dlmmaster.c

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/* -*- mode: c; c-basic-offset: 8; -*-
 * vim: noexpandtab sw=8 ts=8 sts=0:
 *
 * dlmmod.c
 *
 * standalone DLM module
 *
 * 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/init.h>
#include <linux/sysctl.h>
#include <linux/random.h>
#include <linux/blkdev.h>
#include <linux/socket.h>
#include <linux/inet.h>
#include <linux/spinlock.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"
#include "dlmdebug.h"

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

static void dlm_mle_node_down(struct dlm_ctxt *dlm,
                  struct dlm_master_list_entry *mle,
                  struct o2nm_node *node,
                  int idx);
static void dlm_mle_node_up(struct dlm_ctxt *dlm,
                struct dlm_master_list_entry *mle,
                struct o2nm_node *node,
                int idx);

static void dlm_assert_master_worker(struct dlm_work_item *item, void *data);
static int dlm_do_assert_master(struct dlm_ctxt *dlm,
                struct dlm_lock_resource *res,
                void *nodemap, u32 flags);
static void dlm_deref_lockres_worker(struct dlm_work_item *item, void *data);

static inline int dlm_mle_equal(struct dlm_ctxt *dlm,
                struct dlm_master_list_entry *mle,
                const char *name,
                unsigned int namelen)
{
    if (dlm != mle->dlm)
        return 0;

    if (namelen != mle->mnamelen ||
        memcmp(name, mle->mname, namelen) != 0)
        return 0;

    return 1;
}

static struct kmem_cache *dlm_lockres_cache = NULL;
static struct kmem_cache *dlm_lockname_cache = NULL;
static struct kmem_cache *dlm_mle_cache = NULL;

static void dlm_mle_release(struct kref *kref);
static void dlm_init_mle(struct dlm_master_list_entry *mle,
            enum dlm_mle_type type,
            struct dlm_ctxt *dlm,
            struct dlm_lock_resource *res,
            const char *name,
            unsigned int namelen);
static void dlm_put_mle(struct dlm_master_list_entry *mle);
static void __dlm_put_mle(struct dlm_master_list_entry *mle);
static int dlm_find_mle(struct dlm_ctxt *dlm,
            struct dlm_master_list_entry **mle,
            char *name, unsigned int namelen);

static int dlm_do_master_request(struct dlm_lock_resource *res,
                 struct dlm_master_list_entry *mle, int to);


static int dlm_wait_for_lock_mastery(struct dlm_ctxt *dlm,
                     struct dlm_lock_resource *res,
                     struct dlm_master_list_entry *mle,
                     int *blocked);
static int dlm_restart_lock_mastery(struct dlm_ctxt *dlm,
                    struct dlm_lock_resource *res,
                    struct dlm_master_list_entry *mle,
                    int blocked);
static int dlm_add_migration_mle(struct dlm_ctxt *dlm,
                 struct dlm_lock_resource *res,
                 struct dlm_master_list_entry *mle,
                 struct dlm_master_list_entry **oldmle,
                 const char *name, unsigned int namelen,
                 u8 new_master, u8 master);

static u8 dlm_pick_migration_target(struct dlm_ctxt *dlm,
                    struct dlm_lock_resource *res);
static void dlm_remove_nonlocal_locks(struct dlm_ctxt *dlm,
                      struct dlm_lock_resource *res);
static int dlm_mark_lockres_migrating(struct dlm_ctxt *dlm,
                       struct dlm_lock_resource *res,
                       u8 target);
static int dlm_pre_master_reco_lockres(struct dlm_ctxt *dlm,
                       struct dlm_lock_resource *res);


int dlm_is_host_down(int errno)
{
    switch (errno) {
        case -EBADF:
        case -ECONNREFUSED:
        case -ENOTCONN:
        case -ECONNRESET:
        case -EPIPE:
        case -EHOSTDOWN:
        case -EHOSTUNREACH:
        case -ETIMEDOUT:
        case -ECONNABORTED:
        case -ENETDOWN:
        case -ENETUNREACH:
        case -ENETRESET:
        case -ESHUTDOWN:
        case -ENOPROTOOPT:
        case -EINVAL:   /* if returned from our tcp code,
                   this means there is no socket */
            return 1;
    }
    return 0;
}


/*
 * MASTER LIST FUNCTIONS
 */


/*
 * regarding master list entries and heartbeat callbacks:
 *
 * in order to avoid sleeping and allocation that occurs in
 * heartbeat, master list entries are simply attached to the
 * dlm's established heartbeat callbacks.  the mle is attached
 * when it is created, and since the dlm->spinlock is held at
 * that time, any heartbeat event will be properly discovered
 * by the mle.  the mle needs to be detached from the
 * dlm->mle_hb_events list as soon as heartbeat events are no
 * longer useful to the mle, and before the mle is freed.
 *
 * as a general rule, heartbeat events are no longer needed by
 * the mle once an "answer" regarding the lock master has been
 * received.
 */
static inline void __dlm_mle_attach_hb_events(struct dlm_ctxt *dlm,
                          struct dlm_master_list_entry *mle)
{
    assert_spin_locked(&dlm->spinlock);

    list_add_tail(&mle->hb_events, &dlm->mle_hb_events);
}


static inline void __dlm_mle_detach_hb_events(struct dlm_ctxt *dlm,
                          struct dlm_master_list_entry *mle)
{
    if (!list_empty(&mle->hb_events))
        list_del_init(&mle->hb_events);
}


static inline void dlm_mle_detach_hb_events(struct dlm_ctxt *dlm,
                        struct dlm_master_list_entry *mle)
{
    spin_lock(&dlm->spinlock);
    __dlm_mle_detach_hb_events(dlm, mle);
    spin_unlock(&dlm->spinlock);
}

static void dlm_get_mle_inuse(struct dlm_master_list_entry *mle)
{
    struct dlm_ctxt *dlm;
    dlm = mle->dlm;

    assert_spin_locked(&dlm->spinlock);
    assert_spin_locked(&dlm->master_lock);
    mle->inuse++;
    kref_get(&mle->mle_refs);
}

static void dlm_put_mle_inuse(struct dlm_master_list_entry *mle)
{
    struct dlm_ctxt *dlm;
    dlm = mle->dlm;

    spin_lock(&dlm->spinlock);
    spin_lock(&dlm->master_lock);
    mle->inuse--;
    __dlm_put_mle(mle);
    spin_unlock(&dlm->master_lock);
    spin_unlock(&dlm->spinlock);

}

/* remove from list and free */
static void __dlm_put_mle(struct dlm_master_list_entry *mle)
{
    struct dlm_ctxt *dlm;
    dlm = mle->dlm;

    assert_spin_locked(&dlm->spinlock);
    assert_spin_locked(&dlm->master_lock);
    if (!atomic_read(&mle->mle_refs.refcount)) {
        /* this may or may not crash, but who cares.
         * it's a BUG. */
        mlog(ML_ERROR, "bad mle: %p\n", mle);
        dlm_print_one_mle(mle);
        BUG();
    } else
        kref_put(&mle->mle_refs, dlm_mle_release);
}


/* must not have any spinlocks coming in */
static void dlm_put_mle(struct dlm_master_list_entry *mle)
{
    struct dlm_ctxt *dlm;
    dlm = mle->dlm;

    spin_lock(&dlm->spinlock);
    spin_lock(&dlm->master_lock);
    __dlm_put_mle(mle);
    spin_unlock(&dlm->master_lock);
    spin_unlock(&dlm->spinlock);
}

static inline void dlm_get_mle(struct dlm_master_list_entry *mle)
{
    kref_get(&mle->mle_refs);
}

static void dlm_init_mle(struct dlm_master_list_entry *mle,
            enum dlm_mle_type type,
            struct dlm_ctxt *dlm,
            struct dlm_lock_resource *res,
            const char *name,
            unsigned int namelen)
{
    assert_spin_locked(&dlm->spinlock);

    mle->dlm = dlm;
    mle->type = type;
    INIT_HLIST_NODE(&mle->master_hash_node);
    INIT_LIST_HEAD(&mle->hb_events);
    memset(mle->maybe_map, 0, sizeof(mle->maybe_map));
    spin_lock_init(&mle->spinlock);
    init_waitqueue_head(&mle->wq);
    atomic_set(&mle->woken, 0);
    kref_init(&mle->mle_refs);
    memset(mle->response_map, 0, sizeof(mle->response_map));
    mle->master = O2NM_MAX_NODES;
    mle->new_master = O2NM_MAX_NODES;
    mle->inuse = 0;

    BUG_ON(mle->type != DLM_MLE_BLOCK &&
           mle->type != DLM_MLE_MASTER &&
           mle->type != DLM_MLE_MIGRATION);

    if (mle->type == DLM_MLE_MASTER) {
        BUG_ON(!res);
        mle->mleres = res;
        memcpy(mle->mname, res->lockname.name, res->lockname.len);
        mle->mnamelen = res->lockname.len;
        mle->mnamehash = res->lockname.hash;
    } else {
        BUG_ON(!name);
        mle->mleres = NULL;
        memcpy(mle->mname, name, namelen);
        mle->mnamelen = namelen;
        mle->mnamehash = dlm_lockid_hash(name, namelen);
    }

    atomic_inc(&dlm->mle_tot_count[mle->type]);
    atomic_inc(&dlm->mle_cur_count[mle->type]);

    /* copy off the node_map and register hb callbacks on our copy */
    memcpy(mle->node_map, dlm->domain_map, sizeof(mle->node_map));
    memcpy(mle->vote_map, dlm->domain_map, sizeof(mle->vote_map));
    clear_bit(dlm->node_num, mle->vote_map);
    clear_bit(dlm->node_num, mle->node_map);

    /* attach the mle to the domain node up/down events */
    __dlm_mle_attach_hb_events(dlm, mle);
}

void __dlm_unlink_mle(struct dlm_ctxt *dlm, struct dlm_master_list_entry *mle)
{
    assert_spin_locked(&dlm->spinlock);
    assert_spin_locked(&dlm->master_lock);

    if (!hlist_unhashed(&mle->master_hash_node))
        hlist_del_init(&mle->master_hash_node);
}

void __dlm_insert_mle(struct dlm_ctxt *dlm, struct dlm_master_list_entry *mle)
{
    struct hlist_head *bucket;

    assert_spin_locked(&dlm->master_lock);

    bucket = dlm_master_hash(dlm, mle->mnamehash);
    hlist_add_head(&mle->master_hash_node, bucket);
}

/* returns 1 if found, 0 if not */
static int dlm_find_mle(struct dlm_ctxt *dlm,
            struct dlm_master_list_entry **mle,
            char *name, unsigned int namelen)
{
    struct dlm_master_list_entry *tmpmle;
    struct hlist_head *bucket;
    struct hlist_node *list;
    unsigned int hash;

    assert_spin_locked(&dlm->master_lock);

    hash = dlm_lockid_hash(name, namelen);
    bucket = dlm_master_hash(dlm, hash);
    hlist_for_each(list, bucket) {
        tmpmle = hlist_entry(list, struct dlm_master_list_entry,
                     master_hash_node);
        if (!dlm_mle_equal(dlm, tmpmle, name, namelen))
            continue;
        dlm_get_mle(tmpmle);
        *mle = tmpmle;
        return 1;
    }
    return 0;
}

void dlm_hb_event_notify_attached(struct dlm_ctxt *dlm, int idx, int node_up)
{
    struct dlm_master_list_entry *mle;

    assert_spin_locked(&dlm->spinlock);

    list_for_each_entry(mle, &dlm->mle_hb_events, hb_events) {
        if (node_up)
            dlm_mle_node_up(dlm, mle, NULL, idx);
        else
            dlm_mle_node_down(dlm, mle, NULL, idx);
    }
}

static void dlm_mle_node_down(struct dlm_ctxt *dlm,
                  struct dlm_master_list_entry *mle,
                  struct o2nm_node *node, int idx)
{
    spin_lock(&mle->spinlock);

    if (!test_bit(idx, mle->node_map))
        mlog(0, "node %u already removed from nodemap!\n", idx);
    else
        clear_bit(idx, mle->node_map);

    spin_unlock(&mle->spinlock);
}

static void dlm_mle_node_up(struct dlm_ctxt *dlm,
                struct dlm_master_list_entry *mle,
                struct o2nm_node *node, int idx)
{
    spin_lock(&mle->spinlock);

    if (test_bit(idx, mle->node_map))
        mlog(0, "node %u already in node map!\n", idx);
    else
        set_bit(idx, mle->node_map);

    spin_unlock(&mle->spinlock);
}


int dlm_init_mle_cache(void)
{
    dlm_mle_cache = kmem_cache_create("o2dlm_mle",
                      sizeof(struct dlm_master_list_entry),
                      0, SLAB_HWCACHE_ALIGN,
                      NULL);
    if (dlm_mle_cache == NULL)
        return -ENOMEM;
    return 0;
}

void dlm_destroy_mle_cache(void)
{
    if (dlm_mle_cache)
        kmem_cache_destroy(dlm_mle_cache);
}

static void dlm_mle_release(struct kref *kref)
{
    struct dlm_master_list_entry *mle;
    struct dlm_ctxt *dlm;

    mle = container_of(kref, struct dlm_master_list_entry, mle_refs);
    dlm = mle->dlm;

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

    mlog(0, "Releasing mle for %.*s, type %d\n", mle->mnamelen, mle->mname,
         mle->type);

    /* remove from list if not already */
    __dlm_unlink_mle(dlm, mle);

    /* detach the mle from the domain node up/down events */
    __dlm_mle_detach_hb_events(dlm, mle);

    atomic_dec(&dlm->mle_cur_count[mle->type]);

    /* NOTE: kfree under spinlock here.
     * if this is bad, we can move this to a freelist. */
    kmem_cache_free(dlm_mle_cache, mle);
}


/*
 * LOCK RESOURCE FUNCTIONS
 */

int dlm_init_master_caches(void)
{
    dlm_lockres_cache = kmem_cache_create("o2dlm_lockres",
                          sizeof(struct dlm_lock_resource),
                          0, SLAB_HWCACHE_ALIGN, NULL);
    if (!dlm_lockres_cache)
        goto bail;

    dlm_lockname_cache = kmem_cache_create("o2dlm_lockname",
                           DLM_LOCKID_NAME_MAX, 0,
                           SLAB_HWCACHE_ALIGN, NULL);
    if (!dlm_lockname_cache)
        goto bail;

    return 0;
bail:
    dlm_destroy_master_caches();
    return -ENOMEM;
}

void dlm_destroy_master_caches(void)
{
    if (dlm_lockname_cache)
        kmem_cache_destroy(dlm_lockname_cache);

    if (dlm_lockres_cache)
        kmem_cache_destroy(dlm_lockres_cache);
}

static void dlm_lockres_release(struct kref *kref)
{
    struct dlm_lock_resource *res;
    struct dlm_ctxt *dlm;

    res = container_of(kref, struct dlm_lock_resource, refs);
    dlm = res->dlm;

    /* This should not happen -- all lockres' have a name
     * associated with them at init time. */
    BUG_ON(!res->lockname.name);

    mlog(0, "destroying lockres %.*s\n", res->lockname.len,
         res->lockname.name);

    spin_lock(&dlm->track_lock);
    if (!list_empty(&res->tracking))
        list_del_init(&res->tracking);
    else {
        mlog(ML_ERROR, "Resource %.*s not on the Tracking list\n",
             res->lockname.len, res->lockname.name);
        dlm_print_one_lock_resource(res);
    }
    spin_unlock(&dlm->track_lock);

    atomic_dec(&dlm->res_cur_count);

    if (!hlist_unhashed(&res->hash_node) ||
        !list_empty(&res->granted) ||
        !list_empty(&res->converting) ||
        !list_empty(&res->blocked) ||
        !list_empty(&res->dirty) ||
        !list_empty(&res->recovering) ||
        !list_empty(&res->purge)) {
        mlog(ML_ERROR,
             "Going to BUG for resource %.*s."
             "  We're on a list! [%c%c%c%c%c%c%c]\n",
             res->lockname.len, res->lockname.name,
             !hlist_unhashed(&res->hash_node) ? 'H' : ' ',
             !list_empty(&res->granted) ? 'G' : ' ',
             !list_empty(&res->converting) ? 'C' : ' ',
             !list_empty(&res->blocked) ? 'B' : ' ',
             !list_empty(&res->dirty) ? 'D' : ' ',
             !list_empty(&res->recovering) ? 'R' : ' ',
             !list_empty(&res->purge) ? 'P' : ' ');

        dlm_print_one_lock_resource(res);
    }

    /* By the time we're ready to blow this guy away, we shouldn't
     * be on any lists. */
    BUG_ON(!hlist_unhashed(&res->hash_node));
    BUG_ON(!list_empty(&res->granted));
    BUG_ON(!list_empty(&res->converting));
    BUG_ON(!list_empty(&res->blocked));
    BUG_ON(!list_empty(&res->dirty));
    BUG_ON(!list_empty(&res->recovering));
    BUG_ON(!list_empty(&res->purge));

    kmem_cache_free(dlm_lockname_cache, (void *)res->lockname.name);

    kmem_cache_free(dlm_lockres_cache, res);
}

void dlm_lockres_put(struct dlm_lock_resource *res)
{
    kref_put(&res->refs, dlm_lockres_release);
}

static void dlm_init_lockres(struct dlm_ctxt *dlm,
                 struct dlm_lock_resource *res,
                 const char *name, unsigned int namelen)
{
    char *qname;

    /* If we memset here, we lose our reference to the kmalloc'd
     * res->lockname.name, so be sure to init every field
     * correctly! */

    qname = (char *) res->lockname.name;
    memcpy(qname, name, namelen);

    res->lockname.len = namelen;
    res->lockname.hash = dlm_lockid_hash(name, namelen);

    init_waitqueue_head(&res->wq);
    spin_lock_init(&res->spinlock);
    INIT_HLIST_NODE(&res->hash_node);
    INIT_LIST_HEAD(&res->granted);
    INIT_LIST_HEAD(&res->converting);
    INIT_LIST_HEAD(&res->blocked);
    INIT_LIST_HEAD(&res->dirty);
    INIT_LIST_HEAD(&res->recovering);
    INIT_LIST_HEAD(&res->purge);
    INIT_LIST_HEAD(&res->tracking);
    atomic_set(&res->asts_reserved, 0);
    res->migration_pending = 0;
    res->inflight_locks = 0;

    res->dlm = dlm;

    kref_init(&res->refs);

    atomic_inc(&dlm->res_tot_count);
    atomic_inc(&dlm->res_cur_count);

    /* just for consistency */
    spin_lock(&res->spinlock);
    dlm_set_lockres_owner(dlm, res, DLM_LOCK_RES_OWNER_UNKNOWN);
    spin_unlock(&res->spinlock);

    res->state = DLM_LOCK_RES_IN_PROGRESS;

    res->last_used = 0;

    spin_lock(&dlm->spinlock);
    list_add_tail(&res->tracking, &dlm->tracking_list);
    spin_unlock(&dlm->spinlock);

    memset(res->lvb, 0, DLM_LVB_LEN);
    memset(res->refmap, 0, sizeof(res->refmap));
}

struct dlm_lock_resource *dlm_new_lockres(struct dlm_ctxt *dlm,
                   const char *name,
                   unsigned int namelen)
{
    struct dlm_lock_resource *res = NULL;

    res = kmem_cache_zalloc(dlm_lockres_cache, GFP_NOFS);
    if (!res)
        goto error;

    res->lockname.name = kmem_cache_zalloc(dlm_lockname_cache, GFP_NOFS);
    if (!res->lockname.name)
        goto error;

    dlm_init_lockres(dlm, res, name, namelen);
    return res;

error:
    if (res && res->lockname.name)
        kmem_cache_free(dlm_lockname_cache, (void *)res->lockname.name);

    if (res)
        kmem_cache_free(dlm_lockres_cache, res);
    return NULL;
}

void dlm_lockres_set_refmap_bit(struct dlm_ctxt *dlm,
                struct dlm_lock_resource *res, int bit)
{
    assert_spin_locked(&res->spinlock);

    mlog(0, "res %.*s, set node %u, %ps()\n", res->lockname.len,
         res->lockname.name, bit, __builtin_return_address(0));

    set_bit(bit, res->refmap);
}

void dlm_lockres_clear_refmap_bit(struct dlm_ctxt *dlm,
                  struct dlm_lock_resource *res, int bit)
{
    assert_spin_locked(&res->spinlock);

    mlog(0, "res %.*s, clr node %u, %ps()\n", res->lockname.len,
         res->lockname.name, bit, __builtin_return_address(0));

    clear_bit(bit, res->refmap);
}


void dlm_lockres_grab_inflight_ref(struct dlm_ctxt *dlm,
                   struct dlm_lock_resource *res)
{
    assert_spin_locked(&res->spinlock);

    res->inflight_locks++;

    mlog(0, "%s: res %.*s, inflight++: now %u, %ps()\n", dlm->name,
         res->lockname.len, res->lockname.name, res->inflight_locks,
         __builtin_return_address(0));
}

void dlm_lockres_drop_inflight_ref(struct dlm_ctxt *dlm,
                   struct dlm_lock_resource *res)
{
    assert_spin_locked(&res->spinlock);

    BUG_ON(res->inflight_locks == 0);

    res->inflight_locks--;

    mlog(0, "%s: res %.*s, inflight--: now %u, %ps()\n", dlm->name,
         res->lockname.len, res->lockname.name, res->inflight_locks,
         __builtin_return_address(0));

    wake_up(&res->wq);
}

/*
 * lookup a lock resource by name.
 * may already exist in the hashtable.
 * lockid is null terminated
 *
 * if not, allocate enough for the lockres and for
 * the temporary structure used in doing the mastering.
 *
 * also, do a lookup in the dlm->master_list to see
 * if another node has begun mastering the same lock.
 * if so, there should be a block entry in there
 * for this name, and we should *not* attempt to master
 * the lock here.   need to wait around for that node
 * to assert_master (or die).
 *
 */
struct dlm_lock_resource * dlm_get_lock_resource(struct dlm_ctxt *dlm,
                      const char *lockid,
                      int namelen,
                      int flags)
{
    struct dlm_lock_resource *tmpres=NULL, *res=NULL;
    struct dlm_master_list_entry *mle = NULL;
    struct dlm_master_list_entry *alloc_mle = NULL;
    int blocked = 0;
    int ret, nodenum;
    struct dlm_node_iter iter;
    unsigned int hash;
    int tries = 0;
    int bit, wait_on_recovery = 0;

    BUG_ON(!lockid);

    hash = dlm_lockid_hash(lockid, namelen);

    mlog(0, "get lockres %s (len %d)\n", lockid, namelen);

lookup:
    spin_lock(&dlm->spinlock);
    tmpres = __dlm_lookup_lockres_full(dlm, lockid, namelen, hash);
    if (tmpres) {
        spin_unlock(&dlm->spinlock);
        spin_lock(&tmpres->spinlock);
        /* Wait on the thread that is mastering the resource */
        if (tmpres->owner == DLM_LOCK_RES_OWNER_UNKNOWN) {
            __dlm_wait_on_lockres(tmpres);
            BUG_ON(tmpres->owner == DLM_LOCK_RES_OWNER_UNKNOWN);
            spin_unlock(&tmpres->spinlock);
            dlm_lockres_put(tmpres);
            tmpres = NULL;
            goto lookup;
        }

        /* Wait on the resource purge to complete before continuing */
        if (tmpres->state & DLM_LOCK_RES_DROPPING_REF) {
            BUG_ON(tmpres->owner == dlm->node_num);
            __dlm_wait_on_lockres_flags(tmpres,
                            DLM_LOCK_RES_DROPPING_REF);
            spin_unlock(&tmpres->spinlock);
            dlm_lockres_put(tmpres);
            tmpres = NULL;
            goto lookup;
        }

        /* Grab inflight ref to pin the resource */
        dlm_lockres_grab_inflight_ref(dlm, tmpres);

        spin_unlock(&tmpres->spinlock);
        if (res)
            dlm_lockres_put(res);
        res = tmpres;
        goto leave;
    }

    if (!res) {
        spin_unlock(&dlm->spinlock);
        mlog(0, "allocating a new resource\n");
        /* nothing found and we need to allocate one. */
        alloc_mle = kmem_cache_alloc(dlm_mle_cache, GFP_NOFS);
        if (!alloc_mle)
            goto leave;
        res = dlm_new_lockres(dlm, lockid, namelen);
        if (!res)
            goto leave;
        goto lookup;
    }

    mlog(0, "no lockres found, allocated our own: %p\n", res);

    if (flags & LKM_LOCAL) {
        /* caller knows it's safe to assume it's not mastered elsewhere
         * DONE!  return right away */
        spin_lock(&res->spinlock);
        dlm_change_lockres_owner(dlm, res, dlm->node_num);
        __dlm_insert_lockres(dlm, res);
        dlm_lockres_grab_inflight_ref(dlm, res);
        spin_unlock(&res->spinlock);
        spin_unlock(&dlm->spinlock);
        /* lockres still marked IN_PROGRESS */
        goto wake_waiters;
    }

    /* check master list to see if another node has started mastering it */
    spin_lock(&dlm->master_lock);

    /* if we found a block, wait for lock to be mastered by another node */
    blocked = dlm_find_mle(dlm, &mle, (char *)lockid, namelen);
    if (blocked) {
        int mig;
        if (mle->type == DLM_MLE_MASTER) {
            mlog(ML_ERROR, "master entry for nonexistent lock!\n");
            BUG();
        }
        mig = (mle->type == DLM_MLE_MIGRATION);
        /* if there is a migration in progress, let the migration
         * finish before continuing.  we can wait for the absence
         * of the MIGRATION mle: either the migrate finished or
         * one of the nodes died and the mle was cleaned up.
         * if there is a BLOCK here, but it already has a master
         * set, we are too late.  the master does not have a ref
         * for us in the refmap.  detach the mle and drop it.
         * either way, go back to the top and start over. */
        if (mig || mle->master != O2NM_MAX_NODES) {
            BUG_ON(mig && mle->master == dlm->node_num);
            /* we arrived too late.  the master does not
             * have a ref for us. retry. */
            mlog(0, "%s:%.*s: late on %s\n",
                 dlm->name, namelen, lockid,
                 mig ?  "MIGRATION" : "BLOCK");
            spin_unlock(&dlm->master_lock);
            spin_unlock(&dlm->spinlock);

            /* master is known, detach */
            if (!mig)
                dlm_mle_detach_hb_events(dlm, mle);
            dlm_put_mle(mle);
            mle = NULL;
            /* this is lame, but we can't wait on either
             * the mle or lockres waitqueue here */
            if (mig)
                msleep(100);
            goto lookup;
        }
    } else {
        /* go ahead and try to master lock on this node */
        mle = alloc_mle;
        /* make sure this does not get freed below */
        alloc_mle = NULL;
        dlm_init_mle(mle, DLM_MLE_MASTER, dlm, res, NULL, 0);
        set_bit(dlm->node_num, mle->maybe_map);
        __dlm_insert_mle(dlm, mle);

        /* still holding the dlm spinlock, check the recovery map
         * to see if there are any nodes that still need to be
         * considered.  these will not appear in the mle nodemap
         * but they might own this lockres.  wait on them. */
        bit = find_next_bit(dlm->recovery_map, O2NM_MAX_NODES, 0);
        if (bit < O2NM_MAX_NODES) {
            mlog(0, "%s: res %.*s, At least one node (%d) "
                 "to recover before lock mastery can begin\n",
                 dlm->name, namelen, (char *)lockid, bit);
            wait_on_recovery = 1;
        }
    }

    /* at this point there is either a DLM_MLE_BLOCK or a
     * DLM_MLE_MASTER on the master list, so it's safe to add the
     * lockres to the hashtable.  anyone who finds the lock will
     * still have to wait on the IN_PROGRESS. */

    /* finally add the lockres to its hash bucket */
    __dlm_insert_lockres(dlm, res);

    /* Grab inflight ref to pin the resource */
    spin_lock(&res->spinlock);
    dlm_lockres_grab_inflight_ref(dlm, res);
    spin_unlock(&res->spinlock);

    /* get an extra ref on the mle in case this is a BLOCK
     * if so, the creator of the BLOCK may try to put the last
     * ref at this time in the assert master handler, so we
     * need an extra one to keep from a bad ptr deref. */
    dlm_get_mle_inuse(mle);
    spin_unlock(&dlm->master_lock);
    spin_unlock(&dlm->spinlock);

redo_request:
    while (wait_on_recovery) {
        /* any cluster changes that occurred after dropping the
         * dlm spinlock would be detectable be a change on the mle,
         * so we only need to clear out the recovery map once. */
        if (dlm_is_recovery_lock(lockid, namelen)) {
            mlog(0, "%s: Recovery map is not empty, but must "
                 "master $RECOVERY lock now\n", dlm->name);
            if (!dlm_pre_master_reco_lockres(dlm, res))
                wait_on_recovery = 0;
            else {
                mlog(0, "%s: waiting 500ms for heartbeat state "
                    "change\n", dlm->name);
                msleep(500);
            }
            continue;
        }

        dlm_kick_recovery_thread(dlm);
        msleep(1000);
        dlm_wait_for_recovery(dlm);

        spin_lock(&dlm->spinlock);
        bit = find_next_bit(dlm->recovery_map, O2NM_MAX_NODES, 0);
        if (bit < O2NM_MAX_NODES) {
            mlog(0, "%s: res %.*s, At least one node (%d) "
                 "to recover before lock mastery can begin\n",
                 dlm->name, namelen, (char *)lockid, bit);
            wait_on_recovery = 1;
        } else
            wait_on_recovery = 0;
        spin_unlock(&dlm->spinlock);

        if (wait_on_recovery)
            dlm_wait_for_node_recovery(dlm, bit, 10000);
    }

    /* must wait for lock to be mastered elsewhere */
    if (blocked)
        goto wait;

    ret = -EINVAL;
    dlm_node_iter_init(mle->vote_map, &iter);
    while ((nodenum = dlm_node_iter_next(&iter)) >= 0) {
        ret = dlm_do_master_request(res, mle, nodenum);
        if (ret < 0)
            mlog_errno(ret);
        if (mle->master != O2NM_MAX_NODES) {
            /* found a master ! */
            if (mle->master <= nodenum)
                break;
            /* if our master request has not reached the master
             * yet, keep going until it does.  this is how the
             * master will know that asserts are needed back to
             * the lower nodes. */
            mlog(0, "%s: res %.*s, Requests only up to %u but "
                 "master is %u, keep going\n", dlm->name, namelen,
                 lockid, nodenum, mle->master);
        }
    }

wait:
    /* keep going until the response map includes all nodes */
    ret = dlm_wait_for_lock_mastery(dlm, res, mle, &blocked);
    if (ret < 0) {
        wait_on_recovery = 1;
        mlog(0, "%s: res %.*s, Node map changed, redo the master "
             "request now, blocked=%d\n", dlm->name, res->lockname.len,
             res->lockname.name, blocked);
        if (++tries > 20) {
            mlog(ML_ERROR, "%s: res %.*s, Spinning on "
                 "dlm_wait_for_lock_mastery, blocked = %d\n",
                 dlm->name, res->lockname.len,
                 res->lockname.name, blocked);
            dlm_print_one_lock_resource(res);
            dlm_print_one_mle(mle);
            tries = 0;
        }
        goto redo_request;
    }

    mlog(0, "%s: res %.*s, Mastered by %u\n", dlm->name, res->lockname.len,
         res->lockname.name, res->owner);
    /* make sure we never continue without this */
    BUG_ON(res->owner == O2NM_MAX_NODES);

    /* master is known, detach if not already detached */
    dlm_mle_detach_hb_events(dlm, mle);
    dlm_put_mle(mle);
    /* put the extra ref */
    dlm_put_mle_inuse(mle);

wake_waiters:
    spin_lock(&res->spinlock);
    res->state &= ~DLM_LOCK_RES_IN_PROGRESS;
    spin_unlock(&res->spinlock);
    wake_up(&res->wq);

leave:
    /* need to free the unused mle */
    if (alloc_mle)
        kmem_cache_free(dlm_mle_cache, alloc_mle);

    return res;
}


#define DLM_MASTERY_TIMEOUT_MS   5000

static int dlm_wait_for_lock_mastery(struct dlm_ctxt *dlm,
                     struct dlm_lock_resource *res,
                     struct dlm_master_list_entry *mle,
                     int *blocked)
{
    u8 m;
    int ret, bit;
    int map_changed, voting_done;
    int assert, sleep;

recheck:
    ret = 0;
    assert = 0;

    /* check if another node has already become the owner */
    spin_lock(&res->spinlock);
    if (res->owner != DLM_LOCK_RES_OWNER_UNKNOWN) {
        mlog(0, "%s:%.*s: owner is suddenly %u\n", dlm->name,
             res->lockname.len, res->lockname.name, res->owner);
        spin_unlock(&res->spinlock);
        /* this will cause the master to re-assert across
         * the whole cluster, freeing up mles */
        if (res->owner != dlm->node_num) {
            ret = dlm_do_master_request(res, mle, res->owner);
            if (ret < 0) {
                /* give recovery a chance to run */
                mlog(ML_ERROR, "link to %u went down?: %d\n", res->owner, ret);
                msleep(500);
                goto recheck;
            }
        }
        ret = 0;
        goto leave;
    }
    spin_unlock(&res->spinlock);

    spin_lock(&mle->spinlock);
    m = mle->master;
    map_changed = (memcmp(mle->vote_map, mle->node_map,
                  sizeof(mle->vote_map)) != 0);
    voting_done = (memcmp(mle->vote_map, mle->response_map,
                 sizeof(mle->vote_map)) == 0);

    /* restart if we hit any errors */
    if (map_changed) {
        int b;
        mlog(0, "%s: %.*s: node map changed, restarting\n",
             dlm->name, res->lockname.len, res->lockname.name);
        ret = dlm_restart_lock_mastery(dlm, res, mle, *blocked);
        b = (mle->type == DLM_MLE_BLOCK);
        if ((*blocked && !b) || (!*blocked && b)) {
            mlog(0, "%s:%.*s: status change: old=%d new=%d\n",
                 dlm->name, res->lockname.len, res->lockname.name,
                 *blocked, b);
            *blocked = b;
        }
        spin_unlock(&mle->spinlock);
        if (ret < 0) {
            mlog_errno(ret);
            goto leave;
        }
        mlog(0, "%s:%.*s: restart lock mastery succeeded, "
             "rechecking now\n", dlm->name, res->lockname.len,
             res->lockname.name);
        goto recheck;
    } else {
        if (!voting_done) {
            mlog(0, "map not changed and voting not done "
                 "for %s:%.*s\n", dlm->name, res->lockname.len,
                 res->lockname.name);
        }
    }

    if (m != O2NM_MAX_NODES) {
        /* another node has done an assert!
         * all done! */
        sleep = 0;
    } else {
        sleep = 1;
        /* have all nodes responded? */
        if (voting_done && !*blocked) {
            bit = find_next_bit(mle->maybe_map, O2NM_MAX_NODES, 0);
            if (dlm->node_num <= bit) {
                /* my node number is lowest.
                 * now tell other nodes that I am
                 * mastering this. */
                mle->master = dlm->node_num;
                /* ref was grabbed in get_lock_resource
                 * will be dropped in dlmlock_master */
                assert = 1;
                sleep = 0;
            }
            /* if voting is done, but we have not received
             * an assert master yet, we must sleep */
        }
    }

    spin_unlock(&mle->spinlock);

    /* sleep if we haven't finished voting yet */
    if (sleep) {
        unsigned long timeo = msecs_to_jiffies(DLM_MASTERY_TIMEOUT_MS);

        /*
        if (atomic_read(&mle->mle_refs.refcount) < 2)
            mlog(ML_ERROR, "mle (%p) refs=%d, name=%.*s\n", mle,
            atomic_read(&mle->mle_refs.refcount),
            res->lockname.len, res->lockname.name);
        */
        atomic_set(&mle->woken, 0);
        (void)wait_event_timeout(mle->wq,
                     (atomic_read(&mle->woken) == 1),
                     timeo);
        if (res->owner == O2NM_MAX_NODES) {
            mlog(0, "%s:%.*s: waiting again\n", dlm->name,
                 res->lockname.len, res->lockname.name);
            goto recheck;
        }
        mlog(0, "done waiting, master is %u\n", res->owner);
        ret = 0;
        goto leave;
    }

    ret = 0;   /* done */
    if (assert) {
        m = dlm->node_num;
        mlog(0, "about to master %.*s here, this=%u\n",
             res->lockname.len, res->lockname.name, m);
        ret = dlm_do_assert_master(dlm, res, mle->vote_map, 0);
        if (ret) {
            /* This is a failure in the network path,
             * not in the response to the assert_master
             * (any nonzero response is a BUG on this node).
             * Most likely a socket just got disconnected
             * due to node death. */
            mlog_errno(ret);
        }
        /* no longer need to restart lock mastery.
         * all living nodes have been contacted. */
        ret = 0;
    }

    /* set the lockres owner */
    spin_lock(&res->spinlock);
    /* mastery reference obtained either during
     * assert_master_handler or in get_lock_resource */
    dlm_change_lockres_owner(dlm, res, m);
    spin_unlock(&res->spinlock);

leave:
    return ret;
}

struct dlm_bitmap_diff_iter
{
    int curnode;
    unsigned long *orig_bm;
    unsigned long *cur_bm;
    unsigned long diff_bm[BITS_TO_LONGS(O2NM_MAX_NODES)];
};

enum dlm_node_state_change
{
    NODE_DOWN = -1,
    NODE_NO_CHANGE = 0,
    NODE_UP
};

static void dlm_bitmap_diff_iter_init(struct dlm_bitmap_diff_iter *iter,
                      unsigned long *orig_bm,
                      unsigned long *cur_bm)
{
    unsigned long p1, p2;
    int i;

    iter->curnode = -1;
    iter->orig_bm = orig_bm;
    iter->cur_bm = cur_bm;

    for (i = 0; i < BITS_TO_LONGS(O2NM_MAX_NODES); i++) {
            p1 = *(iter->orig_bm + i);
            p2 = *(iter->cur_bm + i);
        iter->diff_bm[i] = (p1 & ~p2) | (p2 & ~p1);
    }
}

static int dlm_bitmap_diff_iter_next(struct dlm_bitmap_diff_iter *iter,
                     enum dlm_node_state_change *state)
{
    int bit;

    if (iter->curnode >= O2NM_MAX_NODES)
        return -ENOENT;

    bit = find_next_bit(iter->diff_bm, O2NM_MAX_NODES,
                iter->curnode+1);
    if (bit >= O2NM_MAX_NODES) {
        iter->curnode = O2NM_MAX_NODES;
        return -ENOENT;
    }

    /* if it was there in the original then this node died */
    if (test_bit(bit, iter->orig_bm))
        *state = NODE_DOWN;
    else
        *state = NODE_UP;

    iter->curnode = bit;
    return bit;
}


static int dlm_restart_lock_mastery(struct dlm_ctxt *dlm,
                    struct dlm_lock_resource *res,
                    struct dlm_master_list_entry *mle,
                    int blocked)
{
    struct dlm_bitmap_diff_iter bdi;
    enum dlm_node_state_change sc;
    int node;
    int ret = 0;

    mlog(0, "something happened such that the "
         "master process may need to be restarted!\n");

    assert_spin_locked(&mle->spinlock);

    dlm_bitmap_diff_iter_init(&bdi, mle->vote_map, mle->node_map);
    node = dlm_bitmap_diff_iter_next(&bdi, &sc);
    while (node >= 0) {
        if (sc == NODE_UP) {
            /* a node came up.  clear any old vote from
             * the response map and set it in the vote map
             * then restart the mastery. */
            mlog(ML_NOTICE, "node %d up while restarting\n", node);

            /* redo the master request, but only for the new node */
            mlog(0, "sending request to new node\n");
            clear_bit(node, mle->response_map);
            set_bit(node, mle->vote_map);
        } else {
            mlog(ML_ERROR, "node down! %d\n", node);
            if (blocked) {
                int lowest = find_next_bit(mle->maybe_map,
                               O2NM_MAX_NODES, 0);

                /* act like it was never there */
                clear_bit(node, mle->maybe_map);

                    if (node == lowest) {
                    mlog(0, "expected master %u died"
                        " while this node was blocked "
                        "waiting on it!\n", node);
                    lowest = find_next_bit(mle->maybe_map,
                                O2NM_MAX_NODES,
                                lowest+1);
                    if (lowest < O2NM_MAX_NODES) {
                        mlog(0, "%s:%.*s:still "
                             "blocked. waiting on %u "
                             "now\n", dlm->name,
                             res->lockname.len,
                             res->lockname.name,
                             lowest);
                    } else {
                        /* mle is an MLE_BLOCK, but
                         * there is now nothing left to
                         * block on.  we need to return
                         * all the way back out and try
                         * again with an MLE_MASTER.
                         * dlm_do_local_recovery_cleanup
                         * has already run, so the mle
                         * refcount is ok */
                        mlog(0, "%s:%.*s: no "
                             "longer blocking. try to "
                             "master this here\n",
                             dlm->name,
                             res->lockname.len,
                             res->lockname.name);
                        mle->type = DLM_MLE_MASTER;
                        mle->mleres = res;
                    }
                }
            }

            /* now blank out everything, as if we had never
             * contacted anyone */
            memset(mle->maybe_map, 0, sizeof(mle->maybe_map));
            memset(mle->response_map, 0, sizeof(mle->response_map));
            /* reset the vote_map to the current node_map */
            memcpy(mle->vote_map, mle->node_map,
                   sizeof(mle->node_map));
            /* put myself into the maybe map */
            if (mle->type != DLM_MLE_BLOCK)
                set_bit(dlm->node_num, mle->maybe_map);
        }
        ret = -EAGAIN;
        node = dlm_bitmap_diff_iter_next(&bdi, &sc);
    }
    return ret;
}


/*
 * DLM_MASTER_REQUEST_MSG
 *
 * returns: 0 on success,
 *          -errno on a network error
 *
 * on error, the caller should assume the target node is "dead"
 *
 */

static int dlm_do_master_request(struct dlm_lock_resource *res,
                 struct dlm_master_list_entry *mle, int to)
{
    struct dlm_ctxt *dlm = mle->dlm;
    struct dlm_master_request request;
    int ret, response=0, resend;

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

    BUG_ON(mle->type == DLM_MLE_MIGRATION);

    request.namelen = (u8)mle->mnamelen;
    memcpy(request.name, mle->mname, request.namelen);

again:
    ret = o2net_send_message(DLM_MASTER_REQUEST_MSG, dlm->key, &request,
                 sizeof(request), to, &response);
    if (ret < 0)  {
        if (ret == -ESRCH) {
            /* should never happen */
            mlog(ML_ERROR, "TCP stack not ready!\n");
            BUG();
        } else if (ret == -EINVAL) {
            mlog(ML_ERROR, "bad args passed to o2net!\n");
            BUG();
        } else if (ret == -ENOMEM) {
            mlog(ML_ERROR, "out of memory while trying to send "
                 "network message!  retrying\n");
            /* this is totally crude */
            msleep(50);
            goto again;
        } else if (!dlm_is_host_down(ret)) {
            /* not a network error. bad. */
            mlog_errno(ret);
            mlog(ML_ERROR, "unhandled error!");
            BUG();
        }
        /* all other errors should be network errors,
         * and likely indicate node death */
        mlog(ML_ERROR, "link to %d went down!\n", to);
        goto out;
    }

    ret = 0;
    resend = 0;
    spin_lock(&mle->spinlock);
    switch (response) {
        case DLM_MASTER_RESP_YES:
            set_bit(to, mle->response_map);
            mlog(0, "node %u is the master, response=YES\n", to);
            mlog(0, "%s:%.*s: master node %u now knows I have a "
                 "reference\n", dlm->name, res->lockname.len,
                 res->lockname.name, to);
            mle->master = to;
            break;
        case DLM_MASTER_RESP_NO:
            mlog(0, "node %u not master, response=NO\n", to);
            set_bit(to, mle->response_map);
            break;
        case DLM_MASTER_RESP_MAYBE:
            mlog(0, "node %u not master, response=MAYBE\n", to);
            set_bit(to, mle->response_map);
            set_bit(to, mle->maybe_map);
            break;
        case DLM_MASTER_RESP_ERROR:
            mlog(0, "node %u hit an error, resending\n", to);
            resend = 1;
            response = 0;
            break;
        default:
            mlog(ML_ERROR, "bad response! %u\n", response);
            BUG();
    }
    spin_unlock(&mle->spinlock);
    if (resend) {
        /* this is also totally crude */
        msleep(50);
        goto again;
    }

out:
    return ret;
}

/*
 * locks that can be taken here:
 * dlm->spinlock
 * res->spinlock
 * mle->spinlock
 * dlm->master_list
 *
 * if possible, TRIM THIS DOWN!!!
 */
int dlm_master_request_handler(struct o2net_msg *msg, u32 len, void *data,
                   void **ret_data)
{
    u8 response = DLM_MASTER_RESP_MAYBE;
    struct dlm_ctxt *dlm = data;
    struct dlm_lock_resource *res = NULL;
    struct dlm_master_request *request = (struct dlm_master_request *) msg->buf;
    struct dlm_master_list_entry *mle = NULL, *tmpmle = NULL;
    char *name;
    unsigned int namelen, hash;
    int found, ret;
    int set_maybe;
    int dispatch_assert = 0;

    if (!dlm_grab(dlm))
        return DLM_MASTER_RESP_NO;

    if (!dlm_domain_fully_joined(dlm)) {
        response = DLM_MASTER_RESP_NO;
        goto send_response;
    }

    name = request->name;
    namelen = request->namelen;
    hash = dlm_lockid_hash(name, namelen);

    if (namelen > DLM_LOCKID_NAME_MAX) {
        response = DLM_IVBUFLEN;
        goto send_response;
    }

way_up_top:
    spin_lock(&dlm->spinlock);
    res = __dlm_lookup_lockres(dlm, name, namelen, hash);
    if (res) {
        spin_unlock(&dlm->spinlock);

        /* take care of the easy cases up front */
        spin_lock(&res->spinlock);
        if (res->state & (DLM_LOCK_RES_RECOVERING|
                  DLM_LOCK_RES_MIGRATING)) {
            spin_unlock(&res->spinlock);
            mlog(0, "returning DLM_MASTER_RESP_ERROR since res is "
                 "being recovered/migrated\n");
            response = DLM_MASTER_RESP_ERROR;
            if (mle)
                kmem_cache_free(dlm_mle_cache, mle);
            goto send_response;
        }

        if (res->owner == dlm->node_num) {
            dlm_lockres_set_refmap_bit(dlm, res, request->node_idx);
            spin_unlock(&res->spinlock);
            response = DLM_MASTER_RESP_YES;
            if (mle)
                kmem_cache_free(dlm_mle_cache, mle);

            /* this node is the owner.
             * there is some extra work that needs to
             * happen now.  the requesting node has
             * caused all nodes up to this one to
             * create mles.  this node now needs to
             * go back and clean those up. */
            dispatch_assert = 1;
            goto send_response;
        } else if (res->owner != DLM_LOCK_RES_OWNER_UNKNOWN) {
            spin_unlock(&res->spinlock);
            // mlog(0, "node %u is the master\n", res->owner);
            response = DLM_MASTER_RESP_NO;
            if (mle)
                kmem_cache_free(dlm_mle_cache, mle);
            goto send_response;
        }

        /* ok, there is no owner.  either this node is
         * being blocked, or it is actively trying to
         * master this lock. */
        if (!(res->state & DLM_LOCK_RES_IN_PROGRESS)) {
            mlog(ML_ERROR, "lock with no owner should be "
                 "in-progress!\n");
            BUG();
        }

        // mlog(0, "lockres is in progress...\n");
        spin_lock(&dlm->master_lock);
        found = dlm_find_mle(dlm, &tmpmle, name, namelen);
        if (!found) {
            mlog(ML_ERROR, "no mle found for this lock!\n");
            BUG();
        }
        set_maybe = 1;
        spin_lock(&tmpmle->spinlock);
        if (tmpmle->type == DLM_MLE_BLOCK) {
            // mlog(0, "this node is waiting for "
            // "lockres to be mastered\n");
            response = DLM_MASTER_RESP_NO;
        } else if (tmpmle->type == DLM_MLE_MIGRATION) {
            mlog(0, "node %u is master, but trying to migrate to "
                 "node %u.\n", tmpmle->master, tmpmle->new_master);
            if (tmpmle->master == dlm->node_num) {
                mlog(ML_ERROR, "no owner on lockres, but this "
                     "node is trying to migrate it to %u?!\n",
                     tmpmle->new_master);
                BUG();
            } else {
                /* the real master can respond on its own */
                response = DLM_MASTER_RESP_NO;
            }
        } else if (tmpmle->master != DLM_LOCK_RES_OWNER_UNKNOWN) {
            set_maybe = 0;
            if (tmpmle->master == dlm->node_num) {
                response = DLM_MASTER_RESP_YES;
                /* this node will be the owner.
                 * go back and clean the mles on any
                 * other nodes */
                dispatch_assert = 1;
                dlm_lockres_set_refmap_bit(dlm, res,
                               request->node_idx);
            } else
                response = DLM_MASTER_RESP_NO;
        } else {
            // mlog(0, "this node is attempting to "
            // "master lockres\n");
            response = DLM_MASTER_RESP_MAYBE;
        }
        if (set_maybe)
            set_bit(request->node_idx, tmpmle->maybe_map);
        spin_unlock(&tmpmle->spinlock);

        spin_unlock(&dlm->master_lock);
        spin_unlock(&res->spinlock);

        /* keep the mle attached to heartbeat events */
        dlm_put_mle(tmpmle);
        if (mle)
            kmem_cache_free(dlm_mle_cache, mle);
        goto send_response;
    }

    /*
     * lockres doesn't exist on this node
     * if there is an MLE_BLOCK, return NO
     * if there is an MLE_MASTER, return MAYBE
     * otherwise, add an MLE_BLOCK, return NO
     */
    spin_lock(&dlm->master_lock);
    found = dlm_find_mle(dlm, &tmpmle, name, namelen);
    if (!found) {
        /* this lockid has never been seen on this node yet */
        // mlog(0, "no mle found\n");
        if (!mle) {
            spin_unlock(&dlm->master_lock);
            spin_unlock(&dlm->spinlock);

            mle = kmem_cache_alloc(dlm_mle_cache, GFP_NOFS);
            if (!mle) {
                response = DLM_MASTER_RESP_ERROR;
                mlog_errno(-ENOMEM);
                goto send_response;
            }
            goto way_up_top;
        }

        // mlog(0, "this is second time thru, already allocated, "
        // "add the block.\n");
        dlm_init_mle(mle, DLM_MLE_BLOCK, dlm, NULL, name, namelen);
        set_bit(request->node_idx, mle->maybe_map);
        __dlm_insert_mle(dlm, mle);
        response = DLM_MASTER_RESP_NO;
    } else {
        // mlog(0, "mle was found\n");
        set_maybe = 1;
        spin_lock(&tmpmle->spinlock);
        if (tmpmle->master == dlm->node_num) {
            mlog(ML_ERROR, "no lockres, but an mle with this node as master!\n");
            BUG();
        }
        if (tmpmle->type == DLM_MLE_BLOCK)
            response = DLM_MASTER_RESP_NO;
        else if (tmpmle->type == DLM_MLE_MIGRATION) {
            mlog(0, "migration mle was found (%u->%u)\n",
                 tmpmle->master, tmpmle->new_master);
            /* real master can respond on its own */
            response = DLM_MASTER_RESP_NO;
        } else
            response = DLM_MASTER_RESP_MAYBE;
        if (set_maybe)
            set_bit(request->node_idx, tmpmle->maybe_map);
        spin_unlock(&tmpmle->spinlock);
    }
    spin_unlock(&dlm->master_lock);
    spin_unlock(&dlm->spinlock);

    if (found) {
        /* keep the mle attached to heartbeat events */
        dlm_put_mle(tmpmle);
    }
send_response:
    /*
     * __dlm_lookup_lockres() grabbed a reference to this lockres.
     * The reference is released by dlm_assert_master_worker() under
     * the call to dlm_dispatch_assert_master().  If
     * dlm_assert_master_worker() isn't called, we drop it here.
     */
    if (dispatch_assert) {
        if (response != DLM_MASTER_RESP_YES)
            mlog(ML_ERROR, "invalid response %d\n", response);
        if (!res) {
            mlog(ML_ERROR, "bad lockres while trying to assert!\n");
            BUG();
        }
        mlog(0, "%u is the owner of %.*s, cleaning everyone else\n",
                 dlm->node_num, res->lockname.len, res->lockname.name);
        ret = dlm_dispatch_assert_master(dlm, res, 0, request->node_idx,
                         DLM_ASSERT_MASTER_MLE_CLEANUP);
        if (ret < 0) {
            mlog(ML_ERROR, "failed to dispatch assert master work\n");
            response = DLM_MASTER_RESP_ERROR;
            dlm_lockres_put(res);
        }
    } else {
        if (res)
            dlm_lockres_put(res);
    }

    dlm_put(dlm);
    return response;
}

/*
 * DLM_ASSERT_MASTER_MSG
 */


/*
 * NOTE: this can be used for debugging
 * can periodically run all locks owned by this node
 * and re-assert across the cluster...
 */
static int dlm_do_assert_master(struct dlm_ctxt *dlm,
                struct dlm_lock_resource *res,
                void *nodemap, u32 flags)
{
    struct dlm_assert_master assert;
    int to, tmpret;
    struct dlm_node_iter iter;
    int ret = 0;
    int reassert;
    const char *lockname = res->lockname.name;
    unsigned int namelen = res->lockname.len;

    BUG_ON(namelen > O2NM_MAX_NAME_LEN);

    spin_lock(&res->spinlock);
    res->state |= DLM_LOCK_RES_SETREF_INPROG;
    spin_unlock(&res->spinlock);

again:
    reassert = 0;

    /* note that if this nodemap is empty, it returns 0 */
    dlm_node_iter_init(nodemap, &iter);
    while ((to = dlm_node_iter_next(&iter)) >= 0) {
        int r = 0;
        struct dlm_master_list_entry *mle = NULL;

        mlog(0, "sending assert master to %d (%.*s)\n", to,
             namelen, lockname);
        memset(&assert, 0, sizeof(assert));
        assert.node_idx = dlm->node_num;
        assert.namelen = namelen;
        memcpy(assert.name, lockname, namelen);
        assert.flags = cpu_to_be32(flags);

        tmpret = o2net_send_message(DLM_ASSERT_MASTER_MSG, dlm->key,
                        &assert, sizeof(assert), to, &r);
        if (tmpret < 0) {
            mlog(ML_ERROR, "Error %d when sending message %u (key "
                 "0x%x) to node %u\n", tmpret,
                 DLM_ASSERT_MASTER_MSG, dlm->key, to);
            if (!dlm_is_host_down(tmpret)) {
                mlog(ML_ERROR, "unhandled error=%d!\n", tmpret);
                BUG();
            }
            /* a node died.  finish out the rest of the nodes. */
            mlog(0, "link to %d went down!\n", to);
            /* any nonzero status return will do */
            ret = tmpret;
            r = 0;
        } else if (r < 0) {
            /* ok, something horribly messed.  kill thyself. */
            mlog(ML_ERROR,"during assert master of %.*s to %u, "
                 "got %d.\n", namelen, lockname, to, r);
            spin_lock(&dlm->spinlock);
            spin_lock(&dlm->master_lock);
            if (dlm_find_mle(dlm, &mle, (char *)lockname,
                     namelen)) {
                dlm_print_one_mle(mle);
                __dlm_put_mle(mle);
            }
            spin_unlock(&dlm->master_lock);
            spin_unlock(&dlm->spinlock);
            BUG();
        }

        if (r & DLM_ASSERT_RESPONSE_REASSERT &&
            !(r & DLM_ASSERT_RESPONSE_MASTERY_REF)) {
                mlog(ML_ERROR, "%.*s: very strange, "
                     "master MLE but no lockres on %u\n",
                     namelen, lockname, to);
        }

        if (r & DLM_ASSERT_RESPONSE_REASSERT) {
            mlog(0, "%.*s: node %u create mles on other "
                 "nodes and requests a re-assert\n",
                 namelen, lockname, to);
            reassert = 1;
        }
        if (r & DLM_ASSERT_RESPONSE_MASTERY_REF) {
            mlog(0, "%.*s: node %u has a reference to this "
                 "lockres, set the bit in the refmap\n",
                 namelen, lockname, to);
            spin_lock(&res->spinlock);
            dlm_lockres_set_refmap_bit(dlm, res, to);
            spin_unlock(&res->spinlock);
        }
    }

    if (reassert)
        goto again;

    spin_lock(&res->spinlock);
    res->state &= ~DLM_LOCK_RES_SETREF_INPROG;
    spin_unlock(&res->spinlock);
    wake_up(&res->wq);

    return ret;
}

/*
 * locks that can be taken here:
 * dlm->spinlock
 * res->spinlock
 * mle->spinlock
 * dlm->master_list
 *
 * if possible, TRIM THIS DOWN!!!
 */
int dlm_assert_master_handler(struct o2net_msg *msg, u32 len, void *data,
                  void **ret_data)
{
    struct dlm_ctxt *dlm = data;
    struct dlm_master_list_entry *mle = NULL;
    struct dlm_assert_master *assert = (struct dlm_assert_master *)msg->buf;
    struct dlm_lock_resource *res = NULL;
    char *name;
    unsigned int namelen, hash;
    u32 flags;
    int master_request = 0, have_lockres_ref = 0;
    int ret = 0;

    if (!dlm_grab(dlm))
        return 0;

    name = assert->name;
    namelen = assert->namelen;
    hash = dlm_lockid_hash(name, namelen);
    flags = be32_to_cpu(assert->flags);

    if (namelen > DLM_LOCKID_NAME_MAX) {
        mlog(ML_ERROR, "Invalid name length!");
        goto done;
    }

    spin_lock(&dlm->spinlock);

    if (flags)
        mlog(0, "assert_master with flags: %u\n", flags);

    /* find the MLE */
    spin_lock(&dlm->master_lock);
    if (!dlm_find_mle(dlm, &mle, name, namelen)) {
        /* not an error, could be master just re-asserting */
        mlog(0, "just got an assert_master from %u, but no "
             "MLE for it! (%.*s)\n", assert->node_idx,
             namelen, name);
    } else {
        int bit = find_next_bit (mle->maybe_map, O2NM_MAX_NODES, 0);
        if (bit >= O2NM_MAX_NODES) {
            /* not necessarily an error, though less likely.
             * could be master just re-asserting. */
            mlog(0, "no bits set in the maybe_map, but %u "
                 "is asserting! (%.*s)\n", assert->node_idx,
                 namelen, name);
        } else if (bit != assert->node_idx) {
            if (flags & DLM_ASSERT_MASTER_MLE_CLEANUP) {
                mlog(0, "master %u was found, %u should "
                     "back off\n", assert->node_idx, bit);
            } else {
                /* with the fix for bug 569, a higher node
                 * number winning the mastery will respond
                 * YES to mastery requests, but this node
                 * had no way of knowing.  let it pass. */
                mlog(0, "%u is the lowest node, "
                     "%u is asserting. (%.*s)  %u must "
                     "have begun after %u won.\n", bit,
                     assert->node_idx, namelen, name, bit,
                     assert->node_idx);
            }
        }
        if (mle->type == DLM_MLE_MIGRATION) {
            if (flags & DLM_ASSERT_MASTER_MLE_CLEANUP) {
                mlog(0, "%s:%.*s: got cleanup assert"
                     " from %u for migration\n",
                     dlm->name, namelen, name,
                     assert->node_idx);
            } else if (!(flags & DLM_ASSERT_MASTER_FINISH_MIGRATION)) {
                mlog(0, "%s:%.*s: got unrelated assert"
                     " from %u for migration, ignoring\n",
                     dlm->name, namelen, name,
                     assert->node_idx);
                __dlm_put_mle(mle);
                spin_unlock(&dlm->master_lock);
                spin_unlock(&dlm->spinlock);
                goto done;
            }
        }
    }
    spin_unlock(&dlm->master_lock);

    /* ok everything checks out with the MLE
     * now check to see if there is a lockres */
    res = __dlm_lookup_lockres(dlm, name, namelen, hash);
    if (res) {
        spin_lock(&res->spinlock);
        if (res->state & DLM_LOCK_RES_RECOVERING)  {
            mlog(ML_ERROR, "%u asserting but %.*s is "
                 "RECOVERING!\n", assert->node_idx, namelen, name);
            goto kill;
        }
        if (!mle) {
            if (res->owner != DLM_LOCK_RES_OWNER_UNKNOWN &&
                res->owner != assert->node_idx) {
                mlog(ML_ERROR, "DIE! Mastery assert from %u, "
                     "but current owner is %u! (%.*s)\n",
                     assert->node_idx, res->owner, namelen,
                     name);
                __dlm_print_one_lock_resource(res);
                BUG();
            }
        } else if (mle->type != DLM_MLE_MIGRATION) {
            if (res->owner != DLM_LOCK_RES_OWNER_UNKNOWN) {
                /* owner is just re-asserting */
                if (res->owner == assert->node_idx) {
                    mlog(0, "owner %u re-asserting on "
                         "lock %.*s\n", assert->node_idx,
                         namelen, name);
                    goto ok;
                }
                mlog(ML_ERROR, "got assert_master from "
                     "node %u, but %u is the owner! "
                     "(%.*s)\n", assert->node_idx,
                     res->owner, namelen, name);
                goto kill;
            }
            if (!(res->state & DLM_LOCK_RES_IN_PROGRESS)) {
                mlog(ML_ERROR, "got assert from %u, but lock "
                     "with no owner should be "
                     "in-progress! (%.*s)\n",
                     assert->node_idx,
                     namelen, name);
                goto kill;
            }
        } else /* mle->type == DLM_MLE_MIGRATION */ {
            /* should only be getting an assert from new master */
            if (assert->node_idx != mle->new_master) {
                mlog(ML_ERROR, "got assert from %u, but "
                     "new master is %u, and old master "
                     "was %u (%.*s)\n",
                     assert->node_idx, mle->new_master,
                     mle->master, namelen, name);
                goto kill;
            }

        }
ok:
        spin_unlock(&res->spinlock);
    }

    // mlog(0, "woo!  got an assert_master from node %u!\n",
    //       assert->node_idx);
    if (mle) {
        int extra_ref = 0;
        int nn = -1;
        int rr, err = 0;

        spin_lock(&mle->spinlock);
        if (mle->type == DLM_MLE_BLOCK || mle->type == DLM_MLE_MIGRATION)
            extra_ref = 1;
        else {
            /* MASTER mle: if any bits set in the response map
             * then the calling node needs to re-assert to clear
             * up nodes that this node contacted */
            while ((nn = find_next_bit (mle->response_map, O2NM_MAX_NODES,
                            nn+1)) < O2NM_MAX_NODES) {
                if (nn != dlm->node_num && nn != assert->node_idx)
                    master_request = 1;
            }
        }
        mle->master = assert->node_idx;
        atomic_set(&mle->woken, 1);
        wake_up(&mle->wq);
        spin_unlock(&mle->spinlock);

        if (res) {
            int wake = 0;
            spin_lock(&res->spinlock);
            if (mle->type == DLM_MLE_MIGRATION) {
                mlog(0, "finishing off migration of lockres %.*s, "
                        "from %u to %u\n",
                        res->lockname.len, res->lockname.name,
                        dlm->node_num, mle->new_master);
                res->state &= ~DLM_LOCK_RES_MIGRATING;
                wake = 1;
                dlm_change_lockres_owner(dlm, res, mle->new_master);
                BUG_ON(res->state & DLM_LOCK_RES_DIRTY);
            } else {
                dlm_change_lockres_owner(dlm, res, mle->master);
            }
            spin_unlock(&res->spinlock);
            have_lockres_ref = 1;
            if (wake)
                wake_up(&res->wq);
        }

        /* master is known, detach if not already detached.
         * ensures that only one assert_master call will happen
         * on this mle. */
        spin_lock(&dlm->master_lock);

        rr = atomic_read(&mle->mle_refs.refcount);
        if (mle->inuse > 0) {
            if (extra_ref && rr < 3)
                err = 1;
            else if (!extra_ref && rr < 2)
                err = 1;
        } else {
            if (extra_ref && rr < 2)
                err = 1;
            else if (!extra_ref && rr < 1)
                err = 1;
        }
        if (err) {
            mlog(ML_ERROR, "%s:%.*s: got assert master from %u "
                 "that will mess up this node, refs=%d, extra=%d, "
                 "inuse=%d\n", dlm->name, namelen, name,
                 assert->node_idx, rr, extra_ref, mle->inuse);
            dlm_print_one_mle(mle);
        }
        __dlm_unlink_mle(dlm, mle);
        __dlm_mle_detach_hb_events(dlm, mle);
        __dlm_put_mle(mle);
        if (extra_ref) {
            /* the assert master message now balances the extra
             * ref given by the master / migration request message.
             * if this is the last put, it will be removed
             * from the list. */
            __dlm_put_mle(mle);
        }
        spin_unlock(&dlm->master_lock);
    } else if (res) {
        if (res->owner != assert->node_idx) {
            mlog(0, "assert_master from %u, but current "
                 "owner is %u (%.*s), no mle\n", assert->node_idx,
                 res->owner, namelen, name);
        }
    }
    spin_unlock(&dlm->spinlock);

done:
    ret = 0;
    if (res) {
        spin_lock(&res->spinlock);
        res->state |= DLM_LOCK_RES_SETREF_INPROG;
        spin_unlock(&res->spinlock);
        *ret_data = (void *)res;
    }
    dlm_put(dlm);
    if (master_request) {
        mlog(0, "need to tell master to reassert\n");
        /* positive. negative would shoot down the node. */
        ret |= DLM_ASSERT_RESPONSE_REASSERT;
        if (!have_lockres_ref) {
            mlog(ML_ERROR, "strange, got assert from %u, MASTER "
                 "mle present here for %s:%.*s, but no lockres!\n",
                 assert->node_idx, dlm->name, namelen, name);
        }
    }
    if (have_lockres_ref) {
        /* let the master know we have a reference to the lockres */
        ret |= DLM_ASSERT_RESPONSE_MASTERY_REF;
        mlog(0, "%s:%.*s: got assert from %u, need a ref\n",
             dlm->name, namelen, name, assert->node_idx);
    }
    return ret;

kill:
    /* kill the caller! */
    mlog(ML_ERROR, "Bad message received from another node.  Dumping state "
         "and killing the other node now!  This node is OK and can continue.\n");
    __dlm_print_one_lock_resource(res);
    spin_unlock(&res->spinlock);
    spin_unlock(&dlm->spinlock);
    *ret_data = (void *)res;
    dlm_put(dlm);
    return -EINVAL;
}

void dlm_assert_master_post_handler(int status, void *data, void *ret_data)
{
    struct dlm_lock_resource *res = (struct dlm_lock_resource *)ret_data;

    if (ret_data) {
        spin_lock(&res->spinlock);
        res->state &= ~DLM_LOCK_RES_SETREF_INPROG;
        spin_unlock(&res->spinlock);
        wake_up(&res->wq);
        dlm_lockres_put(res);
    }
    return;
}

int dlm_dispatch_assert_master(struct dlm_ctxt *dlm,
                   struct dlm_lock_resource *res,
                   int ignore_higher, u8 request_from, u32 flags)
{
    struct dlm_work_item *item;
    item = kzalloc(sizeof(*item), GFP_NOFS);
    if (!item)
        return -ENOMEM;


    /* queue up work for dlm_assert_master_worker */
    dlm_grab(dlm);  /* get an extra ref for the work item */
    dlm_init_work_item(dlm, item, dlm_assert_master_worker, NULL);
    item->u.am.lockres = res; /* already have a ref */
    /* can optionally ignore node numbers higher than this node */
    item->u.am.ignore_higher = ignore_higher;
    item->u.am.request_from = request_from;
    item->u.am.flags = flags;

    if (ignore_higher)
        mlog(0, "IGNORE HIGHER: %.*s\n", res->lockname.len,
             res->lockname.name);

    spin_lock(&dlm->work_lock);
    list_add_tail(&item->list, &dlm->work_list);
    spin_unlock(&dlm->work_lock);

    queue_work(dlm->dlm_worker, &dlm->dispatched_work);
    return 0;
}

static void dlm_assert_master_worker(struct dlm_work_item *item, void *data)
{
    struct dlm_ctxt *dlm = data;
    int ret = 0;
    struct dlm_lock_resource *res;
    unsigned long nodemap[BITS_TO_LONGS(O2NM_MAX_NODES)];
    int ignore_higher;
    int bit;
    u8 request_from;
    u32 flags;

    dlm = item->dlm;
    res = item->u.am.lockres;
    ignore_higher = item->u.am.ignore_higher;
    request_from = item->u.am.request_from;
    flags = item->u.am.flags;

    spin_lock(&dlm->spinlock);
    memcpy(nodemap, dlm->domain_map, sizeof(nodemap));
    spin_unlock(&dlm->spinlock);

    clear_bit(dlm->node_num, nodemap);
    if (ignore_higher) {
        /* if is this just to clear up mles for nodes below
         * this node, do not send the message to the original
         * caller or any node number higher than this */
        clear_bit(request_from, nodemap);
        bit = dlm->node_num;
        while (1) {
            bit = find_next_bit(nodemap, O2NM_MAX_NODES,
                        bit+1);
                if (bit >= O2NM_MAX_NODES)
                break;
            clear_bit(bit, nodemap);
        }
    }

    /*
     * If we're migrating this lock to someone else, we are no
     * longer allowed to assert out own mastery.  OTOH, we need to
     * prevent migration from starting while we're still asserting
     * our dominance.  The reserved ast delays migration.
     */
    spin_lock(&res->spinlock);
    if (res->state & DLM_LOCK_RES_MIGRATING) {
        mlog(0, "Someone asked us to assert mastery, but we're "
             "in the middle of migration.  Skipping assert, "
             "the new master will handle that.\n");
        spin_unlock(&res->spinlock);
        goto put;
    } else
        __dlm_lockres_reserve_ast(res);
    spin_unlock(&res->spinlock);

    /* this call now finishes out the nodemap
     * even if one or more nodes die */
    mlog(0, "worker about to master %.*s here, this=%u\n",
             res->lockname.len, res->lockname.name, dlm->node_num);
    ret = dlm_do_assert_master(dlm, res, nodemap, flags);
    if (ret < 0) {
        /* no need to restart, we are done */
        if (!dlm_is_host_down(ret))
            mlog_errno(ret);
    }

    /* Ok, we've asserted ourselves.  Let's let migration start. */
    dlm_lockres_release_ast(dlm, res);

put:
    dlm_lockres_put(res);

    mlog(0, "finished with dlm_assert_master_worker\n");
}

/* SPECIAL CASE for the $RECOVERY lock used by the recovery thread.
 * We cannot wait for node recovery to complete to begin mastering this
 * lockres because this lockres is used to kick off recovery! ;-)
 * So, do a pre-check on all living nodes to see if any of those nodes
 * think that $RECOVERY is currently mastered by a dead node.  If so,
 * we wait a short time to allow that node to get notified by its own
 * heartbeat stack, then check again.  All $RECOVERY lock resources
 * mastered by dead nodes are purged when the hearbeat callback is
 * fired, so we can know for sure that it is safe to continue once
 * the node returns a live node or no node.  */
static int dlm_pre_master_reco_lockres(struct dlm_ctxt *dlm,
                       struct dlm_lock_resource *res)
{
    struct dlm_node_iter iter;
    int nodenum;
    int ret = 0;
    u8 master = DLM_LOCK_RES_OWNER_UNKNOWN;

    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, &master);
        if (ret < 0) {
            mlog_errno(ret);
            if (!dlm_is_host_down(ret))
                BUG();
            /* host is down, so answer for that node would be
             * DLM_LOCK_RES_OWNER_UNKNOWN.  continue. */
            ret = 0;
        }

        if (master != DLM_LOCK_RES_OWNER_UNKNOWN) {
            /* check to see if this master is in the recovery map */
            spin_lock(&dlm->spinlock);
            if (test_bit(master, dlm->recovery_map)) {
                mlog(ML_NOTICE, "%s: node %u has not seen "
                     "node %u go down yet, and thinks the "
                     "dead node is mastering the recovery "
                     "lock.  must wait.\n", dlm->name,
                     nodenum, master);
                ret = -EAGAIN;
            }
            spin_unlock(&dlm->spinlock);
            mlog(0, "%s: reco lock master is %u\n", dlm->name,
                 master);
            break;
        }
    }
    return ret;
}

/*
 * DLM_DEREF_LOCKRES_MSG
 */

int dlm_drop_lockres_ref(struct dlm_ctxt *dlm, struct dlm_lock_resource *res)
{
    struct dlm_deref_lockres deref;
    int ret = 0, r;
    const char *lockname;
    unsigned int namelen;

    lockname = res->lockname.name;
    namelen = res->lockname.len;
    BUG_ON(namelen > O2NM_MAX_NAME_LEN);

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

    ret = o2net_send_message(DLM_DEREF_LOCKRES_MSG, dlm->key,
                 &deref, sizeof(deref), res->owner, &r);
    if (ret < 0)
        mlog(ML_ERROR, "%s: res %.*s, error %d send DEREF to node %u\n",
             dlm->name, namelen, lockname, ret, res->owner);
    else if (r < 0) {
        /* BAD.  other node says I did not have a ref. */
        mlog(ML_ERROR, "%s: res %.*s, DEREF to node %u got %d\n",
             dlm->name, namelen, lockname, res->owner, r);
        dlm_print_one_lock_resource(res);
        BUG();
    }
    return ret;
}

int dlm_deref_lockres_handler(struct o2net_msg *msg, u32 len, void *data,
                  void **ret_data)
{
    struct dlm_ctxt *dlm = data;
    struct dlm_deref_lockres *deref = (struct dlm_deref_lockres *)msg->buf;
    struct dlm_lock_resource *res = NULL;
    char *name;
    unsigned int namelen;
    int ret = -EINVAL;
    u8 node;
    unsigned int hash;
    struct dlm_work_item *item;
    int cleared = 0;
    int dispatch = 0;

    if (!dlm_grab(dlm))
        return 0;

    name = deref->name;
    namelen = deref->namelen;
    node = deref->node_idx;

    if (namelen > DLM_LOCKID_NAME_MAX) {
        mlog(ML_ERROR, "Invalid name length!");
        goto done;
    }
    if (deref->node_idx >= O2NM_MAX_NODES) {
        mlog(ML_ERROR, "Invalid node number: %u\n", node);
        goto done;
    }

    hash = dlm_lockid_hash(name, namelen);

    spin_lock(&dlm->spinlock);
    res = __dlm_lookup_lockres_full(dlm, name, namelen, hash);
    if (!res) {
        spin_unlock(&dlm->spinlock);
        mlog(ML_ERROR, "%s:%.*s: bad lockres name\n",
             dlm->name, namelen, name);
        goto done;
    }
    spin_unlock(&dlm->spinlock);

    spin_lock(&res->spinlock);
    if (res->state & DLM_LOCK_RES_SETREF_INPROG)
        dispatch = 1;
    else {
        BUG_ON(res->state & DLM_LOCK_RES_DROPPING_REF);
        if (test_bit(node, res->refmap)) {
            dlm_lockres_clear_refmap_bit(dlm, res, node);
            cleared = 1;
        }
    }
    spin_unlock(&res->spinlock);

    if (!dispatch) {
        if (cleared)
            dlm_lockres_calc_usage(dlm, res);
        else {
            mlog(ML_ERROR, "%s:%.*s: node %u trying to drop ref "
                "but it is already dropped!\n", dlm->name,
                res->lockname.len, res->lockname.name, node);
            dlm_print_one_lock_resource(res);
        }
        ret = 0;
        goto done;
    }

    item = kzalloc(sizeof(*item), GFP_NOFS);
    if (!item) {
        ret = -ENOMEM;
        mlog_errno(ret);
        goto done;
    }

    dlm_init_work_item(dlm, item, dlm_deref_lockres_worker, NULL);
    item->u.dl.deref_res = res;
    item->u.dl.deref_node = node;

    spin_lock(&dlm->work_lock);
    list_add_tail(&item->list, &dlm->work_list);
    spin_unlock(&dlm->work_lock);

    queue_work(dlm->dlm_worker, &dlm->dispatched_work);
    return 0;

done:
    if (res)
        dlm_lockres_put(res);
    dlm_put(dlm);

    return ret;
}

static void dlm_deref_lockres_worker(struct dlm_work_item *item, void *data)
{
    struct dlm_ctxt *dlm;
    struct dlm_lock_resource *res;
    u8 node;
    u8 cleared = 0;

    dlm = item->dlm;
    res = item->u.dl.deref_res;
    node = item->u.dl.deref_node;

    spin_lock(&res->spinlock);
    BUG_ON(res->state & DLM_LOCK_RES_DROPPING_REF);
    if (test_bit(node, res->refmap)) {
        __dlm_wait_on_lockres_flags(res, DLM_LOCK_RES_SETREF_INPROG);
        dlm_lockres_clear_refmap_bit(dlm, res, node);
        cleared = 1;
    }
    spin_unlock(&res->spinlock);

    if (cleared) {
        mlog(0, "%s:%.*s node %u ref dropped in dispatch\n",
             dlm->name, res->lockname.len, res->lockname.name, node);
        dlm_lockres_calc_usage(dlm, res);
    } else {
        mlog(ML_ERROR, "%s:%.*s: node %u trying to drop ref "
             "but it is already dropped!\n", dlm->name,
             res->lockname.len, res->lockname.name, node);
        dlm_print_one_lock_resource(res);
    }

    dlm_lockres_put(res);
}

/*
 * A migrateable resource is one that is :
 * 1. locally mastered, and,
 * 2. zero local locks, and,
 * 3. one or more non-local locks, or, one or more references
 * Returns 1 if yes, 0 if not.
 */
static int dlm_is_lockres_migrateable(struct dlm_ctxt *dlm,
                      struct dlm_lock_resource *res)
{
    enum dlm_lockres_list idx;
    int nonlocal = 0, node_ref;
    struct list_head *queue;
    struct dlm_lock *lock;
    u64 cookie;

    assert_spin_locked(&res->spinlock);

    if (res->owner != dlm->node_num)
        return 0;

        for (idx = DLM_GRANTED_LIST; idx <= DLM_BLOCKED_LIST; idx++) {
        queue = dlm_list_idx_to_ptr(res, idx);
        list_for_each_entry(lock, queue, list) {
            if (lock->ml.node != dlm->node_num) {
                nonlocal++;
                continue;
            }
            cookie = be64_to_cpu(lock->ml.cookie);
            mlog(0, "%s: Not migrateable res %.*s, lock %u:%llu on "
                 "%s list\n", dlm->name, res->lockname.len,
                 res->lockname.name,
                 dlm_get_lock_cookie_node(cookie),
                 dlm_get_lock_cookie_seq(cookie),
                 dlm_list_in_text(idx));
            return 0;
        }
    }

    if (!nonlocal) {
        node_ref = find_next_bit(res->refmap, O2NM_MAX_NODES, 0);
        if (node_ref >= O2NM_MAX_NODES)
            return 0;
    }

    mlog(0, "%s: res %.*s, Migrateable\n", dlm->name, res->lockname.len,
         res->lockname.name);

    return 1;
}

/*
 * DLM_MIGRATE_LOCKRES
 */


static int dlm_migrate_lockres(struct dlm_ctxt *dlm,
                   struct dlm_lock_resource *res, u8 target)
{
    struct dlm_master_list_entry *mle = NULL;
    struct dlm_master_list_entry *oldmle = NULL;
    struct dlm_migratable_lockres *mres = NULL;
    int ret = 0;
    const char *name;
    unsigned int namelen;
    int mle_added = 0;
    int wake = 0;

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

    BUG_ON(target == O2NM_MAX_NODES);

    name = res->lockname.name;
    namelen = res->lockname.len;

    mlog(0, "%s: Migrating %.*s to node %u\n", dlm->name, namelen, name,
         target);

    /* preallocate up front. if this fails, abort */
    ret = -ENOMEM;
    mres = (struct dlm_migratable_lockres *) __get_free_page(GFP_NOFS);
    if (!mres) {
        mlog_errno(ret);
        goto leave;
    }

    mle = kmem_cache_alloc(dlm_mle_cache, GFP_NOFS);
    if (!mle) {
        mlog_errno(ret);
        goto leave;
    }
    ret = 0;

    /*
     * clear any existing master requests and
     * add the migration mle to the list
     */
    spin_lock(&dlm->spinlock);
    spin_lock(&dlm->master_lock);
    ret = dlm_add_migration_mle(dlm, res, mle, &oldmle, name,
                    namelen, target, dlm->node_num);
    spin_unlock(&dlm->master_lock);
    spin_unlock(&dlm->spinlock);

    if (ret == -EEXIST) {
        mlog(0, "another process is already migrating it\n");
        goto fail;
    }
    mle_added = 1;

    /*
     * set the MIGRATING flag and flush asts
     * if we fail after this we need to re-dirty the lockres
     */
    if (dlm_mark_lockres_migrating(dlm, res, target) < 0) {
        mlog(ML_ERROR, "tried to migrate %.*s to %u, but "
             "the target went down.\n", res->lockname.len,
             res->lockname.name, target);
        spin_lock(&res->spinlock);
        res->state &= ~DLM_LOCK_RES_MIGRATING;
        wake = 1;
        spin_unlock(&res->spinlock);
        ret = -EINVAL;
    }

fail:
    if (oldmle) {
        /* master is known, detach if not already detached */
        dlm_mle_detach_hb_events(dlm, oldmle);
        dlm_put_mle(oldmle);
    }

    if (ret < 0) {
        if (mle_added) {
            dlm_mle_detach_hb_events(dlm, mle);
            dlm_put_mle(mle);
        } else if (mle) {
            kmem_cache_free(dlm_mle_cache, mle);
            mle = NULL;
        }
        goto leave;
    }

    /*
     * at this point, we have a migration target, an mle
     * in the master list, and the MIGRATING flag set on
     * the lockres
     */

    /* now that remote nodes are spinning on the MIGRATING flag,
     * ensure that all assert_master work is flushed. */
    flush_workqueue(dlm->dlm_worker);

    /* get an extra reference on the mle.
     * otherwise the assert_master from the new
     * master will destroy this.
     * also, make sure that all callers of dlm_get_mle
     * take both dlm->spinlock and dlm->master_lock */
    spin_lock(&dlm->spinlock);
    spin_lock(&dlm->master_lock);
    dlm_get_mle_inuse(mle);
    spin_unlock(&dlm->master_lock);
    spin_unlock(&dlm->spinlock);

    /* notify new node and send all lock state */
    /* call send_one_lockres with migration flag.
     * this serves as notice to the target node that a
     * migration is starting. */
    ret = dlm_send_one_lockres(dlm, res, mres, target,
                   DLM_MRES_MIGRATION);

    if (ret < 0) {
        mlog(0, "migration to node %u failed with %d\n",
             target, ret);
        /* migration failed, detach and clean up mle */
        dlm_mle_detach_hb_events(dlm, mle);
        dlm_put_mle(mle);
        dlm_put_mle_inuse(mle);
        spin_lock(&res->spinlock);
        res->state &= ~DLM_LOCK_RES_MIGRATING;
        wake = 1;
        spin_unlock(&res->spinlock);
        if (dlm_is_host_down(ret))
            dlm_wait_for_node_death(dlm, target,
                        DLM_NODE_DEATH_WAIT_MAX);
        goto leave;
    }

    /* at this point, the target sends a message to all nodes,
     * (using dlm_do_migrate_request).  this node is skipped since
     * we had to put an mle in the list to begin the process.  this
     * node now waits for target to do an assert master.  this node
     * will be the last one notified, ensuring that the migration
     * is complete everywhere.  if the target dies while this is
     * going on, some nodes could potentially see the target as the
     * master, so it is important that my recovery finds the migration
     * mle and sets the master to UNKNOWN. */


    /* wait for new node to assert master */
    while (1) {
        ret = wait_event_interruptible_timeout(mle->wq,
                    (atomic_read(&mle->woken) == 1),
                    msecs_to_jiffies(5000));

        if (ret >= 0) {
                if (atomic_read(&mle->woken) == 1 ||
                res->owner == target)
                break;

            mlog(0, "%s:%.*s: timed out during migration\n",
                 dlm->name, res->lockname.len, res->lockname.name);
            /* avoid hang during shutdown when migrating lockres
             * to a node which also goes down */
            if (dlm_is_node_dead(dlm, target)) {
                mlog(0, "%s:%.*s: expected migration "
                     "target %u is no longer up, restarting\n",
                     dlm->name, res->lockname.len,
                     res->lockname.name, target);
                ret = -EINVAL;
                /* migration failed, detach and clean up mle */
                dlm_mle_detach_hb_events(dlm, mle);
                dlm_put_mle(mle);
                dlm_put_mle_inuse(mle);
                spin_lock(&res->spinlock);
                res->state &= ~DLM_LOCK_RES_MIGRATING;
                wake = 1;
                spin_unlock(&res->spinlock);
                goto leave;
            }
        } else
            mlog(0, "%s:%.*s: caught signal during migration\n",
                 dlm->name, res->lockname.len, res->lockname.name);
    }

    /* all done, set the owner, clear the flag */
    spin_lock(&res->spinlock);
    dlm_set_lockres_owner(dlm, res, target);
    res->state &= ~DLM_LOCK_RES_MIGRATING;
    dlm_remove_nonlocal_locks(dlm, res);
    spin_unlock(&res->spinlock);
    wake_up(&res->wq);

    /* master is known, detach if not already detached */
    dlm_mle_detach_hb_events(dlm, mle);
    dlm_put_mle_inuse(mle);
    ret = 0;

    dlm_lockres_calc_usage(dlm, res);

leave:
    /* re-dirty the lockres if we failed */
    if (ret < 0)
        dlm_kick_thread(dlm, res);

    /* wake up waiters if the MIGRATING flag got set
     * but migration failed */
    if (wake)
        wake_up(&res->wq);

    if (mres)
        free_page((unsigned long)mres);

    dlm_put(dlm);

    mlog(0, "%s: Migrating %.*s to %u, returns %d\n", dlm->name, namelen,
         name, target, ret);
    return ret;
}

#define DLM_MIGRATION_RETRY_MS  100

/*
 * Should be called only after beginning the domain leave process.
 * There should not be any remaining locks on nonlocal lock resources,
 * and there should be no local locks left on locally mastered resources.
 *
 * Called with the dlm spinlock held, may drop it to do migration, but
 * will re-acquire before exit.
 *
 * Returns: 1 if dlm->spinlock was dropped/retaken, 0 if never dropped
 */
int dlm_empty_lockres(struct dlm_ctxt *dlm, struct dlm_lock_resource *res)
{
    int ret;
    int lock_dropped = 0;
    u8 target = O2NM_MAX_NODES;

    assert_spin_locked(&dlm->spinlock);

    spin_lock(&res->spinlock);
    if (dlm_is_lockres_migrateable(dlm, res))
        target = dlm_pick_migration_target(dlm, res);
    spin_unlock(&res->spinlock);

    if (target == O2NM_MAX_NODES)
        goto leave;

    /* Wheee! Migrate lockres here! Will sleep so drop spinlock. */
    spin_unlock(&dlm->spinlock);
    lock_dropped = 1;
    ret = dlm_migrate_lockres(dlm, res, target);
    if (ret)
        mlog(0, "%s: res %.*s, Migrate to node %u failed with %d\n",
             dlm->name, res->lockname.len, res->lockname.name,
             target, ret);
    spin_lock(&dlm->spinlock);
leave:
    return lock_dropped;
}

int dlm_lock_basts_flushed(struct dlm_ctxt *dlm, struct dlm_lock *lock)
{
    int ret;
    spin_lock(&dlm->ast_lock);
    spin_lock(&lock->spinlock);
    ret = (list_empty(&lock->bast_list) && !lock->bast_pending);
    spin_unlock(&lock->spinlock);
    spin_unlock(&dlm->ast_lock);
    return ret;
}

static int dlm_migration_can_proceed(struct dlm_ctxt *dlm,
                     struct dlm_lock_resource *res,
                     u8 mig_target)
{
    int can_proceed;
    spin_lock(&res->spinlock);
    can_proceed = !!(res->state & DLM_LOCK_RES_MIGRATING);
    spin_unlock(&res->spinlock);

    /* target has died, so make the caller break out of the
     * wait_event, but caller must recheck the domain_map */
    spin_lock(&dlm->spinlock);
    if (!test_bit(mig_target, dlm->domain_map))
        can_proceed = 1;
    spin_unlock(&dlm->spinlock);
    return can_proceed;
}

static int dlm_lockres_is_dirty(struct dlm_ctxt *dlm,
                struct dlm_lock_resource *res)
{
    int ret;
    spin_lock(&res->spinlock);
    ret = !!(res->state & DLM_LOCK_RES_DIRTY);
    spin_unlock(&res->spinlock);
    return ret;
}


static int dlm_mark_lockres_migrating(struct dlm_ctxt *dlm,
                       struct dlm_lock_resource *res,
                       u8 target)
{
    int ret = 0;

    mlog(0, "dlm_mark_lockres_migrating: %.*s, from %u to %u\n",
           res->lockname.len, res->lockname.name, dlm->node_num,
           target);
    /* need to set MIGRATING flag on lockres.  this is done by
     * ensuring that all asts have been flushed for this lockres. */
    spin_lock(&res->spinlock);
    BUG_ON(res->migration_pending);
    res->migration_pending = 1;
    /* strategy is to reserve an extra ast then release
     * it below, letting the release do all of the work */
    __dlm_lockres_reserve_ast(res);
    spin_unlock(&res->spinlock);

    /* now flush all the pending asts */
    dlm_kick_thread(dlm, res);
    /* before waiting on DIRTY, block processes which may
     * try to dirty the lockres before MIGRATING is set */
    spin_lock(&res->spinlock);
    BUG_ON(res->state & DLM_LOCK_RES_BLOCK_DIRTY);
    res->state |= DLM_LOCK_RES_BLOCK_DIRTY;
    spin_unlock(&res->spinlock);
    /* now wait on any pending asts and the DIRTY state */
    wait_event(dlm->ast_wq, !dlm_lockres_is_dirty(dlm, res));
    dlm_lockres_release_ast(dlm, res);

    mlog(0, "about to wait on migration_wq, dirty=%s\n",
           res->state & DLM_LOCK_RES_DIRTY ? "yes" : "no");
    /* if the extra ref we just put was the final one, this
     * will pass thru immediately.  otherwise, we need to wait
     * for the last ast to finish. */
again:
    ret = wait_event_interruptible_timeout(dlm->migration_wq,
           dlm_migration_can_proceed(dlm, res, target),
           msecs_to_jiffies(1000));
    if (ret < 0) {
        mlog(0, "woken again: migrating? %s, dead? %s\n",
               res->state & DLM_LOCK_RES_MIGRATING ? "yes":"no",
               test_bit(target, dlm->domain_map) ? "no":"yes");
    } else {
        mlog(0, "all is well: migrating? %s, dead? %s\n",
               res->state & DLM_LOCK_RES_MIGRATING ? "yes":"no",
               test_bit(target, dlm->domain_map) ? "no":"yes");
    }
    if (!dlm_migration_can_proceed(dlm, res, target)) {
        mlog(0, "trying again...\n");
        goto again;
    }

    ret = 0;
    /* did the target go down or die? */
    spin_lock(&dlm->spinlock);
    if (!test_bit(target, dlm->domain_map)) {
        mlog(ML_ERROR, "aha. migration target %u just went down\n",
             target);
        ret = -EHOSTDOWN;
    }
    spin_unlock(&dlm->spinlock);

    /*
     * if target is down, we need to clear DLM_LOCK_RES_BLOCK_DIRTY for
     * another try; otherwise, we are sure the MIGRATING state is there,
     * drop the unneded state which blocked threads trying to DIRTY
     */
    spin_lock(&res->spinlock);
    BUG_ON(!(res->state & DLM_LOCK_RES_BLOCK_DIRTY));
    res->state &= ~DLM_LOCK_RES_BLOCK_DIRTY;
    if (!ret)
        BUG_ON(!(res->state & DLM_LOCK_RES_MIGRATING));
    spin_unlock(&res->spinlock);

    /*
     * at this point:
     *
     *   o the DLM_LOCK_RES_MIGRATING flag is set if target not down
     *   o there are no pending asts on this lockres
     *   o all processes trying to reserve an ast on this
     *     lockres must wait for the MIGRATING flag to clear
     */
    return ret;
}

/* last step in the migration process.
 * original master calls this to free all of the dlm_lock
 * structures that used to be for other nodes. */
static void dlm_remove_nonlocal_locks(struct dlm_ctxt *dlm,
                      struct dlm_lock_resource *res)
{
    struct list_head *queue = &res->granted;
    int i, bit;
    struct dlm_lock *lock, *next;

    assert_spin_locked(&res->spinlock);

    BUG_ON(res->owner == dlm->node_num);

    for (i=0; i<3; i++) {
        list_for_each_entry_safe(lock, next, queue, list) {
            if (lock->ml.node != dlm->node_num) {
                mlog(0, "putting lock for node %u\n",
                     lock->ml.node);
                /* be extra careful */
                BUG_ON(!list_empty(&lock->ast_list));
                BUG_ON(!list_empty(&lock->bast_list));
                BUG_ON(lock->ast_pending);
                BUG_ON(lock->bast_pending);
                dlm_lockres_clear_refmap_bit(dlm, res,
                                 lock->ml.node);
                list_del_init(&lock->list);
                dlm_lock_put(lock);
                /* In a normal unlock, we would have added a
                 * DLM_UNLOCK_FREE_LOCK action. Force it. */
                dlm_lock_put(lock);
            }
        }
        queue++;
    }
    bit = 0;
    while (1) {
        bit = find_next_bit(res->refmap, O2NM_MAX_NODES, bit);
        if (bit >= O2NM_MAX_NODES)
            break;
        /* do not clear the local node reference, if there is a
         * process holding this, let it drop the ref itself */
        if (bit != dlm->node_num) {
            mlog(0, "%s:%.*s: node %u had a ref to this "
                 "migrating lockres, clearing\n", dlm->name,
                 res->lockname.len, res->lockname.name, bit);
            dlm_lockres_clear_refmap_bit(dlm, res, bit);
        }
        bit++;
    }
}

/*
 * Pick a node to migrate the lock resource to. This function selects a
 * potential target based first on the locks and then on refmap. It skips
 * nodes that are in the process of exiting the domain.
 */
static u8 dlm_pick_migration_target(struct dlm_ctxt *dlm,
                    struct dlm_lock_resource *res)
{
    enum dlm_lockres_list idx;
    struct list_head *queue = &res->granted;
    struct dlm_lock *lock;
    int noderef;
    u8 nodenum = O2NM_MAX_NODES;

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

    /* Go through all the locks */
    for (idx = DLM_GRANTED_LIST; idx <= DLM_BLOCKED_LIST; idx++) {
        queue = dlm_list_idx_to_ptr(res, idx);
        list_for_each_entry(lock, queue, list) {
            if (lock->ml.node == dlm->node_num)
                continue;
            if (test_bit(lock->ml.node, dlm->exit_domain_map))
                continue;
            nodenum = lock->ml.node;
            goto bail;
        }
    }

    /* Go thru the refmap */
    noderef = -1;
    while (1) {
        noderef = find_next_bit(res->refmap, O2NM_MAX_NODES,
                    noderef + 1);
        if (noderef >= O2NM_MAX_NODES)
            break;
        if (noderef == dlm->node_num)
            continue;
        if (test_bit(noderef, dlm->exit_domain_map))
            continue;
        nodenum = noderef;
        goto bail;
    }

bail:
    return nodenum;
}

/* this is called by the new master once all lockres
 * data has been received */
static int dlm_do_migrate_request(struct dlm_ctxt *dlm,
                  struct dlm_lock_resource *res,
                  u8 master, u8 new_master,
                  struct dlm_node_iter *iter)
{
    struct dlm_migrate_request migrate;
    int ret, skip, status = 0;
    int nodenum;

    memset(&migrate, 0, sizeof(migrate));
    migrate.namelen = res->lockname.len;
    memcpy(migrate.name, res->lockname.name, migrate.namelen);
    migrate.new_master = new_master;
    migrate.master = master;

    ret = 0;

    /* send message to all nodes, except the master and myself */
    while ((nodenum = dlm_node_iter_next(iter)) >= 0) {
        if (nodenum == master ||
            nodenum == new_master)
            continue;

        /* We could race exit domain. If exited, skip. */
        spin_lock(&dlm->spinlock);
        skip = (!test_bit(nodenum, dlm->domain_map));
        spin_unlock(&dlm->spinlock);
        if (skip) {
            clear_bit(nodenum, iter->node_map);
            continue;
        }

        ret = o2net_send_message(DLM_MIGRATE_REQUEST_MSG, dlm->key,
                     &migrate, sizeof(migrate), nodenum,
                     &status);
        if (ret < 0) {
            mlog(ML_ERROR, "%s: res %.*s, Error %d send "
                 "MIGRATE_REQUEST to node %u\n", dlm->name,
                 migrate.namelen, migrate.name, ret, nodenum);
            if (!dlm_is_host_down(ret)) {
                mlog(ML_ERROR, "unhandled error=%d!\n", ret);
                BUG();
            }
            clear_bit(nodenum, iter->node_map);
            ret = 0;
        } else if (status < 0) {
            mlog(0, "migrate request (node %u) returned %d!\n",
                 nodenum, status);
            ret = status;
        } else if (status == DLM_MIGRATE_RESPONSE_MASTERY_REF) {
            /* during the migration request we short-circuited
             * the mastery of the lockres.  make sure we have
             * a mastery ref for nodenum */
            mlog(0, "%s:%.*s: need ref for node %u\n",
                 dlm->name, res->lockname.len, res->lockname.name,
                 nodenum);
            spin_lock(&res->spinlock);
            dlm_lockres_set_refmap_bit(dlm, res, nodenum);
            spin_unlock(&res->spinlock);
        }
    }

    if (ret < 0)
        mlog_errno(ret);

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


/* if there is an existing mle for this lockres, we now know who the master is.
 * (the one who sent us *this* message) we can clear it up right away.
 * since the process that put the mle on the list still has a reference to it,
 * we can unhash it now, set the master and wake the process.  as a result,
 * we will have no mle in the list to start with.  now we can add an mle for
 * the migration and this should be the only one found for those scanning the
 * list.  */
int dlm_migrate_request_handler(struct o2net_msg *msg, u32 len, void *data,
                void **ret_data)
{
    struct dlm_ctxt *dlm = data;
    struct dlm_lock_resource *res = NULL;
    struct dlm_migrate_request *migrate = (struct dlm_migrate_request *) msg->buf;
    struct dlm_master_list_entry *mle = NULL, *oldmle = NULL;
    const char *name;
    unsigned int namelen, hash;
    int ret = 0;

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

    name = migrate->name;
    namelen = migrate->namelen;
    hash = dlm_lockid_hash(name, namelen);

    /* preallocate.. if this fails, abort */
    mle = kmem_cache_alloc(dlm_mle_cache, GFP_NOFS);

    if (!mle) {
        ret = -ENOMEM;
        goto leave;
    }

    /* check for pre-existing lock */
    spin_lock(&dlm->spinlock);
    res = __dlm_lookup_lockres(dlm, name, namelen, hash);
    if (res) {
        spin_lock(&res->spinlock);
        if (res->state & DLM_LOCK_RES_RECOVERING) {
            /* if all is working ok, this can only mean that we got
            * a migrate request from a node that we now see as
            * dead.  what can we do here?  drop it to the floor? */
            spin_unlock(&res->spinlock);
            mlog(ML_ERROR, "Got a migrate request, but the "
                 "lockres is marked as recovering!");
            kmem_cache_free(dlm_mle_cache, mle);
            ret = -EINVAL; /* need a better solution */
            goto unlock;
        }
        res->state |= DLM_LOCK_RES_MIGRATING;
        spin_unlock(&res->spinlock);
    }

    spin_lock(&dlm->master_lock);
    /* ignore status.  only nonzero status would BUG. */
    ret = dlm_add_migration_mle(dlm, res, mle, &oldmle,
                    name, namelen,
                    migrate->new_master,
                    migrate->master);

    spin_unlock(&dlm->master_lock);
unlock:
    spin_unlock(&dlm->spinlock);

    if (oldmle) {
        /* master is known, detach if not already detached */
        dlm_mle_detach_hb_events(dlm, oldmle);
        dlm_put_mle(oldmle);
    }

    if (res)
        dlm_lockres_put(res);
leave:
    dlm_put(dlm);
    return ret;
}

/* must be holding dlm->spinlock and dlm->master_lock
 * when adding a migration mle, we can clear any other mles
 * in the master list because we know with certainty that
 * the master is "master".  so we remove any old mle from
 * the list after setting it's master field, and then add
 * the new migration mle.  this way we can hold with the rule
 * of having only one mle for a given lock name at all times. */
static int dlm_add_migration_mle(struct dlm_ctxt *dlm,
                 struct dlm_lock_resource *res,
                 struct dlm_master_list_entry *mle,
                 struct dlm_master_list_entry **oldmle,
                 const char *name, unsigned int namelen,
                 u8 new_master, u8 master)
{
    int found;
    int ret = 0;

    *oldmle = NULL;

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

    /* caller is responsible for any ref taken here on oldmle */
    found = dlm_find_mle(dlm, oldmle, (char *)name, namelen);
    if (found) {
        struct dlm_master_list_entry *tmp = *oldmle;
        spin_lock(&tmp->spinlock);
        if (tmp->type == DLM_MLE_MIGRATION) {
            if (master == dlm->node_num) {
                /* ah another process raced me to it */
                mlog(0, "tried to migrate %.*s, but some "
                     "process beat me to it\n",
                     namelen, name);
                ret = -EEXIST;
            } else {
                /* bad.  2 NODES are trying to migrate! */
                mlog(ML_ERROR, "migration error  mle: "
                     "master=%u new_master=%u // request: "
                     "master=%u new_master=%u // "
                     "lockres=%.*s\n",
                     tmp->master, tmp->new_master,
                     master, new_master,
                     namelen, name);
                BUG();
            }
        } else {
            /* this is essentially what assert_master does */
            tmp->master = master;
            atomic_set(&tmp->woken, 1);
            wake_up(&tmp->wq);
            /* remove it so that only one mle will be found */
            __dlm_unlink_mle(dlm, tmp);
            __dlm_mle_detach_hb_events(dlm, tmp);
            ret = DLM_MIGRATE_RESPONSE_MASTERY_REF;
            mlog(0, "%s:%.*s: master=%u, newmaster=%u, "
                "telling master to get ref for cleared out mle "
                "during migration\n", dlm->name, namelen, name,
                master, new_master);
        }
        spin_unlock(&tmp->spinlock);
    }

    /* now add a migration mle to the tail of the list */
    dlm_init_mle(mle, DLM_MLE_MIGRATION, dlm, res, name, namelen);
    mle->new_master = new_master;
    /* the new master will be sending an assert master for this.
     * at that point we will get the refmap reference */
    mle->master = master;
    /* do this for consistency with other mle types */
    set_bit(new_master, mle->maybe_map);
    __dlm_insert_mle(dlm, mle);

    return ret;
}

/*
 * Sets the owner of the lockres, associated to the mle, to UNKNOWN
 */
static struct dlm_lock_resource *dlm_reset_mleres_owner(struct dlm_ctxt *dlm,
                    struct dlm_master_list_entry *mle)
{
    struct dlm_lock_resource *res;

    /* Find the lockres associated to the mle and set its owner to UNK */
    res = __dlm_lookup_lockres(dlm, mle->mname, mle->mnamelen,
                   mle->mnamehash);
    if (res) {
        spin_unlock(&dlm->master_lock);

        /* move lockres onto recovery list */
        spin_lock(&res->spinlock);
        dlm_set_lockres_owner(dlm, res, DLM_LOCK_RES_OWNER_UNKNOWN);
        dlm_move_lockres_to_recovery_list(dlm, res);
        spin_unlock(&res->spinlock);
        dlm_lockres_put(res);

        /* about to get rid of mle, detach from heartbeat */
        __dlm_mle_detach_hb_events(dlm, mle);

        /* dump the mle */
        spin_lock(&dlm->master_lock);
        __dlm_put_mle(mle);
        spin_unlock(&dlm->master_lock);
    }

    return res;
}

static void dlm_clean_migration_mle(struct dlm_ctxt *dlm,
                    struct dlm_master_list_entry *mle)
{
    __dlm_mle_detach_hb_events(dlm, mle);

    spin_lock(&mle->spinlock);
    __dlm_unlink_mle(dlm, mle);
    atomic_set(&mle->woken, 1);
    spin_unlock(&mle->spinlock);

    wake_up(&mle->wq);
}

static void dlm_clean_block_mle(struct dlm_ctxt *dlm,
                struct dlm_master_list_entry *mle, u8 dead_node)
{
    int bit;

    BUG_ON(mle->type != DLM_MLE_BLOCK);

    spin_lock(&mle->spinlock);
    bit = find_next_bit(mle->maybe_map, O2NM_MAX_NODES, 0);
    if (bit != dead_node) {
        mlog(0, "mle found, but dead node %u would not have been "
             "master\n", dead_node);
        spin_unlock(&mle->spinlock);
    } else {
        /* Must drop the refcount by one since the assert_master will
         * never arrive. This may result in the mle being unlinked and
         * freed, but there may still be a process waiting in the
         * dlmlock path which is fine. */
        mlog(0, "node %u was expected master\n", dead_node);
        atomic_set(&mle->woken, 1);
        spin_unlock(&mle->spinlock);
        wake_up(&mle->wq);

        /* Do not need events any longer, so detach from heartbeat */
        __dlm_mle_detach_hb_events(dlm, mle);
        __dlm_put_mle(mle);
    }
}

void dlm_clean_master_list(struct dlm_ctxt *dlm, u8 dead_node)
{
    struct dlm_master_list_entry *mle;
    struct dlm_lock_resource *res;
    struct hlist_head *bucket;
    struct hlist_node *list;
    unsigned int i;

    mlog(0, "dlm=%s, dead node=%u\n", dlm->name, dead_node);
top:
    assert_spin_locked(&dlm->spinlock);

    /* clean the master list */
    spin_lock(&dlm->master_lock);
    for (i = 0; i < DLM_HASH_BUCKETS; i++) {
        bucket = dlm_master_hash(dlm, i);
        hlist_for_each(list, bucket) {
            mle = hlist_entry(list, struct dlm_master_list_entry,
                      master_hash_node);

            BUG_ON(mle->type != DLM_MLE_BLOCK &&
                   mle->type != DLM_MLE_MASTER &&
                   mle->type != DLM_MLE_MIGRATION);

            /* MASTER mles are initiated locally. The waiting
             * process will notice the node map change shortly.
             * Let that happen as normal. */
            if (mle->type == DLM_MLE_MASTER)
                continue;

            /* BLOCK mles are initiated by other nodes. Need to
             * clean up if the dead node would have been the
             * master. */
            if (mle->type == DLM_MLE_BLOCK) {
                dlm_clean_block_mle(dlm, mle, dead_node);
                continue;
            }

            /* Everything else is a MIGRATION mle */

            /* The rule for MIGRATION mles is that the master
             * becomes UNKNOWN if *either* the original or the new
             * master dies. All UNKNOWN lockres' are sent to
             * whichever node becomes the recovery master. The new
             * master is responsible for determining if there is
             * still a master for this lockres, or if he needs to
             * take over mastery. Either way, this node should
             * expect another message to resolve this. */

            if (mle->master != dead_node &&
                mle->new_master != dead_node)
                continue;

            /* If we have reached this point, this mle needs to be
             * removed from the list and freed. */
            dlm_clean_migration_mle(dlm, mle);

            mlog(0, "%s: node %u died during migration from "
                 "%u to %u!\n", dlm->name, dead_node, mle->master,
                 mle->new_master);

            /* If we find a lockres associated with the mle, we've
             * hit this rare case that messes up our lock ordering.
             * If so, we need to drop the master lock so that we can
             * take the lockres lock, meaning that we will have to
             * restart from the head of list. */
            res = dlm_reset_mleres_owner(dlm, mle);
            if (res)
                /* restart */
                goto top;

            /* This may be the last reference */
            __dlm_put_mle(mle);
        }
    }
    spin_unlock(&dlm->master_lock);
}

int dlm_finish_migration(struct dlm_ctxt *dlm, struct dlm_lock_resource *res,
             u8 old_master)
{
    struct dlm_node_iter iter;
    int ret = 0;

    spin_lock(&dlm->spinlock);
    dlm_node_iter_init(dlm->domain_map, &iter);
    clear_bit(old_master, iter.node_map);
    clear_bit(dlm->node_num, iter.node_map);
    spin_unlock(&dlm->spinlock);

    /* ownership of the lockres is changing.  account for the
     * mastery reference here since old_master will briefly have
     * a reference after the migration completes */
    spin_lock(&res->spinlock);
    dlm_lockres_set_refmap_bit(dlm, res, old_master);
    spin_unlock(&res->spinlock);

    mlog(0, "now time to do a migrate request to other nodes\n");
    ret = dlm_do_migrate_request(dlm, res, old_master,
                     dlm->node_num, &iter);
    if (ret < 0) {
        mlog_errno(ret);
        goto leave;
    }

    mlog(0, "doing assert master of %.*s to all except the original node\n",
         res->lockname.len, res->lockname.name);
    /* this call now finishes out the nodemap
     * even if one or more nodes die */
    ret = dlm_do_assert_master(dlm, res, iter.node_map,
                   DLM_ASSERT_MASTER_FINISH_MIGRATION);
    if (ret < 0) {
        /* no longer need to retry.  all living nodes contacted. */
        mlog_errno(ret);
        ret = 0;
    }

    memset(iter.node_map, 0, sizeof(iter.node_map));
    set_bit(old_master, iter.node_map);
    mlog(0, "doing assert master of %.*s back to %u\n",
         res->lockname.len, res->lockname.name, old_master);
    ret = dlm_do_assert_master(dlm, res, iter.node_map,
                   DLM_ASSERT_MASTER_FINISH_MIGRATION);
    if (ret < 0) {
        mlog(0, "assert master to original master failed "
             "with %d.\n", ret);
        /* the only nonzero status here would be because of
         * a dead original node.  we're done. */
        ret = 0;
    }

    /* all done, set the owner, clear the flag */
    spin_lock(&res->spinlock);
    dlm_set_lockres_owner(dlm, res, dlm->node_num);
    res->state &= ~DLM_LOCK_RES_MIGRATING;
    spin_unlock(&res->spinlock);
    /* re-dirty it on the new master */
    dlm_kick_thread(dlm, res);
    wake_up(&res->wq);
leave:
    return ret;
}

/*
 * LOCKRES AST REFCOUNT
 * this is integral to migration
 */

/* for future intent to call an ast, reserve one ahead of time.
 * this should be called only after waiting on the lockres
 * with dlm_wait_on_lockres, and while still holding the
 * spinlock after the call. */
void __dlm_lockres_reserve_ast(struct dlm_lock_resource *res)
{
    assert_spin_locked(&res->spinlock);
    if (res->state & DLM_LOCK_RES_MIGRATING) {
        __dlm_print_one_lock_resource(res);
    }
    BUG_ON(res->state & DLM_LOCK_RES_MIGRATING);

    atomic_inc(&res->asts_reserved);
}

/*
 * used to drop the reserved ast, either because it went unused,
 * or because the ast/bast was actually called.
 *
 * also, if there is a pending migration on this lockres,
 * and this was the last pending ast on the lockres,
 * atomically set the MIGRATING flag before we drop the lock.
 * this is how we ensure that migration can proceed with no
 * asts in progress.  note that it is ok if the state of the
 * queues is such that a lock should be granted in the future
 * or that a bast should be fired, because the new master will
 * shuffle the lists on this lockres as soon as it is migrated.
 */
void dlm_lockres_release_ast(struct dlm_ctxt *dlm,
                 struct dlm_lock_resource *res)
{
    if (!atomic_dec_and_lock(&res->asts_reserved, &res->spinlock))
        return;

    if (!res->migration_pending) {
        spin_unlock(&res->spinlock);
        return;
    }

    BUG_ON(res->state & DLM_LOCK_RES_MIGRATING);
    res->migration_pending = 0;
    res->state |= DLM_LOCK_RES_MIGRATING;
    spin_unlock(&res->spinlock);
    wake_up(&res->wq);
    wake_up(&dlm->migration_wq);
}

void dlm_force_free_mles(struct dlm_ctxt *dlm)
{
    int i;
    struct hlist_head *bucket;
    struct dlm_master_list_entry *mle;
    struct hlist_node *tmp, *list;

    /*
     * We notified all other nodes that we are exiting the domain and
     * marked the dlm state to DLM_CTXT_LEAVING. If any mles are still
     * around we force free them and wake any processes that are waiting
     * on the mles
     */
    spin_lock(&dlm->spinlock);
    spin_lock(&dlm->master_lock);

    BUG_ON(dlm->dlm_state != DLM_CTXT_LEAVING);
    BUG_ON((find_next_bit(dlm->domain_map, O2NM_MAX_NODES, 0) < O2NM_MAX_NODES));

    for (i = 0; i < DLM_HASH_BUCKETS; i++) {
        bucket = dlm_master_hash(dlm, i);
        hlist_for_each_safe(list, tmp, bucket) {
            mle = hlist_entry(list, struct dlm_master_list_entry,
                      master_hash_node);
            if (mle->type != DLM_MLE_BLOCK) {
                mlog(ML_ERROR, "bad mle: %p\n", mle);
                dlm_print_one_mle(mle);
            }
            atomic_set(&mle->woken, 1);
            wake_up(&mle->wq);

            __dlm_unlink_mle(dlm, mle);
            __dlm_mle_detach_hb_events(dlm, mle);
            __dlm_put_mle(mle);
        }
    }
    spin_unlock(&dlm->master_lock);
    spin_unlock(&dlm->spinlock);
}