[PATCH] knfsd: allow sockets to be passed to nfsd via 'portlist'

[linux-2.6/kvm.git] / net / sunrpc / svcsock.c

/*
 * linux/net/sunrpc/svcsock.c
 *
 * These are the RPC server socket internals.
 *
 * The server scheduling algorithm does not always distribute the load
 * evenly when servicing a single client. May need to modify the
 * svc_sock_enqueue procedure...
 *
 * TCP support is largely untested and may be a little slow. The problem
 * is that we currently do two separate recvfrom's, one for the 4-byte
 * record length, and the second for the actual record. This could possibly
 * be improved by always reading a minimum size of around 100 bytes and
 * tucking any superfluous bytes away in a temporary store. Still, that
 * leaves write requests out in the rain. An alternative may be to peek at
 * the first skb in the queue, and if it matches the next TCP sequence
 * number, to extract the record marker. Yuck.
 *
 * Copyright (C) 1995, 1996 Olaf Kirch <okir@monad.swb.de>
 */

#include <linux/sched.h>
#include <linux/errno.h>
#include <linux/fcntl.h>
#include <linux/net.h>
#include <linux/in.h>
#include <linux/inet.h>
#include <linux/udp.h>
#include <linux/tcp.h>
#include <linux/unistd.h>
#include <linux/slab.h>
#include <linux/netdevice.h>
#include <linux/skbuff.h>
#include <linux/file.h>
#include <net/sock.h>
#include <net/checksum.h>
#include <net/ip.h>
#include <net/tcp_states.h>
#include <asm/uaccess.h>
#include <asm/ioctls.h>

#include <linux/sunrpc/types.h>
#include <linux/sunrpc/xdr.h>
#include <linux/sunrpc/svcsock.h>
#include <linux/sunrpc/stats.h>

/* SMP locking strategy:
 *
 *      svc_serv->sv_lock protects most stuff for that service.
 *
 *      Some flags can be set to certain values at any time
 *      providing that certain rules are followed:
 *
 *      SK_BUSY  can be set to 0 at any time.  
 *              svc_sock_enqueue must be called afterwards
 *      SK_CONN, SK_DATA, can be set or cleared at any time.
 *              after a set, svc_sock_enqueue must be called.   
 *              after a clear, the socket must be read/accepted
 *               if this succeeds, it must be set again.
 *      SK_CLOSE can set at any time. It is never cleared.
 *
 */

#define RPCDBG_FACILITY RPCDBG_SVCSOCK


static struct svc_sock *svc_setup_socket(struct svc_serv *, struct socket *,
                                         int *errp, int pmap_reg);
static void             svc_udp_data_ready(struct sock *, int);
static int              svc_udp_recvfrom(struct svc_rqst *);
static int              svc_udp_sendto(struct svc_rqst *);

static struct svc_deferred_req *svc_deferred_dequeue(struct svc_sock *svsk);
static int svc_deferred_recv(struct svc_rqst *rqstp);
static struct cache_deferred_req *svc_defer(struct cache_req *req);

/*
 * Queue up an idle server thread.  Must have serv->sv_lock held.
 * Note: this is really a stack rather than a queue, so that we only
 * use as many different threads as we need, and the rest don't polute
 * the cache.
 */
static inline void
svc_serv_enqueue(struct svc_serv *serv, struct svc_rqst *rqstp)
{
        list_add(&rqstp->rq_list, &serv->sv_threads);
}

/*
 * Dequeue an nfsd thread.  Must have serv->sv_lock held.
 */
static inline void
svc_serv_dequeue(struct svc_serv *serv, struct svc_rqst *rqstp)
{
        list_del(&rqstp->rq_list);
}

/*
 * Release an skbuff after use
 */
static inline void
svc_release_skb(struct svc_rqst *rqstp)
{
        struct sk_buff *skb = rqstp->rq_skbuff;
        struct svc_deferred_req *dr = rqstp->rq_deferred;

        if (skb) {
                rqstp->rq_skbuff = NULL;

                dprintk("svc: service %p, releasing skb %p\n", rqstp, skb);
                skb_free_datagram(rqstp->rq_sock->sk_sk, skb);
        }
        if (dr) {
                rqstp->rq_deferred = NULL;
                kfree(dr);
        }
}

/*
 * Any space to write?
 */
static inline unsigned long
svc_sock_wspace(struct svc_sock *svsk)
{
        int wspace;

        if (svsk->sk_sock->type == SOCK_STREAM)
                wspace = sk_stream_wspace(svsk->sk_sk);
        else
                wspace = sock_wspace(svsk->sk_sk);

        return wspace;
}

/*
 * Queue up a socket with data pending. If there are idle nfsd
 * processes, wake 'em up.
 *
 */
static void
svc_sock_enqueue(struct svc_sock *svsk)
{
        struct svc_serv *serv = svsk->sk_server;
        struct svc_rqst *rqstp;

        if (!(svsk->sk_flags &
              ( (1<<SK_CONN)|(1<<SK_DATA)|(1<<SK_CLOSE)|(1<<SK_DEFERRED)) ))
                return;
        if (test_bit(SK_DEAD, &svsk->sk_flags))
                return;

        spin_lock_bh(&serv->sv_lock);

        if (!list_empty(&serv->sv_threads) && 
            !list_empty(&serv->sv_sockets))
                printk(KERN_ERR
                        "svc_sock_enqueue: threads and sockets both waiting??\n");

        if (test_bit(SK_DEAD, &svsk->sk_flags)) {
                /* Don't enqueue dead sockets */
                dprintk("svc: socket %p is dead, not enqueued\n", svsk->sk_sk);
                goto out_unlock;
        }

        if (test_bit(SK_BUSY, &svsk->sk_flags)) {
                /* Don't enqueue socket while daemon is receiving */
                dprintk("svc: socket %p busy, not enqueued\n", svsk->sk_sk);
                goto out_unlock;
        }

        set_bit(SOCK_NOSPACE, &svsk->sk_sock->flags);
        if (((svsk->sk_reserved + serv->sv_bufsz)*2
             > svc_sock_wspace(svsk))
            && !test_bit(SK_CLOSE, &svsk->sk_flags)
            && !test_bit(SK_CONN, &svsk->sk_flags)) {
                /* Don't enqueue while not enough space for reply */
                dprintk("svc: socket %p  no space, %d*2 > %ld, not enqueued\n",
                        svsk->sk_sk, svsk->sk_reserved+serv->sv_bufsz,
                        svc_sock_wspace(svsk));
                goto out_unlock;
        }
        clear_bit(SOCK_NOSPACE, &svsk->sk_sock->flags);

        /* Mark socket as busy. It will remain in this state until the
         * server has processed all pending data and put the socket back
         * on the idle list.
         */
        set_bit(SK_BUSY, &svsk->sk_flags);

        if (!list_empty(&serv->sv_threads)) {
                rqstp = list_entry(serv->sv_threads.next,
                                   struct svc_rqst,
                                   rq_list);
                dprintk("svc: socket %p served by daemon %p\n",
                        svsk->sk_sk, rqstp);
                svc_serv_dequeue(serv, rqstp);
                if (rqstp->rq_sock)
                        printk(KERN_ERR 
                                "svc_sock_enqueue: server %p, rq_sock=%p!\n",
                                rqstp, rqstp->rq_sock);
                rqstp->rq_sock = svsk;
                svsk->sk_inuse++;
                rqstp->rq_reserved = serv->sv_bufsz;
                svsk->sk_reserved += rqstp->rq_reserved;
                wake_up(&rqstp->rq_wait);
        } else {
                dprintk("svc: socket %p put into queue\n", svsk->sk_sk);
                list_add_tail(&svsk->sk_ready, &serv->sv_sockets);
        }

out_unlock:
        spin_unlock_bh(&serv->sv_lock);
}

/*
 * Dequeue the first socket.  Must be called with the serv->sv_lock held.
 */
static inline struct svc_sock *
svc_sock_dequeue(struct svc_serv *serv)
{
        struct svc_sock *svsk;

        if (list_empty(&serv->sv_sockets))
                return NULL;

        svsk = list_entry(serv->sv_sockets.next,
                          struct svc_sock, sk_ready);
        list_del_init(&svsk->sk_ready);

        dprintk("svc: socket %p dequeued, inuse=%d\n",
                svsk->sk_sk, svsk->sk_inuse);

        return svsk;
}

/*
 * Having read something from a socket, check whether it
 * needs to be re-enqueued.
 * Note: SK_DATA only gets cleared when a read-attempt finds
 * no (or insufficient) data.
 */
static inline void
svc_sock_received(struct svc_sock *svsk)
{
        clear_bit(SK_BUSY, &svsk->sk_flags);
        svc_sock_enqueue(svsk);
}


/**
 * svc_reserve - change the space reserved for the reply to a request.
 * @rqstp:  The request in question
 * @space: new max space to reserve
 *
 * Each request reserves some space on the output queue of the socket
 * to make sure the reply fits.  This function reduces that reserved
 * space to be the amount of space used already, plus @space.
 *
 */
void svc_reserve(struct svc_rqst *rqstp, int space)
{
        space += rqstp->rq_res.head[0].iov_len;

        if (space < rqstp->rq_reserved) {
                struct svc_sock *svsk = rqstp->rq_sock;
                spin_lock_bh(&svsk->sk_server->sv_lock);
                svsk->sk_reserved -= (rqstp->rq_reserved - space);
                rqstp->rq_reserved = space;
                spin_unlock_bh(&svsk->sk_server->sv_lock);

                svc_sock_enqueue(svsk);
        }
}

/*
 * Release a socket after use.
 */
static inline void
svc_sock_put(struct svc_sock *svsk)
{
        struct svc_serv *serv = svsk->sk_server;

        spin_lock_bh(&serv->sv_lock);
        if (!--(svsk->sk_inuse) && test_bit(SK_DEAD, &svsk->sk_flags)) {
                spin_unlock_bh(&serv->sv_lock);
                dprintk("svc: releasing dead socket\n");
                sock_release(svsk->sk_sock);
                kfree(svsk);
        }
        else
                spin_unlock_bh(&serv->sv_lock);
}

static void
svc_sock_release(struct svc_rqst *rqstp)
{
        struct svc_sock *svsk = rqstp->rq_sock;

        svc_release_skb(rqstp);

        svc_free_allpages(rqstp);
        rqstp->rq_res.page_len = 0;
        rqstp->rq_res.page_base = 0;


        /* Reset response buffer and release
         * the reservation.
         * But first, check that enough space was reserved
         * for the reply, otherwise we have a bug!
         */
        if ((rqstp->rq_res.len) >  rqstp->rq_reserved)
                printk(KERN_ERR "RPC request reserved %d but used %d\n",
                       rqstp->rq_reserved,
                       rqstp->rq_res.len);

        rqstp->rq_res.head[0].iov_len = 0;
        svc_reserve(rqstp, 0);
        rqstp->rq_sock = NULL;

        svc_sock_put(svsk);
}

/*
 * External function to wake up a server waiting for data
 */
void
svc_wake_up(struct svc_serv *serv)
{
        struct svc_rqst *rqstp;

        spin_lock_bh(&serv->sv_lock);
        if (!list_empty(&serv->sv_threads)) {
                rqstp = list_entry(serv->sv_threads.next,
                                   struct svc_rqst,
                                   rq_list);
                dprintk("svc: daemon %p woken up.\n", rqstp);
                /*
                svc_serv_dequeue(serv, rqstp);
                rqstp->rq_sock = NULL;
                 */
                wake_up(&rqstp->rq_wait);
        }
        spin_unlock_bh(&serv->sv_lock);
}

/*
 * Generic sendto routine
 */
static int
svc_sendto(struct svc_rqst *rqstp, struct xdr_buf *xdr)
{
        struct svc_sock *svsk = rqstp->rq_sock;
        struct socket   *sock = svsk->sk_sock;
        int             slen;
        char            buffer[CMSG_SPACE(sizeof(struct in_pktinfo))];
        struct cmsghdr *cmh = (struct cmsghdr *)buffer;
        struct in_pktinfo *pki = (struct in_pktinfo *)CMSG_DATA(cmh);
        int             len = 0;
        int             result;
        int             size;
        struct page     **ppage = xdr->pages;
        size_t          base = xdr->page_base;
        unsigned int    pglen = xdr->page_len;
        unsigned int    flags = MSG_MORE;

        slen = xdr->len;

        if (rqstp->rq_prot == IPPROTO_UDP) {
                /* set the source and destination */
                struct msghdr   msg;
                msg.msg_name    = &rqstp->rq_addr;
                msg.msg_namelen = sizeof(rqstp->rq_addr);
                msg.msg_iov     = NULL;
                msg.msg_iovlen  = 0;
                msg.msg_flags   = MSG_MORE;

                msg.msg_control = cmh;
                msg.msg_controllen = sizeof(buffer);
                cmh->cmsg_len = CMSG_LEN(sizeof(*pki));
                cmh->cmsg_level = SOL_IP;
                cmh->cmsg_type = IP_PKTINFO;
                pki->ipi_ifindex = 0;
                pki->ipi_spec_dst.s_addr = rqstp->rq_daddr;

                if (sock_sendmsg(sock, &msg, 0) < 0)
                        goto out;
        }

        /* send head */
        if (slen == xdr->head[0].iov_len)
                flags = 0;
        len = kernel_sendpage(sock, rqstp->rq_respages[0], 0, xdr->head[0].iov_len, flags);
        if (len != xdr->head[0].iov_len)
                goto out;
        slen -= xdr->head[0].iov_len;
        if (slen == 0)
                goto out;

        /* send page data */
        size = PAGE_SIZE - base < pglen ? PAGE_SIZE - base : pglen;
        while (pglen > 0) {
                if (slen == size)
                        flags = 0;
                result = kernel_sendpage(sock, *ppage, base, size, flags);
                if (result > 0)
                        len += result;
                if (result != size)
                        goto out;
                slen -= size;
                pglen -= size;
                size = PAGE_SIZE < pglen ? PAGE_SIZE : pglen;
                base = 0;
                ppage++;
        }
        /* send tail */
        if (xdr->tail[0].iov_len) {
                result = kernel_sendpage(sock, rqstp->rq_respages[rqstp->rq_restailpage],
                                             ((unsigned long)xdr->tail[0].iov_base)& (PAGE_SIZE-1),
                                             xdr->tail[0].iov_len, 0);

                if (result > 0)
                        len += result;
        }
out:
        dprintk("svc: socket %p sendto([%p %Zu... ], %d) = %d (addr %x)\n",
                        rqstp->rq_sock, xdr->head[0].iov_base, xdr->head[0].iov_len, xdr->len, len,
                rqstp->rq_addr.sin_addr.s_addr);

        return len;
}

/*
 * Report socket names for nfsdfs
 */
static int one_sock_name(char *buf, struct svc_sock *svsk)
{
        int len;

        switch(svsk->sk_sk->sk_family) {
        case AF_INET:
                len = sprintf(buf, "ipv4 %s %u.%u.%u.%u %d\n",
                              svsk->sk_sk->sk_protocol==IPPROTO_UDP?
                              "udp" : "tcp",
                              NIPQUAD(inet_sk(svsk->sk_sk)->rcv_saddr),
                              inet_sk(svsk->sk_sk)->num);
                break;
        default:
                len = sprintf(buf, "*unknown-%d*\n",
                               svsk->sk_sk->sk_family);
        }
        return len;
}

int
svc_sock_names(char *buf, struct svc_serv *serv, char *toclose)
{
        struct svc_sock *svsk, *closesk = NULL;
        int len = 0;

        if (!serv)
                return 0;
        spin_lock(&serv->sv_lock);
        list_for_each_entry(svsk, &serv->sv_permsocks, sk_list) {
                int onelen = one_sock_name(buf+len, svsk);
                if (toclose && strcmp(toclose, buf+len) == 0)
                        closesk = svsk;
                else
                        len += onelen;
        }
        spin_unlock(&serv->sv_lock);
        if (closesk)
                svc_delete_socket(closesk);
        return len;
}
EXPORT_SYMBOL(svc_sock_names);

/*
 * Check input queue length
 */
static int
svc_recv_available(struct svc_sock *svsk)
{
        struct socket   *sock = svsk->sk_sock;
        int             avail, err;

        err = kernel_sock_ioctl(sock, TIOCINQ, (unsigned long) &avail);

        return (err >= 0)? avail : err;
}

/*
 * Generic recvfrom routine.
 */
static int
svc_recvfrom(struct svc_rqst *rqstp, struct kvec *iov, int nr, int buflen)
{
        struct msghdr   msg;
        struct socket   *sock;
        int             len, alen;

        rqstp->rq_addrlen = sizeof(rqstp->rq_addr);
        sock = rqstp->rq_sock->sk_sock;

        msg.msg_name    = &rqstp->rq_addr;
        msg.msg_namelen = sizeof(rqstp->rq_addr);
        msg.msg_control = NULL;
        msg.msg_controllen = 0;

        msg.msg_flags   = MSG_DONTWAIT;

        len = kernel_recvmsg(sock, &msg, iov, nr, buflen, MSG_DONTWAIT);

        /* sock_recvmsg doesn't fill in the name/namelen, so we must..
         * possibly we should cache this in the svc_sock structure
         * at accept time. FIXME
         */
        alen = sizeof(rqstp->rq_addr);
        kernel_getpeername(sock, (struct sockaddr *)&rqstp->rq_addr, &alen);

        dprintk("svc: socket %p recvfrom(%p, %Zu) = %d\n",
                rqstp->rq_sock, iov[0].iov_base, iov[0].iov_len, len);

        return len;
}

/*
 * Set socket snd and rcv buffer lengths
 */
static inline void
svc_sock_setbufsize(struct socket *sock, unsigned int snd, unsigned int rcv)
{
#if 0
        mm_segment_t    oldfs;
        oldfs = get_fs(); set_fs(KERNEL_DS);
        sock_setsockopt(sock, SOL_SOCKET, SO_SNDBUF,
                        (char*)&snd, sizeof(snd));
        sock_setsockopt(sock, SOL_SOCKET, SO_RCVBUF,
                        (char*)&rcv, sizeof(rcv));
#else
        /* sock_setsockopt limits use to sysctl_?mem_max,
         * which isn't acceptable.  Until that is made conditional
         * on not having CAP_SYS_RESOURCE or similar, we go direct...
         * DaveM said I could!
         */
        lock_sock(sock->sk);
        sock->sk->sk_sndbuf = snd * 2;
        sock->sk->sk_rcvbuf = rcv * 2;
        sock->sk->sk_userlocks |= SOCK_SNDBUF_LOCK|SOCK_RCVBUF_LOCK;
        release_sock(sock->sk);
#endif
}
/*
 * INET callback when data has been received on the socket.
 */
static void
svc_udp_data_ready(struct sock *sk, int count)
{
        struct svc_sock *svsk = (struct svc_sock *)sk->sk_user_data;

        if (svsk) {
                dprintk("svc: socket %p(inet %p), count=%d, busy=%d\n",
                        svsk, sk, count, test_bit(SK_BUSY, &svsk->sk_flags));
                set_bit(SK_DATA, &svsk->sk_flags);
                svc_sock_enqueue(svsk);
        }
        if (sk->sk_sleep && waitqueue_active(sk->sk_sleep))
                wake_up_interruptible(sk->sk_sleep);
}

/*
 * INET callback when space is newly available on the socket.
 */
static void
svc_write_space(struct sock *sk)
{
        struct svc_sock *svsk = (struct svc_sock *)(sk->sk_user_data);

        if (svsk) {
                dprintk("svc: socket %p(inet %p), write_space busy=%d\n",
                        svsk, sk, test_bit(SK_BUSY, &svsk->sk_flags));
                svc_sock_enqueue(svsk);
        }

        if (sk->sk_sleep && waitqueue_active(sk->sk_sleep)) {
                dprintk("RPC svc_write_space: someone sleeping on %p\n",
                       svsk);
                wake_up_interruptible(sk->sk_sleep);
        }
}

/*
 * Receive a datagram from a UDP socket.
 */
static int
svc_udp_recvfrom(struct svc_rqst *rqstp)
{
        struct svc_sock *svsk = rqstp->rq_sock;
        struct svc_serv *serv = svsk->sk_server;
        struct sk_buff  *skb;
        int             err, len;

        if (test_and_clear_bit(SK_CHNGBUF, &svsk->sk_flags))
            /* udp sockets need large rcvbuf as all pending
             * requests are still in that buffer.  sndbuf must
             * also be large enough that there is enough space
             * for one reply per thread.
             */
            svc_sock_setbufsize(svsk->sk_sock,
                                (serv->sv_nrthreads+3) * serv->sv_bufsz,
                                (serv->sv_nrthreads+3) * serv->sv_bufsz);

        if ((rqstp->rq_deferred = svc_deferred_dequeue(svsk))) {
                svc_sock_received(svsk);
                return svc_deferred_recv(rqstp);
        }

        clear_bit(SK_DATA, &svsk->sk_flags);
        while ((skb = skb_recv_datagram(svsk->sk_sk, 0, 1, &err)) == NULL) {
                if (err == -EAGAIN) {
                        svc_sock_received(svsk);
                        return err;
                }
                /* possibly an icmp error */
                dprintk("svc: recvfrom returned error %d\n", -err);
        }
        if (skb->tstamp.off_sec == 0) {
                struct timeval tv;

                tv.tv_sec = xtime.tv_sec;
                tv.tv_usec = xtime.tv_nsec / NSEC_PER_USEC;
                skb_set_timestamp(skb, &tv);
                /* Don't enable netstamp, sunrpc doesn't 
                   need that much accuracy */
        }
        skb_get_timestamp(skb, &svsk->sk_sk->sk_stamp);
        set_bit(SK_DATA, &svsk->sk_flags); /* there may be more data... */

        /*
         * Maybe more packets - kick another thread ASAP.
         */
        svc_sock_received(svsk);

        len  = skb->len - sizeof(struct udphdr);
        rqstp->rq_arg.len = len;

        rqstp->rq_prot        = IPPROTO_UDP;

        /* Get sender address */
        rqstp->rq_addr.sin_family = AF_INET;
        rqstp->rq_addr.sin_port = skb->h.uh->source;
        rqstp->rq_addr.sin_addr.s_addr = skb->nh.iph->saddr;
        rqstp->rq_daddr = skb->nh.iph->daddr;

        if (skb_is_nonlinear(skb)) {
                /* we have to copy */
                local_bh_disable();
                if (csum_partial_copy_to_xdr(&rqstp->rq_arg, skb)) {
                        local_bh_enable();
                        /* checksum error */
                        skb_free_datagram(svsk->sk_sk, skb);
                        return 0;
                }
                local_bh_enable();
                skb_free_datagram(svsk->sk_sk, skb); 
        } else {
                /* we can use it in-place */
                rqstp->rq_arg.head[0].iov_base = skb->data + sizeof(struct udphdr);
                rqstp->rq_arg.head[0].iov_len = len;
                if (skb_checksum_complete(skb)) {
                        skb_free_datagram(svsk->sk_sk, skb);
                        return 0;
                }
                rqstp->rq_skbuff = skb;
        }

        rqstp->rq_arg.page_base = 0;
        if (len <= rqstp->rq_arg.head[0].iov_len) {
                rqstp->rq_arg.head[0].iov_len = len;
                rqstp->rq_arg.page_len = 0;
        } else {
                rqstp->rq_arg.page_len = len - rqstp->rq_arg.head[0].iov_len;
                rqstp->rq_argused += (rqstp->rq_arg.page_len + PAGE_SIZE - 1)/ PAGE_SIZE;
        }

        if (serv->sv_stats)
                serv->sv_stats->netudpcnt++;

        return len;
}

static int
svc_udp_sendto(struct svc_rqst *rqstp)
{
        int             error;

        error = svc_sendto(rqstp, &rqstp->rq_res);
        if (error == -ECONNREFUSED)
                /* ICMP error on earlier request. */
                error = svc_sendto(rqstp, &rqstp->rq_res);

        return error;
}

static void
svc_udp_init(struct svc_sock *svsk)
{
        svsk->sk_sk->sk_data_ready = svc_udp_data_ready;
        svsk->sk_sk->sk_write_space = svc_write_space;
        svsk->sk_recvfrom = svc_udp_recvfrom;
        svsk->sk_sendto = svc_udp_sendto;

        /* initialise setting must have enough space to
         * receive and respond to one request.  
         * svc_udp_recvfrom will re-adjust if necessary
         */
        svc_sock_setbufsize(svsk->sk_sock,
                            3 * svsk->sk_server->sv_bufsz,
                            3 * svsk->sk_server->sv_bufsz);

        set_bit(SK_DATA, &svsk->sk_flags); /* might have come in before data_ready set up */
        set_bit(SK_CHNGBUF, &svsk->sk_flags);
}

/*
 * A data_ready event on a listening socket means there's a connection
 * pending. Do not use state_change as a substitute for it.
 */
static void
svc_tcp_listen_data_ready(struct sock *sk, int count_unused)
{
        struct svc_sock *svsk = (struct svc_sock *)sk->sk_user_data;

        dprintk("svc: socket %p TCP (listen) state change %d\n",
                sk, sk->sk_state);

        /*
         * This callback may called twice when a new connection
         * is established as a child socket inherits everything
         * from a parent LISTEN socket.
         * 1) data_ready method of the parent socket will be called
         *    when one of child sockets become ESTABLISHED.
         * 2) data_ready method of the child socket may be called
         *    when it receives data before the socket is accepted.
         * In case of 2, we should ignore it silently.
         */
        if (sk->sk_state == TCP_LISTEN) {
                if (svsk) {
                        set_bit(SK_CONN, &svsk->sk_flags);
                        svc_sock_enqueue(svsk);
                } else
                        printk("svc: socket %p: no user data\n", sk);
        }

        if (sk->sk_sleep && waitqueue_active(sk->sk_sleep))
                wake_up_interruptible_all(sk->sk_sleep);
}

/*
 * A state change on a connected socket means it's dying or dead.
 */
static void
svc_tcp_state_change(struct sock *sk)
{
        struct svc_sock *svsk = (struct svc_sock *)sk->sk_user_data;

        dprintk("svc: socket %p TCP (connected) state change %d (svsk %p)\n",
                sk, sk->sk_state, sk->sk_user_data);

        if (!svsk)
                printk("svc: socket %p: no user data\n", sk);
        else {
                set_bit(SK_CLOSE, &svsk->sk_flags);
                svc_sock_enqueue(svsk);
        }
        if (sk->sk_sleep && waitqueue_active(sk->sk_sleep))
                wake_up_interruptible_all(sk->sk_sleep);
}

static void
svc_tcp_data_ready(struct sock *sk, int count)
{
        struct svc_sock *svsk = (struct svc_sock *)sk->sk_user_data;

        dprintk("svc: socket %p TCP data ready (svsk %p)\n",
                sk, sk->sk_user_data);
        if (svsk) {
                set_bit(SK_DATA, &svsk->sk_flags);
                svc_sock_enqueue(svsk);
        }
        if (sk->sk_sleep && waitqueue_active(sk->sk_sleep))
                wake_up_interruptible(sk->sk_sleep);
}

/*
 * Accept a TCP connection
 */
static void
svc_tcp_accept(struct svc_sock *svsk)
{
        struct sockaddr_in sin;
        struct svc_serv *serv = svsk->sk_server;
        struct socket   *sock = svsk->sk_sock;
        struct socket   *newsock;
        struct svc_sock *newsvsk;
        int             err, slen;

        dprintk("svc: tcp_accept %p sock %p\n", svsk, sock);
        if (!sock)
                return;

        clear_bit(SK_CONN, &svsk->sk_flags);
        err = kernel_accept(sock, &newsock, O_NONBLOCK);
        if (err < 0) {
                if (err == -ENOMEM)
                        printk(KERN_WARNING "%s: no more sockets!\n",
                               serv->sv_name);
                else if (err != -EAGAIN && net_ratelimit())
                        printk(KERN_WARNING "%s: accept failed (err %d)!\n",
                                   serv->sv_name, -err);
                return;
        }

        set_bit(SK_CONN, &svsk->sk_flags);
        svc_sock_enqueue(svsk);

        slen = sizeof(sin);
        err = kernel_getpeername(newsock, (struct sockaddr *) &sin, &slen);
        if (err < 0) {
                if (net_ratelimit())
                        printk(KERN_WARNING "%s: peername failed (err %d)!\n",
                                   serv->sv_name, -err);
                goto failed;            /* aborted connection or whatever */
        }

        /* Ideally, we would want to reject connections from unauthorized
         * hosts here, but when we get encription, the IP of the host won't
         * tell us anything. For now just warn about unpriv connections.
         */
        if (ntohs(sin.sin_port) >= 1024) {
                dprintk(KERN_WARNING
                        "%s: connect from unprivileged port: %u.%u.%u.%u:%d\n",
                        serv->sv_name, 
                        NIPQUAD(sin.sin_addr.s_addr), ntohs(sin.sin_port));
        }

        dprintk("%s: connect from %u.%u.%u.%u:%04x\n", serv->sv_name,
                        NIPQUAD(sin.sin_addr.s_addr), ntohs(sin.sin_port));

        /* make sure that a write doesn't block forever when
         * low on memory
         */
        newsock->sk->sk_sndtimeo = HZ*30;

        if (!(newsvsk = svc_setup_socket(serv, newsock, &err, 0)))
                goto failed;


        /* make sure that we don't have too many active connections.
         * If we have, something must be dropped.
         *
         * There's no point in trying to do random drop here for
         * DoS prevention. The NFS clients does 1 reconnect in 15
         * seconds. An attacker can easily beat that.
         *
         * The only somewhat efficient mechanism would be if drop
         * old connections from the same IP first. But right now
         * we don't even record the client IP in svc_sock.
         */
        if (serv->sv_tmpcnt > (serv->sv_nrthreads+3)*20) {
                struct svc_sock *svsk = NULL;
                spin_lock_bh(&serv->sv_lock);
                if (!list_empty(&serv->sv_tempsocks)) {
                        if (net_ratelimit()) {
                                /* Try to help the admin */
                                printk(KERN_NOTICE "%s: too many open TCP "
                                        "sockets, consider increasing the "
                                        "number of nfsd threads\n",
                                                   serv->sv_name);
                                printk(KERN_NOTICE "%s: last TCP connect from "
                                        "%u.%u.%u.%u:%d\n",
                                        serv->sv_name,
                                        NIPQUAD(sin.sin_addr.s_addr),
                                        ntohs(sin.sin_port));
                        }
                        /*
                         * Always select the oldest socket. It's not fair,
                         * but so is life
                         */
                        svsk = list_entry(serv->sv_tempsocks.prev,
                                          struct svc_sock,
                                          sk_list);
                        set_bit(SK_CLOSE, &svsk->sk_flags);
                        svsk->sk_inuse ++;
                }
                spin_unlock_bh(&serv->sv_lock);

                if (svsk) {
                        svc_sock_enqueue(svsk);
                        svc_sock_put(svsk);
                }

        }

        if (serv->sv_stats)
                serv->sv_stats->nettcpconn++;

        return;

failed:
        sock_release(newsock);
        return;
}

/*
 * Receive data from a TCP socket.
 */
static int
svc_tcp_recvfrom(struct svc_rqst *rqstp)
{
        struct svc_sock *svsk = rqstp->rq_sock;
        struct svc_serv *serv = svsk->sk_server;
        int             len;
        struct kvec vec[RPCSVC_MAXPAGES];
        int pnum, vlen;

        dprintk("svc: tcp_recv %p data %d conn %d close %d\n",
                svsk, test_bit(SK_DATA, &svsk->sk_flags),
                test_bit(SK_CONN, &svsk->sk_flags),
                test_bit(SK_CLOSE, &svsk->sk_flags));

        if ((rqstp->rq_deferred = svc_deferred_dequeue(svsk))) {
                svc_sock_received(svsk);
                return svc_deferred_recv(rqstp);
        }

        if (test_bit(SK_CLOSE, &svsk->sk_flags)) {
                svc_delete_socket(svsk);
                return 0;
        }

        if (test_bit(SK_CONN, &svsk->sk_flags)) {
                svc_tcp_accept(svsk);
                svc_sock_received(svsk);
                return 0;
        }

        if (test_and_clear_bit(SK_CHNGBUF, &svsk->sk_flags))
                /* sndbuf needs to have room for one request
                 * per thread, otherwise we can stall even when the
                 * network isn't a bottleneck.
                 * rcvbuf just needs to be able to hold a few requests.
                 * Normally they will be removed from the queue 
                 * as soon a a complete request arrives.
                 */
                svc_sock_setbufsize(svsk->sk_sock,
                                    (serv->sv_nrthreads+3) * serv->sv_bufsz,
                                    3 * serv->sv_bufsz);

        clear_bit(SK_DATA, &svsk->sk_flags);

        /* Receive data. If we haven't got the record length yet, get
         * the next four bytes. Otherwise try to gobble up as much as
         * possible up to the complete record length.
         */
        if (svsk->sk_tcplen < 4) {
                unsigned long   want = 4 - svsk->sk_tcplen;
                struct kvec     iov;

                iov.iov_base = ((char *) &svsk->sk_reclen) + svsk->sk_tcplen;
                iov.iov_len  = want;
                if ((len = svc_recvfrom(rqstp, &iov, 1, want)) < 0)
                        goto error;
                svsk->sk_tcplen += len;

                if (len < want) {
                        dprintk("svc: short recvfrom while reading record length (%d of %lu)\n",
                                len, want);
                        svc_sock_received(svsk);
                        return -EAGAIN; /* record header not complete */
                }

                svsk->sk_reclen = ntohl(svsk->sk_reclen);
                if (!(svsk->sk_reclen & 0x80000000)) {
                        /* FIXME: technically, a record can be fragmented,
                         *  and non-terminal fragments will not have the top
                         *  bit set in the fragment length header.
                         *  But apparently no known nfs clients send fragmented
                         *  records. */
                        printk(KERN_NOTICE "RPC: bad TCP reclen 0x%08lx (non-terminal)\n",
                               (unsigned long) svsk->sk_reclen);
                        goto err_delete;
                }
                svsk->sk_reclen &= 0x7fffffff;
                dprintk("svc: TCP record, %d bytes\n", svsk->sk_reclen);
                if (svsk->sk_reclen > serv->sv_bufsz) {
                        printk(KERN_NOTICE "RPC: bad TCP reclen 0x%08lx (large)\n",
                               (unsigned long) svsk->sk_reclen);
                        goto err_delete;
                }
        }

        /* Check whether enough data is available */
        len = svc_recv_available(svsk);
        if (len < 0)
                goto error;

        if (len < svsk->sk_reclen) {
                dprintk("svc: incomplete TCP record (%d of %d)\n",
                        len, svsk->sk_reclen);
                svc_sock_received(svsk);
                return -EAGAIN; /* record not complete */
        }
        len = svsk->sk_reclen;
        set_bit(SK_DATA, &svsk->sk_flags);

        vec[0] = rqstp->rq_arg.head[0];
        vlen = PAGE_SIZE;
        pnum = 1;
        while (vlen < len) {
                vec[pnum].iov_base = page_address(rqstp->rq_argpages[rqstp->rq_argused++]);
                vec[pnum].iov_len = PAGE_SIZE;
                pnum++;
                vlen += PAGE_SIZE;
        }

        /* Now receive data */
        len = svc_recvfrom(rqstp, vec, pnum, len);
        if (len < 0)
                goto error;

        dprintk("svc: TCP complete record (%d bytes)\n", len);
        rqstp->rq_arg.len = len;
        rqstp->rq_arg.page_base = 0;
        if (len <= rqstp->rq_arg.head[0].iov_len) {
                rqstp->rq_arg.head[0].iov_len = len;
                rqstp->rq_arg.page_len = 0;
        } else {
                rqstp->rq_arg.page_len = len - rqstp->rq_arg.head[0].iov_len;
        }

        rqstp->rq_skbuff      = NULL;
        rqstp->rq_prot        = IPPROTO_TCP;

        /* Reset TCP read info */
        svsk->sk_reclen = 0;
        svsk->sk_tcplen = 0;

        svc_sock_received(svsk);
        if (serv->sv_stats)
                serv->sv_stats->nettcpcnt++;

        return len;

 err_delete:
        svc_delete_socket(svsk);
        return -EAGAIN;

 error:
        if (len == -EAGAIN) {
                dprintk("RPC: TCP recvfrom got EAGAIN\n");
                svc_sock_received(svsk);
        } else {
                printk(KERN_NOTICE "%s: recvfrom returned errno %d\n",
                                        svsk->sk_server->sv_name, -len);
                goto err_delete;
        }

        return len;
}

/*
 * Send out data on TCP socket.
 */
static int
svc_tcp_sendto(struct svc_rqst *rqstp)
{
        struct xdr_buf  *xbufp = &rqstp->rq_res;
        int sent;
        __be32 reclen;

        /* Set up the first element of the reply kvec.
         * Any other kvecs that may be in use have been taken
         * care of by the server implementation itself.
         */
        reclen = htonl(0x80000000|((xbufp->len ) - 4));
        memcpy(xbufp->head[0].iov_base, &reclen, 4);

        if (test_bit(SK_DEAD, &rqstp->rq_sock->sk_flags))
                return -ENOTCONN;

        sent = svc_sendto(rqstp, &rqstp->rq_res);
        if (sent != xbufp->len) {
                printk(KERN_NOTICE "rpc-srv/tcp: %s: %s %d when sending %d bytes - shutting down socket\n",
                       rqstp->rq_sock->sk_server->sv_name,
                       (sent<0)?"got error":"sent only",
                       sent, xbufp->len);
                svc_delete_socket(rqstp->rq_sock);
                sent = -EAGAIN;
        }
        return sent;
}

static void
svc_tcp_init(struct svc_sock *svsk)
{
        struct sock     *sk = svsk->sk_sk;
        struct tcp_sock *tp = tcp_sk(sk);

        svsk->sk_recvfrom = svc_tcp_recvfrom;
        svsk->sk_sendto = svc_tcp_sendto;

        if (sk->sk_state == TCP_LISTEN) {
                dprintk("setting up TCP socket for listening\n");
                sk->sk_data_ready = svc_tcp_listen_data_ready;
                set_bit(SK_CONN, &svsk->sk_flags);
        } else {
                dprintk("setting up TCP socket for reading\n");
                sk->sk_state_change = svc_tcp_state_change;
                sk->sk_data_ready = svc_tcp_data_ready;
                sk->sk_write_space = svc_write_space;

                svsk->sk_reclen = 0;
                svsk->sk_tcplen = 0;

                tp->nonagle = 1;        /* disable Nagle's algorithm */

                /* initialise setting must have enough space to
                 * receive and respond to one request.  
                 * svc_tcp_recvfrom will re-adjust if necessary
                 */
                svc_sock_setbufsize(svsk->sk_sock,
                                    3 * svsk->sk_server->sv_bufsz,
                                    3 * svsk->sk_server->sv_bufsz);

                set_bit(SK_CHNGBUF, &svsk->sk_flags);
                set_bit(SK_DATA, &svsk->sk_flags);
                if (sk->sk_state != TCP_ESTABLISHED) 
                        set_bit(SK_CLOSE, &svsk->sk_flags);
        }
}

void
svc_sock_update_bufs(struct svc_serv *serv)
{
        /*
         * The number of server threads has changed. Update
         * rcvbuf and sndbuf accordingly on all sockets
         */
        struct list_head *le;

        spin_lock_bh(&serv->sv_lock);
        list_for_each(le, &serv->sv_permsocks) {
                struct svc_sock *svsk = 
                        list_entry(le, struct svc_sock, sk_list);
                set_bit(SK_CHNGBUF, &svsk->sk_flags);
        }
        list_for_each(le, &serv->sv_tempsocks) {
                struct svc_sock *svsk =
                        list_entry(le, struct svc_sock, sk_list);
                set_bit(SK_CHNGBUF, &svsk->sk_flags);
        }
        spin_unlock_bh(&serv->sv_lock);
}

/*
 * Receive the next request on any socket.
 */
int
svc_recv(struct svc_serv *serv, struct svc_rqst *rqstp, long timeout)
{
        struct svc_sock         *svsk =NULL;
        int                     len;
        int                     pages;
        struct xdr_buf          *arg;
        DECLARE_WAITQUEUE(wait, current);

        dprintk("svc: server %p waiting for data (to = %ld)\n",
                rqstp, timeout);

        if (rqstp->rq_sock)
                printk(KERN_ERR 
                        "svc_recv: service %p, socket not NULL!\n",
                         rqstp);
        if (waitqueue_active(&rqstp->rq_wait))
                printk(KERN_ERR 
                        "svc_recv: service %p, wait queue active!\n",
                         rqstp);

        /* Initialize the buffers */
        /* first reclaim pages that were moved to response list */
        svc_pushback_allpages(rqstp);

        /* now allocate needed pages.  If we get a failure, sleep briefly */
        pages = 2 + (serv->sv_bufsz + PAGE_SIZE -1) / PAGE_SIZE;
        while (rqstp->rq_arghi < pages) {
                struct page *p = alloc_page(GFP_KERNEL);
                if (!p) {
                        schedule_timeout_uninterruptible(msecs_to_jiffies(500));
                        continue;
                }
                rqstp->rq_argpages[rqstp->rq_arghi++] = p;
        }

        /* Make arg->head point to first page and arg->pages point to rest */
        arg = &rqstp->rq_arg;
        arg->head[0].iov_base = page_address(rqstp->rq_argpages[0]);
        arg->head[0].iov_len = PAGE_SIZE;
        rqstp->rq_argused = 1;
        arg->pages = rqstp->rq_argpages + 1;
        arg->page_base = 0;
        /* save at least one page for response */
        arg->page_len = (pages-2)*PAGE_SIZE;
        arg->len = (pages-1)*PAGE_SIZE;
        arg->tail[0].iov_len = 0;

        try_to_freeze();
        cond_resched();
        if (signalled())
                return -EINTR;

        spin_lock_bh(&serv->sv_lock);
        if (!list_empty(&serv->sv_tempsocks)) {
                svsk = list_entry(serv->sv_tempsocks.next,
                                  struct svc_sock, sk_list);
                /* apparently the "standard" is that clients close
                 * idle connections after 5 minutes, servers after
                 * 6 minutes
                 *   http://www.connectathon.org/talks96/nfstcp.pdf 
                 */
                if (get_seconds() - svsk->sk_lastrecv < 6*60
                    || test_bit(SK_BUSY, &svsk->sk_flags))
                        svsk = NULL;
        }
        if (svsk) {
                set_bit(SK_BUSY, &svsk->sk_flags);
                set_bit(SK_CLOSE, &svsk->sk_flags);
                rqstp->rq_sock = svsk;
                svsk->sk_inuse++;
        } else if ((svsk = svc_sock_dequeue(serv)) != NULL) {
                rqstp->rq_sock = svsk;
                svsk->sk_inuse++;
                rqstp->rq_reserved = serv->sv_bufsz;    
                svsk->sk_reserved += rqstp->rq_reserved;
        } else {
                /* No data pending. Go to sleep */
                svc_serv_enqueue(serv, rqstp);

                /*
                 * We have to be able to interrupt this wait
                 * to bring down the daemons ...
                 */
                set_current_state(TASK_INTERRUPTIBLE);
                add_wait_queue(&rqstp->rq_wait, &wait);
                spin_unlock_bh(&serv->sv_lock);

                schedule_timeout(timeout);

                try_to_freeze();

                spin_lock_bh(&serv->sv_lock);
                remove_wait_queue(&rqstp->rq_wait, &wait);

                if (!(svsk = rqstp->rq_sock)) {
                        svc_serv_dequeue(serv, rqstp);
                        spin_unlock_bh(&serv->sv_lock);
                        dprintk("svc: server %p, no data yet\n", rqstp);
                        return signalled()? -EINTR : -EAGAIN;
                }
        }
        spin_unlock_bh(&serv->sv_lock);

        dprintk("svc: server %p, socket %p, inuse=%d\n",
                 rqstp, svsk, svsk->sk_inuse);
        len = svsk->sk_recvfrom(rqstp);
        dprintk("svc: got len=%d\n", len);

        /* No data, incomplete (TCP) read, or accept() */
        if (len == 0 || len == -EAGAIN) {
                rqstp->rq_res.len = 0;
                svc_sock_release(rqstp);
                return -EAGAIN;
        }
        svsk->sk_lastrecv = get_seconds();
        if (test_bit(SK_TEMP, &svsk->sk_flags)) {
                /* push active sockets to end of list */
                spin_lock_bh(&serv->sv_lock);
                if (!list_empty(&svsk->sk_list))
                        list_move_tail(&svsk->sk_list, &serv->sv_tempsocks);
                spin_unlock_bh(&serv->sv_lock);
        }

        rqstp->rq_secure  = ntohs(rqstp->rq_addr.sin_port) < 1024;
        rqstp->rq_chandle.defer = svc_defer;

        if (serv->sv_stats)
                serv->sv_stats->netcnt++;
        return len;
}

/* 
 * Drop request
 */
void
svc_drop(struct svc_rqst *rqstp)
{
        dprintk("svc: socket %p dropped request\n", rqstp->rq_sock);
        svc_sock_release(rqstp);
}

/*
 * Return reply to client.
 */
int
svc_send(struct svc_rqst *rqstp)
{
        struct svc_sock *svsk;
        int             len;
        struct xdr_buf  *xb;

        if ((svsk = rqstp->rq_sock) == NULL) {
                printk(KERN_WARNING "NULL socket pointer in %s:%d\n",
                                __FILE__, __LINE__);
                return -EFAULT;
        }

        /* release the receive skb before sending the reply */
        svc_release_skb(rqstp);

        /* calculate over-all length */
        xb = & rqstp->rq_res;
        xb->len = xb->head[0].iov_len +
                xb->page_len +
                xb->tail[0].iov_len;

        /* Grab svsk->sk_mutex to serialize outgoing data. */
        mutex_lock(&svsk->sk_mutex);
        if (test_bit(SK_DEAD, &svsk->sk_flags))
                len = -ENOTCONN;
        else
                len = svsk->sk_sendto(rqstp);
        mutex_unlock(&svsk->sk_mutex);
        svc_sock_release(rqstp);

        if (len == -ECONNREFUSED || len == -ENOTCONN || len == -EAGAIN)
                return 0;
        return len;
}

/*
 * Initialize socket for RPC use and create svc_sock struct
 * XXX: May want to setsockopt SO_SNDBUF and SO_RCVBUF.
 */
static struct svc_sock *
svc_setup_socket(struct svc_serv *serv, struct socket *sock,
                                        int *errp, int pmap_register)
{
        struct svc_sock *svsk;
        struct sock     *inet;

        dprintk("svc: svc_setup_socket %p\n", sock);
        if (!(svsk = kzalloc(sizeof(*svsk), GFP_KERNEL))) {
                *errp = -ENOMEM;
                return NULL;
        }

        inet = sock->sk;

        /* Register socket with portmapper */
        if (*errp >= 0 && pmap_register)
                *errp = svc_register(serv, inet->sk_protocol,
                                     ntohs(inet_sk(inet)->sport));

        if (*errp < 0) {
                kfree(svsk);
                return NULL;
        }

        set_bit(SK_BUSY, &svsk->sk_flags);
        inet->sk_user_data = svsk;
        svsk->sk_sock = sock;
        svsk->sk_sk = inet;
        svsk->sk_ostate = inet->sk_state_change;
        svsk->sk_odata = inet->sk_data_ready;
        svsk->sk_owspace = inet->sk_write_space;
        svsk->sk_server = serv;
        svsk->sk_lastrecv = get_seconds();
        INIT_LIST_HEAD(&svsk->sk_deferred);
        INIT_LIST_HEAD(&svsk->sk_ready);
        mutex_init(&svsk->sk_mutex);

        /* Initialize the socket */
        if (sock->type == SOCK_DGRAM)
                svc_udp_init(svsk);
        else
                svc_tcp_init(svsk);

        spin_lock_bh(&serv->sv_lock);
        if (!pmap_register) {
                set_bit(SK_TEMP, &svsk->sk_flags);
                list_add(&svsk->sk_list, &serv->sv_tempsocks);
                serv->sv_tmpcnt++;
        } else {
                clear_bit(SK_TEMP, &svsk->sk_flags);
                list_add(&svsk->sk_list, &serv->sv_permsocks);
        }
        spin_unlock_bh(&serv->sv_lock);

        dprintk("svc: svc_setup_socket created %p (inet %p)\n",
                                svsk, svsk->sk_sk);

        clear_bit(SK_BUSY, &svsk->sk_flags);
        svc_sock_enqueue(svsk);
        return svsk;
}

int svc_addsock(struct svc_serv *serv,
                int fd,
                char *name_return,
                int *proto)
{
        int err = 0;
        struct socket *so = sockfd_lookup(fd, &err);
        struct svc_sock *svsk = NULL;

        if (!so)
                return err;
        if (so->sk->sk_family != AF_INET)
                err =  -EAFNOSUPPORT;
        else if (so->sk->sk_protocol != IPPROTO_TCP &&
            so->sk->sk_protocol != IPPROTO_UDP)
                err =  -EPROTONOSUPPORT;
        else if (so->state > SS_UNCONNECTED)
                err = -EISCONN;
        else {
                svsk = svc_setup_socket(serv, so, &err, 1);
                if (svsk)
                        err = 0;
        }
        if (err) {
                sockfd_put(so);
                return err;
        }
        if (proto) *proto = so->sk->sk_protocol;
        return one_sock_name(name_return, svsk);
}
EXPORT_SYMBOL_GPL(svc_addsock);

/*
 * Create socket for RPC service.
 */
static int
svc_create_socket(struct svc_serv *serv, int protocol, struct sockaddr_in *sin)
{
        struct svc_sock *svsk;
        struct socket   *sock;
        int             error;
        int             type;

        dprintk("svc: svc_create_socket(%s, %d, %u.%u.%u.%u:%d)\n",
                                serv->sv_program->pg_name, protocol,
                                NIPQUAD(sin->sin_addr.s_addr),
                                ntohs(sin->sin_port));

        if (protocol != IPPROTO_UDP && protocol != IPPROTO_TCP) {
                printk(KERN_WARNING "svc: only UDP and TCP "
                                "sockets supported\n");
                return -EINVAL;
        }
        type = (protocol == IPPROTO_UDP)? SOCK_DGRAM : SOCK_STREAM;

        if ((error = sock_create_kern(PF_INET, type, protocol, &sock)) < 0)
                return error;

        if (type == SOCK_STREAM)
                sock->sk->sk_reuse = 1; /* allow address reuse */
        error = kernel_bind(sock, (struct sockaddr *) sin,
                                        sizeof(*sin));
        if (error < 0)
                goto bummer;

        if (protocol == IPPROTO_TCP) {
                if ((error = kernel_listen(sock, 64)) < 0)
                        goto bummer;
        }

        if ((svsk = svc_setup_socket(serv, sock, &error, 1)) != NULL)
                return 0;

bummer:
        dprintk("svc: svc_create_socket error = %d\n", -error);
        sock_release(sock);
        return error;
}

/*
 * Remove a dead socket
 */
void
svc_delete_socket(struct svc_sock *svsk)
{
        struct svc_serv *serv;
        struct sock     *sk;

        dprintk("svc: svc_delete_socket(%p)\n", svsk);

        serv = svsk->sk_server;
        sk = svsk->sk_sk;

        sk->sk_state_change = svsk->sk_ostate;
        sk->sk_data_ready = svsk->sk_odata;
        sk->sk_write_space = svsk->sk_owspace;

        spin_lock_bh(&serv->sv_lock);

        list_del_init(&svsk->sk_list);
        list_del_init(&svsk->sk_ready);
        if (!test_and_set_bit(SK_DEAD, &svsk->sk_flags))
                if (test_bit(SK_TEMP, &svsk->sk_flags))
                        serv->sv_tmpcnt--;

        if (!svsk->sk_inuse) {
                spin_unlock_bh(&serv->sv_lock);
                if (svsk->sk_sock->file)
                        sockfd_put(svsk->sk_sock);
                else
                        sock_release(svsk->sk_sock);
                kfree(svsk);
        } else {
                spin_unlock_bh(&serv->sv_lock);
                dprintk(KERN_NOTICE "svc: server socket destroy delayed\n");
                /* svsk->sk_server = NULL; */
        }
}

/*
 * Make a socket for nfsd and lockd
 */
int
svc_makesock(struct svc_serv *serv, int protocol, unsigned short port)
{
        struct sockaddr_in      sin;

        dprintk("svc: creating socket proto = %d\n", protocol);
        sin.sin_family      = AF_INET;
        sin.sin_addr.s_addr = INADDR_ANY;
        sin.sin_port        = htons(port);
        return svc_create_socket(serv, protocol, &sin);
}

/*
 * Handle defer and revisit of requests 
 */

static void svc_revisit(struct cache_deferred_req *dreq, int too_many)
{
        struct svc_deferred_req *dr = container_of(dreq, struct svc_deferred_req, handle);
        struct svc_serv *serv = dreq->owner;
        struct svc_sock *svsk;

        if (too_many) {
                svc_sock_put(dr->svsk);
                kfree(dr);
                return;
        }
        dprintk("revisit queued\n");
        svsk = dr->svsk;
        dr->svsk = NULL;
        spin_lock_bh(&serv->sv_lock);
        list_add(&dr->handle.recent, &svsk->sk_deferred);
        spin_unlock_bh(&serv->sv_lock);
        set_bit(SK_DEFERRED, &svsk->sk_flags);
        svc_sock_enqueue(svsk);
        svc_sock_put(svsk);
}

static struct cache_deferred_req *
svc_defer(struct cache_req *req)
{
        struct svc_rqst *rqstp = container_of(req, struct svc_rqst, rq_chandle);
        int size = sizeof(struct svc_deferred_req) + (rqstp->rq_arg.len);
        struct svc_deferred_req *dr;

        if (rqstp->rq_arg.page_len)
                return NULL; /* if more than a page, give up FIXME */
        if (rqstp->rq_deferred) {
                dr = rqstp->rq_deferred;
                rqstp->rq_deferred = NULL;
        } else {
                int skip  = rqstp->rq_arg.len - rqstp->rq_arg.head[0].iov_len;
                /* FIXME maybe discard if size too large */
                dr = kmalloc(size, GFP_KERNEL);
                if (dr == NULL)
                        return NULL;

                dr->handle.owner = rqstp->rq_server;
                dr->prot = rqstp->rq_prot;
                dr->addr = rqstp->rq_addr;
                dr->daddr = rqstp->rq_daddr;
                dr->argslen = rqstp->rq_arg.len >> 2;
                memcpy(dr->args, rqstp->rq_arg.head[0].iov_base-skip, dr->argslen<<2);
        }
        spin_lock_bh(&rqstp->rq_server->sv_lock);
        rqstp->rq_sock->sk_inuse++;
        dr->svsk = rqstp->rq_sock;
        spin_unlock_bh(&rqstp->rq_server->sv_lock);

        dr->handle.revisit = svc_revisit;
        return &dr->handle;
}

/*
 * recv data from a deferred request into an active one
 */
static int svc_deferred_recv(struct svc_rqst *rqstp)
{
        struct svc_deferred_req *dr = rqstp->rq_deferred;

        rqstp->rq_arg.head[0].iov_base = dr->args;
        rqstp->rq_arg.head[0].iov_len = dr->argslen<<2;
        rqstp->rq_arg.page_len = 0;
        rqstp->rq_arg.len = dr->argslen<<2;
        rqstp->rq_prot        = dr->prot;
        rqstp->rq_addr        = dr->addr;
        rqstp->rq_daddr       = dr->daddr;
        return dr->argslen<<2;
}


static struct svc_deferred_req *svc_deferred_dequeue(struct svc_sock *svsk)
{
        struct svc_deferred_req *dr = NULL;
        struct svc_serv *serv = svsk->sk_server;
        
        if (!test_bit(SK_DEFERRED, &svsk->sk_flags))
                return NULL;
        spin_lock_bh(&serv->sv_lock);
        clear_bit(SK_DEFERRED, &svsk->sk_flags);
        if (!list_empty(&svsk->sk_deferred)) {
                dr = list_entry(svsk->sk_deferred.next,
                                struct svc_deferred_req,
                                handle.recent);
                list_del_init(&dr->handle.recent);
                set_bit(SK_DEFERRED, &svsk->sk_flags);
        }
        spin_unlock_bh(&serv->sv_lock);
        return dr;
}