/* -*- 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
  ", 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!
  ", 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!
  ", 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;
  
  	mlog_entry_void();
  
  	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
  ", 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
  ", 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
  ",
  		     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]
  ",
  		     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_grab_inflight_ref(struct dlm_ctxt *dlm,
  				   struct dlm_lock_resource *res,
  				   int new_lockres,
  				   const char *file,
  				   int line)
  {
  	if (!new_lockres)
  		assert_spin_locked(&res->spinlock);
  
  	if (!test_bit(dlm->node_num, res->refmap)) {
  		BUG_ON(res->inflight_locks != 0);
  		dlm_lockres_set_refmap_bit(dlm->node_num, res);
  	}
  	res->inflight_locks++;
  	mlog(0, "%s:%.*s: inflight++: now %u
  ",
  	     dlm->name, res->lockname.len, res->lockname.name,
  	     res->inflight_locks);
  }
  
  void __dlm_lockres_drop_inflight_ref(struct dlm_ctxt *dlm,
  				   struct dlm_lock_resource *res,
  				   const char *file,
  				   int line)
  {
  	assert_spin_locked(&res->spinlock);
  
  	BUG_ON(res->inflight_locks == 0);
  	res->inflight_locks--;
  	mlog(0, "%s:%.*s: inflight--: now %u
  ",
  	     dlm->name, res->lockname.len, res->lockname.name,
  	     res->inflight_locks);
  	if (res->inflight_locks == 0)
  		dlm_lockres_clear_refmap_bit(dlm->node_num, res);
  	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;

  	int drop_inflight_if_nonlocal = 0;

  
  	BUG_ON(!lockid);

  	hash = dlm_lockid_hash(lockid, namelen);

  
  	mlog(0, "get lockres %s (len %d)
  ", lockid, namelen);
  
  lookup:
  	spin_lock(&dlm->spinlock);

  	tmpres = __dlm_lookup_lockres_full(dlm, lockid, namelen, hash);

  	if (tmpres) {

  		int dropping_ref = 0;

  		spin_unlock(&dlm->spinlock);

  		spin_lock(&tmpres->spinlock);

  		/* We wait for the other 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);
  		}

  		if (tmpres->owner == dlm->node_num) {
  			BUG_ON(tmpres->state & DLM_LOCK_RES_DROPPING_REF);
  			dlm_lockres_grab_inflight_ref(dlm, tmpres);
  		} else if (tmpres->state & DLM_LOCK_RES_DROPPING_REF)
  			dropping_ref = 1;
  		spin_unlock(&tmpres->spinlock);

  
  		/* wait until done messaging the master, drop our ref to allow
  		 * the lockres to be purged, start over. */
  		if (dropping_ref) {
  			spin_lock(&tmpres->spinlock);
  			__dlm_wait_on_lockres_flags(tmpres, DLM_LOCK_RES_DROPPING_REF);
  			spin_unlock(&tmpres->spinlock);
  			dlm_lockres_put(tmpres);
  			tmpres = NULL;
  			goto lookup;
  		}

  		mlog(0, "found in hash!
  ");
  		if (res)
  			dlm_lockres_put(res);
  		res = tmpres;
  		goto leave;
  	}
  
  	if (!res) {
  		spin_unlock(&dlm->spinlock);
  		mlog(0, "allocating a new resource
  ");
  		/* 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
  ", 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!
  ");
  			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
  ",
  			     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 cant 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(ML_NOTICE, "%s:%.*s: at least one node (%d) to "

  			     "recover before lock mastery can begin
  ",
  			     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);

  	/* since this lockres is new it doesnt not require the spinlock */
  	dlm_lockres_grab_inflight_ref_new(dlm, res);
  
  	/* if this node does not become the master make sure to drop
  	 * this inflight reference below */
  	drop_inflight_if_nonlocal = 1;

  	/* 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(ML_NOTICE, "%s: recovery map is not empty, but "
  			     "must master $RECOVERY lock now
  ", dlm->name);
  			if (!dlm_pre_master_reco_lockres(dlm, res))
  				wait_on_recovery = 0;
  			else {
  				mlog(0, "%s: waiting 500ms for heartbeat state "
  				    "change
  ", 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(ML_NOTICE, "%s:%.*s: at least one node (%d) to "

  			     "recover before lock mastery can begin
  ",
  			     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:%.*s: requests only up to %u but master "
  			     "is %u, keep going
  ", 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:%.*s: node map changed, redo the "
  		     "master request now, blocked=%d
  ",
  		     dlm->name, res->lockname.len,
  		     res->lockname.name, blocked);
  		if (++tries > 20) {
  			mlog(ML_ERROR, "%s:%.*s: spinning on "

  			     "dlm_wait_for_lock_mastery, blocked=%d
  ",
  			     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, "lockres mastered by %u
  ", 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);

  	if (res->owner != dlm->node_num && drop_inflight_if_nonlocal)
  		dlm_lockres_drop_inflight_ref(dlm, res);

  	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
  ", 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
  ", 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
  ",
  		     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
  ",

  			     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
  ", 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
  ", 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
  ", 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
  ", dlm->name,
  			     res->lockname.len, res->lockname.name);

  			goto recheck;
  		}
  		mlog(0, "done waiting, master is %u
  ", res->owner);
  		ret = 0;
  		goto leave;
  	}
  
  	ret = 0;   /* done */
  	if (assert) {
  		m = dlm->node_num;
  		mlog(0, "about to master %.*s here, this=%u
  ",
  		     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!
  ");
  
  	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
  ", node);

  
  			/* redo the master request, but only for the new node */
  			mlog(0, "sending request to new node
  ");
  			clear_bit(node, mle->response_map);
  			set_bit(node, mle->vote_map);
  		} else {
  			mlog(ML_ERROR, "node down! %d
  ", 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!
  ", 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
  ", 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
  ",
  						     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!
  ");
  			BUG();
  		} else if (ret == -EINVAL) {
  			mlog(ML_ERROR, "bad args passed to o2net!
  ");
  			BUG();
  		} else if (ret == -ENOMEM) {
  			mlog(ML_ERROR, "out of memory while trying to send "
  			     "network message!  retrying
  ");
  			/* 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!
  ", 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
  ", to);

  			mlog(0, "%s:%.*s: master node %u now knows I have a "
  			     "reference
  ", 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
  ", to);
  			set_bit(to, mle->response_map);
  			break;
  		case DLM_MASTER_RESP_MAYBE:
  			mlog(0, "node %u not master, response=MAYBE
  ", 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
  ", to);
  			resend = 1;
  			response = 0;
  			break;
  		default:
  			mlog(ML_ERROR, "bad response! %u
  ", 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
  ");

  			response = DLM_MASTER_RESP_ERROR;
  			if (mle)
  				kmem_cache_free(dlm_mle_cache, mle);
  			goto send_response;
  		}
  
  		if (res->owner == dlm->node_num) {

  			mlog(0, "%s:%.*s: setting bit %u in refmap
  ",
  			     dlm->name, namelen, name, request->node_idx);
  			dlm_lockres_set_refmap_bit(request->node_idx, res);

  			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
  ", 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!
  ");
  			BUG();
  		}
  
  		// mlog(0, "lockres is in progress...
  ");
  		spin_lock(&dlm->master_lock);
  		found = dlm_find_mle(dlm, &tmpmle, name, namelen);
  		if (!found) {
  			mlog(ML_ERROR, "no mle found for this lock!
  ");
  			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
  ");
  			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.
  ", 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?!
  ",
  				     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(request->node_idx, res);
  				mlog(0, "%s:%.*s: setting bit %u in refmap
  ",
  				     dlm->name, namelen, name,
  				     request->node_idx);

  			} else

  				response = DLM_MASTER_RESP_NO;
  		} else {
  			// mlog(0, "this node is attempting to "
  			// "master lockres
  ");
  			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
  ");
  		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.
  ");

  		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
  ");
  		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!
  ");
  			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)
  ",
  			     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
  ", response);
  		if (!res) {
  			mlog(ML_ERROR, "bad lockres while trying to assert!
  ");
  			BUG();
  		}
  		mlog(0, "%u is the owner of %.*s, cleaning everyone else
  ",
  			     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
  ");
  			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)
  ", 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
  ", tmpret,
  			     DLM_ASSERT_MASTER_MSG, dlm->key, to);

  			if (!dlm_is_host_down(tmpret)) {

  				mlog(ML_ERROR, "unhandled error=%d!
  ", tmpret);

  				BUG();
  			}
  			/* a node died.  finish out the rest of the nodes. */

  			mlog(0, "link to %d went down!
  ", 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.
  ", 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
  ",
  				     namelen, lockname, to);
  		}
  
  		if (r & DLM_ASSERT_RESPONSE_REASSERT) {

  			mlog(0, "%.*s: node %u create mles on other "

  			     "nodes and requests a re-assert
  ",

  			     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
  ",
  			     namelen, lockname, to);
  			spin_lock(&res->spinlock);
  			dlm_lockres_set_refmap_bit(to, res);
  			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
  ", 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)
  ", 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)
  ", 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
  ", 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.
  ", 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
  ",
  				     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
  ",
  				     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!
  ", 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)
  ",
  				     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
  ", assert->node_idx,
  					     namelen, name);
  					goto ok;
  				}
  				mlog(ML_ERROR, "got assert_master from "
  				     "node %u, but %u is the owner! "
  				     "(%.*s)
  ", 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)
  ",
  				     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)
  ",
  				     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!
  ",
  	// 	     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
  ",
  			       		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
  ", 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
  ", 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
  ");

  		/* 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!
  ",
  			     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
  ",
  		     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.
  ");
  	__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
  ", 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.
  ");
  		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
  ",
  		     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
  ");
  }

  /* 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.
  ", dlm->name,
  				     nodenum, master);
  				ret = -EAGAIN;
  			}
  			spin_unlock(&dlm->spinlock);

  			mlog(0, "%s: reco lock master is %u
  ", 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);
  
  	mlog(0, "%s:%.*s: sending deref to %d
  ",
  	     dlm->name, namelen, lockname, res->owner);
  	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, "Error %d when sending message %u (key 0x%x) to "
  		     "node %u
  ", ret, DLM_DEREF_LOCKRES_MSG, dlm->key,
  		     res->owner);

  	else if (r < 0) {
  		/* BAD.  other node says I did not have a ref. */
  		mlog(ML_ERROR,"while dropping ref on %s:%.*s "
  		    "(master=%u) got %d.
  ", 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
  ", 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
  ",
  		     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(node, res);
  			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!
  ", 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(node, res);
  		cleared = 1;
  	}
  	spin_unlock(&res->spinlock);
  
  	if (cleared) {
  		mlog(0, "%s:%.*s node %u ref dropped in dispatch
  ",
  		     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!
  ", dlm->name,
  		     res->lockname.len, res->lockname.name, node);

  		dlm_print_one_lock_resource(res);

  	}
  
  	dlm_lockres_put(res);
  }

  /* Checks whether the lockres can be migrated. Returns 0 if yes, < 0
   * if not. If 0, numlocks is set to the number of locks in the lockres.
   */
  static int dlm_is_lockres_migrateable(struct dlm_ctxt *dlm,
  				      struct dlm_lock_resource *res,
  				      int *numlocks)
  {
  	int ret;
  	int i;
  	int count = 0;

  	struct list_head *queue;

  	struct dlm_lock *lock;
  
  	assert_spin_locked(&res->spinlock);
  
  	ret = -EINVAL;
  	if (res->owner == DLM_LOCK_RES_OWNER_UNKNOWN) {
  		mlog(0, "cannot migrate lockres with unknown owner!
  ");
  		goto leave;
  	}
  
  	if (res->owner != dlm->node_num) {
  		mlog(0, "cannot migrate lockres this node doesn't own!
  ");
  		goto leave;
  	}
  
  	ret = 0;
  	queue = &res->granted;
  	for (i = 0; i < 3; i++) {

  		list_for_each_entry(lock, queue, list) {

  			++count;
  			if (lock->ml.node == dlm->node_num) {
  				mlog(0, "found a lock owned by this node still "
  				     "on the %s queue!  will not migrate this "
  				     "lockres
  ", (i == 0 ? "granted" :
  						   (i == 1 ? "converting" :
  						    "blocked")));
  				ret = -ENOTEMPTY;
  				goto leave;
  			}
  		}
  		queue++;
  	}
  
  	*numlocks = count;
  	mlog(0, "migrateable lockres having %d locks
  ", *numlocks);
  
  leave:
  	return ret;
  }

  
  /*
   * 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 numlocks;
  	int wake = 0;

  
  	if (!dlm_grab(dlm))
  		return -EINVAL;
  
  	name = res->lockname.name;
  	namelen = res->lockname.len;
  
  	mlog(0, "migrating %.*s to %u
  ", namelen, name, target);
  
  	/*
  	 * ensure this lockres is a proper candidate for migration
  	 */
  	spin_lock(&res->spinlock);

  	ret = dlm_is_lockres_migrateable(dlm, res, &numlocks);
  	if (ret < 0) {

  		spin_unlock(&res->spinlock);
  		goto leave;
  	}

  	spin_unlock(&res->spinlock);
  
  	/* no work to do */

  	if (numlocks == 0) {

  		mlog(0, "no locks were found on this lockres! done!
  ");

  		goto leave;
  	}
  
  	/*
  	 * 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;
  
  	/*
  	 * find a node to migrate the lockres to
  	 */
  
  	mlog(0, "picking a migration node
  ");
  	spin_lock(&dlm->spinlock);
  	/* pick a new node */
  	if (!test_bit(target, dlm->domain_map) ||
  	    target >= O2NM_MAX_NODES) {
  		target = dlm_pick_migration_target(dlm, res);
  	}
  	mlog(0, "node %u chosen for migration
  ", target);
  
  	if (target >= O2NM_MAX_NODES ||
  	    !test_bit(target, dlm->domain_map)) {
  		/* target chosen is not alive */
  		ret = -EINVAL;
  	}
  
  	if (ret) {
  		spin_unlock(&dlm->spinlock);
  		goto fail;
  	}
  
  	mlog(0, "continuing with target = %u
  ", target);
  
  	/*
  	 * clear any existing master requests and
  	 * add the migration mle to the list
  	 */
  	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
  ");
  		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.
  ", 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);
  		}
  		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
  ",
  		     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);

  		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
  ",
  			     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
  ",

  				     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
  ",
  			     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);

  	/* TODO: cleanup */
  	if (mres)
  		free_page((unsigned long)mres);
  
  	dlm_put(dlm);
  
  	mlog(0, "returning %d
  ", 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;

  	int numlocks;

  	spin_lock(&res->spinlock);

  	if (res->owner != dlm->node_num) {
  		if (!__dlm_lockres_unused(res)) {
  			mlog(ML_ERROR, "%s:%.*s: this node is not master, "
  			     "trying to free this but locks remain
  ",
  			     dlm->name, res->lockname.len, res->lockname.name);
  		}

  		spin_unlock(&res->spinlock);

  		goto leave;
  	}

  
  	/* No need to migrate a lockres having no locks */
  	ret = dlm_is_lockres_migrateable(dlm, res, &numlocks);
  	if (ret >= 0 && numlocks == 0) {
  		spin_unlock(&res->spinlock);
  		goto leave;
  	}

  	spin_unlock(&res->spinlock);

  
  	/* Wheee! Migrate lockres here! Will sleep so drop spinlock. */
  	spin_unlock(&dlm->spinlock);
  	lock_dropped = 1;
  	while (1) {
  		ret = dlm_migrate_lockres(dlm, res, O2NM_MAX_NODES);
  		if (ret >= 0)
  			break;
  		if (ret == -ENOTEMPTY) {
  			mlog(ML_ERROR, "lockres %.*s still has local locks!
  ",
  		     		res->lockname.len, res->lockname.name);
  			BUG();
  		}
  
  		mlog(0, "lockres %.*s: migrate failed, "
  		     "retrying
  ", res->lockname.len,
  		     res->lockname.name);
  		msleep(DLM_MIGRATION_RETRY_MS);
  	}
  	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
  ",
  	       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
  ",
  	       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
  ",
  		       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
  ",
  		       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...
  ");
  		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
  ",
  		     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
  ",
  				     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(lock->ml.node, res);

  				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
  ", dlm->name,
  			     res->lockname.len, res->lockname.name, bit);
  			dlm_lockres_clear_refmap_bit(bit, res);
  		}
  		bit++;
  	}

  }
  
  /* for now this is not too intelligent.  we will
   * need stats to make this do the right thing.
   * this just finds the first lock on one of the
   * queues and uses that node as the target. */
  static u8 dlm_pick_migration_target(struct dlm_ctxt *dlm,
  				    struct dlm_lock_resource *res)
  {
  	int i;
  	struct list_head *queue = &res->granted;

  	struct dlm_lock *lock;
  	int nodenum;
  
  	assert_spin_locked(&dlm->spinlock);
  
  	spin_lock(&res->spinlock);
  	for (i=0; i<3; i++) {

  		list_for_each_entry(lock, queue, list) {

  			/* up to the caller to make sure this node
  			 * is alive */

  			if (lock->ml.node != dlm->node_num) {
  				spin_unlock(&res->spinlock);
  				return lock->ml.node;
  			}
  		}
  		queue++;
  	}
  	spin_unlock(&res->spinlock);
  	mlog(0, "have not found a suitable target yet! checking domain map
  ");
  
  	/* ok now we're getting desperate.  pick anyone alive. */
  	nodenum = -1;
  	while (1) {
  		nodenum = find_next_bit(dlm->domain_map,
  					O2NM_MAX_NODES, nodenum+1);
  		mlog(0, "found %d in domain map
  ", nodenum);
  		if (nodenum >= O2NM_MAX_NODES)
  			break;
  		if (nodenum != dlm->node_num) {
  			mlog(0, "picking %d
  ", nodenum);
  			return nodenum;
  		}
  	}
  
  	mlog(0, "giving up.  no master to migrate to
  ");
  	return DLM_LOCK_RES_OWNER_UNKNOWN;
  }
  
  
  
  /* 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, "Error %d when sending message %u (key "
  			     "0x%x) to node %u
  ", ret, DLM_MIGRATE_REQUEST_MSG,
  			     dlm->key, nodenum);

  			if (!dlm_is_host_down(ret)) {
  				mlog(ML_ERROR, "unhandled error=%d!
  ", ret);
  				BUG();
  			}
  			clear_bit(nodenum, iter->node_map);
  			ret = 0;
  		} else if (status < 0) {

  			mlog(0, "migrate request (node %u) returned %d!
  ",
  			     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
  ",
  			     dlm->name, res->lockname.len, res->lockname.name,
  			     nodenum);
  			spin_lock(&res->spinlock);
  			dlm_lockres_set_refmap_bit(nodenum, res);
  			spin_unlock(&res->spinlock);

  		}
  	}
  
  	if (ret < 0)
  		mlog_errno(ret);
  
  	mlog(0, "returning ret=%d
  ", 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;
  
  	mlog_entry_void();
  
  	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
  ",
  				     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
  ",
  				     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
  ", 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
  ", 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
  ", 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_entry("dlm=%s, dead node=%u
  ", 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!
  ", 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(old_master, res);
  	spin_unlock(&res->spinlock);

  	mlog(0, "now time to do a migrate request to other nodes
  ");
  	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
  ",
  	     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
  ",
  	     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.
  ", 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
  ", 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);
  }