KERNEL);
 803         if (!nbd_dev)
 804                 return -ENOMEM;
 805
 806         for (i = 0; i < nbds_max; i++) {
 807                 struct gendisk *disk = alloc_disk(1 << part_shift);
 808                 if (!disk)
 809                         goto out;
 810                 nbd_dev[i].disk = disk;
 811                 /*
 812                  * The new linux 2.5 block layer implementation requires
 813                  * every gendisk to have its very own request_queue struct.
 814                  * These structs are big so we dynamically allocate them.
 815                  */
 816                 disk->queue = blk_init_queue(do_nbd_request, &nbd_lock);
 817                 if (!disk->queue) {
 818                         put_disk(disk);
 819                         goto out;
 820                 }
 821                 /*
 822                  * Tell the block layer that we are not a rotational device
 823                  */
 824                 queue_flag_set_unlocked(QUEUE_FLAG_NONROT, disk->queue);
 825                 queue_flag_clear_unlocked(QUEUE_FLAG_ADD_RANDOM, disk->queue);
 826                 disk->queue->limits.discard_granularity = 512;
 827                 disk->queue->limits.max_discard_sectors = UINT_MAX;
 828                 disk->queue->limits.discard_zeroes_data = 0;
 829                 blk_queue_max_hw_sectors(disk->queue, 65536);
 830                 disk->queue->limits.max_sectors = 256;
 831         }
 832
 833         if (register_blkdev(NBD_MAJOR, "nbd")) {
 834                 err = -EIO;
 835                 goto out;
 836         }
 837
 838         printk(KERN_INFO "nbd: registered device at major %d\n", NBD_MAJOR);
 839
 840         for (i = 0; i < nbds_max; i++) {
 841                 struct gendisk *disk = nbd_dev[i].disk;
 842                 nbd_dev[i].magic = NBD_MAGIC;
 843                 INIT_LIST_HEAD(&nbd_dev[i].waiting_queue);
 844                 spin_lock_init(&nbd_dev[i].queue_lock);
 845                 INIT_LIST_HEAD(&nbd_dev[i].queue_head);
 846                 mutex_init(&nbd_dev[i].tx_lock);
 847                 init_waitqueue_head(&nbd_dev[i].active_wq);
 848                 init_waitqueue_head(&nbd_dev[i].waiting_wq);
 849                 nbd_dev[i].blksize = 1024;
 850                 nbd_dev[i].bytesize = 0;
 851                 disk->major = NBD_MAJOR;
 852                 disk->first_minor = i << part_shift;
 853                 disk->fops = &nbd_fops;
 854                 disk->private_data = &nbd_dev[i];
 855                 sprintf(disk->disk_name, "nbd%d", i);
 856                 set_capacity(disk, 0);
 857                 add_disk(disk);
 858         }
 859
 860         return 0;
 861 out:
 862         while (i--) {
 863                 blk_cleanup_queue(nbd_dev[i].disk->queue);
 864                 put_disk(nbd_dev[i].disk);
 865         }
 866         kfree(nbd_dev);
 867         return err;
 868 }
 869
 870 static void __exit nbd_cleanup(void)
 871 {
 872         int i;
 873         for (i = 0; i < nbds_max; i++) {
 874                 struct gendisk *disk = nbd_dev[i].disk;
 875                 nbd_dev[i].magic = 0;
 876                 if (disk) {
 877                         del_gendisk(disk);
 878                         blk_cleanup_queue(disk->queue);
 879                         put_disk(disk);
 880                 }
 881         }
 882         unregister_blkdev(NBD_MAJOR, "nbd");
 883         kfree(nbd_dev);
 884         printk(KERN_INFO "nbd: unregistered device at major %d\n", NBD_MAJOR);
 885 }
 886
 887 module_init(nbd_init);
 888 module_exit(nbd_cleanup);
 889
 890 MODULE_DESCRIPTION("Network Block Device");
 891 MODULE_LICENSE("GPL");
 892
 893 module_param(nbds_max, int, 0444);
 894 MODULE_PARM_DESC(nbds_max, "number of network block devices to initialize (default: 16)");
 895 module_param(max_part, int, 0444);
 896 MODULE_PARM_DESC(max_part, "number of partitions per device (default: 0)");