diff --git a/drivers/md/bcache/bset.c b/drivers/md/bcache/bset.c
index bfee926e35f06b88bd435854e221814774ad278a..9e3a53d87de02bb631d36605ae1e959cbce0a113 100644
--- a/drivers/md/bcache/bset.c
+++ b/drivers/md/bcache/bset.c
@@ -855,19 +855,13 @@ struct bkey *__bch_bset_search(struct btree *b, struct bset_tree *t,
 
 /* Btree iterator */
 
-/*
- * Returns true if l > r - unless l == r, in which case returns true if l is
- * older than r.
- *
- * Necessary for btree_sort_fixup() - if there are multiple keys that compare
- * equal in different sets, we have to process them newest to oldest.
- */
+typedef bool (btree_iter_cmp_fn)(struct btree_iter_set,
+				 struct btree_iter_set);
+
 static inline bool btree_iter_cmp(struct btree_iter_set l,
 				  struct btree_iter_set r)
 {
-	int64_t c = bkey_cmp(&START_KEY(l.k), &START_KEY(r.k));
-
-	return c ? c > 0 : l.k < r.k;
+	return bkey_cmp(l.k, r.k) > 0;
 }
 
 static inline bool btree_iter_end(struct btree_iter *iter)
@@ -884,8 +878,10 @@ void bch_btree_iter_push(struct btree_iter *iter, struct bkey *k,
 				 btree_iter_cmp));
 }
 
-struct bkey *__bch_btree_iter_init(struct btree *b, struct btree_iter *iter,
-				   struct bkey *search, struct bset_tree *start)
+static struct bkey *__bch_btree_iter_init(struct btree *b,
+					  struct btree_iter *iter,
+					  struct bkey *search,
+					  struct bset_tree *start)
 {
 	struct bkey *ret = NULL;
 	iter->size = ARRAY_SIZE(iter->data);
@@ -903,7 +899,15 @@ struct bkey *__bch_btree_iter_init(struct btree *b, struct btree_iter *iter,
 	return ret;
 }
 
-struct bkey *bch_btree_iter_next(struct btree_iter *iter)
+struct bkey *bch_btree_iter_init(struct btree *b,
+				 struct btree_iter *iter,
+				 struct bkey *search)
+{
+	return __bch_btree_iter_init(b, iter, search, b->sets);
+}
+
+static inline struct bkey *__bch_btree_iter_next(struct btree_iter *iter,
+						 btree_iter_cmp_fn *cmp)
 {
 	struct btree_iter_set unused;
 	struct bkey *ret = NULL;
@@ -920,14 +924,20 @@ struct bkey *bch_btree_iter_next(struct btree_iter *iter)
 		}
 
 		if (iter->data->k == iter->data->end)
-			heap_pop(iter, unused, btree_iter_cmp);
+			heap_pop(iter, unused, cmp);
 		else
-			heap_sift(iter, 0, btree_iter_cmp);
+			heap_sift(iter, 0, cmp);
 	}
 
 	return ret;
 }
 
+struct bkey *bch_btree_iter_next(struct btree_iter *iter)
+{
+	return __bch_btree_iter_next(iter, btree_iter_cmp);
+
+}
+
 struct bkey *bch_btree_iter_next_filter(struct btree_iter *iter,
 					struct btree *b, ptr_filter_fn fn)
 {
@@ -951,13 +961,37 @@ static void sort_key_next(struct btree_iter *iter,
 		*i = iter->data[--iter->used];
 }
 
-static struct bkey *btree_sort_fixup(struct btree_iter *iter, struct bkey *tmp)
+/*
+ * Returns true if l > r - unless l == r, in which case returns true if l is
+ * older than r.
+ *
+ * Necessary for btree_sort_fixup() - if there are multiple keys that compare
+ * equal in different sets, we have to process them newest to oldest.
+ */
+static inline bool sort_extent_cmp(struct btree_iter_set l,
+				   struct btree_iter_set r)
+{
+	int64_t c = bkey_cmp(&START_KEY(l.k), &START_KEY(r.k));
+
+	return c ? c > 0 : l.k < r.k;
+}
+
+static inline bool sort_cmp(struct btree_iter_set l,
+			    struct btree_iter_set r)
+{
+	int64_t c = bkey_cmp(l.k, r.k);
+
+	return c ? c > 0 : l.k < r.k;
+}
+
+static struct bkey *btree_sort_fixup_extents(struct btree_iter *iter,
+					     struct bkey *tmp)
 {
 	while (iter->used > 1) {
 		struct btree_iter_set *top = iter->data, *i = top + 1;
 
 		if (iter->used > 2 &&
-		    btree_iter_cmp(i[0], i[1]))
+		    sort_extent_cmp(i[0], i[1]))
 			i++;
 
 		if (bkey_cmp(top->k, &START_KEY(i->k)) <= 0)
@@ -965,7 +999,7 @@ static struct bkey *btree_sort_fixup(struct btree_iter *iter, struct bkey *tmp)
 
 		if (!KEY_SIZE(i->k)) {
 			sort_key_next(iter, i);
-			heap_sift(iter, i - top, btree_iter_cmp);
+			heap_sift(iter, i - top, sort_extent_cmp);
 			continue;
 		}
 
@@ -975,7 +1009,7 @@ static struct bkey *btree_sort_fixup(struct btree_iter *iter, struct bkey *tmp)
 			else
 				bch_cut_front(top->k, i->k);
 
-			heap_sift(iter, i - top, btree_iter_cmp);
+			heap_sift(iter, i - top, sort_extent_cmp);
 		} else {
 			/* can't happen because of comparison func */
 			BUG_ON(!bkey_cmp(&START_KEY(top->k), &START_KEY(i->k)));
@@ -1001,20 +1035,28 @@ static void btree_mergesort(struct btree *b, struct bset *out,
 			    struct btree_iter *iter,
 			    bool fixup, bool remove_stale)
 {
+	int i;
 	struct bkey *k, *last = NULL;
 	BKEY_PADDED(k) tmp;
+	btree_iter_cmp_fn *cmp = b->level
+		? sort_cmp
+		: sort_extent_cmp;
 	bool (*bad)(struct btree *, const struct bkey *) = remove_stale
 		? bch_ptr_bad
 		: bch_ptr_invalid;
 
+	/* Heapify the iterator, using our comparison function */
+	for (i = iter->used / 2 - 1; i >= 0; --i)
+		heap_sift(iter, i, cmp);
+
 	while (!btree_iter_end(iter)) {
 		if (fixup && !b->level)
-			k = btree_sort_fixup(iter, &tmp.k);
+			k = btree_sort_fixup_extents(iter, &tmp.k);
 		else
 			k = NULL;
 
 		if (!k)
-			k = bch_btree_iter_next(iter);
+			k = __bch_btree_iter_next(iter, cmp);
 
 		if (bad(b, k))
 			continue;
diff --git a/drivers/md/bcache/bset.h b/drivers/md/bcache/bset.h
index 88b6edbf508b45aac3ef98e4a6e62039f468cdf5..91bcbdb04085a3969e7ca7b27d61a33c3fea428b 100644
--- a/drivers/md/bcache/bset.h
+++ b/drivers/md/bcache/bset.h
@@ -305,8 +305,8 @@ struct bkey *bch_btree_iter_next_filter(struct btree_iter *,
 					struct btree *, ptr_filter_fn);
 
 void bch_btree_iter_push(struct btree_iter *, struct bkey *, struct bkey *);
-struct bkey *__bch_btree_iter_init(struct btree *, struct btree_iter *,
-				   struct bkey *, struct bset_tree *);
+struct bkey *bch_btree_iter_init(struct btree *, struct btree_iter *,
+				 struct bkey *);
 
 /* 32 bits total: */
 #define BKEY_MID_BITS		3
diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c
index 8aaaf16637a09236ba95cfd617fadf40806293c7..e1e36e761724c9618042434e95e08bebfef815f9 100644
--- a/drivers/md/bcache/btree.c
+++ b/drivers/md/bcache/btree.c
@@ -1854,10 +1854,16 @@ static bool fix_overlapping_extents(struct btree *b, struct bkey *insert,
 
 	while (1) {
 		struct bkey *k = bch_btree_iter_next(iter);
-		if (!k ||
-		    bkey_cmp(&START_KEY(k), insert) >= 0)
+		if (!k)
 			break;
 
+		if (bkey_cmp(&START_KEY(k), insert) >= 0) {
+			if (KEY_SIZE(k))
+				break;
+			else
+				continue;
+		}
+
 		if (bkey_cmp(k, &START_KEY(insert)) <= 0)
 			continue;
 
diff --git a/drivers/md/bcache/btree.h b/drivers/md/bcache/btree.h
index 580b01137264758d2c7435c22d067c081340151f..2a5a8481f25e125cc2543553b897e11dfca7e3d2 100644
--- a/drivers/md/bcache/btree.h
+++ b/drivers/md/bcache/btree.h
@@ -225,13 +225,6 @@ static inline void set_gc_sectors(struct cache_set *c)
 	atomic_set(&c->sectors_to_gc, c->sb.bucket_size * c->nbuckets / 16);
 }
 
-static inline struct bkey *bch_btree_iter_init(struct btree *b,
-					       struct btree_iter *iter,
-					       struct bkey *search)
-{
-	return __bch_btree_iter_init(b, iter, search, b->sets);
-}
-
 static inline bool bch_ptr_invalid(struct btree *b, const struct bkey *k)
 {
 	if (b->level)