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dlmmaster.c

/* -*- 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/utsname.h>
#include <linux/init.h>
#include <linux/sysctl.h>
#include <linux/random.h>
#include <linux/blkdev.h>
#include <linux/socket.h>
#include <linux/inet.h>
#include <linux/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"

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

enum dlm_mle_type {
      DLM_MLE_BLOCK,
      DLM_MLE_MASTER,
      DLM_MLE_MIGRATION
};

struct dlm_lock_name
{
      u8 len;
      u8 name[DLM_LOCKID_NAME_MAX];
};

struct dlm_master_list_entry
{
      struct list_head list;
      struct list_head hb_events;
      struct dlm_ctxt *dlm;
      spinlock_t spinlock;
      wait_queue_head_t wq;
      atomic_t woken;
      struct kref mle_refs;
      int inuse;
      unsigned long maybe_map[BITS_TO_LONGS(O2NM_MAX_NODES)];
      unsigned long vote_map[BITS_TO_LONGS(O2NM_MAX_NODES)];
      unsigned long response_map[BITS_TO_LONGS(O2NM_MAX_NODES)];
      unsigned long node_map[BITS_TO_LONGS(O2NM_MAX_NODES)];
      u8 master;
      u8 new_master;
      enum dlm_mle_type type;
      struct o2hb_callback_func mle_hb_up;
      struct o2hb_callback_func mle_hb_down;
      union {
            struct dlm_lock_resource *res;
            struct dlm_lock_name name;
      } u;
};

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)
{
      struct dlm_lock_resource *res;

      if (dlm != mle->dlm)
            return 0;

      if (mle->type == DLM_MLE_BLOCK ||
          mle->type == DLM_MLE_MIGRATION) {
            if (namelen != mle->u.name.len ||
                memcmp(name, mle->u.name.name, namelen)!=0)
                  return 0;
      } else {
            res = mle->u.res;
            if (namelen != res->lockname.len ||
                memcmp(res->lockname.name, name, namelen) != 0)
                  return 0;
      }
      return 1;
}

#define dlm_print_nodemap(m)  _dlm_print_nodemap(m,#m)
static void _dlm_print_nodemap(unsigned long *map, const char *mapname)
{
      int i;
      printk("%s=[ ", mapname);
      for (i=0; i<O2NM_MAX_NODES; i++)
            if (test_bit(i, map))
                  printk("%d ", i);
      printk("]");
}

static void dlm_print_one_mle(struct dlm_master_list_entry *mle)
{
      int refs;
      char *type;
      char attached;
      u8 master;
      unsigned int namelen;
      const char *name;
      struct kref *k;
      unsigned long *maybe = mle->maybe_map,
                  *vote = mle->vote_map,
                  *resp = mle->response_map,
                  *node = mle->node_map;

      k = &mle->mle_refs;
      if (mle->type == DLM_MLE_BLOCK)
            type = "BLK";
      else if (mle->type == DLM_MLE_MASTER)
            type = "MAS";
      else
            type = "MIG";
      refs = atomic_read(&k->refcount);
      master = mle->master;
      attached = (list_empty(&mle->hb_events) ? 'N' : 'Y');

      if (mle->type != DLM_MLE_MASTER) {
            namelen = mle->u.name.len;
            name = mle->u.name.name;
      } else {
            namelen = mle->u.res->lockname.len;
            name = mle->u.res->lockname.name;
      }

      mlog(ML_NOTICE, "%.*s: %3s refs=%3d mas=%3u new=%3u evt=%c inuse=%d ",
              namelen, name, type, refs, master, mle->new_master, attached,
              mle->inuse);
      dlm_print_nodemap(maybe);
      printk(", ");
      dlm_print_nodemap(vote);
      printk(", ");
      dlm_print_nodemap(resp);
      printk(", ");
      dlm_print_nodemap(node);
      printk(", ");
      printk("\n");
}

#if 0
/* Code here is included but defined out as it aids debugging */

static void dlm_dump_mles(struct dlm_ctxt *dlm)
{
      struct dlm_master_list_entry *mle;
      
      mlog(ML_NOTICE, "dumping all mles for domain %s:\n", dlm->name);
      spin_lock(&dlm->master_lock);
      list_for_each_entry(mle, &dlm->master_list, list)
            dlm_print_one_mle(mle);
      spin_unlock(&dlm->master_lock);
}

int dlm_dump_all_mles(const char __user *data, unsigned int len)
{
      struct dlm_ctxt *dlm;

      spin_lock(&dlm_domain_lock);
      list_for_each_entry(dlm, &dlm_domains, list) {
            mlog(ML_NOTICE, "found dlm: %p, name=%s\n", dlm, dlm->name);
            dlm_dump_mles(dlm);
      }
      spin_unlock(&dlm_domain_lock);
      return len;
}
EXPORT_SYMBOL_GPL(dlm_dump_all_mles);

#endif  /*  0  */


static struct kmem_cache *dlm_mle_cache = NULL;


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

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


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

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


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


/*
 * MASTER LIST FUNCTIONS
 */


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

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


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


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

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

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

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

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

}

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

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


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

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

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

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

      mle->dlm = dlm;
      mle->type = type;
      INIT_LIST_HEAD(&mle->list);
      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;

      if (mle->type == DLM_MLE_MASTER) {
            BUG_ON(!res);
            mle->u.res = res;
      } else if (mle->type == DLM_MLE_BLOCK) {
            BUG_ON(!name);
            memcpy(mle->u.name.name, name, namelen);
            mle->u.name.len = namelen;
      } else /* DLM_MLE_MIGRATION */ {
            BUG_ON(!name);
            memcpy(mle->u.name.name, name, namelen);
            mle->u.name.len = namelen;
      }

      /* 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);
}


/* 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;

      assert_spin_locked(&dlm->master_lock);

      list_for_each_entry(tmpmle, &dlm->master_list, list) {
            if (!dlm_mle_equal(dlm, tmpmle, name, namelen))
                  continue;
            dlm_get_mle(tmpmle);
            *mle = tmpmle;
            return 1;
      }
      return 0;
}

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

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

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

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

      spin_unlock(&mle->spinlock);
}

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

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

      spin_unlock(&mle->spinlock);
}


int dlm_init_mle_cache(void)
{
      dlm_mle_cache = kmem_cache_create("dlm_mle_cache",
                                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;

      if (mle->type != DLM_MLE_MASTER) {
            mlog(0, "calling mle_release for %.*s, type %d\n",
                 mle->u.name.len, mle->u.name.name, mle->type);
      } else {
            mlog(0, "calling mle_release for %.*s, type %d\n",
                 mle->u.res->lockname.len,
                 mle->u.res->lockname.name, mle->type);
      }
      assert_spin_locked(&dlm->spinlock);
      assert_spin_locked(&dlm->master_lock);

      /* remove from list if not already */
      if (!list_empty(&mle->list))
            list_del_init(&mle->list);

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

      /* 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
 */

static void dlm_set_lockres_owner(struct dlm_ctxt *dlm,
                          struct dlm_lock_resource *res,
                          u8 owner)
{
      assert_spin_locked(&res->spinlock);

      mlog_entry("%.*s, %u\n", res->lockname.len, res->lockname.name, owner);

      if (owner == dlm->node_num)
            atomic_inc(&dlm->local_resources);
      else if (owner == DLM_LOCK_RES_OWNER_UNKNOWN)
            atomic_inc(&dlm->unknown_resources);
      else
            atomic_inc(&dlm->remote_resources);

      res->owner = owner;
}

void dlm_change_lockres_owner(struct dlm_ctxt *dlm,
                        struct dlm_lock_resource *res, u8 owner)
{
      assert_spin_locked(&res->spinlock);

      if (owner == res->owner)
            return;

      if (res->owner == dlm->node_num)
            atomic_dec(&dlm->local_resources);
      else if (res->owner == DLM_LOCK_RES_OWNER_UNKNOWN)
            atomic_dec(&dlm->unknown_resources);
      else
            atomic_dec(&dlm->remote_resources);

      dlm_set_lockres_owner(dlm, res, owner);
}


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

      res = container_of(kref, struct dlm_lock_resource, refs);

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

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

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

            dlm_print_one_lock_resource(res);
      }

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

      kfree(res->lockname.name);

      kfree(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);
      atomic_set(&res->asts_reserved, 0);
      res->migration_pending = 0;
      res->inflight_locks = 0;

      kref_init(&res->refs);

      /* 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;

      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;

      res = kmalloc(sizeof(struct dlm_lock_resource), GFP_NOFS);
      if (!res)
            return NULL;

      res->lockname.name = kmalloc(namelen, GFP_NOFS);
      if (!res->lockname.name) {
            kfree(res);
            return NULL;
      }

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

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\n",
           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\n",
           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)\n", lockid, namelen);

lookup:
      spin_lock(&dlm->spinlock);
      tmpres = __dlm_lookup_lockres_full(dlm, lockid, namelen, hash);
      if (tmpres) {
            int dropping_ref = 0;

            spin_lock(&tmpres->spinlock);
            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);
            spin_unlock(&dlm->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!\n");
            if (res)
                  dlm_lockres_put(res);
            res = tmpres;
            goto leave;
      }

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

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

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

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

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

                  /* master is known, detach */
                  if (!mig)
                        dlm_mle_detach_hb_events(dlm, mle);
                  dlm_put_mle(mle);
                  mle = NULL;
                  /* this is lame, but we 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);
            list_add(&mle->list, &dlm->master_list);

            /* 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\n",
                       dlm->name, namelen, (char *)lockid, bit);
                  wait_on_recovery = 1;
            }
      }

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

      /* finally add the lockres to its hash bucket */
      __dlm_insert_lockres(dlm, res);
      /* 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\n", dlm->name);
                  if (!dlm_pre_master_reco_lockres(dlm, res))
                        wait_on_recovery = 0;
                  else {
                        mlog(0, "%s: waiting 500ms for heartbeat state "
                            "change\n", dlm->name);
                        msleep(500);
                  }
                  continue;
            } 

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

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

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

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

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

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

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

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

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

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

      spin_unlock(&mle->spinlock);

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

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

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

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

leave:
      return ret;
}

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

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

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

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

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

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

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

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

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

      iter->curnode = bit;
      return bit;
}


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

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

      assert_spin_locked(&mle->spinlock);

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

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

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

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

      if (mle->type != DLM_MLE_MASTER) {
            request.namelen = mle->u.name.len;
            memcpy(request.name, mle->u.name.name, request.namelen);
      } else {
            request.namelen = mle->u.res->lockname.len;
            memcpy(request.name, mle->u.res->lockname.name,
                  request.namelen);
      }

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

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

out:
      return ret;
}

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

      if (!dlm_grab(dlm))
            return DLM_MASTER_RESP_NO;

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

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

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

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

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

            if (res->owner == dlm->node_num) {
                  mlog(0, "%s:%.*s: setting bit %u in refmap\n",
                       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\n", res->owner);
                  response = DLM_MASTER_RESP_NO;
                  if (mle)
                        kmem_cache_free(dlm_mle_cache, mle);
                  goto send_response;
            }

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

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

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

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

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

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

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

      if (found) {
            /* keep the mle attached to heartbeat events */
            dlm_put_mle(tmpmle);
      }
send_response:

      if (dispatch_assert) {
            if (response != DLM_MASTER_RESP_YES)
                  mlog(ML_ERROR, "invalid response %d\n", response);
            if (!res) {
                  mlog(ML_ERROR, "bad lockres while trying to assert!\n");
                  BUG();
            }
            mlog(0, "%u is the owner of %.*s, cleaning everyone else\n",
                       dlm->node_num, res->lockname.len, res->lockname.name);
            ret = dlm_dispatch_assert_master(dlm, res, 0, request->node_idx, 
                                     DLM_ASSERT_MASTER_MLE_CLEANUP);
            if (ret < 0) {
                  mlog(ML_ERROR, "failed to dispatch assert master work\n");
                  response = DLM_MASTER_RESP_ERROR;
            }
      }

      dlm_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...
 */
int dlm_do_assert_master(struct dlm_ctxt *dlm,
                   struct dlm_lock_resource *res,
                   void *nodemap, u32 flags)
{
      struct dlm_assert_master assert;
      int to, tmpret;
      struct dlm_node_iter iter;
      int ret = 0;
      int reassert;
      const char *lockname = res->lockname.name;
      unsigned int namelen = res->lockname.len;

      BUG_ON(namelen > O2NM_MAX_NAME_LEN);

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

again:
      reassert = 0;

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

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

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

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

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

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

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

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

      // mlog(0, "woo!  got an assert_master from node %u!\n",
      //         assert->node_idx);
      if (mle) {
            int extra_ref = 0;
            int nn = -1;
            int rr, err = 0;
            
            spin_lock(&mle->spinlock);
            if (mle->type == DLM_MLE_BLOCK || mle->type == DLM_MLE_MIGRATION)
                  extra_ref = 1;
            else {
                  /* MASTER mle: if any bits set in the response map
                   * then the calling node needs to re-assert to clear
                   * up nodes that this node contacted */
                  while ((nn = find_next_bit (mle->response_map, O2NM_MAX_NODES, 
                                        nn+1)) < O2NM_MAX_NODES) {
                        if (nn != dlm->node_num && nn != assert->node_idx)
                              master_request = 1;
                  }
            }
            mle->master = assert->node_idx;
            atomic_set(&mle->woken, 1);
            wake_up(&mle->wq);
            spin_unlock(&mle->spinlock);

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

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

            rr = atomic_read(&mle->mle_refs.refcount);
            if (mle->inuse > 0) {
                  if (extra_ref && rr < 3)
                        err = 1;
                  else if (!extra_ref && rr < 2)
                        err = 1;
            } else {
                  if (extra_ref && rr < 2)
                        err = 1;
                  else if (!extra_ref && rr < 1)
                        err = 1;
            }
            if (err) {
                  mlog(ML_ERROR, "%s:%.*s: got assert master from %u "
                       "that will mess up this node, refs=%d, extra=%d, "
                       "inuse=%d\n", dlm->name, namelen, name,
                       assert->node_idx, rr, extra_ref, mle->inuse);
                  dlm_print_one_mle(mle);
            }
            list_del_init(&mle->list);
            __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);
            spin_unlock(&dlm->spinlock);
      } else if (res) {
            if (res->owner != assert->node_idx) {
                  mlog(0, "assert_master from %u, but current "
                       "owner is %u (%.*s), no mle\n", assert->node_idx,
                       res->owner, namelen, name);
            }
      }

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

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

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

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

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


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

      if (ignore_higher) 
            mlog(0, "IGNORE HIGHER: %.*s\n", res->lockname.len, 
                 res->lockname.name);
            
      spin_lock(&dlm->work_lock);
      list_add_tail(&item->list, &dlm->work_list);
      spin_unlock(&dlm->work_lock);

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

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

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

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

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

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

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

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

put:
      dlm_lockres_put(res);

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

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

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

      while ((nodenum = dlm_node_iter_next(&iter)) >= 0) {
            /* do not send to self */
            if (nodenum == dlm->node_num)
                  continue;
            ret = dlm_do_master_requery(dlm, res, nodenum, &master);
            if (ret < 0) {
                  mlog_errno(ret);
                  if (!dlm_is_host_down(ret))
                        BUG();
                  /* host is down, so answer for that node would be
                   * DLM_LOCK_RES_OWNER_UNKNOWN.  continue. */
                  ret = 0;
            }

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

/*
 * DLM_DEREF_LOCKRES_MSG
 */

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

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

      mlog(0, "%s:%.*s: sending deref to %d\n",
           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_errno(ret);
      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.\n", dlm->name, namelen,
                lockname, res->owner, r);
            dlm_print_one_lock_resource(res);
            BUG();
      }
      return ret;
}

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

      if (!dlm_grab(dlm))
            return 0;

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

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

      hash = dlm_lockid_hash(name, namelen);

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

      spin_lock(&res->spinlock);
      if (res->state & DLM_LOCK_RES_SETREF_INPROG)
            dispatch = 1;
      else {
            BUG_ON(res->state & DLM_LOCK_RES_DROPPING_REF);
            if (test_bit(node, res->refmap)) {
                  dlm_lockres_clear_refmap_bit(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!\n", dlm->name,
                  res->lockname.len, res->lockname.name, node);
                  __dlm_print_one_lock_resource(res);
            }
            ret = 0;
            goto done;
      }

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

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

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

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

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

      return ret;
}

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

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

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

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

      dlm_lockres_put(res);
}

/* 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!\n");
            goto leave;
      }

      if (res->owner != dlm->node_num) {
            mlog(0, "cannot migrate lockres this node doesn't own!\n");
            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\n", (i == 0 ? "granted" :
                                       (i == 1 ? "converting" :
                                        "blocked")));
                        ret = -ENOTEMPTY;
                        goto leave;
                  }
            }
            queue++;
      }

      *numlocks = count;
      mlog(0, "migrateable lockres having %d locks\n", *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\n", 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!\n");
            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 = (struct dlm_master_list_entry *) 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\n");
      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\n", 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\n", 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\n");
            goto fail;
      }
      mle_added = 1;

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

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

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

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

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

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

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

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


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

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

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

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

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

      dlm_lockres_calc_usage(dlm, res);

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

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

      /* TODO: cleanup */
      if (mres)
            free_page((unsigned long)mres);

      dlm_put(dlm);

      mlog(0, "returning %d\n", 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\n",
                       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!\n",
                        res->lockname.len, res->lockname.name);
                  BUG();
            }

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

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

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

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

      /*
       * at this point:
       *
       *   o the DLM_LOCK_RES_MIGRATING flag is set
       *   o there are no pending asts on this lockres
       *   o all processes trying to reserve an ast on this
       *     lockres must wait for the MIGRATING flag to clear
       */
      return ret;
}

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

      assert_spin_locked(&res->spinlock);

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

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

      /* 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\n", nodenum);
            if (nodenum >= O2NM_MAX_NODES)
                  break;
            if (nodenum != dlm->node_num) {
                  mlog(0, "picking %d\n", nodenum);
                  return nodenum;
            }
      }

      mlog(0, "giving up.  no master to migrate to\n");
      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, 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;

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

      if (ret < 0)
            mlog_errno(ret);

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


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

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

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

      /* preallocate.. if this fails, abort */
      mle = (struct dlm_master_list_entry *) 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);
      spin_lock(&dlm->master_lock);

      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);
      }

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

unlock:
      spin_unlock(&dlm->master_lock);
      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\n",
                             namelen, name);
                        ret = -EEXIST;
                  } else {
                        /* bad.  2 NODES are trying to migrate! */
                        mlog(ML_ERROR, "migration error  mle: "
                             "master=%u new_master=%u // request: "
                             "master=%u new_master=%u // "
                             "lockres=%.*s\n",
                             tmp->master, tmp->new_master,
                             master, new_master,
                             namelen, name);
                        BUG();
                  }
            } else {
                  /* this is essentially what assert_master does */
                  tmp->master = master;
                  atomic_set(&tmp->woken, 1);
                  wake_up(&tmp->wq);
                  /* remove it from the list so that only one
                   * mle will be found */
                  list_del_init(&tmp->list);
                  /* this was obviously WRONG.  mle is uninited here.  should be tmp. */
                  __dlm_mle_detach_hb_events(dlm, tmp);
                  ret = DLM_MIGRATE_RESPONSE_MASTERY_REF;
                  mlog(0, "%s:%.*s: master=%u, newmaster=%u, "
                      "telling master to get ref for cleared out mle "
                      "during migration\n", dlm->name, namelen, name,
                      master, new_master);
            }
            spin_unlock(&tmp->spinlock);
      }

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

      return ret;
}


void dlm_clean_master_list(struct dlm_ctxt *dlm, u8 dead_node)
{
      struct dlm_master_list_entry *mle, *next;
      struct dlm_lock_resource *res;
      unsigned int hash;

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

      /* clean the master list */
      spin_lock(&dlm->master_lock);
      list_for_each_entry_safe(mle, next, &dlm->master_list, list) {
            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) {
                  int bit;

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

            /* remove from the list early.  NOTE: unlinking
             * list_head while in list_for_each_safe */
            __dlm_mle_detach_hb_events(dlm, mle);
            spin_lock(&mle->spinlock);
            list_del_init(&mle->list);
            atomic_set(&mle->woken, 1);
            spin_unlock(&mle->spinlock);
            wake_up(&mle->wq);

            mlog(0, "%s: node %u died during migration from "
                 "%u to %u!\n", dlm->name, dead_node,
                 mle->master, mle->new_master);
            /* if there is a lockres associated with this
             * mle, find it and set its owner to UNKNOWN */
            hash = dlm_lockid_hash(mle->u.name.name, mle->u.name.len);
            res = __dlm_lookup_lockres(dlm, mle->u.name.name,
                                 mle->u.name.len, hash);
            if (res) {
                  /* unfortunately if we hit this rare case, our
                   * lock ordering is messed.  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. */
                  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);

                  /* 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\n");
      ret = dlm_do_migrate_request(dlm, res, old_master,
                             dlm->node_num, &iter);
      if (ret < 0) {
            mlog_errno(ret);
            goto leave;
      }

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

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

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

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

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

      atomic_inc(&res->asts_reserved);
}

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

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

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

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