diff --git a/fs/dlm/ast.c b/fs/dlm/ast.c
index 4314f0d..abc49f2 100644
--- a/fs/dlm/ast.c
+++ b/fs/dlm/ast.c
@@ -18,6 +18,7 @@
 
 #define WAKE_ASTS  0
 
+static uint64_t			ast_seq_count;
 static struct list_head		ast_queue;
 static spinlock_t		ast_queue_lock;
 static struct task_struct *	astd_task;
@@ -25,40 +26,186 @@
 static struct mutex		astd_running;
 
 
+static void dlm_dump_lkb_callbacks(struct dlm_lkb *lkb)
+{
+	int i;
+
+	log_print("last_bast %x %llu flags %x mode %d sb %d %x",
+		  lkb->lkb_id,
+		  (unsigned long long)lkb->lkb_last_bast.seq,
+		  lkb->lkb_last_bast.flags,
+		  lkb->lkb_last_bast.mode,
+		  lkb->lkb_last_bast.sb_status,
+		  lkb->lkb_last_bast.sb_flags);
+
+	log_print("last_cast %x %llu flags %x mode %d sb %d %x",
+		  lkb->lkb_id,
+		  (unsigned long long)lkb->lkb_last_cast.seq,
+		  lkb->lkb_last_cast.flags,
+		  lkb->lkb_last_cast.mode,
+		  lkb->lkb_last_cast.sb_status,
+		  lkb->lkb_last_cast.sb_flags);
+
+	for (i = 0; i < DLM_CALLBACKS_SIZE; i++) {
+		log_print("cb %x %llu flags %x mode %d sb %d %x",
+			  lkb->lkb_id,
+			  (unsigned long long)lkb->lkb_callbacks[i].seq,
+			  lkb->lkb_callbacks[i].flags,
+			  lkb->lkb_callbacks[i].mode,
+			  lkb->lkb_callbacks[i].sb_status,
+			  lkb->lkb_callbacks[i].sb_flags);
+	}
+}
+
 void dlm_del_ast(struct dlm_lkb *lkb)
 {
 	spin_lock(&ast_queue_lock);
-	if (lkb->lkb_ast_type & (AST_COMP | AST_BAST))
-		list_del(&lkb->lkb_astqueue);
+	if (!list_empty(&lkb->lkb_astqueue))
+		list_del_init(&lkb->lkb_astqueue);
 	spin_unlock(&ast_queue_lock);
 }
 
-void dlm_add_ast(struct dlm_lkb *lkb, int type, int mode)
+int dlm_add_lkb_callback(struct dlm_lkb *lkb, uint32_t flags, int mode,
+			 int status, uint32_t sbflags, uint64_t seq)
 {
+	struct dlm_ls *ls = lkb->lkb_resource->res_ls;
+	uint64_t prev_seq;
+	int prev_mode;
+	int i;
+
+	for (i = 0; i < DLM_CALLBACKS_SIZE; i++) {
+		if (lkb->lkb_callbacks[i].seq)
+			continue;
+
+		/*
+		 * Suppress some redundant basts here, do more on removal.
+		 * Don't even add a bast if the callback just before it
+		 * is a bast for the same mode or a more restrictive mode.
+		 * (the addional > PR check is needed for PR/CW inversion)
+		 */
+
+		if ((i > 0) && (flags & DLM_CB_BAST) &&
+		    (lkb->lkb_callbacks[i-1].flags & DLM_CB_BAST)) {
+
+			prev_seq = lkb->lkb_callbacks[i-1].seq;
+			prev_mode = lkb->lkb_callbacks[i-1].mode;
+
+			if ((prev_mode == mode) ||
+			    (prev_mode > mode && prev_mode > DLM_LOCK_PR)) {
+
+				log_debug(ls, "skip %x add bast %llu mode %d "
+					  "for bast %llu mode %d",
+					  lkb->lkb_id,
+					  (unsigned long long)seq,
+					  mode,
+					  (unsigned long long)prev_seq,
+					  prev_mode);
+				return 0;
+			}
+		}
+
+		lkb->lkb_callbacks[i].seq = seq;
+		lkb->lkb_callbacks[i].flags = flags;
+		lkb->lkb_callbacks[i].mode = mode;
+		lkb->lkb_callbacks[i].sb_status = status;
+		lkb->lkb_callbacks[i].sb_flags = (sbflags & 0x000000FF);
+		break;
+	}
+
+	if (i == DLM_CALLBACKS_SIZE) {
+		log_error(ls, "no callbacks %x %llu flags %x mode %d sb %d %x",
+			  lkb->lkb_id, (unsigned long long)seq,
+			  flags, mode, status, sbflags);
+		dlm_dump_lkb_callbacks(lkb);
+		return -1;
+	}
+
+	return 0;
+}
+
+int dlm_rem_lkb_callback(struct dlm_ls *ls, struct dlm_lkb *lkb,
+			 struct dlm_callback *cb, int *resid)
+{
+	int i;
+
+	*resid = 0;
+
+	if (!lkb->lkb_callbacks[0].seq)
+		return -ENOENT;
+
+	/* oldest undelivered cb is callbacks[0] */
+
+	memcpy(cb, &lkb->lkb_callbacks[0], sizeof(struct dlm_callback));
+	memset(&lkb->lkb_callbacks[0], 0, sizeof(struct dlm_callback));
+
+	/* shift others down */
+
+	for (i = 1; i < DLM_CALLBACKS_SIZE; i++) {
+		if (!lkb->lkb_callbacks[i].seq)
+			break;
+		memcpy(&lkb->lkb_callbacks[i-1], &lkb->lkb_callbacks[i],
+		       sizeof(struct dlm_callback));
+		memset(&lkb->lkb_callbacks[i], 0, sizeof(struct dlm_callback));
+		(*resid)++;
+	}
+
+	/* if cb is a bast, it should be skipped if the blocking mode is
+	   compatible with the last granted mode */
+
+	if ((cb->flags & DLM_CB_BAST) && lkb->lkb_last_cast.seq) {
+		if (dlm_modes_compat(cb->mode, lkb->lkb_last_cast.mode)) {
+			cb->flags |= DLM_CB_SKIP;
+
+			log_debug(ls, "skip %x bast %llu mode %d "
+				  "for cast %llu mode %d",
+				  lkb->lkb_id,
+				  (unsigned long long)cb->seq,
+				  cb->mode,
+				  (unsigned long long)lkb->lkb_last_cast.seq,
+				  lkb->lkb_last_cast.mode);
+			return 0;
+		}
+	}
+
+	if (cb->flags & DLM_CB_CAST) {
+		memcpy(&lkb->lkb_last_cast, cb, sizeof(struct dlm_callback));
+		lkb->lkb_last_cast_time = ktime_get();
+	}
+
+	if (cb->flags & DLM_CB_BAST) {
+		memcpy(&lkb->lkb_last_bast, cb, sizeof(struct dlm_callback));
+		lkb->lkb_last_bast_time = ktime_get();
+	}
+
+	return 0;
+}
+
+void dlm_add_ast(struct dlm_lkb *lkb, uint32_t flags, int mode, int status,
+		 uint32_t sbflags)
+{
+	uint64_t seq;
+	int rv;
+
+	spin_lock(&ast_queue_lock);
+
+	seq = ++ast_seq_count;
+
 	if (lkb->lkb_flags & DLM_IFL_USER) {
-		dlm_user_add_ast(lkb, type, mode);
+		spin_unlock(&ast_queue_lock);
+		dlm_user_add_ast(lkb, flags, mode, status, sbflags, seq);
 		return;
 	}
 
-	spin_lock(&ast_queue_lock);
-	if (!(lkb->lkb_ast_type & (AST_COMP | AST_BAST))) {
-		kref_get(&lkb->lkb_ref);
-		list_add_tail(&lkb->lkb_astqueue, &ast_queue);
-		lkb->lkb_ast_first = type;
+	rv = dlm_add_lkb_callback(lkb, flags, mode, status, sbflags, seq);
+	if (rv < 0) {
+		spin_unlock(&ast_queue_lock);
+		return;
 	}
 
-	/* sanity check, this should not happen */
-
-	if ((type == AST_COMP) && (lkb->lkb_ast_type & AST_COMP))
-		log_print("repeat cast %d castmode %d lock %x %s",
-			  mode, lkb->lkb_castmode,
-			  lkb->lkb_id, lkb->lkb_resource->res_name);
-
-	lkb->lkb_ast_type |= type;
-	if (type == AST_BAST)
-		lkb->lkb_bastmode = mode;
-	else
-		lkb->lkb_castmode = mode;
+	if (list_empty(&lkb->lkb_astqueue)) {
+		kref_get(&lkb->lkb_ref);
+		list_add_tail(&lkb->lkb_astqueue, &ast_queue);
+	}
 	spin_unlock(&ast_queue_lock);
 
 	set_bit(WAKE_ASTS, &astd_wakeflags);
@@ -72,7 +219,8 @@
 	struct dlm_lkb *lkb;
 	void (*castfn) (void *astparam);
 	void (*bastfn) (void *astparam, int mode);
-	int type, first, bastmode, castmode, do_bast, do_cast, last_castmode;
+	struct dlm_callback callbacks[DLM_CALLBACKS_SIZE];
+	int i, rv, resid;
 
 repeat:
 	spin_lock(&ast_queue_lock);
@@ -83,54 +231,45 @@
 		if (dlm_locking_stopped(ls))
 			continue;
 
-		list_del(&lkb->lkb_astqueue);
-		type = lkb->lkb_ast_type;
-		lkb->lkb_ast_type = 0;
-		first = lkb->lkb_ast_first;
-		lkb->lkb_ast_first = 0;
-		bastmode = lkb->lkb_bastmode;
-		castmode = lkb->lkb_castmode;
+		/* we remove from astqueue list and remove everything in
+		   lkb_callbacks before releasing the spinlock so empty
+		   lkb_astqueue is always consistent with empty lkb_callbacks */
+
+		list_del_init(&lkb->lkb_astqueue);
+
 		castfn = lkb->lkb_astfn;
 		bastfn = lkb->lkb_bastfn;
+
+		memset(&callbacks, 0, sizeof(callbacks));
+
+		for (i = 0; i < DLM_CALLBACKS_SIZE; i++) {
+			rv = dlm_rem_lkb_callback(ls, lkb, &callbacks[i], &resid);
+			if (rv < 0)
+				break;
+		}
 		spin_unlock(&ast_queue_lock);
 
-		do_cast = (type & AST_COMP) && castfn;
-		do_bast = (type & AST_BAST) && bastfn;
-
-		/* Skip a bast if its blocking mode is compatible with the
-		   granted mode of the preceding cast. */
-
-		if (do_bast) {
-			if (first == AST_COMP)
-				last_castmode = castmode;
-			else
-				last_castmode = lkb->lkb_castmode_done;
-			if (dlm_modes_compat(bastmode, last_castmode))
-				do_bast = 0;
+		if (resid) {
+			/* shouldn't happen, for loop should have removed all */
+			log_error(ls, "callback resid %d lkb %x",
+				  resid, lkb->lkb_id);
 		}
 
-		if (first == AST_COMP) {
-			if (do_cast)
+		for (i = 0; i < DLM_CALLBACKS_SIZE; i++) {
+			if (!callbacks[i].seq)
+				break;
+			if (callbacks[i].flags & DLM_CB_SKIP) {
+				continue;
+			} else if (callbacks[i].flags & DLM_CB_BAST) {
+				bastfn(lkb->lkb_astparam, callbacks[i].mode);
+			} else if (callbacks[i].flags & DLM_CB_CAST) {
+				lkb->lkb_lksb->sb_status = callbacks[i].sb_status;
+				lkb->lkb_lksb->sb_flags = callbacks[i].sb_flags;
 				castfn(lkb->lkb_astparam);
-			if (do_bast)
-				bastfn(lkb->lkb_astparam, bastmode);
-		} else if (first == AST_BAST) {
-			if (do_bast)
-				bastfn(lkb->lkb_astparam, bastmode);
-			if (do_cast)
-				castfn(lkb->lkb_astparam);
-		} else {
-			log_error(ls, "bad ast_first %d ast_type %d",
-				  first, type);
+			}
 		}
 
-		if (do_cast)
-			lkb->lkb_castmode_done = castmode;
-		if (do_bast)
-			lkb->lkb_bastmode_done = bastmode;
-
-		/* this removes the reference added by dlm_add_ast
-		   and may result in the lkb being freed */
+		/* removes ref for ast_queue, may cause lkb to be freed */
 		dlm_put_lkb(lkb);
 
 		cond_resched();