trans_fd.c

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/*
 * linux/fs/9p/trans_fd.c
 *
 * Fd transport layer.  Includes deprecated socket layer.
 *
 *  Copyright (C) 2006 by Russ Cox <[email protected]>
 *  Copyright (C) 2004-2005 by Latchesar Ionkov <[email protected]>
 *  Copyright (C) 2004-2008 by Eric Van Hensbergen <[email protected]>
 *  Copyright (C) 1997-2002 by Ron Minnich <[email protected]>
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License version 2
 *  as published by the Free Software Foundation.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to:
 *  Free Software Foundation
 *  51 Franklin Street, Fifth Floor
 *  Boston, MA  02111-1301  USA
 *
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/in.h>
#include <linux/module.h>
#include <linux/net.h>
#include <linux/ipv6.h>
#include <linux/kthread.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/un.h>
#include <linux/uaccess.h>
#include <linux/inet.h>
#include <linux/idr.h>
#include <linux/file.h>
#include <linux/parser.h>
#include <linux/slab.h>
#include <net/9p/9p.h>
#include <net/9p/client.h>
#include <net/9p/transport.h>

#include <linux/syscalls.h> /* killme */

#define P9_PORT 564
#define MAX_SOCK_BUF (64*1024)
#define MAXPOLLWADDR    2

struct p9_fd_opts {
    int rfd;
    int wfd;
    u16 port;
};

struct p9_trans_fd {
    struct file *rd;
    struct file *wr;
    struct p9_conn *conn;
};

/*
  * Option Parsing (code inspired by NFS code)
  *  - a little lazy - parse all fd-transport options
  */

enum {
    /* Options that take integer arguments */
    Opt_port, Opt_rfdno, Opt_wfdno, Opt_err,
};

static const match_table_t tokens = {
    {Opt_port, "port=%u"},
    {Opt_rfdno, "rfdno=%u"},
    {Opt_wfdno, "wfdno=%u"},
    {Opt_err, NULL},
};

enum {
    Rworksched = 1,     /* read work scheduled or running */
    Rpending = 2,       /* can read */
    Wworksched = 4,     /* write work scheduled or running */
    Wpending = 8,       /* can write */
};

struct p9_poll_wait {
    struct p9_conn *conn;
    wait_queue_t wait;
    wait_queue_head_t *wait_addr;
};

struct p9_conn {
    struct list_head mux_list;
    struct p9_client *client;
    int err;
    struct list_head req_list;
    struct list_head unsent_req_list;
    struct p9_req_t *req;
    char tmp_buf[7];
    int rsize;
    int rpos;
    char *rbuf;
    int wpos;
    int wsize;
    char *wbuf;
    struct list_head poll_pending_link;
    struct p9_poll_wait poll_wait[MAXPOLLWADDR];
    poll_table pt;
    struct work_struct rq;
    struct work_struct wq;
    unsigned long wsched;
};

static void p9_poll_workfn(struct work_struct *work);

static DEFINE_SPINLOCK(p9_poll_lock);
static LIST_HEAD(p9_poll_pending_list);
static DECLARE_WORK(p9_poll_work, p9_poll_workfn);

static void p9_mux_poll_stop(struct p9_conn *m)
{
    unsigned long flags;
    int i;

    for (i = 0; i < ARRAY_SIZE(m->poll_wait); i++) {
        struct p9_poll_wait *pwait = &m->poll_wait[i];

        if (pwait->wait_addr) {
            remove_wait_queue(pwait->wait_addr, &pwait->wait);
            pwait->wait_addr = NULL;
        }
    }

    spin_lock_irqsave(&p9_poll_lock, flags);
    list_del_init(&m->poll_pending_link);
    spin_unlock_irqrestore(&p9_poll_lock, flags);
}

static void p9_conn_cancel(struct p9_conn *m, int err)
{
    struct p9_req_t *req, *rtmp;
    unsigned long flags;
    LIST_HEAD(cancel_list);

    p9_debug(P9_DEBUG_ERROR, "mux %p err %d\n", m, err);

    spin_lock_irqsave(&m->client->lock, flags);

    if (m->err) {
        spin_unlock_irqrestore(&m->client->lock, flags);
        return;
    }

    m->err = err;

    list_for_each_entry_safe(req, rtmp, &m->req_list, req_list) {
        req->status = REQ_STATUS_ERROR;
        if (!req->t_err)
            req->t_err = err;
        list_move(&req->req_list, &cancel_list);
    }
    list_for_each_entry_safe(req, rtmp, &m->unsent_req_list, req_list) {
        req->status = REQ_STATUS_ERROR;
        if (!req->t_err)
            req->t_err = err;
        list_move(&req->req_list, &cancel_list);
    }
    spin_unlock_irqrestore(&m->client->lock, flags);

    list_for_each_entry_safe(req, rtmp, &cancel_list, req_list) {
        p9_debug(P9_DEBUG_ERROR, "call back req %p\n", req);
        list_del(&req->req_list);
        p9_client_cb(m->client, req);
    }
}

static int
p9_fd_poll(struct p9_client *client, struct poll_table_struct *pt)
{
    int ret, n;
    struct p9_trans_fd *ts = NULL;

    if (client && client->status == Connected)
        ts = client->trans;

    if (!ts)
        return -EREMOTEIO;

    if (!ts->rd->f_op || !ts->rd->f_op->poll)
        return -EIO;

    if (!ts->wr->f_op || !ts->wr->f_op->poll)
        return -EIO;

    ret = ts->rd->f_op->poll(ts->rd, pt);
    if (ret < 0)
        return ret;

    if (ts->rd != ts->wr) {
        n = ts->wr->f_op->poll(ts->wr, pt);
        if (n < 0)
            return n;
        ret = (ret & ~POLLOUT) | (n & ~POLLIN);
    }

    return ret;
}

static int p9_fd_read(struct p9_client *client, void *v, int len)
{
    int ret;
    struct p9_trans_fd *ts = NULL;

    if (client && client->status != Disconnected)
        ts = client->trans;

    if (!ts)
        return -EREMOTEIO;

    if (!(ts->rd->f_flags & O_NONBLOCK))
        p9_debug(P9_DEBUG_ERROR, "blocking read ...\n");

    ret = kernel_read(ts->rd, ts->rd->f_pos, v, len);
    if (ret <= 0 && ret != -ERESTARTSYS && ret != -EAGAIN)
        client->status = Disconnected;
    return ret;
}

static void p9_read_work(struct work_struct *work)
{
    int n, err;
    struct p9_conn *m;

    m = container_of(work, struct p9_conn, rq);

    if (m->err < 0)
        return;

    p9_debug(P9_DEBUG_TRANS, "start mux %p pos %d\n", m, m->rpos);

    if (!m->rbuf) {
        m->rbuf = m->tmp_buf;
        m->rpos = 0;
        m->rsize = 7; /* start by reading header */
    }

    clear_bit(Rpending, &m->wsched);
    p9_debug(P9_DEBUG_TRANS, "read mux %p pos %d size: %d = %d\n",
         m, m->rpos, m->rsize, m->rsize-m->rpos);
    err = p9_fd_read(m->client, m->rbuf + m->rpos,
                        m->rsize - m->rpos);
    p9_debug(P9_DEBUG_TRANS, "mux %p got %d bytes\n", m, err);
    if (err == -EAGAIN) {
        goto end_clear;
    }

    if (err <= 0)
        goto error;

    m->rpos += err;

    if ((!m->req) && (m->rpos == m->rsize)) { /* header read in */
        u16 tag;
        p9_debug(P9_DEBUG_TRANS, "got new header\n");

        n = le32_to_cpu(*(__le32 *) m->rbuf); /* read packet size */
        if (n >= m->client->msize) {
            p9_debug(P9_DEBUG_ERROR,
                 "requested packet size too big: %d\n", n);
            err = -EIO;
            goto error;
        }

        tag = le16_to_cpu(*(__le16 *) (m->rbuf+5)); /* read tag */
        p9_debug(P9_DEBUG_TRANS,
             "mux %p pkt: size: %d bytes tag: %d\n", m, n, tag);

        m->req = p9_tag_lookup(m->client, tag);
        if (!m->req || (m->req->status != REQ_STATUS_SENT &&
                    m->req->status != REQ_STATUS_FLSH)) {
            p9_debug(P9_DEBUG_ERROR, "Unexpected packet tag %d\n",
                 tag);
            err = -EIO;
            goto error;
        }

        if (m->req->rc == NULL) {
            m->req->rc = kmalloc(sizeof(struct p9_fcall) +
                        m->client->msize, GFP_NOFS);
            if (!m->req->rc) {
                m->req = NULL;
                err = -ENOMEM;
                goto error;
            }
        }
        m->rbuf = (char *)m->req->rc + sizeof(struct p9_fcall);
        memcpy(m->rbuf, m->tmp_buf, m->rsize);
        m->rsize = n;
    }

    /* not an else because some packets (like clunk) have no payload */
    if ((m->req) && (m->rpos == m->rsize)) { /* packet is read in */
        p9_debug(P9_DEBUG_TRANS, "got new packet\n");
        spin_lock(&m->client->lock);
        if (m->req->status != REQ_STATUS_ERROR)
            m->req->status = REQ_STATUS_RCVD;
        list_del(&m->req->req_list);
        spin_unlock(&m->client->lock);
        p9_client_cb(m->client, m->req);
        m->rbuf = NULL;
        m->rpos = 0;
        m->rsize = 0;
        m->req = NULL;
    }

end_clear:
    clear_bit(Rworksched, &m->wsched);

    if (!list_empty(&m->req_list)) {
        if (test_and_clear_bit(Rpending, &m->wsched))
            n = POLLIN;
        else
            n = p9_fd_poll(m->client, NULL);

        if ((n & POLLIN) && !test_and_set_bit(Rworksched, &m->wsched)) {
            p9_debug(P9_DEBUG_TRANS, "sched read work %p\n", m);
            schedule_work(&m->rq);
        }
    }

    return;
error:
    p9_conn_cancel(m, err);
    clear_bit(Rworksched, &m->wsched);
}

static int p9_fd_write(struct p9_client *client, void *v, int len)
{
    int ret;
    mm_segment_t oldfs;
    struct p9_trans_fd *ts = NULL;

    if (client && client->status != Disconnected)
        ts = client->trans;

    if (!ts)
        return -EREMOTEIO;

    if (!(ts->wr->f_flags & O_NONBLOCK))
        p9_debug(P9_DEBUG_ERROR, "blocking write ...\n");

    oldfs = get_fs();
    set_fs(get_ds());
    /* The cast to a user pointer is valid due to the set_fs() */
    ret = vfs_write(ts->wr, (__force void __user *)v, len, &ts->wr->f_pos);
    set_fs(oldfs);

    if (ret <= 0 && ret != -ERESTARTSYS && ret != -EAGAIN)
        client->status = Disconnected;
    return ret;
}

static void p9_write_work(struct work_struct *work)
{
    int n, err;
    struct p9_conn *m;
    struct p9_req_t *req;

    m = container_of(work, struct p9_conn, wq);

    if (m->err < 0) {
        clear_bit(Wworksched, &m->wsched);
        return;
    }

    if (!m->wsize) {
        spin_lock(&m->client->lock);
        if (list_empty(&m->unsent_req_list)) {
            clear_bit(Wworksched, &m->wsched);
            spin_unlock(&m->client->lock);
            return;
        }

        req = list_entry(m->unsent_req_list.next, struct p9_req_t,
                   req_list);
        req->status = REQ_STATUS_SENT;
        p9_debug(P9_DEBUG_TRANS, "move req %p\n", req);
        list_move_tail(&req->req_list, &m->req_list);

        m->wbuf = req->tc->sdata;
        m->wsize = req->tc->size;
        m->wpos = 0;
        spin_unlock(&m->client->lock);
    }

    p9_debug(P9_DEBUG_TRANS, "mux %p pos %d size %d\n",
         m, m->wpos, m->wsize);
    clear_bit(Wpending, &m->wsched);
    err = p9_fd_write(m->client, m->wbuf + m->wpos, m->wsize - m->wpos);
    p9_debug(P9_DEBUG_TRANS, "mux %p sent %d bytes\n", m, err);
    if (err == -EAGAIN)
        goto end_clear;


    if (err < 0)
        goto error;
    else if (err == 0) {
        err = -EREMOTEIO;
        goto error;
    }

    m->wpos += err;
    if (m->wpos == m->wsize)
        m->wpos = m->wsize = 0;

end_clear:
    clear_bit(Wworksched, &m->wsched);

    if (m->wsize || !list_empty(&m->unsent_req_list)) {
        if (test_and_clear_bit(Wpending, &m->wsched))
            n = POLLOUT;
        else
            n = p9_fd_poll(m->client, NULL);

        if ((n & POLLOUT) &&
           !test_and_set_bit(Wworksched, &m->wsched)) {
            p9_debug(P9_DEBUG_TRANS, "sched write work %p\n", m);
            schedule_work(&m->wq);
        }
    }

    return;

error:
    p9_conn_cancel(m, err);
    clear_bit(Wworksched, &m->wsched);
}

static int p9_pollwake(wait_queue_t *wait, unsigned int mode, int sync, void *key)
{
    struct p9_poll_wait *pwait =
        container_of(wait, struct p9_poll_wait, wait);
    struct p9_conn *m = pwait->conn;
    unsigned long flags;

    spin_lock_irqsave(&p9_poll_lock, flags);
    if (list_empty(&m->poll_pending_link))
        list_add_tail(&m->poll_pending_link, &p9_poll_pending_list);
    spin_unlock_irqrestore(&p9_poll_lock, flags);

    schedule_work(&p9_poll_work);
    return 1;
}

static void
p9_pollwait(struct file *filp, wait_queue_head_t *wait_address, poll_table *p)
{
    struct p9_conn *m = container_of(p, struct p9_conn, pt);
    struct p9_poll_wait *pwait = NULL;
    int i;

    for (i = 0; i < ARRAY_SIZE(m->poll_wait); i++) {
        if (m->poll_wait[i].wait_addr == NULL) {
            pwait = &m->poll_wait[i];
            break;
        }
    }

    if (!pwait) {
        p9_debug(P9_DEBUG_ERROR, "not enough wait_address slots\n");
        return;
    }

    pwait->conn = m;
    pwait->wait_addr = wait_address;
    init_waitqueue_func_entry(&pwait->wait, p9_pollwake);
    add_wait_queue(wait_address, &pwait->wait);
}

static struct p9_conn *p9_conn_create(struct p9_client *client)
{
    int n;
    struct p9_conn *m;

    p9_debug(P9_DEBUG_TRANS, "client %p msize %d\n", client, client->msize);
    m = kzalloc(sizeof(struct p9_conn), GFP_KERNEL);
    if (!m)
        return ERR_PTR(-ENOMEM);

    INIT_LIST_HEAD(&m->mux_list);
    m->client = client;

    INIT_LIST_HEAD(&m->req_list);
    INIT_LIST_HEAD(&m->unsent_req_list);
    INIT_WORK(&m->rq, p9_read_work);
    INIT_WORK(&m->wq, p9_write_work);
    INIT_LIST_HEAD(&m->poll_pending_link);
    init_poll_funcptr(&m->pt, p9_pollwait);

    n = p9_fd_poll(client, &m->pt);
    if (n & POLLIN) {
        p9_debug(P9_DEBUG_TRANS, "mux %p can read\n", m);
        set_bit(Rpending, &m->wsched);
    }

    if (n & POLLOUT) {
        p9_debug(P9_DEBUG_TRANS, "mux %p can write\n", m);
        set_bit(Wpending, &m->wsched);
    }

    return m;
}

static void p9_poll_mux(struct p9_conn *m)
{
    int n;

    if (m->err < 0)
        return;

    n = p9_fd_poll(m->client, NULL);
    if (n < 0 || n & (POLLERR | POLLHUP | POLLNVAL)) {
        p9_debug(P9_DEBUG_TRANS, "error mux %p err %d\n", m, n);
        if (n >= 0)
            n = -ECONNRESET;
        p9_conn_cancel(m, n);
    }

    if (n & POLLIN) {
        set_bit(Rpending, &m->wsched);
        p9_debug(P9_DEBUG_TRANS, "mux %p can read\n", m);
        if (!test_and_set_bit(Rworksched, &m->wsched)) {
            p9_debug(P9_DEBUG_TRANS, "sched read work %p\n", m);
            schedule_work(&m->rq);
        }
    }

    if (n & POLLOUT) {
        set_bit(Wpending, &m->wsched);
        p9_debug(P9_DEBUG_TRANS, "mux %p can write\n", m);
        if ((m->wsize || !list_empty(&m->unsent_req_list)) &&
            !test_and_set_bit(Wworksched, &m->wsched)) {
            p9_debug(P9_DEBUG_TRANS, "sched write work %p\n", m);
            schedule_work(&m->wq);
        }
    }
}

static int p9_fd_request(struct p9_client *client, struct p9_req_t *req)
{
    int n;
    struct p9_trans_fd *ts = client->trans;
    struct p9_conn *m = ts->conn;

    p9_debug(P9_DEBUG_TRANS, "mux %p task %p tcall %p id %d\n",
         m, current, req->tc, req->tc->id);
    if (m->err < 0)
        return m->err;

    spin_lock(&client->lock);
    req->status = REQ_STATUS_UNSENT;
    list_add_tail(&req->req_list, &m->unsent_req_list);
    spin_unlock(&client->lock);

    if (test_and_clear_bit(Wpending, &m->wsched))
        n = POLLOUT;
    else
        n = p9_fd_poll(m->client, NULL);

    if (n & POLLOUT && !test_and_set_bit(Wworksched, &m->wsched))
        schedule_work(&m->wq);

    return 0;
}

static int p9_fd_cancel(struct p9_client *client, struct p9_req_t *req)
{
    int ret = 1;

    p9_debug(P9_DEBUG_TRANS, "client %p req %p\n", client, req);

    spin_lock(&client->lock);

    if (req->status == REQ_STATUS_UNSENT) {
        list_del(&req->req_list);
        req->status = REQ_STATUS_FLSHD;
        ret = 0;
    } else if (req->status == REQ_STATUS_SENT)
        req->status = REQ_STATUS_FLSH;

    spin_unlock(&client->lock);

    return ret;
}

static int parse_opts(char *params, struct p9_fd_opts *opts)
{
    char *p;
    substring_t args[MAX_OPT_ARGS];
    int option;
    char *options, *tmp_options;

    opts->port = P9_PORT;
    opts->rfd = ~0;
    opts->wfd = ~0;

    if (!params)
        return 0;

    tmp_options = kstrdup(params, GFP_KERNEL);
    if (!tmp_options) {
        p9_debug(P9_DEBUG_ERROR,
             "failed to allocate copy of option string\n");
        return -ENOMEM;
    }
    options = tmp_options;

    while ((p = strsep(&options, ",")) != NULL) {
        int token;
        int r;
        if (!*p)
            continue;
        token = match_token(p, tokens, args);
        if (token != Opt_err) {
            r = match_int(&args[0], &option);
            if (r < 0) {
                p9_debug(P9_DEBUG_ERROR,
                     "integer field, but no integer?\n");
                continue;
            }
        }
        switch (token) {
        case Opt_port:
            opts->port = option;
            break;
        case Opt_rfdno:
            opts->rfd = option;
            break;
        case Opt_wfdno:
            opts->wfd = option;
            break;
        default:
            continue;
        }
    }

    kfree(tmp_options);
    return 0;
}

static int p9_fd_open(struct p9_client *client, int rfd, int wfd)
{
    struct p9_trans_fd *ts = kmalloc(sizeof(struct p9_trans_fd),
                       GFP_KERNEL);
    if (!ts)
        return -ENOMEM;

    ts->rd = fget(rfd);
    ts->wr = fget(wfd);
    if (!ts->rd || !ts->wr) {
        if (ts->rd)
            fput(ts->rd);
        if (ts->wr)
            fput(ts->wr);
        kfree(ts);
        return -EIO;
    }

    client->trans = ts;
    client->status = Connected;

    return 0;
}

static int p9_socket_open(struct p9_client *client, struct socket *csocket)
{
    struct p9_trans_fd *p;
    struct file *file;
    int ret;

    p = kmalloc(sizeof(struct p9_trans_fd), GFP_KERNEL);
    if (!p)
        return -ENOMEM;

    csocket->sk->sk_allocation = GFP_NOIO;
    file = sock_alloc_file(csocket, 0, NULL);
    if (IS_ERR(file)) {
        pr_err("%s (%d): failed to map fd\n",
               __func__, task_pid_nr(current));
        sock_release(csocket);
        kfree(p);
        return PTR_ERR(file);
    }

    get_file(file);
    p->wr = p->rd = file;
    client->trans = p;
    client->status = Connected;

    p->rd->f_flags |= O_NONBLOCK;

    p->conn = p9_conn_create(client);
    if (IS_ERR(p->conn)) {
        ret = PTR_ERR(p->conn);
        p->conn = NULL;
        kfree(p);
        sockfd_put(csocket);
        sockfd_put(csocket);
        return ret;
    }
    return 0;
}

static void p9_conn_destroy(struct p9_conn *m)
{
    p9_debug(P9_DEBUG_TRANS, "mux %p prev %p next %p\n",
         m, m->mux_list.prev, m->mux_list.next);

    p9_mux_poll_stop(m);
    cancel_work_sync(&m->rq);
    cancel_work_sync(&m->wq);

    p9_conn_cancel(m, -ECONNRESET);

    m->client = NULL;
    kfree(m);
}

static void p9_fd_close(struct p9_client *client)
{
    struct p9_trans_fd *ts;

    if (!client)
        return;

    ts = client->trans;
    if (!ts)
        return;

    client->status = Disconnected;

    p9_conn_destroy(ts->conn);

    if (ts->rd)
        fput(ts->rd);
    if (ts->wr)
        fput(ts->wr);

    kfree(ts);
}

/*
 * stolen from NFS - maybe should be made a generic function?
 */
static inline int valid_ipaddr4(const char *buf)
{
    int rc, count, in[4];

    rc = sscanf(buf, "%d.%d.%d.%d", &in[0], &in[1], &in[2], &in[3]);
    if (rc != 4)
        return -EINVAL;
    for (count = 0; count < 4; count++) {
        if (in[count] > 255)
            return -EINVAL;
    }
    return 0;
}

static int
p9_fd_create_tcp(struct p9_client *client, const char *addr, char *args)
{
    int err;
    struct socket *csocket;
    struct sockaddr_in sin_server;
    struct p9_fd_opts opts;

    err = parse_opts(args, &opts);
    if (err < 0)
        return err;

    if (valid_ipaddr4(addr) < 0)
        return -EINVAL;

    csocket = NULL;

    sin_server.sin_family = AF_INET;
    sin_server.sin_addr.s_addr = in_aton(addr);
    sin_server.sin_port = htons(opts.port);
    err = __sock_create(read_pnet(&current->nsproxy->net_ns), PF_INET,
                SOCK_STREAM, IPPROTO_TCP, &csocket, 1);
    if (err) {
        pr_err("%s (%d): problem creating socket\n",
               __func__, task_pid_nr(current));
        return err;
    }

    err = csocket->ops->connect(csocket,
                    (struct sockaddr *)&sin_server,
                    sizeof(struct sockaddr_in), 0);
    if (err < 0) {
        pr_err("%s (%d): problem connecting socket to %s\n",
               __func__, task_pid_nr(current), addr);
        sock_release(csocket);
        return err;
    }

    return p9_socket_open(client, csocket);
}

static int
p9_fd_create_unix(struct p9_client *client, const char *addr, char *args)
{
    int err;
    struct socket *csocket;
    struct sockaddr_un sun_server;

    csocket = NULL;

    if (strlen(addr) >= UNIX_PATH_MAX) {
        pr_err("%s (%d): address too long: %s\n",
               __func__, task_pid_nr(current), addr);
        return -ENAMETOOLONG;
    }

    sun_server.sun_family = PF_UNIX;
    strcpy(sun_server.sun_path, addr);
    err = __sock_create(read_pnet(&current->nsproxy->net_ns), PF_UNIX,
                SOCK_STREAM, 0, &csocket, 1);
    if (err < 0) {
        pr_err("%s (%d): problem creating socket\n",
               __func__, task_pid_nr(current));

        return err;
    }
    err = csocket->ops->connect(csocket, (struct sockaddr *)&sun_server,
            sizeof(struct sockaddr_un) - 1, 0);
    if (err < 0) {
        pr_err("%s (%d): problem connecting socket: %s: %d\n",
               __func__, task_pid_nr(current), addr, err);
        sock_release(csocket);
        return err;
    }

    return p9_socket_open(client, csocket);
}

static int
p9_fd_create(struct p9_client *client, const char *addr, char *args)
{
    int err;
    struct p9_fd_opts opts;
    struct p9_trans_fd *p;

    parse_opts(args, &opts);

    if (opts.rfd == ~0 || opts.wfd == ~0) {
        pr_err("Insufficient options for proto=fd\n");
        return -ENOPROTOOPT;
    }

    err = p9_fd_open(client, opts.rfd, opts.wfd);
    if (err < 0)
        return err;

    p = (struct p9_trans_fd *) client->trans;
    p->conn = p9_conn_create(client);
    if (IS_ERR(p->conn)) {
        err = PTR_ERR(p->conn);
        p->conn = NULL;
        fput(p->rd);
        fput(p->wr);
        return err;
    }

    return 0;
}

static struct p9_trans_module p9_tcp_trans = {
    .name = "tcp",
    .maxsize = MAX_SOCK_BUF,
    .def = 1,
    .create = p9_fd_create_tcp,
    .close = p9_fd_close,
    .request = p9_fd_request,
    .cancel = p9_fd_cancel,
    .owner = THIS_MODULE,
};

static struct p9_trans_module p9_unix_trans = {
    .name = "unix",
    .maxsize = MAX_SOCK_BUF,
    .def = 0,
    .create = p9_fd_create_unix,
    .close = p9_fd_close,
    .request = p9_fd_request,
    .cancel = p9_fd_cancel,
    .owner = THIS_MODULE,
};

static struct p9_trans_module p9_fd_trans = {
    .name = "fd",
    .maxsize = MAX_SOCK_BUF,
    .def = 0,
    .create = p9_fd_create,
    .close = p9_fd_close,
    .request = p9_fd_request,
    .cancel = p9_fd_cancel,
    .owner = THIS_MODULE,
};

static void p9_poll_workfn(struct work_struct *work)
{
    unsigned long flags;

    p9_debug(P9_DEBUG_TRANS, "start %p\n", current);

    spin_lock_irqsave(&p9_poll_lock, flags);
    while (!list_empty(&p9_poll_pending_list)) {
        struct p9_conn *conn = list_first_entry(&p9_poll_pending_list,
                            struct p9_conn,
                            poll_pending_link);
        list_del_init(&conn->poll_pending_link);
        spin_unlock_irqrestore(&p9_poll_lock, flags);

        p9_poll_mux(conn);

        spin_lock_irqsave(&p9_poll_lock, flags);
    }
    spin_unlock_irqrestore(&p9_poll_lock, flags);

    p9_debug(P9_DEBUG_TRANS, "finish\n");
}

int p9_trans_fd_init(void)
{
    v9fs_register_trans(&p9_tcp_trans);
    v9fs_register_trans(&p9_unix_trans);
    v9fs_register_trans(&p9_fd_trans);

    return 0;
}

void p9_trans_fd_exit(void)
{
    flush_work(&p9_poll_work);
    v9fs_unregister_trans(&p9_tcp_trans);
    v9fs_unregister_trans(&p9_unix_trans);
    v9fs_unregister_trans(&p9_fd_trans);
}