[NETFILTER]: {ip,ip6,arp}_tables: fix exponential worst-case search for loops

[pv_ops_mirror.git] / fs / dlm / lowcomms-tcp.c

/******************************************************************************
*******************************************************************************
**
**  Copyright (C) Sistina Software, Inc.  1997-2003  All rights reserved.
**  Copyright (C) 2004-2006 Red Hat, Inc.  All rights reserved.
**
**  This copyrighted material is made available to anyone wishing to use,
**  modify, copy, or redistribute it subject to the terms and conditions
**  of the GNU General Public License v.2.
**
*******************************************************************************
******************************************************************************/

/*
 * lowcomms.c
 *
 * This is the "low-level" comms layer.
 *
 * It is responsible for sending/receiving messages
 * from other nodes in the cluster.
 *
 * Cluster nodes are referred to by their nodeids. nodeids are
 * simply 32 bit numbers to the locking module - if they need to
 * be expanded for the cluster infrastructure then that is it's
 * responsibility. It is this layer's
 * responsibility to resolve these into IP address or
 * whatever it needs for inter-node communication.
 *
 * The comms level is two kernel threads that deal mainly with
 * the receiving of messages from other nodes and passing them
 * up to the mid-level comms layer (which understands the
 * message format) for execution by the locking core, and
 * a send thread which does all the setting up of connections
 * to remote nodes and the sending of data. Threads are not allowed
 * to send their own data because it may cause them to wait in times
 * of high load. Also, this way, the sending thread can collect together
 * messages bound for one node and send them in one block.
 *
 * I don't see any problem with the recv thread executing the locking
 * code on behalf of remote processes as the locking code is
 * short, efficient and never waits.
 *
 */


#include <asm/ioctls.h>
#include <net/sock.h>
#include <net/tcp.h>
#include <linux/pagemap.h>

#include "dlm_internal.h"
#include "lowcomms.h"
#include "midcomms.h"
#include "config.h"

struct cbuf {
        unsigned int base;
        unsigned int len;
        unsigned int mask;
};

#define NODE_INCREMENT 32
static void cbuf_add(struct cbuf *cb, int n)
{
        cb->len += n;
}

static int cbuf_data(struct cbuf *cb)
{
        return ((cb->base + cb->len) & cb->mask);
}

static void cbuf_init(struct cbuf *cb, int size)
{
        cb->base = cb->len = 0;
        cb->mask = size-1;
}

static void cbuf_eat(struct cbuf *cb, int n)
{
        cb->len  -= n;
        cb->base += n;
        cb->base &= cb->mask;
}

static bool cbuf_empty(struct cbuf *cb)
{
        return cb->len == 0;
}

/* Maximum number of incoming messages to process before
   doing a cond_resched()
*/
#define MAX_RX_MSG_COUNT 25

struct connection {
        struct socket *sock;    /* NULL if not connected */
        uint32_t nodeid;        /* So we know who we are in the list */
        struct rw_semaphore sock_sem; /* Stop connect races */
        struct list_head read_list;   /* On this list when ready for reading */
        struct list_head write_list;  /* On this list when ready for writing */
        struct list_head state_list;  /* On this list when ready to connect */
        unsigned long flags;    /* bit 1,2 = We are on the read/write lists */
#define CF_READ_PENDING 1
#define CF_WRITE_PENDING 2
#define CF_CONNECT_PENDING 3
#define CF_IS_OTHERCON 4
        struct list_head writequeue;  /* List of outgoing writequeue_entries */
        struct list_head listenlist;  /* List of allocated listening sockets */
        spinlock_t writequeue_lock;
        int (*rx_action) (struct connection *); /* What to do when active */
        struct page *rx_page;
        struct cbuf cb;
        int retries;
        atomic_t waiting_requests;
#define MAX_CONNECT_RETRIES 3
        struct connection *othercon;
};
#define sock2con(x) ((struct connection *)(x)->sk_user_data)

/* An entry waiting to be sent */
struct writequeue_entry {
        struct list_head list;
        struct page *page;
        int offset;
        int len;
        int end;
        int users;
        struct connection *con;
};

static struct sockaddr_storage dlm_local_addr;

/* Manage daemons */
static struct task_struct *recv_task;
static struct task_struct *send_task;

static wait_queue_t lowcomms_send_waitq_head;
static DECLARE_WAIT_QUEUE_HEAD(lowcomms_send_waitq);
static wait_queue_t lowcomms_recv_waitq_head;
static DECLARE_WAIT_QUEUE_HEAD(lowcomms_recv_waitq);

/* An array of pointers to connections, indexed by NODEID */
static struct connection **connections;
static DECLARE_MUTEX(connections_lock);
static kmem_cache_t *con_cache;
static int conn_array_size;

/* List of sockets that have reads pending */
static LIST_HEAD(read_sockets);
static DEFINE_SPINLOCK(read_sockets_lock);

/* List of sockets which have writes pending */
static LIST_HEAD(write_sockets);
static DEFINE_SPINLOCK(write_sockets_lock);

/* List of sockets which have connects pending */
static LIST_HEAD(state_sockets);
static DEFINE_SPINLOCK(state_sockets_lock);

static struct connection *nodeid2con(int nodeid, gfp_t allocation)
{
        struct connection *con = NULL;

        down(&connections_lock);
        if (nodeid >= conn_array_size) {
                int new_size = nodeid + NODE_INCREMENT;
                struct connection **new_conns;

                new_conns = kzalloc(sizeof(struct connection *) *
                                    new_size, allocation);
                if (!new_conns)
                        goto finish;

                memcpy(new_conns, connections,  sizeof(struct connection *) * conn_array_size);
                conn_array_size = new_size;
                kfree(connections);
                connections = new_conns;

        }

        con = connections[nodeid];
        if (con == NULL && allocation) {
                con = kmem_cache_zalloc(con_cache, allocation);
                if (!con)
                        goto finish;

                con->nodeid = nodeid;
                init_rwsem(&con->sock_sem);
                INIT_LIST_HEAD(&con->writequeue);
                spin_lock_init(&con->writequeue_lock);

                connections[nodeid] = con;
        }

finish:
        up(&connections_lock);
        return con;
}

/* Data available on socket or listen socket received a connect */
static void lowcomms_data_ready(struct sock *sk, int count_unused)
{
        struct connection *con = sock2con(sk);

        atomic_inc(&con->waiting_requests);
        if (test_and_set_bit(CF_READ_PENDING, &con->flags))
                return;

        spin_lock_bh(&read_sockets_lock);
        list_add_tail(&con->read_list, &read_sockets);
        spin_unlock_bh(&read_sockets_lock);

        wake_up_interruptible(&lowcomms_recv_waitq);
}

static void lowcomms_write_space(struct sock *sk)
{
        struct connection *con = sock2con(sk);

        if (test_and_set_bit(CF_WRITE_PENDING, &con->flags))
                return;

        spin_lock_bh(&write_sockets_lock);
        list_add_tail(&con->write_list, &write_sockets);
        spin_unlock_bh(&write_sockets_lock);

        wake_up_interruptible(&lowcomms_send_waitq);
}

static inline void lowcomms_connect_sock(struct connection *con)
{
        if (test_and_set_bit(CF_CONNECT_PENDING, &con->flags))
                return;

        spin_lock_bh(&state_sockets_lock);
        list_add_tail(&con->state_list, &state_sockets);
        spin_unlock_bh(&state_sockets_lock);

        wake_up_interruptible(&lowcomms_send_waitq);
}

static void lowcomms_state_change(struct sock *sk)
{
        if (sk->sk_state == TCP_ESTABLISHED)
                lowcomms_write_space(sk);
}

/* Make a socket active */
static int add_sock(struct socket *sock, struct connection *con)
{
        con->sock = sock;

        /* Install a data_ready callback */
        con->sock->sk->sk_data_ready = lowcomms_data_ready;
        con->sock->sk->sk_write_space = lowcomms_write_space;
        con->sock->sk->sk_state_change = lowcomms_state_change;

        return 0;
}

/* Add the port number to an IP6 or 4 sockaddr and return the address
   length */
static void make_sockaddr(struct sockaddr_storage *saddr, uint16_t port,
                          int *addr_len)
{
        saddr->ss_family =  dlm_local_addr.ss_family;
        if (saddr->ss_family == AF_INET) {
                struct sockaddr_in *in4_addr = (struct sockaddr_in *)saddr;
                in4_addr->sin_port = cpu_to_be16(port);
                *addr_len = sizeof(struct sockaddr_in);
        } else {
                struct sockaddr_in6 *in6_addr = (struct sockaddr_in6 *)saddr;
                in6_addr->sin6_port = cpu_to_be16(port);
                *addr_len = sizeof(struct sockaddr_in6);
        }
}

/* Close a remote connection and tidy up */
static void close_connection(struct connection *con, bool and_other)
{
        down_write(&con->sock_sem);

        if (con->sock) {
                sock_release(con->sock);
                con->sock = NULL;
        }
        if (con->othercon && and_other) {
                /* Will only re-enter once. */
                close_connection(con->othercon, false);
        }
        if (con->rx_page) {
                __free_page(con->rx_page);
                con->rx_page = NULL;
        }
        con->retries = 0;
        up_write(&con->sock_sem);
}

/* Data received from remote end */
static int receive_from_sock(struct connection *con)
{
        int ret = 0;
        struct msghdr msg;
        struct iovec iov[2];
        mm_segment_t fs;
        unsigned len;
        int r;
        int call_again_soon = 0;

        down_read(&con->sock_sem);

        if (con->sock == NULL)
                goto out;
        if (con->rx_page == NULL) {
                /*
                 * This doesn't need to be atomic, but I think it should
                 * improve performance if it is.
                 */
                con->rx_page = alloc_page(GFP_ATOMIC);
                if (con->rx_page == NULL)
                        goto out_resched;
                cbuf_init(&con->cb, PAGE_CACHE_SIZE);
        }

        msg.msg_control = NULL;
        msg.msg_controllen = 0;
        msg.msg_iovlen = 1;
        msg.msg_iov = iov;
        msg.msg_name = NULL;
        msg.msg_namelen = 0;
        msg.msg_flags = 0;

        /*
         * iov[0] is the bit of the circular buffer between the current end
         * point (cb.base + cb.len) and the end of the buffer.
         */
        iov[0].iov_len = con->cb.base - cbuf_data(&con->cb);
        iov[0].iov_base = page_address(con->rx_page) + cbuf_data(&con->cb);
        iov[1].iov_len = 0;

        /*
         * iov[1] is the bit of the circular buffer between the start of the
         * buffer and the start of the currently used section (cb.base)
         */
        if (cbuf_data(&con->cb) >= con->cb.base) {
                iov[0].iov_len = PAGE_CACHE_SIZE - cbuf_data(&con->cb);
                iov[1].iov_len = con->cb.base;
                iov[1].iov_base = page_address(con->rx_page);
                msg.msg_iovlen = 2;
        }
        len = iov[0].iov_len + iov[1].iov_len;

        fs = get_fs();
        set_fs(get_ds());
        r = ret = sock_recvmsg(con->sock, &msg, len,
                               MSG_DONTWAIT | MSG_NOSIGNAL);
        set_fs(fs);

        if (ret <= 0)
                goto out_close;
        if (ret == len)
                call_again_soon = 1;
        cbuf_add(&con->cb, ret);
        ret = dlm_process_incoming_buffer(con->nodeid,
                                          page_address(con->rx_page),
                                          con->cb.base, con->cb.len,
                                          PAGE_CACHE_SIZE);
        if (ret == -EBADMSG) {
                printk(KERN_INFO "dlm: lowcomms: addr=%p, base=%u, len=%u, "
                       "iov_len=%u, iov_base[0]=%p, read=%d\n",
                       page_address(con->rx_page), con->cb.base, con->cb.len,
                       len, iov[0].iov_base, r);
        }
        if (ret < 0)
                goto out_close;
        cbuf_eat(&con->cb, ret);

        if (cbuf_empty(&con->cb) && !call_again_soon) {
                __free_page(con->rx_page);
                con->rx_page = NULL;
        }

out:
        if (call_again_soon)
                goto out_resched;
        up_read(&con->sock_sem);
        return 0;

out_resched:
        lowcomms_data_ready(con->sock->sk, 0);
        up_read(&con->sock_sem);
        cond_resched();
        return 0;

out_close:
        up_read(&con->sock_sem);
        if (ret != -EAGAIN && !test_bit(CF_IS_OTHERCON, &con->flags)) {
                close_connection(con, false);
                /* Reconnect when there is something to send */
        }

        return ret;
}

/* Listening socket is busy, accept a connection */
static int accept_from_sock(struct connection *con)
{
        int result;
        struct sockaddr_storage peeraddr;
        struct socket *newsock;
        int len;
        int nodeid;
        struct connection *newcon;

        memset(&peeraddr, 0, sizeof(peeraddr));
        result = sock_create_kern(dlm_local_addr.ss_family, SOCK_STREAM,
                                  IPPROTO_TCP, &newsock);
        if (result < 0)
                return -ENOMEM;

        down_read(&con->sock_sem);

        result = -ENOTCONN;
        if (con->sock == NULL)
                goto accept_err;

        newsock->type = con->sock->type;
        newsock->ops = con->sock->ops;

        result = con->sock->ops->accept(con->sock, newsock, O_NONBLOCK);
        if (result < 0)
                goto accept_err;

        /* Get the connected socket's peer */
        memset(&peeraddr, 0, sizeof(peeraddr));
        if (newsock->ops->getname(newsock, (struct sockaddr *)&peeraddr,
                                  &len, 2)) {
                result = -ECONNABORTED;
                goto accept_err;
        }

        /* Get the new node's NODEID */
        make_sockaddr(&peeraddr, 0, &len);
        if (dlm_addr_to_nodeid(&peeraddr, &nodeid)) {
                printk("dlm: connect from non cluster node\n");
                sock_release(newsock);
                up_read(&con->sock_sem);
                return -1;
        }

        log_print("got connection from %d", nodeid);

        /*  Check to see if we already have a connection to this node. This
         *  could happen if the two nodes initiate a connection at roughly
         *  the same time and the connections cross on the wire.
         * TEMPORARY FIX:
         *  In this case we store the incoming one in "othercon"
         */
        newcon = nodeid2con(nodeid, GFP_KERNEL);
        if (!newcon) {
                result = -ENOMEM;
                goto accept_err;
        }
        down_write(&newcon->sock_sem);
        if (newcon->sock) {
                struct connection *othercon = newcon->othercon;

                if (!othercon) {
                        othercon = kmem_cache_zalloc(con_cache, GFP_KERNEL);
                        if (!othercon) {
                                printk("dlm: failed to allocate incoming socket\n");
                                up_write(&newcon->sock_sem);
                                result = -ENOMEM;
                                goto accept_err;
                        }
                        othercon->nodeid = nodeid;
                        othercon->rx_action = receive_from_sock;
                        init_rwsem(&othercon->sock_sem);
                        set_bit(CF_IS_OTHERCON, &othercon->flags);
                        newcon->othercon = othercon;
                }
                othercon->sock = newsock;
                newsock->sk->sk_user_data = othercon;
                add_sock(newsock, othercon);
        }
        else {
                newsock->sk->sk_user_data = newcon;
                newcon->rx_action = receive_from_sock;
                add_sock(newsock, newcon);

        }

        up_write(&newcon->sock_sem);

        /*
         * Add it to the active queue in case we got data
         * beween processing the accept adding the socket
         * to the read_sockets list
         */
        lowcomms_data_ready(newsock->sk, 0);
        up_read(&con->sock_sem);

        return 0;

accept_err:
        up_read(&con->sock_sem);
        sock_release(newsock);

        if (result != -EAGAIN)
                printk("dlm: error accepting connection from node: %d\n", result);
        return result;
}

/* Connect a new socket to its peer */
static void connect_to_sock(struct connection *con)
{
        int result = -EHOSTUNREACH;
        struct sockaddr_storage saddr;
        int addr_len;
        struct socket *sock;

        if (con->nodeid == 0) {
                log_print("attempt to connect sock 0 foiled");
                return;
        }

        down_write(&con->sock_sem);
        if (con->retries++ > MAX_CONNECT_RETRIES)
                goto out;

        /* Some odd races can cause double-connects, ignore them */
        if (con->sock) {
                result = 0;
                goto out;
        }

        /* Create a socket to communicate with */
        result = sock_create_kern(dlm_local_addr.ss_family, SOCK_STREAM,
                                  IPPROTO_TCP, &sock);
        if (result < 0)
                goto out_err;

        memset(&saddr, 0, sizeof(saddr));
        if (dlm_nodeid_to_addr(con->nodeid, &saddr))
                goto out_err;

        sock->sk->sk_user_data = con;
        con->rx_action = receive_from_sock;

        make_sockaddr(&saddr, dlm_config.tcp_port, &addr_len);

        add_sock(sock, con);

        log_print("connecting to %d", con->nodeid);
        result =
                sock->ops->connect(sock, (struct sockaddr *)&saddr, addr_len,
                                   O_NONBLOCK);
        if (result == -EINPROGRESS)
                result = 0;
        if (result == 0)
                goto out;

out_err:
        if (con->sock) {
                sock_release(con->sock);
                con->sock = NULL;
        }
        /*
         * Some errors are fatal and this list might need adjusting. For other
         * errors we try again until the max number of retries is reached.
         */
        if (result != -EHOSTUNREACH && result != -ENETUNREACH &&
            result != -ENETDOWN && result != EINVAL
            && result != -EPROTONOSUPPORT) {
                lowcomms_connect_sock(con);
                result = 0;
        }
out:
        up_write(&con->sock_sem);
        return;
}

static struct socket *create_listen_sock(struct connection *con,
                                         struct sockaddr_storage *saddr)
{
        struct socket *sock = NULL;
        mm_segment_t fs;
        int result = 0;
        int one = 1;
        int addr_len;

        if (dlm_local_addr.ss_family == AF_INET)
                addr_len = sizeof(struct sockaddr_in);
        else
                addr_len = sizeof(struct sockaddr_in6);

        /* Create a socket to communicate with */
        result = sock_create_kern(dlm_local_addr.ss_family, SOCK_STREAM, IPPROTO_TCP, &sock);
        if (result < 0) {
                printk("dlm: Can't create listening comms socket\n");
                goto create_out;
        }

        fs = get_fs();
        set_fs(get_ds());
        result = sock_setsockopt(sock, SOL_SOCKET, SO_REUSEADDR,
                                 (char *)&one, sizeof(one));
        set_fs(fs);
        if (result < 0) {
                printk("dlm: Failed to set SO_REUSEADDR on socket: result=%d\n",
                       result);
        }
        sock->sk->sk_user_data = con;
        con->rx_action = accept_from_sock;
        con->sock = sock;

        /* Bind to our port */
        make_sockaddr(saddr, dlm_config.tcp_port, &addr_len);
        result = sock->ops->bind(sock, (struct sockaddr *) saddr, addr_len);
        if (result < 0) {
                printk("dlm: Can't bind to port %d\n", dlm_config.tcp_port);
                sock_release(sock);
                sock = NULL;
                con->sock = NULL;
                goto create_out;
        }

        fs = get_fs();
        set_fs(get_ds());

        result = sock_setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE,
                                 (char *)&one, sizeof(one));
        set_fs(fs);
        if (result < 0) {
                printk("dlm: Set keepalive failed: %d\n", result);
        }

        result = sock->ops->listen(sock, 5);
        if (result < 0) {
                printk("dlm: Can't listen on port %d\n", dlm_config.tcp_port);
                sock_release(sock);
                sock = NULL;
                goto create_out;
        }

create_out:
        return sock;
}


/* Listen on all interfaces */
static int listen_for_all(void)
{
        struct socket *sock = NULL;
        struct connection *con = nodeid2con(0, GFP_KERNEL);
        int result = -EINVAL;

        /* We don't support multi-homed hosts */
        set_bit(CF_IS_OTHERCON, &con->flags);

        sock = create_listen_sock(con, &dlm_local_addr);
        if (sock) {
                add_sock(sock, con);
                result = 0;
        }
        else {
                result = -EADDRINUSE;
        }

        return result;
}



static struct writequeue_entry *new_writequeue_entry(struct connection *con,
                                                     gfp_t allocation)
{
        struct writequeue_entry *entry;

        entry = kmalloc(sizeof(struct writequeue_entry), allocation);
        if (!entry)
                return NULL;

        entry->page = alloc_page(allocation);
        if (!entry->page) {
                kfree(entry);
                return NULL;
        }

        entry->offset = 0;
        entry->len = 0;
        entry->end = 0;
        entry->users = 0;
        entry->con = con;

        return entry;
}

void *dlm_lowcomms_get_buffer(int nodeid, int len,
                              gfp_t allocation, char **ppc)
{
        struct connection *con;
        struct writequeue_entry *e;
        int offset = 0;
        int users = 0;

        con = nodeid2con(nodeid, allocation);
        if (!con)
                return NULL;

        e = list_entry(con->writequeue.prev, struct writequeue_entry, list);
        if ((&e->list == &con->writequeue) ||
            (PAGE_CACHE_SIZE - e->end < len)) {
                e = NULL;
        } else {
                offset = e->end;
                e->end += len;
                users = e->users++;
        }
        spin_unlock(&con->writequeue_lock);

        if (e) {
        got_one:
                if (users == 0)
                        kmap(e->page);
                *ppc = page_address(e->page) + offset;
                return e;
        }

        e = new_writequeue_entry(con, allocation);
        if (e) {
                spin_lock(&con->writequeue_lock);
                offset = e->end;
                e->end += len;
                users = e->users++;
                list_add_tail(&e->list, &con->writequeue);
                spin_unlock(&con->writequeue_lock);
                goto got_one;
        }
        return NULL;
}

void dlm_lowcomms_commit_buffer(void *mh)
{
        struct writequeue_entry *e = (struct writequeue_entry *)mh;
        struct connection *con = e->con;
        int users;

        users = --e->users;
        if (users)
                goto out;
        e->len = e->end - e->offset;
        kunmap(e->page);
        spin_unlock(&con->writequeue_lock);

        if (test_and_set_bit(CF_WRITE_PENDING, &con->flags) == 0) {
                spin_lock_bh(&write_sockets_lock);
                list_add_tail(&con->write_list, &write_sockets);
                spin_unlock_bh(&write_sockets_lock);

                wake_up_interruptible(&lowcomms_send_waitq);
        }
        return;

out:
        spin_unlock(&con->writequeue_lock);
        return;
}

static void free_entry(struct writequeue_entry *e)
{
        __free_page(e->page);
        kfree(e);
}

/* Send a message */
static void send_to_sock(struct connection *con)
{
        int ret = 0;
        ssize_t(*sendpage) (struct socket *, struct page *, int, size_t, int);
        const int msg_flags = MSG_DONTWAIT | MSG_NOSIGNAL;
        struct writequeue_entry *e;
        int len, offset;

        down_read(&con->sock_sem);
        if (con->sock == NULL)
                goto out_connect;

        sendpage = con->sock->ops->sendpage;

        spin_lock(&con->writequeue_lock);
        for (;;) {
                e = list_entry(con->writequeue.next, struct writequeue_entry,
                               list);
                if ((struct list_head *) e == &con->writequeue)
                        break;

                len = e->len;
                offset = e->offset;
                BUG_ON(len == 0 && e->users == 0);
                spin_unlock(&con->writequeue_lock);

                ret = 0;
                if (len) {
                        ret = sendpage(con->sock, e->page, offset, len,
                                       msg_flags);
                        if (ret == -EAGAIN || ret == 0)
                                goto out;
                        if (ret <= 0)
                                goto send_error;
                }
                else {
                        /* Don't starve people filling buffers */
                        cond_resched();
                }

                spin_lock(&con->writequeue_lock);
                e->offset += ret;
                e->len -= ret;

                if (e->len == 0 && e->users == 0) {
                        list_del(&e->list);
                        kunmap(e->page);
                        free_entry(e);
                        continue;
                }
        }
        spin_unlock(&con->writequeue_lock);
out:
        up_read(&con->sock_sem);
        return;

send_error:
        up_read(&con->sock_sem);
        close_connection(con, false);
        lowcomms_connect_sock(con);
        return;

out_connect:
        up_read(&con->sock_sem);
        lowcomms_connect_sock(con);
        return;
}

static void clean_one_writequeue(struct connection *con)
{
        struct list_head *list;
        struct list_head *temp;

        spin_lock(&con->writequeue_lock);
        list_for_each_safe(list, temp, &con->writequeue) {
                struct writequeue_entry *e =
                        list_entry(list, struct writequeue_entry, list);
                list_del(&e->list);
                free_entry(e);
        }
        spin_unlock(&con->writequeue_lock);
}

/* Called from recovery when it knows that a node has
   left the cluster */
int dlm_lowcomms_close(int nodeid)
{
        struct connection *con;

        if (!connections)
                goto out;

        log_print("closing connection to node %d", nodeid);
        con = nodeid2con(nodeid, 0);
        if (con) {
                clean_one_writequeue(con);
                close_connection(con, true);
                atomic_set(&con->waiting_requests, 0);
        }
        return 0;

out:
        return -1;
}

/* API send message call, may queue the request */
/* N.B. This is the old interface - use the new one for new calls */
int lowcomms_send_message(int nodeid, char *buf, int len, gfp_t allocation)
{
        struct writequeue_entry *e;
        char *b;

        e = dlm_lowcomms_get_buffer(nodeid, len, allocation, &b);
        if (e) {
                memcpy(b, buf, len);
                dlm_lowcomms_commit_buffer(e);
                return 0;
        }
        return -ENOBUFS;
}

/* Look for activity on active sockets */
static void process_sockets(void)
{
        struct list_head *list;
        struct list_head *temp;
        int count = 0;

        spin_lock_bh(&read_sockets_lock);
        list_for_each_safe(list, temp, &read_sockets) {

                struct connection *con =
                        list_entry(list, struct connection, read_list);
                list_del(&con->read_list);
                clear_bit(CF_READ_PENDING, &con->flags);

                spin_unlock_bh(&read_sockets_lock);

                /* This can reach zero if we are processing requests
                 * as they come in.
                 */
                if (atomic_read(&con->waiting_requests) == 0) {
                        spin_lock_bh(&read_sockets_lock);
                        continue;
                }

                do {
                        con->rx_action(con);

                        /* Don't starve out everyone else */
                        if (++count >= MAX_RX_MSG_COUNT) {
                                cond_resched();
                                count = 0;
                        }

                } while (!atomic_dec_and_test(&con->waiting_requests) &&
                         !kthread_should_stop());

                spin_lock_bh(&read_sockets_lock);
        }
        spin_unlock_bh(&read_sockets_lock);
}

/* Try to send any messages that are pending
 */
static void process_output_queue(void)
{
        struct list_head *list;
        struct list_head *temp;

        spin_lock_bh(&write_sockets_lock);
        list_for_each_safe(list, temp, &write_sockets) {
                struct connection *con =
                        list_entry(list, struct connection, write_list);
                clear_bit(CF_WRITE_PENDING, &con->flags);
                list_del(&con->write_list);

                spin_unlock_bh(&write_sockets_lock);
                send_to_sock(con);
                spin_lock_bh(&write_sockets_lock);
        }
        spin_unlock_bh(&write_sockets_lock);
}

static void process_state_queue(void)
{
        struct list_head *list;
        struct list_head *temp;

        spin_lock_bh(&state_sockets_lock);
        list_for_each_safe(list, temp, &state_sockets) {
                struct connection *con =
                        list_entry(list, struct connection, state_list);
                list_del(&con->state_list);
                clear_bit(CF_CONNECT_PENDING, &con->flags);
                spin_unlock_bh(&state_sockets_lock);

                connect_to_sock(con);
                spin_lock_bh(&state_sockets_lock);
        }
        spin_unlock_bh(&state_sockets_lock);
}


/* Discard all entries on the write queues */
static void clean_writequeues(void)
{
        int nodeid;

        for (nodeid = 1; nodeid < conn_array_size; nodeid++) {
                struct connection *con = nodeid2con(nodeid, 0);

                if (con)
                        clean_one_writequeue(con);
        }
}

static int read_list_empty(void)
{
        int status;

        spin_lock_bh(&read_sockets_lock);
        status = list_empty(&read_sockets);
        spin_unlock_bh(&read_sockets_lock);

        return status;
}

/* DLM Transport comms receive daemon */
static int dlm_recvd(void *data)
{
        init_waitqueue_entry(&lowcomms_recv_waitq_head, current);
        add_wait_queue(&lowcomms_recv_waitq, &lowcomms_recv_waitq_head);

        while (!kthread_should_stop()) {
                set_current_state(TASK_INTERRUPTIBLE);
                if (read_list_empty())
                        cond_resched();
                set_current_state(TASK_RUNNING);

                process_sockets();
        }

        return 0;
}

static int write_and_state_lists_empty(void)
{
        int status;

        spin_lock_bh(&write_sockets_lock);
        status = list_empty(&write_sockets);
        spin_unlock_bh(&write_sockets_lock);

        spin_lock_bh(&state_sockets_lock);
        if (list_empty(&state_sockets) == 0)
                status = 0;
        spin_unlock_bh(&state_sockets_lock);

        return status;
}

/* DLM Transport send daemon */
static int dlm_sendd(void *data)
{
        init_waitqueue_entry(&lowcomms_send_waitq_head, current);
        add_wait_queue(&lowcomms_send_waitq, &lowcomms_send_waitq_head);

        while (!kthread_should_stop()) {
                set_current_state(TASK_INTERRUPTIBLE);
                if (write_and_state_lists_empty())
                        cond_resched();
                set_current_state(TASK_RUNNING);

                process_state_queue();
                process_output_queue();
        }

        return 0;
}

static void daemons_stop(void)
{
        kthread_stop(recv_task);
        kthread_stop(send_task);
}

static int daemons_start(void)
{
        struct task_struct *p;
        int error;

        p = kthread_run(dlm_recvd, NULL, "dlm_recvd");
        error = IS_ERR(p);
        if (error) {
                log_print("can't start dlm_recvd %d", error);
                return error;
        }
        recv_task = p;

        p = kthread_run(dlm_sendd, NULL, "dlm_sendd");
        error = IS_ERR(p);
        if (error) {
                log_print("can't start dlm_sendd %d", error);
                kthread_stop(recv_task);
                return error;
        }
        send_task = p;

        return 0;
}

/*
 * Return the largest buffer size we can cope with.
 */
int lowcomms_max_buffer_size(void)
{
        return PAGE_CACHE_SIZE;
}

void dlm_lowcomms_stop(void)
{
        int i;

        /* Set all the flags to prevent any
           socket activity.
        */
        for (i = 0; i < conn_array_size; i++) {
                if (connections[i])
                        connections[i]->flags |= 0xFF;
        }

        daemons_stop();
        clean_writequeues();

        for (i = 0; i < conn_array_size; i++) {
                if (connections[i]) {
                        close_connection(connections[i], true);
                        if (connections[i]->othercon)
                                kmem_cache_free(con_cache, connections[i]->othercon);
                        kmem_cache_free(con_cache, connections[i]);
                }
        }

        kfree(connections);
        connections = NULL;

        kmem_cache_destroy(con_cache);
}

/* This is quite likely to sleep... */
int dlm_lowcomms_start(void)
{
        int error = 0;

        error = -ENOMEM;
        connections = kzalloc(sizeof(struct connection *) *
                              NODE_INCREMENT, GFP_KERNEL);
        if (!connections)
                goto out;

        conn_array_size = NODE_INCREMENT;

        if (dlm_our_addr(&dlm_local_addr, 0)) {
                log_print("no local IP address has been set");
                goto fail_free_conn;
        }
        if (!dlm_our_addr(&dlm_local_addr, 1)) {
                log_print("This dlm comms module does not support multi-homed clustering");
                goto fail_free_conn;
        }

        con_cache = kmem_cache_create("dlm_conn", sizeof(struct connection),
                                      __alignof__(struct connection), 0,
                                      NULL, NULL);
        if (!con_cache)
                goto fail_free_conn;


        /* Start listening */
        error = listen_for_all();
        if (error)
                goto fail_unlisten;

        error = daemons_start();
        if (error)
                goto fail_unlisten;

        return 0;

fail_unlisten:
        close_connection(connections[0], false);
        kmem_cache_free(con_cache, connections[0]);
        kmem_cache_destroy(con_cache);

fail_free_conn:
        kfree(connections);

out:
        return error;
}

/*
 * Overrides for Emacs so that we follow Linus's tabbing style.
 * Emacs will notice this stuff at the end of the file and automatically
 * adjust the settings for this buffer only.  This must remain at the end
 * of the file.
 * ---------------------------------------------------------------------------
 * Local variables:
 * c-file-style: "linux"
 * End:
 */