/* * Network block device - make block devices work over TCP * * Note that you can not swap over this thing, yet. Seems to work but * deadlocks sometimes - you can not swap over TCP in general. * * Copyright 1997-2000, 2008 Pavel Machek <pavel@ucw.cz> * Parts copyright 2001 Steven Whitehouse <steve@chygwyn.com> * * This file is released under GPLv2 or later. * * (part of code stolen from loop.c) */ #include <linux/major.h> #include <linux/blkdev.h> #include <linux/module.h> #include <linux/init.h> #include <linux/sched.h> #include <linux/fs.h> #include <linux/bio.h> #include <linux/stat.h> #include <linux/errno.h> #include <linux/file.h> #include <linux/ioctl.h> #include <linux/mutex.h> #include <linux/compiler.h> #include <linux/err.h> #include <linux/kernel.h> #include <linux/slab.h> #include <net/sock.h> #include <linux/net.h> #include <linux/kthread.h> #include <linux/types.h> #include <asm/uaccess.h> #include <asm/types.h> #include <linux/nbd.h> struct nbd_device { int flags; int harderror; /* Code of hard error */ struct socket * sock; /* If == NULL, device is not ready, yet */ int magic; spinlock_t queue_lock; struct list_head queue_head; /* Requests waiting result */ struct request *active_req; wait_queue_head_t active_wq; struct list_head waiting_queue; /* Requests to be sent */ wait_queue_head_t waiting_wq; struct mutex tx_lock; struct gendisk *disk; int blksize; loff_t bytesize; pid_t pid; /* pid of nbd-client, if attached */ int xmit_timeout; int disconnect; /* a disconnect has been requested by user */ }; #define NBD_MAGIC 0x68797548 static unsigned int nbds_max = 16; static struct nbd_device *nbd_dev; static int max_part; /* * Use just one lock (or at most 1 per NIC). Two arguments for this: * 1. Each NIC is essentially a synchronization point for all servers * accessed through that NIC so there's no need to have more locks * than NICs anyway. * 2. More locks lead to more "Dirty cache line bouncing" which will slow * down each lock to the point where they're actually slower than just * a single lock. * Thanks go to Jens Axboe and Al Viro for their LKML emails explaining this! */ static DEFINE_SPINLOCK(nbd_lock); static inline struct device *nbd_to_dev(struct nbd_device *nbd) { return disk_to_dev(nbd->disk); } static const char *nbdcmd_to_ascii(int cmd) { switch (cmd) { case NBD_CMD_READ: return "read"; case NBD_CMD_WRITE: return "write"; case NBD_CMD_DISC: return "disconnect"; case NBD_CMD_FLUSH: return "flush"; case NBD_CMD_TRIM: return "trim/discard"; } return "invalid"; } static void nbd_end_request(struct nbd_device *nbd, struct request *req) { int error = req->errors ? -EIO : 0; struct request_queue *q = req->q; unsigned long flags; dev_dbg(nbd_to_dev(nbd), "request %p: %s\n", req, error ? "failed" : "done"); spin_lock_irqsave(q->queue_lock, flags); __blk_end_request_all(req, error); spin_unlock_irqrestore(q->queue_lock, flags); } /* * Forcibly shutdown the socket causing all listeners to error */ static void sock_shutdown(struct nbd_device *nbd, int lock) { if (lock) mutex_lock(&nbd->tx_lock); if (nbd->sock) { dev_warn(disk_to_dev(nbd->disk), "shutting down socket\n"); kernel_sock_shutdown(nbd->sock, SHUT_RDWR); nbd->sock = NULL; } if (lock) mutex_unlock(&nbd->tx_lock); } static void nbd_xmit_timeout(unsigned long arg) { struct task_struct *task = (struct task_struct *)arg; printk(KERN_WARNING "nbd: killing hung xmit (%s, pid: %d)\n", task->comm, task->pid); force_sig(SIGKILL, task); } /* * Send or receive packet. */ static int sock_xmit(struct nbd_device *nbd, int send, void *buf, int size, int msg_flags) { struct socket *sock = nbd->sock; int result; struct msghdr msg; struct kvec iov; sigset_t blocked, oldset; unsigned long pflags = current->flags; if (unlikely(!sock)) { dev_err(disk_to_dev(nbd->disk), "Attempted %s on closed socket in sock_xmit\n", (send ? "send" : "recv")); return -EINVAL; } /* Allow interception of SIGKILL only * Don't allow other signals to interrupt the transmission */ siginitsetinv(&blocked, sigmask(SIGKILL)); sigprocmask(SIG_SETMASK, &blocked, &oldset); current->flags |= PF_MEMALLOC; do { sock->sk->sk_allocation = GFP_NOIO | __GFP_MEMALLOC; iov.iov_base = buf; iov.iov_len = size; msg.msg_name = NULL; msg.msg_namelen = 0; msg.msg_control = NULL; msg.msg_controllen = 0; msg.msg_flags = msg_flags | MSG_NOSIGNAL; if (send) { struct timer_list ti; if (nbd->xmit_timeout) { init_timer(&ti); ti.function = nbd_xmit_timeout; ti.data = (unsigned long)current; ti.expires = jiffies + nbd->xmit_timeout; add_timer(&ti); } result = kernel_sendmsg(sock, &msg, &iov, 1, size); if (nbd->xmit_timeout) del_timer_sync(&ti); } else result = kernel_recvmsg(sock, &msg, &iov, 1, size, msg.msg_flags); if (signal_pending(current)) { siginfo_t info; printk(KERN_WARNING "nbd (pid %d: %s) got signal %d\n", task_pid_nr(current), current->comm, dequeue_signal_lock(current, ¤t->blocked, &info)); result = -EINTR; sock_shutdown(nbd, !send); break; } if (result <= 0) { if (result == 0) result = -EPIPE; /* short read */ break; } size -= result; buf += result; } while (size > 0); sigprocmask(SIG_SETMASK, &oldset, NULL); tsk_restore_flags(current, pflags, PF_MEMALLOC); return result; } static inline int sock_send_bvec(struct nbd_device *nbd, struct bio_vec *bvec, int flags) { int result; void *kaddr = kmap(bvec->bv_page); result = sock_xmit(nbd, 1, kaddr + bvec->bv_offset, bvec->bv_len, flags); kunmap(bvec->bv_page); return result; } /* always call with the tx_lock held */ static int nbd_send_req(struct nbd_device *nbd, struct request *req) { int result, flags; struct nbd_request request; unsigned long size = blk_rq_bytes(req); u32 type; if (req->cmd_type == REQ_TYPE_DRV_PRIV) type = NBD_CMD_DISC; else if (req->cmd_flags & REQ_DISCARD) type = NBD_CMD_TRIM; else if (req->cmd_flags & REQ_FLUSH) type = NBD_CMD_FLUSH; else if (rq_data_dir(req) == WRITE) type = NBD_CMD_WRITE; else type = NBD_CMD_READ; memset(&request, 0, sizeof(request)); request.magic = htonl(NBD_REQUEST_MAGIC); request.type = htonl(type); if (type != NBD_CMD_FLUSH && type != NBD_CMD_DISC) { request.from = cpu_to_be64((u64)blk_rq_pos(req) << 9); request.len = htonl(size); } memcpy(request.handle, &req, sizeof(req)); dev_dbg(nbd_to_dev(nbd), "request %p: sending control (%s@%llu,%uB)\n", req, nbdcmd_to_ascii(type), (unsigned long long)blk_rq_pos(req) << 9, blk_rq_bytes(req)); result = sock_xmit(nbd, 1, &request, sizeof(request), (type == NBD_CMD_WRITE) ? MSG_MORE : 0); if (result <= 0) { dev_err(disk_to_dev(nbd->disk), "Send control failed (result %d)\n", result); return -EIO; } if (type == NBD_CMD_WRITE) { struct req_iterator iter; struct bio_vec bvec; /* * we are really probing at internals to determine * whether to set MSG_MORE or not... */ rq_for_each_segment(bvec, req, iter) { flags = 0; if (!rq_iter_last(bvec, iter)) flags = MSG_MORE; dev_dbg(nbd_to_dev(nbd), "request %p: sending %d bytes data\n", req, bvec.bv_len); result = sock_send_bvec(nbd, &bvec, flags); if (result <= 0) { dev_err(disk_to_dev(nbd->disk), "Send data failed (result %d)\n", result); return -EIO; } } } return 0; } static struct request *nbd_find_request(struct nbd_device *nbd, struct request *xreq) { struct request *req, *tmp; int err; err = wait_event_interruptible(nbd->active_wq, nbd->active_req != xreq); if (unlikely(err)) return ERR_PTR(err); spin_lock(&nbd->queue_lock); list_for_each_entry_safe(req, tmp, &nbd->queue_head, queuelist) { if (req != xreq) continue; list_del_init(&req->queuelist); spin_unlock(&nbd->queue_lock); return req; } spin_unlock(&nbd->queue_lock); return ERR_PTR(-ENOENT); } static inline int sock_recv_bvec(struct nbd_device *nbd, struct bio_vec *bvec) { int result; void *kaddr = kmap(bvec->bv_page); result = sock_xmit(nbd, 0, kaddr + bvec->bv_offset, bvec->bv_len, MSG_WAITALL); kunmap(bvec->bv_page); return result; } /* NULL returned = something went wrong, inform userspace */ static struct request *nbd_read_stat(struct nbd_device *nbd) { int result; struct nbd_reply reply; struct request *req; reply.magic = 0; result = sock_xmit(nbd, 0, &reply, sizeof(reply), MSG_WAITALL); if (result <= 0) { dev_err(disk_to_dev(nbd->disk), "Receive control failed (result %d)\n", result); goto harderror; } if (ntohl(reply.magic) != NBD_REPLY_MAGIC) { dev_err(disk_to_dev(nbd->disk), "Wrong magic (0x%lx)\n", (unsigned long)ntohl(reply.magic)); result = -EPROTO; goto harderror; } req = nbd_find_request(nbd, *(struct request **)reply.handle); if (IS_ERR(req)) { result = PTR_ERR(req); if (result != -ENOENT) goto harderror; dev_err(disk_to_dev(nbd->disk), "Unexpected reply (%p)\n", reply.handle); result = -EBADR; goto harderror; } if (ntohl(reply.error)) { dev_err(disk_to_dev(nbd->disk), "Other side returned error (%d)\n", ntohl(reply.error)); req->errors++; return req; } dev_dbg(nbd_to_dev(nbd), "request %p: got reply\n", req); if (rq_data_dir(req) != WRITE) { struct req_iterator iter; struct bio_vec bvec; rq_for_each_segment(bvec, req, iter) { result = sock_recv_bvec(nbd, &bvec); if (result <= 0) { dev_err(disk_to_dev(nbd->disk), "Receive data failed (result %d)\n", result); req->errors++; return req; } dev_dbg(nbd_to_dev(nbd), "request %p: got %d bytes data\n", req, bvec.bv_len); } } return req; harderror: nbd->harderror = result; return NULL; } static ssize_t pid_show(struct device *dev, struct device_attribute *attr, char *buf) { struct gendisk *disk = dev_to_disk(dev); return sprintf(buf, "%ld\n", (long) ((struct nbd_device *)disk->private_data)->pid); } static struct device_attribute pid_attr = { .attr = { .name = "pid", .mode = S_IRUGO}, .show = pid_show, }; static int nbd_do_it(struct nbd_device *nbd) { struct request *req; int ret; BUG_ON(nbd->magic != NBD_MAGIC); sk_set_memalloc(nbd->sock->sk); nbd->pid = task_pid_nr(current); ret = device_create_file(disk_to_dev(nbd->disk), &pid_attr); if (ret) { dev_err(disk_to_dev(nbd->disk), "device_create_file failed!\n"); nbd->pid = 0; return ret; } while ((req = nbd_read_stat(nbd)) != NULL) nbd_end_request(nbd, req); device_remove_file(disk_to_dev(nbd->disk), &pid_attr); nbd->pid = 0; return 0; } static void nbd_clear_que(struct nbd_device *nbd) { struct request *req; BUG_ON(nbd->magic != NBD_MAGIC); /* * Because we have set nbd->sock to NULL under the tx_lock, all * modifications to the list must have completed by now. For * the same reason, the active_req must be NULL. * * As a consequence, we don't need to take the spin lock while * purging the list here. */ BUG_ON(nbd->sock); BUG_ON(nbd->active_req); while (!list_empty(&nbd->queue_head)) { req = list_entry(nbd->queue_head.next, struct request, queuelist); list_del_init(&req->queuelist); req->errors++; nbd_end_request(nbd, req); } while (!list_empty(&nbd->waiting_queue)) { req = list_entry(nbd->waiting_queue.next, struct request, queuelist); list_del_init(&req->queuelist); req->errors++; nbd_end_request(nbd, req); } } static void nbd_handle_req(struct nbd_device *nbd, struct request *req) { if (req->cmd_type != REQ_TYPE_FS) goto error_out; if (rq_data_dir(req) == WRITE && (nbd->flags & NBD_FLAG_READ_ONLY)) { dev_err(disk_to_dev(nbd->disk), "Write on read-only\n"); goto error_out; } req->errors = 0; mutex_lock(&nbd->tx_lock); if (unlikely(!nbd->sock)) { mutex_unlock(&nbd->tx_lock); dev_err(disk_to_dev(nbd->disk), "Attempted send on closed socket\n"); goto error_out; } nbd->active_req = req; if (nbd_send_req(nbd, req) != 0) { dev_err(disk_to_dev(nbd->disk), "Request send failed\n"); req->errors++; nbd_end_request(nbd, req); } else { spin_lock(&nbd->queue_lock); list_add_tail(&req->queuelist, &nbd->queue_head); spin_unlock(&nbd->queue_lock); } nbd->active_req = NULL; mutex_unlock(&nbd->tx_lock); wake_up_all(&nbd->active_wq); return; error_out: req->errors++; nbd_end_request(nbd, req); } static int nbd_thread(void *data) { struct nbd_device *nbd = data; struct request *req; set_user_nice(current, MIN_NICE); while (!kthread_should_stop() || !list_empty(&nbd->waiting_queue)) { /* wait for something to do */ wait_event_interruptible(nbd->waiting_wq, kthread_should_stop() || !list_empty(&nbd->waiting_queue)); /* extract request */ if (list_empty(&nbd->waiting_queue)) continue; spin_lock_irq(&nbd->queue_lock); req = list_entry(nbd->waiting_queue.next, struct request, queuelist); list_del_init(&req->queuelist); spin_unlock_irq(&nbd->queue_lock); /* handle request */ nbd_handle_req(nbd, req); } return 0; } /* * We always wait for result of write, for now. It would be nice to make it optional * in future * if ((rq_data_dir(req) == WRITE) && (nbd->flags & NBD_WRITE_NOCHK)) * { printk( "Warning: Ignoring result!\n"); nbd_end_request( req ); } */ static void do_nbd_request(struct request_queue *q) __releases(q->queue_lock) __acquires(q->queue_lock) { struct request *req; while ((req = blk_fetch_request(q)) != NULL) { struct nbd_device *nbd; spin_unlock_irq(q->queue_lock); nbd = req->rq_disk->private_data; BUG_ON(nbd->magic != NBD_MAGIC); dev_dbg(nbd_to_dev(nbd), "request %p: dequeued (flags=%x)\n", req, req->cmd_type); if (unlikely(!nbd->sock)) { dev_err(disk_to_dev(nbd->disk), "Attempted send on closed socket\n"); req->errors++; nbd_end_request(nbd, req); spin_lock_irq(q->queue_lock); continue; } spin_lock_irq(&nbd->queue_lock); list_add_tail(&req->queuelist, &nbd->waiting_queue); spin_unlock_irq(&nbd->queue_lock); wake_up(&nbd->waiting_wq); spin_lock_irq(q->queue_lock); } } /* Must be called with tx_lock held */ static int __nbd_ioctl(struct block_device *bdev, struct nbd_device *nbd, unsigned int cmd, unsigned long arg) { switch (cmd) { case NBD_DISCONNECT: { struct request sreq; dev_info(disk_to_dev(nbd->disk), "NBD_DISCONNECT\n"); if (!nbd->sock) return -EINVAL; mutex_unlock(&nbd->tx_lock); fsync_bdev(bdev); mutex_lock(&nbd->tx_lock); blk_rq_init(NULL, &sreq); sreq.cmd_type = REQ_TYPE_DRV_PRIV; /* Check again after getting mutex back. */ if (!nbd->sock) return -EINVAL; nbd->disconnect = 1; nbd_send_req(nbd, &sreq); return 0; } case NBD_CLEAR_SOCK: { struct socket *sock = nbd->sock; nbd->sock = NULL; nbd_clear_que(nbd); BUG_ON(!list_empty(&nbd->queue_head)); BUG_ON(!list_empty(&nbd->waiting_queue)); kill_bdev(bdev); if (sock) sockfd_put(sock); return 0; } case NBD_SET_SOCK: { struct socket *sock; int err; if (nbd->sock) return -EBUSY; sock = sockfd_lookup(arg, &err); if (sock) { nbd->sock = sock; if (max_part > 0) bdev->bd_invalidated = 1; nbd->disconnect = 0; /* we're connected now */ return 0; } return -EINVAL; } case NBD_SET_BLKSIZE: nbd->blksize = arg; nbd->bytesize &= ~(nbd->blksize-1); bdev->bd_inode->i_size = nbd->bytesize; set_blocksize(bdev, nbd->blksize); set_capacity(nbd->disk, nbd->bytesize >> 9); return 0; case NBD_SET_SIZE: nbd->bytesize = arg & ~(nbd->blksize-1); bdev->bd_inode->i_size = nbd->bytesize; set_blocksize(bdev, nbd->blksize); set_capacity(nbd->disk, nbd->bytesize >> 9); return 0; case NBD_SET_TIMEOUT: nbd->xmit_timeout = arg * HZ; return 0; case NBD_SET_FLAGS: nbd->flags = arg; return 0; case NBD_SET_SIZE_BLOCKS: nbd->bytesize = ((u64) arg) * nbd->blksize; bdev->bd_inode->i_size = nbd->bytesize; set_blocksize(bdev, nbd->blksize); set_capacity(nbd->disk, nbd->bytesize >> 9); return 0; case NBD_DO_IT: { struct task_struct *thread; struct socket *sock; int error; if (nbd->pid) return -EBUSY; if (!nbd->sock) return -EINVAL; mutex_unlock(&nbd->tx_lock); if (nbd->flags & NBD_FLAG_READ_ONLY) set_device_ro(bdev, true); if (nbd->flags & NBD_FLAG_SEND_TRIM) queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, nbd->disk->queue); if (nbd->flags & NBD_FLAG_SEND_FLUSH) blk_queue_flush(nbd->disk->queue, REQ_FLUSH); else blk_queue_flush(nbd->disk->queue, 0); thread = kthread_run(nbd_thread, nbd, "%s", nbd->disk->disk_name); if (IS_ERR(thread)) { mutex_lock(&nbd->tx_lock); return PTR_ERR(thread); } error = nbd_do_it(nbd); kthread_stop(thread); mutex_lock(&nbd->tx_lock); if (error) return error; sock_shutdown(nbd, 0); sock = nbd->sock; nbd->sock = NULL; nbd_clear_que(nbd); dev_warn(disk_to_dev(nbd->disk), "queue cleared\n"); kill_bdev(bdev); queue_flag_clear_unlocked(QUEUE_FLAG_DISCARD, nbd->disk->queue); set_device_ro(bdev, false); if (sock) sockfd_put(sock); nbd->flags = 0; nbd->bytesize = 0; bdev->bd_inode->i_size = 0; set_capacity(nbd->disk, 0); if (max_part > 0) blkdev_reread_part(bdev); if (nbd->disconnect) /* user requested, ignore socket errors */ return 0; return nbd->harderror; } case NBD_CLEAR_QUE: /* * This is for compatibility only. The queue is always cleared * by NBD_DO_IT or NBD_CLEAR_SOCK. */ return 0; case NBD_PRINT_DEBUG: dev_info(disk_to_dev(nbd->disk), "next = %p, prev = %p, head = %p\n", nbd->queue_head.next, nbd->queue_head.prev, &nbd->queue_head); return 0; } return -ENOTTY; } static int nbd_ioctl(struct block_device *bdev, fmode_t mode, unsigned int cmd, unsigned long arg) { struct nbd_device *nbd = bdev->bd_disk->private_data; int error; if (!capable(CAP_SYS_ADMIN)) return -EPERM; BUG_ON(nbd->magic != NBD_MAGIC); mutex_lock(&nbd->tx_lock); error = __nbd_ioctl(bdev, nbd, cmd, arg); mutex_unlock(&nbd->tx_lock); return error; } static const struct block_device_operations nbd_fops = { .owner = THIS_MODULE, .ioctl = nbd_ioctl, }; /* * And here should be modules and kernel interface * (Just smiley confuses emacs :-) */ static int __init nbd_init(void) { int err = -ENOMEM; int i; int part_shift; BUILD_BUG_ON(sizeof(struct nbd_request) != 28); if (max_part < 0) { printk(KERN_ERR "nbd: max_part must be >= 0\n"); return -EINVAL; } part_shift = 0; if (max_part > 0) { part_shift = fls(max_part); /* * Adjust max_part according to part_shift as it is exported * to user space so that user can know the max number of * partition kernel should be able to manage. * * Note that -1 is required because partition 0 is reserved * for the whole disk. */ max_part = (1UL << part_shift) - 1; } if ((1UL << part_shift) > DISK_MAX_PARTS) return -EINVAL; if (nbds_max > 1UL << (MINORBITS - part_shift)) return -EINVAL; nbd_dev = kcalloc(nbds_max, sizeof(*nbd_dev), GFP_KERNEL); if (!nbd_dev) return -ENOMEM; for (i = 0; i < nbds_max; i++) { struct gendisk *disk = alloc_disk(1 << part_shift); if (!disk) goto out; nbd_dev[i].disk = disk; /* * The new linux 2.5 block layer implementation requires * every gendisk to have its very own request_queue struct. * These structs are big so we dynamically allocate them. */ disk->queue = blk_init_queue(do_nbd_request, &nbd_lock); if (!disk->queue) { put_disk(disk); goto out; } /* * Tell the block layer that we are not a rotational device */ queue_flag_set_unlocked(QUEUE_FLAG_NONROT, disk->queue); queue_flag_clear_unlocked(QUEUE_FLAG_ADD_RANDOM, disk->queue); disk->queue->limits.discard_granularity = 512; disk->queue->limits.max_discard_sectors = UINT_MAX; disk->queue->limits.discard_zeroes_data = 0; blk_queue_max_hw_sectors(disk->queue, 65536); disk->queue->limits.max_sectors = 256; } if (register_blkdev(NBD_MAJOR, "nbd")) { err = -EIO; goto out; } printk(KERN_INFO "nbd: registered device at major %d\n", NBD_MAJOR); for (i = 0; i < nbds_max; i++) { struct gendisk *disk = nbd_dev[i].disk; nbd_dev[i].magic = NBD_MAGIC; INIT_LIST_HEAD(&nbd_dev[i].waiting_queue); spin_lock_init(&nbd_dev[i].queue_lock); INIT_LIST_HEAD(&nbd_dev[i].queue_head); mutex_init(&nbd_dev[i].tx_lock); init_waitqueue_head(&nbd_dev[i].active_wq); init_waitqueue_head(&nbd_dev[i].waiting_wq); nbd_dev[i].blksize = 1024; nbd_dev[i].bytesize = 0; disk->major = NBD_MAJOR; disk->first_minor = i << part_shift; disk->fops = &nbd_fops; disk->private_data = &nbd_dev[i]; sprintf(disk->disk_name, "nbd%d", i); set_capacity(disk, 0); add_disk(disk); } return 0; out: while (i--) { blk_cleanup_queue(nbd_dev[i].disk->queue); put_disk(nbd_dev[i].disk); } kfree(nbd_dev); return err; } static void __exit nbd_cleanup(void) { int i; for (i = 0; i < nbds_max; i++) { struct gendisk *disk = nbd_dev[i].disk; nbd_dev[i].magic = 0; if (disk) { del_gendisk(disk); blk_cleanup_queue(disk->queue); put_disk(disk); } } unregister_blkdev(NBD_MAJOR, "nbd"); kfree(nbd_dev); printk(KERN_INFO "nbd: unregistered device at major %d\n", NBD_MAJOR); } module_init(nbd_init); module_exit(nbd_cleanup); MODULE_DESCRIPTION("Network Block Device"); MODULE_LICENSE("GPL"); module_param(nbds_max, int, 0444); MODULE_PARM_DESC(nbds_max, "number of network block devices to initialize (default: 16)"); module_param(max_part, int, 0444); MODULE_PARM_DESC(max_part, "number of partitions per device (default: 0)");