ocfs2_dlm: fix cluster-wide refcounting of lock resources

This was previously broken and migration of some locks had to be temporarily
disabled. We use a new (and backward-incompatible) set of network messages
to account for all references to a lock resources held across the cluster.
once these are all freed, the master node may then free the lock resource
memory once its local references are dropped.

Signed-off-by: Kurt Hackel <kurt.hackel@oracle.com>
Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>

8 files changed, 729 insertions, 174 deletions

diff --git a/fs/ocfs2/cluster/tcp_internal.h b/fs/ocfs2/cluster/tcp_internal.h
index b700dc9624d1..775c911342f4 100644
--- a/fs/ocfs2/cluster/tcp_internal.h
+++ b/fs/ocfs2/cluster/tcp_internal.h
@@ -38,6 +38,9 @@
  * locking semantics of the file system using the protocol.  It should 
  * be somewhere else, I'm sure, but right now it isn't.
  *
+ * New in version 6:
+ *      - DLM lockres remote refcount fixes.
+ *
  * New in version 5:
  *      - Network timeout checking protocol
  *
@@ -51,7 +54,7 @@
  *      - full 64 bit i_size in the metadata lock lvbs
  *      - introduction of "rw" lock and pushing meta/data locking down
  */
-#define O2NET_PROTOCOL_VERSION 5ULL
+#define O2NET_PROTOCOL_VERSION 6ULL
 struct o2net_handshake {
         __be64  protocol_version;
         __be64  connector_id;
diff --git a/fs/ocfs2/dlm/dlmcommon.h b/fs/ocfs2/dlm/dlmcommon.h
index 6b6ff76538c5..9fa427119a3c 100644
--- a/fs/ocfs2/dlm/dlmcommon.h
+++ b/fs/ocfs2/dlm/dlmcommon.h
@@ -222,6 +222,7 @@ static inline void __dlm_set_joining_node(struct dlm_ctxt *dlm,
 #define DLM_LOCK_RES_DIRTY                0x00000008
 #define DLM_LOCK_RES_IN_PROGRESS          0x00000010
 #define DLM_LOCK_RES_MIGRATING            0x00000020
+#define DLM_LOCK_RES_DROPPING_REF         0x00000040
 
 /* max milliseconds to wait to sync up a network failure with a node death */
 #define DLM_NODE_DEATH_WAIT_MAX (5 * 1000)
@@ -265,6 +266,8 @@ struct dlm_lock_resource
         u8  owner;              //node which owns the lock resource, or unknown
         u16 state;
         char lvb[DLM_LVB_LEN];
+        unsigned int inflight_locks;
+        unsigned long refmap[BITS_TO_LONGS(O2NM_MAX_NODES)];
 };
 
 struct dlm_migratable_lock
@@ -367,7 +370,7 @@ enum {
         DLM_CONVERT_LOCK_MSG,    /* 504 */
         DLM_PROXY_AST_MSG,       /* 505 */
         DLM_UNLOCK_LOCK_MSG,     /* 506 */
-        DLM_UNUSED_MSG2,         /* 507 */
+        DLM_DEREF_LOCKRES_MSG,   /* 507 */
         DLM_MIGRATE_REQUEST_MSG, /* 508 */
         DLM_MIG_LOCKRES_MSG,     /* 509 */
         DLM_QUERY_JOIN_MSG,      /* 510 */
@@ -417,6 +420,9 @@ struct dlm_master_request
         u8 name[O2NM_MAX_NAME_LEN];
 };
 
+#define DLM_ASSERT_RESPONSE_REASSERT       0x00000001
+#define DLM_ASSERT_RESPONSE_MASTERY_REF    0x00000002
+
 #define DLM_ASSERT_MASTER_MLE_CLEANUP      0x00000001
 #define DLM_ASSERT_MASTER_REQUERY          0x00000002
 #define DLM_ASSERT_MASTER_FINISH_MIGRATION 0x00000004
@@ -430,6 +436,8 @@ struct dlm_assert_master
         u8 name[O2NM_MAX_NAME_LEN];
 };
 
+#define DLM_MIGRATE_RESPONSE_MASTERY_REF   0x00000001
+
 struct dlm_migrate_request
 {
         u8 master;
@@ -648,6 +656,16 @@ struct dlm_finalize_reco
         __be32 pad2;
 };
 
+struct dlm_deref_lockres
+{
+        u32 pad1;
+        u16 pad2;
+        u8 node_idx;
+        u8 namelen;
+
+        u8 name[O2NM_MAX_NAME_LEN];
+};
+
 static inline enum dlm_status
 __dlm_lockres_state_to_status(struct dlm_lock_resource *res)
 {
@@ -721,8 +739,8 @@ void __dlm_lockres_calc_usage(struct dlm_ctxt *dlm,
                               struct dlm_lock_resource *res);
 void dlm_lockres_calc_usage(struct dlm_ctxt *dlm,
                             struct dlm_lock_resource *res);
-void dlm_purge_lockres(struct dlm_ctxt *dlm,
-                       struct dlm_lock_resource *lockres);
+int dlm_purge_lockres(struct dlm_ctxt *dlm,
+                      struct dlm_lock_resource *lockres);
 static inline void dlm_lockres_get(struct dlm_lock_resource *res)
 {
         /* This is called on every lookup, so it might be worth
@@ -733,6 +751,10 @@ void dlm_lockres_put(struct dlm_lock_resource *res);
 void __dlm_unhash_lockres(struct dlm_lock_resource *res);
 void __dlm_insert_lockres(struct dlm_ctxt *dlm,
                           struct dlm_lock_resource *res);
+struct dlm_lock_resource * __dlm_lookup_lockres_full(struct dlm_ctxt *dlm,
+                                                     const char *name,
+                                                     unsigned int len,
+                                                     unsigned int hash);
 struct dlm_lock_resource * __dlm_lookup_lockres(struct dlm_ctxt *dlm,
                                                 const char *name,
                                                 unsigned int len,
@@ -753,6 +775,47 @@ struct dlm_lock_resource *dlm_new_lockres(struct dlm_ctxt *dlm,
                                           const char *name,
                                           unsigned int namelen);
 
+#define dlm_lockres_set_refmap_bit(bit,res)  \
+        __dlm_lockres_set_refmap_bit(bit,res,__FILE__,__LINE__)
+#define dlm_lockres_clear_refmap_bit(bit,res)  \
+        __dlm_lockres_clear_refmap_bit(bit,res,__FILE__,__LINE__)
+
+static inline void __dlm_lockres_set_refmap_bit(int bit,
+                                                struct dlm_lock_resource *res,
+                                                const char *file,
+                                                int line)
+{
+        //printk("%s:%d:%.*s: setting bit %d\n", file, line,
+        //     res->lockname.len, res->lockname.name, bit);
+        set_bit(bit, res->refmap);
+}
+
+static inline void __dlm_lockres_clear_refmap_bit(int bit,
+                                                  struct dlm_lock_resource *res,
+                                                  const char *file,
+                                                  int line)
+{
+        //printk("%s:%d:%.*s: clearing bit %d\n", file, line,
+        //     res->lockname.len, res->lockname.name, bit);
+        clear_bit(bit, res->refmap);
+}
+
+void __dlm_lockres_drop_inflight_ref(struct dlm_ctxt *dlm,
+                                   struct dlm_lock_resource *res,
+                                   const char *file,
+                                   int line);
+void __dlm_lockres_grab_inflight_ref(struct dlm_ctxt *dlm,
+                                   struct dlm_lock_resource *res,
+                                   int new_lockres,
+                                   const char *file,
+                                   int line);
+#define dlm_lockres_drop_inflight_ref(d,r)  \
+        __dlm_lockres_drop_inflight_ref(d,r,__FILE__,__LINE__)
+#define dlm_lockres_grab_inflight_ref(d,r)  \
+        __dlm_lockres_grab_inflight_ref(d,r,0,__FILE__,__LINE__)
+#define dlm_lockres_grab_inflight_ref_new(d,r)  \
+        __dlm_lockres_grab_inflight_ref(d,r,1,__FILE__,__LINE__)
+
 void dlm_queue_ast(struct dlm_ctxt *dlm, struct dlm_lock *lock);
 void dlm_queue_bast(struct dlm_ctxt *dlm, struct dlm_lock *lock);
 void dlm_do_local_ast(struct dlm_ctxt *dlm,
@@ -805,6 +868,7 @@ int dlm_lockres_is_dirty(struct dlm_ctxt *dlm, struct dlm_lock_resource *res);
 int dlm_migrate_lockres(struct dlm_ctxt *dlm,
                         struct dlm_lock_resource *res,
                         u8 target);
+int dlm_empty_lockres(struct dlm_ctxt *dlm, struct dlm_lock_resource *res);
 int dlm_finish_migration(struct dlm_ctxt *dlm,
                          struct dlm_lock_resource *res,
                          u8 old_master);
@@ -814,6 +878,7 @@ void __dlm_lockres_reserve_ast(struct dlm_lock_resource *res);
 
 int dlm_master_request_handler(struct o2net_msg *msg, u32 len, void *data);
 int dlm_assert_master_handler(struct o2net_msg *msg, u32 len, void *data);
+int dlm_deref_lockres_handler(struct o2net_msg *msg, u32 len, void *data);
 int dlm_migrate_request_handler(struct o2net_msg *msg, u32 len, void *data);
 int dlm_mig_lockres_handler(struct o2net_msg *msg, u32 len, void *data);
 int dlm_master_requery_handler(struct o2net_msg *msg, u32 len, void *data);
@@ -856,10 +921,12 @@ static inline void __dlm_wait_on_lockres(struct dlm_lock_resource *res)
 int dlm_init_mle_cache(void);
 void dlm_destroy_mle_cache(void);
 void dlm_hb_event_notify_attached(struct dlm_ctxt *dlm, int idx, int node_up);
+int dlm_drop_lockres_ref(struct dlm_ctxt *dlm,
+                         struct dlm_lock_resource *res);
 void dlm_clean_master_list(struct dlm_ctxt *dlm,
                            u8 dead_node);
 int dlm_lock_basts_flushed(struct dlm_ctxt *dlm, struct dlm_lock *lock);
-
+int __dlm_lockres_has_locks(struct dlm_lock_resource *res);
 int __dlm_lockres_unused(struct dlm_lock_resource *res);
 
 static inline const char * dlm_lock_mode_name(int mode)
diff --git a/fs/ocfs2/dlm/dlmdebug.c b/fs/ocfs2/dlm/dlmdebug.c
index 3f6c8d88f7af..1015cc7bf9cb 100644
--- a/fs/ocfs2/dlm/dlmdebug.c
+++ b/fs/ocfs2/dlm/dlmdebug.c
@@ -53,6 +53,23 @@ void dlm_print_one_lock_resource(struct dlm_lock_resource *res)
         spin_unlock(&res->spinlock);
 }
 
+static void dlm_print_lockres_refmap(struct dlm_lock_resource *res)
+{
+        int bit;
+        assert_spin_locked(&res->spinlock);
+
+        mlog(ML_NOTICE, "  refmap nodes: [ ");
+        bit = 0;
+        while (1) {
+                bit = find_next_bit(res->refmap, O2NM_MAX_NODES, bit);
+                if (bit >= O2NM_MAX_NODES)
+                        break;
+                printk("%u ", bit);
+                bit++;
+        }
+        printk("], inflight=%u\n", res->inflight_locks);
+}
+
 void __dlm_print_one_lock_resource(struct dlm_lock_resource *res)
 {
         struct list_head *iter2;
@@ -65,6 +82,7 @@ void __dlm_print_one_lock_resource(struct dlm_lock_resource *res)
                res->owner, res->state);
         mlog(ML_NOTICE, "  last used: %lu, on purge list: %s\n",
              res->last_used, list_empty(&res->purge) ? "no" : "yes");
+        dlm_print_lockres_refmap(res);
         mlog(ML_NOTICE, "  granted queue: \n");
         list_for_each(iter2, &res->granted) {
                 lock = list_entry(iter2, struct dlm_lock, list);
diff --git a/fs/ocfs2/dlm/dlmdomain.c b/fs/ocfs2/dlm/dlmdomain.c
index f0b25f2dd205..3995de360264 100644
--- a/fs/ocfs2/dlm/dlmdomain.c
+++ b/fs/ocfs2/dlm/dlmdomain.c
@@ -125,10 +125,10 @@ void __dlm_insert_lockres(struct dlm_ctxt *dlm,
         hlist_add_head(&res->hash_node, bucket);
 }
 
-struct dlm_lock_resource * __dlm_lookup_lockres(struct dlm_ctxt *dlm,
-                                                const char *name,
-                                                unsigned int len,
-                                                unsigned int hash)
+struct dlm_lock_resource * __dlm_lookup_lockres_full(struct dlm_ctxt *dlm,
+                                                     const char *name,
+                                                     unsigned int len,
+                                                     unsigned int hash)
 {
         struct hlist_head *bucket;
         struct hlist_node *list;
@@ -154,6 +154,37 @@ struct dlm_lock_resource * __dlm_lookup_lockres(struct dlm_ctxt *dlm,
         return NULL;
 }
 
+/* intended to be called by functions which do not care about lock
+ * resources which are being purged (most net _handler functions).
+ * this will return NULL for any lock resource which is found but
+ * currently in the process of dropping its mastery reference.
+ * use __dlm_lookup_lockres_full when you need the lock resource
+ * regardless (e.g. dlm_get_lock_resource) */
+struct dlm_lock_resource * __dlm_lookup_lockres(struct dlm_ctxt *dlm,
+                                                const char *name,
+                                                unsigned int len,
+                                                unsigned int hash)
+{
+        struct dlm_lock_resource *res = NULL;
+
+        mlog_entry("%.*s\n", len, name);
+
+        assert_spin_locked(&dlm->spinlock);
+
+        res = __dlm_lookup_lockres_full(dlm, name, len, hash);
+        if (res) {
+                spin_lock(&res->spinlock);
+                if (res->state & DLM_LOCK_RES_DROPPING_REF) {
+                        spin_unlock(&res->spinlock);
+                        dlm_lockres_put(res);
+                        return NULL;
+                }
+                spin_unlock(&res->spinlock);
+        }
+
+        return res;
+}
+
 struct dlm_lock_resource * dlm_lookup_lockres(struct dlm_ctxt *dlm,
                                     const char *name,
                                     unsigned int len)
@@ -330,43 +361,60 @@ static void dlm_complete_dlm_shutdown(struct dlm_ctxt *dlm)
         wake_up(&dlm_domain_events);
 }
 
-static void dlm_migrate_all_locks(struct dlm_ctxt *dlm)
+static int dlm_migrate_all_locks(struct dlm_ctxt *dlm)
 {
-        int i;
+        int i, num, n, ret = 0;
         struct dlm_lock_resource *res;
+        struct hlist_node *iter;
+        struct hlist_head *bucket;
+        int dropped;
 
         mlog(0, "Migrating locks from domain %s\n", dlm->name);
-restart:
+
+        num = 0;
         spin_lock(&dlm->spinlock);
         for (i = 0; i < DLM_HASH_BUCKETS; i++) {
-                while (!hlist_empty(dlm_lockres_hash(dlm, i))) {
-                        res = hlist_entry(dlm_lockres_hash(dlm, i)->first,
-                                          struct dlm_lock_resource, hash_node);
-                        /* need reference when manually grabbing lockres */
+redo_bucket:
+                n = 0;
+                bucket = dlm_lockres_hash(dlm, i);
+                iter = bucket->first;
+                while (iter) {
+                        n++;
+                        res = hlist_entry(iter, struct dlm_lock_resource,
+                                          hash_node);
                         dlm_lockres_get(res);
-                        /* this should unhash the lockres
-                         * and exit with dlm->spinlock */
-                        mlog(0, "purging res=%p\n", res);
-                        if (dlm_lockres_is_dirty(dlm, res)) {
-                                /* HACK!  this should absolutely go.
-                                 * need to figure out why some empty
-                                 * lockreses are still marked dirty */
-                                mlog(ML_ERROR, "lockres %.*s dirty!\n",
-                                     res->lockname.len, res->lockname.name);
-
-                                spin_unlock(&dlm->spinlock);
-                                dlm_kick_thread(dlm, res);
-                                wait_event(dlm->ast_wq, !dlm_lockres_is_dirty(dlm, res));
-                                dlm_lockres_put(res);
-                                goto restart;
-                        }
-                        dlm_purge_lockres(dlm, res);
+                        /* migrate, if necessary.  this will drop the dlm
+                         * spinlock and retake it if it does migration. */
+                        dropped = dlm_empty_lockres(dlm, res);
+
+                        spin_lock(&res->spinlock);
+                        __dlm_lockres_calc_usage(dlm, res);
+                        iter = res->hash_node.next;
+                        spin_unlock(&res->spinlock);
+
                         dlm_lockres_put(res);
+
+                        cond_resched_lock(&dlm->spinlock);
+
+                        if (dropped)
+                                goto redo_bucket;
                 }
+                num += n;
+                mlog(0, "%s: touched %d lockreses in bucket %d "
+                     "(tot=%d)\n", dlm->name, n, i, num);
         }
         spin_unlock(&dlm->spinlock);
-
+        wake_up(&dlm->dlm_thread_wq);
+
+        /* let the dlm thread take care of purging, keep scanning until
+         * nothing remains in the hash */
+        if (num) {
+                mlog(0, "%s: %d lock resources in hash last pass\n",
+                     dlm->name, num);
+                ret = -EAGAIN;
+        }
         mlog(0, "DONE Migrating locks from domain %s\n", dlm->name);
+        return ret;
 }
 
 static int dlm_no_joining_node(struct dlm_ctxt *dlm)
@@ -571,7 +619,9 @@ void dlm_unregister_domain(struct dlm_ctxt *dlm)
                 /* We changed dlm state, notify the thread */
                 dlm_kick_thread(dlm, NULL);
 
-                dlm_migrate_all_locks(dlm);
+                while (dlm_migrate_all_locks(dlm)) {
+                        mlog(0, "%s: more migration to do\n", dlm->name);
+                }
                 dlm_mark_domain_leaving(dlm);
                 dlm_leave_domain(dlm);
                 dlm_complete_dlm_shutdown(dlm);
@@ -1082,6 +1132,13 @@ static int dlm_register_domain_handlers(struct dlm_ctxt *dlm)
         if (status)
                 goto bail;
 
+        status = o2net_register_handler(DLM_DEREF_LOCKRES_MSG, dlm->key,
+                                        sizeof(struct dlm_deref_lockres),
+                                        dlm_deref_lockres_handler,
+                                        dlm, &dlm->dlm_domain_handlers);
+        if (status)
+                goto bail;
+
         status = o2net_register_handler(DLM_MIGRATE_REQUEST_MSG, dlm->key,
                                         sizeof(struct dlm_migrate_request),
                                         dlm_migrate_request_handler,
diff --git a/fs/ocfs2/dlm/dlmlock.c b/fs/ocfs2/dlm/dlmlock.c
index e5ca3db197f6..ac91a76b1e78 100644
--- a/fs/ocfs2/dlm/dlmlock.c
+++ b/fs/ocfs2/dlm/dlmlock.c
@@ -163,6 +163,10 @@ static enum dlm_status dlmlock_master(struct dlm_ctxt *dlm,
                         kick_thread = 1;
                 }
         }
+        /* reduce the inflight count, this may result in the lockres
+         * being purged below during calc_usage */
+        if (lock->ml.node == dlm->node_num)
+                dlm_lockres_drop_inflight_ref(dlm, res);
 
         spin_unlock(&res->spinlock);
         wake_up(&res->wq);
diff --git a/fs/ocfs2/dlm/dlmmaster.c b/fs/ocfs2/dlm/dlmmaster.c
index 0ad872055cb3..4645ec2e0fc3 100644
--- a/fs/ocfs2/dlm/dlmmaster.c
+++ b/fs/ocfs2/dlm/dlmmaster.c
@@ -99,9 +99,9 @@ static void dlm_mle_node_up(struct dlm_ctxt *dlm,
                             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, const char *lockname,
-                                unsigned int namelen, void *nodemap,
-                                u32 flags);
+static int dlm_do_assert_master(struct dlm_ctxt *dlm,
+                                struct dlm_lock_resource *res,
+                                void *nodemap, u32 flags);
 
 static inline int dlm_mle_equal(struct dlm_ctxt *dlm,
                                 struct dlm_master_list_entry *mle,
@@ -237,7 +237,8 @@ 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_master_list_entry *mle, int to);
+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,
@@ -687,6 +688,7 @@ static void dlm_init_lockres(struct dlm_ctxt *dlm,
         INIT_LIST_HEAD(&res->purge);
         atomic_set(&res->asts_reserved, 0);
         res->migration_pending = 0;
+        res->inflight_locks = 0;
 
         kref_init(&res->refs);
 
@@ -700,6 +702,7 @@ static void dlm_init_lockres(struct dlm_ctxt *dlm,
         res->last_used = 0;
 
         memset(res->lvb, 0, DLM_LVB_LEN);
+        memset(res->refmap, 0, sizeof(res->refmap));
 }
 
 struct dlm_lock_resource *dlm_new_lockres(struct dlm_ctxt *dlm,
@@ -722,6 +725,42 @@ struct dlm_lock_resource *dlm_new_lockres(struct dlm_ctxt *dlm,
         return res;
 }
 
+void __dlm_lockres_grab_inflight_ref(struct dlm_ctxt *dlm,
+                                   struct dlm_lock_resource *res,
+                                   int new_lockres,
+                                   const char *file,
+                                   int line)
+{
+        if (!new_lockres)
+                assert_spin_locked(&res->spinlock);
+
+        if (!test_bit(dlm->node_num, res->refmap)) {
+                BUG_ON(res->inflight_locks != 0);
+                dlm_lockres_set_refmap_bit(dlm->node_num, res);
+        }
+        res->inflight_locks++;
+        mlog(0, "%s:%.*s: inflight++: now %u\n",
+             dlm->name, res->lockname.len, res->lockname.name,
+             res->inflight_locks);
+}
+
+void __dlm_lockres_drop_inflight_ref(struct dlm_ctxt *dlm,
+                                   struct dlm_lock_resource *res,
+                                   const char *file,
+                                   int line)
+{
+        assert_spin_locked(&res->spinlock);
+
+        BUG_ON(res->inflight_locks == 0);
+        res->inflight_locks--;
+        mlog(0, "%s:%.*s: inflight--: now %u\n",
+             dlm->name, res->lockname.len, res->lockname.name,
+             res->inflight_locks);
+        if (res->inflight_locks == 0)
+                dlm_lockres_clear_refmap_bit(dlm->node_num, res);
+        wake_up(&res->wq);
+}
+
 /*
  * lookup a lock resource by name.
  * may already exist in the hashtable.
@@ -752,6 +791,7 @@ struct dlm_lock_resource * dlm_get_lock_resource(struct dlm_ctxt *dlm,
         unsigned int hash;
         int tries = 0;
         int bit, wait_on_recovery = 0;
+        int drop_inflight_if_nonlocal = 0;
 
         BUG_ON(!lockid);
 
@@ -761,9 +801,30 @@ struct dlm_lock_resource * dlm_get_lock_resource(struct dlm_ctxt *dlm,
 
 lookup:
         spin_lock(&dlm->spinlock);
-        tmpres = __dlm_lookup_lockres(dlm, lockid, namelen, hash);
+        tmpres = __dlm_lookup_lockres_full(dlm, lockid, namelen, hash);
         if (tmpres) {
+                int dropping_ref = 0;
+
+                spin_lock(&tmpres->spinlock);
+                if (tmpres->owner == dlm->node_num) {
+                        BUG_ON(tmpres->state & DLM_LOCK_RES_DROPPING_REF);
+                        dlm_lockres_grab_inflight_ref(dlm, tmpres);
+                } else if (tmpres->state & DLM_LOCK_RES_DROPPING_REF)
+                        dropping_ref = 1;
+                spin_unlock(&tmpres->spinlock);
                 spin_unlock(&dlm->spinlock);
+
+                /* wait until done messaging the master, drop our ref to allow
+                 * the lockres to be purged, start over. */
+                if (dropping_ref) {
+                        spin_lock(&tmpres->spinlock);
+                        __dlm_wait_on_lockres_flags(tmpres, DLM_LOCK_RES_DROPPING_REF);
+                        spin_unlock(&tmpres->spinlock);
+                        dlm_lockres_put(tmpres);
+                        tmpres = NULL;
+                        goto lookup;
+                }
+
                 mlog(0, "found in hash!\n");
                 if (res)
                         dlm_lockres_put(res);
@@ -793,6 +854,7 @@ lookup:
                 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 */
@@ -805,29 +867,40 @@ lookup:
         /* 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();
-                } else if (mle->type == DLM_MLE_MIGRATION) {
-                        /* migration is in progress! */
-                        /* the good news is that we now know the
-                         * "current" master (mle->master). */
-
+                }
+                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);
-                        assert_spin_locked(&dlm->spinlock);
-
-                        /* set the lockres owner and hash it */
-                        spin_lock(&res->spinlock);
-                        dlm_set_lockres_owner(dlm, res, mle->master);
-                        __dlm_insert_lockres(dlm, res);
-                        spin_unlock(&res->spinlock);
                         spin_unlock(&dlm->spinlock);
 
                         /* master is known, detach */
-                        dlm_mle_detach_hb_events(dlm, mle);
+                        if (!mig)
+                                dlm_mle_detach_hb_events(dlm, mle);
                         dlm_put_mle(mle);
                         mle = NULL;
-                        goto wake_waiters;
+                        /* this is lame, but we cant wait on either
+                         * the mle or lockres waitqueue here */
+                        if (mig)
+                                msleep(100);
+                        goto lookup;
                 }
         } else {
                 /* go ahead and try to master lock on this node */
@@ -858,6 +931,13 @@ lookup:
 
         /* finally add the lockres to its hash bucket */
         __dlm_insert_lockres(dlm, res);
+        /* since this lockres is new it doesnt not require the spinlock */
+        dlm_lockres_grab_inflight_ref_new(dlm, res);
+
+        /* if this node does not become the master make sure to drop
+         * this inflight reference below */
+        drop_inflight_if_nonlocal = 1;
+
         /* get an extra ref on the mle in case this is a BLOCK
          * if so, the creator of the BLOCK may try to put the last
          * ref at this time in the assert master handler, so we
@@ -910,7 +990,7 @@ redo_request:
         ret = -EINVAL;
         dlm_node_iter_init(mle->vote_map, &iter);
         while ((nodenum = dlm_node_iter_next(&iter)) >= 0) {
-                ret = dlm_do_master_request(mle, nodenum);
+                ret = dlm_do_master_request(res, mle, nodenum);
                 if (ret < 0)
                         mlog_errno(ret);
                 if (mle->master != O2NM_MAX_NODES) {
@@ -960,6 +1040,8 @@ wait:
 
 wake_waiters:
         spin_lock(&res->spinlock);
+        if (res->owner != dlm->node_num && drop_inflight_if_nonlocal)
+                dlm_lockres_drop_inflight_ref(dlm, res);
         res->state &= ~DLM_LOCK_RES_IN_PROGRESS;
         spin_unlock(&res->spinlock);
         wake_up(&res->wq);
@@ -998,7 +1080,7 @@ recheck:
                 /* 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(mle, res->owner);
+                        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);
@@ -1062,6 +1144,8 @@ recheck:
                                  * 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;
                         }
@@ -1087,7 +1171,8 @@ recheck:
                                          (atomic_read(&mle->woken) == 1),
                                          timeo);
                 if (res->owner == O2NM_MAX_NODES) {
-                        mlog(0, "waiting again\n");
+                        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);
@@ -1100,8 +1185,7 @@ recheck:
                 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->lockname.name,
-                                           res->lockname.len, mle->vote_map, 0);
+                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
@@ -1117,6 +1201,8 @@ recheck:
 
         /* 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);
 
@@ -1283,7 +1369,8 @@ static int dlm_restart_lock_mastery(struct dlm_ctxt *dlm,
  *
  */
 
-static int dlm_do_master_request(struct dlm_master_list_entry *mle, int to)
+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;
@@ -1339,6 +1426,9 @@ again:
                 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:
@@ -1428,8 +1518,10 @@ way_up_top:
                 }
 
                 if (res->owner == dlm->node_num) {
+                        mlog(0, "%s:%.*s: setting bit %u in refmap\n",
+                             dlm->name, namelen, name, request->node_idx);
+                        dlm_lockres_set_refmap_bit(request->node_idx, res);
                         spin_unlock(&res->spinlock);
-                        // mlog(0, "this node is the master\n");
                         response = DLM_MASTER_RESP_YES;
                         if (mle)
                                 kmem_cache_free(dlm_mle_cache, mle);
@@ -1477,7 +1569,6 @@ way_up_top:
                         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) {
-                                response = DLM_MASTER_RESP_YES;
                                 mlog(ML_ERROR, "no owner on lockres, but this "
                                      "node is trying to migrate it to %u?!\n",
                                      tmpmle->new_master);
@@ -1494,6 +1585,10 @@ way_up_top:
                                  * go back and clean the mles on any
                                  * other nodes */
                                 dispatch_assert = 1;
+                                dlm_lockres_set_refmap_bit(request->node_idx, res);
+                                mlog(0, "%s:%.*s: setting bit %u in refmap\n",
+                                     dlm->name, namelen, name,
+                                     request->node_idx);
                         } else
                                 response = DLM_MASTER_RESP_NO;
                 } else {
@@ -1607,15 +1702,17 @@ send_response:
  * 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, const char *lockname,
-                                unsigned int namelen, void *nodemap,
-                                u32 flags)
+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);
 again:
@@ -1647,6 +1744,7 @@ again:
                         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, "
@@ -1661,12 +1759,29 @@ again:
                         spin_unlock(&dlm->master_lock);
                         spin_unlock(&dlm->spinlock);
                         BUG();
-                } else if (r == EAGAIN) {
+                }
+
+                if (r & DLM_ASSERT_RESPONSE_REASSERT &&
+                    !(r & DLM_ASSERT_RESPONSE_MASTERY_REF)) {
+                                mlog(ML_ERROR, "%.*s: very strange, "
+                                     "master MLE but no lockres on %u\n",
+                                     namelen, lockname, to);
+                }
+
+                if (r & DLM_ASSERT_RESPONSE_REASSERT) {
                         mlog(0, "%.*s: node %u create mles on other "
                              "nodes and requests a re-assert\n", 
                              namelen, lockname, to);
                         reassert = 1;
                 }
+                if (r & DLM_ASSERT_RESPONSE_MASTERY_REF) {
+                        mlog(0, "%.*s: node %u has a reference to this "
+                             "lockres, set the bit in the refmap\n",
+                             namelen, lockname, to);
+                        spin_lock(&res->spinlock);
+                        dlm_lockres_set_refmap_bit(to, res);
+                        spin_unlock(&res->spinlock);
+                }
         }
 
         if (reassert)
@@ -1693,7 +1808,7 @@ int dlm_assert_master_handler(struct o2net_msg *msg, u32 len, void *data)
         char *name;
         unsigned int namelen, hash;
         u32 flags;
-        int master_request = 0;
+        int master_request = 0, have_lockres_ref = 0;
         int ret = 0;
 
         if (!dlm_grab(dlm))
@@ -1864,6 +1979,7 @@ ok:
                                 dlm_change_lockres_owner(dlm, res, mle->master);
                         }
                         spin_unlock(&res->spinlock);
+                        have_lockres_ref = 1;
                 }
 
                 /* master is known, detach if not already detached.
@@ -1918,7 +2034,19 @@ done:
         dlm_put(dlm);
         if (master_request) {
                 mlog(0, "need to tell master to reassert\n");
-                ret = EAGAIN;  // positive. negative would shoot down the node.
+                /* 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;
 
@@ -2023,9 +2151,7 @@ static void dlm_assert_master_worker(struct dlm_work_item *item, void *data)
          * 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->lockname.name,
-                                   res->lockname.len,
-                                   nodemap, flags);
+        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))
@@ -2097,6 +2223,104 @@ static int dlm_pre_master_reco_lockres(struct dlm_ctxt *dlm,
         return ret;
 }
 
+/*
+ * DLM_DEREF_LOCKRES_MSG
+ */
+
+int dlm_drop_lockres_ref(struct dlm_ctxt *dlm, struct dlm_lock_resource *res)
+{
+        struct dlm_deref_lockres deref;
+        int ret = 0, r;
+        const char *lockname;
+        unsigned int namelen;
+
+        lockname = res->lockname.name;
+        namelen = res->lockname.len;
+        BUG_ON(namelen > O2NM_MAX_NAME_LEN);
+
+        mlog(0, "%s:%.*s: sending deref to %d\n",
+             dlm->name, namelen, lockname, res->owner);
+        memset(&deref, 0, sizeof(deref));
+        deref.node_idx = dlm->node_num;
+        deref.namelen = namelen;
+        memcpy(deref.name, lockname, namelen);
+
+        ret = o2net_send_message(DLM_DEREF_LOCKRES_MSG, dlm->key,
+                                 &deref, sizeof(deref), res->owner, &r);
+        if (ret < 0)
+                mlog_errno(ret);
+        else if (r < 0) {
+                /* BAD.  other node says I did not have a ref. */
+                mlog(ML_ERROR,"while dropping ref on %s:%.*s "
+                    "(master=%u) got %d.\n", dlm->name, namelen,
+                    lockname, res->owner, r);
+                dlm_print_one_lock_resource(res);
+                BUG();
+        }
+        return ret;
+}
+
+int dlm_deref_lockres_handler(struct o2net_msg *msg, u32 len, void *data)
+{
+        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;
+
+        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);
+        BUG_ON(res->state & DLM_LOCK_RES_DROPPING_REF);
+        if (test_bit(node, res->refmap)) {
+                ret = 0;
+                dlm_lockres_clear_refmap_bit(node, res);
+        } else {
+                mlog(ML_ERROR, "%s:%.*s: node %u trying to drop ref "
+                     "but it is already dropped!\n", dlm->name, namelen,
+                     name, node);
+                __dlm_print_one_lock_resource(res);
+        }
+        spin_unlock(&res->spinlock);
+
+        if (!ret)
+                dlm_lockres_calc_usage(dlm, res);
+done:
+        if (res)
+                dlm_lockres_put(res);
+        dlm_put(dlm);
+        return ret;
+}
+
 
 /*
  * DLM_MIGRATE_LOCKRES
@@ -2376,6 +2600,53 @@ leave:
         return ret;
 }
 
+#define DLM_MIGRATION_RETRY_MS  100
+
+/* Should be called only after beginning the domain leave process.
+ * There should not be any remaining locks on nonlocal lock resources,
+ * and there should be no local locks left on locally mastered resources.
+ *
+ * Called with the dlm spinlock held, may drop it to do migration, but
+ * will re-acquire before exit.
+ *
+ * Returns: 1 if dlm->spinlock was dropped/retaken, 0 if never dropped */
+int dlm_empty_lockres(struct dlm_ctxt *dlm, struct dlm_lock_resource *res)
+{
+        int ret;
+        int lock_dropped = 0;
+
+        if (res->owner != dlm->node_num) {
+                if (!__dlm_lockres_unused(res)) {
+                        mlog(ML_ERROR, "%s:%.*s: this node is not master, "
+                             "trying to free this but locks remain\n",
+                             dlm->name, res->lockname.len, res->lockname.name);
+                }
+                goto leave;
+        }
+
+        /* Wheee! Migrate lockres here! Will sleep so drop spinlock. */
+        spin_unlock(&dlm->spinlock);
+        lock_dropped = 1;
+        while (1) {
+                ret = dlm_migrate_lockres(dlm, res, O2NM_MAX_NODES);
+                if (ret >= 0)
+                        break;
+                if (ret == -ENOTEMPTY) {
+                        mlog(ML_ERROR, "lockres %.*s still has local locks!\n",
+                                res->lockname.len, res->lockname.name);
+                        BUG();
+                }
+
+                mlog(0, "lockres %.*s: migrate failed, "
+                     "retrying\n", res->lockname.len,
+                     res->lockname.name);
+                msleep(DLM_MIGRATION_RETRY_MS);
+        }
+        spin_lock(&dlm->spinlock);
+leave:
+        return lock_dropped;
+}
+
 int dlm_lock_basts_flushed(struct dlm_ctxt *dlm, struct dlm_lock *lock)
 {
         int ret;
@@ -2490,7 +2761,7 @@ static void dlm_remove_nonlocal_locks(struct dlm_ctxt *dlm,
 {
         struct list_head *iter, *iter2;
         struct list_head *queue = &res->granted;
-        int i;
+        int i, bit;
         struct dlm_lock *lock;
 
         assert_spin_locked(&res->spinlock);
@@ -2508,12 +2779,28 @@ static void dlm_remove_nonlocal_locks(struct dlm_ctxt *dlm,
                                 BUG_ON(!list_empty(&lock->bast_list));
                                 BUG_ON(lock->ast_pending);
                                 BUG_ON(lock->bast_pending);
+                                dlm_lockres_clear_refmap_bit(lock->ml.node, res);
                                 list_del_init(&lock->list);
                                 dlm_lock_put(lock);
                         }
                 }
                 queue++;
         }
+        bit = 0;
+        while (1) {
+                bit = find_next_bit(res->refmap, O2NM_MAX_NODES, bit);
+                if (bit >= O2NM_MAX_NODES)
+                        break;
+                /* do not clear the local node reference, if there is a
+                 * process holding this, let it drop the ref itself */
+                if (bit != dlm->node_num) {
+                        mlog(0, "%s:%.*s: node %u had a ref to this "
+                             "migrating lockres, clearing\n", dlm->name,
+                             res->lockname.len, res->lockname.name, bit);
+                        dlm_lockres_clear_refmap_bit(bit, res);
+                }
+                bit++;
+        }
 }
 
 /* for now this is not too intelligent.  we will
@@ -2601,6 +2888,16 @@ static int dlm_do_migrate_request(struct dlm_ctxt *dlm,
                         mlog(0, "migrate request (node %u) returned %d!\n",
                              nodenum, status);
                         ret = status;
+                } else if (status == DLM_MIGRATE_RESPONSE_MASTERY_REF) {
+                        /* during the migration request we short-circuited
+                         * the mastery of the lockres.  make sure we have
+                         * a mastery ref for nodenum */
+                        mlog(0, "%s:%.*s: need ref for node %u\n",
+                             dlm->name, res->lockname.len, res->lockname.name,
+                             nodenum);
+                        spin_lock(&res->spinlock);
+                        dlm_lockres_set_refmap_bit(nodenum, res);
+                        spin_unlock(&res->spinlock);
                 }
         }
 
@@ -2745,7 +3042,13 @@ static int dlm_add_migration_mle(struct dlm_ctxt *dlm,
                         /* remove it from the list so that only one
                          * mle will be found */
                         list_del_init(&tmp->list);
-                        __dlm_mle_detach_hb_events(dlm, mle);
+                        /* this was obviously WRONG.  mle is uninited here.  should be tmp. */
+                        __dlm_mle_detach_hb_events(dlm, tmp);
+                        ret = DLM_MIGRATE_RESPONSE_MASTERY_REF;
+                        mlog(0, "%s:%.*s: master=%u, newmaster=%u, "
+                            "telling master to get ref for cleared out mle "
+                            "during migration\n", dlm->name, namelen, name,
+                            master, new_master);
                 }
                 spin_unlock(&tmp->spinlock);
         }
@@ -2753,6 +3056,8 @@ static int dlm_add_migration_mle(struct dlm_ctxt *dlm,
         /* 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);
@@ -2902,6 +3207,13 @@ int dlm_finish_migration(struct dlm_ctxt *dlm, struct dlm_lock_resource *res,
         clear_bit(dlm->node_num, iter.node_map);
         spin_unlock(&dlm->spinlock);
 
+        /* ownership of the lockres is changing.  account for the
+         * mastery reference here since old_master will briefly have
+         * a reference after the migration completes */
+        spin_lock(&res->spinlock);
+        dlm_lockres_set_refmap_bit(old_master, res);
+        spin_unlock(&res->spinlock);
+
         mlog(0, "now time to do a migrate request to other nodes\n");
         ret = dlm_do_migrate_request(dlm, res, old_master,
                                      dlm->node_num, &iter);
@@ -2914,8 +3226,7 @@ int dlm_finish_migration(struct dlm_ctxt *dlm, struct dlm_lock_resource *res,
              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->lockname.name,
-                                   res->lockname.len, iter.node_map,
+        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. */
@@ -2927,8 +3238,7 @@ int dlm_finish_migration(struct dlm_ctxt *dlm, struct dlm_lock_resource *res,
         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->lockname.name,
-                                   res->lockname.len, iter.node_map,
+        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 "
diff --git a/fs/ocfs2/dlm/dlmrecovery.c b/fs/ocfs2/dlm/dlmrecovery.c
index 367a11e9e2ed..d011a2a22742 100644
--- a/fs/ocfs2/dlm/dlmrecovery.c
+++ b/fs/ocfs2/dlm/dlmrecovery.c
@@ -1129,6 +1129,11 @@ static int dlm_send_mig_lockres_msg(struct dlm_ctxt *dlm,
         if (total_locks == mres_total_locks)
                 mres->flags |= DLM_MRES_ALL_DONE;
 
+        mlog(0, "%s:%.*s: sending mig lockres (%s) to %u\n",
+             dlm->name, res->lockname.len, res->lockname.name,
+             orig_flags & DLM_MRES_MIGRATION ? "migrate" : "recovery",
+             send_to);
+
         /* send it */
         ret = o2net_send_message(DLM_MIG_LOCKRES_MSG, dlm->key, mres,
                                  sz, send_to, &status);
@@ -1213,6 +1218,34 @@ static int dlm_add_lock_to_array(struct dlm_lock *lock,
         return 0;
 }
 
+static void dlm_add_dummy_lock(struct dlm_ctxt *dlm,
+                               struct dlm_migratable_lockres *mres)
+{
+        struct dlm_lock dummy;
+        memset(&dummy, 0, sizeof(dummy));
+        dummy.ml.cookie = 0;
+        dummy.ml.type = LKM_IVMODE;
+        dummy.ml.convert_type = LKM_IVMODE;
+        dummy.ml.highest_blocked = LKM_IVMODE;
+        dummy.lksb = NULL;
+        dummy.ml.node = dlm->node_num;
+        dlm_add_lock_to_array(&dummy, mres, DLM_BLOCKED_LIST);
+}
+
+static inline int dlm_is_dummy_lock(struct dlm_ctxt *dlm,
+                                    struct dlm_migratable_lock *ml,
+                                    u8 *nodenum)
+{
+        if (unlikely(ml->cookie == 0 &&
+            ml->type == LKM_IVMODE &&
+            ml->convert_type == LKM_IVMODE &&
+            ml->highest_blocked == LKM_IVMODE &&
+            ml->list == DLM_BLOCKED_LIST)) {
+                *nodenum = ml->node;
+                return 1;
+        }
+        return 0;
+}
 
 int dlm_send_one_lockres(struct dlm_ctxt *dlm, struct dlm_lock_resource *res,
                          struct dlm_migratable_lockres *mres,
@@ -1260,6 +1293,14 @@ int dlm_send_one_lockres(struct dlm_ctxt *dlm, struct dlm_lock_resource *res,
                                 goto error;
                 }
         }
+        if (total_locks == 0) {
+                /* send a dummy lock to indicate a mastery reference only */
+                mlog(0, "%s:%.*s: sending dummy lock to %u, %s\n",
+                     dlm->name, res->lockname.len, res->lockname.name,
+                     send_to, flags & DLM_MRES_RECOVERY ? "recovery" :
+                     "migration");
+                dlm_add_dummy_lock(dlm, mres);
+        }
         /* flush any remaining locks */
         ret = dlm_send_mig_lockres_msg(dlm, mres, send_to, res, total_locks);
         if (ret < 0)
@@ -1386,13 +1427,16 @@ int dlm_mig_lockres_handler(struct o2net_msg *msg, u32 len, void *data)
                 /* add an extra ref for just-allocated lockres 
                  * otherwise the lockres will be purged immediately */
                 dlm_lockres_get(res);
-
         }
 
         /* at this point we have allocated everything we need,
          * and we have a hashed lockres with an extra ref and
          * the proper res->state flags. */
         ret = 0;
+        spin_lock(&res->spinlock);
+        /* drop this either when master requery finds a different master
+         * or when a lock is added by the recovery worker */
+        dlm_lockres_grab_inflight_ref(dlm, res);
         if (mres->master == DLM_LOCK_RES_OWNER_UNKNOWN) {
                 /* migration cannot have an unknown master */
                 BUG_ON(!(mres->flags & DLM_MRES_RECOVERY));
@@ -1400,10 +1444,11 @@ int dlm_mig_lockres_handler(struct o2net_msg *msg, u32 len, void *data)
                           "unknown owner.. will need to requery: "
                           "%.*s\n", mres->lockname_len, mres->lockname);
         } else {
-                spin_lock(&res->spinlock);
+                /* take a reference now to pin the lockres, drop it
+                 * when locks are added in the worker */
                 dlm_change_lockres_owner(dlm, res, dlm->node_num);
-                spin_unlock(&res->spinlock);
         }
+        spin_unlock(&res->spinlock);
 
         /* queue up work for dlm_mig_lockres_worker */
         dlm_grab(dlm);  /* get an extra ref for the work item */
@@ -1459,6 +1504,9 @@ again:
                                    "this node will take it.\n",
                                    res->lockname.len, res->lockname.name);
                 } else {
+                        spin_lock(&res->spinlock);
+                        dlm_lockres_drop_inflight_ref(dlm, res);
+                        spin_unlock(&res->spinlock);
                         mlog(0, "master needs to respond to sender "
                                   "that node %u still owns %.*s\n",
                                   real_master, res->lockname.len,
@@ -1666,10 +1714,25 @@ static int dlm_process_recovery_data(struct dlm_ctxt *dlm,
         int i, bad;
         struct list_head *iter;
         struct dlm_lock *lock = NULL;
+        u8 from = O2NM_MAX_NODES;
+        unsigned int added = 0;
 
         mlog(0, "running %d locks for this lockres\n", mres->num_locks);
         for (i=0; i<mres->num_locks; i++) {
                 ml = &(mres->ml[i]);
+
+                if (dlm_is_dummy_lock(dlm, ml, &from)) {
+                        /* placeholder, just need to set the refmap bit */
+                        BUG_ON(mres->num_locks != 1);
+                        mlog(0, "%s:%.*s: dummy lock for %u\n",
+                             dlm->name, mres->lockname_len, mres->lockname,
+                             from);
+                        spin_lock(&res->spinlock);
+                        dlm_lockres_set_refmap_bit(from, res);
+                        spin_unlock(&res->spinlock);
+                        added++;
+                        break;
+                }
                 BUG_ON(ml->highest_blocked != LKM_IVMODE);
                 newlock = NULL;
                 lksb = NULL;
@@ -1711,6 +1774,7 @@ static int dlm_process_recovery_data(struct dlm_ctxt *dlm,
                         /* do not alter lock refcount.  switching lists. */
                         list_move_tail(&lock->list, queue);
                         spin_unlock(&res->spinlock);
+                        added++;
 
                         mlog(0, "just reordered a local lock!\n");
                         continue;
@@ -1817,12 +1881,24 @@ skip_lvb:
                 if (!bad) {
                         dlm_lock_get(newlock);
                         list_add_tail(&newlock->list, queue);
+                        mlog(0, "%s:%.*s: added lock for node %u, "
+                             "setting refmap bit\n", dlm->name,
+                             res->lockname.len, res->lockname.name, ml->node);
+                        dlm_lockres_set_refmap_bit(ml->node, res);
+                        added++;
                 }
                 spin_unlock(&res->spinlock);
         }
         mlog(0, "done running all the locks\n");
 
 leave:
+        /* balance the ref taken when the work was queued */
+        if (added > 0) {
+                spin_lock(&res->spinlock);
+                dlm_lockres_drop_inflight_ref(dlm, res);
+                spin_unlock(&res->spinlock);
+        }
+
         if (ret < 0) {
                 mlog_errno(ret);
                 if (newlock)
@@ -1935,9 +2011,11 @@ static void dlm_finish_local_lockres_recovery(struct dlm_ctxt *dlm,
                 if (res->owner == dead_node) {
                         list_del_init(&res->recovering);
                         spin_lock(&res->spinlock);
+                        /* new_master has our reference from
+                         * the lock state sent during recovery */
                         dlm_change_lockres_owner(dlm, res, new_master);
                         res->state &= ~DLM_LOCK_RES_RECOVERING;
-                        if (!__dlm_lockres_unused(res))
+                        if (__dlm_lockres_has_locks(res))
                                 __dlm_dirty_lockres(dlm, res);
                         spin_unlock(&res->spinlock);
                         wake_up(&res->wq);
@@ -1977,9 +2055,11 @@ static void dlm_finish_local_lockres_recovery(struct dlm_ctxt *dlm,
                                         dlm_lockres_put(res);
                                 }
                                 spin_lock(&res->spinlock);
+                                /* new_master has our reference from
+                                 * the lock state sent during recovery */
                                 dlm_change_lockres_owner(dlm, res, new_master);
                                 res->state &= ~DLM_LOCK_RES_RECOVERING;
-                                if (!__dlm_lockres_unused(res))
+                                if (__dlm_lockres_has_locks(res))
                                         __dlm_dirty_lockres(dlm, res);
                                 spin_unlock(&res->spinlock);
                                 wake_up(&res->wq);
@@ -2048,6 +2128,7 @@ static void dlm_free_dead_locks(struct dlm_ctxt *dlm,
 {
         struct list_head *iter, *tmpiter;
         struct dlm_lock *lock;
+        unsigned int freed = 0;
 
         /* this node is the lockres master:
          * 1) remove any stale locks for the dead node
@@ -2062,6 +2143,7 @@ static void dlm_free_dead_locks(struct dlm_ctxt *dlm,
                 if (lock->ml.node == dead_node) {
                         list_del_init(&lock->list);
                         dlm_lock_put(lock);
+                        freed++;
                 }
         }
         list_for_each_safe(iter, tmpiter, &res->converting) {
@@ -2069,6 +2151,7 @@ static void dlm_free_dead_locks(struct dlm_ctxt *dlm,
                 if (lock->ml.node == dead_node) {
                         list_del_init(&lock->list);
                         dlm_lock_put(lock);
+                        freed++;
                 }
         }
         list_for_each_safe(iter, tmpiter, &res->blocked) {
@@ -2076,9 +2159,23 @@ static void dlm_free_dead_locks(struct dlm_ctxt *dlm,
                 if (lock->ml.node == dead_node) {
                         list_del_init(&lock->list);
                         dlm_lock_put(lock);
+                        freed++;
                 }
         }
 
+        if (freed) {
+                mlog(0, "%s:%.*s: freed %u locks for dead node %u, "
+                     "dropping ref from lockres\n", dlm->name,
+                     res->lockname.len, res->lockname.name, freed, dead_node);
+                BUG_ON(!test_bit(dead_node, res->refmap));
+                dlm_lockres_clear_refmap_bit(dead_node, res);
+        } else if (test_bit(dead_node, res->refmap)) {
+                mlog(0, "%s:%.*s: dead node %u had a ref, but had "
+                     "no locks and had not purged before dying\n", dlm->name,
+                     res->lockname.len, res->lockname.name, dead_node);
+                dlm_lockres_clear_refmap_bit(dead_node, res);
+        }
+
         /* do not kick thread yet */
         __dlm_dirty_lockres(dlm, res);
 }
@@ -2141,9 +2238,21 @@ static void dlm_do_local_recovery_cleanup(struct dlm_ctxt *dlm, u8 dead_node)
                         spin_lock(&res->spinlock);
                         /* zero the lvb if necessary */
                         dlm_revalidate_lvb(dlm, res, dead_node);
-                        if (res->owner == dead_node)
+                        if (res->owner == dead_node) {
+                                if (res->state & DLM_LOCK_RES_DROPPING_REF)
+                                        mlog(0, "%s:%.*s: owned by "
+                                             "dead node %u, this node was "
+                                             "dropping its ref when it died. "
+                                             "continue, dropping the flag.\n",
+                                             dlm->name, res->lockname.len,
+                                             res->lockname.name, dead_node);
+
+                                /* the wake_up for this will happen when the
+                                 * RECOVERING flag is dropped later */
+                                res->state &= ~DLM_LOCK_RES_DROPPING_REF;
+
                                 dlm_move_lockres_to_recovery_list(dlm, res);
-                        else if (res->owner == dlm->node_num) {
+                        } else if (res->owner == dlm->node_num) {
                                 dlm_free_dead_locks(dlm, res, dead_node);
                                 __dlm_lockres_calc_usage(dlm, res);
                         }
diff --git a/fs/ocfs2/dlm/dlmthread.c b/fs/ocfs2/dlm/dlmthread.c
index 0c822f3ffb05..620eb824ce1d 100644
--- a/fs/ocfs2/dlm/dlmthread.c
+++ b/fs/ocfs2/dlm/dlmthread.c
@@ -54,9 +54,6 @@
 #include "cluster/masklog.h"
 
 static int dlm_thread(void *data);
-static void dlm_purge_lockres_now(struct dlm_ctxt *dlm,
-                                  struct dlm_lock_resource *lockres);
-
 static void dlm_flush_asts(struct dlm_ctxt *dlm);
 
 #define dlm_lock_is_remote(dlm, lock)     ((lock)->ml.node != (dlm)->node_num)
@@ -82,14 +79,33 @@ repeat:
         current->state = TASK_RUNNING;
 }
 
-
-int __dlm_lockres_unused(struct dlm_lock_resource *res)
+int __dlm_lockres_has_locks(struct dlm_lock_resource *res)
 {
         if (list_empty(&res->granted) &&
             list_empty(&res->converting) &&
-            list_empty(&res->blocked) &&
-            list_empty(&res->dirty))
-                return 1;
+            list_empty(&res->blocked))
+                return 0;
+        return 1;
+}
+
+/* "unused": the lockres has no locks, is not on the dirty list,
+ * has no inflight locks (in the gap between mastery and acquiring
+ * the first lock), and has no bits in its refmap.
+ * truly ready to be freed. */
+int __dlm_lockres_unused(struct dlm_lock_resource *res)
+{
+        if (!__dlm_lockres_has_locks(res) &&
+            list_empty(&res->dirty)) {
+                /* try not to scan the bitmap unless the first two
+                 * conditions are already true */
+                int bit = find_next_bit(res->refmap, O2NM_MAX_NODES, 0);
+                if (bit >= O2NM_MAX_NODES) {
+                        /* since the bit for dlm->node_num is not
+                         * set, inflight_locks better be zero */
+                        BUG_ON(res->inflight_locks != 0);
+                        return 1;
+                }
+        }
         return 0;
 }
 
@@ -106,46 +122,21 @@ void __dlm_lockres_calc_usage(struct dlm_ctxt *dlm,
         assert_spin_locked(&res->spinlock);
 
         if (__dlm_lockres_unused(res)){
-                /* For now, just keep any resource we master */
-                if (res->owner == dlm->node_num)
-                {
-                        if (!list_empty(&res->purge)) {
-                                mlog(0, "we master %s:%.*s, but it is on "
-                                     "the purge list.  Removing\n",
-                                     dlm->name, res->lockname.len,
-                                     res->lockname.name);
-                                list_del_init(&res->purge);
-                                dlm->purge_count--;
-                        }
-                        return;
-                }
-
                 if (list_empty(&res->purge)) {
-                        mlog(0, "putting lockres %.*s from purge list\n",
-                             res->lockname.len, res->lockname.name);
+                        mlog(0, "putting lockres %.*s:%p onto purge list\n",
+                             res->lockname.len, res->lockname.name, res);
 
                         res->last_used = jiffies;
+                        dlm_lockres_get(res);
                         list_add_tail(&res->purge, &dlm->purge_list);
                         dlm->purge_count++;
-
-                        /* if this node is not the owner, there is
-                         * no way to keep track of who the owner could be.
-                         * unhash it to avoid serious problems. */
-                        if (res->owner != dlm->node_num) {
-                                mlog(0, "%s:%.*s: doing immediate "
-                                     "purge of lockres owned by %u\n",
-                                     dlm->name, res->lockname.len,
-                                     res->lockname.name, res->owner);
-
-                                dlm_purge_lockres_now(dlm, res);
-                        }
                 }
         } else if (!list_empty(&res->purge)) {
-                mlog(0, "removing lockres %.*s from purge list, "
-                     "owner=%u\n", res->lockname.len, res->lockname.name,
-                     res->owner);
+                mlog(0, "removing lockres %.*s:%p from purge list, owner=%u\n",
+                     res->lockname.len, res->lockname.name, res, res->owner);
 
                 list_del_init(&res->purge);
+                dlm_lockres_put(res);
                 dlm->purge_count--;
         }
 }
@@ -163,68 +154,60 @@ void dlm_lockres_calc_usage(struct dlm_ctxt *dlm,
         spin_unlock(&dlm->spinlock);
 }
 
-/* TODO: Eventual API: Called with the dlm spinlock held, may drop it
- * to do migration, but will re-acquire before exit. */
-void dlm_purge_lockres(struct dlm_ctxt *dlm, struct dlm_lock_resource *lockres)
+int dlm_purge_lockres(struct dlm_ctxt *dlm, struct dlm_lock_resource *res)
 {
         int master;
-        int ret;
-
-        spin_lock(&lockres->spinlock);
-        master = lockres->owner == dlm->node_num;
-        spin_unlock(&lockres->spinlock);
-
-        mlog(0, "purging lockres %.*s, master = %d\n", lockres->lockname.len,
-             lockres->lockname.name, master);
+        int ret = 0;
 
-        /* Non master is the easy case -- no migration required, just
-         * quit. */
+        spin_lock(&res->spinlock);
+        if (!__dlm_lockres_unused(res)) {
+                spin_unlock(&res->spinlock);
+                mlog(0, "%s:%.*s: tried to purge but not unused\n",
+                     dlm->name, res->lockname.len, res->lockname.name);
+                return -ENOTEMPTY;
+        }
+        master = (res->owner == dlm->node_num);
         if (!master)
-                goto finish;
-
-        /* Wheee! Migrate lockres here! */
-        spin_unlock(&dlm->spinlock);
-again:
+                res->state |= DLM_LOCK_RES_DROPPING_REF;
+        spin_unlock(&res->spinlock);
 
-        ret = dlm_migrate_lockres(dlm, lockres, O2NM_MAX_NODES);
-        if (ret == -ENOTEMPTY) {
-                mlog(ML_ERROR, "lockres %.*s still has local locks!\n",
-                     lockres->lockname.len, lockres->lockname.name);
+        mlog(0, "purging lockres %.*s, master = %d\n", res->lockname.len,
+             res->lockname.name, master);
 
-                BUG();
-        } else if (ret < 0) {
-                mlog(ML_NOTICE, "lockres %.*s: migrate failed, retrying\n",
-                     lockres->lockname.len, lockres->lockname.name);
-                msleep(100);
-                goto again;
+        if (!master) {
+                /* drop spinlock to do messaging, retake below */
+                spin_unlock(&dlm->spinlock);
+                /* clear our bit from the master's refmap, ignore errors */
+                ret = dlm_drop_lockres_ref(dlm, res);
+                if (ret < 0) {
+                        mlog_errno(ret);
+                        if (!dlm_is_host_down(ret))
+                                BUG();
+                }
+                mlog(0, "%s:%.*s: dlm_deref_lockres returned %d\n",
+                     dlm->name, res->lockname.len, res->lockname.name, ret);
+                spin_lock(&dlm->spinlock);
         }
 
-        spin_lock(&dlm->spinlock);
-
-finish:
-        if (!list_empty(&lockres->purge)) {
-                list_del_init(&lockres->purge);
+        if (!list_empty(&res->purge)) {
+                mlog(0, "removing lockres %.*s:%p from purgelist, "
+                     "master = %d\n", res->lockname.len, res->lockname.name,
+                     res, master);
+                list_del_init(&res->purge);
+                dlm_lockres_put(res);
                 dlm->purge_count--;
         }
-        __dlm_unhash_lockres(lockres);
-}
-
-/* make an unused lockres go away immediately.
- * as soon as the dlm spinlock is dropped, this lockres
- * will not be found. kfree still happens on last put. */
-static void dlm_purge_lockres_now(struct dlm_ctxt *dlm,
-                                  struct dlm_lock_resource *lockres)
-{
-        assert_spin_locked(&dlm->spinlock);
-        assert_spin_locked(&lockres->spinlock);
-
-        BUG_ON(!__dlm_lockres_unused(lockres));
+        __dlm_unhash_lockres(res);
 
-        if (!list_empty(&lockres->purge)) {
-                list_del_init(&lockres->purge);
-                dlm->purge_count--;
+        /* lockres is not in the hash now.  drop the flag and wake up
+         * any processes waiting in dlm_get_lock_resource. */
+        if (!master) {
+                spin_lock(&res->spinlock);
+                res->state &= ~DLM_LOCK_RES_DROPPING_REF;
+                spin_unlock(&res->spinlock);
+                wake_up(&res->wq);
         }
-        __dlm_unhash_lockres(lockres);
+        return 0;
 }
 
 static void dlm_run_purge_list(struct dlm_ctxt *dlm,
@@ -268,13 +251,17 @@ static void dlm_run_purge_list(struct dlm_ctxt *dlm,
                         break;
                 }
 
+                mlog(0, "removing lockres %.*s:%p from purgelist\n",
+                     lockres->lockname.len, lockres->lockname.name, lockres);
                 list_del_init(&lockres->purge);
+                dlm_lockres_put(lockres);
                 dlm->purge_count--;
 
                 /* This may drop and reacquire the dlm spinlock if it
                  * has to do migration. */
                 mlog(0, "calling dlm_purge_lockres!\n");
-                dlm_purge_lockres(dlm, lockres);
+                if (dlm_purge_lockres(dlm, lockres))
+                        BUG();
                 mlog(0, "DONE calling dlm_purge_lockres!\n");
 
                 /* Avoid adding any scheduling latencies */