OSCL-LXR linux-6.0.1/​fs/​ocfs2/​dlm/​dlmmaster.c	Source navigation Diff markup Identifier search General search
	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * dlmmod.c
  *
  * standalone DLM module
  *
  * Copyright (C) 2004 Oracle.  All rights reserved.
  */
 
 
 #include <linux/module.h>
 #include <linux/fs.h>
 #include <linux/types.h>
 #include <linux/slab.h>
 #include <linux/highmem.h>
 #include <linux/init.h>
 #include <linux/sysctl.h>
 #include <linux/random.h>
 #include <linux/blkdev.h>
 #include <linux/socket.h>
 #include <linux/inet.h>
 #include <linux/spinlock.h>
 #include <linux/delay.h>
 
 
 #include "../cluster/heartbeat.h"
 #include "../cluster/nodemanager.h"
 #include "../cluster/tcp.h"
 
 #include "dlmapi.h"
 #include "dlmcommon.h"
 #include "dlmdomain.h"
 #include "dlmdebug.h"
 
 #define MLOG_MASK_PREFIX (ML_DLM|ML_DLM_MASTER)
 #include "../cluster/masklog.h"
 
 static void dlm_mle_node_down(struct dlm_ctxt *dlm,
                   struct dlm_master_list_entry *mle,
                   struct o2nm_node *node,
                   int idx);
 static void dlm_mle_node_up(struct dlm_ctxt *dlm,
                 struct dlm_master_list_entry *mle,
                 struct o2nm_node *node,
                 int idx);
 
 static void dlm_assert_master_worker(struct dlm_work_item *item, void *data);
 static int dlm_do_assert_master(struct dlm_ctxt *dlm,
                 struct dlm_lock_resource *res,
                 void *nodemap, u32 flags);
 static void dlm_deref_lockres_worker(struct dlm_work_item *item, void *data);
 
 static inline int dlm_mle_equal(struct dlm_ctxt *dlm,
                 struct dlm_master_list_entry *mle,
                 const char *name,
                 unsigned int namelen)
 {
     if (dlm != mle->dlm)
         return 0;
 
     if (namelen != mle->mnamelen ||
         memcmp(name, mle->mname, namelen) != 0)
         return 0;
 
     return 1;
 }
 
 static struct kmem_cache *dlm_lockres_cache;
 static struct kmem_cache *dlm_lockname_cache;
 static struct kmem_cache *dlm_mle_cache;
 
 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 (!kref_read(&mle->mle_refs)) {
         /* this may or may not crash, but who cares.
          * it's a BUG. */
         mlog(ML_ERROR, "bad mle: %p\n", mle);
         dlm_print_one_mle(mle);
         BUG();
     } else
         kref_put(&mle->mle_refs, dlm_mle_release);
 }
 
 
 /* must not have any spinlocks coming in */
 static void dlm_put_mle(struct dlm_master_list_entry *mle)
 {
     struct dlm_ctxt *dlm;
     dlm = mle->dlm;
 
     spin_lock(&dlm->spinlock);
     spin_lock(&dlm->master_lock);
     __dlm_put_mle(mle);
     spin_unlock(&dlm->master_lock);
     spin_unlock(&dlm->spinlock);
 }
 
 static inline void dlm_get_mle(struct dlm_master_list_entry *mle)
 {
     kref_get(&mle->mle_refs);
 }
 
 static void dlm_init_mle(struct dlm_master_list_entry *mle,
             enum dlm_mle_type type,
             struct dlm_ctxt *dlm,
             struct dlm_lock_resource *res,
             const char *name,
             unsigned int namelen)
 {
     assert_spin_locked(&dlm->spinlock);
 
     mle->dlm = dlm;
     mle->type = type;
     INIT_HLIST_NODE(&mle->master_hash_node);
     INIT_LIST_HEAD(&mle->hb_events);
     memset(mle->maybe_map, 0, sizeof(mle->maybe_map));
     spin_lock_init(&mle->spinlock);
     init_waitqueue_head(&mle->wq);
     atomic_set(&mle->woken, 0);
     kref_init(&mle->mle_refs);
     memset(mle->response_map, 0, sizeof(mle->response_map));
     mle->master = O2NM_MAX_NODES;
     mle->new_master = O2NM_MAX_NODES;
     mle->inuse = 0;
 
     BUG_ON(mle->type != DLM_MLE_BLOCK &&
            mle->type != DLM_MLE_MASTER &&
            mle->type != DLM_MLE_MIGRATION);
 
     if (mle->type == DLM_MLE_MASTER) {
         BUG_ON(!res);
         mle->mleres = res;
         memcpy(mle->mname, res->lockname.name, res->lockname.len);
         mle->mnamelen = res->lockname.len;
         mle->mnamehash = res->lockname.hash;
     } else {
         BUG_ON(!name);
         mle->mleres = NULL;
         memcpy(mle->mname, name, namelen);
         mle->mnamelen = namelen;
         mle->mnamehash = dlm_lockid_hash(name, namelen);
     }
 
     atomic_inc(&dlm->mle_tot_count[mle->type]);
     atomic_inc(&dlm->mle_cur_count[mle->type]);
 
     /* copy off the node_map and register hb callbacks on our copy */
     memcpy(mle->node_map, dlm->domain_map, sizeof(mle->node_map));
     memcpy(mle->vote_map, dlm->domain_map, sizeof(mle->vote_map));
     clear_bit(dlm->node_num, mle->vote_map);
     clear_bit(dlm->node_num, mle->node_map);
 
     /* attach the mle to the domain node up/down events */
     __dlm_mle_attach_hb_events(dlm, mle);
 }
 
 void __dlm_unlink_mle(struct dlm_ctxt *dlm, struct dlm_master_list_entry *mle)
 {
     assert_spin_locked(&dlm->spinlock);
     assert_spin_locked(&dlm->master_lock);
 
     if (!hlist_unhashed(&mle->master_hash_node))
         hlist_del_init(&mle->master_hash_node);
 }
 
 void __dlm_insert_mle(struct dlm_ctxt *dlm, struct dlm_master_list_entry *mle)
 {
     struct hlist_head *bucket;
 
     assert_spin_locked(&dlm->master_lock);
 
     bucket = dlm_master_hash(dlm, mle->mnamehash);
     hlist_add_head(&mle->master_hash_node, bucket);
 }
 
 /* returns 1 if found, 0 if not */
 static int dlm_find_mle(struct dlm_ctxt *dlm,
             struct dlm_master_list_entry **mle,
             char *name, unsigned int namelen)
 {
     struct dlm_master_list_entry *tmpmle;
     struct hlist_head *bucket;
     unsigned int hash;
 
     assert_spin_locked(&dlm->master_lock);
 
     hash = dlm_lockid_hash(name, namelen);
     bucket = dlm_master_hash(dlm, hash);
     hlist_for_each_entry(tmpmle, bucket, master_hash_node) {
         if (!dlm_mle_equal(dlm, tmpmle, name, namelen))
             continue;
         dlm_get_mle(tmpmle);
         *mle = tmpmle;
         return 1;
     }
     return 0;
 }
 
 void dlm_hb_event_notify_attached(struct dlm_ctxt *dlm, int idx, int node_up)
 {
     struct dlm_master_list_entry *mle;
 
     assert_spin_locked(&dlm->spinlock);
 
     list_for_each_entry(mle, &dlm->mle_hb_events, hb_events) {
         if (node_up)
             dlm_mle_node_up(dlm, mle, NULL, idx);
         else
             dlm_mle_node_down(dlm, mle, NULL, idx);
     }
 }
 
 static void dlm_mle_node_down(struct dlm_ctxt *dlm,
                   struct dlm_master_list_entry *mle,
                   struct o2nm_node *node, int idx)
 {
     spin_lock(&mle->spinlock);
 
     if (!test_bit(idx, mle->node_map))
         mlog(0, "node %u already removed from nodemap!\n", idx);
     else
         clear_bit(idx, mle->node_map);
 
     spin_unlock(&mle->spinlock);
 }
 
 static void dlm_mle_node_up(struct dlm_ctxt *dlm,
                 struct dlm_master_list_entry *mle,
                 struct o2nm_node *node, int idx)
 {
     spin_lock(&mle->spinlock);
 
     if (test_bit(idx, mle->node_map))
         mlog(0, "node %u already in node map!\n", idx);
     else
         set_bit(idx, mle->node_map);
 
     spin_unlock(&mle->spinlock);
 }
 
 
 int dlm_init_mle_cache(void)
 {
     dlm_mle_cache = kmem_cache_create("o2dlm_mle",
                       sizeof(struct dlm_master_list_entry),
                       0, SLAB_HWCACHE_ALIGN,
                       NULL);
     if (dlm_mle_cache == NULL)
         return -ENOMEM;
     return 0;
 }
 
 void dlm_destroy_mle_cache(void)
 {
     kmem_cache_destroy(dlm_mle_cache);
 }
 
 static void dlm_mle_release(struct kref *kref)
 {
     struct dlm_master_list_entry *mle;
     struct dlm_ctxt *dlm;
 
     mle = container_of(kref, struct dlm_master_list_entry, mle_refs);
     dlm = mle->dlm;
 
     assert_spin_locked(&dlm->spinlock);
     assert_spin_locked(&dlm->master_lock);
 
     mlog(0, "Releasing mle for %.*s, type %d\n", mle->mnamelen, mle->mname,
          mle->type);
 
     /* remove from list if not already */
     __dlm_unlink_mle(dlm, mle);
 
     /* detach the mle from the domain node up/down events */
     __dlm_mle_detach_hb_events(dlm, mle);
 
     atomic_dec(&dlm->mle_cur_count[mle->type]);
 
     /* NOTE: kfree under spinlock here.
      * if this is bad, we can move this to a freelist. */
     kmem_cache_free(dlm_mle_cache, mle);
 }
 
 
 /*
  * LOCK RESOURCE FUNCTIONS
  */
 
 int dlm_init_master_caches(void)
 {
     dlm_lockres_cache = kmem_cache_create("o2dlm_lockres",
                           sizeof(struct dlm_lock_resource),
                           0, SLAB_HWCACHE_ALIGN, NULL);
     if (!dlm_lockres_cache)
         goto bail;
 
     dlm_lockname_cache = kmem_cache_create("o2dlm_lockname",
                            DLM_LOCKID_NAME_MAX, 0,
                            SLAB_HWCACHE_ALIGN, NULL);
     if (!dlm_lockname_cache)
         goto bail;
 
     return 0;
 bail:
     dlm_destroy_master_caches();
     return -ENOMEM;
 }
 
 void dlm_destroy_master_caches(void)
 {
     kmem_cache_destroy(dlm_lockname_cache);
     dlm_lockname_cache = NULL;
 
     kmem_cache_destroy(dlm_lockres_cache);
     dlm_lockres_cache = NULL;
 }
 
 static void dlm_lockres_release(struct kref *kref)
 {
     struct dlm_lock_resource *res;
     struct dlm_ctxt *dlm;
 
     res = container_of(kref, struct dlm_lock_resource, refs);
     dlm = res->dlm;
 
     /* This should not happen -- all lockres' have a name
      * associated with them at init time. */
     BUG_ON(!res->lockname.name);
 
     mlog(0, "destroying lockres %.*s\n", res->lockname.len,
          res->lockname.name);
 
     atomic_dec(&dlm->res_cur_count);
 
     if (!hlist_unhashed(&res->hash_node) ||
         !list_empty(&res->granted) ||
         !list_empty(&res->converting) ||
         !list_empty(&res->blocked) ||
         !list_empty(&res->dirty) ||
         !list_empty(&res->recovering) ||
         !list_empty(&res->purge)) {
         mlog(ML_ERROR,
              "Going to BUG for resource %.*s."
              "  We're on a list! [%c%c%c%c%c%c%c]\n",
              res->lockname.len, res->lockname.name,
              !hlist_unhashed(&res->hash_node) ? 'H' : ' ',
              !list_empty(&res->granted) ? 'G' : ' ',
              !list_empty(&res->converting) ? 'C' : ' ',
              !list_empty(&res->blocked) ? 'B' : ' ',
              !list_empty(&res->dirty) ? 'D' : ' ',
              !list_empty(&res->recovering) ? 'R' : ' ',
              !list_empty(&res->purge) ? 'P' : ' ');
 
         dlm_print_one_lock_resource(res);
     }
 
     /* By the time we're ready to blow this guy away, we shouldn't
      * be on any lists. */
     BUG_ON(!hlist_unhashed(&res->hash_node));
     BUG_ON(!list_empty(&res->granted));
     BUG_ON(!list_empty(&res->converting));
     BUG_ON(!list_empty(&res->blocked));
     BUG_ON(!list_empty(&res->dirty));
     BUG_ON(!list_empty(&res->recovering));
     BUG_ON(!list_empty(&res->purge));
 
     kmem_cache_free(dlm_lockname_cache, (void *)res->lockname.name);
 
     kmem_cache_free(dlm_lockres_cache, res);
 }
 
 void dlm_lockres_put(struct dlm_lock_resource *res)
 {
     kref_put(&res->refs, dlm_lockres_release);
 }
 
 static void dlm_init_lockres(struct dlm_ctxt *dlm,
                  struct dlm_lock_resource *res,
                  const char *name, unsigned int namelen)
 {
     char *qname;
 
     /* If we memset here, we lose our reference to the kmalloc'd
      * res->lockname.name, so be sure to init every field
      * correctly! */
 
     qname = (char *) res->lockname.name;
     memcpy(qname, name, namelen);
 
     res->lockname.len = namelen;
     res->lockname.hash = dlm_lockid_hash(name, namelen);
 
     init_waitqueue_head(&res->wq);
     spin_lock_init(&res->spinlock);
     INIT_HLIST_NODE(&res->hash_node);
     INIT_LIST_HEAD(&res->granted);
     INIT_LIST_HEAD(&res->converting);
     INIT_LIST_HEAD(&res->blocked);
     INIT_LIST_HEAD(&res->dirty);
     INIT_LIST_HEAD(&res->recovering);
     INIT_LIST_HEAD(&res->purge);
     INIT_LIST_HEAD(&res->tracking);
     atomic_set(&res->asts_reserved, 0);
     res->migration_pending = 0;
     res->inflight_locks = 0;
     res->inflight_assert_workers = 0;
 
     res->dlm = dlm;
 
     kref_init(&res->refs);
 
     atomic_inc(&dlm->res_tot_count);
     atomic_inc(&dlm->res_cur_count);
 
     /* just for consistency */
     spin_lock(&res->spinlock);
     dlm_set_lockres_owner(dlm, res, DLM_LOCK_RES_OWNER_UNKNOWN);
     spin_unlock(&res->spinlock);
 
     res->state = DLM_LOCK_RES_IN_PROGRESS;
 
     res->last_used = 0;
 
     spin_lock(&dlm->track_lock);
     list_add_tail(&res->tracking, &dlm->tracking_list);
     spin_unlock(&dlm->track_lock);
 
     memset(res->lvb, 0, DLM_LVB_LEN);
     memset(res->refmap, 0, sizeof(res->refmap));
 }
 
 struct dlm_lock_resource *dlm_new_lockres(struct dlm_ctxt *dlm,
                    const char *name,
                    unsigned int namelen)
 {
     struct dlm_lock_resource *res = NULL;
 
     res = kmem_cache_zalloc(dlm_lockres_cache, GFP_NOFS);
     if (!res)
         goto error;
 
     res->lockname.name = kmem_cache_zalloc(dlm_lockname_cache, GFP_NOFS);
     if (!res->lockname.name)
         goto error;
 
     dlm_init_lockres(dlm, res, name, namelen);
     return res;
 
 error:
     if (res)
         kmem_cache_free(dlm_lockres_cache, res);
     return NULL;
 }
 
 void dlm_lockres_set_refmap_bit(struct dlm_ctxt *dlm,
                 struct dlm_lock_resource *res, int bit)
 {
     assert_spin_locked(&res->spinlock);
 
     mlog(0, "res %.*s, set node %u, %ps()\n", res->lockname.len,
          res->lockname.name, bit, __builtin_return_address(0));
 
     set_bit(bit, res->refmap);
 }
 
 void dlm_lockres_clear_refmap_bit(struct dlm_ctxt *dlm,
                   struct dlm_lock_resource *res, int bit)
 {
     assert_spin_locked(&res->spinlock);
 
     mlog(0, "res %.*s, clr node %u, %ps()\n", res->lockname.len,
          res->lockname.name, bit, __builtin_return_address(0));
 
     clear_bit(bit, res->refmap);
 }
 
 static void __dlm_lockres_grab_inflight_ref(struct dlm_ctxt *dlm,
                    struct dlm_lock_resource *res)
 {
     res->inflight_locks++;
 
     mlog(0, "%s: res %.*s, inflight++: now %u, %ps()\n", dlm->name,
          res->lockname.len, res->lockname.name, res->inflight_locks,
          __builtin_return_address(0));
 }
 
 void dlm_lockres_grab_inflight_ref(struct dlm_ctxt *dlm,
                    struct dlm_lock_resource *res)
 {
     assert_spin_locked(&res->spinlock);
     __dlm_lockres_grab_inflight_ref(dlm, res);
 }
 
 void dlm_lockres_drop_inflight_ref(struct dlm_ctxt *dlm,
                    struct dlm_lock_resource *res)
 {
     assert_spin_locked(&res->spinlock);
 
     BUG_ON(res->inflight_locks == 0);
 
     res->inflight_locks--;
 
     mlog(0, "%s: res %.*s, inflight--: now %u, %ps()\n", dlm->name,
          res->lockname.len, res->lockname.name, res->inflight_locks,
          __builtin_return_address(0));
 
     wake_up(&res->wq);
 }
 
 void __dlm_lockres_grab_inflight_worker(struct dlm_ctxt *dlm,
         struct dlm_lock_resource *res)
 {
     assert_spin_locked(&res->spinlock);
     res->inflight_assert_workers++;
     mlog(0, "%s:%.*s: inflight assert worker++: now %u\n",
             dlm->name, res->lockname.len, res->lockname.name,
             res->inflight_assert_workers);
 }
 
 static void __dlm_lockres_drop_inflight_worker(struct dlm_ctxt *dlm,
         struct dlm_lock_resource *res)
 {
     assert_spin_locked(&res->spinlock);
     BUG_ON(res->inflight_assert_workers == 0);
     res->inflight_assert_workers--;
     mlog(0, "%s:%.*s: inflight assert worker--: now %u\n",
             dlm->name, res->lockname.len, res->lockname.name,
             res->inflight_assert_workers);
 }
 
 static void dlm_lockres_drop_inflight_worker(struct dlm_ctxt *dlm,
         struct dlm_lock_resource *res)
 {
     spin_lock(&res->spinlock);
     __dlm_lockres_drop_inflight_worker(dlm, res);
     spin_unlock(&res->spinlock);
 }
 
 /*
  * lookup a lock resource by name.
  * may already exist in the hashtable.
  * lockid is null terminated
  *
  * if not, allocate enough for the lockres and for
  * the temporary structure used in doing the mastering.
  *
  * also, do a lookup in the dlm->master_list to see
  * if another node has begun mastering the same lock.
  * if so, there should be a block entry in there
  * for this name, and we should *not* attempt to master
  * the lock here.   need to wait around for that node
  * to assert_master (or die).
  *
  */
 struct dlm_lock_resource * dlm_get_lock_resource(struct dlm_ctxt *dlm,
                       const char *lockid,
                       int namelen,
                       int flags)
 {
     struct dlm_lock_resource *tmpres=NULL, *res=NULL;
     struct dlm_master_list_entry *mle = NULL;
     struct dlm_master_list_entry *alloc_mle = NULL;
     int blocked = 0;
     int ret, nodenum;
     struct dlm_node_iter iter;
     unsigned int hash;
     int tries = 0;
     int bit, wait_on_recovery = 0;
 
     BUG_ON(!lockid);
 
     hash = dlm_lockid_hash(lockid, namelen);
 
     mlog(0, "get lockres %s (len %d)\n", lockid, namelen);
 
 lookup:
     spin_lock(&dlm->spinlock);
     tmpres = __dlm_lookup_lockres_full(dlm, lockid, namelen, hash);
     if (tmpres) {
         spin_unlock(&dlm->spinlock);
         spin_lock(&tmpres->spinlock);
 
         /*
          * Right after dlm spinlock was released, dlm_thread could have
          * purged the lockres. Check if lockres got unhashed. If so
          * start over.
          */
         if (hlist_unhashed(&tmpres->hash_node)) {
             spin_unlock(&tmpres->spinlock);
             dlm_lockres_put(tmpres);
             tmpres = NULL;
             goto lookup;
         }
 
         /* Wait on the thread that is mastering the resource */
         if (tmpres->owner == DLM_LOCK_RES_OWNER_UNKNOWN) {
             __dlm_wait_on_lockres(tmpres);
             BUG_ON(tmpres->owner == DLM_LOCK_RES_OWNER_UNKNOWN);
             spin_unlock(&tmpres->spinlock);
             dlm_lockres_put(tmpres);
             tmpres = NULL;
             goto lookup;
         }
 
         /* Wait on the resource purge to complete before continuing */
         if (tmpres->state & DLM_LOCK_RES_DROPPING_REF) {
             BUG_ON(tmpres->owner == dlm->node_num);
             __dlm_wait_on_lockres_flags(tmpres,
                             DLM_LOCK_RES_DROPPING_REF);
             spin_unlock(&tmpres->spinlock);
             dlm_lockres_put(tmpres);
             tmpres = NULL;
             goto lookup;
         }
 
         /* Grab inflight ref to pin the resource */
         dlm_lockres_grab_inflight_ref(dlm, tmpres);
 
         spin_unlock(&tmpres->spinlock);
         if (res) {
             spin_lock(&dlm->track_lock);
             if (!list_empty(&res->tracking))
                 list_del_init(&res->tracking);
             else
                 mlog(ML_ERROR, "Resource %.*s not "
                         "on the Tracking list\n",
                         res->lockname.len,
                         res->lockname.name);
             spin_unlock(&dlm->track_lock);
             dlm_lockres_put(res);
         }
         res = tmpres;
         goto leave;
     }
 
     if (!res) {
         spin_unlock(&dlm->spinlock);
         mlog(0, "allocating a new resource\n");
         /* nothing found and we need to allocate one. */
         alloc_mle = kmem_cache_alloc(dlm_mle_cache, GFP_NOFS);
         if (!alloc_mle)
             goto leave;
         res = dlm_new_lockres(dlm, lockid, namelen);
         if (!res)
             goto leave;
         goto lookup;
     }
 
     mlog(0, "no lockres found, allocated our own: %p\n", res);
 
     if (flags & LKM_LOCAL) {
         /* caller knows it's safe to assume it's not mastered elsewhere
          * DONE!  return right away */
         spin_lock(&res->spinlock);
         dlm_change_lockres_owner(dlm, res, dlm->node_num);
         __dlm_insert_lockres(dlm, res);
         dlm_lockres_grab_inflight_ref(dlm, res);
         spin_unlock(&res->spinlock);
         spin_unlock(&dlm->spinlock);
         /* lockres still marked IN_PROGRESS */
         goto wake_waiters;
     }
 
     /* check master list to see if another node has started mastering it */
     spin_lock(&dlm->master_lock);
 
     /* if we found a block, wait for lock to be mastered by another node */
     blocked = dlm_find_mle(dlm, &mle, (char *)lockid, namelen);
     if (blocked) {
         int mig;
         if (mle->type == DLM_MLE_MASTER) {
             mlog(ML_ERROR, "master entry for nonexistent lock!\n");
             BUG();
         }
         mig = (mle->type == DLM_MLE_MIGRATION);
         /* if there is a migration in progress, let the migration
          * finish before continuing.  we can wait for the absence
          * of the MIGRATION mle: either the migrate finished or
          * one of the nodes died and the mle was cleaned up.
          * if there is a BLOCK here, but it already has a master
          * set, we are too late.  the master does not have a ref
          * for us in the refmap.  detach the mle and drop it.
          * either way, go back to the top and start over. */
         if (mig || mle->master != O2NM_MAX_NODES) {
             BUG_ON(mig && mle->master == dlm->node_num);
             /* we arrived too late.  the master does not
              * have a ref for us. retry. */
             mlog(0, "%s:%.*s: late on %s\n",
                  dlm->name, namelen, lockid,
                  mig ?  "MIGRATION" : "BLOCK");
             spin_unlock(&dlm->master_lock);
             spin_unlock(&dlm->spinlock);
 
             /* master is known, detach */
             if (!mig)
                 dlm_mle_detach_hb_events(dlm, mle);
             dlm_put_mle(mle);
             mle = NULL;
             /* this is lame, but we can't wait on either
              * the mle or lockres waitqueue here */
             if (mig)
                 msleep(100);
             goto lookup;
         }
     } else {
         /* go ahead and try to master lock on this node */
         mle = alloc_mle;
         /* make sure this does not get freed below */
         alloc_mle = NULL;
         dlm_init_mle(mle, DLM_MLE_MASTER, dlm, res, NULL, 0);
         set_bit(dlm->node_num, mle->maybe_map);
         __dlm_insert_mle(dlm, mle);
 
         /* still holding the dlm spinlock, check the recovery map
          * to see if there are any nodes that still need to be
          * considered.  these will not appear in the mle nodemap
          * but they might own this lockres.  wait on them. */
         bit = find_first_bit(dlm->recovery_map, O2NM_MAX_NODES);
         if (bit < O2NM_MAX_NODES) {
             mlog(0, "%s: res %.*s, At least one node (%d) "
                  "to recover before lock mastery can begin\n",
                  dlm->name, namelen, (char *)lockid, bit);
             wait_on_recovery = 1;
         }
     }
 
     /* at this point there is either a DLM_MLE_BLOCK or a
      * DLM_MLE_MASTER on the master list, so it's safe to add the
      * lockres to the hashtable.  anyone who finds the lock will
      * still have to wait on the IN_PROGRESS. */
 
     /* finally add the lockres to its hash bucket */
     __dlm_insert_lockres(dlm, res);
 
     /* since this lockres is new it doesn't not require the spinlock */
     __dlm_lockres_grab_inflight_ref(dlm, res);
 
     /* get an extra ref on the mle in case this is a BLOCK
      * if so, the creator of the BLOCK may try to put the last
      * ref at this time in the assert master handler, so we
      * need an extra one to keep from a bad ptr deref. */
     dlm_get_mle_inuse(mle);
     spin_unlock(&dlm->master_lock);
     spin_unlock(&dlm->spinlock);
 
 redo_request:
     while (wait_on_recovery) {
         /* any cluster changes that occurred after dropping the
          * dlm spinlock would be detectable be a change on the mle,
          * so we only need to clear out the recovery map once. */
         if (dlm_is_recovery_lock(lockid, namelen)) {
             mlog(0, "%s: Recovery map is not empty, but must "
                  "master $RECOVERY lock now\n", dlm->name);
             if (!dlm_pre_master_reco_lockres(dlm, res))
                 wait_on_recovery = 0;
             else {
                 mlog(0, "%s: waiting 500ms for heartbeat state "
                     "change\n", dlm->name);
                 msleep(500);
             }
             continue;
         }
 
         dlm_kick_recovery_thread(dlm);
         msleep(1000);
         dlm_wait_for_recovery(dlm);
 
         spin_lock(&dlm->spinlock);
         bit = find_first_bit(dlm->recovery_map, O2NM_MAX_NODES);
         if (bit < O2NM_MAX_NODES) {
             mlog(0, "%s: res %.*s, At least one node (%d) "
                  "to recover before lock mastery can begin\n",
                  dlm->name, namelen, (char *)lockid, bit);
             wait_on_recovery = 1;
         } else
             wait_on_recovery = 0;
         spin_unlock(&dlm->spinlock);
 
         if (wait_on_recovery)
             dlm_wait_for_node_recovery(dlm, bit, 10000);
     }
 
     /* must wait for lock to be mastered elsewhere */
     if (blocked)
         goto wait;
 
     ret = -EINVAL;
     dlm_node_iter_init(mle->vote_map, &iter);
     while ((nodenum = dlm_node_iter_next(&iter)) >= 0) {
         ret = dlm_do_master_request(res, mle, nodenum);
         if (ret < 0)
             mlog_errno(ret);
         if (mle->master != O2NM_MAX_NODES) {
             /* found a master ! */
             if (mle->master <= nodenum)
                 break;
             /* if our master request has not reached the master
              * yet, keep going until it does.  this is how the
              * master will know that asserts are needed back to
              * the lower nodes. */
             mlog(0, "%s: res %.*s, Requests only up to %u but "
                  "master is %u, keep going\n", dlm->name, namelen,
                  lockid, nodenum, mle->master);
         }
     }
 
 wait:
     /* keep going until the response map includes all nodes */
     ret = dlm_wait_for_lock_mastery(dlm, res, mle, &blocked);
     if (ret < 0) {
         wait_on_recovery = 1;
         mlog(0, "%s: res %.*s, Node map changed, redo the master "
              "request now, blocked=%d\n", dlm->name, res->lockname.len,
              res->lockname.name, blocked);
         if (++tries > 20) {
             mlog(ML_ERROR, "%s: res %.*s, Spinning on "
                  "dlm_wait_for_lock_mastery, blocked = %d\n",
                  dlm->name, res->lockname.len,
                  res->lockname.name, blocked);
             dlm_print_one_lock_resource(res);
             dlm_print_one_mle(mle);
             tries = 0;
         }
         goto redo_request;
     }
 
     mlog(0, "%s: res %.*s, Mastered by %u\n", dlm->name, res->lockname.len,
          res->lockname.name, res->owner);
     /* make sure we never continue without this */
     BUG_ON(res->owner == O2NM_MAX_NODES);
 
     /* master is known, detach if not already detached */
     dlm_mle_detach_hb_events(dlm, mle);
     dlm_put_mle(mle);
     /* put the extra ref */
     dlm_put_mle_inuse(mle);
 
 wake_waiters:
     spin_lock(&res->spinlock);
     res->state &= ~DLM_LOCK_RES_IN_PROGRESS;
     spin_unlock(&res->spinlock);
     wake_up(&res->wq);
 
 leave:
     /* need to free the unused mle */
     if (alloc_mle)
         kmem_cache_free(dlm_mle_cache, alloc_mle);
 
     return res;
 }
 
 
 #define DLM_MASTERY_TIMEOUT_MS   5000
 
 static int dlm_wait_for_lock_mastery(struct dlm_ctxt *dlm,
                      struct dlm_lock_resource *res,
                      struct dlm_master_list_entry *mle,
                      int *blocked)
 {
     u8 m;
     int ret, bit;
     int map_changed, voting_done;
     int assert, sleep;
 
 recheck:
     ret = 0;
     assert = 0;
 
     /* check if another node has already become the owner */
     spin_lock(&res->spinlock);
     if (res->owner != DLM_LOCK_RES_OWNER_UNKNOWN) {
         mlog(0, "%s:%.*s: owner is suddenly %u\n", dlm->name,
              res->lockname.len, res->lockname.name, res->owner);
         spin_unlock(&res->spinlock);
         /* this will cause the master to re-assert across
          * the whole cluster, freeing up mles */
         if (res->owner != dlm->node_num) {
             ret = dlm_do_master_request(res, mle, res->owner);
             if (ret < 0) {
                 /* give recovery a chance to run */
                 mlog(ML_ERROR, "link to %u went down?: %d\n", res->owner, ret);
                 msleep(500);
                 goto recheck;
             }
         }
         ret = 0;
         goto leave;
     }
     spin_unlock(&res->spinlock);
 
     spin_lock(&mle->spinlock);
     m = mle->master;
     map_changed = (memcmp(mle->vote_map, mle->node_map,
                   sizeof(mle->vote_map)) != 0);
     voting_done = (memcmp(mle->vote_map, mle->response_map,
                  sizeof(mle->vote_map)) == 0);
 
     /* restart if we hit any errors */
     if (map_changed) {
         int b;
         mlog(0, "%s: %.*s: node map changed, restarting\n",
              dlm->name, res->lockname.len, res->lockname.name);
         ret = dlm_restart_lock_mastery(dlm, res, mle, *blocked);
         b = (mle->type == DLM_MLE_BLOCK);
         if ((*blocked && !b) || (!*blocked && b)) {
             mlog(0, "%s:%.*s: status change: old=%d new=%d\n",
                  dlm->name, res->lockname.len, res->lockname.name,
                  *blocked, b);
             *blocked = b;
         }
         spin_unlock(&mle->spinlock);
         if (ret < 0) {
             mlog_errno(ret);
             goto leave;
         }
         mlog(0, "%s:%.*s: restart lock mastery succeeded, "
              "rechecking now\n", dlm->name, res->lockname.len,
              res->lockname.name);
         goto recheck;
     } else {
         if (!voting_done) {
             mlog(0, "map not changed and voting not done "
                  "for %s:%.*s\n", dlm->name, res->lockname.len,
                  res->lockname.name);
         }
     }
 
     if (m != O2NM_MAX_NODES) {
         /* another node has done an assert!
          * all done! */
         sleep = 0;
     } else {
         sleep = 1;
         /* have all nodes responded? */
         if (voting_done && !*blocked) {
             bit = find_first_bit(mle->maybe_map, O2NM_MAX_NODES);
             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);
         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_first_bit(mle->maybe_map,
                                O2NM_MAX_NODES);
 
                 /* act like it was never there */
                 clear_bit(node, mle->maybe_map);
 
                     if (node == lowest) {
                     mlog(0, "expected master %u died"
                         " while this node was blocked "
                         "waiting on it!\n", node);
                     lowest = find_next_bit(mle->maybe_map,
                                 O2NM_MAX_NODES,
                                 lowest+1);
                     if (lowest < O2NM_MAX_NODES) {
                         mlog(0, "%s:%.*s:still "
                              "blocked. waiting on %u "
                              "now\n", dlm->name,
                              res->lockname.len,
                              res->lockname.name,
                              lowest);
                     } else {
                         /* mle is an MLE_BLOCK, but
                          * there is now nothing left to
                          * block on.  we need to return
                          * all the way back out and try
                          * again with an MLE_MASTER.
                          * dlm_do_local_recovery_cleanup
                          * has already run, so the mle
                          * refcount is ok */
                         mlog(0, "%s:%.*s: no "
                              "longer blocking. try to "
                              "master this here\n",
                              dlm->name,
                              res->lockname.len,
                              res->lockname.name);
                         mle->type = DLM_MLE_MASTER;
                         mle->mleres = res;
                     }
                 }
             }
 
             /* now blank out everything, as if we had never
              * contacted anyone */
             memset(mle->maybe_map, 0, sizeof(mle->maybe_map));
             memset(mle->response_map, 0, sizeof(mle->response_map));
             /* reset the vote_map to the current node_map */
             memcpy(mle->vote_map, mle->node_map,
                    sizeof(mle->node_map));
             /* put myself into the maybe map */
             if (mle->type != DLM_MLE_BLOCK)
                 set_bit(dlm->node_num, mle->maybe_map);
         }
         ret = -EAGAIN;
         node = dlm_bitmap_diff_iter_next(&bdi, &sc);
     }
     return ret;
 }
 
 
 /*
  * DLM_MASTER_REQUEST_MSG
  *
  * returns: 0 on success,
  *          -errno on a network error
  *
  * on error, the caller should assume the target node is "dead"
  *
  */
 
 static int dlm_do_master_request(struct dlm_lock_resource *res,
                  struct dlm_master_list_entry *mle, int to)
 {
     struct dlm_ctxt *dlm = mle->dlm;
     struct dlm_master_request request;
     int ret, response=0, resend;
 
     memset(&request, 0, sizeof(request));
     request.node_idx = dlm->node_num;
 
     BUG_ON(mle->type == DLM_MLE_MIGRATION);
 
     request.namelen = (u8)mle->mnamelen;
     memcpy(request.name, mle->mname, request.namelen);
 
 again:
     ret = o2net_send_message(DLM_MASTER_REQUEST_MSG, dlm->key, &request,
                  sizeof(request), to, &response);
     if (ret < 0)  {
         if (ret == -ESRCH) {
             /* should never happen */
             mlog(ML_ERROR, "TCP stack not ready!\n");
             BUG();
         } else if (ret == -EINVAL) {
             mlog(ML_ERROR, "bad args passed to o2net!\n");
             BUG();
         } else if (ret == -ENOMEM) {
             mlog(ML_ERROR, "out of memory while trying to send "
                  "network message!  retrying\n");
             /* this is totally crude */
             msleep(50);
             goto again;
         } else if (!dlm_is_host_down(ret)) {
             /* not a network error. bad. */
             mlog_errno(ret);
             mlog(ML_ERROR, "unhandled error!");
             BUG();
         }
         /* all other errors should be network errors,
          * and likely indicate node death */
         mlog(ML_ERROR, "link to %d went down!\n", to);
         goto out;
     }
 
     ret = 0;
     resend = 0;
     spin_lock(&mle->spinlock);
     switch (response) {
         case DLM_MASTER_RESP_YES:
             set_bit(to, mle->response_map);
             mlog(0, "node %u is the master, response=YES\n", to);
             mlog(0, "%s:%.*s: master node %u now knows I have a "
                  "reference\n", dlm->name, res->lockname.len,
                  res->lockname.name, to);
             mle->master = to;
             break;
         case DLM_MASTER_RESP_NO:
             mlog(0, "node %u not master, response=NO\n", to);
             set_bit(to, mle->response_map);
             break;
         case DLM_MASTER_RESP_MAYBE:
             mlog(0, "node %u not master, response=MAYBE\n", to);
             set_bit(to, mle->response_map);
             set_bit(to, mle->maybe_map);
             break;
         case DLM_MASTER_RESP_ERROR:
             mlog(0, "node %u hit an error, resending\n", to);
             resend = 1;
             response = 0;
             break;
         default:
             mlog(ML_ERROR, "bad response! %u\n", response);
             BUG();
     }
     spin_unlock(&mle->spinlock);
     if (resend) {
         /* this is also totally crude */
         msleep(50);
         goto again;
     }
 
 out:
     return ret;
 }
 
 /*
  * locks that can be taken here:
  * dlm->spinlock
  * res->spinlock
  * mle->spinlock
  * dlm->master_list
  *
  * if possible, TRIM THIS DOWN!!!
  */
 int dlm_master_request_handler(struct o2net_msg *msg, u32 len, void *data,
                    void **ret_data)
 {
     u8 response = DLM_MASTER_RESP_MAYBE;
     struct dlm_ctxt *dlm = data;
     struct dlm_lock_resource *res = NULL;
     struct dlm_master_request *request = (struct dlm_master_request *) msg->buf;
     struct dlm_master_list_entry *mle = NULL, *tmpmle = NULL;
     char *name;
     unsigned int namelen, hash;
     int found, ret;
     int set_maybe;
     int dispatch_assert = 0;
     int dispatched = 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);
 
         /*
          * Right after dlm spinlock was released, dlm_thread could have
          * purged the lockres. Check if lockres got unhashed. If so
          * start over.
          */
         if (hlist_unhashed(&res->hash_node)) {
             spin_unlock(&res->spinlock);
             dlm_lockres_put(res);
             goto way_up_top;
         }
 
         if (res->state & (DLM_LOCK_RES_RECOVERING|
                   DLM_LOCK_RES_MIGRATING)) {
             spin_unlock(&res->spinlock);
             mlog(0, "returning DLM_MASTER_RESP_ERROR since res is "
                  "being recovered/migrated\n");
             response = DLM_MASTER_RESP_ERROR;
             if (mle)
                 kmem_cache_free(dlm_mle_cache, mle);
             goto send_response;
         }
 
         if (res->owner == dlm->node_num) {
             dlm_lockres_set_refmap_bit(dlm, res, request->node_idx);
             spin_unlock(&res->spinlock);
             response = DLM_MASTER_RESP_YES;
             if (mle)
                 kmem_cache_free(dlm_mle_cache, mle);
 
             /* this node is the owner.
              * there is some extra work that needs to
              * happen now.  the requesting node has
              * caused all nodes up to this one to
              * create mles.  this node now needs to
              * go back and clean those up. */
             dispatch_assert = 1;
             goto send_response;
         } else if (res->owner != DLM_LOCK_RES_OWNER_UNKNOWN) {
             spin_unlock(&res->spinlock);
             // mlog(0, "node %u is the master\n", res->owner);
             response = DLM_MASTER_RESP_NO;
             if (mle)
                 kmem_cache_free(dlm_mle_cache, mle);
             goto send_response;
         }
 
         /* ok, there is no owner.  either this node is
          * being blocked, or it is actively trying to
          * master this lock. */
         if (!(res->state & DLM_LOCK_RES_IN_PROGRESS)) {
             mlog(ML_ERROR, "lock with no owner should be "
                  "in-progress!\n");
             BUG();
         }
 
         // mlog(0, "lockres is in progress...\n");
         spin_lock(&dlm->master_lock);
         found = dlm_find_mle(dlm, &tmpmle, name, namelen);
         if (!found) {
             mlog(ML_ERROR, "no mle found for this lock!\n");
             BUG();
         }
         set_maybe = 1;
         spin_lock(&tmpmle->spinlock);
         if (tmpmle->type == DLM_MLE_BLOCK) {
             // mlog(0, "this node is waiting for "
             // "lockres to be mastered\n");
             response = DLM_MASTER_RESP_NO;
         } else if (tmpmle->type == DLM_MLE_MIGRATION) {
             mlog(0, "node %u is master, but trying to migrate to "
                  "node %u.\n", tmpmle->master, tmpmle->new_master);
             if (tmpmle->master == dlm->node_num) {
                 mlog(ML_ERROR, "no owner on lockres, but this "
                      "node is trying to migrate it to %u?!\n",
                      tmpmle->new_master);
                 BUG();
             } else {
                 /* the real master can respond on its own */
                 response = DLM_MASTER_RESP_NO;
             }
         } else if (tmpmle->master != DLM_LOCK_RES_OWNER_UNKNOWN) {
             set_maybe = 0;
             if (tmpmle->master == dlm->node_num) {
                 response = DLM_MASTER_RESP_YES;
                 /* this node will be the owner.
                  * go back and clean the mles on any
                  * other nodes */
                 dispatch_assert = 1;
                 dlm_lockres_set_refmap_bit(dlm, res,
                                request->node_idx);
             } else
                 response = DLM_MASTER_RESP_NO;
         } else {
             // mlog(0, "this node is attempting to "
             // "master lockres\n");
             response = DLM_MASTER_RESP_MAYBE;
         }
         if (set_maybe)
             set_bit(request->node_idx, tmpmle->maybe_map);
         spin_unlock(&tmpmle->spinlock);
 
         spin_unlock(&dlm->master_lock);
         spin_unlock(&res->spinlock);
 
         /* keep the mle attached to heartbeat events */
         dlm_put_mle(tmpmle);
         if (mle)
             kmem_cache_free(dlm_mle_cache, mle);
         goto send_response;
     }
 
     /*
      * lockres doesn't exist on this node
      * if there is an MLE_BLOCK, return NO
      * if there is an MLE_MASTER, return MAYBE
      * otherwise, add an MLE_BLOCK, return NO
      */
     spin_lock(&dlm->master_lock);
     found = dlm_find_mle(dlm, &tmpmle, name, namelen);
     if (!found) {
         /* this lockid has never been seen on this node yet */
         // mlog(0, "no mle found\n");
         if (!mle) {
             spin_unlock(&dlm->master_lock);
             spin_unlock(&dlm->spinlock);
 
             mle = kmem_cache_alloc(dlm_mle_cache, GFP_NOFS);
             if (!mle) {
                 response = DLM_MASTER_RESP_ERROR;
                 mlog_errno(-ENOMEM);
                 goto send_response;
             }
             goto way_up_top;
         }
 
         // mlog(0, "this is second time thru, already allocated, "
         // "add the block.\n");
         dlm_init_mle(mle, DLM_MLE_BLOCK, dlm, NULL, name, namelen);
         set_bit(request->node_idx, mle->maybe_map);
         __dlm_insert_mle(dlm, mle);
         response = DLM_MASTER_RESP_NO;
     } else {
         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;
         set_bit(request->node_idx, tmpmle->maybe_map);
         spin_unlock(&tmpmle->spinlock);
     }
     spin_unlock(&dlm->master_lock);
     spin_unlock(&dlm->spinlock);
 
     if (found) {
         /* keep the mle attached to heartbeat events */
         dlm_put_mle(tmpmle);
     }
 send_response:
     /*
      * __dlm_lookup_lockres() grabbed a reference to this lockres.
      * The reference is released by dlm_assert_master_worker() under
      * the call to dlm_dispatch_assert_master().  If
      * dlm_assert_master_worker() isn't called, we drop it here.
      */
     if (dispatch_assert) {
         mlog(0, "%u is the owner of %.*s, cleaning everyone else\n",
                  dlm->node_num, res->lockname.len, res->lockname.name);
         spin_lock(&res->spinlock);
         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;
             spin_unlock(&res->spinlock);
             dlm_lockres_put(res);
         } else {
             dispatched = 1;
             __dlm_lockres_grab_inflight_worker(dlm, res);
             spin_unlock(&res->spinlock);
         }
     } else {
         if (res)
             dlm_lockres_put(res);
     }
 
     if (!dispatched)
         dlm_put(dlm);
     return response;
 }
 
 /*
  * DLM_ASSERT_MASTER_MSG
  */
 
 
 /*
  * NOTE: this can be used for debugging
  * can periodically run all locks owned by this node
  * and re-assert across the cluster...
  */
 static int dlm_do_assert_master(struct dlm_ctxt *dlm,
                 struct dlm_lock_resource *res,
                 void *nodemap, u32 flags)
 {
     struct dlm_assert_master assert;
     int to, tmpret;
     struct dlm_node_iter iter;
     int ret = 0;
     int reassert;
     const char *lockname = res->lockname.name;
     unsigned int namelen = res->lockname.len;
 
     BUG_ON(namelen > O2NM_MAX_NAME_LEN);
 
     spin_lock(&res->spinlock);
     res->state |= DLM_LOCK_RES_SETREF_INPROG;
     spin_unlock(&res->spinlock);
 
 again:
     reassert = 0;
 
     /* note that if this nodemap is empty, it returns 0 */
     dlm_node_iter_init(nodemap, &iter);
     while ((to = dlm_node_iter_next(&iter)) >= 0) {
         int r = 0;
         struct dlm_master_list_entry *mle = NULL;
 
         mlog(0, "sending assert master to %d (%.*s)\n", to,
              namelen, lockname);
         memset(&assert, 0, sizeof(assert));
         assert.node_idx = dlm->node_num;
         assert.namelen = namelen;
         memcpy(assert.name, lockname, namelen);
         assert.flags = cpu_to_be32(flags);
 
         tmpret = o2net_send_message(DLM_ASSERT_MASTER_MSG, dlm->key,
                         &assert, sizeof(assert), to, &r);
         if (tmpret < 0) {
             mlog(ML_ERROR, "Error %d when sending message %u (key "
                  "0x%x) to node %u\n", tmpret,
                  DLM_ASSERT_MASTER_MSG, dlm->key, to);
             if (!dlm_is_host_down(tmpret)) {
                 mlog(ML_ERROR, "unhandled error=%d!\n", tmpret);
                 BUG();
             }
             /* a node died.  finish out the rest of the nodes. */
             mlog(0, "link to %d went down!\n", to);
             /* any nonzero status return will do */
             ret = tmpret;
             r = 0;
         } else if (r < 0) {
             /* ok, something horribly messed.  kill thyself. */
             mlog(ML_ERROR,"during assert master of %.*s to %u, "
                  "got %d.\n", namelen, lockname, to, r);
             spin_lock(&dlm->spinlock);
             spin_lock(&dlm->master_lock);
             if (dlm_find_mle(dlm, &mle, (char *)lockname,
                      namelen)) {
                 dlm_print_one_mle(mle);
                 __dlm_put_mle(mle);
             }
             spin_unlock(&dlm->master_lock);
             spin_unlock(&dlm->spinlock);
             BUG();
         }
 
         if (r & DLM_ASSERT_RESPONSE_REASSERT &&
             !(r & DLM_ASSERT_RESPONSE_MASTERY_REF)) {
                 mlog(ML_ERROR, "%.*s: very strange, "
                      "master MLE but no lockres on %u\n",
                      namelen, lockname, to);
         }
 
         if (r & DLM_ASSERT_RESPONSE_REASSERT) {
             mlog(0, "%.*s: node %u create mles on other "
                  "nodes and requests a re-assert\n",
                  namelen, lockname, to);
             reassert = 1;
         }
         if (r & DLM_ASSERT_RESPONSE_MASTERY_REF) {
             mlog(0, "%.*s: node %u has a reference to this "
                  "lockres, set the bit in the refmap\n",
                  namelen, lockname, to);
             spin_lock(&res->spinlock);
             dlm_lockres_set_refmap_bit(dlm, res, to);
             spin_unlock(&res->spinlock);
         }
     }
 
     if (reassert)
         goto again;
 
     spin_lock(&res->spinlock);
     res->state &= ~DLM_LOCK_RES_SETREF_INPROG;
     spin_unlock(&res->spinlock);
     wake_up(&res->wq);
 
     return ret;
 }
 
 /*
  * locks that can be taken here:
  * dlm->spinlock
  * res->spinlock
  * mle->spinlock
  * dlm->master_list
  *
  * if possible, TRIM THIS DOWN!!!
  */
 int dlm_assert_master_handler(struct o2net_msg *msg, u32 len, void *data,
                   void **ret_data)
 {
     struct dlm_ctxt *dlm = data;
     struct dlm_master_list_entry *mle = NULL;
     struct dlm_assert_master *assert = (struct dlm_assert_master *)msg->buf;
     struct dlm_lock_resource *res = NULL;
     char *name;
     unsigned int namelen, hash;
     u32 flags;
     int master_request = 0, have_lockres_ref = 0;
     int ret = 0;
 
     if (!dlm_grab(dlm))
         return 0;
 
     name = assert->name;
     namelen = assert->namelen;
     hash = dlm_lockid_hash(name, namelen);
     flags = be32_to_cpu(assert->flags);
 
     if (namelen > DLM_LOCKID_NAME_MAX) {
         mlog(ML_ERROR, "Invalid name length!");
         goto done;
     }
 
     spin_lock(&dlm->spinlock);
 
     if (flags)
         mlog(0, "assert_master with flags: %u\n", flags);
 
     /* find the MLE */
     spin_lock(&dlm->master_lock);
     if (!dlm_find_mle(dlm, &mle, name, namelen)) {
         /* not an error, could be master just re-asserting */
         mlog(0, "just got an assert_master from %u, but no "
              "MLE for it! (%.*s)\n", assert->node_idx,
              namelen, name);
     } else {
         int bit = find_first_bit(mle->maybe_map, O2NM_MAX_NODES);
         if (bit >= O2NM_MAX_NODES) {
             /* not necessarily an error, though less likely.
              * could be master just re-asserting. */
             mlog(0, "no bits set in the maybe_map, but %u "
                  "is asserting! (%.*s)\n", assert->node_idx,
                  namelen, name);
         } else if (bit != assert->node_idx) {
             if (flags & DLM_ASSERT_MASTER_MLE_CLEANUP) {
                 mlog(0, "master %u was found, %u should "
                      "back off\n", assert->node_idx, bit);
             } else {
                 /* with the fix for bug 569, a higher node
                  * number winning the mastery will respond
                  * YES to mastery requests, but this node
                  * had no way of knowing.  let it pass. */
                 mlog(0, "%u is the lowest node, "
                      "%u is asserting. (%.*s)  %u must "
                      "have begun after %u won.\n", bit,
                      assert->node_idx, namelen, name, bit,
                      assert->node_idx);
             }
         }
         if (mle->type == DLM_MLE_MIGRATION) {
             if (flags & DLM_ASSERT_MASTER_MLE_CLEANUP) {
                 mlog(0, "%s:%.*s: got cleanup assert"
                      " from %u for migration\n",
                      dlm->name, namelen, name,
                      assert->node_idx);
             } else if (!(flags & DLM_ASSERT_MASTER_FINISH_MIGRATION)) {
                 mlog(0, "%s:%.*s: got unrelated assert"
                      " from %u for migration, ignoring\n",
                      dlm->name, namelen, name,
                      assert->node_idx);
                 __dlm_put_mle(mle);
                 spin_unlock(&dlm->master_lock);
                 spin_unlock(&dlm->spinlock);
                 goto done;
             }
         }
     }
     spin_unlock(&dlm->master_lock);
 
     /* ok everything checks out with the MLE
      * now check to see if there is a lockres */
     res = __dlm_lookup_lockres(dlm, name, namelen, hash);
     if (res) {
         spin_lock(&res->spinlock);
         if (res->state & DLM_LOCK_RES_RECOVERING)  {
             mlog(ML_ERROR, "%u asserting but %.*s is "
                  "RECOVERING!\n", assert->node_idx, namelen, name);
             goto kill;
         }
         if (!mle) {
             if (res->owner != DLM_LOCK_RES_OWNER_UNKNOWN &&
                 res->owner != assert->node_idx) {
                 mlog(ML_ERROR, "DIE! Mastery assert from %u, "
                      "but current owner is %u! (%.*s)\n",
                      assert->node_idx, res->owner, namelen,
                      name);
                 __dlm_print_one_lock_resource(res);
                 BUG();
             }
         } else if (mle->type != DLM_MLE_MIGRATION) {
             if (res->owner != DLM_LOCK_RES_OWNER_UNKNOWN) {
                 /* owner is just re-asserting */
                 if (res->owner == assert->node_idx) {
                     mlog(0, "owner %u re-asserting on "
                          "lock %.*s\n", assert->node_idx,
                          namelen, name);
                     goto ok;
                 }
                 mlog(ML_ERROR, "got assert_master from "
                      "node %u, but %u is the owner! "
                      "(%.*s)\n", assert->node_idx,
                      res->owner, namelen, name);
                 goto kill;
             }
             if (!(res->state & DLM_LOCK_RES_IN_PROGRESS)) {
                 mlog(ML_ERROR, "got assert from %u, but lock "
                      "with no owner should be "
                      "in-progress! (%.*s)\n",
                      assert->node_idx,
                      namelen, name);
                 goto kill;
             }
         } else /* mle->type == DLM_MLE_MIGRATION */ {
             /* should only be getting an assert from new master */
             if (assert->node_idx != mle->new_master) {
                 mlog(ML_ERROR, "got assert from %u, but "
                      "new master is %u, and old master "
                      "was %u (%.*s)\n",
                      assert->node_idx, mle->new_master,
                      mle->master, namelen, name);
                 goto kill;
             }
 
         }
 ok:
         spin_unlock(&res->spinlock);
     }
 
     // mlog(0, "woo!  got an assert_master from node %u!\n",
     //       assert->node_idx);
     if (mle) {
         int extra_ref = 0;
         int nn = -1;
         int rr, err = 0;
 
         spin_lock(&mle->spinlock);
         if (mle->type == DLM_MLE_BLOCK || mle->type == DLM_MLE_MIGRATION)
             extra_ref = 1;
         else {
             /* MASTER mle: if any bits set in the response map
              * then the calling node needs to re-assert to clear
              * up nodes that this node contacted */
             while ((nn = find_next_bit (mle->response_map, O2NM_MAX_NODES,
                             nn+1)) < O2NM_MAX_NODES) {
                 if (nn != dlm->node_num && nn != assert->node_idx) {
                     master_request = 1;
                     break;
                 }
             }
         }
         mle->master = assert->node_idx;
         atomic_set(&mle->woken, 1);
         wake_up(&mle->wq);
         spin_unlock(&mle->spinlock);
 
         if (res) {
             int wake = 0;
             spin_lock(&res->spinlock);
             if (mle->type == DLM_MLE_MIGRATION) {
                 mlog(0, "finishing off migration of lockres %.*s, "
                         "from %u to %u\n",
                         res->lockname.len, res->lockname.name,
                         dlm->node_num, mle->new_master);
                 res->state &= ~DLM_LOCK_RES_MIGRATING;
                 wake = 1;
                 dlm_change_lockres_owner(dlm, res, mle->new_master);
                 BUG_ON(res->state & DLM_LOCK_RES_DIRTY);
             } else {
                 dlm_change_lockres_owner(dlm, res, mle->master);
             }
             spin_unlock(&res->spinlock);
             have_lockres_ref = 1;
             if (wake)
                 wake_up(&res->wq);
         }
 
         /* master is known, detach if not already detached.
          * ensures that only one assert_master call will happen
          * on this mle. */
         spin_lock(&dlm->master_lock);
 
         rr = kref_read(&mle->mle_refs);
         if (mle->inuse > 0) {
             if (extra_ref && rr < 3)
                 err = 1;
             else if (!extra_ref && rr < 2)
                 err = 1;
         } else {
             if (extra_ref && rr < 2)
                 err = 1;
             else if (!extra_ref && rr < 1)
                 err = 1;
         }
         if (err) {
             mlog(ML_ERROR, "%s:%.*s: got assert master from %u "
                  "that will mess up this node, refs=%d, extra=%d, "
                  "inuse=%d\n", dlm->name, namelen, name,
                  assert->node_idx, rr, extra_ref, mle->inuse);
             dlm_print_one_mle(mle);
         }
         __dlm_unlink_mle(dlm, mle);
         __dlm_mle_detach_hb_events(dlm, mle);
         __dlm_put_mle(mle);
         if (extra_ref) {
             /* the assert master message now balances the extra
              * ref given by the master / migration request message.
              * if this is the last put, it will be removed
              * from the list. */
             __dlm_put_mle(mle);
         }
         spin_unlock(&dlm->master_lock);
     } else if (res) {
         if (res->owner != assert->node_idx) {
             mlog(0, "assert_master from %u, but current "
                  "owner is %u (%.*s), no mle\n", assert->node_idx,
                  res->owner, namelen, name);
         }
     }
     spin_unlock(&dlm->spinlock);
 
 done:
     ret = 0;
     if (res) {
         spin_lock(&res->spinlock);
         res->state |= DLM_LOCK_RES_SETREF_INPROG;
         spin_unlock(&res->spinlock);
         *ret_data = (void *)res;
     }
     dlm_put(dlm);
     if (master_request) {
         mlog(0, "need to tell master to reassert\n");
         /* positive. negative would shoot down the node. */
         ret |= DLM_ASSERT_RESPONSE_REASSERT;
         if (!have_lockres_ref) {
             mlog(ML_ERROR, "strange, got assert from %u, MASTER "
                  "mle present here for %s:%.*s, but no lockres!\n",
                  assert->node_idx, dlm->name, namelen, name);
         }
     }
     if (have_lockres_ref) {
         /* let the master know we have a reference to the lockres */
         ret |= DLM_ASSERT_RESPONSE_MASTERY_REF;
         mlog(0, "%s:%.*s: got assert from %u, need a ref\n",
              dlm->name, namelen, name, assert->node_idx);
     }
     return ret;
 
 kill:
     /* kill the caller! */
     mlog(ML_ERROR, "Bad message received from another node.  Dumping state "
          "and killing the other node now!  This node is OK and can continue.\n");
     __dlm_print_one_lock_resource(res);
     spin_unlock(&res->spinlock);
     spin_lock(&dlm->master_lock);
     if (mle)
         __dlm_put_mle(mle);
     spin_unlock(&dlm->master_lock);
     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_ATOMIC);
     if (!item)
         return -ENOMEM;
 
 
     /* queue up work for dlm_assert_master_worker */
     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_drop_inflight_worker(dlm, res);
 
     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 heartbeat callback is
  * fired, so we can know for sure that it is safe to continue once
  * the node returns a live node or no node.  */
 static int dlm_pre_master_reco_lockres(struct dlm_ctxt *dlm,
                        struct dlm_lock_resource *res)
 {
     struct dlm_node_iter iter;
     int nodenum;
     int ret = 0;
     u8 master = DLM_LOCK_RES_OWNER_UNKNOWN;
 
     spin_lock(&dlm->spinlock);
     dlm_node_iter_init(dlm->domain_map, &iter);
     spin_unlock(&dlm->spinlock);
 
     while ((nodenum = dlm_node_iter_next(&iter)) >= 0) {
         /* do not send to self */
         if (nodenum == dlm->node_num)
             continue;
         ret = dlm_do_master_requery(dlm, res, nodenum, &master);
         if (ret < 0) {
             mlog_errno(ret);
             if (!dlm_is_host_down(ret))
                 BUG();
             /* host is down, so answer for that node would be
              * DLM_LOCK_RES_OWNER_UNKNOWN.  continue. */
             ret = 0;
         }
 
         if (master != DLM_LOCK_RES_OWNER_UNKNOWN) {
             /* check to see if this master is in the recovery map */
             spin_lock(&dlm->spinlock);
             if (test_bit(master, dlm->recovery_map)) {
                 mlog(ML_NOTICE, "%s: node %u has not seen "
                      "node %u go down yet, and thinks the "
                      "dead node is mastering the recovery "
                      "lock.  must wait.\n", dlm->name,
                      nodenum, master);
                 ret = -EAGAIN;
             }
             spin_unlock(&dlm->spinlock);
             mlog(0, "%s: reco lock master is %u\n", dlm->name,
                  master);
             break;
         }
     }
     return ret;
 }
 
 /*
  * DLM_DEREF_LOCKRES_MSG
  */
 
 int dlm_drop_lockres_ref(struct dlm_ctxt *dlm, struct dlm_lock_resource *res)
 {
     struct dlm_deref_lockres deref;
     int ret = 0, r;
     const char *lockname;
     unsigned int namelen;
 
     lockname = res->lockname.name;
     namelen = res->lockname.len;
     BUG_ON(namelen > O2NM_MAX_NAME_LEN);
 
     memset(&deref, 0, sizeof(deref));
     deref.node_idx = dlm->node_num;
     deref.namelen = namelen;
     memcpy(deref.name, lockname, namelen);
 
     ret = o2net_send_message(DLM_DEREF_LOCKRES_MSG, dlm->key,
                  &deref, sizeof(deref), res->owner, &r);
     if (ret < 0)
         mlog(ML_ERROR, "%s: res %.*s, error %d send DEREF to node %u\n",
              dlm->name, namelen, lockname, ret, res->owner);
     else if (r < 0) {
         /* BAD.  other node says I did not have a ref. */
         mlog(ML_ERROR, "%s: res %.*s, DEREF to node %u got %d\n",
              dlm->name, namelen, lockname, res->owner, r);
         dlm_print_one_lock_resource(res);
         if (r == -ENOMEM)
             BUG();
     } else
         ret = r;
 
     return ret;
 }
 
 int dlm_deref_lockres_handler(struct o2net_msg *msg, u32 len, void *data,
                   void **ret_data)
 {
     struct dlm_ctxt *dlm = data;
     struct dlm_deref_lockres *deref = (struct dlm_deref_lockres *)msg->buf;
     struct dlm_lock_resource *res = NULL;
     char *name;
     unsigned int namelen;
     int ret = -EINVAL;
     u8 node;
     unsigned int hash;
     struct dlm_work_item *item;
     int cleared = 0;
     int dispatch = 0;
 
     if (!dlm_grab(dlm))
         return 0;
 
     name = deref->name;
     namelen = deref->namelen;
     node = deref->node_idx;
 
     if (namelen > DLM_LOCKID_NAME_MAX) {
         mlog(ML_ERROR, "Invalid name length!");
         goto done;
     }
     if (deref->node_idx >= O2NM_MAX_NODES) {
         mlog(ML_ERROR, "Invalid node number: %u\n", node);
         goto done;
     }
 
     hash = dlm_lockid_hash(name, namelen);
 
     spin_lock(&dlm->spinlock);
     res = __dlm_lookup_lockres_full(dlm, name, namelen, hash);
     if (!res) {
         spin_unlock(&dlm->spinlock);
         mlog(ML_ERROR, "%s:%.*s: bad lockres name\n",
              dlm->name, namelen, name);
         goto done;
     }
     spin_unlock(&dlm->spinlock);
 
     spin_lock(&res->spinlock);
     if (res->state & DLM_LOCK_RES_SETREF_INPROG)
         dispatch = 1;
     else {
         BUG_ON(res->state & DLM_LOCK_RES_DROPPING_REF);
         if (test_bit(node, res->refmap)) {
             dlm_lockres_clear_refmap_bit(dlm, res, node);
             cleared = 1;
         }
     }
     spin_unlock(&res->spinlock);
 
     if (!dispatch) {
         if (cleared)
             dlm_lockres_calc_usage(dlm, res);
         else {
             mlog(ML_ERROR, "%s:%.*s: node %u trying to drop ref "
                 "but it is already dropped!\n", dlm->name,
                 res->lockname.len, res->lockname.name, node);
             dlm_print_one_lock_resource(res);
         }
         ret = DLM_DEREF_RESPONSE_DONE;
         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 DLM_DEREF_RESPONSE_INPROG;
 
 done:
     if (res)
         dlm_lockres_put(res);
     dlm_put(dlm);
 
     return ret;
 }
 
 int dlm_deref_lockres_done_handler(struct o2net_msg *msg, u32 len, void *data,
                   void **ret_data)
 {
     struct dlm_ctxt *dlm = data;
     struct dlm_deref_lockres_done *deref
             = (struct dlm_deref_lockres_done *)msg->buf;
     struct dlm_lock_resource *res = NULL;
     char *name;
     unsigned int namelen;
     int ret = -EINVAL;
     u8 node;
     unsigned int hash;
 
     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_lock(&res->spinlock);
     if (!(res->state & DLM_LOCK_RES_DROPPING_REF)) {
         spin_unlock(&res->spinlock);
         spin_unlock(&dlm->spinlock);
         mlog(ML_NOTICE, "%s:%.*s: node %u sends deref done "
             "but it is already derefed!\n", dlm->name,
             res->lockname.len, res->lockname.name, node);
         ret = 0;
         goto done;
     }
 
     __dlm_do_purge_lockres(dlm, res);
     spin_unlock(&res->spinlock);
     wake_up(&res->wq);
 
     spin_unlock(&dlm->spinlock);
 
     ret = 0;
 done:
     if (res)
         dlm_lockres_put(res);
     dlm_put(dlm);
     return ret;
 }
 
 static void dlm_drop_lockres_ref_done(struct dlm_ctxt *dlm,
         struct dlm_lock_resource *res, u8 node)
 {
     struct dlm_deref_lockres_done deref;
     int ret = 0, r;
     const char *lockname;
     unsigned int namelen;
 
     lockname = res->lockname.name;
     namelen = res->lockname.len;
     BUG_ON(namelen > O2NM_MAX_NAME_LEN);
 
     memset(&deref, 0, sizeof(deref));
     deref.node_idx = dlm->node_num;
     deref.namelen = namelen;
     memcpy(deref.name, lockname, namelen);
 
     ret = o2net_send_message(DLM_DEREF_LOCKRES_DONE, dlm->key,
                  &deref, sizeof(deref), node, &r);
     if (ret < 0) {
         mlog(ML_ERROR, "%s: res %.*s, error %d send DEREF DONE "
                 " to node %u\n", dlm->name, namelen,
                 lockname, ret, node);
     } else if (r < 0) {
         /* ignore the error */
         mlog(ML_ERROR, "%s: res %.*s, DEREF to node %u got %d\n",
              dlm->name, namelen, lockname, node, r);
         dlm_print_one_lock_resource(res);
     }
 }
 
 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);
     __dlm_wait_on_lockres_flags(res, DLM_LOCK_RES_SETREF_INPROG);
     if (test_bit(node, res->refmap)) {
         dlm_lockres_clear_refmap_bit(dlm, res, node);
         cleared = 1;
     }
     spin_unlock(&res->spinlock);
 
     dlm_drop_lockres_ref_done(dlm, res, node);
 
     if (cleared) {
         mlog(0, "%s:%.*s node %u ref dropped in dispatch\n",
              dlm->name, res->lockname.len, res->lockname.name, node);
         dlm_lockres_calc_usage(dlm, res);
     } else {
         mlog(ML_ERROR, "%s:%.*s: node %u trying to drop ref "
              "but it is already dropped!\n", dlm->name,
              res->lockname.len, res->lockname.name, node);
         dlm_print_one_lock_resource(res);
     }
 
     dlm_lockres_put(res);
 }
 
 /*
  * A migratable resource is one that is :
  * 1. locally mastered, and,
  * 2. zero local locks, and,
  * 3. one or more non-local locks, or, one or more references
  * Returns 1 if yes, 0 if not.
  */
 static int dlm_is_lockres_migratable(struct dlm_ctxt *dlm,
                       struct dlm_lock_resource *res)
 {
     enum dlm_lockres_list idx;
     int nonlocal = 0, node_ref;
     struct list_head *queue;
     struct dlm_lock *lock;
     u64 cookie;
 
     assert_spin_locked(&res->spinlock);
 
     /* delay migration when the lockres is in MIGRATING state */
     if (res->state & DLM_LOCK_RES_MIGRATING)
         return 0;
 
     /* delay migration when the lockres is in RECOCERING state */
     if (res->state & (DLM_LOCK_RES_RECOVERING|
             DLM_LOCK_RES_RECOVERY_WAITING))
         return 0;
 
     if (res->owner != dlm->node_num)
         return 0;
 
         for (idx = DLM_GRANTED_LIST; idx <= DLM_BLOCKED_LIST; idx++) {
         queue = dlm_list_idx_to_ptr(res, idx);
         list_for_each_entry(lock, queue, list) {
             if (lock->ml.node != dlm->node_num) {
                 nonlocal++;
                 continue;
             }
             cookie = be64_to_cpu(lock->ml.cookie);
             mlog(0, "%s: Not migratable res %.*s, lock %u:%llu on "
                  "%s list\n", dlm->name, res->lockname.len,
                  res->lockname.name,
                  dlm_get_lock_cookie_node(cookie),
                  dlm_get_lock_cookie_seq(cookie),
                  dlm_list_in_text(idx));
             return 0;
         }
     }
 
     if (!nonlocal) {
         node_ref = find_first_bit(res->refmap, O2NM_MAX_NODES);
         if (node_ref >= O2NM_MAX_NODES)
             return 0;
     }
 
     mlog(0, "%s: res %.*s, Migratable\n", dlm->name, res->lockname.len,
          res->lockname.name);
 
     return 1;
 }
 
 /*
  * DLM_MIGRATE_LOCKRES
  */
 
 
 static int dlm_migrate_lockres(struct dlm_ctxt *dlm,
                    struct dlm_lock_resource *res, u8 target)
 {
     struct dlm_master_list_entry *mle = NULL;
     struct dlm_master_list_entry *oldmle = NULL;
     struct dlm_migratable_lockres *mres = NULL;
     int ret = 0;
     const char *name;
     unsigned int namelen;
     int mle_added = 0;
     int wake = 0;
 
     if (!dlm_grab(dlm))
         return -EINVAL;
 
     name = res->lockname.name;
     namelen = res->lockname.len;
 
     mlog(0, "%s: Migrating %.*s to node %u\n", dlm->name, namelen, name,
          target);
 
     /* preallocate up front. if this fails, abort */
     ret = -ENOMEM;
     mres = (struct dlm_migratable_lockres *) __get_free_page(GFP_NOFS);
     if (!mres) {
         mlog_errno(ret);
         goto leave;
     }
 
     mle = kmem_cache_alloc(dlm_mle_cache, GFP_NOFS);
     if (!mle) {
         mlog_errno(ret);
         goto leave;
     }
     ret = 0;
 
     /*
      * clear any existing master requests and
      * add the migration mle to the list
      */
     spin_lock(&dlm->spinlock);
     spin_lock(&dlm->master_lock);
     ret = dlm_add_migration_mle(dlm, res, mle, &oldmle, name,
                     namelen, target, dlm->node_num);
     /* get an extra reference on the mle.
      * otherwise the assert_master from the new
      * master will destroy this.
      */
     if (ret != -EEXIST)
         dlm_get_mle_inuse(mle);
 
     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 (ret != -EEXIST && 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);
             dlm_put_mle_inuse(mle);
         } else if (mle) {
             kmem_cache_free(dlm_mle_cache, mle);
             mle = NULL;
         }
         goto leave;
     }
 
     /*
      * at this point, we have a migration target, an mle
      * in the master list, and the MIGRATING flag set on
      * the lockres
      */
 
     /* now that remote nodes are spinning on the MIGRATING flag,
      * ensure that all assert_master work is flushed. */
     flush_workqueue(dlm->dlm_worker);
 
     /* notify new node and send all lock state */
     /* call send_one_lockres with migration flag.
      * this serves as notice to the target node that a
      * migration is starting. */
     ret = dlm_send_one_lockres(dlm, res, mres, target,
                    DLM_MRES_MIGRATION);
 
     if (ret < 0) {
         mlog(0, "migration to node %u failed with %d\n",
              target, ret);
         /* migration failed, detach and clean up mle */
         dlm_mle_detach_hb_events(dlm, mle);
         dlm_put_mle(mle);
         dlm_put_mle_inuse(mle);
         spin_lock(&res->spinlock);
         res->state &= ~DLM_LOCK_RES_MIGRATING;
         wake = 1;
         spin_unlock(&res->spinlock);
         if (dlm_is_host_down(ret))
             dlm_wait_for_node_death(dlm, target,
                         DLM_NODE_DEATH_WAIT_MAX);
         goto leave;
     }
 
     /* at this point, the target sends a message to all nodes,
      * (using dlm_do_migrate_request).  this node is skipped since
      * we had to put an mle in the list to begin the process.  this
      * node now waits for target to do an assert master.  this node
      * will be the last one notified, ensuring that the migration
      * is complete everywhere.  if the target dies while this is
      * going on, some nodes could potentially see the target as the
      * master, so it is important that my recovery finds the migration
      * mle and sets the master to UNKNOWN. */
 
 
     /* wait for new node to assert master */
     while (1) {
         ret = wait_event_interruptible_timeout(mle->wq,
                     (atomic_read(&mle->woken) == 1),
                     msecs_to_jiffies(5000));
 
         if (ret >= 0) {
                 if (atomic_read(&mle->woken) == 1 ||
                 res->owner == target)
                 break;
 
             mlog(0, "%s:%.*s: timed out during migration\n",
                  dlm->name, res->lockname.len, res->lockname.name);
             /* avoid hang during shutdown when migrating lockres
              * to a node which also goes down */
             if (dlm_is_node_dead(dlm, target)) {
                 mlog(0, "%s:%.*s: expected migration "
                      "target %u is no longer up, restarting\n",
                      dlm->name, res->lockname.len,
                      res->lockname.name, target);
                 ret = -EINVAL;
                 /* migration failed, detach and clean up mle */
                 dlm_mle_detach_hb_events(dlm, mle);
                 dlm_put_mle(mle);
                 dlm_put_mle_inuse(mle);
                 spin_lock(&res->spinlock);
                 res->state &= ~DLM_LOCK_RES_MIGRATING;
                 wake = 1;
                 spin_unlock(&res->spinlock);
                 goto leave;
             }
         } else
             mlog(0, "%s:%.*s: caught signal during migration\n",
                  dlm->name, res->lockname.len, res->lockname.name);
     }
 
     /* all done, set the owner, clear the flag */
     spin_lock(&res->spinlock);
     dlm_set_lockres_owner(dlm, res, target);
     res->state &= ~DLM_LOCK_RES_MIGRATING;
     dlm_remove_nonlocal_locks(dlm, res);
     spin_unlock(&res->spinlock);
     wake_up(&res->wq);
 
     /* master is known, detach if not already detached */
     dlm_mle_detach_hb_events(dlm, mle);
     dlm_put_mle_inuse(mle);
     ret = 0;
 
     dlm_lockres_calc_usage(dlm, res);
 
 leave:
     /* re-dirty the lockres if we failed */
     if (ret < 0)
         dlm_kick_thread(dlm, res);
 
     /* wake up waiters if the MIGRATING flag got set
      * but migration failed */
     if (wake)
         wake_up(&res->wq);
 
     if (mres)
         free_page((unsigned long)mres);
 
     dlm_put(dlm);
 
     mlog(0, "%s: Migrating %.*s to %u, returns %d\n", dlm->name, namelen,
          name, target, ret);
     return ret;
 }
 
 /*
  * 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)
     __must_hold(&dlm->spinlock)
 {
     int ret;
     int lock_dropped = 0;
     u8 target = O2NM_MAX_NODES;
 
     assert_spin_locked(&dlm->spinlock);
 
     spin_lock(&res->spinlock);
     if (dlm_is_lockres_migratable(dlm, res))
         target = dlm_pick_migration_target(dlm, res);
     spin_unlock(&res->spinlock);
 
     if (target == O2NM_MAX_NODES)
         goto leave;
 
     /* Wheee! Migrate lockres here! Will sleep so drop spinlock. */
     spin_unlock(&dlm->spinlock);
     lock_dropped = 1;
     ret = dlm_migrate_lockres(dlm, res, target);
     if (ret)
         mlog(0, "%s: res %.*s, Migrate to node %u failed with %d\n",
              dlm->name, res->lockname.len, res->lockname.name,
              target, ret);
     spin_lock(&dlm->spinlock);
 leave:
     return lock_dropped;
 }
 
 int dlm_lock_basts_flushed(struct dlm_ctxt *dlm, struct dlm_lock *lock)
 {
     int ret;
     spin_lock(&dlm->ast_lock);
     spin_lock(&lock->spinlock);
     ret = (list_empty(&lock->bast_list) && !lock->bast_pending);
     spin_unlock(&lock->spinlock);
     spin_unlock(&dlm->ast_lock);
     return ret;
 }
 
 static int dlm_migration_can_proceed(struct dlm_ctxt *dlm,
                      struct dlm_lock_resource *res,
                      u8 mig_target)
 {
     int can_proceed;
     spin_lock(&res->spinlock);
     can_proceed = !!(res->state & DLM_LOCK_RES_MIGRATING);
     spin_unlock(&res->spinlock);
 
     /* target has died, so make the caller break out of the
      * wait_event, but caller must recheck the domain_map */
     spin_lock(&dlm->spinlock);
     if (!test_bit(mig_target, dlm->domain_map))
         can_proceed = 1;
     spin_unlock(&dlm->spinlock);
     return can_proceed;
 }
 
 static int dlm_lockres_is_dirty(struct dlm_ctxt *dlm,
                 struct dlm_lock_resource *res)
 {
     int ret;
     spin_lock(&res->spinlock);
     ret = !!(res->state & DLM_LOCK_RES_DIRTY);
     spin_unlock(&res->spinlock);
     return ret;
 }
 
 
 static int dlm_mark_lockres_migrating(struct dlm_ctxt *dlm,
                        struct dlm_lock_resource *res,
                        u8 target)
 {
     int ret = 0;
 
     mlog(0, "dlm_mark_lockres_migrating: %.*s, from %u to %u\n",
            res->lockname.len, res->lockname.name, dlm->node_num,
            target);
     /* need to set MIGRATING flag on lockres.  this is done by
      * ensuring that all asts have been flushed for this lockres. */
     spin_lock(&res->spinlock);
     BUG_ON(res->migration_pending);
     res->migration_pending = 1;
     /* strategy is to reserve an extra ast then release
      * it below, letting the release do all of the work */
     __dlm_lockres_reserve_ast(res);
     spin_unlock(&res->spinlock);
 
     /* now flush all the pending asts */
     dlm_kick_thread(dlm, res);
     /* before waiting on DIRTY, block processes which may
      * try to dirty the lockres before MIGRATING is set */
     spin_lock(&res->spinlock);
     BUG_ON(res->state & DLM_LOCK_RES_BLOCK_DIRTY);
     res->state |= DLM_LOCK_RES_BLOCK_DIRTY;
     spin_unlock(&res->spinlock);
     /* now wait on any pending asts and the DIRTY state */
     wait_event(dlm->ast_wq, !dlm_lockres_is_dirty(dlm, res));
     dlm_lockres_release_ast(dlm, res);
 
     mlog(0, "about to wait on migration_wq, dirty=%s\n",
            res->state & DLM_LOCK_RES_DIRTY ? "yes" : "no");
     /* if the extra ref we just put was the final one, this
      * will pass thru immediately.  otherwise, we need to wait
      * for the last ast to finish. */
 again:
     ret = wait_event_interruptible_timeout(dlm->migration_wq,
            dlm_migration_can_proceed(dlm, res, target),
            msecs_to_jiffies(1000));
     if (ret < 0) {
         mlog(0, "woken again: migrating? %s, dead? %s\n",
                res->state & DLM_LOCK_RES_MIGRATING ? "yes":"no",
                test_bit(target, dlm->domain_map) ? "no":"yes");
     } else {
         mlog(0, "all is well: migrating? %s, dead? %s\n",
                res->state & DLM_LOCK_RES_MIGRATING ? "yes":"no",
                test_bit(target, dlm->domain_map) ? "no":"yes");
     }
     if (!dlm_migration_can_proceed(dlm, res, target)) {
         mlog(0, "trying again...\n");
         goto again;
     }
 
     ret = 0;
     /* did the target go down or die? */
     spin_lock(&dlm->spinlock);
     if (!test_bit(target, dlm->domain_map)) {
         mlog(ML_ERROR, "aha. migration target %u just went down\n",
              target);
         ret = -EHOSTDOWN;
     }
     spin_unlock(&dlm->spinlock);
 
     /*
      * if target is down, we need to clear DLM_LOCK_RES_BLOCK_DIRTY for
      * another try; otherwise, we are sure the MIGRATING state is there,
      * drop the unneeded state which blocked threads trying to DIRTY
      */
     spin_lock(&res->spinlock);
     BUG_ON(!(res->state & DLM_LOCK_RES_BLOCK_DIRTY));
     res->state &= ~DLM_LOCK_RES_BLOCK_DIRTY;
     if (!ret)
         BUG_ON(!(res->state & DLM_LOCK_RES_MIGRATING));
     else
         res->migration_pending = 0;
     spin_unlock(&res->spinlock);
 
     /*
      * at this point:
      *
      *   o the DLM_LOCK_RES_MIGRATING flag is set if target not down
      *   o there are no pending asts on this lockres
      *   o all processes trying to reserve an ast on this
      *     lockres must wait for the MIGRATING flag to clear
      */
     return ret;
 }
 
 /* last step in the migration process.
  * original master calls this to free all of the dlm_lock
  * structures that used to be for other nodes. */
 static void dlm_remove_nonlocal_locks(struct dlm_ctxt *dlm,
                       struct dlm_lock_resource *res)
 {
     struct list_head *queue = &res->granted;
     int i, bit;
     struct dlm_lock *lock, *next;
 
     assert_spin_locked(&res->spinlock);
 
     BUG_ON(res->owner == dlm->node_num);
 
     for (i=0; i<3; i++) {
         list_for_each_entry_safe(lock, next, queue, list) {
             if (lock->ml.node != dlm->node_num) {
                 mlog(0, "putting lock for node %u\n",
                      lock->ml.node);
                 /* be extra careful */
                 BUG_ON(!list_empty(&lock->ast_list));
                 BUG_ON(!list_empty(&lock->bast_list));
                 BUG_ON(lock->ast_pending);
                 BUG_ON(lock->bast_pending);
                 dlm_lockres_clear_refmap_bit(dlm, res,
                                  lock->ml.node);
                 list_del_init(&lock->list);
                 dlm_lock_put(lock);
                 /* In a normal unlock, we would have added a
                  * DLM_UNLOCK_FREE_LOCK action. Force it. */
                 dlm_lock_put(lock);
             }
         }
         queue++;
     }
     bit = 0;
     while (1) {
         bit = find_next_bit(res->refmap, O2NM_MAX_NODES, bit);
         if (bit >= O2NM_MAX_NODES)
             break;
         /* do not clear the local node reference, if there is a
          * process holding this, let it drop the ref itself */
         if (bit != dlm->node_num) {
             mlog(0, "%s:%.*s: node %u had a ref to this "
                  "migrating lockres, clearing\n", dlm->name,
                  res->lockname.len, res->lockname.name, bit);
             dlm_lockres_clear_refmap_bit(dlm, res, bit);
         }
         bit++;
     }
 }
 
 /*
  * Pick a node to migrate the lock resource to. This function selects a
  * potential target based first on the locks and then on refmap. It skips
  * nodes that are in the process of exiting the domain.
  */
 static u8 dlm_pick_migration_target(struct dlm_ctxt *dlm,
                     struct dlm_lock_resource *res)
 {
     enum dlm_lockres_list idx;
     struct list_head *queue;
     struct dlm_lock *lock;
     int noderef;
     u8 nodenum = O2NM_MAX_NODES;
 
     assert_spin_locked(&dlm->spinlock);
     assert_spin_locked(&res->spinlock);
 
     /* Go through all the locks */
     for (idx = DLM_GRANTED_LIST; idx <= DLM_BLOCKED_LIST; idx++) {
         queue = dlm_list_idx_to_ptr(res, idx);
         list_for_each_entry(lock, queue, list) {
             if (lock->ml.node == dlm->node_num)
                 continue;
             if (test_bit(lock->ml.node, dlm->exit_domain_map))
                 continue;
             nodenum = lock->ml.node;
             goto bail;
         }
     }
 
     /* Go thru the refmap */
     noderef = -1;
     while (1) {
         noderef = find_next_bit(res->refmap, O2NM_MAX_NODES,
                     noderef + 1);
         if (noderef >= O2NM_MAX_NODES)
             break;
         if (noderef == dlm->node_num)
             continue;
         if (test_bit(noderef, dlm->exit_domain_map))
             continue;
         nodenum = noderef;
         goto bail;
     }
 
 bail:
     return nodenum;
 }
 
 /* this is called by the new master once all lockres
  * data has been received */
 static int dlm_do_migrate_request(struct dlm_ctxt *dlm,
                   struct dlm_lock_resource *res,
                   u8 master, u8 new_master,
                   struct dlm_node_iter *iter)
 {
     struct dlm_migrate_request migrate;
     int ret, skip, status = 0;
     int nodenum;
 
     memset(&migrate, 0, sizeof(migrate));
     migrate.namelen = res->lockname.len;
     memcpy(migrate.name, res->lockname.name, migrate.namelen);
     migrate.new_master = new_master;
     migrate.master = master;
 
     ret = 0;
 
     /* send message to all nodes, except the master and myself */
     while ((nodenum = dlm_node_iter_next(iter)) >= 0) {
         if (nodenum == master ||
             nodenum == new_master)
             continue;
 
         /* We could race exit domain. If exited, skip. */
         spin_lock(&dlm->spinlock);
         skip = (!test_bit(nodenum, dlm->domain_map));
         spin_unlock(&dlm->spinlock);
         if (skip) {
             clear_bit(nodenum, iter->node_map);
             continue;
         }
 
         ret = o2net_send_message(DLM_MIGRATE_REQUEST_MSG, dlm->key,
                      &migrate, sizeof(migrate), nodenum,
                      &status);
         if (ret < 0) {
             mlog(ML_ERROR, "%s: res %.*s, Error %d send "
                  "MIGRATE_REQUEST to node %u\n", dlm->name,
                  migrate.namelen, migrate.name, ret, nodenum);
             if (!dlm_is_host_down(ret)) {
                 mlog(ML_ERROR, "unhandled error=%d!\n", ret);
                 BUG();
             }
             clear_bit(nodenum, iter->node_map);
             ret = 0;
         } else if (status < 0) {
             mlog(0, "migrate request (node %u) returned %d!\n",
                  nodenum, status);
             ret = status;
         } else if (status == DLM_MIGRATE_RESPONSE_MASTERY_REF) {
             /* during the migration request we short-circuited
              * the mastery of the lockres.  make sure we have
              * a mastery ref for nodenum */
             mlog(0, "%s:%.*s: need ref for node %u\n",
                  dlm->name, res->lockname.len, res->lockname.name,
                  nodenum);
             spin_lock(&res->spinlock);
             dlm_lockres_set_refmap_bit(dlm, res, nodenum);
             spin_unlock(&res->spinlock);
         }
     }
 
     if (ret < 0)
         mlog_errno(ret);
 
     mlog(0, "returning ret=%d\n", ret);
     return ret;
 }
 
 
 /* if there is an existing mle for this lockres, we now know who the master is.
  * (the one who sent us *this* message) we can clear it up right away.
  * since the process that put the mle on the list still has a reference to it,
  * we can unhash it now, set the master and wake the process.  as a result,
  * we will have no mle in the list to start with.  now we can add an mle for
  * the migration and this should be the only one found for those scanning the
  * list.  */
 int dlm_migrate_request_handler(struct o2net_msg *msg, u32 len, void *data,
                 void **ret_data)
 {
     struct dlm_ctxt *dlm = data;
     struct dlm_lock_resource *res = NULL;
     struct dlm_migrate_request *migrate = (struct dlm_migrate_request *) msg->buf;
     struct dlm_master_list_entry *mle = NULL, *oldmle = NULL;
     const char *name;
     unsigned int namelen, hash;
     int ret = 0;
 
     if (!dlm_grab(dlm))
         return 0;
 
     name = migrate->name;
     namelen = migrate->namelen;
     hash = dlm_lockid_hash(name, namelen);
 
     /* preallocate.. if this fails, abort */
     mle = kmem_cache_alloc(dlm_mle_cache, GFP_NOFS);
 
     if (!mle) {
         ret = -ENOMEM;
         goto leave;
     }
 
     /* check for pre-existing lock */
     spin_lock(&dlm->spinlock);
     res = __dlm_lookup_lockres(dlm, name, namelen, hash);
     if (res) {
         spin_lock(&res->spinlock);
         if (res->state & DLM_LOCK_RES_RECOVERING) {
             /* if all is working ok, this can only mean that we got
             * a migrate request from a node that we now see as
             * dead.  what can we do here?  drop it to the floor? */
             spin_unlock(&res->spinlock);
             mlog(ML_ERROR, "Got a migrate request, but the "
                  "lockres is marked as recovering!");
             kmem_cache_free(dlm_mle_cache, mle);
             ret = -EINVAL; /* need a better solution */
             goto unlock;
         }
         res->state |= DLM_LOCK_RES_MIGRATING;
         spin_unlock(&res->spinlock);
     }
 
     spin_lock(&dlm->master_lock);
     /* ignore status.  only nonzero status would BUG. */
     ret = dlm_add_migration_mle(dlm, res, mle, &oldmle,
                     name, namelen,
                     migrate->new_master,
                     migrate->master);
 
     if (ret < 0)
         kmem_cache_free(dlm_mle_cache, mle);
 
     spin_unlock(&dlm->master_lock);
 unlock:
     spin_unlock(&dlm->spinlock);
 
     if (oldmle) {
         /* master is known, detach if not already detached */
         dlm_mle_detach_hb_events(dlm, oldmle);
         dlm_put_mle(oldmle);
     }
 
     if (res)
         dlm_lockres_put(res);
 leave:
     dlm_put(dlm);
     return ret;
 }
 
 /* must be holding dlm->spinlock and dlm->master_lock
  * when adding a migration mle, we can clear any other mles
  * in the master list because we know with certainty that
  * the master is "master".  so we remove any old mle from
  * the list after setting it's master field, and then add
  * the new migration mle.  this way we can hold with the rule
  * of having only one mle for a given lock name at all times. */
 static int dlm_add_migration_mle(struct dlm_ctxt *dlm,
                  struct dlm_lock_resource *res,
                  struct dlm_master_list_entry *mle,
                  struct dlm_master_list_entry **oldmle,
                  const char *name, unsigned int namelen,
                  u8 new_master, u8 master)
 {
     int found;
     int ret = 0;
 
     *oldmle = NULL;
 
     assert_spin_locked(&dlm->spinlock);
     assert_spin_locked(&dlm->master_lock);
 
     /* caller is responsible for any ref taken here on oldmle */
     found = dlm_find_mle(dlm, oldmle, (char *)name, namelen);
     if (found) {
         struct dlm_master_list_entry *tmp = *oldmle;
         spin_lock(&tmp->spinlock);
         if (tmp->type == DLM_MLE_MIGRATION) {
             if (master == dlm->node_num) {
                 /* ah another process raced me to it */
                 mlog(0, "tried to migrate %.*s, but some "
                      "process beat me to it\n",
                      namelen, name);
                 spin_unlock(&tmp->spinlock);
                 return -EEXIST;
             } else {
                 /* bad.  2 NODES are trying to migrate! */
                 mlog(ML_ERROR, "migration error  mle: "
                      "master=%u new_master=%u // request: "
                      "master=%u new_master=%u // "
                      "lockres=%.*s\n",
                      tmp->master, tmp->new_master,
                      master, new_master,
                      namelen, name);
                 BUG();
             }
         } else {
             /* this is essentially what assert_master does */
             tmp->master = master;
             atomic_set(&tmp->woken, 1);
             wake_up(&tmp->wq);
             /* remove it so that only one mle will be found */
             __dlm_unlink_mle(dlm, tmp);
             __dlm_mle_detach_hb_events(dlm, tmp);
             if (tmp->type == DLM_MLE_MASTER) {
                 ret = DLM_MIGRATE_RESPONSE_MASTERY_REF;
                 mlog(0, "%s:%.*s: master=%u, newmaster=%u, "
                         "telling master to get ref "
                         "for cleared out mle during "
                         "migration\n", dlm->name,
                         namelen, name, master,
                         new_master);
             }
         }
         spin_unlock(&tmp->spinlock);
     }
 
     /* now add a migration mle to the tail of the list */
     dlm_init_mle(mle, DLM_MLE_MIGRATION, dlm, res, name, namelen);
     mle->new_master = new_master;
     /* the new master will be sending an assert master for this.
      * at that point we will get the refmap reference */
     mle->master = master;
     /* do this for consistency with other mle types */
     set_bit(new_master, mle->maybe_map);
     __dlm_insert_mle(dlm, mle);
 
     return ret;
 }
 
 /*
  * Sets the owner of the lockres, associated to the mle, to UNKNOWN
  */
 static struct dlm_lock_resource *dlm_reset_mleres_owner(struct dlm_ctxt *dlm,
                     struct dlm_master_list_entry *mle)
 {
     struct dlm_lock_resource *res;
 
     /* Find the lockres associated to the mle and set its owner to UNK */
     res = __dlm_lookup_lockres(dlm, mle->mname, mle->mnamelen,
                    mle->mnamehash);
     if (res) {
         spin_unlock(&dlm->master_lock);
 
         /* move lockres onto recovery list */
         spin_lock(&res->spinlock);
         dlm_set_lockres_owner(dlm, res, DLM_LOCK_RES_OWNER_UNKNOWN);
         dlm_move_lockres_to_recovery_list(dlm, res);
         spin_unlock(&res->spinlock);
         dlm_lockres_put(res);
 
         /* about to get rid of mle, detach from heartbeat */
         __dlm_mle_detach_hb_events(dlm, mle);
 
         /* dump the mle */
         spin_lock(&dlm->master_lock);
         __dlm_put_mle(mle);
         spin_unlock(&dlm->master_lock);
     }
 
     return res;
 }
 
 static void dlm_clean_migration_mle(struct dlm_ctxt *dlm,
                     struct dlm_master_list_entry *mle)
 {
     __dlm_mle_detach_hb_events(dlm, mle);
 
     spin_lock(&mle->spinlock);
     __dlm_unlink_mle(dlm, mle);
     atomic_set(&mle->woken, 1);
     spin_unlock(&mle->spinlock);
 
     wake_up(&mle->wq);
 }
 
 static void dlm_clean_block_mle(struct dlm_ctxt *dlm,
                 struct dlm_master_list_entry *mle, u8 dead_node)
 {
     int bit;
 
     BUG_ON(mle->type != DLM_MLE_BLOCK);
 
     spin_lock(&mle->spinlock);
     bit = find_first_bit(mle->maybe_map, O2NM_MAX_NODES);
     if (bit != dead_node) {
         mlog(0, "mle found, but dead node %u would not have been "
              "master\n", dead_node);
         spin_unlock(&mle->spinlock);
     } else {
         /* Must drop the refcount by one since the assert_master will
          * never arrive. This may result in the mle being unlinked and
          * freed, but there may still be a process waiting in the
          * dlmlock path which is fine. */
         mlog(0, "node %u was expected master\n", dead_node);
         atomic_set(&mle->woken, 1);
         spin_unlock(&mle->spinlock);
         wake_up(&mle->wq);
 
         /* Do not need events any longer, so detach from heartbeat */
         __dlm_mle_detach_hb_events(dlm, mle);
         __dlm_put_mle(mle);
     }
 }
 
 void dlm_clean_master_list(struct dlm_ctxt *dlm, u8 dead_node)
 {
     struct dlm_master_list_entry *mle;
     struct dlm_lock_resource *res;
     struct hlist_head *bucket;
     struct hlist_node *tmp;
     unsigned int i;
 
     mlog(0, "dlm=%s, dead node=%u\n", dlm->name, dead_node);
 top:
     assert_spin_locked(&dlm->spinlock);
 
     /* clean the master list */
     spin_lock(&dlm->master_lock);
     for (i = 0; i < DLM_HASH_BUCKETS; i++) {
         bucket = dlm_master_hash(dlm, i);
         hlist_for_each_entry_safe(mle, tmp, bucket, master_hash_node) {
             BUG_ON(mle->type != DLM_MLE_BLOCK &&
                    mle->type != DLM_MLE_MASTER &&
                    mle->type != DLM_MLE_MIGRATION);
 
             /* MASTER mles are initiated locally. The waiting
              * process will notice the node map change shortly.
              * Let that happen as normal. */
             if (mle->type == DLM_MLE_MASTER)
                 continue;
 
             /* BLOCK mles are initiated by other nodes. Need to
              * clean up if the dead node would have been the
              * master. */
             if (mle->type == DLM_MLE_BLOCK) {
                 dlm_clean_block_mle(dlm, mle, dead_node);
                 continue;
             }
 
             /* Everything else is a MIGRATION mle */
 
             /* The rule for MIGRATION mles is that the master
              * becomes UNKNOWN if *either* the original or the new
              * master dies. All UNKNOWN lockres' are sent to
              * whichever node becomes the recovery master. The new
              * master is responsible for determining if there is
              * still a master for this lockres, or if he needs to
              * take over mastery. Either way, this node should
              * expect another message to resolve this. */
 
             if (mle->master != dead_node &&
                 mle->new_master != dead_node)
                 continue;
 
             if (mle->new_master == dead_node && mle->inuse) {
                 mlog(ML_NOTICE, "%s: target %u died during "
                         "migration from %u, the MLE is "
                         "still keep used, ignore it!\n",
                         dlm->name, dead_node,
                         mle->master);
                 continue;
             }
 
             /* If we have reached this point, this mle needs to be
              * removed from the list and freed. */
             dlm_clean_migration_mle(dlm, mle);
 
             mlog(0, "%s: node %u died during migration from "
                  "%u to %u!\n", dlm->name, dead_node, mle->master,
                  mle->new_master);
 
             /* If we find a lockres associated with the mle, we've
              * hit this rare case that messes up our lock ordering.
              * If so, we need to drop the master lock so that we can
              * take the lockres lock, meaning that we will have to
              * restart from the head of list. */
             res = dlm_reset_mleres_owner(dlm, mle);
             if (res)
                 /* restart */
                 goto top;
 
             /* This may be the last reference */
             __dlm_put_mle(mle);
         }
     }
     spin_unlock(&dlm->master_lock);
 }
 
 int dlm_finish_migration(struct dlm_ctxt *dlm, struct dlm_lock_resource *res,
              u8 old_master)
 {
     struct dlm_node_iter iter;
     int ret = 0;
 
     spin_lock(&dlm->spinlock);
     dlm_node_iter_init(dlm->domain_map, &iter);
     clear_bit(old_master, iter.node_map);
     clear_bit(dlm->node_num, iter.node_map);
     spin_unlock(&dlm->spinlock);
 
     /* ownership of the lockres is changing.  account for the
      * mastery reference here since old_master will briefly have
      * a reference after the migration completes */
     spin_lock(&res->spinlock);
     dlm_lockres_set_refmap_bit(dlm, res, old_master);
     spin_unlock(&res->spinlock);
 
     mlog(0, "now time to do a migrate request to other nodes\n");
     ret = dlm_do_migrate_request(dlm, res, old_master,
                      dlm->node_num, &iter);
     if (ret < 0) {
         mlog_errno(ret);
         goto leave;
     }
 
     mlog(0, "doing assert master of %.*s to all except the original node\n",
          res->lockname.len, res->lockname.name);
     /* this call now finishes out the nodemap
      * even if one or more nodes die */
     ret = dlm_do_assert_master(dlm, res, iter.node_map,
                    DLM_ASSERT_MASTER_FINISH_MIGRATION);
     if (ret < 0) {
         /* no longer need to retry.  all living nodes contacted. */
         mlog_errno(ret);
         ret = 0;
     }
 
     memset(iter.node_map, 0, sizeof(iter.node_map));
     set_bit(old_master, iter.node_map);
     mlog(0, "doing assert master of %.*s back to %u\n",
          res->lockname.len, res->lockname.name, old_master);
     ret = dlm_do_assert_master(dlm, res, iter.node_map,
                    DLM_ASSERT_MASTER_FINISH_MIGRATION);
     if (ret < 0) {
         mlog(0, "assert master to original master failed "
              "with %d.\n", ret);
         /* the only nonzero status here would be because of
          * a dead original node.  we're done. */
         ret = 0;
     }
 
     /* all done, set the owner, clear the flag */
     spin_lock(&res->spinlock);
     dlm_set_lockres_owner(dlm, res, dlm->node_num);
     res->state &= ~DLM_LOCK_RES_MIGRATING;
     spin_unlock(&res->spinlock);
     /* re-dirty it on the new master */
     dlm_kick_thread(dlm, res);
     wake_up(&res->wq);
 leave:
     return ret;
 }
 
 /*
  * LOCKRES AST REFCOUNT
  * this is integral to migration
  */
 
 /* for future intent to call an ast, reserve one ahead of time.
  * this should be called only after waiting on the lockres
  * with dlm_wait_on_lockres, and while still holding the
  * spinlock after the call. */
 void __dlm_lockres_reserve_ast(struct dlm_lock_resource *res)
 {
     assert_spin_locked(&res->spinlock);
     if (res->state & DLM_LOCK_RES_MIGRATING) {
         __dlm_print_one_lock_resource(res);
     }
     BUG_ON(res->state & DLM_LOCK_RES_MIGRATING);
 
     atomic_inc(&res->asts_reserved);
 }
 
 /*
  * used to drop the reserved ast, either because it went unused,
  * or because the ast/bast was actually called.
  *
  * also, if there is a pending migration on this lockres,
  * and this was the last pending ast on the lockres,
  * atomically set the MIGRATING flag before we drop the lock.
  * this is how we ensure that migration can proceed with no
  * asts in progress.  note that it is ok if the state of the
  * queues is such that a lock should be granted in the future
  * or that a bast should be fired, because the new master will
  * shuffle the lists on this lockres as soon as it is migrated.
  */
 void dlm_lockres_release_ast(struct dlm_ctxt *dlm,
                  struct dlm_lock_resource *res)
 {
     if (!atomic_dec_and_lock(&res->asts_reserved, &res->spinlock))
         return;
 
     if (!res->migration_pending) {
         spin_unlock(&res->spinlock);
         return;
     }
 
     BUG_ON(res->state & DLM_LOCK_RES_MIGRATING);
     res->migration_pending = 0;
     res->state |= DLM_LOCK_RES_MIGRATING;
     spin_unlock(&res->spinlock);
     wake_up(&res->wq);
     wake_up(&dlm->migration_wq);
 }
 
 void dlm_force_free_mles(struct dlm_ctxt *dlm)
 {
     int i;
     struct hlist_head *bucket;
     struct dlm_master_list_entry *mle;
     struct hlist_node *tmp;
 
     /*
      * We notified all other nodes that we are exiting the domain and
      * marked the dlm state to DLM_CTXT_LEAVING. If any mles are still
      * around we force free them and wake any processes that are waiting
      * on the mles
      */
     spin_lock(&dlm->spinlock);
     spin_lock(&dlm->master_lock);
 
     BUG_ON(dlm->dlm_state != DLM_CTXT_LEAVING);
     BUG_ON((find_first_bit(dlm->domain_map, O2NM_MAX_NODES) < O2NM_MAX_NODES));
 
     for (i = 0; i < DLM_HASH_BUCKETS; i++) {
         bucket = dlm_master_hash(dlm, i);
         hlist_for_each_entry_safe(mle, tmp, bucket, master_hash_node) {
             if (mle->type != DLM_MLE_BLOCK) {
                 mlog(ML_ERROR, "bad mle: %p\n", mle);
                 dlm_print_one_mle(mle);
             }
             atomic_set(&mle->woken, 1);
             wake_up(&mle->wq);
 
             __dlm_unlink_mle(dlm, mle);
             __dlm_mle_detach_hb_events(dlm, mle);
             __dlm_put_mle(mle);
         }
     }
     spin_unlock(&dlm->master_lock);
     spin_unlock(&dlm->spinlock);
 }