Linux 2.6.21

[linux/fpc-iii.git] / fs / ocfs2 / dlm / dlmdomain.c

/* -*- mode: c; c-basic-offset: 8; -*-
 * vim: noexpandtab sw=8 ts=8 sts=0:
 *
 * dlmdomain.c
 *
 * defines domain join / leave apis
 *
 * Copyright (C) 2004 Oracle.  All rights reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public
 * License along with this program; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 021110-1307, USA.
 *
 */

#include <linux/module.h>
#include <linux/types.h>
#include <linux/slab.h>
#include <linux/highmem.h>
#include <linux/utsname.h>
#include <linux/init.h>
#include <linux/spinlock.h>
#include <linux/delay.h>
#include <linux/err.h>

#include "cluster/heartbeat.h"
#include "cluster/nodemanager.h"
#include "cluster/tcp.h"

#include "dlmapi.h"
#include "dlmcommon.h"

#include "dlmdomain.h"

#include "dlmver.h"

#define MLOG_MASK_PREFIX (ML_DLM|ML_DLM_DOMAIN)
#include "cluster/masklog.h"

/*
 * ocfs2 node maps are array of long int, which limits to send them freely
 * across the wire due to endianness issues. To workaround this, we convert
 * long ints to byte arrays. Following 3 routines are helper functions to
 * set/test/copy bits within those array of bytes
 */
static inline void byte_set_bit(u8 nr, u8 map[])
{
        map[nr >> 3] |= (1UL << (nr & 7));
}

static inline int byte_test_bit(u8 nr, u8 map[])
{
        return ((1UL << (nr & 7)) & (map[nr >> 3])) != 0;
}

static inline void byte_copymap(u8 dmap[], unsigned long smap[],
                        unsigned int sz)
{
        unsigned int nn;

        if (!sz)
                return;

        memset(dmap, 0, ((sz + 7) >> 3));
        for (nn = 0 ; nn < sz; nn++)
                if (test_bit(nn, smap))
                        byte_set_bit(nn, dmap);
}

static void dlm_free_pagevec(void **vec, int pages)
{
        while (pages--)
                free_page((unsigned long)vec[pages]);
        kfree(vec);
}

static void **dlm_alloc_pagevec(int pages)
{
        void **vec = kmalloc(pages * sizeof(void *), GFP_KERNEL);
        int i;

        if (!vec)
                return NULL;

        for (i = 0; i < pages; i++)
                if (!(vec[i] = (void *)__get_free_page(GFP_KERNEL)))
                        goto out_free;

        mlog(0, "Allocated DLM hash pagevec; %d pages (%lu expected), %lu buckets per page\n",
             pages, (unsigned long)DLM_HASH_PAGES,
             (unsigned long)DLM_BUCKETS_PER_PAGE);
        return vec;
out_free:
        dlm_free_pagevec(vec, i);
        return NULL;
}

/*
 *
 * spinlock lock ordering: if multiple locks are needed, obey this ordering:
 *    dlm_domain_lock
 *    struct dlm_ctxt->spinlock
 *    struct dlm_lock_resource->spinlock
 *    struct dlm_ctxt->master_lock
 *    struct dlm_ctxt->ast_lock
 *    dlm_master_list_entry->spinlock
 *    dlm_lock->spinlock
 *
 */

DEFINE_SPINLOCK(dlm_domain_lock);
LIST_HEAD(dlm_domains);
static DECLARE_WAIT_QUEUE_HEAD(dlm_domain_events);

#define DLM_DOMAIN_BACKOFF_MS 200

static int dlm_query_join_handler(struct o2net_msg *msg, u32 len, void *data,
                                  void **ret_data);
static int dlm_assert_joined_handler(struct o2net_msg *msg, u32 len, void *data,
                                     void **ret_data);
static int dlm_cancel_join_handler(struct o2net_msg *msg, u32 len, void *data,
                                   void **ret_data);
static int dlm_exit_domain_handler(struct o2net_msg *msg, u32 len, void *data,
                                   void **ret_data);

static void dlm_unregister_domain_handlers(struct dlm_ctxt *dlm);

void __dlm_unhash_lockres(struct dlm_lock_resource *lockres)
{
        if (!hlist_unhashed(&lockres->hash_node)) {
                hlist_del_init(&lockres->hash_node);
                dlm_lockres_put(lockres);
        }
}

void __dlm_insert_lockres(struct dlm_ctxt *dlm,
                       struct dlm_lock_resource *res)
{
        struct hlist_head *bucket;
        struct qstr *q;

        assert_spin_locked(&dlm->spinlock);

        q = &res->lockname;
        bucket = dlm_lockres_hash(dlm, q->hash);

        /* get a reference for our hashtable */
        dlm_lockres_get(res);

        hlist_add_head(&res->hash_node, bucket);
}

struct dlm_lock_resource * __dlm_lookup_lockres_full(struct dlm_ctxt *dlm,
                                                     const char *name,
                                                     unsigned int len,
                                                     unsigned int hash)
{
        struct hlist_head *bucket;
        struct hlist_node *list;

        mlog_entry("%.*s\n", len, name);

        assert_spin_locked(&dlm->spinlock);

        bucket = dlm_lockres_hash(dlm, hash);

        hlist_for_each(list, bucket) {
                struct dlm_lock_resource *res = hlist_entry(list,
                        struct dlm_lock_resource, hash_node);
                if (res->lockname.name[0] != name[0])
                        continue;
                if (unlikely(res->lockname.len != len))
                        continue;
                if (memcmp(res->lockname.name + 1, name + 1, len - 1))
                        continue;
                dlm_lockres_get(res);
                return res;
        }
        return NULL;
}

/* intended to be called by functions which do not care about lock
 * resources which are being purged (most net _handler functions).
 * this will return NULL for any lock resource which is found but
 * currently in the process of dropping its mastery reference.
 * use __dlm_lookup_lockres_full when you need the lock resource
 * regardless (e.g. dlm_get_lock_resource) */
struct dlm_lock_resource * __dlm_lookup_lockres(struct dlm_ctxt *dlm,
                                                const char *name,
                                                unsigned int len,
                                                unsigned int hash)
{
        struct dlm_lock_resource *res = NULL;

        mlog_entry("%.*s\n", len, name);

        assert_spin_locked(&dlm->spinlock);

        res = __dlm_lookup_lockres_full(dlm, name, len, hash);
        if (res) {
                spin_lock(&res->spinlock);
                if (res->state & DLM_LOCK_RES_DROPPING_REF) {
                        spin_unlock(&res->spinlock);
                        dlm_lockres_put(res);
                        return NULL;
                }
                spin_unlock(&res->spinlock);
        }

        return res;
}

struct dlm_lock_resource * dlm_lookup_lockres(struct dlm_ctxt *dlm,
                                    const char *name,
                                    unsigned int len)
{
        struct dlm_lock_resource *res;
        unsigned int hash = dlm_lockid_hash(name, len);

        spin_lock(&dlm->spinlock);
        res = __dlm_lookup_lockres(dlm, name, len, hash);
        spin_unlock(&dlm->spinlock);
        return res;
}

static struct dlm_ctxt * __dlm_lookup_domain_full(const char *domain, int len)
{
        struct dlm_ctxt *tmp = NULL;
        struct list_head *iter;

        assert_spin_locked(&dlm_domain_lock);

        /* tmp->name here is always NULL terminated,
         * but domain may not be! */
        list_for_each(iter, &dlm_domains) {
                tmp = list_entry (iter, struct dlm_ctxt, list);
                if (strlen(tmp->name) == len &&
                    memcmp(tmp->name, domain, len)==0)
                        break;
                tmp = NULL;
        }

        return tmp;
}

/* For null terminated domain strings ONLY */
static struct dlm_ctxt * __dlm_lookup_domain(const char *domain)
{
        assert_spin_locked(&dlm_domain_lock);

        return __dlm_lookup_domain_full(domain, strlen(domain));
}


/* returns true on one of two conditions:
 * 1) the domain does not exist
 * 2) the domain exists and it's state is "joined" */
static int dlm_wait_on_domain_helper(const char *domain)
{
        int ret = 0;
        struct dlm_ctxt *tmp = NULL;

        spin_lock(&dlm_domain_lock);

        tmp = __dlm_lookup_domain(domain);
        if (!tmp)
                ret = 1;
        else if (tmp->dlm_state == DLM_CTXT_JOINED)
                ret = 1;

        spin_unlock(&dlm_domain_lock);
        return ret;
}

static void dlm_free_ctxt_mem(struct dlm_ctxt *dlm)
{
        if (dlm->lockres_hash)
                dlm_free_pagevec((void **)dlm->lockres_hash, DLM_HASH_PAGES);

        if (dlm->name)
                kfree(dlm->name);

        kfree(dlm);
}

/* A little strange - this function will be called while holding
 * dlm_domain_lock and is expected to be holding it on the way out. We
 * will however drop and reacquire it multiple times */
static void dlm_ctxt_release(struct kref *kref)
{
        struct dlm_ctxt *dlm;

        dlm = container_of(kref, struct dlm_ctxt, dlm_refs);

        BUG_ON(dlm->num_joins);
        BUG_ON(dlm->dlm_state == DLM_CTXT_JOINED);

        /* we may still be in the list if we hit an error during join. */
        list_del_init(&dlm->list);

        spin_unlock(&dlm_domain_lock);

        mlog(0, "freeing memory from domain %s\n", dlm->name);

        wake_up(&dlm_domain_events);

        dlm_free_ctxt_mem(dlm);

        spin_lock(&dlm_domain_lock);
}

void dlm_put(struct dlm_ctxt *dlm)
{
        spin_lock(&dlm_domain_lock);
        kref_put(&dlm->dlm_refs, dlm_ctxt_release);
        spin_unlock(&dlm_domain_lock);
}

static void __dlm_get(struct dlm_ctxt *dlm)
{
        kref_get(&dlm->dlm_refs);
}

/* given a questionable reference to a dlm object, gets a reference if
 * it can find it in the list, otherwise returns NULL in which case
 * you shouldn't trust your pointer. */
struct dlm_ctxt *dlm_grab(struct dlm_ctxt *dlm)
{
        struct list_head *iter;
        struct dlm_ctxt *target = NULL;

        spin_lock(&dlm_domain_lock);

        list_for_each(iter, &dlm_domains) {
                target = list_entry (iter, struct dlm_ctxt, list);

                if (target == dlm) {
                        __dlm_get(target);
                        break;
                }

                target = NULL;
        }

        spin_unlock(&dlm_domain_lock);

        return target;
}

int dlm_domain_fully_joined(struct dlm_ctxt *dlm)
{
        int ret;

        spin_lock(&dlm_domain_lock);
        ret = (dlm->dlm_state == DLM_CTXT_JOINED) ||
                (dlm->dlm_state == DLM_CTXT_IN_SHUTDOWN);
        spin_unlock(&dlm_domain_lock);

        return ret;
}

static void dlm_destroy_dlm_worker(struct dlm_ctxt *dlm)
{
        if (dlm->dlm_worker) {
                flush_workqueue(dlm->dlm_worker);
                destroy_workqueue(dlm->dlm_worker);
                dlm->dlm_worker = NULL;
        }
}

static void dlm_complete_dlm_shutdown(struct dlm_ctxt *dlm)
{
        dlm_unregister_domain_handlers(dlm);
        dlm_complete_thread(dlm);
        dlm_complete_recovery_thread(dlm);
        dlm_destroy_dlm_worker(dlm);

        /* We've left the domain. Now we can take ourselves out of the
         * list and allow the kref stuff to help us free the
         * memory. */
        spin_lock(&dlm_domain_lock);
        list_del_init(&dlm->list);
        spin_unlock(&dlm_domain_lock);

        /* Wake up anyone waiting for us to remove this domain */
        wake_up(&dlm_domain_events);
}

static int dlm_migrate_all_locks(struct dlm_ctxt *dlm)
{
        int i, num, n, ret = 0;
        struct dlm_lock_resource *res;
        struct hlist_node *iter;
        struct hlist_head *bucket;
        int dropped;

        mlog(0, "Migrating locks from domain %s\n", dlm->name);

        num = 0;
        spin_lock(&dlm->spinlock);
        for (i = 0; i < DLM_HASH_BUCKETS; i++) {
redo_bucket:
                n = 0;
                bucket = dlm_lockres_hash(dlm, i);
                iter = bucket->first;
                while (iter) {
                        n++;
                        res = hlist_entry(iter, struct dlm_lock_resource,
                                          hash_node);
                        dlm_lockres_get(res);
                        /* migrate, if necessary.  this will drop the dlm
                         * spinlock and retake it if it does migration. */
                        dropped = dlm_empty_lockres(dlm, res);

                        spin_lock(&res->spinlock);
                        __dlm_lockres_calc_usage(dlm, res);
                        iter = res->hash_node.next;
                        spin_unlock(&res->spinlock);

                        dlm_lockres_put(res);

                        cond_resched_lock(&dlm->spinlock);

                        if (dropped)
                                goto redo_bucket;
                }
                num += n;
                mlog(0, "%s: touched %d lockreses in bucket %d "
                     "(tot=%d)\n", dlm->name, n, i, num);
        }
        spin_unlock(&dlm->spinlock);
        wake_up(&dlm->dlm_thread_wq);

        /* let the dlm thread take care of purging, keep scanning until
         * nothing remains in the hash */
        if (num) {
                mlog(0, "%s: %d lock resources in hash last pass\n",
                     dlm->name, num);
                ret = -EAGAIN;
        }
        mlog(0, "DONE Migrating locks from domain %s\n", dlm->name);
        return ret;
}

static int dlm_no_joining_node(struct dlm_ctxt *dlm)
{
        int ret;

        spin_lock(&dlm->spinlock);
        ret = dlm->joining_node == DLM_LOCK_RES_OWNER_UNKNOWN;
        spin_unlock(&dlm->spinlock);

        return ret;
}

static void dlm_mark_domain_leaving(struct dlm_ctxt *dlm)
{
        /* Yikes, a double spinlock! I need domain_lock for the dlm
         * state and the dlm spinlock for join state... Sorry! */
again:
        spin_lock(&dlm_domain_lock);
        spin_lock(&dlm->spinlock);

        if (dlm->joining_node != DLM_LOCK_RES_OWNER_UNKNOWN) {
                mlog(0, "Node %d is joining, we wait on it.\n",
                          dlm->joining_node);
                spin_unlock(&dlm->spinlock);
                spin_unlock(&dlm_domain_lock);

                wait_event(dlm->dlm_join_events, dlm_no_joining_node(dlm));
                goto again;
        }

        dlm->dlm_state = DLM_CTXT_LEAVING;
        spin_unlock(&dlm->spinlock);
        spin_unlock(&dlm_domain_lock);
}

static void __dlm_print_nodes(struct dlm_ctxt *dlm)
{
        int node = -1;

        assert_spin_locked(&dlm->spinlock);

        printk(KERN_INFO "ocfs2_dlm: Nodes in domain (\"%s\"): ", dlm->name);

        while ((node = find_next_bit(dlm->domain_map, O2NM_MAX_NODES,
                                     node + 1)) < O2NM_MAX_NODES) {
                printk("%d ", node);
        }
        printk("\n");
}

static int dlm_exit_domain_handler(struct o2net_msg *msg, u32 len, void *data,
                                   void **ret_data)
{
        struct dlm_ctxt *dlm = data;
        unsigned int node;
        struct dlm_exit_domain *exit_msg = (struct dlm_exit_domain *) msg->buf;

        mlog_entry("%p %u %p", msg, len, data);

        if (!dlm_grab(dlm))
                return 0;

        node = exit_msg->node_idx;

        printk(KERN_INFO "ocfs2_dlm: Node %u leaves domain %s\n", node, dlm->name);

        spin_lock(&dlm->spinlock);
        clear_bit(node, dlm->domain_map);
        __dlm_print_nodes(dlm);

        /* notify anything attached to the heartbeat events */
        dlm_hb_event_notify_attached(dlm, node, 0);

        spin_unlock(&dlm->spinlock);

        dlm_put(dlm);

        return 0;
}

static int dlm_send_one_domain_exit(struct dlm_ctxt *dlm,
                                    unsigned int node)
{
        int status;
        struct dlm_exit_domain leave_msg;

        mlog(0, "Asking node %u if we can leave the domain %s me = %u\n",
                  node, dlm->name, dlm->node_num);

        memset(&leave_msg, 0, sizeof(leave_msg));
        leave_msg.node_idx = dlm->node_num;

        status = o2net_send_message(DLM_EXIT_DOMAIN_MSG, dlm->key,
                                    &leave_msg, sizeof(leave_msg), node,
                                    NULL);

        mlog(0, "status return %d from o2net_send_message\n", status);

        return status;
}


static void dlm_leave_domain(struct dlm_ctxt *dlm)
{
        int node, clear_node, status;

        /* At this point we've migrated away all our locks and won't
         * accept mastership of new ones. The dlm is responsible for
         * almost nothing now. We make sure not to confuse any joining
         * nodes and then commence shutdown procedure. */

        spin_lock(&dlm->spinlock);
        /* Clear ourselves from the domain map */
        clear_bit(dlm->node_num, dlm->domain_map);
        while ((node = find_next_bit(dlm->domain_map, O2NM_MAX_NODES,
                                     0)) < O2NM_MAX_NODES) {
                /* Drop the dlm spinlock. This is safe wrt the domain_map.
                 * -nodes cannot be added now as the
                 *   query_join_handlers knows to respond with OK_NO_MAP
                 * -we catch the right network errors if a node is
                 *   removed from the map while we're sending him the
                 *   exit message. */
                spin_unlock(&dlm->spinlock);

                clear_node = 1;

                status = dlm_send_one_domain_exit(dlm, node);
                if (status < 0 &&
                    status != -ENOPROTOOPT &&
                    status != -ENOTCONN) {
                        mlog(ML_NOTICE, "Error %d sending domain exit message "
                             "to node %d\n", status, node);

                        /* Not sure what to do here but lets sleep for
                         * a bit in case this was a transient
                         * error... */
                        msleep(DLM_DOMAIN_BACKOFF_MS);
                        clear_node = 0;
                }

                spin_lock(&dlm->spinlock);
                /* If we're not clearing the node bit then we intend
                 * to loop back around to try again. */
                if (clear_node)
                        clear_bit(node, dlm->domain_map);
        }
        spin_unlock(&dlm->spinlock);
}

int dlm_joined(struct dlm_ctxt *dlm)
{
        int ret = 0;

        spin_lock(&dlm_domain_lock);

        if (dlm->dlm_state == DLM_CTXT_JOINED)
                ret = 1;

        spin_unlock(&dlm_domain_lock);

        return ret;
}

int dlm_shutting_down(struct dlm_ctxt *dlm)
{
        int ret = 0;

        spin_lock(&dlm_domain_lock);

        if (dlm->dlm_state == DLM_CTXT_IN_SHUTDOWN)
                ret = 1;

        spin_unlock(&dlm_domain_lock);

        return ret;
}

void dlm_unregister_domain(struct dlm_ctxt *dlm)
{
        int leave = 0;

        spin_lock(&dlm_domain_lock);
        BUG_ON(dlm->dlm_state != DLM_CTXT_JOINED);
        BUG_ON(!dlm->num_joins);

        dlm->num_joins--;
        if (!dlm->num_joins) {
                /* We mark it "in shutdown" now so new register
                 * requests wait until we've completely left the
                 * domain. Don't use DLM_CTXT_LEAVING yet as we still
                 * want new domain joins to communicate with us at
                 * least until we've completed migration of our
                 * resources. */
                dlm->dlm_state = DLM_CTXT_IN_SHUTDOWN;
                leave = 1;
        }
        spin_unlock(&dlm_domain_lock);

        if (leave) {
                mlog(0, "shutting down domain %s\n", dlm->name);

                /* We changed dlm state, notify the thread */
                dlm_kick_thread(dlm, NULL);

                while (dlm_migrate_all_locks(dlm)) {
                        /* Give dlm_thread time to purge the lockres' */
                        msleep(500);
                        mlog(0, "%s: more migration to do\n", dlm->name);
                }
                dlm_mark_domain_leaving(dlm);
                dlm_leave_domain(dlm);
                dlm_complete_dlm_shutdown(dlm);
        }
        dlm_put(dlm);
}
EXPORT_SYMBOL_GPL(dlm_unregister_domain);

static int dlm_query_join_handler(struct o2net_msg *msg, u32 len, void *data,
                                  void **ret_data)
{
        struct dlm_query_join_request *query;
        enum dlm_query_join_response response;
        struct dlm_ctxt *dlm = NULL;
        u8 nodenum;

        query = (struct dlm_query_join_request *) msg->buf;

        mlog(0, "node %u wants to join domain %s\n", query->node_idx,
                  query->domain);

        /*
         * If heartbeat doesn't consider the node live, tell it
         * to back off and try again.  This gives heartbeat a chance
         * to catch up.
         */
        if (!o2hb_check_node_heartbeating(query->node_idx)) {
                mlog(0, "node %u is not in our live map yet\n",
                     query->node_idx);

                response = JOIN_DISALLOW;
                goto respond;
        }

        response = JOIN_OK_NO_MAP;

        spin_lock(&dlm_domain_lock);
        dlm = __dlm_lookup_domain_full(query->domain, query->name_len);
        if (!dlm)
                goto unlock_respond;

        /*
         * There is a small window where the joining node may not see the
         * node(s) that just left but still part of the cluster. DISALLOW
         * join request if joining node has different node map.
         */
        nodenum=0;
        while (nodenum < O2NM_MAX_NODES) {
                if (test_bit(nodenum, dlm->domain_map)) {
                        if (!byte_test_bit(nodenum, query->node_map)) {
                                mlog(0, "disallow join as node %u does not "
                                     "have node %u in its nodemap\n",
                                     query->node_idx, nodenum);
                                response = JOIN_DISALLOW;
                                goto unlock_respond;
                        }
                }
                nodenum++;
        }

        /* Once the dlm ctxt is marked as leaving then we don't want
         * to be put in someone's domain map. 
         * Also, explicitly disallow joining at certain troublesome
         * times (ie. during recovery). */
        if (dlm && dlm->dlm_state != DLM_CTXT_LEAVING) {
                int bit = query->node_idx;
                spin_lock(&dlm->spinlock);

                if (dlm->dlm_state == DLM_CTXT_NEW &&
                    dlm->joining_node == DLM_LOCK_RES_OWNER_UNKNOWN) {
                        /*If this is a brand new context and we
                         * haven't started our join process yet, then
                         * the other node won the race. */
                        response = JOIN_OK_NO_MAP;
                } else if (dlm->joining_node != DLM_LOCK_RES_OWNER_UNKNOWN) {
                        /* Disallow parallel joins. */
                        response = JOIN_DISALLOW;
                } else if (dlm->reco.state & DLM_RECO_STATE_ACTIVE) {
                        mlog(0, "node %u trying to join, but recovery "
                             "is ongoing.\n", bit);
                        response = JOIN_DISALLOW;
                } else if (test_bit(bit, dlm->recovery_map)) {
                        mlog(0, "node %u trying to join, but it "
                             "still needs recovery.\n", bit);
                        response = JOIN_DISALLOW;
                } else if (test_bit(bit, dlm->domain_map)) {
                        mlog(0, "node %u trying to join, but it "
                             "is still in the domain! needs recovery?\n",
                             bit);
                        response = JOIN_DISALLOW;
                } else {
                        /* Alright we're fully a part of this domain
                         * so we keep some state as to who's joining
                         * and indicate to him that needs to be fixed
                         * up. */
                        response = JOIN_OK;
                        __dlm_set_joining_node(dlm, query->node_idx);
                }

                spin_unlock(&dlm->spinlock);
        }
unlock_respond:
        spin_unlock(&dlm_domain_lock);

respond:
        mlog(0, "We respond with %u\n", response);

        return response;
}

static int dlm_assert_joined_handler(struct o2net_msg *msg, u32 len, void *data,
                                     void **ret_data)
{
        struct dlm_assert_joined *assert;
        struct dlm_ctxt *dlm = NULL;

        assert = (struct dlm_assert_joined *) msg->buf;

        mlog(0, "node %u asserts join on domain %s\n", assert->node_idx,
                  assert->domain);

        spin_lock(&dlm_domain_lock);
        dlm = __dlm_lookup_domain_full(assert->domain, assert->name_len);
        /* XXX should we consider no dlm ctxt an error? */
        if (dlm) {
                spin_lock(&dlm->spinlock);

                /* Alright, this node has officially joined our
                 * domain. Set him in the map and clean up our
                 * leftover join state. */
                BUG_ON(dlm->joining_node != assert->node_idx);
                set_bit(assert->node_idx, dlm->domain_map);
                __dlm_set_joining_node(dlm, DLM_LOCK_RES_OWNER_UNKNOWN);

                printk(KERN_INFO "ocfs2_dlm: Node %u joins domain %s\n",
                       assert->node_idx, dlm->name);
                __dlm_print_nodes(dlm);

                /* notify anything attached to the heartbeat events */
                dlm_hb_event_notify_attached(dlm, assert->node_idx, 1);

                spin_unlock(&dlm->spinlock);
        }
        spin_unlock(&dlm_domain_lock);

        return 0;
}

static int dlm_cancel_join_handler(struct o2net_msg *msg, u32 len, void *data,
                                   void **ret_data)
{
        struct dlm_cancel_join *cancel;
        struct dlm_ctxt *dlm = NULL;

        cancel = (struct dlm_cancel_join *) msg->buf;

        mlog(0, "node %u cancels join on domain %s\n", cancel->node_idx,
                  cancel->domain);

        spin_lock(&dlm_domain_lock);
        dlm = __dlm_lookup_domain_full(cancel->domain, cancel->name_len);

        if (dlm) {
                spin_lock(&dlm->spinlock);

                /* Yikes, this guy wants to cancel his join. No
                 * problem, we simply cleanup our join state. */
                BUG_ON(dlm->joining_node != cancel->node_idx);
                __dlm_set_joining_node(dlm, DLM_LOCK_RES_OWNER_UNKNOWN);

                spin_unlock(&dlm->spinlock);
        }
        spin_unlock(&dlm_domain_lock);

        return 0;
}

static int dlm_send_one_join_cancel(struct dlm_ctxt *dlm,
                                    unsigned int node)
{
        int status;
        struct dlm_cancel_join cancel_msg;

        memset(&cancel_msg, 0, sizeof(cancel_msg));
        cancel_msg.node_idx = dlm->node_num;
        cancel_msg.name_len = strlen(dlm->name);
        memcpy(cancel_msg.domain, dlm->name, cancel_msg.name_len);

        status = o2net_send_message(DLM_CANCEL_JOIN_MSG, DLM_MOD_KEY,
                                    &cancel_msg, sizeof(cancel_msg), node,
                                    NULL);
        if (status < 0) {
                mlog_errno(status);
                goto bail;
        }

bail:
        return status;
}

/* map_size should be in bytes. */
static int dlm_send_join_cancels(struct dlm_ctxt *dlm,
                                 unsigned long *node_map,
                                 unsigned int map_size)
{
        int status, tmpstat;
        unsigned int node;

        if (map_size != (BITS_TO_LONGS(O2NM_MAX_NODES) *
                         sizeof(unsigned long))) {
                mlog(ML_ERROR,
                     "map_size %u != BITS_TO_LONGS(O2NM_MAX_NODES) %u\n",
                     map_size, BITS_TO_LONGS(O2NM_MAX_NODES));
                return -EINVAL;
        }

        status = 0;
        node = -1;
        while ((node = find_next_bit(node_map, O2NM_MAX_NODES,
                                     node + 1)) < O2NM_MAX_NODES) {
                if (node == dlm->node_num)
                        continue;

                tmpstat = dlm_send_one_join_cancel(dlm, node);
                if (tmpstat) {
                        mlog(ML_ERROR, "Error return %d cancelling join on "
                             "node %d\n", tmpstat, node);
                        if (!status)
                                status = tmpstat;
                }
        }

        if (status)
                mlog_errno(status);
        return status;
}

static int dlm_request_join(struct dlm_ctxt *dlm,
                            int node,
                            enum dlm_query_join_response *response)
{
        int status, retval;
        struct dlm_query_join_request join_msg;

        mlog(0, "querying node %d\n", node);

        memset(&join_msg, 0, sizeof(join_msg));
        join_msg.node_idx = dlm->node_num;
        join_msg.name_len = strlen(dlm->name);
        memcpy(join_msg.domain, dlm->name, join_msg.name_len);

        /* copy live node map to join message */
        byte_copymap(join_msg.node_map, dlm->live_nodes_map, O2NM_MAX_NODES);

        status = o2net_send_message(DLM_QUERY_JOIN_MSG, DLM_MOD_KEY, &join_msg,
                                    sizeof(join_msg), node, &retval);
        if (status < 0 && status != -ENOPROTOOPT) {
                mlog_errno(status);
                goto bail;
        }

        /* -ENOPROTOOPT from the net code means the other side isn't
            listening for our message type -- that's fine, it means
            his dlm isn't up, so we can consider him a 'yes' but not
            joined into the domain.  */
        if (status == -ENOPROTOOPT) {
                status = 0;
                *response = JOIN_OK_NO_MAP;
        } else if (retval == JOIN_DISALLOW ||
                   retval == JOIN_OK ||
                   retval == JOIN_OK_NO_MAP) {
                *response = retval;
        } else {
                status = -EINVAL;
                mlog(ML_ERROR, "invalid response %d from node %u\n", retval,
                     node);
        }

        mlog(0, "status %d, node %d response is %d\n", status, node,
                  *response);

bail:
        return status;
}

static int dlm_send_one_join_assert(struct dlm_ctxt *dlm,
                                    unsigned int node)
{
        int status;
        struct dlm_assert_joined assert_msg;

        mlog(0, "Sending join assert to node %u\n", node);

        memset(&assert_msg, 0, sizeof(assert_msg));
        assert_msg.node_idx = dlm->node_num;
        assert_msg.name_len = strlen(dlm->name);
        memcpy(assert_msg.domain, dlm->name, assert_msg.name_len);

        status = o2net_send_message(DLM_ASSERT_JOINED_MSG, DLM_MOD_KEY,
                                    &assert_msg, sizeof(assert_msg), node,
                                    NULL);
        if (status < 0)
                mlog_errno(status);

        return status;
}

static void dlm_send_join_asserts(struct dlm_ctxt *dlm,
                                  unsigned long *node_map)
{
        int status, node, live;

        status = 0;
        node = -1;
        while ((node = find_next_bit(node_map, O2NM_MAX_NODES,
                                     node + 1)) < O2NM_MAX_NODES) {
                if (node == dlm->node_num)
                        continue;

                do {
                        /* It is very important that this message be
                         * received so we spin until either the node
                         * has died or it gets the message. */
                        status = dlm_send_one_join_assert(dlm, node);

                        spin_lock(&dlm->spinlock);
                        live = test_bit(node, dlm->live_nodes_map);
                        spin_unlock(&dlm->spinlock);

                        if (status) {
                                mlog(ML_ERROR, "Error return %d asserting "
                                     "join on node %d\n", status, node);

                                /* give us some time between errors... */
                                if (live)
                                        msleep(DLM_DOMAIN_BACKOFF_MS);
                        }
                } while (status && live);
        }
}

struct domain_join_ctxt {
        unsigned long live_map[BITS_TO_LONGS(O2NM_MAX_NODES)];
        unsigned long yes_resp_map[BITS_TO_LONGS(O2NM_MAX_NODES)];
};

static int dlm_should_restart_join(struct dlm_ctxt *dlm,
                                   struct domain_join_ctxt *ctxt,
                                   enum dlm_query_join_response response)
{
        int ret;

        if (response == JOIN_DISALLOW) {
                mlog(0, "Latest response of disallow -- should restart\n");
                return 1;
        }

        spin_lock(&dlm->spinlock);
        /* For now, we restart the process if the node maps have
         * changed at all */
        ret = memcmp(ctxt->live_map, dlm->live_nodes_map,
                     sizeof(dlm->live_nodes_map));
        spin_unlock(&dlm->spinlock);

        if (ret)
                mlog(0, "Node maps changed -- should restart\n");

        return ret;
}

static int dlm_try_to_join_domain(struct dlm_ctxt *dlm)
{
        int status = 0, tmpstat, node;
        struct domain_join_ctxt *ctxt;
        enum dlm_query_join_response response;

        mlog_entry("%p", dlm);

        ctxt = kzalloc(sizeof(*ctxt), GFP_KERNEL);
        if (!ctxt) {
                status = -ENOMEM;
                mlog_errno(status);
                goto bail;
        }

        /* group sem locking should work for us here -- we're already
         * registered for heartbeat events so filling this should be
         * atomic wrt getting those handlers called. */
        o2hb_fill_node_map(dlm->live_nodes_map, sizeof(dlm->live_nodes_map));

        spin_lock(&dlm->spinlock);
        memcpy(ctxt->live_map, dlm->live_nodes_map, sizeof(ctxt->live_map));

        __dlm_set_joining_node(dlm, dlm->node_num);

        spin_unlock(&dlm->spinlock);

        node = -1;
        while ((node = find_next_bit(ctxt->live_map, O2NM_MAX_NODES,
                                     node + 1)) < O2NM_MAX_NODES) {
                if (node == dlm->node_num)
                        continue;

                status = dlm_request_join(dlm, node, &response);
                if (status < 0) {
                        mlog_errno(status);
                        goto bail;
                }

                /* Ok, either we got a response or the node doesn't have a
                 * dlm up. */
                if (response == JOIN_OK)
                        set_bit(node, ctxt->yes_resp_map);

                if (dlm_should_restart_join(dlm, ctxt, response)) {
                        status = -EAGAIN;
                        goto bail;
                }
        }

        mlog(0, "Yay, done querying nodes!\n");

        /* Yay, everyone agree's we can join the domain. My domain is
         * comprised of all nodes who were put in the
         * yes_resp_map. Copy that into our domain map and send a join
         * assert message to clean up everyone elses state. */
        spin_lock(&dlm->spinlock);
        memcpy(dlm->domain_map, ctxt->yes_resp_map,
               sizeof(ctxt->yes_resp_map));
        set_bit(dlm->node_num, dlm->domain_map);
        spin_unlock(&dlm->spinlock);

        dlm_send_join_asserts(dlm, ctxt->yes_resp_map);

        /* Joined state *must* be set before the joining node
         * information, otherwise the query_join handler may read no
         * current joiner but a state of NEW and tell joining nodes
         * we're not in the domain. */
        spin_lock(&dlm_domain_lock);
        dlm->dlm_state = DLM_CTXT_JOINED;
        dlm->num_joins++;
        spin_unlock(&dlm_domain_lock);

bail:
        spin_lock(&dlm->spinlock);
        __dlm_set_joining_node(dlm, DLM_LOCK_RES_OWNER_UNKNOWN);
        if (!status)
                __dlm_print_nodes(dlm);
        spin_unlock(&dlm->spinlock);

        if (ctxt) {
                /* Do we need to send a cancel message to any nodes? */
                if (status < 0) {
                        tmpstat = dlm_send_join_cancels(dlm,
                                                        ctxt->yes_resp_map,
                                                        sizeof(ctxt->yes_resp_map));
                        if (tmpstat < 0)
                                mlog_errno(tmpstat);
                }
                kfree(ctxt);
        }

        mlog(0, "returning %d\n", status);
        return status;
}

static void dlm_unregister_domain_handlers(struct dlm_ctxt *dlm)
{
        o2hb_unregister_callback(&dlm->dlm_hb_up);
        o2hb_unregister_callback(&dlm->dlm_hb_down);
        o2net_unregister_handler_list(&dlm->dlm_domain_handlers);
}

static int dlm_register_domain_handlers(struct dlm_ctxt *dlm)
{
        int status;

        mlog(0, "registering handlers.\n");

        o2hb_setup_callback(&dlm->dlm_hb_down, O2HB_NODE_DOWN_CB,
                            dlm_hb_node_down_cb, dlm, DLM_HB_NODE_DOWN_PRI);
        status = o2hb_register_callback(&dlm->dlm_hb_down);
        if (status)
                goto bail;

        o2hb_setup_callback(&dlm->dlm_hb_up, O2HB_NODE_UP_CB,
                            dlm_hb_node_up_cb, dlm, DLM_HB_NODE_UP_PRI);
        status = o2hb_register_callback(&dlm->dlm_hb_up);
        if (status)
                goto bail;

        status = o2net_register_handler(DLM_MASTER_REQUEST_MSG, dlm->key,
                                        sizeof(struct dlm_master_request),
                                        dlm_master_request_handler,
                                        dlm, NULL, &dlm->dlm_domain_handlers);
        if (status)
                goto bail;

        status = o2net_register_handler(DLM_ASSERT_MASTER_MSG, dlm->key,
                                        sizeof(struct dlm_assert_master),
                                        dlm_assert_master_handler,
                                        dlm, dlm_assert_master_post_handler,
                                        &dlm->dlm_domain_handlers);
        if (status)
                goto bail;

        status = o2net_register_handler(DLM_CREATE_LOCK_MSG, dlm->key,
                                        sizeof(struct dlm_create_lock),
                                        dlm_create_lock_handler,
                                        dlm, NULL, &dlm->dlm_domain_handlers);
        if (status)
                goto bail;

        status = o2net_register_handler(DLM_CONVERT_LOCK_MSG, dlm->key,
                                        DLM_CONVERT_LOCK_MAX_LEN,
                                        dlm_convert_lock_handler,
                                        dlm, NULL, &dlm->dlm_domain_handlers);
        if (status)
                goto bail;

        status = o2net_register_handler(DLM_UNLOCK_LOCK_MSG, dlm->key,
                                        DLM_UNLOCK_LOCK_MAX_LEN,
                                        dlm_unlock_lock_handler,
                                        dlm, NULL, &dlm->dlm_domain_handlers);
        if (status)
                goto bail;

        status = o2net_register_handler(DLM_PROXY_AST_MSG, dlm->key,
                                        DLM_PROXY_AST_MAX_LEN,
                                        dlm_proxy_ast_handler,
                                        dlm, NULL, &dlm->dlm_domain_handlers);
        if (status)
                goto bail;

        status = o2net_register_handler(DLM_EXIT_DOMAIN_MSG, dlm->key,
                                        sizeof(struct dlm_exit_domain),
                                        dlm_exit_domain_handler,
                                        dlm, NULL, &dlm->dlm_domain_handlers);
        if (status)
                goto bail;

        status = o2net_register_handler(DLM_DEREF_LOCKRES_MSG, dlm->key,
                                        sizeof(struct dlm_deref_lockres),
                                        dlm_deref_lockres_handler,
                                        dlm, NULL, &dlm->dlm_domain_handlers);
        if (status)
                goto bail;

        status = o2net_register_handler(DLM_MIGRATE_REQUEST_MSG, dlm->key,
                                        sizeof(struct dlm_migrate_request),
                                        dlm_migrate_request_handler,
                                        dlm, NULL, &dlm->dlm_domain_handlers);
        if (status)
                goto bail;

        status = o2net_register_handler(DLM_MIG_LOCKRES_MSG, dlm->key,
                                        DLM_MIG_LOCKRES_MAX_LEN,
                                        dlm_mig_lockres_handler,
                                        dlm, NULL, &dlm->dlm_domain_handlers);
        if (status)
                goto bail;

        status = o2net_register_handler(DLM_MASTER_REQUERY_MSG, dlm->key,
                                        sizeof(struct dlm_master_requery),
                                        dlm_master_requery_handler,
                                        dlm, NULL, &dlm->dlm_domain_handlers);
        if (status)
                goto bail;

        status = o2net_register_handler(DLM_LOCK_REQUEST_MSG, dlm->key,
                                        sizeof(struct dlm_lock_request),
                                        dlm_request_all_locks_handler,
                                        dlm, NULL, &dlm->dlm_domain_handlers);
        if (status)
                goto bail;

        status = o2net_register_handler(DLM_RECO_DATA_DONE_MSG, dlm->key,
                                        sizeof(struct dlm_reco_data_done),
                                        dlm_reco_data_done_handler,
                                        dlm, NULL, &dlm->dlm_domain_handlers);
        if (status)
                goto bail;

        status = o2net_register_handler(DLM_BEGIN_RECO_MSG, dlm->key,
                                        sizeof(struct dlm_begin_reco),
                                        dlm_begin_reco_handler,
                                        dlm, NULL, &dlm->dlm_domain_handlers);
        if (status)
                goto bail;

        status = o2net_register_handler(DLM_FINALIZE_RECO_MSG, dlm->key,
                                        sizeof(struct dlm_finalize_reco),
                                        dlm_finalize_reco_handler,
                                        dlm, NULL, &dlm->dlm_domain_handlers);
        if (status)
                goto bail;

bail:
        if (status)
                dlm_unregister_domain_handlers(dlm);

        return status;
}

static int dlm_join_domain(struct dlm_ctxt *dlm)
{
        int status;
        unsigned int backoff;
        unsigned int total_backoff = 0;

        BUG_ON(!dlm);

        mlog(0, "Join domain %s\n", dlm->name);

        status = dlm_register_domain_handlers(dlm);
        if (status) {
                mlog_errno(status);
                goto bail;
        }

        status = dlm_launch_thread(dlm);
        if (status < 0) {
                mlog_errno(status);
                goto bail;
        }

        status = dlm_launch_recovery_thread(dlm);
        if (status < 0) {
                mlog_errno(status);
                goto bail;
        }

        dlm->dlm_worker = create_singlethread_workqueue("dlm_wq");
        if (!dlm->dlm_worker) {
                status = -ENOMEM;
                mlog_errno(status);
                goto bail;
        }

        do {
                status = dlm_try_to_join_domain(dlm);

                /* If we're racing another node to the join, then we
                 * need to back off temporarily and let them
                 * complete. */
#define DLM_JOIN_TIMEOUT_MSECS  90000
                if (status == -EAGAIN) {
                        if (signal_pending(current)) {
                                status = -ERESTARTSYS;
                                goto bail;
                        }

                        if (total_backoff >
                            msecs_to_jiffies(DLM_JOIN_TIMEOUT_MSECS)) {
                                status = -ERESTARTSYS;
                                mlog(ML_NOTICE, "Timed out joining dlm domain "
                                     "%s after %u msecs\n", dlm->name,
                                     jiffies_to_msecs(total_backoff));
                                goto bail;
                        }

                        /*
                         * <chip> After you!
                         * <dale> No, after you!
                         * <chip> I insist!
                         * <dale> But you first!
                         * ...
                         */
                        backoff = (unsigned int)(jiffies & 0x3);
                        backoff *= DLM_DOMAIN_BACKOFF_MS;
                        total_backoff += backoff;
                        mlog(0, "backoff %d\n", backoff);
                        msleep(backoff);
                }
        } while (status == -EAGAIN);

        if (status < 0) {
                mlog_errno(status);
                goto bail;
        }

        status = 0;
bail:
        wake_up(&dlm_domain_events);

        if (status) {
                dlm_unregister_domain_handlers(dlm);
                dlm_complete_thread(dlm);
                dlm_complete_recovery_thread(dlm);
                dlm_destroy_dlm_worker(dlm);
        }

        return status;
}

static struct dlm_ctxt *dlm_alloc_ctxt(const char *domain,
                                u32 key)
{
        int i;
        struct dlm_ctxt *dlm = NULL;

        dlm = kzalloc(sizeof(*dlm), GFP_KERNEL);
        if (!dlm) {
                mlog_errno(-ENOMEM);
                goto leave;
        }

        dlm->name = kmalloc(strlen(domain) + 1, GFP_KERNEL);
        if (dlm->name == NULL) {
                mlog_errno(-ENOMEM);
                kfree(dlm);
                dlm = NULL;
                goto leave;
        }

        dlm->lockres_hash = (struct hlist_head **)dlm_alloc_pagevec(DLM_HASH_PAGES);
        if (!dlm->lockres_hash) {
                mlog_errno(-ENOMEM);
                kfree(dlm->name);
                kfree(dlm);
                dlm = NULL;
                goto leave;
        }

        for (i = 0; i < DLM_HASH_BUCKETS; i++)
                INIT_HLIST_HEAD(dlm_lockres_hash(dlm, i));

        strcpy(dlm->name, domain);
        dlm->key = key;
        dlm->node_num = o2nm_this_node();

        spin_lock_init(&dlm->spinlock);
        spin_lock_init(&dlm->master_lock);
        spin_lock_init(&dlm->ast_lock);
        INIT_LIST_HEAD(&dlm->list);
        INIT_LIST_HEAD(&dlm->dirty_list);
        INIT_LIST_HEAD(&dlm->reco.resources);
        INIT_LIST_HEAD(&dlm->reco.received);
        INIT_LIST_HEAD(&dlm->reco.node_data);
        INIT_LIST_HEAD(&dlm->purge_list);
        INIT_LIST_HEAD(&dlm->dlm_domain_handlers);
        dlm->reco.state = 0;

        INIT_LIST_HEAD(&dlm->pending_asts);
        INIT_LIST_HEAD(&dlm->pending_basts);

        mlog(0, "dlm->recovery_map=%p, &(dlm->recovery_map[0])=%p\n",
                  dlm->recovery_map, &(dlm->recovery_map[0]));

        memset(dlm->recovery_map, 0, sizeof(dlm->recovery_map));
        memset(dlm->live_nodes_map, 0, sizeof(dlm->live_nodes_map));
        memset(dlm->domain_map, 0, sizeof(dlm->domain_map));

        dlm->dlm_thread_task = NULL;
        dlm->dlm_reco_thread_task = NULL;
        dlm->dlm_worker = NULL;
        init_waitqueue_head(&dlm->dlm_thread_wq);
        init_waitqueue_head(&dlm->dlm_reco_thread_wq);
        init_waitqueue_head(&dlm->reco.event);
        init_waitqueue_head(&dlm->ast_wq);
        init_waitqueue_head(&dlm->migration_wq);
        INIT_LIST_HEAD(&dlm->master_list);
        INIT_LIST_HEAD(&dlm->mle_hb_events);

        dlm->joining_node = DLM_LOCK_RES_OWNER_UNKNOWN;
        init_waitqueue_head(&dlm->dlm_join_events);

        dlm->reco.new_master = O2NM_INVALID_NODE_NUM;
        dlm->reco.dead_node = O2NM_INVALID_NODE_NUM;
        atomic_set(&dlm->local_resources, 0);
        atomic_set(&dlm->remote_resources, 0);
        atomic_set(&dlm->unknown_resources, 0);

        spin_lock_init(&dlm->work_lock);
        INIT_LIST_HEAD(&dlm->work_list);
        INIT_WORK(&dlm->dispatched_work, dlm_dispatch_work);

        kref_init(&dlm->dlm_refs);
        dlm->dlm_state = DLM_CTXT_NEW;

        INIT_LIST_HEAD(&dlm->dlm_eviction_callbacks);

        mlog(0, "context init: refcount %u\n",
                  atomic_read(&dlm->dlm_refs.refcount));

leave:
        return dlm;
}

/*
 * dlm_register_domain: one-time setup per "domain"
 */
struct dlm_ctxt * dlm_register_domain(const char *domain,
                               u32 key)
{
        int ret;
        struct dlm_ctxt *dlm = NULL;
        struct dlm_ctxt *new_ctxt = NULL;

        if (strlen(domain) > O2NM_MAX_NAME_LEN) {
                ret = -ENAMETOOLONG;
                mlog(ML_ERROR, "domain name length too long\n");
                goto leave;
        }

        if (!o2hb_check_local_node_heartbeating()) {
                mlog(ML_ERROR, "the local node has not been configured, or is "
                     "not heartbeating\n");
                ret = -EPROTO;
                goto leave;
        }

        mlog(0, "register called for domain \"%s\"\n", domain);

retry:
        dlm = NULL;
        if (signal_pending(current)) {
                ret = -ERESTARTSYS;
                mlog_errno(ret);
                goto leave;
        }

        spin_lock(&dlm_domain_lock);

        dlm = __dlm_lookup_domain(domain);
        if (dlm) {
                if (dlm->dlm_state != DLM_CTXT_JOINED) {
                        spin_unlock(&dlm_domain_lock);

                        mlog(0, "This ctxt is not joined yet!\n");
                        wait_event_interruptible(dlm_domain_events,
                                                 dlm_wait_on_domain_helper(
                                                         domain));
                        goto retry;
                }

                __dlm_get(dlm);
                dlm->num_joins++;

                spin_unlock(&dlm_domain_lock);

                ret = 0;
                goto leave;
        }

        /* doesn't exist */
        if (!new_ctxt) {
                spin_unlock(&dlm_domain_lock);

                new_ctxt = dlm_alloc_ctxt(domain, key);
                if (new_ctxt)
                        goto retry;

                ret = -ENOMEM;
                mlog_errno(ret);
                goto leave;
        }

        /* a little variable switch-a-roo here... */
        dlm = new_ctxt;
        new_ctxt = NULL;

        /* add the new domain */
        list_add_tail(&dlm->list, &dlm_domains);
        spin_unlock(&dlm_domain_lock);

        ret = dlm_join_domain(dlm);
        if (ret) {
                mlog_errno(ret);
                dlm_put(dlm);
                goto leave;
        }

        ret = 0;
leave:
        if (new_ctxt)
                dlm_free_ctxt_mem(new_ctxt);

        if (ret < 0)
                dlm = ERR_PTR(ret);

        return dlm;
}
EXPORT_SYMBOL_GPL(dlm_register_domain);

static LIST_HEAD(dlm_join_handlers);

static void dlm_unregister_net_handlers(void)
{
        o2net_unregister_handler_list(&dlm_join_handlers);
}

static int dlm_register_net_handlers(void)
{
        int status = 0;

        status = o2net_register_handler(DLM_QUERY_JOIN_MSG, DLM_MOD_KEY,
                                        sizeof(struct dlm_query_join_request),
                                        dlm_query_join_handler,
                                        NULL, NULL, &dlm_join_handlers);
        if (status)
                goto bail;

        status = o2net_register_handler(DLM_ASSERT_JOINED_MSG, DLM_MOD_KEY,
                                        sizeof(struct dlm_assert_joined),
                                        dlm_assert_joined_handler,
                                        NULL, NULL, &dlm_join_handlers);
        if (status)
                goto bail;

        status = o2net_register_handler(DLM_CANCEL_JOIN_MSG, DLM_MOD_KEY,
                                        sizeof(struct dlm_cancel_join),
                                        dlm_cancel_join_handler,
                                        NULL, NULL, &dlm_join_handlers);

bail:
        if (status < 0)
                dlm_unregister_net_handlers();

        return status;
}

/* Domain eviction callback handling.
 *
 * The file system requires notification of node death *before* the
 * dlm completes it's recovery work, otherwise it may be able to
 * acquire locks on resources requiring recovery. Since the dlm can
 * evict a node from it's domain *before* heartbeat fires, a similar
 * mechanism is required. */

/* Eviction is not expected to happen often, so a per-domain lock is
 * not necessary. Eviction callbacks are allowed to sleep for short
 * periods of time. */
static DECLARE_RWSEM(dlm_callback_sem);

void dlm_fire_domain_eviction_callbacks(struct dlm_ctxt *dlm,
                                        int node_num)
{
        struct list_head *iter;
        struct dlm_eviction_cb *cb;

        down_read(&dlm_callback_sem);
        list_for_each(iter, &dlm->dlm_eviction_callbacks) {
                cb = list_entry(iter, struct dlm_eviction_cb, ec_item);

                cb->ec_func(node_num, cb->ec_data);
        }
        up_read(&dlm_callback_sem);
}

void dlm_setup_eviction_cb(struct dlm_eviction_cb *cb,
                           dlm_eviction_func *f,
                           void *data)
{
        INIT_LIST_HEAD(&cb->ec_item);
        cb->ec_func = f;
        cb->ec_data = data;
}
EXPORT_SYMBOL_GPL(dlm_setup_eviction_cb);

void dlm_register_eviction_cb(struct dlm_ctxt *dlm,
                              struct dlm_eviction_cb *cb)
{
        down_write(&dlm_callback_sem);
        list_add_tail(&cb->ec_item, &dlm->dlm_eviction_callbacks);
        up_write(&dlm_callback_sem);
}
EXPORT_SYMBOL_GPL(dlm_register_eviction_cb);

void dlm_unregister_eviction_cb(struct dlm_eviction_cb *cb)
{
        down_write(&dlm_callback_sem);
        list_del_init(&cb->ec_item);
        up_write(&dlm_callback_sem);
}
EXPORT_SYMBOL_GPL(dlm_unregister_eviction_cb);

static int __init dlm_init(void)
{
        int status;

        dlm_print_version();

        status = dlm_init_mle_cache();
        if (status)
                return -1;

        status = dlm_register_net_handlers();
        if (status) {
                dlm_destroy_mle_cache();
                return -1;
        }

        return 0;
}

static void __exit dlm_exit (void)
{
        dlm_unregister_net_handlers();
        dlm_destroy_mle_cache();
}

MODULE_AUTHOR("Oracle");
MODULE_LICENSE("GPL");

module_init(dlm_init);
module_exit(dlm_exit);