Import 2.4.0-test2pre7

[davej-history.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/malloc.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/unistd.h>
#include <linux/sunrpc/clnt.h>
#include <linux/file.h>

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

#include <asm/uaccess.h>

/* Following value should be > 32k + RPC overhead */
#define XPRT_MIN_WRITE_SPACE 35000

extern spinlock_t rpc_queue_lock;

/*
 * Local variables
 */

/* Spinlock for critical sections in the code. */
spinlock_t xprt_sock_lock = SPIN_LOCK_UNLOCKED;
spinlock_t xprt_lock = SPIN_LOCK_UNLOCKED;

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

#ifndef MAX
# define MAX(a, b)      ((a) > (b)? (a) : (b))
# define MIN(a, b)      ((a) < (b)? (a) : (b))
#endif

/*
 * Local functions
 */
static void     xprt_request_init(struct rpc_task *, struct rpc_xprt *);
static void     do_xprt_transmit(struct rpc_task *);
static void     xprt_reserve_status(struct rpc_task *task);
static void     xprt_disconnect(struct rpc_xprt *);
static void     xprt_reconn_status(struct rpc_task *task);
static struct socket *xprt_create_socket(int, struct rpc_timeout *);
static int      xprt_bind_socket(struct rpc_xprt *, struct socket *);
static void     xprt_remove_pending(struct rpc_xprt *);

#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;
}

/*
 *      Adjust the iovec to move on 'n' bytes
 */
 
extern inline void
xprt_move_iov(struct msghdr *msg, struct iovec *niv, unsigned amount)
{
        struct iovec *iv=msg->msg_iov;
        int i;
        
        /*
         *      Eat any sent iovecs
         */
        while (iv->iov_len <= amount) {
                amount -= iv->iov_len;
                iv++;
                msg->msg_iovlen--;
        }

        /*
         *      And chew down the partial one
         */
        niv[0].iov_len = iv->iov_len-amount;
        niv[0].iov_base =((unsigned char *)iv->iov_base)+amount;
        iv++;

        /*
         *      And copy any others
         */
        for(i = 1; i < msg->msg_iovlen; i++)
                niv[i]=*iv++;

        msg->msg_iov=niv;
}
 
/*
 * 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;
        mm_segment_t    oldfs;
        int             result;
        int             slen = req->rq_slen - req->rq_bytes_sent;
        struct iovec    niv[MAX_IOVEC];

        if (slen <= 0)
                return 0;

        if (!sock)
                return -ENOTCONN;

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

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

        /* Dont repeat bytes */
        if (req->rq_bytes_sent)
                xprt_move_iov(&msg, niv, req->rq_bytes_sent);

        oldfs = get_fs(); set_fs(get_ds());
        result = sock_sendmsg(sock, &msg, slen);
        set_fs(oldfs);

        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.
                 */
                break;
        case -EAGAIN:
                if (test_bit(SOCK_NOSPACE, &sock->flags))
                        result = -ENOMEM;
                break;
        case -ENOTCONN:
        case -EPIPE:
                /* connection broken */
                if (xprt->stream)
                        result = -ENOTCONN;
                break;
        default:
                printk(KERN_NOTICE "RPC: sendmsg returned error %d\n", -result);
                result = 0;
        }
        return result;
}

/*
 * Read data from socket
 */
static int
xprt_recvmsg(struct rpc_xprt *xprt, struct iovec *iov, int nr, unsigned len, unsigned shift)
{
        struct socket   *sock = xprt->sock;
        struct msghdr   msg;
        mm_segment_t    oldfs;
        struct iovec    niv[MAX_IOVEC];
        int             result;

        if (!sock)
                return -ENOTCONN;

        msg.msg_flags   = MSG_DONTWAIT|MSG_NOSIGNAL;
        msg.msg_iov     = iov;
        msg.msg_iovlen  = nr;
        msg.msg_name    = NULL;
        msg.msg_namelen = 0;
        msg.msg_control = NULL;
        msg.msg_controllen = 0;

        /* Adjust the iovec if we've already filled it */
        if (shift)
                xprt_move_iov(&msg, niv, shift);

        oldfs = get_fs(); set_fs(get_ds());
        result = sock_recvmsg(sock, &msg, len, MSG_DONTWAIT);
        set_fs(oldfs);

        dprintk("RPC:      xprt_recvmsg(iov %p, len %d) = %d\n",
                                                iov, len, result);
        return result;
}


/*
 * 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 = xprt->cwnd;

        spin_lock_bh(&xprt_sock_lock);
        if (xprt->nocong)
                goto out;
        if (result >= 0) {
                if (xprt->cong < cwnd || time_before(jiffies, xprt->congtime))
                        goto out;
                /* 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;
                else
                        pprintk("RPC: %lu %ld cwnd\n", jiffies, cwnd);
                xprt->congtime = jiffies + ((cwnd * HZ) << 2) / RPC_CWNDSCALE;
                dprintk("RPC:      cong %08lx, cwnd was %08lx, now %08lx, "
                        "time %ld ms\n", xprt->cong, xprt->cwnd, cwnd,
                        (xprt->congtime-jiffies)*1000/HZ);
        } else if (result == -ETIMEDOUT) {
                if ((cwnd >>= 1) < RPC_CWNDSCALE)
                        cwnd = RPC_CWNDSCALE;
                xprt->congtime = jiffies + ((cwnd * HZ) << 3) / RPC_CWNDSCALE;
                dprintk("RPC:      cong %ld, cwnd was %ld, now %ld, "
                        "time %ld ms\n", xprt->cong, xprt->cwnd, cwnd,
                        (xprt->congtime-jiffies)*1000/HZ);
                pprintk("RPC: %lu %ld cwnd\n", jiffies, cwnd);
        }

        xprt->cwnd = cwnd;
 out:
        spin_unlock_bh(&xprt_sock_lock);
}

/*
 * 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);
        /*
         *      TCP doesnt require the rpciod now - other things may
         *      but rpciod handles that not us.
         */
        if(xprt->stream)
                rpciod_down();
}

/*
 * Mark a transport as disconnected
 */
static void
xprt_disconnect(struct rpc_xprt *xprt)
{
        dprintk("RPC:      disconnected transport %p\n", xprt);
        xprt->connected = 0;
        xprt->tcp_offset = 0;
        xprt->tcp_copied = 0;
        xprt->tcp_more = 0;
        xprt_remove_pending(xprt);
        rpc_wake_up_status(&xprt->pending, -ENOTCONN);
}

/*
 * Reconnect a broken TCP connection.
 */
void
xprt_reconnect(struct rpc_task *task)
{
        struct rpc_xprt *xprt = task->tk_xprt;
        struct socket   *sock = xprt->sock;
        struct sock     *inet = xprt->inet;
        int             status;

        dprintk("RPC: %4d xprt_reconnect %p connected %d\n",
                                task->tk_pid, xprt, xprt->connected);
        if (xprt->shutdown)
                return;

        if (!xprt->stream)
                return;

        if (!xprt->addr.sin_port) {
                task->tk_status = -EIO;
                return;
        }

        spin_lock(&xprt_lock);
        if (xprt->connecting) {
                task->tk_timeout = 0;
                rpc_sleep_on(&xprt->reconn, task, NULL, NULL);
                spin_unlock(&xprt_lock);
                return;
        }
        xprt->connecting = 1;
        spin_unlock(&xprt_lock);

        status = -ENOTCONN;
        if (!inet) {
                /* Create an unconnected socket */
                if (!(sock = xprt_create_socket(xprt->prot, &xprt->timeout)))
                        goto defer;
                xprt_bind_socket(xprt, sock);
                inet = sock->sk;
        }

        xprt_disconnect(xprt);

        /* Now connect it asynchronously. */
        dprintk("RPC: %4d connecting new socket\n", task->tk_pid);
        status = sock->ops->connect(sock, (struct sockaddr *) &xprt->addr,
                                sizeof(xprt->addr), O_NONBLOCK);

        if (status < 0) {
                switch (status) {
                case -EALREADY:
                case -EINPROGRESS:
                        status = 0;
                        break;
                case -EISCONN:
                case -EPIPE:
                        status = 0;
                        xprt_close(xprt);
                        goto defer;
                default:
                        printk("RPC: TCP connect error %d!\n", -status);
                        xprt_close(xprt);
                        goto defer;
                }

                dprintk("RPC: %4d connect status %d connected %d\n",
                                task->tk_pid, status, xprt->connected);

                spin_lock_bh(&xprt_sock_lock);
                if (!xprt->connected) {
                        task->tk_timeout = xprt->timeout.to_maxval;
                        rpc_sleep_on(&xprt->reconn, task, xprt_reconn_status, NULL);
                        spin_unlock_bh(&xprt_sock_lock);
                        return;
                }
                spin_unlock_bh(&xprt_sock_lock);
        }
defer:
        spin_lock(&xprt_lock);
        xprt->connecting = 0;
        if (status < 0) {
                rpc_delay(task, 5*HZ);
                task->tk_status = -ENOTCONN;
        }
        rpc_wake_up(&xprt->reconn);
        spin_unlock(&xprt_lock);
}

/*
 * Reconnect timeout. We just mark the transport as not being in the
 * process of reconnecting, and leave the rest to the upper layers.
 */
static void
xprt_reconn_status(struct rpc_task *task)
{
        struct rpc_xprt *xprt = task->tk_xprt;

        dprintk("RPC: %4d xprt_reconn_timeout %d\n",
                                task->tk_pid, task->tk_status);

        spin_lock(&xprt_lock);
        xprt->connecting = 0;
        rpc_wake_up(&xprt->reconn);
        spin_unlock(&xprt_lock);
}

/*
 * 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 rpc_task *head, *task;
        struct rpc_rqst *req;
        int             safe = 0;

        spin_lock_bh(&rpc_queue_lock);
        if ((head = xprt->pending.task) != NULL) {
                task = head;
                do {
                        if ((req = task->tk_rqstp) && req->rq_xid == xid)
                                goto out;
                        task = task->tk_next;
                        if (++safe > 100) {
                                printk("xprt_lookup_rqst: loop in Q!\n");
                                goto out_bad;
                        }
                } while (task != head);
        }
        dprintk("RPC:      unknown XID %08x in reply.\n", xid);
 out_bad:
        req = NULL;
 out:
        if (req && !rpc_lock_task(req->rq_task))
                req = NULL;
        spin_unlock_bh(&rpc_queue_lock);
        return req;
}

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

        /* Adjust congestion window */
        xprt_adjust_cwnd(xprt, copied);

#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);
        task->tk_status = copied;

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

/*
 * 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
 */
static int csum_partial_copy_to_page_cache(struct iovec *iov,
                                           struct sk_buff *skb,
                                           int copied)
{
        __u8 *pkt_data = skb->data + sizeof(struct udphdr);
        __u8 *cur_ptr = iov->iov_base;
        __kernel_size_t cur_len = iov->iov_len;
        unsigned int csum = skb->csum;
        int need_csum = (skb->ip_summed != CHECKSUM_UNNECESSARY);
        int slack = skb->len - copied - sizeof(struct udphdr);

        if (need_csum)
                csum = csum_partial(skb->h.raw, sizeof(struct udphdr), csum);
        while (copied > 0) {
                if (cur_len) {
                        int to_move = cur_len;
                        if (to_move > copied)
                                to_move = copied;
                        if (need_csum)
                                csum = csum_partial_copy_nocheck(pkt_data, cur_ptr,
                                                                 to_move, csum);
                        else
                                memcpy(cur_ptr, pkt_data, to_move);
                        pkt_data += to_move;
                        copied -= to_move;
                        cur_ptr += to_move;
                        cur_len -= to_move;
                }
                if (cur_len <= 0) {
                        iov++;
                        cur_len = iov->iov_len;
                        cur_ptr = iov->iov_base;
                }
        }
        if (need_csum) {
                if (slack > 0)
                        csum = csum_partial(pkt_data, slack, csum);
                if ((unsigned short)csum_fold(csum))
                        return -1;
        }
        return 0;
}

/*
 * Input handler for RPC replies. Called from a bottom half and hence
 * atomic.
 */
static inline 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");
                return;
        }

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

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

        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 */
        rovr = xprt_lookup_rqst(xprt, *(u32 *) (skb->h.raw + sizeof(struct udphdr)));
        if (!rovr)
                goto dropit;
        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;

        rovr->rq_damaged  = 1;
        /* Suck it into the iovec, verify checksum if not done by hw. */
        if (csum_partial_copy_to_page_cache(rovr->rq_rvec, skb, copied))
                goto out_unlock;

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

        xprt_complete_rqst(xprt, rovr, copied);

 out_unlock:
        rpc_unlock_task(task);

 dropit:
        skb_free_datagram(sk, skb);
}

/*
 * TCP read fragment marker
 */
static inline int
tcp_read_fraghdr(struct rpc_xprt *xprt)
{
        struct iovec    riov;
        int             want, result;

        if (xprt->tcp_offset >= xprt->tcp_reclen + sizeof(xprt->tcp_recm)) {
                xprt->tcp_offset = 0;
                xprt->tcp_reclen = 0;
        }
        if (xprt->tcp_offset >= sizeof(xprt->tcp_recm))
                goto done;

        want = sizeof(xprt->tcp_recm) - xprt->tcp_offset;
        dprintk("RPC:      reading header (%d bytes)\n", want);
        do {
                riov.iov_base = ((u8*) &xprt->tcp_recm) + xprt->tcp_offset;
                riov.iov_len  = want;
                result = xprt_recvmsg(xprt, &riov, 1, want, 0);
                if (result < 0)
                        return result;
                xprt->tcp_offset += result;
                want -= result;
        } while (want);

        /* Is this another fragment in the last message */
        if (!xprt->tcp_more)
                xprt->tcp_copied = 0; /* No, so we're reading a new message */

        /* Get the record length and mask out the last fragment bit */
        xprt->tcp_reclen = ntohl(xprt->tcp_recm);
        xprt->tcp_more = (xprt->tcp_reclen & 0x80000000) ? 0 : 1;
        xprt->tcp_reclen &= 0x7fffffff;

        dprintk("RPC:      New record reclen %d morefrags %d\n",
                                   xprt->tcp_reclen, xprt->tcp_more);
 done:
        return xprt->tcp_reclen + sizeof(xprt->tcp_recm) - xprt->tcp_offset;
}

/*
 * TCP read xid
 */
static inline int
tcp_read_xid(struct rpc_xprt *xprt, int avail)
{
        struct iovec    riov;
        int             want, result;

        if (xprt->tcp_copied >= sizeof(xprt->tcp_xid) || !avail)
                goto done;
        want = MIN(sizeof(xprt->tcp_xid) - xprt->tcp_copied, avail);
        do {
                dprintk("RPC:      reading xid (%d bytes)\n", want);
                riov.iov_base = ((u8*) &xprt->tcp_xid) + xprt->tcp_copied;
                riov.iov_len  = want;
                result = xprt_recvmsg(xprt, &riov, 1, want, 0);
                if (result < 0)
                        return result;
                xprt->tcp_copied += result;
                xprt->tcp_offset += result;
                want  -= result;
                avail -= result;
        } while (want);
 done:
        return avail;
}

/*
 * TCP read and complete request
 */
static inline int
tcp_read_request(struct rpc_xprt *xprt, struct rpc_rqst *req, int avail)
{
        int     want, result;

        if (req->rq_rlen <= xprt->tcp_copied || !avail)
                goto done;
        want = MIN(req->rq_rlen - xprt->tcp_copied, avail);
        do {
                dprintk("RPC: %4d TCP receiving %d bytes\n",
                        req->rq_task->tk_pid, want);

                result = xprt_recvmsg(xprt, req->rq_rvec, req->rq_rnr, want, xprt->tcp_copied);
                if (result < 0)
                        return result;
                xprt->tcp_copied += result;
                xprt->tcp_offset += result;
                avail  -= result;
                want   -= result;
        } while (want);

 done:
        if (req->rq_rlen > xprt->tcp_copied && xprt->tcp_more)
                return avail;
        dprintk("RPC: %4d received reply complete\n", req->rq_task->tk_pid);
        xprt_complete_rqst(xprt, req, xprt->tcp_copied);

        return avail;
}

/*
 * TCP discard extra bytes from a short read
 */
static inline int
tcp_read_discard(struct rpc_xprt *xprt, int avail)
{
        struct iovec    riov;
        static u8       dummy[64];
        int             want, result = 0;

        while (avail) {
                want = MIN(avail, sizeof(dummy));
                riov.iov_base = dummy;
                riov.iov_len  = want;
                dprintk("RPC:      TCP skipping %d bytes\n", want);
                result = xprt_recvmsg(xprt, &riov, 1, want, 0);
                if (result < 0)
                        return result;
                xprt->tcp_offset += result;
                avail  -= result;
        }
        return avail;
}

/*
 * TCP record receive routine
 * This is not the most efficient code since we call recvfrom thrice--
 * first receiving the record marker, then the XID, then the data.
 * 
 * The optimal solution would be a RPC support in the TCP layer, which
 * would gather all data up to the next record marker and then pass us
 * the list of all TCP segments ready to be copied.
 */
static int
tcp_input_record(struct rpc_xprt *xprt)
{
        struct rpc_rqst *req = NULL;
        struct rpc_task *task = NULL;
        int             avail, result;

        dprintk("RPC:      tcp_input_record\n");

        if (xprt->shutdown)
                return -EIO;
        if (!xprt->connected)
                return -ENOTCONN;

        /* Read in a new fragment marker if necessary */
        /* Can we ever really expect to get completely empty fragments? */
        if ((result = tcp_read_fraghdr(xprt)) <= 0)
                return result;
        avail = result;

        /* Read in the xid if necessary */
        if ((result = tcp_read_xid(xprt, avail)) <= 0)
                return result;
        avail = result;

        /* Find and lock the request corresponding to this xid */
        req = xprt_lookup_rqst(xprt, xprt->tcp_xid);
        if (req) {
                task = req->rq_task;
                if (xprt->tcp_copied == sizeof(xprt->tcp_xid) || req->rq_damaged) {
                        req->rq_damaged = 1;
                        /* Read in the request data */
                        result = tcp_read_request(xprt,  req, avail);
                }
                rpc_unlock_task(task);
                if (result < 0)
                        return result;
                avail = result;
        }

        /* Skip over any trailing bytes on short reads */
        if ((result = tcp_read_discard(xprt, avail)) < 0)
                return result;

        dprintk("RPC:      tcp_input_record done (off %d reclen %d copied %d)\n",
                        xprt->tcp_offset, xprt->tcp_reclen, xprt->tcp_copied);
        result = xprt->tcp_reclen;
        return result;
}

/*
 *      TCP task queue stuff
 */
LIST_HEAD(rpc_xprt_pending);    /* List of xprts having pending tcp requests */

static inline
void tcp_rpciod_queue(void)
{
        rpciod_wake_up();
}

static inline
void xprt_append_pending(struct rpc_xprt *xprt)
{
        if (!list_empty(&xprt->rx_pending))
                return;
        spin_lock_bh(&rpc_queue_lock);
        if (list_empty(&xprt->rx_pending)) {
                list_add(&xprt->rx_pending, rpc_xprt_pending.prev);
                dprintk("RPC:     xprt queue %p\n", xprt);
                tcp_rpciod_queue();
        }
        spin_unlock_bh(&rpc_queue_lock);
}

static
void xprt_remove_pending(struct rpc_xprt *xprt)
{
        spin_lock_bh(&rpc_queue_lock);
        if (!list_empty(&xprt->rx_pending)) {
                list_del(&xprt->rx_pending);
                INIT_LIST_HEAD(&xprt->rx_pending);
        }
        spin_unlock_bh(&rpc_queue_lock);
}

static inline
struct rpc_xprt *xprt_remove_pending_next(void)
{
        struct rpc_xprt *xprt = NULL;

        spin_lock_bh(&rpc_queue_lock);
        if (!list_empty(&rpc_xprt_pending)) {
                xprt = list_entry(rpc_xprt_pending.next, struct rpc_xprt, rx_pending);
                list_del(&xprt->rx_pending);
                INIT_LIST_HEAD(&xprt->rx_pending);
        }
        spin_unlock_bh(&rpc_queue_lock);
        return xprt;
}

/*
 *      This is protected from tcp_data_ready and the stack as its run
 *      inside of the RPC I/O daemon
 */
void
__rpciod_tcp_dispatcher(void)
{
        struct rpc_xprt *xprt;
        int safe_retry = 0, result;

        dprintk("rpciod_tcp_dispatcher: Queue Running\n");

        /*
         *      Empty each pending socket
         */
        while ((xprt = xprt_remove_pending_next()) != NULL) {
                dprintk("rpciod_tcp_dispatcher: Processing %p\n", xprt);

                do {
                        result = tcp_input_record(xprt);
                } while (result >= 0);

                if (safe_retry++ > 200) {
                        schedule();
                        safe_retry = 0;
                }
        }
}

/*
 *      data_ready callback for TCP. We can't just jump into the
 *      tcp recvmsg functions inside of the network receive bh or
 *      bad things occur. We queue it to pick up after networking
 *      is done.
 */
 
static void tcp_data_ready(struct sock *sk, int len)
{
        struct rpc_xprt *xprt;

        dprintk("RPC:      tcp_data_ready...\n");
        if (!(xprt = xprt_from_sock(sk)))
        {
                printk("Not a socket with xprt %p\n", sk);
                return;
        }

        if (xprt->shutdown)
                return;

        xprt_append_pending(xprt);

        dprintk("RPC:      tcp_data_ready client %p\n", xprt);
        dprintk("RPC:      state %x conn %d dead %d zapped %d\n",
                                sk->state, xprt->connected,
                                sk->dead, sk->zapped);
}


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

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

        spin_lock_bh(&xprt_sock_lock);
        switch (sk->state) {
        case TCP_ESTABLISHED:
                xprt->connected = 1;
                if (xprt->snd_task && xprt->snd_task->tk_rpcwait == &xprt->sending)
                        rpc_wake_up_task(xprt->snd_task);
                rpc_wake_up(&xprt->reconn);
                break;
        default:
                xprt->connected = 0;
                rpc_wake_up_status(&xprt->pending, -ENOTCONN);
                break;
        }
        spin_unlock_bh(&xprt_sock_lock);
}

/*
 * The following 2 routines allow a task to sleep while socket memory is
 * low.
 */
static void
tcp_write_space(struct sock *sk)
{
        struct rpc_xprt *xprt;

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

        /* Wait until we have enough socket memory */
        if (sock_wspace(sk) < min(sk->sndbuf,XPRT_MIN_WRITE_SPACE))
                return;

        spin_lock_bh(&xprt_sock_lock);
        if (xprt->write_space)
                goto out_unlock;

        xprt->write_space = 1;

        if (xprt->snd_task && xprt->snd_task->tk_rpcwait == &xprt->sending)
                rpc_wake_up_task(xprt->snd_task);
 out_unlock:
        spin_unlock_bh(&xprt_sock_lock);
}

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

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


        /* Wait until we have enough socket memory */
        if (sock_wspace(sk) < min(sk->sndbuf,XPRT_MIN_WRITE_SPACE))
                return;

        spin_lock_bh(&xprt_sock_lock);
        if (xprt->write_space)
                goto out_unlock;

        xprt->write_space = 1;

        if (xprt->snd_task && xprt->snd_task->tk_rpcwait == &xprt->sending)
                rpc_wake_up_task(xprt->snd_task);
 out_unlock:
        spin_unlock_bh(&xprt_sock_lock);
}

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

        if (req)
                xprt_adjust_cwnd(task->tk_xprt, -ETIMEDOUT);

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

        task->tk_status  = -ETIMEDOUT;
        task->tk_timeout = 0;
        rpc_wake_up_task(task);
}


/*
 * Serialize access to sockets, in order to prevent different
 * requests from interfering with each other.
 */
static int
xprt_down_transmit(struct rpc_task *task)
{
        struct rpc_xprt *xprt = task->tk_rqstp->rq_xprt;
        struct rpc_rqst *req = task->tk_rqstp;

        spin_lock(&xprt_lock);
        if (xprt->snd_task && xprt->snd_task != task) {
                dprintk("RPC: %4d TCP write queue full (task %d)\n",
                        task->tk_pid, xprt->snd_task->tk_pid);
                task->tk_timeout = 0;
                task->tk_status = -EAGAIN;
                rpc_sleep_on(&xprt->sending, task, NULL, NULL);
        } else if (!xprt->snd_task) {
                xprt->snd_task = task;
#ifdef RPC_PROFILE
                req->rq_xtime = jiffies;
#endif
                req->rq_bytes_sent = 0;
        }
        spin_unlock(&xprt_lock);
        return xprt->snd_task == task;
}

/*
 * Releases the socket for use by other requests.
 */
static inline void
xprt_up_transmit(struct rpc_task *task)
{
        struct rpc_xprt *xprt = task->tk_rqstp->rq_xprt;

        if (xprt->snd_task && xprt->snd_task == task) {
                spin_lock(&xprt_lock);
                xprt->snd_task = NULL;
                rpc_wake_up_next(&xprt->sending);
                spin_unlock(&xprt_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)
                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)));
        }

        if (!xprt_down_transmit(task))
                return;

        do_xprt_transmit(task);
}

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


        /* For fast networks/servers we have to put the request on
         * the pending list now:
         * Note that we don't want the task timing out during the
         * call to xprt_sendmsg(), so we initially disable the timeout,
         * and then reset it later...
         */
        xprt_receive(task);

        /* Continue transmitting the packet/record. We must be careful
         * to cope with writespace callbacks arriving _after_ we have
         * called xprt_sendmsg().
         */
        while (1) {
                xprt->write_space = 0;
                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 = -ENOMEM;
                        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;
        }
        rpc_unlock_task(task);

        task->tk_status = status;

        /* 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().
         */
        rpc_wake_up_task(task);
        if (!RPC_IS_RUNNING(task))
                goto out_release;

        switch (status) {
        case -ENOMEM:
                /* Protect against (udp|tcp)_write_space */
                task->tk_timeout = req->rq_timeout.to_current;
                spin_lock_bh(&xprt_sock_lock);
                if (!xprt->write_space)
                        rpc_sleep_on(&xprt->sending, task, NULL, NULL);
                spin_unlock_bh(&xprt_sock_lock);
                return;
        case -EAGAIN:
                /* Keep holding the socket if it is blocked */
                rpc_delay(task, HZ>>4);
                return;
        case -ECONNREFUSED:
        case -ENOTCONN:
                if (!xprt->stream)
                        return;
        default:
                goto out_release;
        }

 out_receive:
        dprintk("RPC: %4d xmit complete\n", task->tk_pid);
        /* Set the task's receive timeout value */
        task->tk_timeout = req->rq_timeout.to_current;
        rpc_add_timer(task, xprt_timer);
        rpc_unlock_task(task);
 out_release:
        xprt_up_transmit(task);
}

/*
 * Queue the task for a reply to our call.
 * When the callback is invoked, the congestion window should have
 * been updated already.
 */
void
xprt_receive(struct rpc_task *task)
{
        struct rpc_rqst *req = task->tk_rqstp;
        struct rpc_xprt *xprt = req->rq_xprt;

        dprintk("RPC: %4d xprt_receive\n", task->tk_pid);

        task->tk_timeout = 0;
        rpc_sleep_locked(&xprt->pending, task, NULL, NULL);
}

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

        /* We already have an initialized request. */
        if (task->tk_rqstp)
                return 0;

        dprintk("RPC: %4d xprt_reserve cong = %ld cwnd = %ld\n",
                                task->tk_pid, xprt->cong, xprt->cwnd);
        spin_lock_bh(&xprt_sock_lock);
        xprt_reserve_status(task);
        if (task->tk_rqstp) {
                task->tk_timeout = 0;
        } else if (!task->tk_timeout) {
                task->tk_status = -ENOBUFS;
        } else {
                dprintk("RPC:      xprt_reserve waiting on backlog\n");
                task->tk_status = -EAGAIN;
                rpc_sleep_on(&xprt->backlog, task, NULL, NULL);
        }
        spin_unlock_bh(&xprt_sock_lock);
        dprintk("RPC: %4d xprt_reserve returns %d\n",
                                task->tk_pid, task->tk_status);
        return task->tk_status;
}

/*
 * Reservation callback
 */
static void
xprt_reserve_status(struct rpc_task *task)
{
        struct rpc_xprt *xprt = task->tk_xprt;
        struct rpc_rqst *req;

        if (xprt->shutdown) {
                task->tk_status = -EIO;
        } else if (task->tk_status < 0) {
                /* NOP */
        } else if (task->tk_rqstp) {
                /* We've already been given a request slot: NOP */
        } else {
                if (RPCXPRT_CONGESTED(xprt) || !(req = xprt->free))
                        goto out_nofree;
                /* OK: There's room for us. Grab a free slot and bump
                 * congestion value */
                xprt->free     = req->rq_next;
                req->rq_next   = NULL;
                xprt->cong    += RPC_CWNDSCALE;
                task->tk_rqstp = req;
                xprt_request_init(task, xprt);

                if (xprt->free)
                        xprt_clear_backlog(xprt);
        }

        return;

out_nofree:
        task->tk_status = -EAGAIN;
}

/*
 * 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 = CURRENT_TIME << 12;

        dprintk("RPC: %4d reserved req %p xid %08x\n", task->tk_pid, req, xid);
        task->tk_status = 0;
        req->rq_timeout = xprt->timeout;
        req->rq_task    = task;
        req->rq_xprt    = xprt;
        req->rq_xid     = xid++;
        if (!xid)
                xid++;
}

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

        xprt_up_transmit(task);
        if (!(req = task->tk_rqstp))
                return;
        task->tk_rqstp = NULL;
        memset(req, 0, sizeof(*req));   /* mark unused */

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

        /* remove slot from queue of pending */
        if (task->tk_rpcwait) {
                printk("RPC: task of released request still queued!\n");
                rpc_remove_wait_queue(task);
        }

        spin_lock_bh(&xprt_sock_lock);
        req->rq_next = xprt->free;
        xprt->free   = req;

        /* Decrease congestion value. */
        xprt->cong -= RPC_CWNDSCALE;

        xprt_clear_backlog(xprt);
        spin_unlock_bh(&xprt_sock_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_resrvval  = incr * retr;
        to->to_retries   = retr;
        to->to_exponential = 0;
}

/*
 * Initialize an RPC client
 */
static struct rpc_xprt *
xprt_setup(struct socket *sock, 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;
        xprt->congtime = jiffies;
        init_waitqueue_head(&xprt->cong_wait);

        /* Set timeout parameters */
        if (to) {
                xprt->timeout = *to;
                xprt->timeout.to_current = to->to_initval;
                xprt->timeout.to_resrvval = to->to_maxval << 1;
        } else
                xprt_default_timeout(&xprt->timeout, xprt->prot);

        xprt->pending = RPC_INIT_WAITQ("xprt_pending");
        xprt->sending = RPC_INIT_WAITQ("xprt_sending");
        xprt->backlog = RPC_INIT_WAITQ("xprt_backlog");
        xprt->reconn  = RPC_INIT_WAITQ("xprt_reconn");

        /* 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;

        INIT_LIST_HEAD(&xprt->rx_pending);

        dprintk("RPC:      created transport %p\n", xprt);
        
        xprt_bind_socket(xprt, sock);
        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 int 
xprt_bind_socket(struct rpc_xprt *xprt, struct socket *sock)
{
        struct sock     *sk = sock->sk;

        if (xprt->inet)
                return -EBUSY;

        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->write_space = udp_write_space;
                sk->no_check = UDP_CSUM_NORCV;
                xprt->connected = 1;
        } else {
                sk->data_ready = tcp_data_ready;
                sk->state_change = tcp_state_change;
                sk->write_space = tcp_write_space;
                xprt->connected = 0;
        }

        /* Reset to new socket */
        xprt->sock = sock;
        xprt->inet = sk;
        /*
         *      TCP requires the rpc I/O daemon is present
         */
        if(xprt->stream)
                rpciod_up();

        return 0;
}

/*
 * Create a client socket given the protocol and peer address.
 */
static struct socket *
xprt_create_socket(int proto, struct rpc_timeout *to)
{
        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 (capable(CAP_NET_BIND_SERVICE) && xprt_bindresvport(sock) < 0)
                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 socket   *sock;
        struct rpc_xprt *xprt;

        dprintk("RPC:      xprt_create_proto called\n");

        if (!(sock = xprt_create_socket(proto, to)))
                return NULL;

        if (!(xprt = xprt_setup(sock, proto, sap, to)))
                sock_release(sock);

        return xprt;
}

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

/*
 * Clear the xprt backlog queue
 */
int
xprt_clear_backlog(struct rpc_xprt *xprt) {
        if (RPCXPRT_CONGESTED(xprt))
                return 0;
        rpc_wake_up_next(&xprt->backlog);
        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;
}