[deliverable/linux.git] / fs / ocfs2 / dlm / dlmrecovery.c

/* -*- mode: c; c-basic-offset: 8; -*-
 * vim: noexpandtab sw=8 ts=8 sts=0:
 *
 * dlmrecovery.c
 *
 * recovery stuff
 *
 * 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/fs.h>
#include <linux/types.h>
#include <linux/slab.h>
#include <linux/highmem.h>
#include <linux/utsname.h>
#include <linux/init.h>
#include <linux/sysctl.h>
#include <linux/random.h>
#include <linux/blkdev.h>
#include <linux/socket.h>
#include <linux/inet.h>
#include <linux/timer.h>
#include <linux/kthread.h>
#include <linux/delay.h>


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

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

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

static void dlm_do_local_recovery_cleanup(struct dlm_ctxt *dlm, u8 dead_node);

static int dlm_recovery_thread(void *data);
void dlm_complete_recovery_thread(struct dlm_ctxt *dlm);
int dlm_launch_recovery_thread(struct dlm_ctxt *dlm);
static void dlm_kick_recovery_thread(struct dlm_ctxt *dlm);
static int dlm_do_recovery(struct dlm_ctxt *dlm);

static int dlm_pick_recovery_master(struct dlm_ctxt *dlm);
static int dlm_remaster_locks(struct dlm_ctxt *dlm, u8 dead_node);
static int dlm_init_recovery_area(struct dlm_ctxt *dlm, u8 dead_node);
static int dlm_request_all_locks(struct dlm_ctxt *dlm,
                                 u8 request_from, u8 dead_node);
static void dlm_destroy_recovery_area(struct dlm_ctxt *dlm, u8 dead_node);

static inline int dlm_num_locks_in_lockres(struct dlm_lock_resource *res);
static void dlm_init_migratable_lockres(struct dlm_migratable_lockres *mres,
                                        const char *lockname, int namelen,
                                        int total_locks, u64 cookie,
                                        u8 flags, u8 master);
static int dlm_send_mig_lockres_msg(struct dlm_ctxt *dlm,
                                    struct dlm_migratable_lockres *mres,
                                    u8 send_to,
                                    struct dlm_lock_resource *res,
                                    int total_locks);
static int dlm_lockres_master_requery(struct dlm_ctxt *dlm,
                                      struct dlm_lock_resource *res,
                                      u8 *real_master);
static int dlm_process_recovery_data(struct dlm_ctxt *dlm,
                                     struct dlm_lock_resource *res,
                                     struct dlm_migratable_lockres *mres);
static int dlm_do_master_requery(struct dlm_ctxt *dlm,
                                 struct dlm_lock_resource *res,
                                 u8 nodenum, u8 *real_master);
static int dlm_send_finalize_reco_message(struct dlm_ctxt *dlm);
static int dlm_send_all_done_msg(struct dlm_ctxt *dlm,
                                 u8 dead_node, u8 send_to);
static int dlm_send_begin_reco_message(struct dlm_ctxt *dlm, u8 dead_node);
static void dlm_move_reco_locks_to_list(struct dlm_ctxt *dlm,
                                        struct list_head *list, u8 dead_node);
static void dlm_finish_local_lockres_recovery(struct dlm_ctxt *dlm,
                                              u8 dead_node, u8 new_master);
static void dlm_reco_ast(void *astdata);
static void dlm_reco_bast(void *astdata, int blocked_type);
static void dlm_reco_unlock_ast(void *astdata, enum dlm_status st);
static void dlm_request_all_locks_worker(struct dlm_work_item *item,
                                         void *data);
static void dlm_mig_lockres_worker(struct dlm_work_item *item, void *data);

static u64 dlm_get_next_mig_cookie(void);

static spinlock_t dlm_reco_state_lock = SPIN_LOCK_UNLOCKED;
static spinlock_t dlm_mig_cookie_lock = SPIN_LOCK_UNLOCKED;
static u64 dlm_mig_cookie = 1;

static u64 dlm_get_next_mig_cookie(void)
{
        u64 c;
        spin_lock(&dlm_mig_cookie_lock);
        c = dlm_mig_cookie;
        if (dlm_mig_cookie == (~0ULL))
                dlm_mig_cookie = 1;
        else
                dlm_mig_cookie++;
        spin_unlock(&dlm_mig_cookie_lock);
        return c;
}

static inline void dlm_reset_recovery(struct dlm_ctxt *dlm)
{
        spin_lock(&dlm->spinlock);
        clear_bit(dlm->reco.dead_node, dlm->recovery_map);
        dlm->reco.dead_node = O2NM_INVALID_NODE_NUM;
        dlm->reco.new_master = O2NM_INVALID_NODE_NUM;
        spin_unlock(&dlm->spinlock);
}

/* Worker function used during recovery. */
void dlm_dispatch_work(void *data)
{
        struct dlm_ctxt *dlm = (struct dlm_ctxt *)data;
        LIST_HEAD(tmp_list);
        struct list_head *iter, *iter2;
        struct dlm_work_item *item;
        dlm_workfunc_t *workfunc;

        spin_lock(&dlm->work_lock);
        list_splice_init(&dlm->work_list, &tmp_list);
        spin_unlock(&dlm->work_lock);

        list_for_each_safe(iter, iter2, &tmp_list) {
                item = list_entry(iter, struct dlm_work_item, list);
                workfunc = item->func;
                list_del_init(&item->list);

                /* already have ref on dlm to avoid having
                 * it disappear.  just double-check. */
                BUG_ON(item->dlm != dlm);

                /* this is allowed to sleep and
                 * call network stuff */
                workfunc(item, item->data);

                dlm_put(dlm);
                kfree(item);
        }
}

/*
 * RECOVERY THREAD
 */

static void dlm_kick_recovery_thread(struct dlm_ctxt *dlm)
{
        /* wake the recovery thread
         * this will wake the reco thread in one of three places
         * 1) sleeping with no recovery happening
         * 2) sleeping with recovery mastered elsewhere
         * 3) recovery mastered here, waiting on reco data */

        wake_up(&dlm->dlm_reco_thread_wq);
}

/* Launch the recovery thread */
int dlm_launch_recovery_thread(struct dlm_ctxt *dlm)
{
        mlog(0, "starting dlm recovery thread...\n");

        dlm->dlm_reco_thread_task = kthread_run(dlm_recovery_thread, dlm,
                                                "dlm_reco_thread");
        if (IS_ERR(dlm->dlm_reco_thread_task)) {
                mlog_errno(PTR_ERR(dlm->dlm_reco_thread_task));
                dlm->dlm_reco_thread_task = NULL;
                return -EINVAL;
        }

        return 0;
}

void dlm_complete_recovery_thread(struct dlm_ctxt *dlm)
{
        if (dlm->dlm_reco_thread_task) {
                mlog(0, "waiting for dlm recovery thread to exit\n");
                kthread_stop(dlm->dlm_reco_thread_task);
                dlm->dlm_reco_thread_task = NULL;
        }
}



/*
 * this is lame, but here's how recovery works...
 * 1) all recovery threads cluster wide will work on recovering
 *    ONE node at a time
 * 2) negotiate who will take over all the locks for the dead node.
 *    thats right... ALL the locks.
 * 3) once a new master is chosen, everyone scans all locks
 *    and moves aside those mastered by the dead guy
 * 4) each of these locks should be locked until recovery is done
 * 5) the new master collects up all of secondary lock queue info
 *    one lock at a time, forcing each node to communicate back
 *    before continuing
 * 6) each secondary lock queue responds with the full known lock info
 * 7) once the new master has run all its locks, it sends a ALLDONE!
 *    message to everyone
 * 8) upon receiving this message, the secondary queue node unlocks
 *    and responds to the ALLDONE
 * 9) once the new master gets responses from everyone, he unlocks
 *    everything and recovery for this dead node is done
 *10) go back to 2) while there are still dead nodes
 *
 */


#define DLM_RECO_THREAD_TIMEOUT_MS (5 * 1000)

static int dlm_recovery_thread(void *data)
{
        int status;
        struct dlm_ctxt *dlm = data;
        unsigned long timeout = msecs_to_jiffies(DLM_RECO_THREAD_TIMEOUT_MS);

        mlog(0, "dlm thread running for %s...\n", dlm->name);

        while (!kthread_should_stop()) {
                if (dlm_joined(dlm)) {
                        status = dlm_do_recovery(dlm);
                        if (status == -EAGAIN) {
                                /* do not sleep, recheck immediately. */
                                continue;
                        }
                        if (status < 0)
                                mlog_errno(status);
                }

                wait_event_interruptible_timeout(dlm->dlm_reco_thread_wq,
                                                 kthread_should_stop(),
                                                 timeout);
        }

        mlog(0, "quitting DLM recovery thread\n");
        return 0;
}

/* returns true when the recovery master has contacted us */
static int dlm_reco_master_ready(struct dlm_ctxt *dlm)
{
        int ready;
        spin_lock(&dlm->spinlock);
        ready = (dlm->reco.new_master != O2NM_INVALID_NODE_NUM);
        spin_unlock(&dlm->spinlock);
        return ready;
}

/* returns true if node is no longer in the domain
 * could be dead or just not joined */
int dlm_is_node_dead(struct dlm_ctxt *dlm, u8 node)
{
        int dead;
        spin_lock(&dlm->spinlock);
        dead = test_bit(node, dlm->domain_map);
        spin_unlock(&dlm->spinlock);
        return dead;
}

/* callers of the top-level api calls (dlmlock/dlmunlock) should
 * block on the dlm->reco.event when recovery is in progress.
 * the dlm recovery thread will set this state when it begins
 * recovering a dead node (as the new master or not) and clear
 * the state and wake as soon as all affected lock resources have
 * been marked with the RECOVERY flag */
static int dlm_in_recovery(struct dlm_ctxt *dlm)
{
        int in_recovery;
        spin_lock(&dlm->spinlock);
        in_recovery = !!(dlm->reco.state & DLM_RECO_STATE_ACTIVE);
        spin_unlock(&dlm->spinlock);
        return in_recovery;
}


void dlm_wait_for_recovery(struct dlm_ctxt *dlm)
{
        wait_event(dlm->reco.event, !dlm_in_recovery(dlm));
}

static void dlm_begin_recovery(struct dlm_ctxt *dlm)
{
        spin_lock(&dlm->spinlock);
        BUG_ON(dlm->reco.state & DLM_RECO_STATE_ACTIVE);
        dlm->reco.state |= DLM_RECO_STATE_ACTIVE;
        spin_unlock(&dlm->spinlock);
}

static void dlm_end_recovery(struct dlm_ctxt *dlm)
{
        spin_lock(&dlm->spinlock);
        BUG_ON(!(dlm->reco.state & DLM_RECO_STATE_ACTIVE));
        dlm->reco.state &= ~DLM_RECO_STATE_ACTIVE;
        spin_unlock(&dlm->spinlock);
        wake_up(&dlm->reco.event);
}

static int dlm_do_recovery(struct dlm_ctxt *dlm)
{
        int status = 0;
        int ret;

        spin_lock(&dlm->spinlock);

        /* check to see if the new master has died */
        if (dlm->reco.new_master != O2NM_INVALID_NODE_NUM &&
            test_bit(dlm->reco.new_master, dlm->recovery_map)) {
                mlog(0, "new master %u died while recovering %u!\n",
                     dlm->reco.new_master, dlm->reco.dead_node);
                /* unset the new_master, leave dead_node */
                dlm->reco.new_master = O2NM_INVALID_NODE_NUM;
        }

        /* select a target to recover */
        if (dlm->reco.dead_node == O2NM_INVALID_NODE_NUM) {
                int bit;

                bit = find_next_bit (dlm->recovery_map, O2NM_MAX_NODES+1, 0);
                if (bit >= O2NM_MAX_NODES || bit < 0)
                        dlm->reco.dead_node = O2NM_INVALID_NODE_NUM;
                else
                        dlm->reco.dead_node = bit;
        } else if (!test_bit(dlm->reco.dead_node, dlm->recovery_map)) {
                /* BUG? */
                mlog(ML_ERROR, "dead_node %u no longer in recovery map!\n",
                     dlm->reco.dead_node);
                dlm->reco.dead_node = O2NM_INVALID_NODE_NUM;
        }

        if (dlm->reco.dead_node == O2NM_INVALID_NODE_NUM) {
                // mlog(0, "nothing to recover!  sleeping now!\n");
                spin_unlock(&dlm->spinlock);
                /* return to main thread loop and sleep. */
                return 0;
        }
        mlog(0, "recovery thread found node %u in the recovery map!\n",
             dlm->reco.dead_node);
        spin_unlock(&dlm->spinlock);

        /* take write barrier */
        /* (stops the list reshuffling thread, proxy ast handling) */
        dlm_begin_recovery(dlm);

        if (dlm->reco.new_master == dlm->node_num)
                goto master_here;

        if (dlm->reco.new_master == O2NM_INVALID_NODE_NUM) {
                /* choose a new master, returns 0 if this node
                 * is the master, -EEXIST if it's another node.
                 * this does not return until a new master is chosen
                 * or recovery completes entirely. */
                ret = dlm_pick_recovery_master(dlm);
                if (!ret) {
                        /* already notified everyone.  go. */
                        goto master_here;
                }
                mlog(0, "another node will master this recovery session.\n");
        }
        mlog(0, "dlm=%s, new_master=%u, this node=%u, dead_node=%u\n",
             dlm->name, dlm->reco.new_master,
             dlm->node_num, dlm->reco.dead_node);

        /* it is safe to start everything back up here
         * because all of the dead node's lock resources
         * have been marked as in-recovery */
        dlm_end_recovery(dlm);

        /* sleep out in main dlm_recovery_thread loop. */
        return 0;

master_here:
        mlog(0, "mastering recovery of %s:%u here(this=%u)!\n",
             dlm->name, dlm->reco.dead_node, dlm->node_num);

        status = dlm_remaster_locks(dlm, dlm->reco.dead_node);
        if (status < 0) {
                mlog(ML_ERROR, "error %d remastering locks for node %u, "
                     "retrying.\n", status, dlm->reco.dead_node);
                /* yield a bit to allow any final network messages
                 * to get handled on remaining nodes */
                msleep(100);
        } else {
                /* success!  see if any other nodes need recovery */
                mlog(0, "DONE mastering recovery of %s:%u here(this=%u)!\n",
                     dlm->name, dlm->reco.dead_node, dlm->node_num);
                dlm_reset_recovery(dlm);
        }
        dlm_end_recovery(dlm);

        /* continue and look for another dead node */
        return -EAGAIN;
}

static int dlm_remaster_locks(struct dlm_ctxt *dlm, u8 dead_node)
{
        int status = 0;
        struct dlm_reco_node_data *ndata;
        struct list_head *iter;
        int all_nodes_done;
        int destroy = 0;
        int pass = 0;

        status = dlm_init_recovery_area(dlm, dead_node);
        if (status < 0)
                goto leave;

        /* safe to access the node data list without a lock, since this
         * process is the only one to change the list */
        list_for_each(iter, &dlm->reco.node_data) {
                ndata = list_entry (iter, struct dlm_reco_node_data, list);
                BUG_ON(ndata->state != DLM_RECO_NODE_DATA_INIT);
                ndata->state = DLM_RECO_NODE_DATA_REQUESTING;

                mlog(0, "requesting lock info from node %u\n",
                     ndata->node_num);

                if (ndata->node_num == dlm->node_num) {
                        ndata->state = DLM_RECO_NODE_DATA_DONE;
                        continue;
                }

                status = dlm_request_all_locks(dlm, ndata->node_num, dead_node);
                if (status < 0) {
                        mlog_errno(status);
                        if (dlm_is_host_down(status))
                                ndata->state = DLM_RECO_NODE_DATA_DEAD;
                        else {
                                destroy = 1;
                                goto leave;
                        }
                }

                switch (ndata->state) {
                        case DLM_RECO_NODE_DATA_INIT:
                        case DLM_RECO_NODE_DATA_FINALIZE_SENT:
                        case DLM_RECO_NODE_DATA_REQUESTED:
                                BUG();
                                break;
                        case DLM_RECO_NODE_DATA_DEAD:
                                mlog(0, "node %u died after requesting "
                                     "recovery info for node %u\n",
                                     ndata->node_num, dead_node);
                                // start all over
                                destroy = 1;
                                status = -EAGAIN;
                                goto leave;
                        case DLM_RECO_NODE_DATA_REQUESTING:
                                ndata->state = DLM_RECO_NODE_DATA_REQUESTED;
                                mlog(0, "now receiving recovery data from "
                                     "node %u for dead node %u\n",
                                     ndata->node_num, dead_node);
                                break;
                        case DLM_RECO_NODE_DATA_RECEIVING:
                                mlog(0, "already receiving recovery data from "
                                     "node %u for dead node %u\n",
                                     ndata->node_num, dead_node);
                                break;
                        case DLM_RECO_NODE_DATA_DONE:
                                mlog(0, "already DONE receiving recovery data "
                                     "from node %u for dead node %u\n",
                                     ndata->node_num, dead_node);
                                break;
                }
        }

        mlog(0, "done requesting all lock info\n");

        /* nodes should be sending reco data now
         * just need to wait */

        while (1) {
                /* check all the nodes now to see if we are
                 * done, or if anyone died */
                all_nodes_done = 1;
                spin_lock(&dlm_reco_state_lock);
                list_for_each(iter, &dlm->reco.node_data) {
                        ndata = list_entry (iter, struct dlm_reco_node_data, list);

                        mlog(0, "checking recovery state of node %u\n",
                             ndata->node_num);
                        switch (ndata->state) {
                                case DLM_RECO_NODE_DATA_INIT:
                                case DLM_RECO_NODE_DATA_REQUESTING:
                                        mlog(ML_ERROR, "bad ndata state for "
                                             "node %u: state=%d\n",
                                             ndata->node_num, ndata->state);
                                        BUG();
                                        break;
                                case DLM_RECO_NODE_DATA_DEAD:
                                        mlog(ML_NOTICE, "node %u died after "
                                             "requesting recovery info for "
                                             "node %u\n", ndata->node_num,
                                             dead_node);
                                        spin_unlock(&dlm_reco_state_lock);
                                        // start all over
                                        destroy = 1;
                                        status = -EAGAIN;
                                        /* instead of spinning like crazy here,
                                         * wait for the domain map to catch up
                                         * with the network state.  otherwise this
                                         * can be hit hundreds of times before
                                         * the node is really seen as dead. */
                                        wait_event_timeout(dlm->dlm_reco_thread_wq,
                                                           dlm_is_node_dead(dlm,
                                                                ndata->node_num),
                                                           msecs_to_jiffies(1000));
                                        mlog(0, "waited 1 sec for %u, "
                                             "dead? %s\n", ndata->node_num,
                                             dlm_is_node_dead(dlm, ndata->node_num) ?
                                             "yes" : "no");
                                        goto leave;
                                case DLM_RECO_NODE_DATA_RECEIVING:
                                case DLM_RECO_NODE_DATA_REQUESTED:
                                        all_nodes_done = 0;
                                        break;
                                case DLM_RECO_NODE_DATA_DONE:
                                        break;
                                case DLM_RECO_NODE_DATA_FINALIZE_SENT:
                                        break;
                        }
                }
                spin_unlock(&dlm_reco_state_lock);

                mlog(0, "pass #%d, all_nodes_done?: %s\n", ++pass,
                     all_nodes_done?"yes":"no");
                if (all_nodes_done) {
                        int ret;

                        /* all nodes are now in DLM_RECO_NODE_DATA_DONE state
                         * just send a finalize message to everyone and
                         * clean up */
                        mlog(0, "all nodes are done! send finalize\n");
                        ret = dlm_send_finalize_reco_message(dlm);
                        if (ret < 0)
                                mlog_errno(ret);

                        spin_lock(&dlm->spinlock);
                        dlm_finish_local_lockres_recovery(dlm, dead_node,
                                                          dlm->node_num);
                        spin_unlock(&dlm->spinlock);
                        mlog(0, "should be done with recovery!\n");

                        mlog(0, "finishing recovery of %s at %lu, "
                             "dead=%u, this=%u, new=%u\n", dlm->name,
                             jiffies, dlm->reco.dead_node,
                             dlm->node_num, dlm->reco.new_master);
                        destroy = 1;
                        status = ret;
                        /* rescan everything marked dirty along the way */
                        dlm_kick_thread(dlm, NULL);
                        break;
                }
                /* wait to be signalled, with periodic timeout
                 * to check for node death */
                wait_event_interruptible_timeout(dlm->dlm_reco_thread_wq,
                                         kthread_should_stop(),
                                         msecs_to_jiffies(DLM_RECO_THREAD_TIMEOUT_MS));

        }

leave:
        if (destroy)
                dlm_destroy_recovery_area(dlm, dead_node);

        mlog_exit(status);
        return status;
}

static int dlm_init_recovery_area(struct dlm_ctxt *dlm, u8 dead_node)
{
        int num=0;
        struct dlm_reco_node_data *ndata;

        spin_lock(&dlm->spinlock);
        memcpy(dlm->reco.node_map, dlm->domain_map, sizeof(dlm->domain_map));
        /* nodes can only be removed (by dying) after dropping
         * this lock, and death will be trapped later, so this should do */
        spin_unlock(&dlm->spinlock);

        while (1) {
                num = find_next_bit (dlm->reco.node_map, O2NM_MAX_NODES, num);
                if (num >= O2NM_MAX_NODES) {
                        break;
                }
                BUG_ON(num == dead_node);

                ndata = kcalloc(1, sizeof(*ndata), GFP_KERNEL);
                if (!ndata) {
                        dlm_destroy_recovery_area(dlm, dead_node);
                        return -ENOMEM;
                }
                ndata->node_num = num;
                ndata->state = DLM_RECO_NODE_DATA_INIT;
                spin_lock(&dlm_reco_state_lock);
                list_add_tail(&ndata->list, &dlm->reco.node_data);
                spin_unlock(&dlm_reco_state_lock);
                num++;
        }

        return 0;
}

static void dlm_destroy_recovery_area(struct dlm_ctxt *dlm, u8 dead_node)
{
        struct list_head *iter, *iter2;
        struct dlm_reco_node_data *ndata;
        LIST_HEAD(tmplist);

        spin_lock(&dlm_reco_state_lock);
        list_splice_init(&dlm->reco.node_data, &tmplist);
        spin_unlock(&dlm_reco_state_lock);

        list_for_each_safe(iter, iter2, &tmplist) {
                ndata = list_entry (iter, struct dlm_reco_node_data, list);
                list_del_init(&ndata->list);
                kfree(ndata);
        }
}

static int dlm_request_all_locks(struct dlm_ctxt *dlm, u8 request_from,
                                 u8 dead_node)
{
        struct dlm_lock_request lr;
        enum dlm_status ret;

        mlog(0, "\n");


        mlog(0, "dlm_request_all_locks: dead node is %u, sending request "
                  "to %u\n", dead_node, request_from);

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

        // send message
        ret = DLM_NOLOCKMGR;
        ret = o2net_send_message(DLM_LOCK_REQUEST_MSG, dlm->key,
                                 &lr, sizeof(lr), request_from, NULL);

        /* negative status is handled by caller */
        if (ret < 0)
                mlog_errno(ret);

        // return from here, then
        // sleep until all received or error
        return ret;

}

int dlm_request_all_locks_handler(struct o2net_msg *msg, u32 len, void *data)
{
        struct dlm_ctxt *dlm = data;
        struct dlm_lock_request *lr = (struct dlm_lock_request *)msg->buf;
        char *buf = NULL;
        struct dlm_work_item *item = NULL;

        if (!dlm_grab(dlm))
                return -EINVAL;

        BUG_ON(lr->dead_node != dlm->reco.dead_node);

        item = kcalloc(1, sizeof(*item), GFP_KERNEL);
        if (!item) {
                dlm_put(dlm);
                return -ENOMEM;
        }

        /* this will get freed by dlm_request_all_locks_worker */
        buf = (char *) __get_free_page(GFP_KERNEL);
        if (!buf) {
                kfree(item);
                dlm_put(dlm);
                return -ENOMEM;
        }

        /* queue up work for dlm_request_all_locks_worker */
        dlm_grab(dlm);  /* get an extra ref for the work item */
        dlm_init_work_item(dlm, item, dlm_request_all_locks_worker, buf);
        item->u.ral.reco_master = lr->node_idx;
        item->u.ral.dead_node = lr->dead_node;
        spin_lock(&dlm->work_lock);
        list_add_tail(&item->list, &dlm->work_list);
        spin_unlock(&dlm->work_lock);
        schedule_work(&dlm->dispatched_work);

        dlm_put(dlm);
        return 0;
}

static void dlm_request_all_locks_worker(struct dlm_work_item *item, void *data)
{
        struct dlm_migratable_lockres *mres;
        struct dlm_lock_resource *res;
        struct dlm_ctxt *dlm;
        LIST_HEAD(resources);
        struct list_head *iter;
        int ret;
        u8 dead_node, reco_master;

        dlm = item->dlm;
        dead_node = item->u.ral.dead_node;
        reco_master = item->u.ral.reco_master;
        mres = (struct dlm_migratable_lockres *)data;

        if (dead_node != dlm->reco.dead_node ||
            reco_master != dlm->reco.new_master) {
                /* show extra debug info if the recovery state is messed */
                mlog(ML_ERROR, "%s: bad reco state: reco(dead=%u, master=%u), "
                     "request(dead=%u, master=%u)\n",
                     dlm->name, dlm->reco.dead_node, dlm->reco.new_master,
                     dead_node, reco_master);
                mlog(ML_ERROR, "%s: name=%.*s master=%u locks=%u/%u flags=%u "
                     "entry[0]={c=%"MLFu64",l=%u,f=%u,t=%d,ct=%d,hb=%d,n=%u}\n",
                     dlm->name, mres->lockname_len, mres->lockname, mres->master,
                     mres->num_locks, mres->total_locks, mres->flags,
                     mres->ml[0].cookie, mres->ml[0].list, mres->ml[0].flags,
                     mres->ml[0].type, mres->ml[0].convert_type,
                     mres->ml[0].highest_blocked, mres->ml[0].node);
                BUG();
        }
        BUG_ON(dead_node != dlm->reco.dead_node);
        BUG_ON(reco_master != dlm->reco.new_master);

        /* lock resources should have already been moved to the
         * dlm->reco.resources list.  now move items from that list
         * to a temp list if the dead owner matches.  note that the
         * whole cluster recovers only one node at a time, so we
         * can safely move UNKNOWN lock resources for each recovery
         * session. */
        dlm_move_reco_locks_to_list(dlm, &resources, dead_node);

        /* now we can begin blasting lockreses without the dlm lock */
        list_for_each(iter, &resources) {
                res = list_entry (iter, struct dlm_lock_resource, recovering);
                ret = dlm_send_one_lockres(dlm, res, mres, reco_master,
                                        DLM_MRES_RECOVERY);
                if (ret < 0)
                        mlog_errno(ret);
        }

        /* move the resources back to the list */
        spin_lock(&dlm->spinlock);
        list_splice_init(&resources, &dlm->reco.resources);
        spin_unlock(&dlm->spinlock);

        ret = dlm_send_all_done_msg(dlm, dead_node, reco_master);
        if (ret < 0)
                mlog_errno(ret);

        free_page((unsigned long)data);
}


static int dlm_send_all_done_msg(struct dlm_ctxt *dlm, u8 dead_node, u8 send_to)
{
        int ret, tmpret;
        struct dlm_reco_data_done done_msg;

        memset(&done_msg, 0, sizeof(done_msg));
        done_msg.node_idx = dlm->node_num;
        done_msg.dead_node = dead_node;
        mlog(0, "sending DATA DONE message to %u, "
             "my node=%u, dead node=%u\n", send_to, done_msg.node_idx,
             done_msg.dead_node);

        ret = o2net_send_message(DLM_RECO_DATA_DONE_MSG, dlm->key, &done_msg,
                                 sizeof(done_msg), send_to, &tmpret);
        /* negative status is ignored by the caller */
        if (ret >= 0)
                ret = tmpret;
        return ret;
}


int dlm_reco_data_done_handler(struct o2net_msg *msg, u32 len, void *data)
{
        struct dlm_ctxt *dlm = data;
        struct dlm_reco_data_done *done = (struct dlm_reco_data_done *)msg->buf;
        struct list_head *iter;
        struct dlm_reco_node_data *ndata = NULL;
        int ret = -EINVAL;

        if (!dlm_grab(dlm))
                return -EINVAL;

        mlog(0, "got DATA DONE: dead_node=%u, reco.dead_node=%u, "
             "node_idx=%u, this node=%u\n", done->dead_node,
             dlm->reco.dead_node, done->node_idx, dlm->node_num);
        BUG_ON(done->dead_node != dlm->reco.dead_node);

        spin_lock(&dlm_reco_state_lock);
        list_for_each(iter, &dlm->reco.node_data) {
                ndata = list_entry (iter, struct dlm_reco_node_data, list);
                if (ndata->node_num != done->node_idx)
                        continue;

                switch (ndata->state) {
                        /* should have moved beyond INIT but not to FINALIZE yet */
                        case DLM_RECO_NODE_DATA_INIT:
                        case DLM_RECO_NODE_DATA_DEAD:
                        case DLM_RECO_NODE_DATA_FINALIZE_SENT:
                                mlog(ML_ERROR, "bad ndata state for node %u:"
                                     " state=%d\n", ndata->node_num,
                                     ndata->state);
                                BUG();
                                break;
                        /* these states are possible at this point, anywhere along
                         * the line of recovery */
                        case DLM_RECO_NODE_DATA_DONE:
                        case DLM_RECO_NODE_DATA_RECEIVING:
                        case DLM_RECO_NODE_DATA_REQUESTED:
                        case DLM_RECO_NODE_DATA_REQUESTING:
                                mlog(0, "node %u is DONE sending "
                                          "recovery data!\n",
                                          ndata->node_num);

                                ndata->state = DLM_RECO_NODE_DATA_DONE;
                                ret = 0;
                                break;
                }
        }
        spin_unlock(&dlm_reco_state_lock);

        /* wake the recovery thread, some node is done */
        if (!ret)
                dlm_kick_recovery_thread(dlm);

        if (ret < 0)
                mlog(ML_ERROR, "failed to find recovery node data for node "
                     "%u\n", done->node_idx);
        dlm_put(dlm);

        mlog(0, "leaving reco data done handler, ret=%d\n", ret);
        return ret;
}

static void dlm_move_reco_locks_to_list(struct dlm_ctxt *dlm,
                                        struct list_head *list,
                                        u8 dead_node)
{
        struct dlm_lock_resource *res;
        struct list_head *iter, *iter2;
        struct dlm_lock *lock;

        spin_lock(&dlm->spinlock);
        list_for_each_safe(iter, iter2, &dlm->reco.resources) {
                res = list_entry (iter, struct dlm_lock_resource, recovering);
                /* always prune any $RECOVERY entries for dead nodes,
                 * otherwise hangs can occur during later recovery */
                if (dlm_is_recovery_lock(res->lockname.name,
                                         res->lockname.len)) {
                        spin_lock(&res->spinlock);
                        list_for_each_entry(lock, &res->granted, list) {
                                if (lock->ml.node == dead_node) {
                                        mlog(0, "AHA! there was "
                                             "a $RECOVERY lock for dead "
                                             "node %u (%s)!\n", 
                                             dead_node, dlm->name);
                                        list_del_init(&lock->list);
                                        dlm_lock_put(lock);
                                        break;
                                }
                        }
                        spin_unlock(&res->spinlock);
                        continue;
                }

                if (res->owner == dead_node) {
                        mlog(0, "found lockres owned by dead node while "
                                  "doing recovery for node %u. sending it.\n",
                                  dead_node);
                        list_del_init(&res->recovering);
                        list_add_tail(&res->recovering, list);
                } else if (res->owner == DLM_LOCK_RES_OWNER_UNKNOWN) {
                        mlog(0, "found UNKNOWN owner while doing recovery "
                                  "for node %u. sending it.\n", dead_node);
                        list_del_init(&res->recovering);
                        list_add_tail(&res->recovering, list);
                }
        }
        spin_unlock(&dlm->spinlock);
}

static inline int dlm_num_locks_in_lockres(struct dlm_lock_resource *res)
{
        int total_locks = 0;
        struct list_head *iter, *queue = &res->granted;
        int i;

        for (i=0; i<3; i++) {
                list_for_each(iter, queue)
                        total_locks++;
                queue++;
        }
        return total_locks;
}


static int dlm_send_mig_lockres_msg(struct dlm_ctxt *dlm,
                                      struct dlm_migratable_lockres *mres,
                                      u8 send_to,
                                      struct dlm_lock_resource *res,
                                      int total_locks)
{
        u64 mig_cookie = be64_to_cpu(mres->mig_cookie);
        int mres_total_locks = be32_to_cpu(mres->total_locks);
        int sz, ret = 0, status = 0;
        u8 orig_flags = mres->flags,
           orig_master = mres->master;

        BUG_ON(mres->num_locks > DLM_MAX_MIGRATABLE_LOCKS);
        if (!mres->num_locks)
                return 0;

        sz = sizeof(struct dlm_migratable_lockres) +
                (mres->num_locks * sizeof(struct dlm_migratable_lock));

        /* add an all-done flag if we reached the last lock */
        orig_flags = mres->flags;
        BUG_ON(total_locks > mres_total_locks);
        if (total_locks == mres_total_locks)
                mres->flags |= DLM_MRES_ALL_DONE;

        /* send it */
        ret = o2net_send_message(DLM_MIG_LOCKRES_MSG, dlm->key, mres,
                                 sz, send_to, &status);
        if (ret < 0) {
                /* XXX: negative status is not handled.
                 * this will end up killing this node. */
                mlog_errno(ret);
        } else {
                /* might get an -ENOMEM back here */
                ret = status;
                if (ret < 0) {
                        mlog_errno(ret);

                        if (ret == -EFAULT) {
                                mlog(ML_ERROR, "node %u told me to kill "
                                     "myself!\n", send_to);
                                BUG();
                        }
                }
        }

        /* zero and reinit the message buffer */
        dlm_init_migratable_lockres(mres, res->lockname.name,
                                    res->lockname.len, mres_total_locks,
                                    mig_cookie, orig_flags, orig_master);
        return ret;
}

static void dlm_init_migratable_lockres(struct dlm_migratable_lockres *mres,
                                        const char *lockname, int namelen,
                                        int total_locks, u64 cookie,
                                        u8 flags, u8 master)
{
        /* mres here is one full page */
        memset(mres, 0, PAGE_SIZE);
        mres->lockname_len = namelen;
        memcpy(mres->lockname, lockname, namelen);
        mres->num_locks = 0;
        mres->total_locks = cpu_to_be32(total_locks);
        mres->mig_cookie = cpu_to_be64(cookie);
        mres->flags = flags;
        mres->master = master;
}


/* returns 1 if this lock fills the network structure,
 * 0 otherwise */
static int dlm_add_lock_to_array(struct dlm_lock *lock,
                                 struct dlm_migratable_lockres *mres, int queue)
{
        struct dlm_migratable_lock *ml;
        int lock_num = mres->num_locks;

        ml = &(mres->ml[lock_num]);
        ml->cookie = lock->ml.cookie;
        ml->type = lock->ml.type;
        ml->convert_type = lock->ml.convert_type;
        ml->highest_blocked = lock->ml.highest_blocked;
        ml->list = queue;
        if (lock->lksb) {
                ml->flags = lock->lksb->flags;
                /* send our current lvb */
                if (ml->type == LKM_EXMODE ||
                    ml->type == LKM_PRMODE) {
                        /* if it is already set, this had better be a PR
                         * and it has to match */
                        if (mres->lvb[0] && (ml->type == LKM_EXMODE ||
                            memcmp(mres->lvb, lock->lksb->lvb, DLM_LVB_LEN))) {
                                mlog(ML_ERROR, "mismatched lvbs!\n");
                                __dlm_print_one_lock_resource(lock->lockres);
                                BUG();
                        }
                        memcpy(mres->lvb, lock->lksb->lvb, DLM_LVB_LEN);
                }
        }
        ml->node = lock->ml.node;
        mres->num_locks++;
        /* we reached the max, send this network message */
        if (mres->num_locks == DLM_MAX_MIGRATABLE_LOCKS)
                return 1;
        return 0;
}


int dlm_send_one_lockres(struct dlm_ctxt *dlm, struct dlm_lock_resource *res,
                         struct dlm_migratable_lockres *mres,
                         u8 send_to, u8 flags)
{
        struct list_head *queue, *iter;
        int total_locks, i;
        u64 mig_cookie = 0;
        struct dlm_lock *lock;
        int ret = 0;

        BUG_ON(!(flags & (DLM_MRES_RECOVERY|DLM_MRES_MIGRATION)));

        mlog(0, "sending to %u\n", send_to);

        total_locks = dlm_num_locks_in_lockres(res);
        if (total_locks > DLM_MAX_MIGRATABLE_LOCKS) {
                /* rare, but possible */
                mlog(0, "argh.  lockres has %d locks.  this will "
                          "require more than one network packet to "
                          "migrate\n", total_locks);
                mig_cookie = dlm_get_next_mig_cookie();
        }

        dlm_init_migratable_lockres(mres, res->lockname.name,
                                    res->lockname.len, total_locks,
                                    mig_cookie, flags, res->owner);

        total_locks = 0;
        for (i=DLM_GRANTED_LIST; i<=DLM_BLOCKED_LIST; i++) {
                queue = dlm_list_idx_to_ptr(res, i);
                list_for_each(iter, queue) {
                        lock = list_entry (iter, struct dlm_lock, list);

                        /* add another lock. */
                        total_locks++;
                        if (!dlm_add_lock_to_array(lock, mres, i))
                                continue;

                        /* this filled the lock message,
                         * we must send it immediately. */
                        ret = dlm_send_mig_lockres_msg(dlm, mres, send_to,
                                                       res, total_locks);
                        if (ret < 0) {
                                // TODO
                                mlog(ML_ERROR, "dlm_send_mig_lockres_msg "
                                     "returned %d, TODO\n", ret);
                                BUG();
                        }
                }
        }
        /* flush any remaining locks */
        ret = dlm_send_mig_lockres_msg(dlm, mres, send_to, res, total_locks);
        if (ret < 0) {
                // TODO
                mlog(ML_ERROR, "dlm_send_mig_lockres_msg returned %d, "
                     "TODO\n", ret);
                BUG();
        }
        return ret;
}



/*
 * this message will contain no more than one page worth of
 * recovery data, and it will work on only one lockres.
 * there may be many locks in this page, and we may need to wait
 * for additional packets to complete all the locks (rare, but
 * possible).
 */
/*
 * NOTE: the allocation error cases here are scary
 * we really cannot afford to fail an alloc in recovery
 * do we spin?  returning an error only delays the problem really
 */

int dlm_mig_lockres_handler(struct o2net_msg *msg, u32 len, void *data)
{
        struct dlm_ctxt *dlm = data;
        struct dlm_migratable_lockres *mres =
                (struct dlm_migratable_lockres *)msg->buf;
        int ret = 0;
        u8 real_master;
        char *buf = NULL;
        struct dlm_work_item *item = NULL;
        struct dlm_lock_resource *res = NULL;

        if (!dlm_grab(dlm))
                return -EINVAL;

        BUG_ON(!(mres->flags & (DLM_MRES_RECOVERY|DLM_MRES_MIGRATION)));

        real_master = mres->master;
        if (real_master == DLM_LOCK_RES_OWNER_UNKNOWN) {
                /* cannot migrate a lockres with no master */
                BUG_ON(!(mres->flags & DLM_MRES_RECOVERY));
        }

        mlog(0, "%s message received from node %u\n",
                  (mres->flags & DLM_MRES_RECOVERY) ?
                  "recovery" : "migration", mres->master);
        if (mres->flags & DLM_MRES_ALL_DONE)
                mlog(0, "all done flag.  all lockres data received!\n");

        ret = -ENOMEM;
        buf = kmalloc(be16_to_cpu(msg->data_len), GFP_KERNEL);
        item = kcalloc(1, sizeof(*item), GFP_KERNEL);
        if (!buf || !item)
                goto leave;

        /* lookup the lock to see if we have a secondary queue for this
         * already...  just add the locks in and this will have its owner
         * and RECOVERY flag changed when it completes. */
        res = dlm_lookup_lockres(dlm, mres->lockname, mres->lockname_len);
        if (res) {
                /* this will get a ref on res */
                /* mark it as recovering/migrating and hash it */
                spin_lock(&res->spinlock);
                if (mres->flags & DLM_MRES_RECOVERY) {
                        res->state |= DLM_LOCK_RES_RECOVERING;
                } else {
                        if (res->state & DLM_LOCK_RES_MIGRATING) {
                                /* this is at least the second
                                 * lockres message */
                                mlog(0, "lock %.*s is already migrating\n",
                                          mres->lockname_len,
                                          mres->lockname);
                        } else if (res->state & DLM_LOCK_RES_RECOVERING) {
                                /* caller should BUG */
                                mlog(ML_ERROR, "node is attempting to migrate "
                                     "lock %.*s, but marked as recovering!\n",
                                     mres->lockname_len, mres->lockname);
                                ret = -EFAULT;
                                spin_unlock(&res->spinlock);
                                goto leave;
                        }
                        res->state |= DLM_LOCK_RES_MIGRATING;
                }
                spin_unlock(&res->spinlock);
        } else {
                /* need to allocate, just like if it was
                 * mastered here normally  */
                res = dlm_new_lockres(dlm, mres->lockname, mres->lockname_len);
                if (!res)
                        goto leave;

                /* to match the ref that we would have gotten if
                 * dlm_lookup_lockres had succeeded */
                dlm_lockres_get(res);

                /* mark it as recovering/migrating and hash it */
                if (mres->flags & DLM_MRES_RECOVERY)
                        res->state |= DLM_LOCK_RES_RECOVERING;
                else
                        res->state |= DLM_LOCK_RES_MIGRATING;

                spin_lock(&dlm->spinlock);
                __dlm_insert_lockres(dlm, res);
                spin_unlock(&dlm->spinlock);

                /* now that the new lockres is inserted,
                 * make it usable by other processes */
                spin_lock(&res->spinlock);
                res->state &= ~DLM_LOCK_RES_IN_PROGRESS;
                spin_unlock(&res->spinlock);

                /* add an extra ref for just-allocated lockres 
                 * otherwise the lockres will be purged immediately */
                dlm_lockres_get(res);

        }

        /* at this point we have allocated everything we need,
         * and we have a hashed lockres with an extra ref and
         * the proper res->state flags. */
        ret = 0;
        if (mres->master == DLM_LOCK_RES_OWNER_UNKNOWN) {
                /* migration cannot have an unknown master */
                BUG_ON(!(mres->flags & DLM_MRES_RECOVERY));
                mlog(0, "recovery has passed me a lockres with an "
                          "unknown owner.. will need to requery: "
                          "%.*s\n", mres->lockname_len, mres->lockname);
        } else {
                spin_lock(&res->spinlock);
                dlm_change_lockres_owner(dlm, res, dlm->node_num);
                spin_unlock(&res->spinlock);
        }

        /* queue up work for dlm_mig_lockres_worker */
        dlm_grab(dlm);  /* get an extra ref for the work item */
        memcpy(buf, msg->buf, be16_to_cpu(msg->data_len));  /* copy the whole message */
        dlm_init_work_item(dlm, item, dlm_mig_lockres_worker, buf);
        item->u.ml.lockres = res; /* already have a ref */
        item->u.ml.real_master = real_master;
        spin_lock(&dlm->work_lock);
        list_add_tail(&item->list, &dlm->work_list);
        spin_unlock(&dlm->work_lock);
        schedule_work(&dlm->dispatched_work);

leave:
        dlm_put(dlm);
        if (ret < 0) {
                if (buf)
                        kfree(buf);
                if (item)
                        kfree(item);
        }

        mlog_exit(ret);
        return ret;
}


static void dlm_mig_lockres_worker(struct dlm_work_item *item, void *data)
{
        struct dlm_ctxt *dlm = data;
        struct dlm_migratable_lockres *mres;
        int ret = 0;
        struct dlm_lock_resource *res;
        u8 real_master;

        dlm = item->dlm;
        mres = (struct dlm_migratable_lockres *)data;

        res = item->u.ml.lockres;
        real_master = item->u.ml.real_master;

        if (real_master == DLM_LOCK_RES_OWNER_UNKNOWN) {
                /* this case is super-rare. only occurs if
                 * node death happens during migration. */
again:
                ret = dlm_lockres_master_requery(dlm, res, &real_master);
                if (ret < 0) {
                        mlog(0, "dlm_lockres_master_requery ret=%d\n",
                                  ret);
                        goto again;
                }
                if (real_master == DLM_LOCK_RES_OWNER_UNKNOWN) {
                        mlog(0, "lockres %.*s not claimed.  "
                                   "this node will take it.\n",
                                   res->lockname.len, res->lockname.name);
                } else {
                        mlog(0, "master needs to respond to sender "
                                  "that node %u still owns %.*s\n",
                                  real_master, res->lockname.len,
                                  res->lockname.name);
                        /* cannot touch this lockres */
                        goto leave;
                }
        }

        ret = dlm_process_recovery_data(dlm, res, mres);
        if (ret < 0)
                mlog(0, "dlm_process_recovery_data returned  %d\n", ret);
        else
                mlog(0, "dlm_process_recovery_data succeeded\n");

        if ((mres->flags & (DLM_MRES_MIGRATION|DLM_MRES_ALL_DONE)) ==
                           (DLM_MRES_MIGRATION|DLM_MRES_ALL_DONE)) {
                ret = dlm_finish_migration(dlm, res, mres->master);
                if (ret < 0)
                        mlog_errno(ret);
        }

leave:
        kfree(data);
        mlog_exit(ret);
}



static int dlm_lockres_master_requery(struct dlm_ctxt *dlm,
                                      struct dlm_lock_resource *res,
                                      u8 *real_master)
{
        struct dlm_node_iter iter;
        int nodenum;
        int ret = 0;

        *real_master = DLM_LOCK_RES_OWNER_UNKNOWN;

        /* we only reach here if one of the two nodes in a
         * migration died while the migration was in progress.
         * at this point we need to requery the master.  we
         * know that the new_master got as far as creating
         * an mle on at least one node, but we do not know
         * if any nodes had actually cleared the mle and set
         * the master to the new_master.  the old master
         * is supposed to set the owner to UNKNOWN in the
         * event of a new_master death, so the only possible
         * responses that we can get from nodes here are
         * that the master is new_master, or that the master
         * is UNKNOWN.
         * if all nodes come back with UNKNOWN then we know
         * the lock needs remastering here.
         * if any node comes back with a valid master, check
         * to see if that master is the one that we are
         * recovering.  if so, then the new_master died and
         * we need to remaster this lock.  if not, then the
         * new_master survived and that node will respond to
         * other nodes about the owner.
         * if there is an owner, this node needs to dump this
         * lockres and alert the sender that this lockres
         * was rejected. */
        spin_lock(&dlm->spinlock);
        dlm_node_iter_init(dlm->domain_map, &iter);
        spin_unlock(&dlm->spinlock);

        while ((nodenum = dlm_node_iter_next(&iter)) >= 0) {
                /* do not send to self */
                if (nodenum == dlm->node_num)
                        continue;
                ret = dlm_do_master_requery(dlm, res, nodenum, real_master);
                if (ret < 0) {
                        mlog_errno(ret);
                        BUG();
                        /* TODO: need to figure a way to restart this */
                }
                if (*real_master != DLM_LOCK_RES_OWNER_UNKNOWN) {
                        mlog(0, "lock master is %u\n", *real_master);
                        break;
                }
        }
        return ret;
}


static int dlm_do_master_requery(struct dlm_ctxt *dlm,
                                 struct dlm_lock_resource *res,
                                 u8 nodenum, u8 *real_master)
{
        int ret = -EINVAL;
        struct dlm_master_requery req;
        int status = DLM_LOCK_RES_OWNER_UNKNOWN;

        memset(&req, 0, sizeof(req));
        req.node_idx = dlm->node_num;
        req.namelen = res->lockname.len;
        memcpy(req.name, res->lockname.name, res->lockname.len);

        ret = o2net_send_message(DLM_MASTER_REQUERY_MSG, dlm->key,
                                 &req, sizeof(req), nodenum, &status);
        /* XXX: negative status not handled properly here. */
        if (ret < 0)
                mlog_errno(ret);
        else {
                BUG_ON(status < 0);
                BUG_ON(status > DLM_LOCK_RES_OWNER_UNKNOWN);
                *real_master = (u8) (status & 0xff);
                mlog(0, "node %u responded to master requery with %u\n",
                          nodenum, *real_master);
                ret = 0;
        }
        return ret;
}


/* this function cannot error, so unless the sending
 * or receiving of the message failed, the owner can
 * be trusted */
int dlm_master_requery_handler(struct o2net_msg *msg, u32 len, void *data)
{
        struct dlm_ctxt *dlm = data;
        struct dlm_master_requery *req = (struct dlm_master_requery *)msg->buf;
        struct dlm_lock_resource *res = NULL;
        int master = DLM_LOCK_RES_OWNER_UNKNOWN;
        u32 flags = DLM_ASSERT_MASTER_REQUERY;

        if (!dlm_grab(dlm)) {
                /* since the domain has gone away on this
                 * node, the proper response is UNKNOWN */
                return master;
        }

        spin_lock(&dlm->spinlock);
        res = __dlm_lookup_lockres(dlm, req->name, req->namelen);
        if (res) {
                spin_lock(&res->spinlock);
                master = res->owner;
                if (master == dlm->node_num) {
                        int ret = dlm_dispatch_assert_master(dlm, res,
                                                             0, 0, flags);
                        if (ret < 0) {
                                mlog_errno(-ENOMEM);
                                /* retry!? */
                                BUG();
                        }
                }
                spin_unlock(&res->spinlock);
        }
        spin_unlock(&dlm->spinlock);

        dlm_put(dlm);
        return master;
}

static inline struct list_head *
dlm_list_num_to_pointer(struct dlm_lock_resource *res, int list_num)
{
        struct list_head *ret;
        BUG_ON(list_num < 0);
        BUG_ON(list_num > 2);
        ret = &(res->granted);
        ret += list_num;
        return ret;
}
/* TODO: do ast flush business
 * TODO: do MIGRATING and RECOVERING spinning
 */

/*
* NOTE about in-flight requests during migration:
*
* Before attempting the migrate, the master has marked the lockres as
* MIGRATING and then flushed all of its pending ASTS.  So any in-flight
* requests either got queued before the MIGRATING flag got set, in which
* case the lock data will reflect the change and a return message is on
* the way, or the request failed to get in before MIGRATING got set.  In
* this case, the caller will be told to spin and wait for the MIGRATING
* flag to be dropped, then recheck the master.
* This holds true for the convert, cancel and unlock cases, and since lvb
* updates are tied to these same messages, it applies to lvb updates as
* well.  For the lock case, there is no way a lock can be on the master
* queue and not be on the secondary queue since the lock is always added
* locally first.  This means that the new target node will never be sent
* a lock that he doesn't already have on the list.
* In total, this means that the local lock is correct and should not be
* updated to match the one sent by the master.  Any messages sent back
* from the master before the MIGRATING flag will bring the lock properly
* up-to-date, and the change will be ordered properly for the waiter.
* We will *not* attempt to modify the lock underneath the waiter.
*/

static int dlm_process_recovery_data(struct dlm_ctxt *dlm,
                                     struct dlm_lock_resource *res,
                                     struct dlm_migratable_lockres *mres)
{
        struct dlm_migratable_lock *ml;
        struct list_head *queue;
        struct dlm_lock *newlock = NULL;
        struct dlm_lockstatus *lksb = NULL;
        int ret = 0;
        int i;
        struct list_head *iter;
        struct dlm_lock *lock = NULL;

        mlog(0, "running %d locks for this lockres\n", mres->num_locks);
        for (i=0; i<mres->num_locks; i++) {
                ml = &(mres->ml[i]);
                BUG_ON(ml->highest_blocked != LKM_IVMODE);
                newlock = NULL;
                lksb = NULL;

                queue = dlm_list_num_to_pointer(res, ml->list);

                /* if the lock is for the local node it needs to
                 * be moved to the proper location within the queue.
                 * do not allocate a new lock structure. */
                if (ml->node == dlm->node_num) {
                        /* MIGRATION ONLY! */
                        BUG_ON(!(mres->flags & DLM_MRES_MIGRATION));

                        spin_lock(&res->spinlock);
                        list_for_each(iter, queue) {
                                lock = list_entry (iter, struct dlm_lock, list);
                                if (lock->ml.cookie != ml->cookie)
                                        lock = NULL;
                                else
                                        break;
                        }

                        /* lock is always created locally first, and
                         * destroyed locally last.  it must be on the list */
                        if (!lock) {
                                mlog(ML_ERROR, "could not find local lock "
                                               "with cookie %"MLFu64"!\n",
                                     ml->cookie);
                                BUG();
                        }
                        BUG_ON(lock->ml.node != ml->node);

                        /* see NOTE above about why we do not update
                         * to match the master here */

                        /* move the lock to its proper place */
                        /* do not alter lock refcount.  switching lists. */
                        list_del_init(&lock->list);
                        list_add_tail(&lock->list, queue);
                        spin_unlock(&res->spinlock);

                        mlog(0, "just reordered a local lock!\n");
                        continue;
                }

                /* lock is for another node. */
                newlock = dlm_new_lock(ml->type, ml->node,
                                       be64_to_cpu(ml->cookie), NULL);
                if (!newlock) {
                        ret = -ENOMEM;
                        goto leave;
                }
                lksb = newlock->lksb;
                dlm_lock_attach_lockres(newlock, res);

                if (ml->convert_type != LKM_IVMODE) {
                        BUG_ON(queue != &res->converting);
                        newlock->ml.convert_type = ml->convert_type;
                }
                lksb->flags |= (ml->flags &
                                (DLM_LKSB_PUT_LVB|DLM_LKSB_GET_LVB));
                        
                if (mres->lvb[0]) {
                        if (lksb->flags & DLM_LKSB_PUT_LVB) {
                                /* other node was trying to update
                                 * lvb when node died.  recreate the
                                 * lksb with the updated lvb. */
                                memcpy(lksb->lvb, mres->lvb, DLM_LVB_LEN);
                        } else {
                                /* otherwise, the node is sending its 
                                 * most recent valid lvb info */
                                BUG_ON(ml->type != LKM_EXMODE &&
                                       ml->type != LKM_PRMODE);
                                if (res->lvb[0] && (ml->type == LKM_EXMODE ||
                                    memcmp(res->lvb, mres->lvb, DLM_LVB_LEN))) {
                                        mlog(ML_ERROR, "received bad lvb!\n");
                                        __dlm_print_one_lock_resource(res);
                                        BUG();
                                }
                                memcpy(res->lvb, mres->lvb, DLM_LVB_LEN);
                        }
                }


                /* NOTE:
                 * wrt lock queue ordering and recovery:
                 *    1. order of locks on granted queue is
                 *       meaningless.
                 *    2. order of locks on converting queue is
                 *       LOST with the node death.  sorry charlie.
                 *    3. order of locks on the blocked queue is
                 *       also LOST.
                 * order of locks does not affect integrity, it
                 * just means that a lock request may get pushed
                 * back in line as a result of the node death.
                 * also note that for a given node the lock order
                 * for its secondary queue locks is preserved
                 * relative to each other, but clearly *not*
                 * preserved relative to locks from other nodes.
                 */
                spin_lock(&res->spinlock);
                dlm_lock_get(newlock);
                list_add_tail(&newlock->list, queue);
                spin_unlock(&res->spinlock);
        }
        mlog(0, "done running all the locks\n");

leave:
        if (ret < 0) {
                mlog_errno(ret);
                if (newlock)
                        dlm_lock_put(newlock);
        }

        mlog_exit(ret);
        return ret;
}

void dlm_move_lockres_to_recovery_list(struct dlm_ctxt *dlm,
                                       struct dlm_lock_resource *res)
{
        int i;
        struct list_head *queue, *iter, *iter2;
        struct dlm_lock *lock;

        res->state |= DLM_LOCK_RES_RECOVERING;
        if (!list_empty(&res->recovering))
                list_del_init(&res->recovering);
        list_add_tail(&res->recovering, &dlm->reco.resources);

        /* find any pending locks and put them back on proper list */
        for (i=DLM_BLOCKED_LIST; i>=DLM_GRANTED_LIST; i--) {
                queue = dlm_list_idx_to_ptr(res, i);
                list_for_each_safe(iter, iter2, queue) {
                        lock = list_entry (iter, struct dlm_lock, list);
                        dlm_lock_get(lock);
                        if (lock->convert_pending) {
                                /* move converting lock back to granted */
                                BUG_ON(i != DLM_CONVERTING_LIST);
                                mlog(0, "node died with convert pending "
                                     "on %.*s. move back to granted list.\n",
                                     res->lockname.len, res->lockname.name);
                                dlm_revert_pending_convert(res, lock);
                                lock->convert_pending = 0;
                        } else if (lock->lock_pending) {
                                /* remove pending lock requests completely */
                                BUG_ON(i != DLM_BLOCKED_LIST);
                                mlog(0, "node died with lock pending "
                                     "on %.*s. remove from blocked list and skip.\n",
                                     res->lockname.len, res->lockname.name);
                                /* lock will be floating until ref in
                                 * dlmlock_remote is freed after the network
                                 * call returns.  ok for it to not be on any
                                 * list since no ast can be called
                                 * (the master is dead). */
                                dlm_revert_pending_lock(res, lock);
                                lock->lock_pending = 0;
                        } else if (lock->unlock_pending) {
                                /* if an unlock was in progress, treat as
                                 * if this had completed successfully
                                 * before sending this lock state to the
                                 * new master.  note that the dlm_unlock
                                 * call is still responsible for calling
                                 * the unlockast.  that will happen after
                                 * the network call times out.  for now,
                                 * just move lists to prepare the new
                                 * recovery master.  */
                                BUG_ON(i != DLM_GRANTED_LIST);
                                mlog(0, "node died with unlock pending "
                                     "on %.*s. remove from blocked list and skip.\n",
                                     res->lockname.len, res->lockname.name);
                                dlm_commit_pending_unlock(res, lock);
                                lock->unlock_pending = 0;
                        } else if (lock->cancel_pending) {
                                /* if a cancel was in progress, treat as
                                 * if this had completed successfully
                                 * before sending this lock state to the
                                 * new master */
                                BUG_ON(i != DLM_CONVERTING_LIST);
                                mlog(0, "node died with cancel pending "
                                     "on %.*s. move back to granted list.\n",
                                     res->lockname.len, res->lockname.name);
                                dlm_commit_pending_cancel(res, lock);
                                lock->cancel_pending = 0;
                        }
                        dlm_lock_put(lock);
                }
        }
}



/* removes all recovered locks from the recovery list.
 * sets the res->owner to the new master.
 * unsets the RECOVERY flag and wakes waiters. */
static void dlm_finish_local_lockres_recovery(struct dlm_ctxt *dlm,
                                              u8 dead_node, u8 new_master)
{
        int i;
        struct list_head *iter, *iter2, *bucket;
        struct dlm_lock_resource *res;

        mlog_entry_void();

        assert_spin_locked(&dlm->spinlock);

        list_for_each_safe(iter, iter2, &dlm->reco.resources) {
                res = list_entry (iter, struct dlm_lock_resource, recovering);
                if (res->owner == dead_node) {
                        list_del_init(&res->recovering);
                        spin_lock(&res->spinlock);
                        dlm_change_lockres_owner(dlm, res, new_master);
                        res->state &= ~DLM_LOCK_RES_RECOVERING;
                        __dlm_dirty_lockres(dlm, res);
                        spin_unlock(&res->spinlock);
                        wake_up(&res->wq);
                }
        }

        /* this will become unnecessary eventually, but
         * for now we need to run the whole hash, clear
         * the RECOVERING state and set the owner
         * if necessary */
        for (i=0; i<DLM_HASH_SIZE; i++) {
                bucket = &(dlm->resources[i]);
                list_for_each(iter, bucket) {
                        res = list_entry (iter, struct dlm_lock_resource, list);
                        if (res->state & DLM_LOCK_RES_RECOVERING) {
                                if (res->owner == dead_node) {
                                        mlog(0, "(this=%u) res %.*s owner=%u "
                                             "was not on recovering list, but "
                                             "clearing state anyway\n",
                                             dlm->node_num, res->lockname.len,
                                             res->lockname.name, new_master);
                                } else if (res->owner == dlm->node_num) {
                                        mlog(0, "(this=%u) res %.*s owner=%u "
                                             "was not on recovering list, "
                                             "owner is THIS node, clearing\n",
                                             dlm->node_num, res->lockname.len,
                                             res->lockname.name, new_master);
                                } else
                                        continue;

                                spin_lock(&res->spinlock);
                                dlm_change_lockres_owner(dlm, res, new_master);
                                res->state &= ~DLM_LOCK_RES_RECOVERING;
                                __dlm_dirty_lockres(dlm, res);
                                spin_unlock(&res->spinlock);
                                wake_up(&res->wq);
                        }
                }
        }
}

static inline int dlm_lvb_needs_invalidation(struct dlm_lock *lock, int local)
{
        if (local) {
                if (lock->ml.type != LKM_EXMODE &&
                    lock->ml.type != LKM_PRMODE)
                        return 1;
        } else if (lock->ml.type == LKM_EXMODE)
                return 1;
        return 0;
}

static void dlm_revalidate_lvb(struct dlm_ctxt *dlm,
                               struct dlm_lock_resource *res, u8 dead_node)
{
        struct list_head *iter, *queue;
        struct dlm_lock *lock;
        int blank_lvb = 0, local = 0;
        int i;
        u8 search_node;

        assert_spin_locked(&dlm->spinlock);
        assert_spin_locked(&res->spinlock);

        if (res->owner == dlm->node_num)
                /* if this node owned the lockres, and if the dead node 
                 * had an EX when he died, blank out the lvb */
                search_node = dead_node;
        else {
                /* if this is a secondary lockres, and we had no EX or PR
                 * locks granted, we can no longer trust the lvb */
                search_node = dlm->node_num;
                local = 1;  /* check local state for valid lvb */
        }

        for (i=DLM_GRANTED_LIST; i<=DLM_CONVERTING_LIST; i++) {
                queue = dlm_list_idx_to_ptr(res, i);
                list_for_each(iter, queue) {
                        lock = list_entry (iter, struct dlm_lock, list);
                        if (lock->ml.node == search_node) {
                                if (dlm_lvb_needs_invalidation(lock, local)) {
                                        /* zero the lksb lvb and lockres lvb */
                                        blank_lvb = 1;
                                        memset(lock->lksb->lvb, 0, DLM_LVB_LEN);
                                }
                        }
                }
        }

        if (blank_lvb) {
                mlog(0, "clearing %.*s lvb, dead node %u had EX\n",
                     res->lockname.len, res->lockname.name, dead_node);
                memset(res->lvb, 0, DLM_LVB_LEN);
        }
}

static void dlm_free_dead_locks(struct dlm_ctxt *dlm,
                                struct dlm_lock_resource *res, u8 dead_node)
{
        struct list_head *iter, *tmpiter;
        struct dlm_lock *lock;

        /* this node is the lockres master:
         * 1) remove any stale locks for the dead node
         * 2) if the dead node had an EX when he died, blank out the lvb 
         */
        assert_spin_locked(&dlm->spinlock);
        assert_spin_locked(&res->spinlock);

        /* TODO: check pending_asts, pending_basts here */
        list_for_each_safe(iter, tmpiter, &res->granted) {
                lock = list_entry (iter, struct dlm_lock, list);
                if (lock->ml.node == dead_node) {
                        list_del_init(&lock->list);
                        dlm_lock_put(lock);
                }
        }
        list_for_each_safe(iter, tmpiter, &res->converting) {
                lock = list_entry (iter, struct dlm_lock, list);
                if (lock->ml.node == dead_node) {
                        list_del_init(&lock->list);
                        dlm_lock_put(lock);
                }
        }
        list_for_each_safe(iter, tmpiter, &res->blocked) {
                lock = list_entry (iter, struct dlm_lock, list);
                if (lock->ml.node == dead_node) {
                        list_del_init(&lock->list);
                        dlm_lock_put(lock);
                }
        }

        /* do not kick thread yet */
        __dlm_dirty_lockres(dlm, res);
}

/* if this node is the recovery master, and there are no
 * locks for a given lockres owned by this node that are in
 * either PR or EX mode, zero out the lvb before requesting.
 *
 */


static void dlm_do_local_recovery_cleanup(struct dlm_ctxt *dlm, u8 dead_node)
{
        struct list_head *iter;
        struct dlm_lock_resource *res;
        int i;
        struct list_head *bucket;
        struct dlm_lock *lock;


        /* purge any stale mles */
        dlm_clean_master_list(dlm, dead_node);

        /*
         * now clean up all lock resources.  there are two rules:
         *
         * 1) if the dead node was the master, move the lockres
         *    to the recovering list.  set the RECOVERING flag.
         *    this lockres needs to be cleaned up before it can
         *    be used further.
         *
         * 2) if this node was the master, remove all locks from
         *    each of the lockres queues that were owned by the
         *    dead node.  once recovery finishes, the dlm thread
         *    can be kicked again to see if any ASTs or BASTs
         *    need to be fired as a result.
         */
        for (i=0; i<DLM_HASH_SIZE; i++) {
                bucket = &(dlm->resources[i]);
                list_for_each(iter, bucket) {
                        res = list_entry (iter, struct dlm_lock_resource, list);
                        /* always prune any $RECOVERY entries for dead nodes,
                         * otherwise hangs can occur during later recovery */
                        if (dlm_is_recovery_lock(res->lockname.name,
                                                 res->lockname.len)) {
                                spin_lock(&res->spinlock);
                                list_for_each_entry(lock, &res->granted, list) {
                                        if (lock->ml.node == dead_node) {
                                                mlog(0, "AHA! there was "
                                                     "a $RECOVERY lock for dead "
                                                     "node %u (%s)!\n",
                                                     dead_node, dlm->name);
                                                list_del_init(&lock->list);
                                                dlm_lock_put(lock);
                                                break;
                                        }
                                }
                                spin_unlock(&res->spinlock);
                                continue;
                        }                       
                        spin_lock(&res->spinlock);
                        /* zero the lvb if necessary */
                        dlm_revalidate_lvb(dlm, res, dead_node);
                        if (res->owner == dead_node)
                                dlm_move_lockres_to_recovery_list(dlm, res);
                        else if (res->owner == dlm->node_num) {
                                dlm_free_dead_locks(dlm, res, dead_node);
                                __dlm_lockres_calc_usage(dlm, res);
                        }
                        spin_unlock(&res->spinlock);
                }
        }

}

static void __dlm_hb_node_down(struct dlm_ctxt *dlm, int idx)
{
        assert_spin_locked(&dlm->spinlock);

        /* check to see if the node is already considered dead */
        if (!test_bit(idx, dlm->live_nodes_map)) {
                mlog(0, "for domain %s, node %d is already dead. "
                     "another node likely did recovery already.\n",
                     dlm->name, idx);
                return;
        }

        /* check to see if we do not care about this node */
        if (!test_bit(idx, dlm->domain_map)) {
                /* This also catches the case that we get a node down
                 * but haven't joined the domain yet. */
                mlog(0, "node %u already removed from domain!\n", idx);
                return;
        }

        clear_bit(idx, dlm->live_nodes_map);

        /* Clean up join state on node death. */
        if (dlm->joining_node == idx) {
                mlog(0, "Clearing join state for node %u\n", idx);
                __dlm_set_joining_node(dlm, DLM_LOCK_RES_OWNER_UNKNOWN);
        }

        /* make sure local cleanup occurs before the heartbeat events */
        if (!test_bit(idx, dlm->recovery_map))
                dlm_do_local_recovery_cleanup(dlm, idx);

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

        mlog(0, "node %u being removed from domain map!\n", idx);
        clear_bit(idx, dlm->domain_map);
        /* wake up migration waiters if a node goes down.
         * perhaps later we can genericize this for other waiters. */
        wake_up(&dlm->migration_wq);

        if (test_bit(idx, dlm->recovery_map))
                mlog(0, "domain %s, node %u already added "
                     "to recovery map!\n", dlm->name, idx);
        else
                set_bit(idx, dlm->recovery_map);
}

void dlm_hb_node_down_cb(struct o2nm_node *node, int idx, void *data)
{
        struct dlm_ctxt *dlm = data;

        if (!dlm_grab(dlm))
                return;

        spin_lock(&dlm->spinlock);
        __dlm_hb_node_down(dlm, idx);
        spin_unlock(&dlm->spinlock);

        dlm_put(dlm);
}

void dlm_hb_node_up_cb(struct o2nm_node *node, int idx, void *data)
{
        struct dlm_ctxt *dlm = data;

        if (!dlm_grab(dlm))
                return;

        spin_lock(&dlm->spinlock);
        set_bit(idx, dlm->live_nodes_map);
        /* do NOT notify mle attached to the heartbeat events.
         * new nodes are not interesting in mastery until joined. */
        spin_unlock(&dlm->spinlock);

        dlm_put(dlm);
}

static void dlm_reco_ast(void *astdata)
{
        struct dlm_ctxt *dlm = astdata;
        mlog(0, "ast for recovery lock fired!, this=%u, dlm=%s\n",
             dlm->node_num, dlm->name);
}
static void dlm_reco_bast(void *astdata, int blocked_type)
{
        struct dlm_ctxt *dlm = astdata;
        mlog(0, "bast for recovery lock fired!, this=%u, dlm=%s\n",
             dlm->node_num, dlm->name);
}
static void dlm_reco_unlock_ast(void *astdata, enum dlm_status st)
{
        mlog(0, "unlockast for recovery lock fired!\n");
}

/*
 * dlm_pick_recovery_master will continually attempt to use
 * dlmlock() on the special "$RECOVERY" lockres with the
 * LKM_NOQUEUE flag to get an EX.  every thread that enters
 * this function on each node racing to become the recovery
 * master will not stop attempting this until either:
 * a) this node gets the EX (and becomes the recovery master),
 * or b) dlm->reco.new_master gets set to some nodenum 
 * != O2NM_INVALID_NODE_NUM (another node will do the reco).
 * so each time a recovery master is needed, the entire cluster
 * will sync at this point.  if the new master dies, that will
 * be detected in dlm_do_recovery */
static int dlm_pick_recovery_master(struct dlm_ctxt *dlm)
{
        enum dlm_status ret;
        struct dlm_lockstatus lksb;
        int status = -EINVAL;

        mlog(0, "starting recovery of %s at %lu, dead=%u, this=%u\n",
             dlm->name, jiffies, dlm->reco.dead_node, dlm->node_num);
again:  
        memset(&lksb, 0, sizeof(lksb));

        ret = dlmlock(dlm, LKM_EXMODE, &lksb, LKM_NOQUEUE|LKM_RECOVERY,
                      DLM_RECOVERY_LOCK_NAME, dlm_reco_ast, dlm, dlm_reco_bast);

        mlog(0, "%s: dlmlock($RECOVERY) returned %d, lksb=%d\n",
             dlm->name, ret, lksb.status);

        if (ret == DLM_NORMAL) {
                mlog(0, "dlm=%s dlmlock says I got it (this=%u)\n",
                     dlm->name, dlm->node_num);
                
                /* got the EX lock.  check to see if another node 
                 * just became the reco master */
                if (dlm_reco_master_ready(dlm)) {
                        mlog(0, "%s: got reco EX lock, but %u will "
                             "do the recovery\n", dlm->name,
                             dlm->reco.new_master);
                        status = -EEXIST;
                } else {
                        status = dlm_send_begin_reco_message(dlm,
                                      dlm->reco.dead_node);
                        /* this always succeeds */
                        BUG_ON(status);

                        /* set the new_master to this node */
                        spin_lock(&dlm->spinlock);
                        dlm->reco.new_master = dlm->node_num;
                        spin_unlock(&dlm->spinlock);
                }

                /* recovery lock is a special case.  ast will not get fired,
                 * so just go ahead and unlock it. */
                ret = dlmunlock(dlm, &lksb, 0, dlm_reco_unlock_ast, dlm);
                if (ret == DLM_DENIED) {
                        mlog(0, "got DLM_DENIED, trying LKM_CANCEL\n");
                        ret = dlmunlock(dlm, &lksb, LKM_CANCEL, dlm_reco_unlock_ast, dlm);
                }
                if (ret != DLM_NORMAL) {
                        /* this would really suck. this could only happen
                         * if there was a network error during the unlock
                         * because of node death.  this means the unlock
                         * is actually "done" and the lock structure is
                         * even freed.  we can continue, but only
                         * because this specific lock name is special. */
                        mlog(ML_ERROR, "dlmunlock returned %d\n", ret);
                }
        } else if (ret == DLM_NOTQUEUED) {
                mlog(0, "dlm=%s dlmlock says another node got it (this=%u)\n",
                     dlm->name, dlm->node_num);
                /* another node is master. wait on
                 * reco.new_master != O2NM_INVALID_NODE_NUM 
                 * for at most one second */
                wait_event_timeout(dlm->dlm_reco_thread_wq,
                                         dlm_reco_master_ready(dlm),
                                         msecs_to_jiffies(1000));
                if (!dlm_reco_master_ready(dlm)) {
                        mlog(0, "%s: reco master taking awhile\n",
                             dlm->name);
                        goto again;
                }
                /* another node has informed this one that it is reco master */
                mlog(0, "%s: reco master %u is ready to recover %u\n",
                     dlm->name, dlm->reco.new_master, dlm->reco.dead_node);
                status = -EEXIST;
        } else {
                struct dlm_lock_resource *res;

                /* dlmlock returned something other than NOTQUEUED or NORMAL */
                mlog(ML_ERROR, "%s: got %s from dlmlock($RECOVERY), "
                     "lksb.status=%s\n", dlm->name, dlm_errname(ret),
                     dlm_errname(lksb.status));
                res = dlm_lookup_lockres(dlm, DLM_RECOVERY_LOCK_NAME,
                                         DLM_RECOVERY_LOCK_NAME_LEN);
                if (res) {
                        dlm_print_one_lock_resource(res);
                        dlm_lockres_put(res);
                } else {
                        mlog(ML_ERROR, "recovery lock not found\n");
                }
                BUG();
        }

        return status;
}

static int dlm_send_begin_reco_message(struct dlm_ctxt *dlm, u8 dead_node)
{
        struct dlm_begin_reco br;
        int ret = 0;
        struct dlm_node_iter iter;
        int nodenum;
        int status;

        mlog_entry("%u\n", dead_node);

        mlog(0, "dead node is %u\n", dead_node);

        spin_lock(&dlm->spinlock);
        dlm_node_iter_init(dlm->domain_map, &iter);
        spin_unlock(&dlm->spinlock);

        clear_bit(dead_node, iter.node_map);

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

        while ((nodenum = dlm_node_iter_next(&iter)) >= 0) {
                ret = 0;
                if (nodenum == dead_node) {
                        mlog(0, "not sending begin reco to dead node "
                                  "%u\n", dead_node);
                        continue;
                }
                if (nodenum == dlm->node_num) {
                        mlog(0, "not sending begin reco to self\n");
                        continue;
                }
retry:
                ret = -EINVAL;
                mlog(0, "attempting to send begin reco msg to %d\n",
                          nodenum);
                ret = o2net_send_message(DLM_BEGIN_RECO_MSG, dlm->key,
                                         &br, sizeof(br), nodenum, &status);
                /* negative status is handled ok by caller here */
                if (ret >= 0)
                        ret = status;
                if (dlm_is_host_down(ret)) {
                        /* node is down.  not involved in recovery
                         * so just keep going */
                        mlog(0, "%s: node %u was down when sending "
                             "begin reco msg (%d)\n", dlm->name, nodenum, ret);
                        ret = 0;
                }
                if (ret < 0) {
                        struct dlm_lock_resource *res;
                        /* this is now a serious problem, possibly ENOMEM 
                         * in the network stack.  must retry */
                        mlog_errno(ret);
                        mlog(ML_ERROR, "begin reco of dlm %s to node %u "
                            " returned %d\n", dlm->name, nodenum, ret);
                        res = dlm_lookup_lockres(dlm, DLM_RECOVERY_LOCK_NAME,
                                                 DLM_RECOVERY_LOCK_NAME_LEN);
                        if (res) {
                                dlm_print_one_lock_resource(res);
                                dlm_lockres_put(res);
                        } else {
                                mlog(ML_ERROR, "recovery lock not found\n");
                        }
                        /* sleep for a bit in hopes that we can avoid 
                         * another ENOMEM */
                        msleep(100);
                        goto retry;
                }
        }

        return ret;
}

int dlm_begin_reco_handler(struct o2net_msg *msg, u32 len, void *data)
{
        struct dlm_ctxt *dlm = data;
        struct dlm_begin_reco *br = (struct dlm_begin_reco *)msg->buf;

        /* ok to return 0, domain has gone away */
        if (!dlm_grab(dlm))
                return 0;

        mlog(0, "node %u wants to recover node %u\n",
                  br->node_idx, br->dead_node);

        dlm_fire_domain_eviction_callbacks(dlm, br->dead_node);

        spin_lock(&dlm->spinlock);
        if (dlm->reco.new_master != O2NM_INVALID_NODE_NUM) {
                if (test_bit(dlm->reco.new_master, dlm->recovery_map)) {
                        mlog(0, "%s: new_master %u died, changing "
                             "to %u\n", dlm->name, dlm->reco.new_master,
                             br->node_idx);
                } else {
                        mlog(0, "%s: new_master %u NOT DEAD, changing "
                             "to %u\n", dlm->name, dlm->reco.new_master,
                             br->node_idx);
                        /* may not have seen the new master as dead yet */
                }
        }
        if (dlm->reco.dead_node != O2NM_INVALID_NODE_NUM) {
                mlog(ML_NOTICE, "%s: dead_node previously set to %u, "
                     "node %u changing it to %u\n", dlm->name, 
                     dlm->reco.dead_node, br->node_idx, br->dead_node);
        }
        dlm->reco.new_master = br->node_idx;
        dlm->reco.dead_node = br->dead_node;
        if (!test_bit(br->dead_node, dlm->recovery_map)) {
                mlog(0, "recovery master %u sees %u as dead, but this "
                     "node has not yet.  marking %u as dead\n",
                     br->node_idx, br->dead_node, br->dead_node);
                if (!test_bit(br->dead_node, dlm->domain_map) ||
                    !test_bit(br->dead_node, dlm->live_nodes_map))
                        mlog(0, "%u not in domain/live_nodes map "
                             "so setting it in reco map manually\n",
                             br->dead_node);
                set_bit(br->dead_node, dlm->recovery_map);
                __dlm_hb_node_down(dlm, br->dead_node);
        }
        spin_unlock(&dlm->spinlock);

        dlm_kick_recovery_thread(dlm);
        dlm_put(dlm);
        return 0;
}

static int dlm_send_finalize_reco_message(struct dlm_ctxt *dlm)
{
        int ret = 0;
        struct dlm_finalize_reco fr;
        struct dlm_node_iter iter;
        int nodenum;
        int status;

        mlog(0, "finishing recovery for node %s:%u\n",
             dlm->name, dlm->reco.dead_node);

        spin_lock(&dlm->spinlock);
        dlm_node_iter_init(dlm->domain_map, &iter);
        spin_unlock(&dlm->spinlock);

        memset(&fr, 0, sizeof(fr));
        fr.node_idx = dlm->node_num;
        fr.dead_node = dlm->reco.dead_node;

        while ((nodenum = dlm_node_iter_next(&iter)) >= 0) {
                if (nodenum == dlm->node_num)
                        continue;
                ret = o2net_send_message(DLM_FINALIZE_RECO_MSG, dlm->key,
                                         &fr, sizeof(fr), nodenum, &status);
                if (ret >= 0) {
                        ret = status;
                        if (dlm_is_host_down(ret)) {
                                /* this has no effect on this recovery 
                                 * session, so set the status to zero to 
                                 * finish out the last recovery */
                                mlog(ML_ERROR, "node %u went down after this "
                                     "node finished recovery.\n", nodenum);
                                ret = 0;
                        }
                }
                if (ret < 0) {
                        mlog_errno(ret);
                        break;
                }
        }

        return ret;
}

int dlm_finalize_reco_handler(struct o2net_msg *msg, u32 len, void *data)
{
        struct dlm_ctxt *dlm = data;
        struct dlm_finalize_reco *fr = (struct dlm_finalize_reco *)msg->buf;

        /* ok to return 0, domain has gone away */
        if (!dlm_grab(dlm))
                return 0;

        mlog(0, "node %u finalizing recovery of node %u\n",
             fr->node_idx, fr->dead_node);

        spin_lock(&dlm->spinlock);

        if (dlm->reco.new_master != fr->node_idx) {
                mlog(ML_ERROR, "node %u sent recovery finalize msg, but node "
                     "%u is supposed to be the new master, dead=%u\n",
                     fr->node_idx, dlm->reco.new_master, fr->dead_node);
                BUG();
        }
        if (dlm->reco.dead_node != fr->dead_node) {
                mlog(ML_ERROR, "node %u sent recovery finalize msg for dead "
                     "node %u, but node %u is supposed to be dead\n",
                     fr->node_idx, fr->dead_node, dlm->reco.dead_node);
                BUG();
        }

        dlm_finish_local_lockres_recovery(dlm, fr->dead_node, fr->node_idx);

        spin_unlock(&dlm->spinlock);

        dlm_reset_recovery(dlm);

        dlm_kick_recovery_thread(dlm);
        dlm_put(dlm);
        return 0;
}