diff --git a/include/sys/bqueue.h b/include/sys/bqueue.h
index b9621966027a..bd66e172c66e 100644
--- a/include/sys/bqueue.h
+++ b/include/sys/bqueue.h
@@ -27,10 +27,14 @@ extern "C" {
 
 typedef struct bqueue {
 	list_t bq_list;
+	size_t bq_size;
+	list_t bq_deqing_list;
+	size_t bq_deqing_size;
+	list_t bq_enqing_list;
+	size_t bq_enqing_size;
 	kmutex_t bq_lock;
 	kcondvar_t bq_add_cv;
 	kcondvar_t bq_pop_cv;
-	size_t bq_size;
 	size_t bq_maxsize;
 	uint_t bq_fill_fraction;
 	size_t bq_node_offset;
@@ -47,7 +51,6 @@ void bqueue_destroy(bqueue_t *);
 void bqueue_enqueue(bqueue_t *, void *, size_t);
 void bqueue_enqueue_flush(bqueue_t *, void *, size_t);
 void *bqueue_dequeue(bqueue_t *);
-boolean_t bqueue_empty(bqueue_t *);
 
 #ifdef	__cplusplus
 }
diff --git a/module/zfs/bqueue.c b/module/zfs/bqueue.c
index ec5ce4388ec8..a1a3b31186d4 100644
--- a/module/zfs/bqueue.c
+++ b/module/zfs/bqueue.c
@@ -27,19 +27,26 @@ obj2node(bqueue_t *q, void *data)
 
 /*
  * Initialize a blocking queue  The maximum capacity of the queue is set to
- * size.  Types that are stored in a bqueue must contain a bqueue_node_t,
- * and node_offset must be its offset from the start of the struct.
- * fill_fraction is a performance tuning value; when the queue is full, any
- * threads attempting to enqueue records will block.  They will block until
- * they're signaled, which will occur when the queue is at least 1/fill_fraction
+ * size.  Types that are stored in a bqueue must contain a bqueue_node_t, and
+ * node_offset must be its offset from the start of the struct. fill_fraction
+ * is a performance tuning value; when the queue is full, any threads
+ * attempting to enqueue records will block.  They will block until they're
+ * signaled, which will occur when the queue is at least 1/fill_fraction
  * empty.  Similar behavior occurs on dequeue; if the queue is empty, threads
- * block.  They will be signalled when the queue has 1/fill_fraction full, or
- * when bqueue_flush is called.  As a result, you must call bqueue_flush when
- * you enqueue your final record on a thread, in case the dequeueing threads are
- * currently blocked and that enqueue does not cause them to be awoken.
- * Alternatively, this behavior can be disabled (causing signaling to happen
- * immediately) by setting fill_fraction to any value larger than size.
- * Return 0 on success, or -1 on failure.
+ * block.  They will be signalled when the queue has 1/fill_fraction full.
+ * As a result, you must call bqueue_enqueue_flush() when you enqueue your
+ * final record on a thread, in case the dequeuing threads are currently
+ * blocked and that enqueue does not cause them to be woken. Alternatively,
+ * this behavior can be disabled (causing signaling to happen immediately) by
+ * setting fill_fraction to any value larger than size. Return 0 on success,
+ * or -1 on failure.
+ *
+ * Note: The caller must ensure that for a given bqueue_t, there's only a
+ * single call to bqueue_enqueue() running at a time (e.g. by calling only
+ * from a single thread, or with locking around the call). Similarly, the
+ * caller must ensure that there's only a single call to bqueue_dequeue()
+ * running at a time. However, the one call to bqueue_enqueue() may be
+ * invoked concurrently with the one call to bqueue_dequeue().
  */
 int
 bqueue_init(bqueue_t *q, uint_t fill_fraction, size_t size, size_t node_offset)
@@ -49,11 +56,17 @@ bqueue_init(bqueue_t *q, uint_t fill_fraction, size_t size, size_t node_offset)
 	}
 	list_create(&q->bq_list, node_offset + sizeof (bqueue_node_t),
 	    node_offset + offsetof(bqueue_node_t, bqn_node));
+	list_create(&q->bq_deqing_list, node_offset + sizeof (bqueue_node_t),
+	    node_offset + offsetof(bqueue_node_t, bqn_node));
+	list_create(&q->bq_enqing_list, node_offset + sizeof (bqueue_node_t),
+	    node_offset + offsetof(bqueue_node_t, bqn_node));
 	cv_init(&q->bq_add_cv, NULL, CV_DEFAULT, NULL);
 	cv_init(&q->bq_pop_cv, NULL, CV_DEFAULT, NULL);
 	mutex_init(&q->bq_lock, NULL, MUTEX_DEFAULT, NULL);
 	q->bq_node_offset = node_offset;
 	q->bq_size = 0;
+	q->bq_deqing_size = 0;
+	q->bq_enqing_size = 0;
 	q->bq_maxsize = size;
 	q->bq_fill_fraction = fill_fraction;
 	return (0);
@@ -69,9 +82,13 @@ bqueue_destroy(bqueue_t *q)
 {
 	mutex_enter(&q->bq_lock);
 	ASSERT0(q->bq_size);
+	ASSERT0(q->bq_deqing_size);
+	ASSERT0(q->bq_enqing_size);
 	cv_destroy(&q->bq_add_cv);
 	cv_destroy(&q->bq_pop_cv);
 	list_destroy(&q->bq_list);
+	list_destroy(&q->bq_deqing_list);
+	list_destroy(&q->bq_enqing_list);
 	mutex_exit(&q->bq_lock);
 	mutex_destroy(&q->bq_lock);
 }
@@ -81,23 +98,24 @@ bqueue_enqueue_impl(bqueue_t *q, void *data, size_t item_size, boolean_t flush)
 {
 	ASSERT3U(item_size, >, 0);
 	ASSERT3U(item_size, <=, q->bq_maxsize);
-	mutex_enter(&q->bq_lock);
+
 	obj2node(q, data)->bqn_size = item_size;
-	while (q->bq_size && q->bq_size + item_size > q->bq_maxsize) {
-		/*
-		 * Wake up bqueue_dequeue() thread if already sleeping in order
-		 * to prevent the deadlock condition
-		 */
-		cv_signal(&q->bq_pop_cv);
-		cv_wait_sig(&q->bq_add_cv, &q->bq_lock);
-	}
-	q->bq_size += item_size;
-	list_insert_tail(&q->bq_list, data);
-	if (flush)
+	q->bq_enqing_size += item_size;
+	list_insert_tail(&q->bq_enqing_list, data);
+
+	if (flush ||
+	    q->bq_enqing_size >= q->bq_maxsize / q->bq_fill_fraction) {
+		/* Append the enquing list to the shared list. */
+		mutex_enter(&q->bq_lock);
+		while (q->bq_size > q->bq_maxsize) {
+			cv_wait_sig(&q->bq_add_cv, &q->bq_lock);
+		}
+		q->bq_size += q->bq_enqing_size;
+		list_move_tail(&q->bq_list, &q->bq_enqing_list);
+		q->bq_enqing_size = 0;
 		cv_broadcast(&q->bq_pop_cv);
-	else if (q->bq_size >= q->bq_maxsize / q->bq_fill_fraction)
-		cv_signal(&q->bq_pop_cv);
-	mutex_exit(&q->bq_lock);
+		mutex_exit(&q->bq_lock);
+	}
 }
 
 /*
@@ -115,8 +133,8 @@ bqueue_enqueue(bqueue_t *q, void *data, size_t item_size)
  * Enqueue an entry, and then flush the queue.  This forces the popping threads
  * to wake up, even if we're below the fill fraction.  We have this in a single
  * function, rather than having a separate call, because it prevents race
- * conditions between the enqueuing thread and the dequeueing thread, where the
- * enqueueing thread will wake up the dequeueing thread, that thread will
+ * conditions between the enqueuing thread and the dequeuing thread, where the
+ * enqueueing thread will wake up the dequeuing thread, that thread will
  * destroy the condvar before the enqueuing thread is done.
  */
 void
@@ -132,27 +150,26 @@ bqueue_enqueue_flush(bqueue_t *q, void *data, size_t item_size)
 void *
 bqueue_dequeue(bqueue_t *q)
 {
-	void *ret = NULL;
-	size_t item_size;
-	mutex_enter(&q->bq_lock);
-	while (q->bq_size == 0) {
-		cv_wait_sig(&q->bq_pop_cv, &q->bq_lock);
+	void *ret = list_remove_head(&q->bq_deqing_list);
+	if (ret == NULL) {
+		/*
+		 * Dequeuing list is empty.  Wait for there to be something on
+		 * the shared list, then move the entire shared list to the
+		 * dequeuing list.
+		 */
+		mutex_enter(&q->bq_lock);
+		while (q->bq_size == 0) {
+			cv_wait_sig(&q->bq_pop_cv, &q->bq_lock);
+		}
+		ASSERT0(q->bq_deqing_size);
+		ASSERT(list_is_empty(&q->bq_deqing_list));
+		list_move_tail(&q->bq_deqing_list, &q->bq_list);
+		q->bq_deqing_size = q->bq_size;
+		q->bq_size = 0;
+		cv_broadcast(&q->bq_add_cv);
+		mutex_exit(&q->bq_lock);
+		ret = list_remove_head(&q->bq_deqing_list);
 	}
-	ret = list_remove_head(&q->bq_list);
-	ASSERT3P(ret, !=, NULL);
-	item_size = obj2node(q, ret)->bqn_size;
-	q->bq_size -= item_size;
-	if (q->bq_size <= q->bq_maxsize - (q->bq_maxsize / q->bq_fill_fraction))
-		cv_signal(&q->bq_add_cv);
-	mutex_exit(&q->bq_lock);
+	q->bq_deqing_size -= obj2node(q, ret)->bqn_size;
 	return (ret);
 }
-
-/*
- * Returns true if the space used is 0.
- */
-boolean_t
-bqueue_empty(bqueue_t *q)
-{
-	return (q->bq_size == 0);
-}