Merge with Linux 2.5.48.

[linux-2.6/linux-mips.git] / net / sunrpc / xprt.c

/*
 *  linux/net/sunrpc/xprt.c
 *
 *  This is a generic RPC call interface supporting congestion avoidance,
 *  and asynchronous calls.
 *
 *  The interface works like this:
 *
 *  -   When a process places a call, it allocates a request slot if
 *      one is available. Otherwise, it sleeps on the backlog queue
 *      (xprt_reserve).
 *  -   Next, the caller puts together the RPC message, stuffs it into
 *      the request struct, and calls xprt_call().
 *  -   xprt_call transmits the message and installs the caller on the
 *      socket's wait list. At the same time, it installs a timer that
 *      is run after the packet's timeout has expired.
 *  -   When a packet arrives, the data_ready handler walks the list of
 *      pending requests for that socket. If a matching XID is found, the
 *      caller is woken up, and the timer removed.
 *  -   When no reply arrives within the timeout interval, the timer is
 *      fired by the kernel and runs xprt_timer(). It either adjusts the
 *      timeout values (minor timeout) or wakes up the caller with a status
 *      of -ETIMEDOUT.
 *  -   When the caller receives a notification from RPC that a reply arrived,
 *      it should release the RPC slot, and process the reply.
 *      If the call timed out, it may choose to retry the operation by
 *      adjusting the initial timeout value, and simply calling rpc_call
 *      again.
 *
 *  Support for async RPC is done through a set of RPC-specific scheduling
 *  primitives that `transparently' work for processes as well as async
 *  tasks that rely on callbacks.
 *
 *  Copyright (C) 1995-1997, Olaf Kirch <okir@monad.swb.de>
 *
 *  TCP callback races fixes (C) 1998 Red Hat Software <alan@redhat.com>
 *  TCP send fixes (C) 1998 Red Hat Software <alan@redhat.com>
 *  TCP NFS related read + write fixes
 *   (C) 1999 Dave Airlie, University of Limerick, Ireland <airlied@linux.ie>
 *
 *  Rewrite of larges part of the code in order to stabilize TCP stuff.
 *  Fix behaviour when socket buffer is full.
 *   (C) 1999 Trond Myklebust <trond.myklebust@fys.uio.no>
 */

#define __KERNEL_SYSCALLS__

#include <linux/version.h>
#include <linux/types.h>
#include <linux/slab.h>
#include <linux/capability.h>
#include <linux/sched.h>
#include <linux/errno.h>
#include <linux/socket.h>
#include <linux/in.h>
#include <linux/net.h>
#include <linux/mm.h>
#include <linux/udp.h>
#include <linux/tcp.h>
#include <linux/unistd.h>
#include <linux/sunrpc/clnt.h>
#include <linux/file.h>

#include <net/sock.h>
#include <net/checksum.h>
#include <net/udp.h>
#include <net/tcp.h>

#include <asm/uaccess.h>

/*
 * Local variables
 */

#ifdef RPC_DEBUG
# undef  RPC_DEBUG_DATA
# define RPCDBG_FACILITY        RPCDBG_XPRT
#endif

#define XPRT_MAX_BACKOFF        (8)

/*
 * Local functions
 */
static void     xprt_request_init(struct rpc_task *, struct rpc_xprt *);
static void     do_xprt_transmit(struct rpc_task *);
static inline void      do_xprt_reserve(struct rpc_task *);
static void     xprt_disconnect(struct rpc_xprt *);
static void     xprt_conn_status(struct rpc_task *task);
static struct rpc_xprt * xprt_setup(int proto, struct sockaddr_in *ap,
                                                struct rpc_timeout *to);
static struct socket *xprt_create_socket(int, struct rpc_timeout *, int);
static void     xprt_bind_socket(struct rpc_xprt *, struct socket *);
static int      __xprt_get_cong(struct rpc_xprt *, struct rpc_task *);

#ifdef RPC_DEBUG_DATA
/*
 * Print the buffer contents (first 128 bytes only--just enough for
 * diropres return).
 */
static void
xprt_pktdump(char *msg, u32 *packet, unsigned int count)
{
        u8      *buf = (u8 *) packet;
        int     j;

        dprintk("RPC:      %s\n", msg);
        for (j = 0; j < count && j < 128; j += 4) {
                if (!(j & 31)) {
                        if (j)
                                dprintk("\n");
                        dprintk("0x%04x ", j);
                }
                dprintk("%02x%02x%02x%02x ",
                        buf[j], buf[j+1], buf[j+2], buf[j+3]);
        }
        dprintk("\n");
}
#else
static inline void
xprt_pktdump(char *msg, u32 *packet, unsigned int count)
{
        /* NOP */
}
#endif

/*
 * Look up RPC transport given an INET socket
 */
static inline struct rpc_xprt *
xprt_from_sock(struct sock *sk)
{
        return (struct rpc_xprt *) sk->user_data;
}

/*
 * Serialize write access to sockets, in order to prevent different
 * requests from interfering with each other.
 * Also prevents TCP socket connects from colliding with writes.
 */
static int
__xprt_lock_write(struct rpc_xprt *xprt, struct rpc_task *task)
{
        if (!xprt->snd_task) {
                if (xprt->nocong || __xprt_get_cong(xprt, task))
                        xprt->snd_task = task;
        }
        if (xprt->snd_task != task) {
                dprintk("RPC: %4d TCP write queue full\n", task->tk_pid);
                task->tk_timeout = 0;
                task->tk_status = -EAGAIN;
                if (task->tk_rqstp && task->tk_rqstp->rq_nresend)
                        rpc_sleep_on(&xprt->resend, task, NULL, NULL);
                else
                        rpc_sleep_on(&xprt->sending, task, NULL, NULL);
        }
        return xprt->snd_task == task;
}

static inline int
xprt_lock_write(struct rpc_xprt *xprt, struct rpc_task *task)
{
        int retval;

        spin_lock_bh(&xprt->sock_lock);
        retval = __xprt_lock_write(xprt, task);
        spin_unlock_bh(&xprt->sock_lock);
        return retval;
}


static void
__xprt_lock_write_next(struct rpc_xprt *xprt)
{
        struct rpc_task *task;

        if (xprt->snd_task)
                return;
        if (!xprt->nocong && RPCXPRT_CONGESTED(xprt))
                return;
        task = rpc_wake_up_next(&xprt->resend);
        if (!task) {
                task = rpc_wake_up_next(&xprt->sending);
                if (!task)
                        return;
        }
        if (xprt->nocong || __xprt_get_cong(xprt, task))
                xprt->snd_task = task;
}

/*
 * Releases the socket for use by other requests.
 */
static void
__xprt_release_write(struct rpc_xprt *xprt, struct rpc_task *task)
{
        if (xprt->snd_task == task)
                xprt->snd_task = NULL;
        __xprt_lock_write_next(xprt);
}

static inline void
xprt_release_write(struct rpc_xprt *xprt, struct rpc_task *task)
{
        spin_lock_bh(&xprt->sock_lock);
        __xprt_release_write(xprt, task);
        spin_unlock_bh(&xprt->sock_lock);
}

/*
 * Write data to socket.
 */
static inline int
xprt_sendmsg(struct rpc_xprt *xprt, struct rpc_rqst *req)
{
        struct socket   *sock = xprt->sock;
        struct msghdr   msg;
        struct xdr_buf  *xdr = &req->rq_snd_buf;
        struct iovec    niv[MAX_IOVEC];
        unsigned int    niov, slen, skip;
        mm_segment_t    oldfs;
        int             result;

        if (!sock)
                return -ENOTCONN;

        xprt_pktdump("packet data:",
                                req->rq_svec->iov_base,
                                req->rq_svec->iov_len);

        /* Dont repeat bytes */
        skip = req->rq_bytes_sent;
        slen = xdr->len - skip;
        niov = xdr_kmap(niv, xdr, skip);

        msg.msg_flags   = MSG_DONTWAIT|MSG_NOSIGNAL;
        msg.msg_iov     = niv;
        msg.msg_iovlen  = niov;
        msg.msg_name    = (struct sockaddr *) &xprt->addr;
        msg.msg_namelen = sizeof(xprt->addr);
        msg.msg_control = NULL;
        msg.msg_controllen = 0;

        oldfs = get_fs(); set_fs(get_ds());
        clear_bit(SOCK_ASYNC_NOSPACE, &sock->flags);
        result = sock_sendmsg(sock, &msg, slen);
        set_fs(oldfs);

        xdr_kunmap(xdr, skip);

        dprintk("RPC:      xprt_sendmsg(%d) = %d\n", slen, result);

        if (result >= 0)
                return result;

        switch (result) {
        case -ECONNREFUSED:
                /* When the server has died, an ICMP port unreachable message
                 * prompts ECONNREFUSED.
                 */
        case -EAGAIN:
                break;
        case -ENOTCONN:
        case -EPIPE:
                /* connection broken */
                if (xprt->stream)
                        result = -ENOTCONN;
                break;
        default:
                printk(KERN_NOTICE "RPC: sendmsg returned error %d\n", -result);
        }
        return result;
}

/*
 * Van Jacobson congestion avoidance. Check if the congestion window
 * overflowed. Put the task to sleep if this is the case.
 */
static int
__xprt_get_cong(struct rpc_xprt *xprt, struct rpc_task *task)
{
        struct rpc_rqst *req = task->tk_rqstp;

        if (req->rq_cong)
                return 1;
        dprintk("RPC: %4d xprt_cwnd_limited cong = %ld cwnd = %ld\n",
                        task->tk_pid, xprt->cong, xprt->cwnd);
        if (RPCXPRT_CONGESTED(xprt))
                return 0;
        req->rq_cong = 1;
        xprt->cong += RPC_CWNDSCALE;
        return 1;
}

/*
 * Adjust the congestion window, and wake up the next task
 * that has been sleeping due to congestion
 */
static void
__xprt_put_cong(struct rpc_xprt *xprt, struct rpc_rqst *req)
{
        if (!req->rq_cong)
                return;
        req->rq_cong = 0;
        xprt->cong -= RPC_CWNDSCALE;
        __xprt_lock_write_next(xprt);
}

/*
 * Adjust RPC congestion window
 * We use a time-smoothed congestion estimator to avoid heavy oscillation.
 */
static void
xprt_adjust_cwnd(struct rpc_xprt *xprt, int result)
{
        unsigned long   cwnd;

        cwnd = xprt->cwnd;
        if (result >= 0 && cwnd <= xprt->cong) {
                /* The (cwnd >> 1) term makes sure
                 * the result gets rounded properly. */
                cwnd += (RPC_CWNDSCALE * RPC_CWNDSCALE + (cwnd >> 1)) / cwnd;
                if (cwnd > RPC_MAXCWND)
                        cwnd = RPC_MAXCWND;
                __xprt_lock_write_next(xprt);
        } else if (result == -ETIMEDOUT) {
                cwnd >>= 1;
                if (cwnd < RPC_CWNDSCALE)
                        cwnd = RPC_CWNDSCALE;
        }
        dprintk("RPC:      cong %ld, cwnd was %ld, now %ld\n",
                        xprt->cong, xprt->cwnd, cwnd);
        xprt->cwnd = cwnd;
}

/*
 * Adjust timeout values etc for next retransmit
 */
int
xprt_adjust_timeout(struct rpc_timeout *to)
{
        if (to->to_retries > 0) {
                if (to->to_exponential)
                        to->to_current <<= 1;
                else
                        to->to_current += to->to_increment;
                if (to->to_maxval && to->to_current >= to->to_maxval)
                        to->to_current = to->to_maxval;
        } else {
                if (to->to_exponential)
                        to->to_initval <<= 1;
                else
                        to->to_initval += to->to_increment;
                if (to->to_maxval && to->to_initval >= to->to_maxval)
                        to->to_initval = to->to_maxval;
                to->to_current = to->to_initval;
        }

        if (!to->to_current) {
                printk(KERN_WARNING "xprt_adjust_timeout: to_current = 0!\n");
                to->to_current = 5 * HZ;
        }
        pprintk("RPC: %lu %s\n", jiffies,
                        to->to_retries? "retrans" : "timeout");
        return to->to_retries-- > 0;
}

/*
 * Close down a transport socket
 */
static void
xprt_close(struct rpc_xprt *xprt)
{
        struct socket   *sock = xprt->sock;
        struct sock     *sk = xprt->inet;

        if (!sk)
                return;

        xprt->inet = NULL;
        xprt->sock = NULL;

        sk->user_data    = NULL;
        sk->data_ready   = xprt->old_data_ready;
        sk->state_change = xprt->old_state_change;
        sk->write_space  = xprt->old_write_space;

        xprt_disconnect(xprt);
        sk->no_check     = 0;

        sock_release(sock);
}

/*
 * Mark a transport as disconnected
 */
static void
xprt_disconnect(struct rpc_xprt *xprt)
{
        dprintk("RPC:      disconnected transport %p\n", xprt);
        xprt_clear_connected(xprt);
        rpc_wake_up_status(&xprt->pending, -ENOTCONN);
}

/*
 * Attempt to connect a TCP socket.
 *
 * NB: This never collides with TCP reads, as both run from rpciod
 */
void
xprt_connect(struct rpc_task *task)
{
        struct rpc_xprt *xprt = task->tk_xprt;
        struct socket   *sock = xprt->sock;
        struct sock     *inet;
        int             status;

        dprintk("RPC: %4d xprt_connect xprt %p %s connected\n", task->tk_pid,
                        xprt, (xprt_connected(xprt) ? "is" : "is not"));

        if (xprt->shutdown) {
                task->tk_status = -EIO;
                return;
        }
        if (!xprt->addr.sin_port) {
                task->tk_status = -EIO;
                return;
        }
        if (!xprt_lock_write(xprt, task))
                return;
        if (xprt_connected(xprt))
                goto out_write;

        /*
         * We're here because the xprt was marked disconnected.
         * Start by resetting any existing state.
         */
        xprt_close(xprt);
        if (!(sock = xprt_create_socket(xprt->prot, &xprt->timeout, xprt->resvport))) {
                /* couldn't create socket or bind to reserved port;
                 * this is likely a permanent error, so cause an abort */
                task->tk_status = -EIO;
                goto out_write;
        }
        xprt_bind_socket(xprt, sock);
        inet = sock->sk;

        /*
         * Tell the socket layer to start connecting...
         */
        status = sock->ops->connect(sock, (struct sockaddr *) &xprt->addr,
                                sizeof(xprt->addr), O_NONBLOCK);
        dprintk("RPC: %4d  connect status %d connected %d sock state %d\n",
                task->tk_pid, -status, xprt_connected(xprt), inet->state);

        switch (status) {
        case -EINPROGRESS:
        case -EALREADY:
                /* Protect against TCP socket state changes */
                lock_sock(inet);
                if (inet->state != TCP_ESTABLISHED) {
                        dprintk("RPC: %4d  waiting for connection\n",
                                        task->tk_pid);
                        task->tk_timeout = RPC_CONNECT_TIMEOUT;
                        /* if the socket is already closing, delay briefly */
                        if ((1 << inet->state) & ~(TCPF_SYN_SENT|TCPF_SYN_RECV))
                                task->tk_timeout = RPC_REESTABLISH_TIMEOUT;
                        rpc_sleep_on(&xprt->pending, task, xprt_conn_status,
                                                                        NULL);
                        release_sock(inet);
                        /* task status set when task wakes up again */
                        return;
                }
                release_sock(inet);
                task->tk_status = 0;
                break;

        case 0:
        case -EISCONN:  /* not likely, but just in case */
                /* Half closed state.  No race -- this socket is dead. */
                if (inet->state != TCP_ESTABLISHED) {
                        xprt_close(xprt);
                        task->tk_status = -EAGAIN;
                        goto out_write;
                }

                /* Otherwise, the connection is already established. */
                task->tk_status = 0;
                break;

        case -EPIPE:
                xprt_close(xprt);
                task->tk_status = -ENOTCONN;
                goto out_write;

        default:
                /* Report myriad other possible returns.  If this file
                 * system is soft mounted, just error out, like Solaris.  */
                xprt_close(xprt);
                if (task->tk_client->cl_softrtry) {
                        printk(KERN_WARNING
                        "RPC: error %d connecting to server %s, exiting\n",
                                        -status, task->tk_client->cl_server);
                        task->tk_status = -EIO;
                } else {
                        printk(KERN_WARNING
                        "RPC: error %d connecting to server %s\n",
                                        -status, task->tk_client->cl_server);
                        rpc_delay(task, RPC_REESTABLISH_TIMEOUT);
                        task->tk_status = status;
                }
                break;
        }

 out_write:
        xprt_release_write(xprt, task);
}

/*
 * We arrive here when awoken from waiting on connection establishment.
 */
static void
xprt_conn_status(struct rpc_task *task)
{
        struct rpc_xprt *xprt = task->tk_xprt;

        switch (task->tk_status) {
        case 0:
                dprintk("RPC: %4d xprt_conn_status: connection established\n",
                                task->tk_pid);
                goto out;
        case -ETIMEDOUT:
                dprintk("RPC: %4d xprt_conn_status: timed out\n",
                                task->tk_pid);
                /* prevent TCP from continuing to retry SYNs */
                xprt_close(xprt);
                break;
        default:
                printk(KERN_ERR "RPC: error %d connecting to server %s\n",
                                -task->tk_status, task->tk_client->cl_server);
                xprt_close(xprt);
                rpc_delay(task, RPC_REESTABLISH_TIMEOUT);
                break;
        }
        /* if soft mounted, cause this RPC to fail */
        if (task->tk_client->cl_softrtry)
                task->tk_status = -EIO;

 out:
        xprt_release_write(xprt, task);
}

/*
 * Look up the RPC request corresponding to a reply, and then lock it.
 */
static inline struct rpc_rqst *
xprt_lookup_rqst(struct rpc_xprt *xprt, u32 xid)
{
        struct list_head *pos;
        struct rpc_rqst *req = NULL;

        list_for_each(pos, &xprt->recv) {
                struct rpc_rqst *entry = list_entry(pos, struct rpc_rqst, rq_list);
                if (entry->rq_xid == xid) {
                        req = entry;
                        break;
                }
        }
        return req;
}

/*
 * Complete reply received.
 * The TCP code relies on us to remove the request from xprt->pending.
 */
static void
xprt_complete_rqst(struct rpc_xprt *xprt, struct rpc_rqst *req, int copied)
{
        struct rpc_task *task = req->rq_task;
        struct rpc_clnt *clnt = task->tk_client;

        /* Adjust congestion window */
        if (!xprt->nocong) {
                xprt_adjust_cwnd(xprt, copied);
                __xprt_put_cong(xprt, req);
                if (!req->rq_nresend) {
                        unsigned timer =
                                task->tk_msg.rpc_proc->p_timer;
                        if (timer)
                                rpc_update_rtt(&clnt->cl_rtt, timer,
                                                (long)jiffies - req->rq_xtime);
                }
                rpc_clear_timeo(&clnt->cl_rtt);
        }

#ifdef RPC_PROFILE
        /* Profile only reads for now */
        if (copied > 1024) {
                static unsigned long    nextstat = 0;
                static unsigned long    pkt_rtt = 0, pkt_len = 0, pkt_cnt = 0;

                pkt_cnt++;
                pkt_len += req->rq_slen + copied;
                pkt_rtt += jiffies - req->rq_xtime;
                if (time_before(nextstat, jiffies)) {
                        printk("RPC: %lu %ld cwnd\n", jiffies, xprt->cwnd);
                        printk("RPC: %ld %ld %ld %ld stat\n",
                                        jiffies, pkt_cnt, pkt_len, pkt_rtt);
                        pkt_rtt = pkt_len = pkt_cnt = 0;
                        nextstat = jiffies + 5 * HZ;
                }
        }
#endif

        dprintk("RPC: %4d has input (%d bytes)\n", task->tk_pid, copied);
        req->rq_received = copied;
        list_del_init(&req->rq_list);

        /* ... and wake up the process. */
        rpc_wake_up_task(task);
        return;
}

static size_t
skb_read_bits(skb_reader_t *desc, void *to, size_t len)
{
        if (len > desc->count)
                len = desc->count;
        skb_copy_bits(desc->skb, desc->offset, to, len);
        desc->count -= len;
        desc->offset += len;
        return len;
}

static size_t
skb_read_and_csum_bits(skb_reader_t *desc, void *to, size_t len)
{
        unsigned int csum2, pos;

        if (len > desc->count)
                len = desc->count;
        pos = desc->offset;
        csum2 = skb_copy_and_csum_bits(desc->skb, pos, to, len, 0);
        desc->csum = csum_block_add(desc->csum, csum2, pos);
        desc->count -= len;
        desc->offset += len;
        return len;
}

/*
 * We have set things up such that we perform the checksum of the UDP
 * packet in parallel with the copies into the RPC client iovec.  -DaveM
 */
int
csum_partial_copy_to_xdr(struct xdr_buf *xdr, struct sk_buff *skb)
{
        skb_reader_t desc;

        desc.skb = skb;
        desc.offset = sizeof(struct udphdr);
        desc.count = skb->len - desc.offset;

        if (skb->ip_summed == CHECKSUM_UNNECESSARY)
                goto no_checksum;

        desc.csum = csum_partial(skb->data, desc.offset, skb->csum);
        xdr_partial_copy_from_skb(xdr, 0, &desc, skb_read_and_csum_bits);
        if (desc.offset != skb->len) {
                unsigned int csum2;
                csum2 = skb_checksum(skb, desc.offset, skb->len - desc.offset, 0);
                desc.csum = csum_block_add(desc.csum, csum2, desc.offset);
        }
        if ((unsigned short)csum_fold(desc.csum))
                return -1;
        return 0;
no_checksum:
        xdr_partial_copy_from_skb(xdr, 0, &desc, skb_read_bits);
        return 0;
}

/*
 * Input handler for RPC replies. Called from a bottom half and hence
 * atomic.
 */
static void
udp_data_ready(struct sock *sk, int len)
{
        struct rpc_task *task;
        struct rpc_xprt *xprt;
        struct rpc_rqst *rovr;
        struct sk_buff  *skb;
        int             err, repsize, copied;

        dprintk("RPC:      udp_data_ready...\n");
        if (!(xprt = xprt_from_sock(sk))) {
                printk("RPC:      udp_data_ready request not found!\n");
                goto out;
        }

        dprintk("RPC:      udp_data_ready client %p\n", xprt);

        if ((skb = skb_recv_datagram(sk, 0, 1, &err)) == NULL)
                goto out;

        if (xprt->shutdown)
                goto dropit;

        repsize = skb->len - sizeof(struct udphdr);
        if (repsize < 4) {
                printk("RPC: impossible RPC reply size %d!\n", repsize);
                goto dropit;
        }

        /* Look up and lock the request corresponding to the given XID */
        spin_lock(&xprt->sock_lock);
        rovr = xprt_lookup_rqst(xprt, *(u32 *) (skb->h.raw + sizeof(struct udphdr)));
        if (!rovr)
                goto out_unlock;
        task = rovr->rq_task;

        dprintk("RPC: %4d received reply\n", task->tk_pid);
        xprt_pktdump("packet data:",
                     (u32 *) (skb->h.raw+sizeof(struct udphdr)), repsize);

        if ((copied = rovr->rq_rlen) > repsize)
                copied = repsize;

        /* Suck it into the iovec, verify checksum if not done by hw. */
        if (csum_partial_copy_to_xdr(&rovr->rq_rcv_buf, skb))
                goto out_unlock;

        /* Something worked... */
        dst_confirm(skb->dst);

        xprt_complete_rqst(xprt, rovr, copied);

 out_unlock:
        spin_unlock(&xprt->sock_lock);
 dropit:
        skb_free_datagram(sk, skb);
 out:
        if (sk->sleep && waitqueue_active(sk->sleep))
                wake_up_interruptible(sk->sleep);
}

/*
 * Copy from an skb into memory and shrink the skb.
 */
static inline size_t
tcp_copy_data(skb_reader_t *desc, void *p, size_t len)
{
        if (len > desc->count)
                len = desc->count;
        skb_copy_bits(desc->skb, desc->offset, p, len);
        desc->offset += len;
        desc->count -= len;
        return len;
}

/*
 * TCP read fragment marker
 */
static inline void
tcp_read_fraghdr(struct rpc_xprt *xprt, skb_reader_t *desc)
{
        size_t len, used;
        char *p;

        p = ((char *) &xprt->tcp_recm) + xprt->tcp_offset;
        len = sizeof(xprt->tcp_recm) - xprt->tcp_offset;
        used = tcp_copy_data(desc, p, len);
        xprt->tcp_offset += used;
        if (used != len)
                return;
        xprt->tcp_reclen = ntohl(xprt->tcp_recm);
        if (xprt->tcp_reclen & 0x80000000)
                xprt->tcp_flags |= XPRT_LAST_FRAG;
        else
                xprt->tcp_flags &= ~XPRT_LAST_FRAG;
        xprt->tcp_reclen &= 0x7fffffff;
        xprt->tcp_flags &= ~XPRT_COPY_RECM;
        xprt->tcp_offset = 0;
        /* Sanity check of the record length */
        if (xprt->tcp_reclen < 4) {
                printk(KERN_ERR "RPC: Invalid TCP record fragment length\n");
                xprt_disconnect(xprt);
        }
        dprintk("RPC:      reading TCP record fragment of length %d\n",
                        xprt->tcp_reclen);
}

static void
tcp_check_recm(struct rpc_xprt *xprt)
{
        if (xprt->tcp_offset == xprt->tcp_reclen) {
                xprt->tcp_flags |= XPRT_COPY_RECM;
                xprt->tcp_offset = 0;
                if (xprt->tcp_flags & XPRT_LAST_FRAG) {
                        xprt->tcp_flags &= ~XPRT_COPY_DATA;
                        xprt->tcp_flags |= XPRT_COPY_XID;
                        xprt->tcp_copied = 0;
                }
        }
}

/*
 * TCP read xid
 */
static inline void
tcp_read_xid(struct rpc_xprt *xprt, skb_reader_t *desc)
{
        size_t len, used;
        char *p;

        len = sizeof(xprt->tcp_xid) - xprt->tcp_offset;
        dprintk("RPC:      reading XID (%Zu bytes)\n", len);
        p = ((char *) &xprt->tcp_xid) + xprt->tcp_offset;
        used = tcp_copy_data(desc, p, len);
        xprt->tcp_offset += used;
        if (used != len)
                return;
        xprt->tcp_flags &= ~XPRT_COPY_XID;
        xprt->tcp_flags |= XPRT_COPY_DATA;
        xprt->tcp_copied = 4;
        dprintk("RPC:      reading reply for XID %08x\n", xprt->tcp_xid);
        tcp_check_recm(xprt);
}

/*
 * TCP read and complete request
 */
static inline void
tcp_read_request(struct rpc_xprt *xprt, skb_reader_t *desc)
{
        struct rpc_rqst *req;
        struct xdr_buf *rcvbuf;
        size_t len;

        /* Find and lock the request corresponding to this xid */
        spin_lock(&xprt->sock_lock);
        req = xprt_lookup_rqst(xprt, xprt->tcp_xid);
        if (!req) {
                xprt->tcp_flags &= ~XPRT_COPY_DATA;
                dprintk("RPC:      XID %08x request not found!\n",
                                xprt->tcp_xid);
                spin_unlock(&xprt->sock_lock);
                return;
        }

        rcvbuf = &req->rq_rcv_buf;
        len = desc->count;
        if (len > xprt->tcp_reclen - xprt->tcp_offset) {
                skb_reader_t my_desc;

                len = xprt->tcp_reclen - xprt->tcp_offset;
                memcpy(&my_desc, desc, sizeof(my_desc));
                my_desc.count = len;
                xdr_partial_copy_from_skb(rcvbuf, xprt->tcp_copied,
                                          &my_desc, tcp_copy_data);
                desc->count -= len;
                desc->offset += len;
        } else
                xdr_partial_copy_from_skb(rcvbuf, xprt->tcp_copied,
                                          desc, tcp_copy_data);
        xprt->tcp_copied += len;
        xprt->tcp_offset += len;

        if (xprt->tcp_copied == req->rq_rlen)
                xprt->tcp_flags &= ~XPRT_COPY_DATA;
        else if (xprt->tcp_offset == xprt->tcp_reclen) {
                if (xprt->tcp_flags & XPRT_LAST_FRAG)
                        xprt->tcp_flags &= ~XPRT_COPY_DATA;
        }

        if (!(xprt->tcp_flags & XPRT_COPY_DATA)) {
                dprintk("RPC: %4d received reply complete\n",
                                req->rq_task->tk_pid);
                xprt_complete_rqst(xprt, req, xprt->tcp_copied);
        }
        spin_unlock(&xprt->sock_lock);
        tcp_check_recm(xprt);
}

/*
 * TCP discard extra bytes from a short read
 */
static inline void
tcp_read_discard(struct rpc_xprt *xprt, skb_reader_t *desc)
{
        size_t len;

        len = xprt->tcp_reclen - xprt->tcp_offset;
        if (len > desc->count)
                len = desc->count;
        desc->count -= len;
        desc->offset += len;
        xprt->tcp_offset += len;
        tcp_check_recm(xprt);
}

/*
 * TCP record receive routine
 * We first have to grab the record marker, then the XID, then the data.
 */
static int
tcp_data_recv(read_descriptor_t *rd_desc, struct sk_buff *skb,
                unsigned int offset, size_t len)
{
        struct rpc_xprt *xprt = (struct rpc_xprt *)rd_desc->buf;
        skb_reader_t desc = {
                .skb    = skb,
                .offset = offset,
                .count  = len,
                .csum   = 0
        };

        dprintk("RPC:      tcp_data_recv\n");
        do {
                /* Read in a new fragment marker if necessary */
                /* Can we ever really expect to get completely empty fragments? */
                if (xprt->tcp_flags & XPRT_COPY_RECM) {
                        tcp_read_fraghdr(xprt, &desc);
                        continue;
                }
                /* Read in the xid if necessary */
                if (xprt->tcp_flags & XPRT_COPY_XID) {
                        tcp_read_xid(xprt, &desc);
                        continue;
                }
                /* Read in the request data */
                if (xprt->tcp_flags & XPRT_COPY_DATA) {
                        tcp_read_request(xprt, &desc);
                        continue;
                }
                /* Skip over any trailing bytes on short reads */
                tcp_read_discard(xprt, &desc);
        } while (desc.count && xprt_connected(xprt));
        dprintk("RPC:      tcp_data_recv done\n");
        return len - desc.count;
}

static void tcp_data_ready(struct sock *sk, int bytes)
{
        struct rpc_xprt *xprt;
        read_descriptor_t rd_desc;

        dprintk("RPC:      tcp_data_ready...\n");
        if (!(xprt = xprt_from_sock(sk))) {
                printk("RPC:      tcp_data_ready socket info not found!\n");
                return;
        }
        if (xprt->shutdown)
                return;

        /* We use rd_desc to pass struct xprt to tcp_data_recv */
        rd_desc.buf = (char *)xprt;
        rd_desc.count = 65536;
        tcp_read_sock(sk, &rd_desc, tcp_data_recv);
}

static void
tcp_state_change(struct sock *sk)
{
        struct rpc_xprt *xprt;

        if (!(xprt = xprt_from_sock(sk)))
                goto out;
        dprintk("RPC:      tcp_state_change client %p...\n", xprt);
        dprintk("RPC:      state %x conn %d dead %d zapped %d\n",
                                sk->state, xprt_connected(xprt),
                                sk->dead, sk->zapped);

        switch (sk->state) {
        case TCP_ESTABLISHED:
                if (xprt_test_and_set_connected(xprt))
                        break;

                /* Reset TCP record info */
                xprt->tcp_offset = 0;
                xprt->tcp_reclen = 0;
                xprt->tcp_copied = 0;
                xprt->tcp_flags = XPRT_COPY_RECM | XPRT_COPY_XID;

                spin_lock(&xprt->sock_lock);
                if (xprt->snd_task && xprt->snd_task->tk_rpcwait == &xprt->pending)
                        rpc_wake_up_task(xprt->snd_task);
                spin_unlock(&xprt->sock_lock);
                break;
        case TCP_SYN_SENT:
        case TCP_SYN_RECV:
                break;
        default:
                xprt_disconnect(xprt);
                break;
        }
 out:
        if (sk->sleep && waitqueue_active(sk->sleep))
                wake_up_interruptible_all(sk->sleep);
}

/*
 * Called when more output buffer space is available for this socket.
 * We try not to wake our writers until they can make "significant"
 * progress, otherwise we'll waste resources thrashing sock_sendmsg
 * with a bunch of small requests.
 */
static void
xprt_write_space(struct sock *sk)
{
        struct rpc_xprt *xprt;
        struct socket   *sock;

        if (!(xprt = xprt_from_sock(sk)) || !(sock = sk->socket))
                return;
        if (xprt->shutdown)
                return;

        /* Wait until we have enough socket memory */
        if (xprt->stream) {
                /* from net/ipv4/tcp.c:tcp_write_space */
                if (tcp_wspace(sk) < tcp_min_write_space(sk))
                        return;
        } else {
                /* from net/core/sock.c:sock_def_write_space */
                if (!sock_writeable(sk))
                        return;
        }

        if (!test_and_clear_bit(SOCK_NOSPACE, &sock->flags))
                return;

        spin_lock_bh(&xprt->sock_lock);
        if (xprt->snd_task && xprt->snd_task->tk_rpcwait == &xprt->pending)
                rpc_wake_up_task(xprt->snd_task);
        spin_unlock_bh(&xprt->sock_lock);
        if (sk->sleep && waitqueue_active(sk->sleep))
                wake_up_interruptible(sk->sleep);
}

/*
 * Exponential backoff for UDP retries
 */
static inline int
xprt_expbackoff(struct rpc_task *task, struct rpc_rqst *req)
{
        int backoff;

        req->rq_ntimeo++;
        backoff = min(rpc_ntimeo(&task->tk_client->cl_rtt), XPRT_MAX_BACKOFF);
        if (req->rq_ntimeo < (1 << backoff))
                return 1;
        return 0;
}

/*
 * RPC receive timeout handler.
 */
static void
xprt_timer(struct rpc_task *task)
{
        struct rpc_rqst *req = task->tk_rqstp;
        struct rpc_xprt *xprt = req->rq_xprt;

        spin_lock(&xprt->sock_lock);
        if (req->rq_received)
                goto out;

        if (!xprt->nocong) {
                if (xprt_expbackoff(task, req)) {
                        rpc_add_timer(task, xprt_timer);
                        goto out_unlock;
                }
                rpc_inc_timeo(&task->tk_client->cl_rtt);
                xprt_adjust_cwnd(req->rq_xprt, -ETIMEDOUT);
                __xprt_put_cong(xprt, req);
        }
        req->rq_nresend++;

        dprintk("RPC: %4d xprt_timer (%s request)\n",
                task->tk_pid, req ? "pending" : "backlogged");

        task->tk_status  = -ETIMEDOUT;
out:
        task->tk_timeout = 0;
        rpc_wake_up_task(task);
out_unlock:
        spin_unlock(&xprt->sock_lock);
}

/*
 * Place the actual RPC call.
 * We have to copy the iovec because sendmsg fiddles with its contents.
 */
void
xprt_transmit(struct rpc_task *task)
{
        struct rpc_rqst *req = task->tk_rqstp;
        struct rpc_xprt *xprt = req->rq_xprt;

        dprintk("RPC: %4d xprt_transmit(%x)\n", task->tk_pid, 
                                *(u32 *)(req->rq_svec[0].iov_base));

        if (xprt->shutdown)
                task->tk_status = -EIO;

        if (!xprt_connected(xprt))
                task->tk_status = -ENOTCONN;

        if (task->tk_status < 0)
                return;

        if (task->tk_rpcwait)
                rpc_remove_wait_queue(task);

        /* set up everything as needed. */
        /* Write the record marker */
        if (xprt->stream) {
                u32     *marker = req->rq_svec[0].iov_base;

                *marker = htonl(0x80000000|(req->rq_slen-sizeof(*marker)));
        }

        spin_lock_bh(&xprt->sock_lock);
        if (!__xprt_lock_write(xprt, task)) {
                spin_unlock_bh(&xprt->sock_lock);
                return;
        }
        if (list_empty(&req->rq_list)) {
                list_add_tail(&req->rq_list, &xprt->recv);
                req->rq_received = 0;
        }
        spin_unlock_bh(&xprt->sock_lock);

        do_xprt_transmit(task);
}

static void
do_xprt_transmit(struct rpc_task *task)
{
        struct rpc_clnt *clnt = task->tk_client;
        struct rpc_rqst *req = task->tk_rqstp;
        struct rpc_xprt *xprt = req->rq_xprt;
        int status, retry = 0;


        /* Continue transmitting the packet/record. We must be careful
         * to cope with writespace callbacks arriving _after_ we have
         * called xprt_sendmsg().
         */
        while (1) {
                req->rq_xtime = jiffies;
                status = xprt_sendmsg(xprt, req);

                if (status < 0)
                        break;

                if (xprt->stream) {
                        req->rq_bytes_sent += status;

                        if (req->rq_bytes_sent >= req->rq_slen)
                                goto out_receive;
                } else {
                        if (status >= req->rq_slen)
                                goto out_receive;
                        status = -EAGAIN;
                        break;
                }

                dprintk("RPC: %4d xmit incomplete (%d left of %d)\n",
                                task->tk_pid, req->rq_slen - req->rq_bytes_sent,
                                req->rq_slen);

                status = -EAGAIN;
                if (retry++ > 50)
                        break;
        }

        /* Note: at this point, task->tk_sleeping has not yet been set,
         *       hence there is no danger of the waking up task being put on
         *       schedq, and being picked up by a parallel run of rpciod().
         */
        if (req->rq_received)
                goto out_release;

        task->tk_status = status;

        switch (status) {
        case -EAGAIN:
                if (test_bit(SOCK_ASYNC_NOSPACE, &xprt->sock->flags)) {
                        /* Protect against races with xprt_write_space */
                        spin_lock_bh(&xprt->sock_lock);
                        if (test_bit(SOCK_NOSPACE, &xprt->sock->flags)) {
                                task->tk_timeout = req->rq_timeout.to_current;
                                rpc_sleep_on(&xprt->pending, task, NULL, NULL);
                        }
                        spin_unlock_bh(&xprt->sock_lock);
                        return;
                }
                /* Keep holding the socket if it is blocked */
                rpc_delay(task, HZ>>4);
                return;
        case -ECONNREFUSED:
        case -ENOTCONN:
                if (!xprt->stream) {
                        task->tk_timeout = RPC_REESTABLISH_TIMEOUT;
                        rpc_sleep_on(&xprt->sending, task, NULL, NULL);
                        return;
                }
                /* fall through */
        default:
                if (xprt->stream)
                        xprt_disconnect(xprt);
                req->rq_bytes_sent = 0;
        }
 out_release:
        spin_lock_bh(&xprt->sock_lock);
        __xprt_release_write(xprt, task);
        __xprt_put_cong(xprt, req);
        spin_unlock_bh(&xprt->sock_lock);
        return;
 out_receive:
        dprintk("RPC: %4d xmit complete\n", task->tk_pid);
        /* Set the task's receive timeout value */
        if (!xprt->nocong) {
                task->tk_timeout = rpc_calc_rto(&clnt->cl_rtt,
                                task->tk_msg.rpc_proc->p_timer);
                req->rq_ntimeo = 0;
                if (task->tk_timeout > req->rq_timeout.to_maxval)
                        task->tk_timeout = req->rq_timeout.to_maxval;
        } else
                task->tk_timeout = req->rq_timeout.to_current;
        spin_lock_bh(&xprt->sock_lock);
        if (!req->rq_received)
                rpc_sleep_on(&xprt->pending, task, NULL, xprt_timer);
        __xprt_release_write(xprt, task);
        spin_unlock_bh(&xprt->sock_lock);
}

/*
 * Reserve an RPC call slot.
 */
void
xprt_reserve(struct rpc_task *task)
{
        struct rpc_xprt *xprt = task->tk_xprt;

        task->tk_status = -EIO;
        if (!xprt->shutdown) {
                spin_lock(&xprt->xprt_lock);
                do_xprt_reserve(task);
                spin_unlock(&xprt->xprt_lock);
        }
}

static inline void
do_xprt_reserve(struct rpc_task *task)
{
        struct rpc_xprt *xprt = task->tk_xprt;

        task->tk_status = 0;
        if (task->tk_rqstp)
                return;
        if (xprt->free) {
                struct rpc_rqst *req = xprt->free;
                xprt->free = req->rq_next;
                req->rq_next = NULL;
                task->tk_rqstp = req;
                xprt_request_init(task, xprt);
                return;
        }
        dprintk("RPC:      waiting for request slot\n");
        task->tk_status = -EAGAIN;
        task->tk_timeout = 0;
        rpc_sleep_on(&xprt->backlog, task, NULL, NULL);
}

/*
 * Initialize RPC request
 */
static void
xprt_request_init(struct rpc_task *task, struct rpc_xprt *xprt)
{
        struct rpc_rqst *req = task->tk_rqstp;
        static u32      xid = 0;

        if (!xid)
                xid = get_seconds() << 12;

        dprintk("RPC: %4d reserved req %p xid %08x\n", task->tk_pid, req, xid);
        req->rq_timeout = xprt->timeout;
        req->rq_task    = task;
        req->rq_xprt    = xprt;
        req->rq_xid     = xid++;
        if (!xid)
                xid++;
        INIT_LIST_HEAD(&req->rq_list);
}

/*
 * Release an RPC call slot
 */
void
xprt_release(struct rpc_task *task)
{
        struct rpc_xprt *xprt = task->tk_xprt;
        struct rpc_rqst *req;

        if (!(req = task->tk_rqstp))
                return;
        spin_lock_bh(&xprt->sock_lock);
        __xprt_release_write(xprt, task);
        __xprt_put_cong(xprt, req);
        if (!list_empty(&req->rq_list))
                list_del(&req->rq_list);
        spin_unlock_bh(&xprt->sock_lock);
        task->tk_rqstp = NULL;
        memset(req, 0, sizeof(*req));   /* mark unused */

        dprintk("RPC: %4d release request %p\n", task->tk_pid, req);

        spin_lock(&xprt->xprt_lock);
        req->rq_next = xprt->free;
        xprt->free   = req;

        xprt_clear_backlog(xprt);
        spin_unlock(&xprt->xprt_lock);
}

/*
 * Set default timeout parameters
 */
void
xprt_default_timeout(struct rpc_timeout *to, int proto)
{
        if (proto == IPPROTO_UDP)
                xprt_set_timeout(to, 5,  5 * HZ);
        else
                xprt_set_timeout(to, 5, 60 * HZ);
}

/*
 * Set constant timeout
 */
void
xprt_set_timeout(struct rpc_timeout *to, unsigned int retr, unsigned long incr)
{
        to->to_current   = 
        to->to_initval   = 
        to->to_increment = incr;
        to->to_maxval    = incr * retr;
        to->to_retries   = retr;
        to->to_exponential = 0;
}

/*
 * Initialize an RPC client
 */
static struct rpc_xprt *
xprt_setup(int proto, struct sockaddr_in *ap, struct rpc_timeout *to)
{
        struct rpc_xprt *xprt;
        struct rpc_rqst *req;
        int             i;

        dprintk("RPC:      setting up %s transport...\n",
                                proto == IPPROTO_UDP? "UDP" : "TCP");

        if ((xprt = kmalloc(sizeof(struct rpc_xprt), GFP_KERNEL)) == NULL)
                return NULL;
        memset(xprt, 0, sizeof(*xprt)); /* Nnnngh! */

        xprt->addr = *ap;
        xprt->prot = proto;
        xprt->stream = (proto == IPPROTO_TCP)? 1 : 0;
        if (xprt->stream) {
                xprt->cwnd = RPC_MAXCWND;
                xprt->nocong = 1;
        } else
                xprt->cwnd = RPC_INITCWND;
        spin_lock_init(&xprt->sock_lock);
        spin_lock_init(&xprt->xprt_lock);
        init_waitqueue_head(&xprt->cong_wait);

        INIT_LIST_HEAD(&xprt->recv);

        /* Set timeout parameters */
        if (to) {
                xprt->timeout = *to;
                xprt->timeout.to_current = to->to_initval;
        } else
                xprt_default_timeout(&xprt->timeout, xprt->prot);

        INIT_RPC_WAITQ(&xprt->pending, "xprt_pending");
        INIT_RPC_WAITQ(&xprt->sending, "xprt_sending");
        INIT_RPC_WAITQ(&xprt->resend, "xprt_resend");
        INIT_RPC_WAITQ(&xprt->backlog, "xprt_backlog");

        /* initialize free list */
        for (i = 0, req = xprt->slot; i < RPC_MAXREQS-1; i++, req++)
                req->rq_next = req + 1;
        req->rq_next = NULL;
        xprt->free = xprt->slot;

        dprintk("RPC:      created transport %p\n", xprt);
        
        return xprt;
}

/*
 * Bind to a reserved port
 */
static inline int
xprt_bindresvport(struct socket *sock)
{
        struct sockaddr_in myaddr;
        int             err, port;

        memset(&myaddr, 0, sizeof(myaddr));
        myaddr.sin_family = AF_INET;
        port = 800;
        do {
                myaddr.sin_port = htons(port);
                err = sock->ops->bind(sock, (struct sockaddr *) &myaddr,
                                                sizeof(myaddr));
        } while (err == -EADDRINUSE && --port > 0);

        if (err < 0)
                printk("RPC: Can't bind to reserved port (%d).\n", -err);

        return err;
}

static void
xprt_bind_socket(struct rpc_xprt *xprt, struct socket *sock)
{
        struct sock     *sk = sock->sk;

        if (xprt->inet)
                return;

        sk->user_data = xprt;
        xprt->old_data_ready = sk->data_ready;
        xprt->old_state_change = sk->state_change;
        xprt->old_write_space = sk->write_space;
        if (xprt->prot == IPPROTO_UDP) {
                sk->data_ready = udp_data_ready;
                sk->no_check = UDP_CSUM_NORCV;
                xprt_set_connected(xprt);
        } else {
                struct tcp_opt *tp = tcp_sk(sk);
                tp->nonagle = 1;        /* disable Nagle's algorithm */
                sk->data_ready = tcp_data_ready;
                sk->state_change = tcp_state_change;
                xprt_clear_connected(xprt);
        }
        sk->write_space = xprt_write_space;

        /* Reset to new socket */
        xprt->sock = sock;
        xprt->inet = sk;

        return;
}

/*
 * Set socket buffer length
 */
void
xprt_sock_setbufsize(struct rpc_xprt *xprt)
{
        struct sock *sk = xprt->inet;

        if (xprt->stream)
                return;
        if (xprt->rcvsize) {
                sk->userlocks |= SOCK_RCVBUF_LOCK;
                sk->rcvbuf = xprt->rcvsize * RPC_MAXCONG * 2;
        }
        if (xprt->sndsize) {
                sk->userlocks |= SOCK_SNDBUF_LOCK;
                sk->sndbuf = xprt->sndsize * RPC_MAXCONG * 2;
                sk->write_space(sk);
        }
}

/*
 * Datastream sockets are created here, but xprt_connect will create
 * and connect stream sockets.
 */
static struct socket *
xprt_create_socket(int proto, struct rpc_timeout *to, int resvport)
{
        struct socket   *sock;
        int             type, err;

        dprintk("RPC:      xprt_create_socket(%s %d)\n",
                           (proto == IPPROTO_UDP)? "udp" : "tcp", proto);

        type = (proto == IPPROTO_UDP)? SOCK_DGRAM : SOCK_STREAM;

        if ((err = sock_create(PF_INET, type, proto, &sock)) < 0) {
                printk("RPC: can't create socket (%d).\n", -err);
                goto failed;
        }

        /* If the caller has the capability, bind to a reserved port */
        if (resvport && xprt_bindresvport(sock) < 0) {
                printk("RPC: can't bind to reserved port.\n");
                goto failed;
        }

        return sock;

failed:
        sock_release(sock);
        return NULL;
}

/*
 * Create an RPC client transport given the protocol and peer address.
 */
struct rpc_xprt *
xprt_create_proto(int proto, struct sockaddr_in *sap, struct rpc_timeout *to)
{
        struct rpc_xprt *xprt;

        xprt = xprt_setup(proto, sap, to);
        if (!xprt)
                goto out_bad;

        xprt->resvport = capable(CAP_NET_BIND_SERVICE) ? 1 : 0;
        if (!xprt->stream) {
                struct socket *sock;

                sock = xprt_create_socket(proto, to, xprt->resvport);
                if (!sock)
                        goto out_bad;
                xprt_bind_socket(xprt, sock);
        }

        dprintk("RPC:      xprt_create_proto created xprt %p\n", xprt);
        return xprt;
 out_bad:
        dprintk("RPC:      xprt_create_proto failed\n");
        if (xprt)
                kfree(xprt);
        return NULL;
}

/*
 * Prepare for transport shutdown.
 */
void
xprt_shutdown(struct rpc_xprt *xprt)
{
        xprt->shutdown = 1;
        rpc_wake_up(&xprt->sending);
        rpc_wake_up(&xprt->resend);
        rpc_wake_up(&xprt->pending);
        rpc_wake_up(&xprt->backlog);
        if (waitqueue_active(&xprt->cong_wait))
                wake_up(&xprt->cong_wait);
}

/*
 * Clear the xprt backlog queue
 */
int
xprt_clear_backlog(struct rpc_xprt *xprt) {
        rpc_wake_up_next(&xprt->backlog);
        if (waitqueue_active(&xprt->cong_wait))
                wake_up(&xprt->cong_wait);
        return 1;
}

/*
 * Destroy an RPC transport, killing off all requests.
 */
int
xprt_destroy(struct rpc_xprt *xprt)
{
        dprintk("RPC:      destroying transport %p\n", xprt);
        xprt_shutdown(xprt);
        xprt_close(xprt);
        kfree(xprt);

        return 0;
}