block: fold cmd_type into the REQ_OP_ space

[mirror_ubuntu-bionic-kernel.git] / drivers / block / nbd.c

/*
 * 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 <linux/debugfs.h>
#include <linux/blk-mq.h>

#include <linux/uaccess.h>
#include <asm/types.h>

#include <linux/nbd.h>

struct nbd_sock {
        struct socket *sock;
        struct mutex tx_lock;
};

#define NBD_TIMEDOUT                    0
#define NBD_DISCONNECT_REQUESTED        1
#define NBD_DISCONNECTED                2
#define NBD_RUNNING                     3

struct nbd_device {
        u32 flags;
        unsigned long runtime_flags;
        struct nbd_sock **socks;
        int magic;

        struct blk_mq_tag_set tag_set;

        struct mutex config_lock;
        struct gendisk *disk;
        int num_connections;
        atomic_t recv_threads;
        wait_queue_head_t recv_wq;
        loff_t blksize;
        loff_t bytesize;

        struct task_struct *task_recv;
        struct task_struct *task_setup;

#if IS_ENABLED(CONFIG_DEBUG_FS)
        struct dentry *dbg_dir;
#endif
};

struct nbd_cmd {
        struct nbd_device *nbd;
        struct completion send_complete;
};

#if IS_ENABLED(CONFIG_DEBUG_FS)
static struct dentry *nbd_dbg_dir;
#endif

#define nbd_name(nbd) ((nbd)->disk->disk_name)

#define NBD_MAGIC 0x68797548

static unsigned int nbds_max = 16;
static struct nbd_device *nbd_dev;
static int max_part;

static inline struct device *nbd_to_dev(struct nbd_device *nbd)
{
        return disk_to_dev(nbd->disk);
}

static bool nbd_is_connected(struct nbd_device *nbd)
{
        return !!nbd->task_recv;
}

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 int nbd_size_clear(struct nbd_device *nbd, struct block_device *bdev)
{
        bdev->bd_inode->i_size = 0;
        set_capacity(nbd->disk, 0);
        kobject_uevent(&nbd_to_dev(nbd)->kobj, KOBJ_CHANGE);

        return 0;
}

static void nbd_size_update(struct nbd_device *nbd, struct block_device *bdev)
{
        if (!nbd_is_connected(nbd))
                return;

        bdev->bd_inode->i_size = nbd->bytesize;
        set_capacity(nbd->disk, nbd->bytesize >> 9);
        kobject_uevent(&nbd_to_dev(nbd)->kobj, KOBJ_CHANGE);
}

static int nbd_size_set(struct nbd_device *nbd, struct block_device *bdev,
                        loff_t blocksize, loff_t nr_blocks)
{
        int ret;

        ret = set_blocksize(bdev, blocksize);
        if (ret)
                return ret;

        nbd->blksize = blocksize;
        nbd->bytesize = blocksize * nr_blocks;

        nbd_size_update(nbd, bdev);

        return 0;
}

static void nbd_end_request(struct nbd_cmd *cmd)
{
        struct nbd_device *nbd = cmd->nbd;
        struct request *req = blk_mq_rq_from_pdu(cmd);
        int error = req->errors ? -EIO : 0;

        dev_dbg(nbd_to_dev(nbd), "request %p: %s\n", cmd,
                error ? "failed" : "done");

        blk_mq_complete_request(req, error);
}

/*
 * Forcibly shutdown the socket causing all listeners to error
 */
static void sock_shutdown(struct nbd_device *nbd)
{
        int i;

        if (nbd->num_connections == 0)
                return;
        if (test_and_set_bit(NBD_DISCONNECTED, &nbd->runtime_flags))
                return;

        for (i = 0; i < nbd->num_connections; i++) {
                struct nbd_sock *nsock = nbd->socks[i];
                mutex_lock(&nsock->tx_lock);
                kernel_sock_shutdown(nsock->sock, SHUT_RDWR);
                mutex_unlock(&nsock->tx_lock);
        }
        dev_warn(disk_to_dev(nbd->disk), "shutting down sockets\n");
}

static enum blk_eh_timer_return nbd_xmit_timeout(struct request *req,
                                                 bool reserved)
{
        struct nbd_cmd *cmd = blk_mq_rq_to_pdu(req);
        struct nbd_device *nbd = cmd->nbd;

        dev_err(nbd_to_dev(nbd), "Connection timed out, shutting down connection\n");
        set_bit(NBD_TIMEDOUT, &nbd->runtime_flags);
        req->errors++;

        mutex_lock(&nbd->config_lock);
        sock_shutdown(nbd);
        mutex_unlock(&nbd->config_lock);
        return BLK_EH_HANDLED;
}

/*
 *  Send or receive packet.
 */
static int sock_xmit(struct nbd_device *nbd, int index, int send, void *buf,
                     int size, int msg_flags)
{
        struct socket *sock = nbd->socks[index]->sock;
        int result;
        struct msghdr msg;
        struct kvec iov;
        unsigned long pflags = current->flags;

        if (unlikely(!sock)) {
                dev_err_ratelimited(disk_to_dev(nbd->disk),
                        "Attempted %s on closed socket in sock_xmit\n",
                        (send ? "send" : "recv"));
                return -EINVAL;
        }

        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)
                        result = kernel_sendmsg(sock, &msg, &iov, 1, size);
                else
                        result = kernel_recvmsg(sock, &msg, &iov, 1, size,
                                                msg.msg_flags);

                if (result <= 0) {
                        if (result == 0)
                                result = -EPIPE; /* short read */
                        break;
                }
                size -= result;
                buf += result;
        } while (size > 0);

        tsk_restore_flags(current, pflags, PF_MEMALLOC);

        return result;
}

static inline int sock_send_bvec(struct nbd_device *nbd, int index,
                                 struct bio_vec *bvec, int flags)
{
        int result;
        void *kaddr = kmap(bvec->bv_page);
        result = sock_xmit(nbd, index, 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_cmd(struct nbd_device *nbd, struct nbd_cmd *cmd, int index)
{
        struct request *req = blk_mq_rq_from_pdu(cmd);
        int result;
        struct nbd_request request;
        unsigned long size = blk_rq_bytes(req);
        struct bio *bio;
        u32 type;
        u32 tag = blk_mq_unique_tag(req);

        switch (req_op(req)) {
        case REQ_OP_DISCARD:
                type = NBD_CMD_TRIM;
                break;
        case REQ_OP_FLUSH:
                type = NBD_CMD_FLUSH;
                break;
        case REQ_OP_WRITE:
                type = NBD_CMD_WRITE;
                break;
        case REQ_OP_READ:
                type = NBD_CMD_READ;
                break;
        default:
                return -EIO;
        }

        if (rq_data_dir(req) == WRITE &&
            (nbd->flags & NBD_FLAG_READ_ONLY)) {
                dev_err_ratelimited(disk_to_dev(nbd->disk),
                                    "Write on read-only\n");
                return -EIO;
        }

        memset(&request, 0, sizeof(request));
        request.magic = htonl(NBD_REQUEST_MAGIC);
        request.type = htonl(type);
        if (type != NBD_CMD_FLUSH) {
                request.from = cpu_to_be64((u64)blk_rq_pos(req) << 9);
                request.len = htonl(size);
        }
        memcpy(request.handle, &tag, sizeof(tag));

        dev_dbg(nbd_to_dev(nbd), "request %p: sending control (%s@%llu,%uB)\n",
                cmd, nbdcmd_to_ascii(type),
                (unsigned long long)blk_rq_pos(req) << 9, blk_rq_bytes(req));
        result = sock_xmit(nbd, index, 1, &request, sizeof(request),
                        (type == NBD_CMD_WRITE) ? MSG_MORE : 0);
        if (result <= 0) {
                dev_err_ratelimited(disk_to_dev(nbd->disk),
                        "Send control failed (result %d)\n", result);
                return -EIO;
        }

        if (type != NBD_CMD_WRITE)
                return 0;

        bio = req->bio;
        while (bio) {
                struct bio *next = bio->bi_next;
                struct bvec_iter iter;
                struct bio_vec bvec;

                bio_for_each_segment(bvec, bio, iter) {
                        bool is_last = !next && bio_iter_last(bvec, iter);
                        int flags = is_last ? 0 : MSG_MORE;

                        dev_dbg(nbd_to_dev(nbd), "request %p: sending %d bytes data\n",
                                cmd, bvec.bv_len);
                        result = sock_send_bvec(nbd, index, &bvec, flags);
                        if (result <= 0) {
                                dev_err(disk_to_dev(nbd->disk),
                                        "Send data failed (result %d)\n",
                                        result);
                                return -EIO;
                        }
                        /*
                         * The completion might already have come in,
                         * so break for the last one instead of letting
                         * the iterator do it. This prevents use-after-free
                         * of the bio.
                         */
                        if (is_last)
                                break;
                }
                bio = next;
        }
        return 0;
}

static inline int sock_recv_bvec(struct nbd_device *nbd, int index,
                                 struct bio_vec *bvec)
{
        int result;
        void *kaddr = kmap(bvec->bv_page);
        result = sock_xmit(nbd, index, 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 nbd_cmd *nbd_read_stat(struct nbd_device *nbd, int index)
{
        int result;
        struct nbd_reply reply;
        struct nbd_cmd *cmd;
        struct request *req = NULL;
        u16 hwq;
        u32 tag;

        reply.magic = 0;
        result = sock_xmit(nbd, index, 0, &reply, sizeof(reply), MSG_WAITALL);
        if (result <= 0) {
                if (!test_bit(NBD_DISCONNECTED, &nbd->runtime_flags) &&
                    !test_bit(NBD_DISCONNECT_REQUESTED, &nbd->runtime_flags))
                        dev_err(disk_to_dev(nbd->disk),
                                "Receive control failed (result %d)\n", result);
                return ERR_PTR(result);
        }

        if (ntohl(reply.magic) != NBD_REPLY_MAGIC) {
                dev_err(disk_to_dev(nbd->disk), "Wrong magic (0x%lx)\n",
                                (unsigned long)ntohl(reply.magic));
                return ERR_PTR(-EPROTO);
        }

        memcpy(&tag, reply.handle, sizeof(u32));

        hwq = blk_mq_unique_tag_to_hwq(tag);
        if (hwq < nbd->tag_set.nr_hw_queues)
                req = blk_mq_tag_to_rq(nbd->tag_set.tags[hwq],
                                       blk_mq_unique_tag_to_tag(tag));
        if (!req || !blk_mq_request_started(req)) {
                dev_err(disk_to_dev(nbd->disk), "Unexpected reply (%d) %p\n",
                        tag, req);
                return ERR_PTR(-ENOENT);
        }
        cmd = blk_mq_rq_to_pdu(req);
        if (ntohl(reply.error)) {
                dev_err(disk_to_dev(nbd->disk), "Other side returned error (%d)\n",
                        ntohl(reply.error));
                req->errors++;
                return cmd;
        }

        dev_dbg(nbd_to_dev(nbd), "request %p: got reply\n", cmd);
        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, index, &bvec);
                        if (result <= 0) {
                                dev_err(disk_to_dev(nbd->disk), "Receive data failed (result %d)\n",
                                        result);
                                req->errors++;
                                return cmd;
                        }
                        dev_dbg(nbd_to_dev(nbd), "request %p: got %d bytes data\n",
                                cmd, bvec.bv_len);
                }
        } else {
                /* See the comment in nbd_queue_rq. */
                wait_for_completion(&cmd->send_complete);
        }
        return cmd;
}

static ssize_t pid_show(struct device *dev,
                        struct device_attribute *attr, char *buf)
{
        struct gendisk *disk = dev_to_disk(dev);
        struct nbd_device *nbd = (struct nbd_device *)disk->private_data;

        return sprintf(buf, "%d\n", task_pid_nr(nbd->task_recv));
}

static struct device_attribute pid_attr = {
        .attr = { .name = "pid", .mode = S_IRUGO},
        .show = pid_show,
};

struct recv_thread_args {
        struct work_struct work;
        struct nbd_device *nbd;
        int index;
};

static void recv_work(struct work_struct *work)
{
        struct recv_thread_args *args = container_of(work,
                                                     struct recv_thread_args,
                                                     work);
        struct nbd_device *nbd = args->nbd;
        struct nbd_cmd *cmd;
        int ret = 0;

        BUG_ON(nbd->magic != NBD_MAGIC);
        while (1) {
                cmd = nbd_read_stat(nbd, args->index);
                if (IS_ERR(cmd)) {
                        ret = PTR_ERR(cmd);
                        break;
                }

                nbd_end_request(cmd);
        }

        /*
         * We got an error, shut everybody down if this wasn't the result of a
         * disconnect request.
         */
        if (ret && !test_bit(NBD_DISCONNECT_REQUESTED, &nbd->runtime_flags))
                sock_shutdown(nbd);
        atomic_dec(&nbd->recv_threads);
        wake_up(&nbd->recv_wq);
}

static void nbd_clear_req(struct request *req, void *data, bool reserved)
{
        struct nbd_cmd *cmd;

        if (!blk_mq_request_started(req))
                return;
        cmd = blk_mq_rq_to_pdu(req);
        req->errors++;
        nbd_end_request(cmd);
}

static void nbd_clear_que(struct nbd_device *nbd)
{
        BUG_ON(nbd->magic != NBD_MAGIC);

        blk_mq_tagset_busy_iter(&nbd->tag_set, nbd_clear_req, NULL);
        dev_dbg(disk_to_dev(nbd->disk), "queue cleared\n");
}


static void nbd_handle_cmd(struct nbd_cmd *cmd, int index)
{
        struct request *req = blk_mq_rq_from_pdu(cmd);
        struct nbd_device *nbd = cmd->nbd;
        struct nbd_sock *nsock;

        if (index >= nbd->num_connections) {
                dev_err_ratelimited(disk_to_dev(nbd->disk),
                                    "Attempted send on invalid socket\n");
                goto error_out;
        }

        if (test_bit(NBD_DISCONNECTED, &nbd->runtime_flags)) {
                dev_err_ratelimited(disk_to_dev(nbd->disk),
                                    "Attempted send on closed socket\n");
                goto error_out;
        }

        req->errors = 0;

        nsock = nbd->socks[index];
        mutex_lock(&nsock->tx_lock);
        if (unlikely(!nsock->sock)) {
                mutex_unlock(&nsock->tx_lock);
                dev_err_ratelimited(disk_to_dev(nbd->disk),
                                    "Attempted send on closed socket\n");
                goto error_out;
        }

        if (nbd_send_cmd(nbd, cmd, index) != 0) {
                dev_err_ratelimited(disk_to_dev(nbd->disk),
                                    "Request send failed\n");
                req->errors++;
                nbd_end_request(cmd);
        }

        mutex_unlock(&nsock->tx_lock);

        return;

error_out:
        req->errors++;
        nbd_end_request(cmd);
}

static int nbd_queue_rq(struct blk_mq_hw_ctx *hctx,
                        const struct blk_mq_queue_data *bd)
{
        struct nbd_cmd *cmd = blk_mq_rq_to_pdu(bd->rq);

        /*
         * Since we look at the bio's to send the request over the network we
         * need to make sure the completion work doesn't mark this request done
         * before we are done doing our send.  This keeps us from dereferencing
         * freed data if we have particularly fast completions (ie we get the
         * completion before we exit sock_xmit on the last bvec) or in the case
         * that the server is misbehaving (or there was an error) before we're
         * done sending everything over the wire.
         */
        init_completion(&cmd->send_complete);
        blk_mq_start_request(bd->rq);
        nbd_handle_cmd(cmd, hctx->queue_num);
        complete(&cmd->send_complete);

        return BLK_MQ_RQ_QUEUE_OK;
}

static int nbd_add_socket(struct nbd_device *nbd, struct socket *sock)
{
        struct nbd_sock **socks;
        struct nbd_sock *nsock;

        if (!nbd->task_setup)
                nbd->task_setup = current;
        if (nbd->task_setup != current) {
                dev_err(disk_to_dev(nbd->disk),
                        "Device being setup by another task");
                return -EINVAL;
        }

        socks = krealloc(nbd->socks, (nbd->num_connections + 1) *
                         sizeof(struct nbd_sock *), GFP_KERNEL);
        if (!socks)
                return -ENOMEM;
        nsock = kzalloc(sizeof(struct nbd_sock), GFP_KERNEL);
        if (!nsock)
                return -ENOMEM;

        nbd->socks = socks;

        mutex_init(&nsock->tx_lock);
        nsock->sock = sock;
        socks[nbd->num_connections++] = nsock;

        return 0;
}

/* Reset all properties of an NBD device */
static void nbd_reset(struct nbd_device *nbd)
{
        int i;

        for (i = 0; i < nbd->num_connections; i++)
                kfree(nbd->socks[i]);
        kfree(nbd->socks);
        nbd->socks = NULL;
        nbd->runtime_flags = 0;
        nbd->blksize = 1024;
        nbd->bytesize = 0;
        set_capacity(nbd->disk, 0);
        nbd->flags = 0;
        nbd->tag_set.timeout = 0;
        nbd->num_connections = 0;
        nbd->task_setup = NULL;
        queue_flag_clear_unlocked(QUEUE_FLAG_DISCARD, nbd->disk->queue);
}

static void nbd_bdev_reset(struct block_device *bdev)
{
        set_device_ro(bdev, false);
        bdev->bd_inode->i_size = 0;
        if (max_part > 0) {
                blkdev_reread_part(bdev);
                bdev->bd_invalidated = 1;
        }
}

static void nbd_parse_flags(struct nbd_device *nbd, struct block_device *bdev)
{
        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_write_cache(nbd->disk->queue, true, false);
        else
                blk_queue_write_cache(nbd->disk->queue, false, false);
}

static void send_disconnects(struct nbd_device *nbd)
{
        struct nbd_request request = {};
        int i, ret;

        request.magic = htonl(NBD_REQUEST_MAGIC);
        request.type = htonl(NBD_CMD_DISC);

        for (i = 0; i < nbd->num_connections; i++) {
                ret = sock_xmit(nbd, i, 1, &request, sizeof(request), 0);
                if (ret <= 0)
                        dev_err(disk_to_dev(nbd->disk),
                                "Send disconnect failed %d\n", ret);
        }
}

static int nbd_dev_dbg_init(struct nbd_device *nbd);
static void nbd_dev_dbg_close(struct nbd_device *nbd);

/* Must be called with config_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: {
                dev_info(disk_to_dev(nbd->disk), "NBD_DISCONNECT\n");
                if (!nbd->socks)
                        return -EINVAL;

                mutex_unlock(&nbd->config_lock);
                fsync_bdev(bdev);
                mutex_lock(&nbd->config_lock);

                /* Check again after getting mutex back.  */
                if (!nbd->socks)
                        return -EINVAL;

                if (!test_and_set_bit(NBD_DISCONNECT_REQUESTED,
                                      &nbd->runtime_flags))
                        send_disconnects(nbd);
                return 0;
        }

        case NBD_CLEAR_SOCK:
                sock_shutdown(nbd);
                nbd_clear_que(nbd);
                kill_bdev(bdev);
                nbd_bdev_reset(bdev);
                /*
                 * We want to give the run thread a chance to wait for everybody
                 * to clean up and then do it's own cleanup.
                 */
                if (!test_bit(NBD_RUNNING, &nbd->runtime_flags)) {
                        int i;

                        for (i = 0; i < nbd->num_connections; i++)
                                kfree(nbd->socks[i]);
                        kfree(nbd->socks);
                        nbd->socks = NULL;
                        nbd->num_connections = 0;
                        nbd->task_setup = NULL;
                }
                return 0;

        case NBD_SET_SOCK: {
                int err;
                struct socket *sock = sockfd_lookup(arg, &err);

                if (!sock)
                        return err;

                err = nbd_add_socket(nbd, sock);
                if (!err && max_part)
                        bdev->bd_invalidated = 1;

                return err;
        }

        case NBD_SET_BLKSIZE: {
                loff_t bsize = div_s64(nbd->bytesize, arg);

                return nbd_size_set(nbd, bdev, arg, bsize);
        }

        case NBD_SET_SIZE:
                return nbd_size_set(nbd, bdev, nbd->blksize,
                                        div_s64(arg, nbd->blksize));

        case NBD_SET_SIZE_BLOCKS:
                return nbd_size_set(nbd, bdev, nbd->blksize, arg);

        case NBD_SET_TIMEOUT:
                nbd->tag_set.timeout = arg * HZ;
                return 0;

        case NBD_SET_FLAGS:
                nbd->flags = arg;
                return 0;

        case NBD_DO_IT: {
                struct recv_thread_args *args;
                int num_connections = nbd->num_connections;
                int error = 0, i;

                if (nbd->task_recv)
                        return -EBUSY;
                if (!nbd->socks)
                        return -EINVAL;
                if (num_connections > 1 &&
                    !(nbd->flags & NBD_FLAG_CAN_MULTI_CONN)) {
                        dev_err(disk_to_dev(nbd->disk), "server does not support multiple connections per device.\n");
                        error = -EINVAL;
                        goto out_err;
                }

                set_bit(NBD_RUNNING, &nbd->runtime_flags);
                blk_mq_update_nr_hw_queues(&nbd->tag_set, nbd->num_connections);
                args = kcalloc(num_connections, sizeof(*args), GFP_KERNEL);
                if (!args) {
                        error = -ENOMEM;
                        goto out_err;
                }
                nbd->task_recv = current;
                mutex_unlock(&nbd->config_lock);

                nbd_parse_flags(nbd, bdev);

                error = device_create_file(disk_to_dev(nbd->disk), &pid_attr);
                if (error) {
                        dev_err(disk_to_dev(nbd->disk), "device_create_file failed!\n");
                        goto out_recv;
                }

                nbd_size_update(nbd, bdev);

                nbd_dev_dbg_init(nbd);
                for (i = 0; i < num_connections; i++) {
                        sk_set_memalloc(nbd->socks[i]->sock->sk);
                        atomic_inc(&nbd->recv_threads);
                        INIT_WORK(&args[i].work, recv_work);
                        args[i].nbd = nbd;
                        args[i].index = i;
                        queue_work(system_long_wq, &args[i].work);
                }
                wait_event_interruptible(nbd->recv_wq,
                                         atomic_read(&nbd->recv_threads) == 0);
                for (i = 0; i < num_connections; i++)
                        flush_work(&args[i].work);
                nbd_dev_dbg_close(nbd);
                nbd_size_clear(nbd, bdev);
                device_remove_file(disk_to_dev(nbd->disk), &pid_attr);
out_recv:
                mutex_lock(&nbd->config_lock);
                nbd->task_recv = NULL;
out_err:
                sock_shutdown(nbd);
                nbd_clear_que(nbd);
                kill_bdev(bdev);
                nbd_bdev_reset(bdev);

                /* user requested, ignore socket errors */
                if (test_bit(NBD_DISCONNECT_REQUESTED, &nbd->runtime_flags))
                        error = 0;
                if (test_bit(NBD_TIMEDOUT, &nbd->runtime_flags))
                        error = -ETIMEDOUT;

                nbd_reset(nbd);
                return error;
        }

        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:
                /*
                 * For compatibility only, we no longer keep a list of
                 * outstanding requests.
                 */
                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->config_lock);
        error = __nbd_ioctl(bdev, nbd, cmd, arg);
        mutex_unlock(&nbd->config_lock);

        return error;
}

static const struct block_device_operations nbd_fops =
{
        .owner =        THIS_MODULE,
        .ioctl =        nbd_ioctl,
        .compat_ioctl = nbd_ioctl,
};

#if IS_ENABLED(CONFIG_DEBUG_FS)

static int nbd_dbg_tasks_show(struct seq_file *s, void *unused)
{
        struct nbd_device *nbd = s->private;

        if (nbd->task_recv)
                seq_printf(s, "recv: %d\n", task_pid_nr(nbd->task_recv));

        return 0;
}

static int nbd_dbg_tasks_open(struct inode *inode, struct file *file)
{
        return single_open(file, nbd_dbg_tasks_show, inode->i_private);
}

static const struct file_operations nbd_dbg_tasks_ops = {
        .open = nbd_dbg_tasks_open,
        .read = seq_read,
        .llseek = seq_lseek,
        .release = single_release,
};

static int nbd_dbg_flags_show(struct seq_file *s, void *unused)
{
        struct nbd_device *nbd = s->private;
        u32 flags = nbd->flags;

        seq_printf(s, "Hex: 0x%08x\n\n", flags);

        seq_puts(s, "Known flags:\n");

        if (flags & NBD_FLAG_HAS_FLAGS)
                seq_puts(s, "NBD_FLAG_HAS_FLAGS\n");
        if (flags & NBD_FLAG_READ_ONLY)
                seq_puts(s, "NBD_FLAG_READ_ONLY\n");
        if (flags & NBD_FLAG_SEND_FLUSH)
                seq_puts(s, "NBD_FLAG_SEND_FLUSH\n");
        if (flags & NBD_FLAG_SEND_TRIM)
                seq_puts(s, "NBD_FLAG_SEND_TRIM\n");

        return 0;
}

static int nbd_dbg_flags_open(struct inode *inode, struct file *file)
{
        return single_open(file, nbd_dbg_flags_show, inode->i_private);
}

static const struct file_operations nbd_dbg_flags_ops = {
        .open = nbd_dbg_flags_open,
        .read = seq_read,
        .llseek = seq_lseek,
        .release = single_release,
};

static int nbd_dev_dbg_init(struct nbd_device *nbd)
{
        struct dentry *dir;

        if (!nbd_dbg_dir)
                return -EIO;

        dir = debugfs_create_dir(nbd_name(nbd), nbd_dbg_dir);
        if (!dir) {
                dev_err(nbd_to_dev(nbd), "Failed to create debugfs dir for '%s'\n",
                        nbd_name(nbd));
                return -EIO;
        }
        nbd->dbg_dir = dir;

        debugfs_create_file("tasks", 0444, dir, nbd, &nbd_dbg_tasks_ops);
        debugfs_create_u64("size_bytes", 0444, dir, &nbd->bytesize);
        debugfs_create_u32("timeout", 0444, dir, &nbd->tag_set.timeout);
        debugfs_create_u64("blocksize", 0444, dir, &nbd->blksize);
        debugfs_create_file("flags", 0444, dir, nbd, &nbd_dbg_flags_ops);

        return 0;
}

static void nbd_dev_dbg_close(struct nbd_device *nbd)
{
        debugfs_remove_recursive(nbd->dbg_dir);
}

static int nbd_dbg_init(void)
{
        struct dentry *dbg_dir;

        dbg_dir = debugfs_create_dir("nbd", NULL);
        if (!dbg_dir)
                return -EIO;

        nbd_dbg_dir = dbg_dir;

        return 0;
}

static void nbd_dbg_close(void)
{
        debugfs_remove_recursive(nbd_dbg_dir);
}

#else  /* IS_ENABLED(CONFIG_DEBUG_FS) */

static int nbd_dev_dbg_init(struct nbd_device *nbd)
{
        return 0;
}

static void nbd_dev_dbg_close(struct nbd_device *nbd)
{
}

static int nbd_dbg_init(void)
{
        return 0;
}

static void nbd_dbg_close(void)
{
}

#endif

static int nbd_init_request(void *data, struct request *rq,
                            unsigned int hctx_idx, unsigned int request_idx,
                            unsigned int numa_node)
{
        struct nbd_cmd *cmd = blk_mq_rq_to_pdu(rq);
        cmd->nbd = data;
        return 0;
}

static struct blk_mq_ops nbd_mq_ops = {
        .queue_rq       = nbd_queue_rq,
        .init_request   = nbd_init_request,
        .timeout        = nbd_xmit_timeout,
};

/*
 * 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 request_queue *q;
                struct gendisk *disk = alloc_disk(1 << part_shift);
                if (!disk)
                        goto out;
                nbd_dev[i].disk = disk;

                nbd_dev[i].tag_set.ops = &nbd_mq_ops;
                nbd_dev[i].tag_set.nr_hw_queues = 1;
                nbd_dev[i].tag_set.queue_depth = 128;
                nbd_dev[i].tag_set.numa_node = NUMA_NO_NODE;
                nbd_dev[i].tag_set.cmd_size = sizeof(struct nbd_cmd);
                nbd_dev[i].tag_set.flags = BLK_MQ_F_SHOULD_MERGE |
                        BLK_MQ_F_SG_MERGE | BLK_MQ_F_BLOCKING;
                nbd_dev[i].tag_set.driver_data = &nbd_dev[i];

                err = blk_mq_alloc_tag_set(&nbd_dev[i].tag_set);
                if (err) {
                        put_disk(disk);
                        goto out;
                }

                /*
                 * 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.
                 */
                q = blk_mq_init_queue(&nbd_dev[i].tag_set);
                if (IS_ERR(q)) {
                        blk_mq_free_tag_set(&nbd_dev[i].tag_set);
                        put_disk(disk);
                        goto out;
                }
                disk->queue = q;

                /*
                 * 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;
                blk_queue_max_discard_sectors(disk->queue, 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);

        nbd_dbg_init();

        for (i = 0; i < nbds_max; i++) {
                struct gendisk *disk = nbd_dev[i].disk;
                nbd_dev[i].magic = NBD_MAGIC;
                mutex_init(&nbd_dev[i].config_lock);
                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);
                init_waitqueue_head(&nbd_dev[i].recv_wq);
                nbd_reset(&nbd_dev[i]);
                add_disk(disk);
        }

        return 0;
out:
        while (i--) {
                blk_mq_free_tag_set(&nbd_dev[i].tag_set);
                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;

        nbd_dbg_close();

        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);
                        blk_mq_free_tag_set(&nbd_dev[i].tag_set);
                        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)");