diff --git a/fs/bcachefs/bset.c b/fs/bcachefs/bset.c
index cf83911b3f5d..27fa3e230e6e 100644
--- a/fs/bcachefs/bset.c
+++ b/fs/bcachefs/bset.c
@@ -18,6 +18,9 @@
 #include <linux/random.h>
 #include <linux/prefetch.h>
 
+static inline void __bch2_btree_node_iter_advance(struct btree_node_iter *,
+						  struct btree *);
+
 struct bset_tree *bch2_bkey_to_bset(struct btree *b, struct bkey_packed *k)
 {
 	unsigned offset = __btree_node_key_to_offset(b, k);
@@ -63,8 +66,8 @@ void bch2_dump_bset(struct btree *b, struct bset *i, unsigned set)
 		_n = bkey_next(_k);
 
 		bch2_bkey_to_text(buf, sizeof(buf), &k);
-		printk(KERN_ERR "block %u key %zi/%u: %s\n", set,
-		       _k->_data - i->_data, i->u64s, buf);
+		printk(KERN_ERR "block %u key %5u: %s\n", set,
+		       __btree_node_key_to_offset(b, _k), buf);
 
 		if (_n == vstruct_last(i))
 			continue;
@@ -120,20 +123,6 @@ void bch2_dump_btree_node_iter(struct btree *b,
 
 #ifdef CONFIG_BCACHEFS_DEBUG
 
-static bool keys_out_of_order(struct btree *b,
-			      const struct bkey_packed *prev,
-			      const struct bkey_packed *next,
-			      bool is_extents)
-{
-	struct bkey nextu = bkey_unpack_key(b, next);
-
-	return bkey_cmp_left_packed_byval(b, prev, bkey_start_pos(&nextu)) > 0 ||
-		((is_extents
-		  ? !bkey_deleted(next)
-		  : !bkey_deleted(prev)) &&
-		 !bkey_cmp_packed(b, prev, next));
-}
-
 void __bch2_verify_btree_nr_keys(struct btree *b)
 {
 	struct bset_tree *t;
@@ -150,16 +139,21 @@ void __bch2_verify_btree_nr_keys(struct btree *b)
 	BUG_ON(memcmp(&nr, &b->nr, sizeof(nr)));
 }
 
-static void bch2_btree_node_iter_next_check(struct btree_node_iter *iter,
-					   struct btree *b,
-					   struct bkey_packed *k)
+static void bch2_btree_node_iter_next_check(struct btree_node_iter *_iter,
+					    struct btree *b)
 {
-	const struct bkey_packed *n = bch2_btree_node_iter_peek_all(iter, b);
+	struct btree_node_iter iter = *_iter;
+	const struct bkey_packed *k, *n;
+
+	k = bch2_btree_node_iter_peek_all(&iter, b);
+	__bch2_btree_node_iter_advance(&iter, b);
+	n = bch2_btree_node_iter_peek_all(&iter, b);
 
 	bkey_unpack_key(b, k);
 
 	if (n &&
-	    keys_out_of_order(b, k, n, iter->is_extents)) {
+	    __btree_node_iter_cmp(b, k, n) > 0) {
+		struct btree_node_iter_set *set;
 		struct bkey ku = bkey_unpack_key(b, k);
 		struct bkey nu = bkey_unpack_key(b, n);
 		char buf1[80], buf2[80];
@@ -167,12 +161,22 @@ static void bch2_btree_node_iter_next_check(struct btree_node_iter *iter,
 		bch2_dump_btree_node(b);
 		bch2_bkey_to_text(buf1, sizeof(buf1), &ku);
 		bch2_bkey_to_text(buf2, sizeof(buf2), &nu);
-		panic("out of order/overlapping:\n%s\n%s\n", buf1, buf2);
+		printk(KERN_ERR "out of order/overlapping:\n%s\n%s\n",
+		       buf1, buf2);
+		printk(KERN_ERR "iter was:");
+
+		btree_node_iter_for_each(_iter, set) {
+			struct bkey_packed *k = __btree_node_offset_to_key(b, set->k);
+			struct bset_tree *t = bch2_bkey_to_bset(b, k);
+			printk(" [%zi %zi]", t - b->set,
+			       k->_data - bset(b, t)->_data);
+		}
+		panic("\n");
 	}
 }
 
 void bch2_btree_node_iter_verify(struct btree_node_iter *iter,
-				struct btree *b)
+				 struct btree *b)
 {
 	struct btree_node_iter_set *set, *s2;
 	struct bset_tree *t;
@@ -196,72 +200,72 @@ found:
 	/* Verify iterator is sorted: */
 	btree_node_iter_for_each(iter, set)
 		BUG_ON(set != iter->data &&
-		       btree_node_iter_cmp(iter, b, set[-1], set[0]) > 0);
+		       btree_node_iter_cmp(b, set[-1], set[0]) > 0);
+}
+
+void bch2_verify_insert_pos(struct btree *b, struct bkey_packed *where,
+			    struct bkey_packed *insert, unsigned clobber_u64s)
+{
+	struct bset_tree *t = bch2_bkey_to_bset(b, where);
+	struct bkey_packed *prev = bch2_bkey_prev_all(b, t, where);
+	struct bkey_packed *next = (void *) (where->_data + clobber_u64s);
+#if 0
+	BUG_ON(prev &&
+	       __btree_node_iter_cmp(b, prev, insert) > 0);
+#else
+	if (prev &&
+	    __btree_node_iter_cmp(b, prev, insert) > 0) {
+		struct bkey k1 = bkey_unpack_key(b, prev);
+		struct bkey k2 = bkey_unpack_key(b, insert);
+		char buf1[100];
+		char buf2[100];
+
+		bch2_dump_btree_node(b);
+		bch2_bkey_to_text(buf1, sizeof(buf1), &k1);
+		bch2_bkey_to_text(buf2, sizeof(buf2), &k2);
+
+		panic("prev > insert:\n"
+		      "prev    key %5u %s\n"
+		      "insert  key %5u %s\n",
+		       __btree_node_key_to_offset(b, prev), buf1,
+		       __btree_node_key_to_offset(b, insert), buf2);
+	}
+#endif
+#if 0
+	BUG_ON(next != btree_bkey_last(b, t) &&
+	       __btree_node_iter_cmp(b, insert, next) > 0);
+#else
+	if (next != btree_bkey_last(b, t) &&
+	    __btree_node_iter_cmp(b, insert, next) > 0) {
+		struct bkey k1 = bkey_unpack_key(b, insert);
+		struct bkey k2 = bkey_unpack_key(b, next);
+		char buf1[100];
+		char buf2[100];
+
+		bch2_dump_btree_node(b);
+		bch2_bkey_to_text(buf1, sizeof(buf1), &k1);
+		bch2_bkey_to_text(buf2, sizeof(buf2), &k2);
+
+		panic("insert > next:\n"
+		      "insert  key %5u %s\n"
+		      "next    key %5u %s\n",
+		       __btree_node_key_to_offset(b, insert), buf1,
+		       __btree_node_key_to_offset(b, next), buf2);
+	}
+#endif
 }
 
 void bch2_verify_key_order(struct btree *b,
-			  struct btree_node_iter *iter,
-			  struct bkey_packed *where)
+			   struct btree_node_iter *_iter,
+			   struct bkey_packed *where)
 {
-	struct bset_tree *t = bch2_bkey_to_bset(b, where);
-	struct bkey_packed *k, *prev;
-	struct bkey uk, uw = bkey_unpack_key(b, where);
-
-	k = bch2_bkey_prev_all(b, t, where);
-	if (k &&
-	    keys_out_of_order(b, k, where, iter->is_extents)) {
-		char buf1[100], buf2[100];
-
-		bch2_dump_btree_node(b);
-		uk = bkey_unpack_key(b, k);
-		bch2_bkey_to_text(buf1, sizeof(buf1), &uk);
-		bch2_bkey_to_text(buf2, sizeof(buf2), &uw);
-		panic("out of order with prev:\n%s\n%s\n",
-		      buf1, buf2);
-	}
-
-	k = bkey_next(where);
-	BUG_ON(k != btree_bkey_last(b, t) &&
-	       keys_out_of_order(b, where, k, iter->is_extents));
-
-	for_each_bset(b, t) {
-		if (where >= btree_bkey_first(b, t) ||
-		    where < btree_bkey_last(b, t))
-			continue;
-
-		k = bch2_btree_node_iter_bset_pos(iter, b, t);
-
-		if (k == btree_bkey_last(b, t))
-			k = bch2_bkey_prev_all(b, t, k);
-
-		while (bkey_cmp_left_packed_byval(b, k, bkey_start_pos(&uw)) > 0 &&
-		       (prev = bch2_bkey_prev_all(b, t, k)))
-			k = prev;
-
-		for (;
-		     k != btree_bkey_last(b, t);
-		     k = bkey_next(k)) {
-			uk = bkey_unpack_key(b, k);
-
-			if (iter->is_extents) {
-				BUG_ON(!(bkey_cmp(uw.p, bkey_start_pos(&uk)) <= 0 ||
-					 bkey_cmp(uk.p, bkey_start_pos(&uw)) <= 0));
-			} else {
-				BUG_ON(!bkey_cmp(uw.p, uk.p) &&
-				       !bkey_deleted(&uk));
-			}
-
-			if (bkey_cmp(uw.p, bkey_start_pos(&uk)) <= 0)
-				break;
-		}
-	}
+	bch2_verify_insert_pos(b, where, where, where->u64s);
 }
 
 #else
 
 static inline void bch2_btree_node_iter_next_check(struct btree_node_iter *iter,
-						   struct btree *b,
-						   struct bkey_packed *k) {}
+						   struct btree *b) {}
 
 #endif
 
@@ -1229,6 +1233,7 @@ void bch2_bset_insert(struct btree *b,
 	struct bkey_packed packed, *src = bkey_to_packed(insert);
 
 	bch2_bset_verify_rw_aux_tree(b, t);
+	bch2_verify_insert_pos(b, where, bkey_to_packed(insert), clobber_u64s);
 
 	if (bch2_bkey_pack_key(&packed, &insert->k, f))
 		src = &packed;
@@ -1255,7 +1260,6 @@ void bch2_bset_insert(struct btree *b,
 
 	bch2_bset_fix_lookup_table(b, t, where, clobber_u64s, src->u64s);
 
-	bch2_verify_key_order(b, iter, where);
 	bch2_verify_btree_nr_keys(b);
 }
 
@@ -1461,7 +1465,7 @@ void bch2_btree_node_iter_push(struct btree_node_iter *iter,
 noinline __flatten __attribute__((cold))
 static void btree_node_iter_init_pack_failed(struct btree_node_iter *iter,
 			      struct btree *b, struct bpos search,
-			      bool strictly_greater, bool is_extents)
+			      bool strictly_greater)
 {
 	struct bset_tree *t;
 
@@ -1518,7 +1522,7 @@ static void btree_node_iter_init_pack_failed(struct btree_node_iter *iter,
  */
 void bch2_btree_node_iter_init(struct btree_node_iter *iter,
 			       struct btree *b, struct bpos search,
-			       bool strictly_greater, bool is_extents)
+			       bool strictly_greater)
 {
 	struct bset_tree *t;
 	struct bkey_packed p, *packed_search = NULL;
@@ -1526,7 +1530,7 @@ void bch2_btree_node_iter_init(struct btree_node_iter *iter,
 	EBUG_ON(bkey_cmp(search, b->data->min_key) < 0);
 	bset_aux_tree_verify(b);
 
-	__bch2_btree_node_iter_init(iter, is_extents);
+	memset(iter, 0, sizeof(*iter));
 
 	switch (bch2_bkey_pack_pos_lossy(&p, search, b)) {
 	case BKEY_PACK_POS_EXACT:
@@ -1537,7 +1541,7 @@ void bch2_btree_node_iter_init(struct btree_node_iter *iter,
 		break;
 	case BKEY_PACK_POS_FAIL:
 		btree_node_iter_init_pack_failed(iter, b, search,
-					strictly_greater, is_extents);
+						 strictly_greater);
 		return;
 	}
 
@@ -1552,12 +1556,11 @@ void bch2_btree_node_iter_init(struct btree_node_iter *iter,
 }
 
 void bch2_btree_node_iter_init_from_start(struct btree_node_iter *iter,
-					  struct btree *b,
-					  bool is_extents)
+					  struct btree *b)
 {
 	struct bset_tree *t;
 
-	__bch2_btree_node_iter_init(iter, is_extents);
+	memset(iter, 0, sizeof(*iter));
 
 	for_each_bset(b, t)
 		__bch2_btree_node_iter_push(iter, b,
@@ -1585,7 +1588,7 @@ static inline bool btree_node_iter_sort_two(struct btree_node_iter *iter,
 {
 	bool ret;
 
-	if ((ret = (btree_node_iter_cmp(iter, b,
+	if ((ret = (btree_node_iter_cmp(b,
 					iter->data[first],
 					iter->data[first + 1]) > 0)))
 		swap(iter->data[first], iter->data[first + 1]);
@@ -1640,23 +1643,14 @@ static inline void __bch2_btree_node_iter_advance(struct btree_node_iter *iter,
 	btree_node_iter_sort_two(iter, b, 1);
 }
 
-/**
- * bch_btree_node_iter_advance - advance @iter by one key
- *
- * Doesn't do debugchecks - for cases where (insert_fixup_extent()) a bset might
- * momentarily have out of order extents.
- */
 void bch2_btree_node_iter_advance(struct btree_node_iter *iter,
 				  struct btree *b)
 {
 #ifdef CONFIG_BCACHEFS_DEBUG
-	struct bkey_packed *k = bch2_btree_node_iter_peek_all(iter, b);
-
-	__bch2_btree_node_iter_advance(iter, b);
-	bch2_btree_node_iter_next_check(iter, b, k);
-#else
-	__bch2_btree_node_iter_advance(iter, b);
+	bch2_btree_node_iter_verify(iter, b);
+	bch2_btree_node_iter_next_check(iter, b);
 #endif
+	__bch2_btree_node_iter_advance(iter, b);
 }
 
 static inline unsigned __btree_node_iter_used(struct btree_node_iter *iter)
@@ -1689,8 +1683,7 @@ struct bkey_packed *bch2_btree_node_iter_prev_filter(struct btree_node_iter *ite
 			bch2_btree_node_iter_bset_pos(iter, b, t),
 			min_key_type);
 		if (k &&
-		    (!prev || __btree_node_iter_cmp(iter->is_extents, b,
-						    k, prev) > 0)) {
+		    (!prev || __btree_node_iter_cmp(b, k, prev) > 0)) {
 			prev = k;
 			end = t->end_offset;
 		}
@@ -1723,11 +1716,11 @@ out:
 		struct btree_node_iter iter2 = *iter;
 
 		if (prev)
-			bch2_btree_node_iter_advance(&iter2, b);
+			__bch2_btree_node_iter_advance(&iter2, b);
 
 		while ((k = bch2_btree_node_iter_peek_all(&iter2, b)) != orig_pos) {
 			BUG_ON(k->type >= min_key_type);
-			bch2_btree_node_iter_advance(&iter2, b);
+			__bch2_btree_node_iter_advance(&iter2, b);
 		}
 	}
 
diff --git a/fs/bcachefs/bset.h b/fs/bcachefs/bset.h
index 2fa71d7c0e8a..0787030ccc7e 100644
--- a/fs/bcachefs/bset.h
+++ b/fs/bcachefs/bset.h
@@ -369,6 +369,17 @@ static inline int bkey_cmp_p_or_unp(const struct btree *b,
 	return __bch2_bkey_cmp_left_packed_format_checked(b, l, r);
 }
 
+/* Returns true if @k is after iterator position @pos */
+static inline bool btree_iter_pos_cmp(struct btree_iter *iter,
+				      const struct bkey *k)
+{
+	int cmp = bkey_cmp(k->p, iter->pos);
+
+	return cmp > 0 ||
+		(cmp == 0 &&
+		 !(iter->flags & BTREE_ITER_IS_EXTENTS) && !bkey_deleted(k));
+}
+
 /* Returns true if @k is after iterator position @pos */
 static inline bool btree_iter_pos_cmp_packed(const struct btree *b,
 					     struct bpos *pos,
@@ -419,7 +430,7 @@ enum bch_extent_overlap {
 
 /* Returns how k overlaps with m */
 static inline enum bch_extent_overlap bch2_extent_overlap(const struct bkey *k,
-							 const struct bkey *m)
+							  const struct bkey *m)
 {
 	int cmp1 = bkey_cmp(k->p, m->p) < 0;
 	int cmp2 = bkey_cmp(bkey_start_pos(k),
@@ -430,20 +441,13 @@ static inline enum bch_extent_overlap bch2_extent_overlap(const struct bkey *k,
 
 /* Btree key iteration */
 
-static inline void __bch2_btree_node_iter_init(struct btree_node_iter *iter,
-					      bool is_extents)
-{
-	iter->is_extents = is_extents;
-	memset(iter->data, 0, sizeof(iter->data));
-}
-
 void bch2_btree_node_iter_push(struct btree_node_iter *, struct btree *,
 			      const struct bkey_packed *,
 			      const struct bkey_packed *);
 void bch2_btree_node_iter_init(struct btree_node_iter *, struct btree *,
-			      struct bpos, bool, bool);
+			       struct bpos, bool);
 void bch2_btree_node_iter_init_from_start(struct btree_node_iter *,
-					 struct btree *, bool);
+					  struct btree *);
 struct bkey_packed *bch2_btree_node_iter_bset_pos(struct btree_node_iter *,
 						 struct btree *,
 						 struct bset_tree *);
@@ -470,32 +474,21 @@ static inline bool bch2_btree_node_iter_end(struct btree_node_iter *iter)
 	return __btree_node_iter_set_end(iter, 0);
 }
 
-static inline int __btree_node_iter_cmp(bool is_extents,
-					struct btree *b,
-					struct bkey_packed *l,
-					struct bkey_packed *r)
+static inline int __btree_node_iter_cmp(struct btree *b,
+					const struct bkey_packed *l,
+					const struct bkey_packed *r)
 {
-	/*
-	 * For non extents, when keys compare equal the deleted keys have to
-	 * come first - so that bch2_btree_node_iter_next_check() can detect
-	 * duplicate nondeleted keys (and possibly other reasons?)
-	 *
-	 * For extents, bkey_deleted() is used as a proxy for k->size == 0, so
-	 * deleted keys have to sort last.
-	 */
+	/* When keys compare equal deleted keys come first */
 	return bkey_cmp_packed(b, l, r)
-		?: (is_extents
-		    ? (int) bkey_deleted(l) - (int) bkey_deleted(r)
-		    : (int) bkey_deleted(r) - (int) bkey_deleted(l))
+		?: (int) bkey_deleted(r) - (int) bkey_deleted(l)
 		?: (l > r) - (l < r);
 }
 
-static inline int btree_node_iter_cmp(struct btree_node_iter *iter,
-				      struct btree *b,
+static inline int btree_node_iter_cmp(struct btree *b,
 				      struct btree_node_iter_set l,
 				      struct btree_node_iter_set r)
 {
-	return __btree_node_iter_cmp(iter->is_extents, b,
+	return __btree_node_iter_cmp(b,
 			__btree_node_offset_to_key(b, l.k),
 			__btree_node_offset_to_key(b, r.k));
 }
@@ -582,21 +575,12 @@ bch2_btree_node_iter_prev(struct btree_node_iter *iter, struct btree *b)
 	return bch2_btree_node_iter_prev_filter(iter, b, KEY_TYPE_DISCARD + 1);
 }
 
-/*
- * Iterates over all _live_ keys - skipping deleted (and potentially
- * overlapping) keys
- */
-#define for_each_btree_node_key(b, k, iter, _is_extents)		\
-	for (bch2_btree_node_iter_init_from_start((iter), (b), (_is_extents));\
-	     ((k) = bch2_btree_node_iter_peek(iter, b));			\
-	     bch2_btree_node_iter_advance(iter, b))
-
 struct bkey_s_c bch2_btree_node_iter_peek_unpack(struct btree_node_iter *,
 						struct btree *,
 						struct bkey *);
 
-#define for_each_btree_node_key_unpack(b, k, iter, _is_extents, unpacked)\
-	for (bch2_btree_node_iter_init_from_start((iter), (b), (_is_extents));\
+#define for_each_btree_node_key_unpack(b, k, iter, unpacked)		\
+	for (bch2_btree_node_iter_init_from_start((iter), (b));		\
 	     (k = bch2_btree_node_iter_peek_unpack((iter), (b), (unpacked))).k;\
 	     bch2_btree_node_iter_advance(iter, b))
 
@@ -646,6 +630,8 @@ void bch2_dump_btree_node_iter(struct btree *, struct btree_node_iter *);
 
 void __bch2_verify_btree_nr_keys(struct btree *);
 void bch2_btree_node_iter_verify(struct btree_node_iter *, struct btree *);
+void bch2_verify_insert_pos(struct btree *, struct bkey_packed *,
+			    struct bkey_packed *, unsigned);
 void bch2_verify_key_order(struct btree *, struct btree_node_iter *,
 			  struct bkey_packed *);
 
@@ -654,6 +640,10 @@ void bch2_verify_key_order(struct btree *, struct btree_node_iter *,
 static inline void __bch2_verify_btree_nr_keys(struct btree *b) {}
 static inline void bch2_btree_node_iter_verify(struct btree_node_iter *iter,
 					      struct btree *b) {}
+static inline void bch2_verify_insert_pos(struct btree *b,
+					  struct bkey_packed *where,
+					  struct bkey_packed *insert,
+					  unsigned clobber_u64s) {}
 static inline void bch2_verify_key_order(struct btree *b,
 					struct btree_node_iter *iter,
 					struct bkey_packed *where) {}
diff --git a/fs/bcachefs/btree_gc.c b/fs/bcachefs/btree_gc.c
index 1fbb9c657fc6..2526118fe9ce 100644
--- a/fs/bcachefs/btree_gc.c
+++ b/fs/bcachefs/btree_gc.c
@@ -217,7 +217,6 @@ static unsigned btree_gc_mark_node(struct bch_fs *c, struct btree *b)
 
 	if (btree_node_has_ptrs(b))
 		for_each_btree_node_key_unpack(b, k, &iter,
-					       btree_node_is_extents(b),
 					       &unpacked) {
 			bch2_bkey_debugcheck(c, b, k);
 			stale = max(stale, bch2_gc_mark_key(c, type, k, 0));
@@ -1044,7 +1043,6 @@ static int bch2_initial_gc_btree(struct bch_fs *c, enum btree_id id)
 			struct bkey_s_c k;
 
 			for_each_btree_node_key_unpack(b, k, &node_iter,
-						       btree_node_is_extents(b),
 						       &unpacked) {
 				ret = bch2_btree_mark_key_initial(c,
 							btree_node_type(b), k);
diff --git a/fs/bcachefs/btree_io.c b/fs/bcachefs/btree_io.c
index 5c36acef2b13..889870582566 100644
--- a/fs/bcachefs/btree_io.c
+++ b/fs/bcachefs/btree_io.c
@@ -22,7 +22,7 @@
 /* btree_node_iter_large: */
 
 #define btree_node_iter_cmp_heap(h, _l, _r)				\
-	__btree_node_iter_cmp((iter)->is_extents, b,			\
+	__btree_node_iter_cmp(b,					\
 			       __btree_node_offset_to_key(b, (_l).k),	\
 			       __btree_node_offset_to_key(b, (_r).k))
 
@@ -248,6 +248,9 @@ static unsigned sort_extent_whiteouts(struct bkey_packed *dst,
 	sort_iter_sort(iter, sort_extent_whiteouts_cmp);
 
 	while ((in = sort_iter_next(iter, sort_extent_whiteouts_cmp))) {
+		if (bkey_deleted(in))
+			continue;
+
 		EBUG_ON(bkeyp_val_u64s(f, in));
 		EBUG_ON(in->type != KEY_TYPE_DISCARD);
 
@@ -785,8 +788,7 @@ void bch2_btree_sort_into(struct bch_fs *c,
 
 	bch2_bset_set_no_aux_tree(dst, dst->set);
 
-	bch2_btree_node_iter_init_from_start(&src_iter, src,
-					    btree_node_is_extents(src));
+	bch2_btree_node_iter_init_from_start(&src_iter, src);
 
 	if (btree_node_ops(src)->key_normalize ||
 	    btree_node_ops(src)->key_merge)
@@ -1171,7 +1173,7 @@ int bch2_btree_node_read_done(struct bch_fs *c, struct btree *b, bool have_retry
 	int ret, retry_read = 0, write = READ;
 
 	iter = mempool_alloc(&c->fill_iter, GFP_NOIO);
-	__bch2_btree_node_iter_large_init(iter, btree_node_is_extents(b));
+	iter->used = 0;
 
 	if (bch2_meta_read_fault("btree"))
 		btree_err(BTREE_ERR_MUST_RETRY, c, b, NULL,
diff --git a/fs/bcachefs/btree_io.h b/fs/bcachefs/btree_io.h
index 0688ce420610..7835f8a9e3a0 100644
--- a/fs/bcachefs/btree_io.h
+++ b/fs/bcachefs/btree_io.h
@@ -146,20 +146,11 @@ ssize_t bch2_dirty_btree_nodes_print(struct bch_fs *, char *);
 /* Sorting */
 
 struct btree_node_iter_large {
-	u8		is_extents;
 	u16		used;
 
 	struct btree_node_iter_set data[MAX_BSETS];
 };
 
-static inline void
-__bch2_btree_node_iter_large_init(struct btree_node_iter_large *iter,
-				  bool is_extents)
-{
-	iter->used = 0;
-	iter->is_extents = is_extents;
-}
-
 void bch2_btree_node_iter_large_advance(struct btree_node_iter_large *,
 					struct btree *);
 
diff --git a/fs/bcachefs/btree_iter.c b/fs/bcachefs/btree_iter.c
index 8918268f99f4..9d92826181dc 100644
--- a/fs/bcachefs/btree_iter.c
+++ b/fs/bcachefs/btree_iter.c
@@ -375,14 +375,20 @@ static void __bch2_btree_iter_verify(struct btree_iter *iter,
 	struct btree_node_iter tmp = l->iter;
 	struct bkey_packed *k;
 
+	if (iter->uptodate > BTREE_ITER_NEED_PEEK)
+		return;
+
 	bch2_btree_node_iter_verify(&l->iter, b);
 
 	/*
 	 * For interior nodes, the iterator will have skipped past
 	 * deleted keys:
+	 *
+	 * For extents, the iterator may have skipped past deleted keys (but not
+	 * whiteouts)
 	 */
-	k = b->level
-		? bch2_btree_node_iter_prev(&tmp, b)
+	k = b->level || iter->flags & BTREE_ITER_IS_EXTENTS
+		? bch2_btree_node_iter_prev_filter(&tmp, b, KEY_TYPE_DISCARD)
 		: bch2_btree_node_iter_prev_all(&tmp, b);
 	if (k && btree_iter_pos_cmp_packed(b, &iter->pos, k,
 				iter->flags & BTREE_ITER_IS_EXTENTS)) {
@@ -390,7 +396,7 @@ static void __bch2_btree_iter_verify(struct btree_iter *iter,
 		struct bkey uk = bkey_unpack_key(b, k);
 
 		bch2_bkey_to_text(buf, sizeof(buf), &uk);
-		panic("prev key should be before after pos:\n%s\n%llu:%llu\n",
+		panic("prev key should be before iter pos:\n%s\n%llu:%llu\n",
 		      buf, iter->pos.inode, iter->pos.offset);
 	}
 
@@ -401,15 +407,16 @@ static void __bch2_btree_iter_verify(struct btree_iter *iter,
 		struct bkey uk = bkey_unpack_key(b, k);
 
 		bch2_bkey_to_text(buf, sizeof(buf), &uk);
-		panic("next key should be before iter pos:\n%llu:%llu\n%s\n",
+		panic("iter should be after current key:\n"
+		      "iter pos %llu:%llu\n"
+		      "cur key  %s\n",
 		      iter->pos.inode, iter->pos.offset, buf);
 	}
 
-	if (iter->uptodate == BTREE_ITER_UPTODATE &&
-	    (iter->flags & BTREE_ITER_TYPE) != BTREE_ITER_NODES) {
-		BUG_ON(!bkey_whiteout(&iter->k) &&
-		       bch2_btree_node_iter_end(&l->iter));
-	}
+	BUG_ON(iter->uptodate == BTREE_ITER_UPTODATE &&
+	       (iter->flags & BTREE_ITER_TYPE) == BTREE_ITER_KEYS &&
+	       !bkey_whiteout(&iter->k) &&
+	       bch2_btree_node_iter_end(&l->iter));
 }
 
 void bch2_btree_iter_verify(struct btree_iter *iter, struct btree *b)
@@ -420,6 +427,11 @@ void bch2_btree_iter_verify(struct btree_iter *iter, struct btree *b)
 		__bch2_btree_iter_verify(linked, b);
 }
 
+#else
+
+static inline void __bch2_btree_iter_verify(struct btree_iter *iter,
+					    struct btree *b) {}
+
 #endif
 
 static void __bch2_btree_node_iter_fix(struct btree_iter *iter,
@@ -434,7 +446,7 @@ static void __bch2_btree_node_iter_fix(struct btree_iter *iter,
 	struct btree_node_iter_set *set;
 	unsigned offset = __btree_node_key_to_offset(b, where);
 	int shift = new_u64s - clobber_u64s;
-	unsigned old_end = (int) __btree_node_key_to_offset(b, end) - shift;
+	unsigned old_end = t->end_offset - shift;
 
 	btree_node_iter_for_each(node_iter, set)
 		if (set->end == old_end)
@@ -456,7 +468,7 @@ static void __bch2_btree_node_iter_fix(struct btree_iter *iter,
 	}
 	return;
 found:
-	set->end = (int) set->end + shift;
+	set->end = t->end_offset;
 
 	/* Iterator hasn't gotten to the key that changed yet: */
 	if (set->k < offset)
@@ -517,8 +529,7 @@ iter_current_key_not_modified:
 			k = bch2_bkey_prev_all(b, t,
 				bch2_btree_node_iter_bset_pos(node_iter, b, t));
 			if (k &&
-			    __btree_node_iter_cmp(node_iter, b,
-						  k, where) > 0) {
+			    __btree_node_iter_cmp(b, k, where) > 0) {
 				struct btree_node_iter_set *set;
 				unsigned offset =
 					__btree_node_key_to_offset(b, bkey_next(k));
@@ -557,10 +568,6 @@ void bch2_btree_node_iter_fix(struct btree_iter *iter,
 		__bch2_btree_node_iter_fix(linked, b,
 					  &linked->l[b->level].iter, t,
 					  where, clobber_u64s, new_u64s);
-
-	/* interior node iterators are... special... */
-	if (!b->level)
-		bch2_btree_iter_verify(iter, b);
 }
 
 static inline struct bkey_s_c __btree_iter_unpack(struct btree_iter *iter,
@@ -647,17 +654,6 @@ static void btree_iter_verify_new_node(struct btree_iter *iter, struct btree *b)
 		btree_node_unlock(iter, b->level + 1);
 }
 
-/* Returns true if @k is after iterator position @pos */
-static inline bool btree_iter_pos_cmp(struct btree_iter *iter,
-				      const struct bkey *k)
-{
-	int cmp = bkey_cmp(k->p, iter->pos);
-
-	return cmp > 0 ||
-		(cmp == 0 &&
-		 !(iter->flags & BTREE_ITER_IS_EXTENTS) && !bkey_deleted(k));
-}
-
 static inline bool btree_iter_pos_after_node(struct btree_iter *iter,
 					     struct btree *b)
 {
@@ -679,8 +675,7 @@ static inline void __btree_iter_init(struct btree_iter *iter,
 	struct btree_iter_level *l = &iter->l[b->level];
 
 	bch2_btree_node_iter_init(&l->iter, b, iter->pos,
-				  iter->flags & BTREE_ITER_IS_EXTENTS,
-				  btree_node_is_extents(b));
+				  iter->flags & BTREE_ITER_IS_EXTENTS);
 
 	/* Skip to first non whiteout: */
 	if (b->level)
@@ -1022,7 +1017,9 @@ int __must_check __bch2_btree_iter_traverse(struct btree_iter *iter)
 	}
 
 	iter->uptodate = BTREE_ITER_NEED_PEEK;
+
 	bch2_btree_iter_verify_locks(iter);
+	__bch2_btree_iter_verify(iter, iter->l[iter->level].b);
 	return 0;
 }
 
@@ -1363,9 +1360,10 @@ struct bkey_s_c bch2_btree_iter_prev(struct btree_iter *iter)
 }
 
 static inline struct bkey_s_c
-__bch2_btree_iter_peek_slot(struct btree_iter *iter)
+__bch2_btree_iter_peek_slot_extents(struct btree_iter *iter)
 {
 	struct btree_iter_level *l = &iter->l[0];
+	struct btree_node_iter node_iter;
 	struct bkey_s_c k;
 	struct bkey n;
 	int ret;
@@ -1376,6 +1374,17 @@ recheck:
 	       bkey_cmp(bkey_start_pos(k.k), iter->pos) == 0)
 		__btree_iter_advance(l);
 
+	/*
+	 * iterator is now at the correct position for inserting at iter->pos,
+	 * but we need to keep iterating until we find the first non whiteout so
+	 * we know how big a hole we have, if any:
+	 */
+
+	node_iter = l->iter;
+	if (k.k && bkey_whiteout(k.k))
+		k = __btree_iter_unpack(iter, l, &iter->k,
+			bch2_btree_node_iter_peek(&node_iter, l->b));
+
 	/*
 	 * If we got to the end of the node, check if we need to traverse to the
 	 * next node:
@@ -1392,6 +1401,13 @@ recheck:
 	if (k.k &&
 	    !bkey_whiteout(k.k) &&
 	    bkey_cmp(bkey_start_pos(k.k), iter->pos) <= 0) {
+		/*
+		 * if we skipped forward to find the first non whiteout and
+		 * there _wasn't_ actually a hole, we want the iterator to be
+		 * pointed at the key we found:
+		 */
+		l->iter = node_iter;
+
 		EBUG_ON(bkey_cmp(k.k->p, iter->pos) < 0);
 		EBUG_ON(bkey_deleted(k.k));
 		iter->uptodate = BTREE_ITER_UPTODATE;
@@ -1399,36 +1415,39 @@ recheck:
 	}
 
 	/* hole */
+
+	/* holes can't span inode numbers: */
+	if (iter->pos.offset == KEY_OFFSET_MAX) {
+		if (iter->pos.inode == KEY_INODE_MAX)
+			return bkey_s_c_null;
+
+		iter->pos = bkey_successor(iter->pos);
+		goto recheck;
+	}
+
+	if (!k.k)
+		k.k = &l->b->key.k;
+
 	bkey_init(&n);
 	n.p = iter->pos;
+	bch2_key_resize(&n,
+			min_t(u64, KEY_SIZE_MAX,
+			      (k.k->p.inode == n.p.inode
+			       ? bkey_start_offset(k.k)
+			       : KEY_OFFSET_MAX) -
+			      n.p.offset));
 
-	if (iter->flags & BTREE_ITER_IS_EXTENTS) {
-		if (n.p.offset == KEY_OFFSET_MAX) {
-			if (n.p.inode == KEY_INODE_MAX)
-				return bkey_s_c_null;
+	//EBUG_ON(!n.size);
+	if (!n.size) {
+		char buf[100];
+		bch2_dump_btree_node(iter->l[0].b);
 
-			iter->pos = bkey_successor(iter->pos);
-			goto recheck;
-		}
-
-		if (k.k && bkey_whiteout(k.k)) {
-			struct btree_node_iter node_iter = l->iter;
-
-			k = __btree_iter_unpack(iter, l, &iter->k,
-				bch2_btree_node_iter_peek(&node_iter, l->b));
-		}
-
-		if (!k.k)
-			k.k = &l->b->key.k;
-
-		bch2_key_resize(&n,
-				min_t(u64, KEY_SIZE_MAX,
-				      (k.k->p.inode == n.p.inode
-				       ? bkey_start_offset(k.k)
-				       : KEY_OFFSET_MAX) -
-				      n.p.offset));
-
-		EBUG_ON(!n.size);
+		bch2_bkey_to_text(buf, sizeof(buf), k.k);
+		panic("iter at %llu:%llu\n"
+		      "next key %s\n",
+		      iter->pos.inode,
+		      iter->pos.offset,
+		      buf);
 	}
 
 	iter->k	= n;
@@ -1436,6 +1455,50 @@ recheck:
 	return (struct bkey_s_c) { &iter->k, NULL };
 }
 
+static inline struct bkey_s_c
+__bch2_btree_iter_peek_slot(struct btree_iter *iter)
+{
+	struct btree_iter_level *l = &iter->l[0];
+	struct bkey_s_c k;
+	int ret;
+
+	if (iter->flags & BTREE_ITER_IS_EXTENTS)
+		return __bch2_btree_iter_peek_slot_extents(iter);
+
+recheck:
+	while ((k = __btree_iter_peek_all(iter, l, &iter->k)).k &&
+	       bkey_deleted(k.k) &&
+	       bkey_cmp(k.k->p, iter->pos) == 0)
+		__btree_iter_advance(l);
+
+	/*
+	 * If we got to the end of the node, check if we need to traverse to the
+	 * next node:
+	 */
+	if (unlikely(!k.k && btree_iter_pos_after_node(iter, l->b))) {
+		btree_iter_set_dirty(iter, BTREE_ITER_NEED_TRAVERSE);
+		ret = bch2_btree_iter_traverse(iter);
+		if (unlikely(ret))
+			return bkey_s_c_err(ret);
+
+		goto recheck;
+	}
+
+	if (k.k &&
+	    !bkey_deleted(k.k) &&
+	    !bkey_cmp(iter->pos, k.k->p)) {
+		iter->uptodate = BTREE_ITER_UPTODATE;
+		return k;
+	} else {
+		/* hole */
+		bkey_init(&iter->k);
+		iter->k.p = iter->pos;
+
+		iter->uptodate = BTREE_ITER_UPTODATE;
+		return (struct bkey_s_c) { &iter->k, NULL };
+	}
+}
+
 struct bkey_s_c bch2_btree_iter_peek_slot(struct btree_iter *iter)
 {
 	int ret;
diff --git a/fs/bcachefs/btree_types.h b/fs/bcachefs/btree_types.h
index 5376388e91e6..d57ca3d08c16 100644
--- a/fs/bcachefs/btree_types.h
+++ b/fs/bcachefs/btree_types.h
@@ -176,8 +176,6 @@ struct btree_cache {
 };
 
 struct btree_node_iter {
-	u8		is_extents;
-
 	struct btree_node_iter_set {
 		u16	k, end;
 	} data[MAX_BSETS];
@@ -459,9 +457,6 @@ struct btree_root {
  * we're holding the write lock and we know what key is about to be overwritten:
  */
 
-struct btree_iter;
-struct btree_node_iter;
-
 enum btree_insert_ret {
 	BTREE_INSERT_OK,
 	/* extent spanned multiple leaf nodes: have to traverse to next node: */
diff --git a/fs/bcachefs/btree_update_interior.c b/fs/bcachefs/btree_update_interior.c
index b60eb3d33c7b..1fe6f1e3e843 100644
--- a/fs/bcachefs/btree_update_interior.c
+++ b/fs/bcachefs/btree_update_interior.c
@@ -35,7 +35,7 @@ static void btree_node_interior_verify(struct btree *b)
 
 	BUG_ON(!b->level);
 
-	bch2_btree_node_iter_init(&iter, b, b->key.k.p, false, false);
+	bch2_btree_node_iter_init(&iter, b, b->key.k.p, false);
 #if 1
 	BUG_ON(!(k = bch2_btree_node_iter_peek(&iter, b)) ||
 	       bkey_cmp_left_packed(b, k, &b->key.k.p));
@@ -1322,7 +1322,7 @@ static void btree_split_insert_keys(struct btree_update *as, struct btree *b,
 
 	BUG_ON(btree_node_type(b) != BKEY_TYPE_BTREE);
 
-	bch2_btree_node_iter_init(&node_iter, b, k->k.p, false, false);
+	bch2_btree_node_iter_init(&node_iter, b, k->k.p, false);
 
 	while (!bch2_keylist_empty(keys)) {
 		k = bch2_keylist_front(keys);
diff --git a/fs/bcachefs/btree_update_leaf.c b/fs/bcachefs/btree_update_leaf.c
index ce0223bd52b5..0ef519e8feed 100644
--- a/fs/bcachefs/btree_update_leaf.c
+++ b/fs/bcachefs/btree_update_leaf.c
@@ -64,7 +64,8 @@ bool bch2_btree_bset_insert_key(struct btree_iter *iter,
 			if (bkey_whiteout(&insert->k) && !k->needs_whiteout) {
 				bch2_bset_delete(b, k, clobber_u64s);
 				bch2_btree_node_iter_fix(iter, b, node_iter, t,
-							k, clobber_u64s, 0);
+							 k, clobber_u64s, 0);
+				bch2_btree_iter_verify(iter, b);
 				return true;
 			}
 
@@ -73,7 +74,8 @@ bool bch2_btree_bset_insert_key(struct btree_iter *iter,
 
 		k->type = KEY_TYPE_DELETED;
 		bch2_btree_node_iter_fix(iter, b, node_iter, t, k,
-					k->u64s, k->u64s);
+					 k->u64s, k->u64s);
+		bch2_btree_iter_verify(iter, b);
 
 		if (bkey_whiteout(&insert->k)) {
 			reserve_whiteout(b, k);
@@ -98,7 +100,8 @@ overwrite:
 	bch2_bset_insert(b, node_iter, k, insert, clobber_u64s);
 	if (k->u64s != clobber_u64s || bkey_whiteout(&insert->k))
 		bch2_btree_node_iter_fix(iter, b, node_iter, t, k,
-					clobber_u64s, k->u64s);
+					 clobber_u64s, k->u64s);
+	bch2_btree_iter_verify(iter, b);
 	return true;
 }
 
diff --git a/fs/bcachefs/extents.c b/fs/bcachefs/extents.c
index 803272b10e61..df04af882c16 100644
--- a/fs/bcachefs/extents.c
+++ b/fs/bcachefs/extents.c
@@ -858,30 +858,34 @@ void bch2_key_resize(struct bkey *k,
  * that we have to unpack the key, modify the unpacked key - then this
  * copies/repacks the unpacked to the original as necessary.
  */
-static bool __extent_save(struct btree *b, struct btree_node_iter *iter,
-			  struct bkey_packed *dst, struct bkey *src)
+static void extent_save(struct btree *b, struct bkey_packed *dst,
+			struct bkey *src)
 {
 	struct bkey_format *f = &b->format;
 	struct bkey_i *dst_unpacked;
-	bool ret;
 
-	if ((dst_unpacked = packed_to_bkey(dst))) {
+	if ((dst_unpacked = packed_to_bkey(dst)))
 		dst_unpacked->k = *src;
-		ret = true;
-	} else {
-		ret = bch2_bkey_pack_key(dst, src, f);
-	}
-
-	if (ret && iter)
-		bch2_verify_key_order(b, iter, dst);
-
-	return ret;
+	else
+		BUG_ON(!bch2_bkey_pack_key(dst, src, f));
 }
 
-static void extent_save(struct btree *b, struct btree_node_iter *iter,
-			struct bkey_packed *dst, struct bkey *src)
+static bool extent_i_save(struct btree *b, struct bkey_packed *dst,
+			  struct bkey_i *src)
 {
-	BUG_ON(!__extent_save(b, iter, dst, src));
+	struct bkey_format *f = &b->format;
+	struct bkey_i *dst_unpacked;
+	struct bkey_packed tmp;
+
+	if ((dst_unpacked = packed_to_bkey(dst)))
+		dst_unpacked->k = src->k;
+	else if (bch2_bkey_pack_key(&tmp, &src->k, f))
+		memcpy_u64s(dst, &tmp, f->key_u64s);
+	else
+		return false;
+
+	memcpy_u64s(bkeyp_val(f, dst), &src->v, bkey_val_u64s(&src->k));
+	return true;
 }
 
 /*
@@ -1010,7 +1014,7 @@ struct btree_nr_keys bch2_extent_sort_fix_overlapping(struct bch_fs *c,
 				sort_key_next(iter, b, _r);
 			} else {
 				__bch2_cut_front(l.k->p, r);
-				extent_save(b, NULL, rk, r.k);
+				extent_save(b, rk, r.k);
 			}
 
 			extent_sort_sift(iter, b, _r - iter->data);
@@ -1024,7 +1028,7 @@ struct btree_nr_keys bch2_extent_sort_fix_overlapping(struct bch_fs *c,
 			bch2_cut_back(bkey_start_pos(r.k), &tmp.k.k);
 
 			__bch2_cut_front(r.k->p, l);
-			extent_save(b, NULL, lk, l.k);
+			extent_save(b, lk, l.k);
 
 			extent_sort_sift(iter, b, 0);
 
@@ -1032,7 +1036,7 @@ struct btree_nr_keys bch2_extent_sort_fix_overlapping(struct bch_fs *c,
 					   bkey_to_packed(&tmp.k));
 		} else {
 			bch2_cut_back(bkey_start_pos(r.k), l.k);
-			extent_save(b, NULL, lk, l.k);
+			extent_save(b, lk, l.k);
 		}
 	}
 
@@ -1135,6 +1139,55 @@ extent_insert_should_stop(struct extent_insert_state *s)
 		return BTREE_INSERT_OK;
 }
 
+static void verify_extent_nonoverlapping(struct btree *b,
+					 struct btree_node_iter *_iter,
+					 struct bkey_i *insert)
+{
+#ifdef CONFIG_BCACHEFS_DEBUG
+	struct btree_node_iter iter;
+	struct bkey_packed *k;
+	struct bkey uk;
+
+	iter = *_iter;
+	k = bch2_btree_node_iter_prev_filter(&iter, b, KEY_TYPE_DISCARD);
+	BUG_ON(k &&
+	       (uk = bkey_unpack_key(b, k),
+		bkey_cmp(uk.p, bkey_start_pos(&insert->k)) > 0));
+
+	iter = *_iter;
+	k = bch2_btree_node_iter_peek_filter(&iter, b, KEY_TYPE_DISCARD);
+#if 0
+	BUG_ON(k &&
+	       (uk = bkey_unpack_key(b, k),
+		bkey_cmp(insert->k.p, bkey_start_pos(&uk))) > 0);
+#else
+	if (k &&
+	    (uk = bkey_unpack_key(b, k),
+	     bkey_cmp(insert->k.p, bkey_start_pos(&uk))) > 0) {
+		char buf1[100];
+		char buf2[100];
+
+		bch2_bkey_to_text(buf1, sizeof(buf1), &insert->k);
+		bch2_bkey_to_text(buf2, sizeof(buf2), &uk);
+
+		bch2_dump_btree_node(b);
+		panic("insert > next :\n"
+		      "insert %s\n"
+		      "next   %s\n",
+		      buf1, buf2);
+	}
+#endif
+
+#endif
+}
+
+static void verify_modified_extent(struct btree_iter *iter,
+				   struct bkey_packed *k)
+{
+	bch2_btree_iter_verify(iter, iter->l[0].b);
+	bch2_verify_insert_pos(iter->l[0].b, k, k, k->u64s);
+}
+
 static void extent_bset_insert(struct bch_fs *c, struct btree_iter *iter,
 			       struct bkey_i *insert)
 {
@@ -1148,6 +1201,14 @@ static void extent_bset_insert(struct bch_fs *c, struct btree_iter *iter,
 	unsigned clobber_u64s;
 
 	EBUG_ON(bkey_deleted(&insert->k) || !insert->k.size);
+	verify_extent_nonoverlapping(l->b, &l->iter, insert);
+
+	if (!prev) {
+		while ((prev = bch2_bkey_prev_all(l->b, t, where)) &&
+		       (bkey_cmp_left_packed(l->b, prev, &insert->k.p) ?:
+			((int) bkey_deleted(&insert->k) - (int) bkey_deleted(prev))) > 0)
+			where = prev;
+	}
 
 	if (prev)
 		where = bkey_next(prev);
@@ -1173,12 +1234,15 @@ static void extent_bset_insert(struct bch_fs *c, struct btree_iter *iter,
 
 	bch2_bset_insert(l->b, &l->iter, where, insert, clobber_u64s);
 	bch2_btree_node_iter_fix(iter, l->b, &l->iter, t, where,
-				clobber_u64s, where->u64s);
+				 clobber_u64s, where->u64s);
+	bch2_verify_key_order(l->b, &l->iter, where);
+	bch2_btree_iter_verify(iter, l->b);
 	return;
 drop_deleted_keys:
 	bch2_bset_delete(l->b, where, clobber_u64s);
 	bch2_btree_node_iter_fix(iter, l->b, &l->iter, t,
 				 where, clobber_u64s, 0);
+	bch2_btree_iter_verify(iter, l->b);
 }
 
 static void extent_insert_committed(struct extent_insert_state *s)
@@ -1226,8 +1290,10 @@ static void extent_insert_committed(struct extent_insert_state *s)
 
 	bch2_btree_journal_key(s->trans, iter, &split.k);
 
-	if (!s->deleting)
+	if (!s->deleting) {
+		bch2_btree_iter_set_pos_same_leaf(iter, s->committed);
 		extent_bset_insert(c, iter, &split.k);
+	}
 done:
 	bch2_btree_iter_set_pos_same_leaf(iter, s->committed);
 
@@ -1345,22 +1411,21 @@ extent_squash(struct extent_insert_state *s, struct bkey_i *insert,
 	struct btree_iter *iter = s->insert->iter;
 	struct btree_iter_level *l = &iter->l[0];
 	struct btree *b = l->b;
-	struct btree_node_iter *node_iter = &l->iter;
-	enum btree_insert_ret ret;
 
 	switch (overlap) {
 	case BCH_EXTENT_OVERLAP_FRONT:
 		/* insert overlaps with start of k: */
 		bch2_cut_subtract_front(s, insert->k.p, k);
 		BUG_ON(bkey_deleted(k.k));
-		extent_save(b, node_iter, _k, k.k);
+		extent_save(b, _k, k.k);
+		bch2_verify_key_order(b, &l->iter, _k);
 		break;
 
 	case BCH_EXTENT_OVERLAP_BACK:
 		/* insert overlaps with end of k: */
 		bch2_cut_subtract_back(s, bkey_start_pos(&insert->k), k);
 		BUG_ON(bkey_deleted(k.k));
-		extent_save(b, node_iter, _k, k.k);
+		extent_save(b, _k, k.k);
 
 		/*
 		 * As the auxiliary tree is indexed by the end of the
@@ -1368,46 +1433,31 @@ extent_squash(struct extent_insert_state *s, struct bkey_i *insert,
 		 * auxiliary tree.
 		 */
 		bch2_bset_fix_invalidated_key(b, t, _k);
-		bch2_btree_node_iter_fix(iter, b, node_iter, t,
-					_k, _k->u64s, _k->u64s);
+		bch2_btree_node_iter_fix(iter, b, &l->iter, t,
+					 _k, _k->u64s, _k->u64s);
+		bch2_verify_key_order(b, &l->iter, _k);
 		break;
 
 	case BCH_EXTENT_OVERLAP_ALL: {
-		struct bpos orig_pos = k.k->p;
-
 		/* The insert key completely covers k, invalidate k */
 		if (!bkey_whiteout(k.k))
 			btree_keys_account_key_drop(&b->nr,
 						t - b->set, _k);
 
 		bch2_drop_subtract(s, k);
-		k.k->p = bkey_start_pos(&insert->k);
-		if (!__extent_save(b, node_iter, _k, k.k)) {
-			/*
-			 * Couldn't repack: we aren't necessarily able
-			 * to repack if the new key is outside the range
-			 * of the old extent, so we have to split
-			 * @insert:
-			 */
-			k.k->p = orig_pos;
-			extent_save(b, node_iter, _k, k.k);
 
-			ret = extent_insert_advance_pos(s, k.s_c);
-			if (ret != BTREE_INSERT_OK)
-				return ret;
+		if (t == bset_tree_last(l->b)) {
+			unsigned u64s = _k->u64s;
 
-			extent_insert_committed(s);
-			/*
-			 * We split and inserted upto at k.k->p - that
-			 * has to coincide with iter->pos, so that we
-			 * don't have anything more we have to insert
-			 * until we recheck our journal reservation:
-			 */
-			EBUG_ON(bkey_cmp(s->committed, k.k->p));
+			bch2_bset_delete(l->b, _k, _k->u64s);
+			bch2_btree_node_iter_fix(iter, b, &l->iter, t,
+						 _k, u64s, 0);
+			bch2_btree_iter_verify(iter, b);
 		} else {
-			bch2_bset_fix_invalidated_key(b, t, _k);
-			bch2_btree_node_iter_fix(iter, b, node_iter, t,
-						_k, _k->u64s, _k->u64s);
+			extent_save(b, _k, k.k);
+			bch2_btree_node_iter_fix(iter, b, &l->iter, t,
+						 _k, _k->u64s, _k->u64s);
+			bch2_verify_key_order(b, &l->iter, _k);
 		}
 
 		break;
@@ -1436,7 +1486,8 @@ extent_squash(struct extent_insert_state *s, struct bkey_i *insert,
 
 		bch2_cut_subtract_front(s, insert->k.p, k);
 		BUG_ON(bkey_deleted(k.k));
-		extent_save(b, node_iter, _k, k.k);
+		extent_save(b, _k, k.k);
+		bch2_verify_key_order(b, &l->iter, _k);
 
 		bch2_add_sectors(s, bkey_i_to_s_c(&split.k),
 				bkey_start_offset(&split.k.k),
@@ -1450,26 +1501,20 @@ extent_squash(struct extent_insert_state *s, struct bkey_i *insert,
 }
 
 static enum btree_insert_ret
-__bch2_delete_fixup_extent(struct extent_insert_state *s)
+__bch2_insert_fixup_extent(struct extent_insert_state *s)
 {
 	struct bch_fs *c = s->trans->c;
 	struct btree_iter *iter = s->insert->iter;
 	struct btree_iter_level *l = &iter->l[0];
 	struct btree *b = l->b;
-	struct btree_node_iter *node_iter = &l->iter;
 	struct bkey_packed *_k;
 	struct bkey unpacked;
 	struct bkey_i *insert = s->insert->k;
 	enum btree_insert_ret ret = BTREE_INSERT_OK;
 
-	EBUG_ON(bkey_cmp(iter->pos, bkey_start_pos(&insert->k)));
-
-	s->whiteout = *insert;
-	s->whiteout.k.type = KEY_TYPE_DISCARD;
-
 	while (bkey_cmp(s->committed, insert->k.p) < 0 &&
 	       (ret = extent_insert_should_stop(s)) == BTREE_INSERT_OK &&
-	       (_k = bch2_btree_node_iter_peek_all(node_iter, b))) {
+	       (_k = bch2_btree_node_iter_peek_filter(&l->iter, b, KEY_TYPE_DISCARD))) {
 		struct bset_tree *t = bch2_bkey_to_bset(b, _k);
 		struct bkey_s k = __bkey_disassemble(b, _k, &unpacked);
 		enum bch_extent_overlap overlap;
@@ -1480,112 +1525,92 @@ __bch2_delete_fixup_extent(struct extent_insert_state *s)
 		if (bkey_cmp(bkey_start_pos(k.k), insert->k.p) >= 0)
 			break;
 
-		if (bkey_whiteout(k.k)) {
-			s->committed = bpos_min(insert->k.p, k.k->p);
-			goto next;
-		}
-
-		overlap = bch2_extent_overlap(&insert->k, k.k);
-
 		ret = extent_insert_advance_pos(s, k.s_c);
 		if (ret)
 			break;
 
-		s->do_journal = true;
+		overlap = bch2_extent_overlap(&insert->k, k.k);
 
-		if (overlap == BCH_EXTENT_OVERLAP_ALL) {
-			btree_keys_account_key_drop(&b->nr,
-						t - b->set, _k);
-			bch2_subtract_sectors(s, k.s_c,
-					     bkey_start_offset(k.k), k.k->size);
-			_k->type = KEY_TYPE_DISCARD;
-			reserve_whiteout(b, _k);
-		} else if (k.k->needs_whiteout ||
-			   bkey_written(b, _k)) {
-			struct bkey_i discard = *insert;
+		if (!s->deleting) {
+			if (k.k->needs_whiteout || bkey_written(b, _k))
+				insert->k.needs_whiteout = true;
 
-			discard.k.type = KEY_TYPE_DISCARD;
-
-			switch (overlap) {
-			case BCH_EXTENT_OVERLAP_FRONT:
-				bch2_cut_front(bkey_start_pos(k.k), &discard);
-				break;
-			case BCH_EXTENT_OVERLAP_BACK:
-				bch2_cut_back(k.k->p, &discard.k);
-				break;
-			default:
-				break;
+			if (overlap == BCH_EXTENT_OVERLAP_ALL &&
+			    bkey_whiteout(k.k) &&
+			    k.k->needs_whiteout) {
+				unreserve_whiteout(b, _k);
+				_k->needs_whiteout = false;
 			}
 
-			discard.k.needs_whiteout = true;
-
 			ret = extent_squash(s, insert, t, _k, k, overlap);
-			BUG_ON(ret != BTREE_INSERT_OK);
-
-			extent_bset_insert(c, iter, &discard);
 		} else {
-			ret = extent_squash(s, insert, t, _k, k, overlap);
-			BUG_ON(ret != BTREE_INSERT_OK);
-		}
+			if (bkey_whiteout(k.k))
+				goto next;
+
+			s->do_journal = true;
+
+			if (overlap == BCH_EXTENT_OVERLAP_ALL) {
+				btree_keys_account_key_drop(&b->nr,
+							t - b->set, _k);
+				bch2_subtract_sectors(s, k.s_c,
+						     bkey_start_offset(k.k), k.k->size);
+				_k->type = KEY_TYPE_DISCARD;
+				reserve_whiteout(b, _k);
+			} else if (k.k->needs_whiteout ||
+				   bkey_written(b, _k)) {
+				struct bkey_i discard = *insert;
+
+				discard.k.type = KEY_TYPE_DISCARD;
+
+				switch (overlap) {
+				case BCH_EXTENT_OVERLAP_FRONT:
+					bch2_cut_front(bkey_start_pos(k.k), &discard);
+					break;
+				case BCH_EXTENT_OVERLAP_BACK:
+					bch2_cut_back(k.k->p, &discard.k);
+					break;
+				default:
+					break;
+				}
+
+				discard.k.needs_whiteout = true;
+
+				ret = extent_squash(s, insert, t, _k, k, overlap);
+				BUG_ON(ret != BTREE_INSERT_OK);
+
+				extent_bset_insert(c, iter, &discard);
+			} else {
+				ret = extent_squash(s, insert, t, _k, k, overlap);
+				BUG_ON(ret != BTREE_INSERT_OK);
+			}
 next:
-		bch2_cut_front(s->committed, insert);
-		bch2_btree_iter_set_pos_same_leaf(iter, s->committed);
+			bch2_cut_front(s->committed, insert);
+			bch2_btree_iter_set_pos_same_leaf(iter, s->committed);
+		}
+
+		if (ret != BTREE_INSERT_OK ||
+		    overlap == BCH_EXTENT_OVERLAP_FRONT ||
+		    overlap == BCH_EXTENT_OVERLAP_MIDDLE)
+			break;
 	}
 
-	return ret;
-}
+	if (ret == BTREE_INSERT_OK &&
+	    bkey_cmp(s->committed, insert->k.p) < 0)
+		ret = extent_insert_advance_pos(s, bkey_s_c_null);
 
-static enum btree_insert_ret
-__bch2_insert_fixup_extent(struct extent_insert_state *s)
-{
-	struct btree_iter *iter = s->insert->iter;
-	struct btree_iter_level *l = &iter->l[0];
-	struct btree *b = l->b;
-	struct btree_node_iter *node_iter = &l->iter;
-	struct bkey_packed *_k;
-	struct bkey unpacked;
-	struct bkey_i *insert = s->insert->k;
-	enum btree_insert_ret ret = BTREE_INSERT_OK;
+	/*
+	 * may have skipped past some deleted extents greater than the insert
+	 * key, before we got to a non deleted extent and knew we could bail out
+	 * rewind the iterator a bit if necessary:
+	 */
+	{
+		struct btree_node_iter node_iter = l->iter;
+		struct bkey uk;
 
-	while (bkey_cmp(s->committed, insert->k.p) < 0 &&
-	       (ret = extent_insert_should_stop(s)) == BTREE_INSERT_OK &&
-	       (_k = bch2_btree_node_iter_peek_all(node_iter, b))) {
-		struct bset_tree *t = bch2_bkey_to_bset(b, _k);
-		struct bkey_s k = __bkey_disassemble(b, _k, &unpacked);
-		enum bch_extent_overlap overlap;
-
-		EBUG_ON(bkey_cmp(iter->pos, bkey_start_pos(&insert->k)));
-		EBUG_ON(bkey_cmp(iter->pos, k.k->p) >= 0);
-
-		if (bkey_cmp(bkey_start_pos(k.k), insert->k.p) >= 0)
-			break;
-
-		overlap = bch2_extent_overlap(&insert->k, k.k);
-
-		if (!k.k->size)
-			goto squash;
-
-		/*
-		 * Only call advance pos & call hook for nonzero size extents:
-		 */
-		ret = extent_insert_advance_pos(s, k.s_c);
-		if (ret)
-			break;
-
-		if (k.k->size &&
-		    (k.k->needs_whiteout || bkey_written(b, _k)))
-			insert->k.needs_whiteout = true;
-
-		if (overlap == BCH_EXTENT_OVERLAP_ALL &&
-		    bkey_whiteout(k.k) &&
-		    k.k->needs_whiteout) {
-			unreserve_whiteout(b, _k);
-			_k->needs_whiteout = false;
-		}
-squash:
-		ret = extent_squash(s, insert, t, _k, k, overlap);
-		if (ret != BTREE_INSERT_OK)
-			break;
+		while ((_k = bch2_btree_node_iter_prev_all(&node_iter, l->b)) &&
+		       (uk = bkey_unpack_key(l->b, _k),
+			bkey_cmp(uk.p, s->committed) > 0))
+			l->iter = node_iter;
 	}
 
 	return ret;
@@ -1647,6 +1672,11 @@ bch2_insert_fixup_extent(struct btree_insert *trans,
 		.deleting	= bkey_whiteout(&insert->k->k),
 	};
 
+	if (s.deleting) {
+		s.whiteout = *insert->k;
+		s.whiteout.k.type = KEY_TYPE_DISCARD;
+	}
+
 	EBUG_ON(iter->level);
 	EBUG_ON(!insert->k->k.size);
 
@@ -1657,6 +1687,7 @@ bch2_insert_fixup_extent(struct btree_insert *trans,
 	 * @insert->k and the node iterator that we're advancing:
 	 */
 	EBUG_ON(bkey_cmp(iter->pos, bkey_start_pos(&insert->k->k)));
+	bch2_btree_iter_verify(iter, b);
 
 	if (!s.deleting &&
 	    !(trans->flags & BTREE_INSERT_JOURNAL_REPLAY))
@@ -1664,13 +1695,7 @@ bch2_insert_fixup_extent(struct btree_insert *trans,
 				bkey_start_offset(&insert->k->k),
 				insert->k->k.size);
 
-	ret = !s.deleting
-		? __bch2_insert_fixup_extent(&s)
-		: __bch2_delete_fixup_extent(&s);
-
-	if (ret == BTREE_INSERT_OK &&
-	    bkey_cmp(s.committed, insert->k->k.p) < 0)
-		ret = extent_insert_advance_pos(&s, bkey_s_c_null);
+	ret = __bch2_insert_fixup_extent(&s);
 
 	extent_insert_committed(&s);
 
@@ -2172,130 +2197,6 @@ enum merge_result bch2_extent_merge(struct bch_fs *c, struct btree *b,
 	return BCH_MERGE_MERGE;
 }
 
-static void extent_i_save(struct btree *b, struct bkey_packed *dst,
-			  struct bkey_i *src)
-{
-	struct bkey_format *f = &b->format;
-	struct bkey_i *dst_unpacked;
-
-	BUG_ON(bkeyp_val_u64s(f, dst) != bkey_val_u64s(&src->k));
-
-	/*
-	 * We don't want the bch2_verify_key_order() call in extent_save(),
-	 * because we may be out of order with deleted keys that are about to be
-	 * removed by extent_bset_insert()
-	 */
-
-	if ((dst_unpacked = packed_to_bkey(dst)))
-		bkey_copy(dst_unpacked, src);
-	else
-		BUG_ON(!bch2_bkey_pack(dst, src, f));
-}
-
-static bool extent_merge_one_overlapping(struct btree_iter *iter,
-					 struct bpos new_pos,
-					 struct bset_tree *t,
-					 struct bkey_packed *k, struct bkey uk,
-					 bool check, bool could_pack)
-{
-	struct btree_iter_level *l = &iter->l[0];
-
-	BUG_ON(!bkey_deleted(k));
-
-	if (check) {
-		return !bkey_packed(k) || could_pack;
-	} else {
-		uk.p = new_pos;
-		extent_save(l->b, &l->iter, k, &uk);
-		bch2_bset_fix_invalidated_key(l->b, t, k);
-		bch2_btree_node_iter_fix(iter, l->b, &l->iter, t,
-					 k, k->u64s, k->u64s);
-		return true;
-	}
-}
-
-static bool extent_merge_do_overlapping(struct btree_iter *iter,
-					struct bkey *m, bool back_merge)
-{
-	struct btree_iter_level *l = &iter->l[0];
-	struct btree *b = l->b;
-	struct btree_node_iter *node_iter = &l->iter;
-	struct bset_tree *t;
-	struct bkey_packed *k;
-	struct bkey uk;
-	struct bpos new_pos = back_merge ? m->p : bkey_start_pos(m);
-	bool could_pack = bkey_pack_pos((void *) &uk, new_pos, b);
-	bool check = true;
-
-	/*
-	 * @m is the new merged extent:
-	 *
-	 * The merge took place in the last bset; we know there can't be any 0
-	 * size extents overlapping with m there because if so they would have
-	 * been between the two extents we merged.
-	 *
-	 * But in the other bsets, we have to check for and fix such extents:
-	 */
-do_fixup:
-	for_each_bset(b, t) {
-		if (t == bset_tree_last(b))
-			break;
-
-		/*
-		 * if we don't find this bset in the iterator we already got to
-		 * the end of that bset, so start searching from the end.
-		 */
-		k = bch2_btree_node_iter_bset_pos(node_iter, b, t);
-
-		if (k == btree_bkey_last(b, t))
-			k = bch2_bkey_prev_all(b, t, k);
-		if (!k)
-			continue;
-
-		if (back_merge) {
-			/*
-			 * Back merge: 0 size extents will be before the key
-			 * that was just inserted (and thus the iterator
-			 * position) - walk backwards to find them
-			 */
-			for (;
-			     k &&
-			     (uk = bkey_unpack_key(b, k),
-			      bkey_cmp(uk.p, bkey_start_pos(m)) > 0);
-			     k = bch2_bkey_prev_all(b, t, k)) {
-				if (bkey_cmp(uk.p, m->p) >= 0)
-					continue;
-
-				if (!extent_merge_one_overlapping(iter, new_pos,
-						t, k, uk, check, could_pack))
-					return false;
-			}
-		} else {
-			/* Front merge - walk forwards */
-			for (;
-			     k != btree_bkey_last(b, t) &&
-			     (uk = bkey_unpack_key(b, k),
-			      bkey_cmp(uk.p, m->p) < 0);
-			     k = bkey_next(k)) {
-				if (bkey_cmp(uk.p,
-					     bkey_start_pos(m)) <= 0)
-					continue;
-
-				if (!extent_merge_one_overlapping(iter, new_pos,
-						t, k, uk, check, could_pack))
-					return false;
-			}
-		}
-	}
-
-	if (check) {
-		check = false;
-		goto do_fixup;
-	}
-
-	return true;
-}
-
 /*
  * When merging an extent that we're inserting into a btree node, the new merged
  * extent could overlap with an existing 0 size extent - if we don't fix that,
@@ -2312,13 +2213,13 @@ static bool bch2_extent_merge_inline(struct bch_fs *c,
 {
 	struct btree *b = iter->l[0].b;
 	struct btree_node_iter *node_iter = &iter->l[0].iter;
-	const struct bkey_format *f = &b->format;
-	struct bset_tree *t = bset_tree_last(b);
-	struct bkey_packed *m;
-	BKEY_PADDED(k) li;
-	BKEY_PADDED(k) ri;
-	struct bkey_i *mi;
-	struct bkey tmp;
+	BKEY_PADDED(k) li, ri;
+	struct bkey_packed *m	= back_merge ? l : r;
+	struct bkey_i *mi	= back_merge ? &li.k : &ri.k;
+	struct bset_tree *t	= bch2_bkey_to_bset(b, m);
+	enum merge_result ret;
+
+	EBUG_ON(bkey_written(b, m));
 
 	/*
 	 * We need to save copies of both l and r, because we might get a
@@ -2327,57 +2228,49 @@ static bool bch2_extent_merge_inline(struct bch_fs *c,
 	bch2_bkey_unpack(b, &li.k, l);
 	bch2_bkey_unpack(b, &ri.k, r);
 
-	m = back_merge ? l : r;
-	mi = back_merge ? &li.k : &ri.k;
-
-	/* l & r should be in last bset: */
-	EBUG_ON(bch2_bkey_to_bset(b, m) != t);
-
-	switch (bch2_extent_merge(c, b, &li.k, &ri.k)) {
-	case BCH_MERGE_NOMERGE:
+	ret = bch2_extent_merge(c, b, &li.k, &ri.k);
+	if (ret == BCH_MERGE_NOMERGE)
 		return false;
-	case BCH_MERGE_PARTIAL:
-		if (bkey_packed(m) && !bch2_bkey_pack_key((void *) &tmp, &mi->k, f))
+
+	/*
+	 * check if we overlap with deleted extents - would break the sort
+	 * order:
+	 */
+	if (back_merge) {
+		struct bkey_packed *n = bkey_next(m);
+
+		if (n != btree_bkey_last(b, t) &&
+		    bkey_cmp_left_packed(b, n, &li.k.k.p) <= 0 &&
+		    bkey_deleted(n))
 			return false;
+	} else if (ret == BCH_MERGE_MERGE) {
+		struct bkey_packed *prev = bch2_bkey_prev_all(b, t, m);
 
-		if (!extent_merge_do_overlapping(iter, &li.k.k, back_merge))
+		if (prev &&
+		    bkey_cmp_left_packed_byval(b, prev,
+				bkey_start_pos(&li.k.k)) > 0)
 			return false;
+	}
 
-		extent_i_save(b, m, mi);
-		bch2_bset_fix_invalidated_key(b, t, m);
-
-		/*
-		 * Update iterator to reflect what we just inserted - otherwise,
-		 * the iter_fix() call is going to put us _before_ the key we
-		 * just partially merged with:
-		 */
-		if (back_merge)
-			bch2_btree_iter_set_pos_same_leaf(iter, li.k.k.p);
-
-		bch2_btree_node_iter_fix(iter, b, node_iter,
-					 t, m, m->u64s, m->u64s);
+	if (ret == BCH_MERGE_PARTIAL) {
+		if (!extent_i_save(b, m, mi))
+			return false;
 
 		if (!back_merge)
 			bkey_copy(packed_to_bkey(l), &li.k);
 		else
 			bkey_copy(packed_to_bkey(r), &ri.k);
-		return false;
-	case BCH_MERGE_MERGE:
-		if (bkey_packed(m) && !bch2_bkey_pack_key((void *) &tmp, &li.k.k, f))
+	} else {
+		if (!extent_i_save(b, m, &li.k))
 			return false;
-
-		if (!extent_merge_do_overlapping(iter, &li.k.k, back_merge))
-			return false;
-
-		extent_i_save(b, m, &li.k);
-		bch2_bset_fix_invalidated_key(b, t, m);
-
-		bch2_btree_node_iter_fix(iter, b, node_iter,
-					 t, m, m->u64s, m->u64s);
-		return true;
-	default:
-		BUG();
 	}
+
+	bch2_bset_fix_invalidated_key(b, t, m);
+	bch2_btree_node_iter_fix(iter, b, node_iter,
+				 t, m, m->u64s, m->u64s);
+	verify_modified_extent(iter, m);
+
+	return ret == BCH_MERGE_MERGE;
 }
 
 int bch2_check_range_allocated(struct bch_fs *c, struct bpos pos, u64 size)