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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/kernel.h>
#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 <linux/freezer.h>
#include <net/sock.h>
#include <net/checksum.h>
#include <net/ip.h>
#include <net/ipv6.h>
#include <net/tcp_states.h>
#include <asm/uaccess.h>
#include <asm/ioctls.h>

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

/* SMP locking strategy:
 *
 *    svc_pool->sp_lock protects most of the fields of that pool.
 *    svc_serv->sv_lock protects sv_tempsocks, sv_permsocks, sv_tmpcnt.
 *    when both need to be taken (rare), svc_serv->sv_lock is first.
 *    BKL protects svc_serv->sv_nrthread.
 *    svc_sock->sk_lock protects the svc_sock->sk_deferred list
 *             and the ->sk_info_authunix cache.
 *    svc_sock->sk_flags.SK_BUSY prevents a svc_sock being enqueued multiply.
 *
 *    Some flags can be set to certain values at any time
 *    providing that certain rules are followed:
 *
 *    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.
 *      sk_inuse contains a bias of '1' until SK_DEAD is set.
 *             so when sk_inuse hits zero, we know the socket is dead
 *             and no-one is using it.
 *      SK_DEAD can only be set while SK_BUSY is held which ensures
 *             no other thread will be using the socket or will try to
 *           set SK_DEAD.
 *
 */

#define RPCDBG_FACILITY RPCDBG_SVCSOCK


static struct svc_sock *svc_setup_socket(struct svc_serv *, struct socket *,
                               int *errp, int flags);
static void       svc_delete_socket(struct svc_sock *svsk);
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 void       svc_close_socket(struct svc_sock *svsk);

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);

/* apparently the "standard" is that clients close
 * idle connections after 5 minutes, servers after
 * 6 minutes
 *   http://www.connectathon.org/talks96/nfstcp.pdf
 */
static int svc_conn_age_period = 6*60;

#ifdef CONFIG_DEBUG_LOCK_ALLOC
static struct lock_class_key svc_key[2];
static struct lock_class_key svc_slock_key[2];

static inline void svc_reclassify_socket(struct socket *sock)
{
      struct sock *sk = sock->sk;
      BUG_ON(sock_owned_by_user(sk));
      switch (sk->sk_family) {
      case AF_INET:
            sock_lock_init_class_and_name(sk, "slock-AF_INET-NFSD",
                &svc_slock_key[0], "sk_lock-AF_INET-NFSD", &svc_key[0]);
            break;

      case AF_INET6:
            sock_lock_init_class_and_name(sk, "slock-AF_INET6-NFSD",
                &svc_slock_key[1], "sk_lock-AF_INET6-NFSD", &svc_key[1]);
            break;

      default:
            BUG();
      }
}
#else
static inline void svc_reclassify_socket(struct socket *sock)
{
}
#endif

static char *__svc_print_addr(struct sockaddr *addr, char *buf, size_t len)
{
      switch (addr->sa_family) {
      case AF_INET:
            snprintf(buf, len, "%u.%u.%u.%u, port=%u",
                  NIPQUAD(((struct sockaddr_in *) addr)->sin_addr),
                  ntohs(((struct sockaddr_in *) addr)->sin_port));
            break;

      case AF_INET6:
            snprintf(buf, len, "%x:%x:%x:%x:%x:%x:%x:%x, port=%u",
                  NIP6(((struct sockaddr_in6 *) addr)->sin6_addr),
                  ntohs(((struct sockaddr_in6 *) addr)->sin6_port));
            break;

      default:
            snprintf(buf, len, "unknown address type: %d", addr->sa_family);
            break;
      }
      return buf;
}

/**
 * svc_print_addr - Format rq_addr field for printing
 * @rqstp: svc_rqst struct containing address to print
 * @buf: target buffer for formatted address
 * @len: length of target buffer
 *
 */
char *svc_print_addr(struct svc_rqst *rqstp, char *buf, size_t len)
{
      return __svc_print_addr(svc_addr(rqstp), buf, len);
}
EXPORT_SYMBOL_GPL(svc_print_addr);

/*
 * Queue up an idle server thread.  Must have pool->sp_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 pollute
 * the cache.
 */
static inline void
svc_thread_enqueue(struct svc_pool *pool, struct svc_rqst *rqstp)
{
      list_add(&rqstp->rq_list, &pool->sp_threads);
}

/*
 * Dequeue an nfsd thread.  Must have pool->sp_lock held.
 */
static inline void
svc_thread_dequeue(struct svc_pool *pool, 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_pool *pool;
      struct svc_rqst   *rqstp;
      int cpu;

      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;

      cpu = get_cpu();
      pool = svc_pool_for_cpu(svsk->sk_server, cpu);
      put_cpu();

      spin_lock_bh(&pool->sp_lock);

      if (!list_empty(&pool->sp_threads) &&
          !list_empty(&pool->sp_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;
      }

      /* 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.  We update SK_BUSY atomically because
       * it also guards against trying to enqueue the svc_sock twice.
       */
      if (test_and_set_bit(SK_BUSY, &svsk->sk_flags)) {
            /* Don't enqueue socket while already enqueued */
            dprintk("svc: socket %p busy, not enqueued\n", svsk->sk_sk);
            goto out_unlock;
      }
      BUG_ON(svsk->sk_pool != NULL);
      svsk->sk_pool = pool;

      set_bit(SOCK_NOSPACE, &svsk->sk_sock->flags);
      if (((atomic_read(&svsk->sk_reserved) + serv->sv_max_mesg)*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, atomic_read(&svsk->sk_reserved)+serv->sv_max_mesg,
                  svc_sock_wspace(svsk));
            svsk->sk_pool = NULL;
            clear_bit(SK_BUSY, &svsk->sk_flags);
            goto out_unlock;
      }
      clear_bit(SOCK_NOSPACE, &svsk->sk_sock->flags);


      if (!list_empty(&pool->sp_threads)) {
            rqstp = list_entry(pool->sp_threads.next,
                           struct svc_rqst,
                           rq_list);
            dprintk("svc: socket %p served by daemon %p\n",
                  svsk->sk_sk, rqstp);
            svc_thread_dequeue(pool, 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;
            atomic_inc(&svsk->sk_inuse);
            rqstp->rq_reserved = serv->sv_max_mesg;
            atomic_add(rqstp->rq_reserved, &svsk->sk_reserved);
            BUG_ON(svsk->sk_pool != pool);
            wake_up(&rqstp->rq_wait);
      } else {
            dprintk("svc: socket %p put into queue\n", svsk->sk_sk);
            list_add_tail(&svsk->sk_ready, &pool->sp_sockets);
            BUG_ON(svsk->sk_pool != pool);
      }

out_unlock:
      spin_unlock_bh(&pool->sp_lock);
}

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

      if (list_empty(&pool->sp_sockets))
            return NULL;

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

      dprintk("svc: socket %p dequeued, inuse=%d\n",
            svsk->sk_sk, atomic_read(&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)
{
      svsk->sk_pool = NULL;
      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;
            atomic_sub((rqstp->rq_reserved - space), &svsk->sk_reserved);
            rqstp->rq_reserved = space;

            svc_sock_enqueue(svsk);
      }
}

/*
 * Release a socket after use.
 */
static inline void
svc_sock_put(struct svc_sock *svsk)
{
      if (atomic_dec_and_test(&svsk->sk_inuse)) {
            BUG_ON(! test_bit(SK_DEAD, &svsk->sk_flags));

            dprintk("svc: releasing dead socket\n");
            if (svsk->sk_sock->file)
                  sockfd_put(svsk->sk_sock);
            else
                  sock_release(svsk->sk_sock);
            if (svsk->sk_info_authunix != NULL)
                  svcauth_unix_info_release(svsk->sk_info_authunix);
            kfree(svsk);
      }
}

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

      svc_release_skb(rqstp);

      svc_free_res_pages(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
 * This really only makes sense for services like lockd
 * which have exactly one thread anyway.
 */
void
svc_wake_up(struct svc_serv *serv)
{
      struct svc_rqst   *rqstp;
      unsigned int i;
      struct svc_pool *pool;

      for (i = 0; i < serv->sv_nrpools; i++) {
            pool = &serv->sv_pools[i];

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

union svc_pktinfo_u {
      struct in_pktinfo pkti;
      struct in6_pktinfo pkti6;
};
#define SVC_PKTINFO_SPACE \
      CMSG_SPACE(sizeof(union svc_pktinfo_u))

static void svc_set_cmsg_data(struct svc_rqst *rqstp, struct cmsghdr *cmh)
{
      switch (rqstp->rq_sock->sk_sk->sk_family) {
      case AF_INET: {
                  struct in_pktinfo *pki = CMSG_DATA(cmh);

                  cmh->cmsg_level = SOL_IP;
                  cmh->cmsg_type = IP_PKTINFO;
                  pki->ipi_ifindex = 0;
                  pki->ipi_spec_dst.s_addr = rqstp->rq_daddr.addr.s_addr;
                  cmh->cmsg_len = CMSG_LEN(sizeof(*pki));
            }
            break;

      case AF_INET6: {
                  struct in6_pktinfo *pki = CMSG_DATA(cmh);

                  cmh->cmsg_level = SOL_IPV6;
                  cmh->cmsg_type = IPV6_PKTINFO;
                  pki->ipi6_ifindex = 0;
                  ipv6_addr_copy(&pki->ipi6_addr,
                              &rqstp->rq_daddr.addr6);
                  cmh->cmsg_len = CMSG_LEN(sizeof(*pki));
            }
            break;
      }
      return;
}

/*
 * 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;
      union {
            struct cmsghdr    hdr;
            long        all[SVC_PKTINFO_SPACE / sizeof(long)];
      } buffer;
      struct cmsghdr *cmh = &buffer.hdr;
      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;
      char        buf[RPC_MAX_ADDRBUFLEN];

      slen = xdr->len;

      if (rqstp->rq_prot == IPPROTO_UDP) {
            struct msghdr msg = {
                  .msg_name   = &rqstp->rq_addr,
                  .msg_namelen      = rqstp->rq_addrlen,
                  .msg_control      = cmh,
                  .msg_controllen   = sizeof(buffer),
                  .msg_flags  = MSG_MORE,
            };

            svc_set_cmsg_data(rqstp, cmh);

            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[0],
                                   ((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 %s)\n",
            rqstp->rq_sock, xdr->head[0].iov_base, xdr->head[0].iov_len,
            xdr->len, len, svc_print_addr(rqstp, buf, sizeof(buf)));

      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_bh(&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_bh(&serv->sv_lock);
      if (closesk)
            /* Should unregister with portmap, but you cannot
             * unregister just one protocol...
             */
            svc_close_socket(closesk);
      else if (toclose)
            return -ENOENT;
      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 svc_sock *svsk = rqstp->rq_sock;
      struct msghdr msg = {
            .msg_flags  = MSG_DONTWAIT,
      };
      struct sockaddr *sin;
      int len;

      len = kernel_recvmsg(svsk->sk_sock, &msg, iov, nr, buflen,
                        msg.msg_flags);

      /* sock_recvmsg doesn't fill in the name/namelen, so we must..
       */
      memcpy(&rqstp->rq_addr, &svsk->sk_remote, svsk->sk_remotelen);
      rqstp->rq_addrlen = svsk->sk_remotelen;

      /* Destination address in request is needed for binding the
       * source address in RPC callbacks later.
       */
      sin = (struct sockaddr *)&svsk->sk_local;
      switch (sin->sa_family) {
      case AF_INET:
            rqstp->rq_daddr.addr = ((struct sockaddr_in *)sin)->sin_addr;
            break;
      case AF_INET6:
            rqstp->rq_daddr.addr6 = ((struct sockaddr_in6 *)sin)->sin6_addr;
            break;
      }

      dprintk("svc: socket %p recvfrom(%p, %Zu) = %d\n",
            svsk, 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);
      }
}

static inline void svc_udp_get_dest_address(struct svc_rqst *rqstp,
                                  struct cmsghdr *cmh)
{
      switch (rqstp->rq_sock->sk_sk->sk_family) {
      case AF_INET: {
            struct in_pktinfo *pki = CMSG_DATA(cmh);
            rqstp->rq_daddr.addr.s_addr = pki->ipi_spec_dst.s_addr;
            break;
            }
      case AF_INET6: {
            struct in6_pktinfo *pki = CMSG_DATA(cmh);
            ipv6_addr_copy(&rqstp->rq_daddr.addr6, &pki->ipi6_addr);
            break;
            }
      }
}

/*
 * 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;
      union {
            struct cmsghdr    hdr;
            long        all[SVC_PKTINFO_SPACE / sizeof(long)];
      } buffer;
      struct cmsghdr *cmh = &buffer.hdr;
      int         err, len;
      struct msghdr msg = {
            .msg_name = svc_addr(rqstp),
            .msg_control = cmh,
            .msg_controllen = sizeof(buffer),
            .msg_flags = MSG_DONTWAIT,
      };

      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.  We count all threads
           * rather than threads in a particular pool, which
           * provides an upper bound on the number of threads
           * which will access the socket.
           */
          svc_sock_setbufsize(svsk->sk_sock,
                        (serv->sv_nrthreads+3) * serv->sv_max_mesg,
                        (serv->sv_nrthreads+3) * serv->sv_max_mesg);

      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;
      }

      clear_bit(SK_DATA, &svsk->sk_flags);
      skb = NULL;
      err = kernel_recvmsg(svsk->sk_sock, &msg, NULL,
                       0, 0, MSG_PEEK | MSG_DONTWAIT);
      if (err >= 0)
            skb = skb_recv_datagram(svsk->sk_sk, 0, 1, &err);

      if (skb == NULL) {
            if (err != -EAGAIN) {
                  /* possibly an icmp error */
                  dprintk("svc: recvfrom returned error %d\n", -err);
                  set_bit(SK_DATA, &svsk->sk_flags);
            }
            svc_sock_received(svsk);
            return -EAGAIN;
      }
      rqstp->rq_addrlen = sizeof(rqstp->rq_addr);
      if (skb->tstamp.tv64 == 0) {
            skb->tstamp = ktime_get_real();
            /* Don't enable netstamp, sunrpc doesn't
               need that much accuracy */
      }
      svsk->sk_sk->sk_stamp = skb->tstamp;
      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;

      if (cmh->cmsg_level != IPPROTO_IP ||
          cmh->cmsg_type != IP_PKTINFO) {
            if (net_ratelimit())
                  printk("rpcsvc: received unknown control message:"
                         "%d/%d\n",
                         cmh->cmsg_level, cmh->cmsg_type);
            skb_free_datagram(svsk->sk_sk, skb);
            return 0;
      }
      svc_udp_get_dest_address(rqstp, cmh);

      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;
            rqstp->rq_respages = rqstp->rq_pages+1;
      } else {
            rqstp->rq_arg.page_len = len - rqstp->rq_arg.head[0].iov_len;
            rqstp->rq_respages = rqstp->rq_pages + 1 +
                  DIV_ROUND_UP(rqstp->rq_arg.page_len, 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)
{
      int one = 1;
      mm_segment_t oldfs;

      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_max_mesg,
                      3 * svsk->sk_server->sv_max_mesg);

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

      oldfs = get_fs();
      set_fs(KERNEL_DS);
      /* make sure we get destination address info */
      svsk->sk_sock->ops->setsockopt(svsk->sk_sock, IPPROTO_IP, IP_PKTINFO,
                               (char __user *)&one, sizeof(one));
      set_fs(oldfs);
}

/*
 * 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);
}

static inline int svc_port_is_privileged(struct sockaddr *sin)
{
      switch (sin->sa_family) {
      case AF_INET:
            return ntohs(((struct sockaddr_in *)sin)->sin_port)
                  < PROT_SOCK;
      case AF_INET6:
            return ntohs(((struct sockaddr_in6 *)sin)->sin6_port)
                  < PROT_SOCK;
      default:
            return 0;
      }
}

/*
 * Accept a TCP connection
 */
static void
svc_tcp_accept(struct svc_sock *svsk)
{
      struct sockaddr_storage addr;
      struct sockaddr   *sin = (struct sockaddr *) &addr;
      struct svc_serv   *serv = svsk->sk_server;
      struct socket     *sock = svsk->sk_sock;
      struct socket     *newsock;
      struct svc_sock   *newsvsk;
      int         err, slen;
      char        buf[RPC_MAX_ADDRBUFLEN];

      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);

      err = kernel_getpeername(newsock, 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 encryption, the IP of the host won't
       * tell us anything.  For now just warn about unpriv connections.
       */
      if (!svc_port_is_privileged(sin)) {
            dprintk(KERN_WARNING
                  "%s: connect from unprivileged port: %s\n",
                  serv->sv_name,
                  __svc_print_addr(sin, buf, sizeof(buf)));
      }
      dprintk("%s: connect from %s\n", serv->sv_name,
            __svc_print_addr(sin, buf, sizeof(buf)));

      /* 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,
                         (SVC_SOCK_ANONYMOUS | SVC_SOCK_TEMPORARY))))
            goto failed;
      memcpy(&newsvsk->sk_remote, sin, slen);
      newsvsk->sk_remotelen = slen;
      err = kernel_getsockname(newsock, sin, &slen);
      if (unlikely(err < 0)) {
            dprintk("svc_tcp_accept: kernel_getsockname error %d\n", -err);
            slen = offsetof(struct sockaddr, sa_data);
      }
      memcpy(&newsvsk->sk_local, sin, slen);

      svc_sock_received(newsvsk);

      /* 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 %s\n",
                               serv->sv_name, __svc_print_addr(sin,
                                          buf, sizeof(buf)));
                  }
                  /*
                   * 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);
                  atomic_inc(&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;
      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 (svsk->sk_sk->sk_state == TCP_LISTEN) {
            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.
             *
             * We count all threads rather than threads in a
             * particular pool, which provides an upper bound
             * on the number of threads which will access the socket.
             *
             * 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_max_mesg,
                            3 * serv->sv_max_mesg);

      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. */
                  if (net_ratelimit())
                        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_max_mesg) {
                  if (net_ratelimit())
                        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 = rqstp->rq_vec;
      vec[0] = rqstp->rq_arg.head[0];
      vlen = PAGE_SIZE;
      pnum = 1;
      while (vlen < len) {
            vec[pnum].iov_base = page_address(rqstp->rq_pages[pnum]);
            vec[pnum].iov_len = PAGE_SIZE;
            pnum++;
            vlen += PAGE_SIZE;
      }
      rqstp->rq_respages = &rqstp->rq_pages[pnum];

      /* 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);
            set_bit(SK_CLOSE, &rqstp->rq_sock->sk_flags);
            svc_sock_enqueue(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_max_mesg,
                            3 * svsk->sk_server->sv_max_mesg);

            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.  This code is carefully
 * organised not to touch any cachelines in the shared svc_serv
 * structure, only cachelines in the local svc_pool.
 */
int
svc_recv(struct svc_rqst *rqstp, long timeout)
{
      struct svc_sock         *svsk = NULL;
      struct svc_serv         *serv = rqstp->rq_server;
      struct svc_pool         *pool = rqstp->rq_pool;
      int               len, i;
      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);


      /* now allocate needed pages.  If we get a failure, sleep briefly */
      pages = (serv->sv_max_mesg + PAGE_SIZE) / PAGE_SIZE;
      for (i=0; i < pages ; i++)
            while (rqstp->rq_pages[i] == NULL) {
                  struct page *p = alloc_page(GFP_KERNEL);
                  if (!p)
                        schedule_timeout_uninterruptible(msecs_to_jiffies(500));
                  rqstp->rq_pages[i] = p;
            }
      rqstp->rq_pages[i++] = NULL; /* this might be seen in nfs_read_actor */
      BUG_ON(pages >= RPCSVC_MAXPAGES);

      /* 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_pages[0]);
      arg->head[0].iov_len = PAGE_SIZE;
      arg->pages = rqstp->rq_pages + 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(&pool->sp_lock);
      if ((svsk = svc_sock_dequeue(pool)) != NULL) {
            rqstp->rq_sock = svsk;
            atomic_inc(&svsk->sk_inuse);
            rqstp->rq_reserved = serv->sv_max_mesg;
            atomic_add(rqstp->rq_reserved, &svsk->sk_reserved);
      } else {
            /* No data pending. Go to sleep */
            svc_thread_enqueue(pool, 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(&pool->sp_lock);

            schedule_timeout(timeout);

            try_to_freeze();

            spin_lock_bh(&pool->sp_lock);
            remove_wait_queue(&rqstp->rq_wait, &wait);

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

      dprintk("svc: server %p, pool %u, socket %p, inuse=%d\n",
             rqstp, pool->sp_id, svsk, atomic_read(&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();
      clear_bit(SK_OLD, &svsk->sk_flags);

      rqstp->rq_secure = svc_port_is_privileged(svc_addr(rqstp));
      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;
}

/*
 * Timer function to close old temporary sockets, using
 * a mark-and-sweep algorithm.
 */
static void
svc_age_temp_sockets(unsigned long closure)
{
      struct svc_serv *serv = (struct svc_serv *)closure;
      struct svc_sock *svsk;
      struct list_head *le, *next;
      LIST_HEAD(to_be_aged);

      dprintk("svc_age_temp_sockets\n");

      if (!spin_trylock_bh(&serv->sv_lock)) {
            /* busy, try again 1 sec later */
            dprintk("svc_age_temp_sockets: busy\n");
            mod_timer(&serv->sv_temptimer, jiffies + HZ);
            return;
      }

      list_for_each_safe(le, next, &serv->sv_tempsocks) {
            svsk = list_entry(le, struct svc_sock, sk_list);

            if (!test_and_set_bit(SK_OLD, &svsk->sk_flags))
                  continue;
            if (atomic_read(&svsk->sk_inuse) > 1 || test_bit(SK_BUSY, &svsk->sk_flags))
                  continue;
            atomic_inc(&svsk->sk_inuse);
            list_move(le, &to_be_aged);
            set_bit(SK_CLOSE, &svsk->sk_flags);
            set_bit(SK_DETACHED, &svsk->sk_flags);
      }
      spin_unlock_bh(&serv->sv_lock);

      while (!list_empty(&to_be_aged)) {
            le = to_be_aged.next;
            /* fiddling the sk_list node is safe 'cos we're SK_DETACHED */
            list_del_init(le);
            svsk = list_entry(le, struct svc_sock, sk_list);

            dprintk("queuing svsk %p for closing, %lu seconds old\n",
                  svsk, get_seconds() - svsk->sk_lastrecv);

            /* a thread will dequeue and close it soon */
            svc_sock_enqueue(svsk);
            svc_sock_put(svsk);
      }

      mod_timer(&serv->sv_temptimer, jiffies + svc_conn_age_period * HZ);
}

/*
 * 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 flags)
{
      struct svc_sock   *svsk;
      struct sock *inet;
      int         pmap_register = !(flags & SVC_SOCK_ANONYMOUS);
      int         is_temporary = flags & SVC_SOCK_TEMPORARY;

      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;
      atomic_set(&svsk->sk_inuse, 1);
      svsk->sk_lastrecv = get_seconds();
      spin_lock_init(&svsk->sk_lock);
      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 (is_temporary) {
            set_bit(SK_TEMP, &svsk->sk_flags);
            list_add(&svsk->sk_list, &serv->sv_tempsocks);
            serv->sv_tmpcnt++;
            if (serv->sv_temptimer.function == NULL) {
                  /* setup timer to age temp sockets */
                  setup_timer(&serv->sv_temptimer, svc_age_temp_sockets,
                              (unsigned long)serv);
                  mod_timer(&serv->sv_temptimer,
                              jiffies + svc_conn_age_period * HZ);
            }
      } 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);

      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, SVC_SOCK_DEFAULTS);
            if (svsk) {
                  svc_sock_received(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 *sin, int len, int flags)
{
      struct svc_sock   *svsk;
      struct socket     *sock;
      int         error;
      int         type;
      char        buf[RPC_MAX_ADDRBUFLEN];

      dprintk("svc: svc_create_socket(%s, %d, %s)\n",
                  serv->sv_program->pg_name, protocol,
                  __svc_print_addr(sin, buf, sizeof(buf)));

      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;

      error = sock_create_kern(sin->sa_family, type, protocol, &sock);
      if (error < 0)
            return error;

      svc_reclassify_socket(sock);

      if (type == SOCK_STREAM)
            sock->sk->sk_reuse = 1;       /* allow address reuse */
      error = kernel_bind(sock, sin, len);
      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, flags)) != NULL) {
            svc_sock_received(svsk);
            return ntohs(inet_sk(svsk->sk_sk)->sport);
      }

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

/*
 * Remove a dead socket
 */
static 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);

      if (!test_and_set_bit(SK_DETACHED, &svsk->sk_flags))
            list_del_init(&svsk->sk_list);
      /*
       * We used to delete the svc_sock from whichever list
       * it's sk_ready node was on, but we don't actually
       * need to.  This is because the only time we're called
       * while still attached to a queue, the queue itself
       * is about to be destroyed (in svc_destroy).
       */
      if (!test_and_set_bit(SK_DEAD, &svsk->sk_flags)) {
            BUG_ON(atomic_read(&svsk->sk_inuse)<2);
            atomic_dec(&svsk->sk_inuse);
            if (test_bit(SK_TEMP, &svsk->sk_flags))
                  serv->sv_tmpcnt--;
      }

      spin_unlock_bh(&serv->sv_lock);
}

static void svc_close_socket(struct svc_sock *svsk)
{
      set_bit(SK_CLOSE, &svsk->sk_flags);
      if (test_and_set_bit(SK_BUSY, &svsk->sk_flags))
            /* someone else will have to effect the close */
            return;

      atomic_inc(&svsk->sk_inuse);
      svc_delete_socket(svsk);
      clear_bit(SK_BUSY, &svsk->sk_flags);
      svc_sock_put(svsk);
}

void svc_force_close_socket(struct svc_sock *svsk)
{
      set_bit(SK_CLOSE, &svsk->sk_flags);
      if (test_bit(SK_BUSY, &svsk->sk_flags)) {
            /* Waiting to be processed, but no threads left,
             * So just remove it from the waiting list
             */
            list_del_init(&svsk->sk_ready);
            clear_bit(SK_BUSY, &svsk->sk_flags);
      }
      svc_close_socket(svsk);
}

/**
 * svc_makesock - Make a socket for nfsd and lockd
 * @serv: RPC server structure
 * @protocol: transport protocol to use
 * @port: port to use
 * @flags: requested socket characteristics
 *
 */
int svc_makesock(struct svc_serv *serv, int protocol, unsigned short port,
                  int flags)
{
      struct sockaddr_in sin = {
            .sin_family       = AF_INET,
            .sin_addr.s_addr  = INADDR_ANY,
            .sin_port         = htons(port),
      };

      dprintk("svc: creating socket proto = %d\n", protocol);
      return svc_create_socket(serv, protocol, (struct sockaddr *) &sin,
                                          sizeof(sin), flags);
}

/*
 * 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_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(&svsk->sk_lock);
      list_add(&dr->handle.recent, &svsk->sk_deferred);
      spin_unlock(&svsk->sk_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;
            memcpy(&dr->addr, &rqstp->rq_addr, rqstp->rq_addrlen);
            dr->addrlen = rqstp->rq_addrlen;
            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);
      }
      atomic_inc(&rqstp->rq_sock->sk_inuse);
      dr->svsk = rqstp->rq_sock;

      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;
      memcpy(&rqstp->rq_addr, &dr->addr, dr->addrlen);
      rqstp->rq_addrlen     = dr->addrlen;
      rqstp->rq_daddr       = dr->daddr;
      rqstp->rq_respages    = rqstp->rq_pages;
      return dr->argslen<<2;
}


static struct svc_deferred_req *svc_deferred_dequeue(struct svc_sock *svsk)
{
      struct svc_deferred_req *dr = NULL;

      if (!test_bit(SK_DEFERRED, &svsk->sk_flags))
            return NULL;
      spin_lock(&svsk->sk_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(&svsk->sk_lock);
      return dr;
}

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