writeback: split writeback_inodes_wb

[linux-2.6/next.git] / net / tipc / subscr.c

/*
 * net/tipc/subscr.c: TIPC network topology service
 *
 * Copyright (c) 2000-2006, Ericsson AB
 * Copyright (c) 2005-2007, Wind River Systems
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the names of the copyright holders nor the names of its
 *    contributors may be used to endorse or promote products derived from
 *    this software without specific prior written permission.
 *
 * Alternatively, this software may be distributed under the terms of the
 * GNU General Public License ("GPL") version 2 as published by the Free
 * Software Foundation.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#include "core.h"
#include "dbg.h"
#include "name_table.h"
#include "port.h"
#include "ref.h"
#include "subscr.h"

/**
 * struct subscriber - TIPC network topology subscriber
 * @port_ref: object reference to server port connecting to subscriber
 * @lock: pointer to spinlock controlling access to subscriber's server port
 * @subscriber_list: adjacent subscribers in top. server's list of subscribers
 * @subscription_list: list of subscription objects for this subscriber
 */

struct subscriber {
        u32 port_ref;
        spinlock_t *lock;
        struct list_head subscriber_list;
        struct list_head subscription_list;
};

/**
 * struct top_srv - TIPC network topology subscription service
 * @user_ref: TIPC userid of subscription service
 * @setup_port: reference to TIPC port that handles subscription requests
 * @subscription_count: number of active subscriptions (not subscribers!)
 * @subscriber_list: list of ports subscribing to service
 * @lock: spinlock govering access to subscriber list
 */

struct top_srv {
        u32 user_ref;
        u32 setup_port;
        atomic_t subscription_count;
        struct list_head subscriber_list;
        spinlock_t lock;
};

static struct top_srv topsrv = { 0 };

/**
 * subscr_send_event - send a message containing a tipc_event to the subscriber
 *
 * Note: Must not hold subscriber's server port lock, since tipc_send() will
 *       try to take the lock if the message is rejected and returned!
 */

static void subscr_send_event(struct subscription *sub,
                              u32 found_lower,
                              u32 found_upper,
                              u32 event,
                              u32 port_ref,
                              u32 node)
{
        struct iovec msg_sect;

        msg_sect.iov_base = (void *)&sub->evt;
        msg_sect.iov_len = sizeof(struct tipc_event);

        sub->evt.event = htonl(event);
        sub->evt.found_lower = htonl(found_lower);
        sub->evt.found_upper = htonl(found_upper);
        sub->evt.port.ref = htonl(port_ref);
        sub->evt.port.node = htonl(node);
        tipc_send(sub->server_ref, 1, &msg_sect);
}

/**
 * tipc_subscr_overlap - test for subscription overlap with the given values
 *
 * Returns 1 if there is overlap, otherwise 0.
 */

int tipc_subscr_overlap(struct subscription *sub,
                        u32 found_lower,
                        u32 found_upper)

{
        if (found_lower < sub->seq.lower)
                found_lower = sub->seq.lower;
        if (found_upper > sub->seq.upper)
                found_upper = sub->seq.upper;
        if (found_lower > found_upper)
                return 0;
        return 1;
}

/**
 * tipc_subscr_report_overlap - issue event if there is subscription overlap
 *
 * Protected by nameseq.lock in name_table.c
 */

void tipc_subscr_report_overlap(struct subscription *sub,
                                u32 found_lower,
                                u32 found_upper,
                                u32 event,
                                u32 port_ref,
                                u32 node,
                                int must)
{
        if (!tipc_subscr_overlap(sub, found_lower, found_upper))
                return;
        if (!must && !(sub->filter & TIPC_SUB_PORTS))
                return;

        sub->event_cb(sub, found_lower, found_upper, event, port_ref, node);
}

/**
 * subscr_timeout - subscription timeout has occurred
 */

static void subscr_timeout(struct subscription *sub)
{
        struct port *server_port;

        /* Validate server port reference (in case subscriber is terminating) */

        server_port = tipc_port_lock(sub->server_ref);
        if (server_port == NULL)
                return;

        /* Validate timeout (in case subscription is being cancelled) */

        if (sub->timeout == TIPC_WAIT_FOREVER) {
                tipc_port_unlock(server_port);
                return;
        }

        /* Unlink subscription from name table */

        tipc_nametbl_unsubscribe(sub);

        /* Unlink subscription from subscriber */

        list_del(&sub->subscription_list);

        /* Release subscriber's server port */

        tipc_port_unlock(server_port);

        /* Notify subscriber of timeout */

        subscr_send_event(sub, sub->evt.s.seq.lower, sub->evt.s.seq.upper,
                          TIPC_SUBSCR_TIMEOUT, 0, 0);

        /* Now destroy subscription */

        k_term_timer(&sub->timer);
        kfree(sub);
        atomic_dec(&topsrv.subscription_count);
}

/**
 * subscr_del - delete a subscription within a subscription list
 *
 * Called with subscriber port locked.
 */

static void subscr_del(struct subscription *sub)
{
        tipc_nametbl_unsubscribe(sub);
        list_del(&sub->subscription_list);
        kfree(sub);
        atomic_dec(&topsrv.subscription_count);
}

/**
 * subscr_terminate - terminate communication with a subscriber
 *
 * Called with subscriber port locked.  Routine must temporarily release lock
 * to enable subscription timeout routine(s) to finish without deadlocking;
 * the lock is then reclaimed to allow caller to release it upon return.
 * (This should work even in the unlikely event some other thread creates
 * a new object reference in the interim that uses this lock; this routine will
 * simply wait for it to be released, then claim it.)
 */

static void subscr_terminate(struct subscriber *subscriber)
{
        u32 port_ref;
        struct subscription *sub;
        struct subscription *sub_temp;

        /* Invalidate subscriber reference */

        port_ref = subscriber->port_ref;
        subscriber->port_ref = 0;
        spin_unlock_bh(subscriber->lock);

        /* Sever connection to subscriber */

        tipc_shutdown(port_ref);
        tipc_deleteport(port_ref);

        /* Destroy any existing subscriptions for subscriber */

        list_for_each_entry_safe(sub, sub_temp, &subscriber->subscription_list,
                                 subscription_list) {
                if (sub->timeout != TIPC_WAIT_FOREVER) {
                        k_cancel_timer(&sub->timer);
                        k_term_timer(&sub->timer);
                }
                dbg("Term: Removing sub %u,%u,%u from subscriber %x list\n",
                    sub->seq.type, sub->seq.lower, sub->seq.upper, subscriber);
                subscr_del(sub);
        }

        /* Remove subscriber from topology server's subscriber list */

        spin_lock_bh(&topsrv.lock);
        list_del(&subscriber->subscriber_list);
        spin_unlock_bh(&topsrv.lock);

        /* Reclaim subscriber lock */

        spin_lock_bh(subscriber->lock);

        /* Now destroy subscriber */

        kfree(subscriber);
}

/**
 * subscr_cancel - handle subscription cancellation request
 *
 * Called with subscriber port locked.  Routine must temporarily release lock
 * to enable the subscription timeout routine to finish without deadlocking;
 * the lock is then reclaimed to allow caller to release it upon return.
 *
 * Note that fields of 's' use subscriber's endianness!
 */

static void subscr_cancel(struct tipc_subscr *s,
                          struct subscriber *subscriber)
{
        struct subscription *sub;
        struct subscription *sub_temp;
        __u32 type, lower, upper, timeout, filter;
        int found = 0;

        /* Find first matching subscription, exit if not found */

        type = ntohl(s->seq.type);
        lower = ntohl(s->seq.lower);
        upper = ntohl(s->seq.upper);
        timeout = ntohl(s->timeout);
        filter = ntohl(s->filter) & ~TIPC_SUB_CANCEL;

        list_for_each_entry_safe(sub, sub_temp, &subscriber->subscription_list,
                                 subscription_list) {
                        if ((type == sub->seq.type) &&
                            (lower == sub->seq.lower) &&
                            (upper == sub->seq.upper) &&
                            (timeout == sub->timeout) &&
                            (filter == sub->filter) &&
                             !memcmp(s->usr_handle,sub->evt.s.usr_handle,
                                     sizeof(s->usr_handle)) ){
                                found = 1;
                                break;
                        }
        }
        if (!found)
                return;

        /* Cancel subscription timer (if used), then delete subscription */

        if (sub->timeout != TIPC_WAIT_FOREVER) {
                sub->timeout = TIPC_WAIT_FOREVER;
                spin_unlock_bh(subscriber->lock);
                k_cancel_timer(&sub->timer);
                k_term_timer(&sub->timer);
                spin_lock_bh(subscriber->lock);
        }
        dbg("Cancel: removing sub %u,%u,%u from subscriber %p list\n",
            sub->seq.type, sub->seq.lower, sub->seq.upper, subscriber);
        subscr_del(sub);
}

/**
 * subscr_subscribe - create subscription for subscriber
 *
 * Called with subscriber port locked.
 */

static struct subscription *subscr_subscribe(struct tipc_subscr *s,
                                             struct subscriber *subscriber)
{
        struct subscription *sub;

        /* Detect & process a subscription cancellation request */

        if (ntohl(s->filter) & TIPC_SUB_CANCEL) {
                subscr_cancel(s, subscriber);
                return NULL;
        }

        /* Refuse subscription if global limit exceeded */

        if (atomic_read(&topsrv.subscription_count) >= tipc_max_subscriptions) {
                warn("Subscription rejected, subscription limit reached (%u)\n",
                     tipc_max_subscriptions);
                subscr_terminate(subscriber);
                return NULL;
        }

        /* Allocate subscription object */

        sub = kmalloc(sizeof(*sub), GFP_ATOMIC);
        if (!sub) {
                warn("Subscription rejected, no memory\n");
                subscr_terminate(subscriber);
                return NULL;
        }

        /* Initialize subscription object */

        sub->seq.type = ntohl(s->seq.type);
        sub->seq.lower = ntohl(s->seq.lower);
        sub->seq.upper = ntohl(s->seq.upper);
        sub->timeout = ntohl(s->timeout);
        sub->filter = ntohl(s->filter);
        if ((sub->filter && (sub->filter != TIPC_SUB_PORTS)) ||
            (sub->seq.lower > sub->seq.upper)) {
                warn("Subscription rejected, illegal request\n");
                kfree(sub);
                subscr_terminate(subscriber);
                return NULL;
        }
        sub->event_cb = subscr_send_event;
        INIT_LIST_HEAD(&sub->nameseq_list);
        list_add(&sub->subscription_list, &subscriber->subscription_list);
        sub->server_ref = subscriber->port_ref;
        memcpy(&sub->evt.s, s, sizeof(struct tipc_subscr));
        atomic_inc(&topsrv.subscription_count);
        if (sub->timeout != TIPC_WAIT_FOREVER) {
                k_init_timer(&sub->timer,
                             (Handler)subscr_timeout, (unsigned long)sub);
                k_start_timer(&sub->timer, sub->timeout);
        }

        return sub;
}

/**
 * subscr_conn_shutdown_event - handle termination request from subscriber
 *
 * Called with subscriber's server port unlocked.
 */

static void subscr_conn_shutdown_event(void *usr_handle,
                                       u32 port_ref,
                                       struct sk_buff **buf,
                                       unsigned char const *data,
                                       unsigned int size,
                                       int reason)
{
        struct subscriber *subscriber = usr_handle;
        spinlock_t *subscriber_lock;

        if (tipc_port_lock(port_ref) == NULL)
                return;

        subscriber_lock = subscriber->lock;
        subscr_terminate(subscriber);
        spin_unlock_bh(subscriber_lock);
}

/**
 * subscr_conn_msg_event - handle new subscription request from subscriber
 *
 * Called with subscriber's server port unlocked.
 */

static void subscr_conn_msg_event(void *usr_handle,
                                  u32 port_ref,
                                  struct sk_buff **buf,
                                  const unchar *data,
                                  u32 size)
{
        struct subscriber *subscriber = usr_handle;
        spinlock_t *subscriber_lock;
        struct subscription *sub;

        /*
         * Lock subscriber's server port (& make a local copy of lock pointer,
         * in case subscriber is deleted while processing subscription request)
         */

        if (tipc_port_lock(port_ref) == NULL)
                return;

        subscriber_lock = subscriber->lock;

        if (size != sizeof(struct tipc_subscr)) {
                subscr_terminate(subscriber);
                spin_unlock_bh(subscriber_lock);
        } else {
                sub = subscr_subscribe((struct tipc_subscr *)data, subscriber);
                spin_unlock_bh(subscriber_lock);
                if (sub != NULL) {

                        /*
                         * We must release the server port lock before adding a
                         * subscription to the name table since TIPC needs to be
                         * able to (re)acquire the port lock if an event message
                         * issued by the subscription process is rejected and
                         * returned.  The subscription cannot be deleted while
                         * it is being added to the name table because:
                         * a) the single-threading of the native API port code
                         *    ensures the subscription cannot be cancelled and
                         *    the subscriber connection cannot be broken, and
                         * b) the name table lock ensures the subscription
                         *    timeout code cannot delete the subscription,
                         * so the subscription object is still protected.
                         */

                        tipc_nametbl_subscribe(sub);
                }
        }
}

/**
 * subscr_named_msg_event - handle request to establish a new subscriber
 */

static void subscr_named_msg_event(void *usr_handle,
                                   u32 port_ref,
                                   struct sk_buff **buf,
                                   const unchar *data,
                                   u32 size,
                                   u32 importance,
                                   struct tipc_portid const *orig,
                                   struct tipc_name_seq const *dest)
{
        static struct iovec msg_sect = {NULL, 0};

        struct subscriber *subscriber;
        u32 server_port_ref;

        /* Create subscriber object */

        subscriber = kzalloc(sizeof(struct subscriber), GFP_ATOMIC);
        if (subscriber == NULL) {
                warn("Subscriber rejected, no memory\n");
                return;
        }
        INIT_LIST_HEAD(&subscriber->subscription_list);
        INIT_LIST_HEAD(&subscriber->subscriber_list);

        /* Create server port & establish connection to subscriber */

        tipc_createport(topsrv.user_ref,
                        subscriber,
                        importance,
                        NULL,
                        NULL,
                        subscr_conn_shutdown_event,
                        NULL,
                        NULL,
                        subscr_conn_msg_event,
                        NULL,
                        &subscriber->port_ref);
        if (subscriber->port_ref == 0) {
                warn("Subscriber rejected, unable to create port\n");
                kfree(subscriber);
                return;
        }
        tipc_connect2port(subscriber->port_ref, orig);

        /* Lock server port (& save lock address for future use) */

        subscriber->lock = tipc_port_lock(subscriber->port_ref)->publ.lock;

        /* Add subscriber to topology server's subscriber list */

        spin_lock_bh(&topsrv.lock);
        list_add(&subscriber->subscriber_list, &topsrv.subscriber_list);
        spin_unlock_bh(&topsrv.lock);

        /* Unlock server port */

        server_port_ref = subscriber->port_ref;
        spin_unlock_bh(subscriber->lock);

        /* Send an ACK- to complete connection handshaking */

        tipc_send(server_port_ref, 1, &msg_sect);

        /* Handle optional subscription request */

        if (size != 0) {
                subscr_conn_msg_event(subscriber, server_port_ref,
                                      buf, data, size);
        }
}

int tipc_subscr_start(void)
{
        struct tipc_name_seq seq = {TIPC_TOP_SRV, TIPC_TOP_SRV, TIPC_TOP_SRV};
        int res = -1;

        memset(&topsrv, 0, sizeof (topsrv));
        spin_lock_init(&topsrv.lock);
        INIT_LIST_HEAD(&topsrv.subscriber_list);

        spin_lock_bh(&topsrv.lock);
        res = tipc_attach(&topsrv.user_ref, NULL, NULL);
        if (res) {
                spin_unlock_bh(&topsrv.lock);
                return res;
        }

        res = tipc_createport(topsrv.user_ref,
                              NULL,
                              TIPC_CRITICAL_IMPORTANCE,
                              NULL,
                              NULL,
                              NULL,
                              NULL,
                              subscr_named_msg_event,
                              NULL,
                              NULL,
                              &topsrv.setup_port);
        if (res)
                goto failed;

        res = tipc_nametbl_publish_rsv(topsrv.setup_port, TIPC_NODE_SCOPE, &seq);
        if (res)
                goto failed;

        spin_unlock_bh(&topsrv.lock);
        return 0;

failed:
        err("Failed to create subscription service\n");
        tipc_detach(topsrv.user_ref);
        topsrv.user_ref = 0;
        spin_unlock_bh(&topsrv.lock);
        return res;
}

void tipc_subscr_stop(void)
{
        struct subscriber *subscriber;
        struct subscriber *subscriber_temp;
        spinlock_t *subscriber_lock;

        if (topsrv.user_ref) {
                tipc_deleteport(topsrv.setup_port);
                list_for_each_entry_safe(subscriber, subscriber_temp,
                                         &topsrv.subscriber_list,
                                         subscriber_list) {
                        subscriber_lock = subscriber->lock;
                        spin_lock_bh(subscriber_lock);
                        subscr_terminate(subscriber);
                        spin_unlock_bh(subscriber_lock);
                }
                tipc_detach(topsrv.user_ref);
                topsrv.user_ref = 0;
        }
}


int tipc_ispublished(struct tipc_name const *name)
{
        u32 domain = 0;

        return(tipc_nametbl_translate(name->type, name->instance,&domain) != 0);
}