diff --git a/.bcachefs_revision b/.bcachefs_revision
index 9fff2db3..e42a96d6 100644
--- a/.bcachefs_revision
+++ b/.bcachefs_revision
@@ -1 +1 @@
-ffe09df1065dd1b326913b21381ed1ad35ab8ef9
+d868a87c678935c89df9bca63d708d616529b0d2
diff --git a/cmd_debug.c b/cmd_debug.c
index 72eccd80..5da97daa 100644
--- a/cmd_debug.c
+++ b/cmd_debug.c
@@ -59,10 +59,13 @@ static void dump_one_device(struct bch_fs *c, struct bch_dev *ca, int fd)
 	/* Btree: */
 	for (i = 0; i < BTREE_ID_NR; i++) {
 		const struct bch_extent_ptr *ptr;
-		struct btree_iter iter;
+		struct btree_trans trans;
+		struct btree_iter *iter;
 		struct btree *b;
 
-		for_each_btree_node(&iter, c, i, POS_MIN, 0, b) {
+		bch2_trans_init(&trans, c);
+
+		for_each_btree_node(&trans, iter, i, POS_MIN, 0, b) {
 			struct bkey_s_c_extent e = bkey_i_to_s_c_extent(&b->key);
 
 			extent_for_each_ptr(e, ptr)
@@ -71,7 +74,7 @@ static void dump_one_device(struct bch_fs *c, struct bch_dev *ca, int fd)
 						  ptr->offset << 9,
 						  b->written << 9);
 		}
-		bch2_btree_iter_unlock(&iter);
+		bch2_trans_exit(&trans);
 	}
 
 	qcow2_write_image(ca->disk_sb.bdev->bd_fd, fd, &data,
@@ -151,11 +154,14 @@ int cmd_dump(int argc, char *argv[])
 static void list_keys(struct bch_fs *c, enum btree_id btree_id,
 		      struct bpos start, struct bpos end)
 {
-	struct btree_iter iter;
+	struct btree_trans trans;
+	struct btree_iter *iter;
 	struct bkey_s_c k;
 	char buf[512];
 
-	for_each_btree_key(&iter, c, btree_id, start,
+	bch2_trans_init(&trans, c);
+
+	for_each_btree_key(&trans, iter, btree_id, start,
 			   BTREE_ITER_PREFETCH, k) {
 		if (bkey_cmp(k.k->p, end) > 0)
 			break;
@@ -163,37 +169,43 @@ static void list_keys(struct bch_fs *c, enum btree_id btree_id,
 		bch2_bkey_val_to_text(&PBUF(buf), c, k);
 		puts(buf);
 	}
-	bch2_btree_iter_unlock(&iter);
+	bch2_trans_exit(&trans);
 }
 
 static void list_btree_formats(struct bch_fs *c, enum btree_id btree_id,
 			       struct bpos start, struct bpos end)
 {
-	struct btree_iter iter;
+	struct btree_trans trans;
+	struct btree_iter *iter;
 	struct btree *b;
 	char buf[4096];
 
-	for_each_btree_node(&iter, c, btree_id, start, 0, b) {
+	bch2_trans_init(&trans, c);
+
+	for_each_btree_node(&trans, iter, btree_id, start, 0, b) {
 		if (bkey_cmp(b->key.k.p, end) > 0)
 			break;
 
 		bch2_btree_node_to_text(&PBUF(buf), c, b);
 		puts(buf);
 	}
-	bch2_btree_iter_unlock(&iter);
+	bch2_trans_exit(&trans);
 }
 
 static void list_nodes_keys(struct bch_fs *c, enum btree_id btree_id,
 			    struct bpos start, struct bpos end)
 {
-	struct btree_iter iter;
+	struct btree_trans trans;
+	struct btree_iter *iter;
 	struct btree_node_iter node_iter;
 	struct bkey unpacked;
 	struct bkey_s_c k;
 	struct btree *b;
 	char buf[4096];
 
-	for_each_btree_node(&iter, c, btree_id, start, 0, b) {
+	bch2_trans_init(&trans, c);
+
+	for_each_btree_node(&trans, iter, btree_id, start, 0, b) {
 		if (bkey_cmp(b->key.k.p, end) > 0)
 			break;
 
@@ -206,7 +218,7 @@ static void list_nodes_keys(struct bch_fs *c, enum btree_id btree_id,
 			puts(buf);
 		}
 	}
-	bch2_btree_iter_unlock(&iter);
+	bch2_trans_exit(&trans);
 }
 
 static struct bpos parse_pos(char *buf)
diff --git a/include/linux/bitops.h b/include/linux/bitops.h
index dc2927b3..f2183d54 100644
--- a/include/linux/bitops.h
+++ b/include/linux/bitops.h
@@ -120,6 +120,12 @@ static inline unsigned long hweight_long(unsigned long w)
 	return __builtin_popcountl(w);
 }
 
+static inline unsigned long hweight64(u64 w)
+{
+	return __builtin_popcount((u32) w) +
+	       __builtin_popcount(w >> 32);
+}
+
 static inline unsigned long hweight8(unsigned long w)
 {
 	return __builtin_popcountl(w);
diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 9dc0fef1..10d94c5e 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -217,4 +217,6 @@ struct qstr {
 
 #define QSTR_INIT(n,l) { { { .len = l } }, .name = n }
 
+#define POISON_FREE 0x6b
+
 #endif
diff --git a/include/linux/printk.h b/include/linux/printk.h
index 8f8dd6b9..bc1619f7 100644
--- a/include/linux/printk.h
+++ b/include/linux/printk.h
@@ -45,6 +45,7 @@ static inline int scnprintf(char * buf, size_t size, const char * fmt, ...)
 }
 
 #define printk(...)	printf(__VA_ARGS__)
+#define vprintk(...)	vprintf(__VA_ARGS__)
 
 #define no_printk(fmt, ...)				\
 ({							\
diff --git a/libbcachefs/alloc_background.c b/libbcachefs/alloc_background.c
index 1a40ac21..18afef2e 100644
--- a/libbcachefs/alloc_background.c
+++ b/libbcachefs/alloc_background.c
@@ -263,18 +263,21 @@ static void bch2_alloc_read_key(struct bch_fs *c, struct bkey_s_c k)
 int bch2_alloc_read(struct bch_fs *c, struct list_head *journal_replay_list)
 {
 	struct journal_replay *r;
-	struct btree_iter iter;
+	struct btree_trans trans;
+	struct btree_iter *iter;
 	struct bkey_s_c k;
 	struct bch_dev *ca;
 	unsigned i;
 	int ret;
 
-	for_each_btree_key(&iter, c, BTREE_ID_ALLOC, POS_MIN, 0, k) {
+	bch2_trans_init(&trans, c);
+
+	for_each_btree_key(&trans, iter, BTREE_ID_ALLOC, POS_MIN, 0, k) {
 		bch2_alloc_read_key(c, k);
-		bch2_btree_iter_cond_resched(&iter);
+		bch2_trans_cond_resched(&trans);
 	}
 
-	ret = bch2_btree_iter_unlock(&iter);
+	ret = bch2_trans_exit(&trans);
 	if (ret)
 		return ret;
 
@@ -390,8 +393,6 @@ static int __bch2_alloc_write_key(struct btree_trans *trans, struct bch_dev *ca,
 	__alloc_write_key(a, g, m);
 	percpu_up_read_preempt_enable(&c->mark_lock);
 
-	bch2_btree_iter_cond_resched(iter);
-
 	bch2_trans_update(trans, BTREE_INSERT_ENTRY(iter, &a->k_i));
 
 	ret = bch2_trans_commit(trans, NULL, journal_seq,
@@ -449,6 +450,7 @@ int bch2_alloc_write(struct bch_fs *c, bool nowait, bool *wrote)
 			if (ret)
 				break;
 
+			bch2_trans_cond_resched(&trans);
 			*wrote = true;
 		}
 		up_read(&ca->bucket_lock);
@@ -937,14 +939,12 @@ static int bch2_invalidate_one_bucket2(struct btree_trans *trans,
 	spin_unlock(&c->freelist_lock);
 	percpu_up_read_preempt_enable(&c->mark_lock);
 
-	bch2_btree_iter_cond_resched(iter);
-
 	BUG_ON(BKEY_ALLOC_VAL_U64s_MAX > 8);
 
 	bch2_btree_iter_set_pos(iter, POS(ca->dev_idx, b));
 retry:
 	k = bch2_btree_iter_peek_slot(iter);
-	ret = btree_iter_err(k);
+	ret = bkey_err(k);
 	if (ret)
 		return ret;
 
diff --git a/libbcachefs/bcachefs.h b/libbcachefs/bcachefs.h
index ac90d8aa..9ee06e58 100644
--- a/libbcachefs/bcachefs.h
+++ b/libbcachefs/bcachefs.h
@@ -254,6 +254,8 @@ do {									\
 	BCH_DEBUG_PARAM(expensive_debug_checks,				\
 		"Enables various runtime debugging checks that "	\
 		"significantly affect performance")			\
+	BCH_DEBUG_PARAM(debug_check_iterators,				\
+		"Enables extra verification for btree iterators")	\
 	BCH_DEBUG_PARAM(debug_check_bkeys,				\
 		"Run bkey_debugcheck (primarily checking GC/allocation "\
 		"information) when iterating over keys")		\
diff --git a/libbcachefs/bset.c b/libbcachefs/bset.c
index 7e572f5f..4d182518 100644
--- a/libbcachefs/bset.c
+++ b/libbcachefs/bset.c
@@ -1040,7 +1040,7 @@ struct bkey_packed *bch2_bkey_prev_filter(struct btree *b,
 		k = p;
 	}
 
-	if (IS_ENABLED(CONFIG_BCACHEFS_DEBUG)) {
+	if (btree_keys_expensive_checks(b)) {
 		BUG_ON(ret >= orig_k);
 
 		for (i = ret ? bkey_next(ret) : btree_bkey_first(b, t);
@@ -1661,10 +1661,11 @@ static inline void __bch2_btree_node_iter_advance(struct btree_node_iter *iter,
 void bch2_btree_node_iter_advance(struct btree_node_iter *iter,
 				  struct btree *b)
 {
-#ifdef CONFIG_BCACHEFS_DEBUG
-	bch2_btree_node_iter_verify(iter, b);
-	bch2_btree_node_iter_next_check(iter, b);
-#endif
+	if (btree_keys_expensive_checks(b)) {
+		bch2_btree_node_iter_verify(iter, b);
+		bch2_btree_node_iter_next_check(iter, b);
+	}
+
 	__bch2_btree_node_iter_advance(iter, b);
 }
 
@@ -1727,7 +1728,7 @@ found:
 	iter->data[0].k = __btree_node_key_to_offset(b, prev);
 	iter->data[0].end = end;
 out:
-	if (IS_ENABLED(CONFIG_BCACHEFS_DEBUG)) {
+	if (btree_keys_expensive_checks(b)) {
 		struct btree_node_iter iter2 = *iter;
 
 		if (prev)
diff --git a/libbcachefs/btree_cache.c b/libbcachefs/btree_cache.c
index f77dc20d..074ea6f1 100644
--- a/libbcachefs/btree_cache.c
+++ b/libbcachefs/btree_cache.c
@@ -812,7 +812,7 @@ struct btree *bch2_btree_node_get_sibling(struct bch_fs *c,
 		 * We might have got -EINTR because trylock failed, and we're
 		 * holding other locks that would cause us to deadlock:
 		 */
-		for_each_linked_btree_iter(iter, linked)
+		trans_for_each_iter(iter->trans, linked)
 			if (btree_iter_cmp(iter, linked) < 0)
 				__bch2_btree_iter_unlock(linked);
 
@@ -837,13 +837,13 @@ struct btree *bch2_btree_node_get_sibling(struct bch_fs *c,
 			}
 		}
 
-		bch2_btree_iter_relock(iter);
+		bch2_btree_trans_relock(iter->trans);
 	}
 out:
 	if (btree_lock_want(iter, level + 1) == BTREE_NODE_UNLOCKED)
 		btree_node_unlock(iter, level + 1);
 
-	bch2_btree_iter_verify_locks(iter);
+	bch2_btree_trans_verify_locks(iter->trans);
 
 	BUG_ON((!may_drop_locks || !IS_ERR(ret)) &&
 	       (iter->uptodate >= BTREE_ITER_NEED_RELOCK ||
diff --git a/libbcachefs/btree_gc.c b/libbcachefs/btree_gc.c
index af75878c..cb0e2449 100644
--- a/libbcachefs/btree_gc.c
+++ b/libbcachefs/btree_gc.c
@@ -204,13 +204,16 @@ static int btree_gc_mark_node(struct bch_fs *c, struct btree *b,
 static int bch2_gc_btree(struct bch_fs *c, enum btree_id btree_id,
 			 bool initial)
 {
-	struct btree_iter iter;
+	struct btree_trans trans;
+	struct btree_iter *iter;
 	struct btree *b;
 	struct range_checks r;
 	unsigned depth = btree_node_type_needs_gc(btree_id) ? 0 : 1;
 	u8 max_stale;
 	int ret = 0;
 
+	bch2_trans_init(&trans, c);
+
 	gc_pos_set(c, gc_pos_btree(btree_id, POS_MIN, 0));
 
 	/*
@@ -224,7 +227,7 @@ static int bch2_gc_btree(struct bch_fs *c, enum btree_id btree_id,
 
 	btree_node_range_checks_init(&r, depth);
 
-	__for_each_btree_node(&iter, c, btree_id, POS_MIN,
+	__for_each_btree_node(&trans, iter, btree_id, POS_MIN,
 			      0, depth, BTREE_ITER_PREFETCH, b) {
 		btree_node_range_checks(c, b, &r);
 
@@ -238,22 +241,22 @@ static int bch2_gc_btree(struct bch_fs *c, enum btree_id btree_id,
 
 		if (!initial) {
 			if (max_stale > 64)
-				bch2_btree_node_rewrite(c, &iter,
+				bch2_btree_node_rewrite(c, iter,
 						b->data->keys.seq,
 						BTREE_INSERT_USE_RESERVE|
 						BTREE_INSERT_NOWAIT|
 						BTREE_INSERT_GC_LOCK_HELD);
 			else if (!btree_gc_rewrite_disabled(c) &&
 				 (btree_gc_always_rewrite(c) || max_stale > 16))
-				bch2_btree_node_rewrite(c, &iter,
+				bch2_btree_node_rewrite(c, iter,
 						b->data->keys.seq,
 						BTREE_INSERT_NOWAIT|
 						BTREE_INSERT_GC_LOCK_HELD);
 		}
 
-		bch2_btree_iter_cond_resched(&iter);
+		bch2_trans_cond_resched(&trans);
 	}
-	ret = bch2_btree_iter_unlock(&iter) ?: ret;
+	ret = bch2_trans_exit(&trans) ?: ret;
 	if (ret)
 		return ret;
 
@@ -474,12 +477,8 @@ static void bch2_gc_free(struct bch_fs *c)
 		ca->usage[1] = NULL;
 	}
 
-	percpu_down_write(&c->mark_lock);
-
 	free_percpu(c->usage[1]);
 	c->usage[1] = NULL;
-
-	percpu_up_write(&c->mark_lock);
 }
 
 static void bch2_gc_done(struct bch_fs *c, bool initial)
@@ -520,8 +519,6 @@ static void bch2_gc_done(struct bch_fs *c, bool initial)
 #define copy_fs_field(_f, _msg, ...)					\
 	copy_field(_f, "fs has wrong " _msg, ##__VA_ARGS__)
 
-	percpu_down_write(&c->mark_lock);
-
 	{
 		struct genradix_iter dst_iter = genradix_iter_init(&c->stripes[0], 0);
 		struct genradix_iter src_iter = genradix_iter_init(&c->stripes[1], 0);
@@ -559,12 +556,6 @@ static void bch2_gc_done(struct bch_fs *c, bool initial)
 		struct bucket_array *src = __bucket_array(ca, 1);
 		size_t b;
 
-		if (initial) {
-			memcpy(dst, src,
-			       sizeof(struct bucket_array) +
-			       sizeof(struct bucket) * dst->nbuckets);
-		}
-
 		for (b = 0; b < src->nbuckets; b++) {
 			copy_bucket_field(gen);
 			copy_bucket_field(data_type);
@@ -629,8 +620,6 @@ static void bch2_gc_done(struct bch_fs *c, bool initial)
 		}
 	}
 
-	percpu_up_write(&c->mark_lock);
-
 #undef copy_fs_field
 #undef copy_dev_field
 #undef copy_bucket_field
@@ -643,8 +632,6 @@ static int bch2_gc_start(struct bch_fs *c)
 	struct bch_dev *ca;
 	unsigned i;
 
-	percpu_down_write(&c->mark_lock);
-
 	/*
 	 * indicate to stripe code that we need to allocate for the gc stripes
 	 * radix tree, too
@@ -655,8 +642,6 @@ static int bch2_gc_start(struct bch_fs *c)
 
 	c->usage[1] = __alloc_percpu_gfp(fs_usage_u64s(c) * sizeof(u64),
 					 sizeof(u64), GFP_KERNEL);
-	percpu_up_write(&c->mark_lock);
-
 	if (!c->usage[1])
 		return -ENOMEM;
 
@@ -679,8 +664,6 @@ static int bch2_gc_start(struct bch_fs *c)
 		}
 	}
 
-	percpu_down_write(&c->mark_lock);
-
 	for_each_member_device(ca, c, i) {
 		struct bucket_array *dst = __bucket_array(ca, 1);
 		struct bucket_array *src = __bucket_array(ca, 0);
@@ -697,8 +680,6 @@ static int bch2_gc_start(struct bch_fs *c)
 		}
 	};
 
-	percpu_up_write(&c->mark_lock);
-
 	return bch2_ec_mem_alloc(c, true);
 }
 
@@ -731,7 +712,10 @@ int bch2_gc(struct bch_fs *c, struct list_head *journal, bool initial)
 
 	down_write(&c->gc_lock);
 again:
+	percpu_down_write(&c->mark_lock);
 	ret = bch2_gc_start(c);
+	percpu_up_write(&c->mark_lock);
+
 	if (ret)
 		goto out;
 
@@ -756,7 +740,11 @@ out:
 			bch_info(c, "Fixed gens, restarting mark and sweep:");
 			clear_bit(BCH_FS_FIXED_GENS, &c->flags);
 			__gc_pos_set(c, gc_phase(GC_PHASE_NOT_RUNNING));
+
+			percpu_down_write(&c->mark_lock);
 			bch2_gc_free(c);
+			percpu_up_write(&c->mark_lock);
+
 			goto again;
 		}
 
@@ -764,6 +752,8 @@ out:
 		ret = -EINVAL;
 	}
 
+	percpu_down_write(&c->mark_lock);
+
 	if (!ret)
 		bch2_gc_done(c, initial);
 
@@ -771,6 +761,8 @@ out:
 	__gc_pos_set(c, gc_phase(GC_PHASE_NOT_RUNNING));
 
 	bch2_gc_free(c);
+	percpu_up_write(&c->mark_lock);
+
 	up_write(&c->gc_lock);
 
 	trace_gc_end(c);
@@ -1027,7 +1019,8 @@ next:
 
 static int bch2_coalesce_btree(struct bch_fs *c, enum btree_id btree_id)
 {
-	struct btree_iter iter;
+	struct btree_trans trans;
+	struct btree_iter *iter;
 	struct btree *b;
 	bool kthread = (current->flags & PF_KTHREAD) != 0;
 	unsigned i;
@@ -1036,6 +1029,8 @@ static int bch2_coalesce_btree(struct bch_fs *c, enum btree_id btree_id)
 	struct btree *merge[GC_MERGE_NODES];
 	u32 lock_seq[GC_MERGE_NODES];
 
+	bch2_trans_init(&trans, c);
+
 	/*
 	 * XXX: We don't have a good way of positively matching on sibling nodes
 	 * that have the same parent - this code works by handling the cases
@@ -1045,7 +1040,7 @@ static int bch2_coalesce_btree(struct bch_fs *c, enum btree_id btree_id)
 	 */
 	memset(merge, 0, sizeof(merge));
 
-	__for_each_btree_node(&iter, c, btree_id, POS_MIN,
+	__for_each_btree_node(&trans, iter, btree_id, POS_MIN,
 			      BTREE_MAX_DEPTH, 0,
 			      BTREE_ITER_PREFETCH, b) {
 		memmove(merge + 1, merge,
@@ -1067,7 +1062,7 @@ static int bch2_coalesce_btree(struct bch_fs *c, enum btree_id btree_id)
 		}
 		memset(merge + i, 0, (GC_MERGE_NODES - i) * sizeof(merge[0]));
 
-		bch2_coalesce_nodes(c, &iter, merge);
+		bch2_coalesce_nodes(c, iter, merge);
 
 		for (i = 1; i < GC_MERGE_NODES && merge[i]; i++) {
 			lock_seq[i] = merge[i]->lock.state.seq;
@@ -1077,23 +1072,23 @@ static int bch2_coalesce_btree(struct bch_fs *c, enum btree_id btree_id)
 		lock_seq[0] = merge[0]->lock.state.seq;
 
 		if (kthread && kthread_should_stop()) {
-			bch2_btree_iter_unlock(&iter);
+			bch2_trans_exit(&trans);
 			return -ESHUTDOWN;
 		}
 
-		bch2_btree_iter_cond_resched(&iter);
+		bch2_trans_cond_resched(&trans);
 
 		/*
 		 * If the parent node wasn't relocked, it might have been split
 		 * and the nodes in our sliding window might not have the same
 		 * parent anymore - blow away the sliding window:
 		 */
-		if (btree_iter_node(&iter, iter.level + 1) &&
-		    !btree_node_intent_locked(&iter, iter.level + 1))
+		if (btree_iter_node(iter, iter->level + 1) &&
+		    !btree_node_intent_locked(iter, iter->level + 1))
 			memset(merge + 1, 0,
 			       (GC_MERGE_NODES - 1) * sizeof(merge[0]));
 	}
-	return bch2_btree_iter_unlock(&iter);
+	return bch2_trans_exit(&trans);
 }
 
 /**
diff --git a/libbcachefs/btree_io.c b/libbcachefs/btree_io.c
index f2107cf7..0b99e7d2 100644
--- a/libbcachefs/btree_io.c
+++ b/libbcachefs/btree_io.c
@@ -1153,19 +1153,21 @@ static void bch2_btree_node_write_error(struct bch_fs *c,
 	struct bkey_i_btree_ptr *new_key;
 	struct bkey_s_btree_ptr bp;
 	struct bch_extent_ptr *ptr;
-	struct btree_iter iter;
+	struct btree_trans trans;
+	struct btree_iter *iter;
 	int ret;
 
-	__bch2_btree_iter_init(&iter, c, b->btree_id, b->key.k.p,
-			       BTREE_MAX_DEPTH,
-			       b->level, BTREE_ITER_NODES);
+	bch2_trans_init(&trans, c);
+
+	iter = bch2_trans_get_node_iter(&trans, b->btree_id, b->key.k.p,
+					BTREE_MAX_DEPTH, b->level, 0);
 retry:
-	ret = bch2_btree_iter_traverse(&iter);
+	ret = bch2_btree_iter_traverse(iter);
 	if (ret)
 		goto err;
 
 	/* has node been freed? */
-	if (iter.l[b->level].b != b) {
+	if (iter->l[b->level].b != b) {
 		/* node has been freed: */
 		BUG_ON(!btree_node_dying(b));
 		goto out;
@@ -1184,13 +1186,13 @@ retry:
 	if (!bch2_bkey_nr_ptrs(bp.s_c))
 		goto err;
 
-	ret = bch2_btree_node_update_key(c, &iter, b, new_key);
+	ret = bch2_btree_node_update_key(c, iter, b, new_key);
 	if (ret == -EINTR)
 		goto retry;
 	if (ret)
 		goto err;
 out:
-	bch2_btree_iter_unlock(&iter);
+	bch2_trans_exit(&trans);
 	bio_put(&wbio->wbio.bio);
 	btree_node_write_done(c, b);
 	return;
diff --git a/libbcachefs/btree_iter.c b/libbcachefs/btree_iter.c
index 94b86ad6..49ad6df8 100644
--- a/libbcachefs/btree_iter.c
+++ b/libbcachefs/btree_iter.c
@@ -69,7 +69,7 @@ void bch2_btree_node_unlock_write(struct btree *b, struct btree_iter *iter)
 	EBUG_ON(iter->l[b->level].b != b);
 	EBUG_ON(iter->l[b->level].lock_seq + 1 != b->lock.state.seq);
 
-	for_each_btree_iter_with_node(iter, b, linked)
+	trans_for_each_iter_with_node(iter->trans, b, linked)
 		linked->l[b->level].lock_seq += 2;
 
 	six_unlock_write(&b->lock);
@@ -77,13 +77,12 @@ void bch2_btree_node_unlock_write(struct btree *b, struct btree_iter *iter)
 
 void __bch2_btree_node_lock_write(struct btree *b, struct btree_iter *iter)
 {
-	struct bch_fs *c = iter->c;
 	struct btree_iter *linked;
 	unsigned readers = 0;
 
 	EBUG_ON(btree_node_read_locked(iter, b->level));
 
-	for_each_linked_btree_iter(iter, linked)
+	trans_for_each_iter(iter->trans, linked)
 		if (linked->l[b->level].b == b &&
 		    btree_node_read_locked(linked, b->level))
 			readers++;
@@ -96,7 +95,7 @@ void __bch2_btree_node_lock_write(struct btree *b, struct btree_iter *iter)
 	 */
 	atomic64_sub(__SIX_VAL(read_lock, readers),
 		     &b->lock.state.counter);
-	btree_node_lock_type(c, b, SIX_LOCK_write);
+	btree_node_lock_type(iter->trans->c, b, SIX_LOCK_write);
 	atomic64_add(__SIX_VAL(read_lock, readers),
 		     &b->lock.state.counter);
 }
@@ -187,7 +186,8 @@ static inline bool btree_iter_get_locks(struct btree_iter *iter,
 	if (iter->uptodate == BTREE_ITER_NEED_RELOCK)
 		iter->uptodate = BTREE_ITER_NEED_PEEK;
 
-	bch2_btree_iter_verify_locks(iter);
+	bch2_btree_trans_verify_locks(iter->trans);
+
 	return iter->uptodate < BTREE_ITER_NEED_RELOCK;
 }
 
@@ -198,12 +198,11 @@ bool __bch2_btree_node_lock(struct btree *b, struct bpos pos,
 			   enum six_lock_type type,
 			   bool may_drop_locks)
 {
-	struct bch_fs *c = iter->c;
 	struct btree_iter *linked;
 	bool ret = true;
 
 	/* Check if it's safe to block: */
-	for_each_btree_iter(iter, linked) {
+	trans_for_each_iter(iter->trans, linked) {
 		if (!linked->nodes_locked)
 			continue;
 
@@ -253,7 +252,7 @@ bool __bch2_btree_node_lock(struct btree *b, struct bpos pos,
 	}
 
 	if (ret)
-		__btree_node_lock_type(c, b, type);
+		__btree_node_lock_type(iter->trans->c, b, type);
 	else
 		trans_restart();
 
@@ -263,7 +262,7 @@ bool __bch2_btree_node_lock(struct btree *b, struct bpos pos,
 /* Btree iterator locking: */
 
 #ifdef CONFIG_BCACHEFS_DEBUG
-void __bch2_btree_iter_verify_locks(struct btree_iter *iter)
+void bch2_btree_iter_verify_locks(struct btree_iter *iter)
 {
 	unsigned l;
 
@@ -280,35 +279,23 @@ void __bch2_btree_iter_verify_locks(struct btree_iter *iter)
 	}
 }
 
-void bch2_btree_iter_verify_locks(struct btree_iter *iter)
+void bch2_btree_trans_verify_locks(struct btree_trans *trans)
 {
-	struct btree_iter *linked;
-
-	for_each_btree_iter(iter, linked)
-		__bch2_btree_iter_verify_locks(linked);
+	struct btree_iter *iter;
 
+	trans_for_each_iter(trans, iter)
+		bch2_btree_iter_verify_locks(iter);
 }
 #endif
 
 __flatten
-static bool __bch2_btree_iter_relock(struct btree_iter *iter)
+static bool bch2_btree_iter_relock(struct btree_iter *iter)
 {
 	return iter->uptodate >= BTREE_ITER_NEED_RELOCK
 		? btree_iter_get_locks(iter, false)
 		: true;
 }
 
-bool bch2_btree_iter_relock(struct btree_iter *iter)
-{
-	struct btree_iter *linked;
-	bool ret = true;
-
-	for_each_btree_iter(iter, linked)
-		ret &= __bch2_btree_iter_relock(linked);
-
-	return ret;
-}
-
 bool __bch2_btree_iter_upgrade(struct btree_iter *iter,
 			       unsigned new_locks_want)
 {
@@ -326,8 +313,9 @@ bool __bch2_btree_iter_upgrade(struct btree_iter *iter,
 	 * on iterators that might lock ancestors before us to avoid getting
 	 * -EINTR later:
 	 */
-	for_each_linked_btree_iter(iter, linked)
-		if (linked->btree_id == iter->btree_id &&
+	trans_for_each_iter(iter->trans, linked)
+		if (linked != iter &&
+		    linked->btree_id == iter->btree_id &&
 		    btree_iter_cmp(linked, iter) <= 0 &&
 		    linked->locks_want < new_locks_want) {
 			linked->locks_want = new_locks_want;
@@ -372,7 +360,7 @@ void __bch2_btree_iter_downgrade(struct btree_iter *iter,
 	 * might have had to modify locks_want on linked iterators due to lock
 	 * ordering:
 	 */
-	for_each_btree_iter(iter, linked) {
+	trans_for_each_iter(iter->trans, linked) {
 		unsigned new_locks_want = downgrade_to ?:
 			(linked->flags & BTREE_ITER_INTENT ? 1 : 0);
 
@@ -395,19 +383,40 @@ void __bch2_btree_iter_downgrade(struct btree_iter *iter,
 		}
 	}
 
-	bch2_btree_iter_verify_locks(iter);
+	bch2_btree_trans_verify_locks(iter->trans);
 }
 
 int bch2_btree_iter_unlock(struct btree_iter *iter)
 {
 	struct btree_iter *linked;
 
-	for_each_btree_iter(iter, linked)
+	trans_for_each_iter(iter->trans, linked)
 		__bch2_btree_iter_unlock(linked);
 
-	return iter->flags & BTREE_ITER_ERROR ? -EIO : 0;
+	return btree_iter_err(iter);
 }
 
+bool bch2_btree_trans_relock(struct btree_trans *trans)
+{
+	struct btree_iter *iter;
+	bool ret = true;
+
+	trans_for_each_iter(trans, iter)
+		ret &= bch2_btree_iter_relock(iter);
+
+	return ret;
+}
+
+void bch2_btree_trans_unlock(struct btree_trans *trans)
+{
+	struct btree_iter *iter;
+
+	trans_for_each_iter(trans, iter)
+		__bch2_btree_iter_unlock(iter);
+}
+
+/* Btree transaction locking: */
+
 /* Btree iterator: */
 
 #ifdef CONFIG_BCACHEFS_DEBUG
@@ -419,6 +428,9 @@ static void __bch2_btree_iter_verify(struct btree_iter *iter,
 	struct btree_node_iter tmp = l->iter;
 	struct bkey_packed *k;
 
+	if (!debug_check_iterators(iter->trans->c))
+		return;
+
 	if (iter->uptodate > BTREE_ITER_NEED_PEEK)
 		return;
 
@@ -465,7 +477,10 @@ void bch2_btree_iter_verify(struct btree_iter *iter, struct btree *b)
 {
 	struct btree_iter *linked;
 
-	for_each_btree_iter_with_node(iter, b, linked)
+	if (!debug_check_iterators(iter->trans->c))
+		return;
+
+	trans_for_each_iter_with_node(iter->trans, b, linked)
 		__bch2_btree_iter_verify(linked, b);
 }
 
@@ -619,7 +634,7 @@ void bch2_btree_node_iter_fix(struct btree_iter *iter,
 		__bch2_btree_node_iter_fix(iter, b, node_iter, t,
 					  where, clobber_u64s, new_u64s);
 
-	for_each_btree_iter_with_node(iter, b, linked)
+	trans_for_each_iter_with_node(iter->trans, b, linked)
 		__bch2_btree_node_iter_fix(linked, b,
 					  &linked->l[b->level].iter, t,
 					  where, clobber_u64s, new_u64s);
@@ -643,8 +658,8 @@ static inline struct bkey_s_c __btree_iter_unpack(struct btree_iter *iter,
 
 	ret = bkey_disassemble(l->b, k, u);
 
-	if (debug_check_bkeys(iter->c))
-		bch2_bkey_debugcheck(iter->c, l->b, ret);
+	if (debug_check_bkeys(iter->trans->c))
+		bch2_bkey_debugcheck(iter->trans->c, l->b, ret);
 
 	return ret;
 }
@@ -777,7 +792,7 @@ void bch2_btree_iter_node_replace(struct btree_iter *iter, struct btree *b)
 	enum btree_node_locked_type t;
 	struct btree_iter *linked;
 
-	for_each_btree_iter(iter, linked)
+	trans_for_each_iter(iter->trans, linked)
 		if (btree_iter_pos_in_node(linked, b)) {
 			/*
 			 * bch2_btree_iter_node_drop() has already been called -
@@ -811,7 +826,7 @@ void bch2_btree_iter_node_drop(struct btree_iter *iter, struct btree *b)
 	iter->l[level].b = BTREE_ITER_NOT_END;
 	mark_btree_node_unlocked(iter, level);
 
-	for_each_btree_iter(iter, linked)
+	trans_for_each_iter(iter->trans, linked)
 		if (linked->l[level].b == b) {
 			__btree_node_unlock(linked, level);
 			linked->l[level].b = BTREE_ITER_NOT_END;
@@ -826,14 +841,14 @@ void bch2_btree_iter_reinit_node(struct btree_iter *iter, struct btree *b)
 {
 	struct btree_iter *linked;
 
-	for_each_btree_iter_with_node(iter, b, linked)
+	trans_for_each_iter_with_node(iter->trans, b, linked)
 		__btree_iter_init(linked, b->level);
 }
 
 static inline int btree_iter_lock_root(struct btree_iter *iter,
 				       unsigned depth_want)
 {
-	struct bch_fs *c = iter->c;
+	struct bch_fs *c = iter->trans->c;
 	struct btree *b;
 	enum six_lock_type lock_type;
 	unsigned i;
@@ -881,11 +896,12 @@ static inline int btree_iter_lock_root(struct btree_iter *iter,
 noinline
 static void btree_iter_prefetch(struct btree_iter *iter)
 {
+	struct bch_fs *c = iter->trans->c;
 	struct btree_iter_level *l = &iter->l[iter->level];
 	struct btree_node_iter node_iter = l->iter;
 	struct bkey_packed *k;
 	BKEY_PADDED(k) tmp;
-	unsigned nr = test_bit(BCH_FS_STARTED, &iter->c->flags)
+	unsigned nr = test_bit(BCH_FS_STARTED, &c->flags)
 		? (iter->level > 1 ? 0 :  2)
 		: (iter->level > 1 ? 1 : 16);
 	bool was_locked = btree_node_locked(iter, iter->level);
@@ -900,8 +916,7 @@ static void btree_iter_prefetch(struct btree_iter *iter)
 			break;
 
 		bch2_bkey_unpack(l->b, &tmp.k, k);
-		bch2_btree_node_prefetch(iter->c, iter, &tmp.k,
-					 iter->level - 1);
+		bch2_btree_node_prefetch(c, iter, &tmp.k, iter->level - 1);
 	}
 
 	if (!was_locked)
@@ -910,6 +925,7 @@ static void btree_iter_prefetch(struct btree_iter *iter)
 
 static inline int btree_iter_down(struct btree_iter *iter)
 {
+	struct bch_fs *c = iter->trans->c;
 	struct btree_iter_level *l = &iter->l[iter->level];
 	struct btree *b;
 	unsigned level = iter->level - 1;
@@ -921,7 +937,7 @@ static inline int btree_iter_down(struct btree_iter *iter)
 	bch2_bkey_unpack(l->b, &tmp.k,
 			 bch2_btree_node_iter_peek(&l->iter, l->b));
 
-	b = bch2_btree_node_get(iter->c, iter, &tmp.k, level, lock_type, true);
+	b = bch2_btree_node_get(c, iter, &tmp.k, level, lock_type, true);
 	if (unlikely(IS_ERR(b)))
 		return PTR_ERR(b);
 
@@ -943,17 +959,26 @@ static void btree_iter_up(struct btree_iter *iter)
 
 int __must_check __bch2_btree_iter_traverse(struct btree_iter *);
 
-static int btree_iter_traverse_error(struct btree_iter *iter, int ret)
+static int __btree_iter_traverse_all(struct btree_trans *trans,
+				     struct btree_iter *iter, int ret)
 {
-	struct bch_fs *c = iter->c;
-	struct btree_iter *linked, *sorted_iters, **i;
+	struct bch_fs *c = trans->c;
+	u8 sorted[BTREE_ITER_MAX];
+	unsigned i, nr_sorted = 0;
+
+	trans_for_each_iter(trans, iter)
+		sorted[nr_sorted++] = iter - trans->iters;
+
+#define btree_iter_cmp_by_idx(_l, _r)				\
+		btree_iter_cmp(&trans->iters[_l], &trans->iters[_r])
+
+	bubble_sort(sorted, nr_sorted, btree_iter_cmp_by_idx);
+#undef btree_iter_cmp_by_idx
+
 retry_all:
-	bch2_btree_iter_unlock(iter);
+	bch2_btree_trans_unlock(trans);
 
-	if (ret != -ENOMEM && ret != -EINTR)
-		goto io_error;
-
-	if (ret == -ENOMEM) {
+	if (unlikely(ret == -ENOMEM)) {
 		struct closure cl;
 
 		closure_init_stack(&cl);
@@ -964,57 +989,35 @@ retry_all:
 		} while (ret);
 	}
 
-	/*
-	 * Linked iters are normally a circular singly linked list - break cycle
-	 * while we sort them:
-	 */
-	linked = iter->next;
-	iter->next = NULL;
-	sorted_iters = NULL;
-
-	while (linked) {
-		iter = linked;
-		linked = linked->next;
-
-		i = &sorted_iters;
-		while (*i && btree_iter_cmp(iter, *i) > 0)
-			i = &(*i)->next;
-
-		iter->next = *i;
-		*i = iter;
+	if (unlikely(ret == -EIO)) {
+		iter->flags |= BTREE_ITER_ERROR;
+		iter->l[iter->level].b = BTREE_ITER_NOT_END;
+		goto out;
 	}
 
-	/* Make list circular again: */
-	iter = sorted_iters;
-	while (iter->next)
-		iter = iter->next;
-	iter->next = sorted_iters;
+	BUG_ON(ret && ret != -EINTR);
 
 	/* Now, redo traversals in correct order: */
+	for (i = 0; i < nr_sorted; i++) {
+		iter = &trans->iters[sorted[i]];
 
-	iter = sorted_iters;
-	do {
-retry:
-		ret = __bch2_btree_iter_traverse(iter);
-		if (unlikely(ret)) {
-			if (ret == -EINTR)
-				goto retry;
+		do {
+			ret = __bch2_btree_iter_traverse(iter);
+		} while (ret == -EINTR);
+
+		if (ret)
 			goto retry_all;
-		}
+	}
 
-		iter = iter->next;
-	} while (iter != sorted_iters);
-
-	ret = btree_iter_linked(iter) ? -EINTR : 0;
+	ret = btree_trans_has_multiple_iters(trans) ? -EINTR : 0;
 out:
 	bch2_btree_cache_cannibalize_unlock(c);
 	return ret;
-io_error:
-	BUG_ON(ret != -EIO);
+}
 
-	iter->flags |= BTREE_ITER_ERROR;
-	iter->l[iter->level].b = BTREE_ITER_NOT_END;
-	goto out;
+int bch2_btree_iter_traverse_all(struct btree_trans *trans)
+{
+	return __btree_iter_traverse_all(trans, NULL, 0);
 }
 
 static unsigned btree_iter_up_until_locked(struct btree_iter *iter,
@@ -1051,7 +1054,7 @@ int __must_check __bch2_btree_iter_traverse(struct btree_iter *iter)
 	if (unlikely(iter->level >= BTREE_MAX_DEPTH))
 		return 0;
 
-	if (__bch2_btree_iter_relock(iter))
+	if (bch2_btree_iter_relock(iter))
 		return 0;
 
 	/*
@@ -1091,7 +1094,7 @@ 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_trans_verify_locks(iter->trans);
 	__bch2_btree_iter_verify(iter, iter->l[iter->level].b);
 	return 0;
 }
@@ -1102,9 +1105,9 @@ int __must_check bch2_btree_iter_traverse(struct btree_iter *iter)
 
 	ret = __bch2_btree_iter_traverse(iter);
 	if (unlikely(ret))
-		ret = btree_iter_traverse_error(iter, ret);
+		ret = __btree_iter_traverse_all(iter->trans, iter, ret);
 
-	BUG_ON(ret == -EINTR && !btree_iter_linked(iter));
+	BUG_ON(ret == -EINTR && !btree_trans_has_multiple_iters(iter->trans));
 
 	return ret;
 }
@@ -1117,7 +1120,7 @@ static inline void bch2_btree_iter_checks(struct btree_iter *iter,
 		(iter->btree_id == BTREE_ID_EXTENTS &&
 		 type != BTREE_ITER_NODES));
 
-	bch2_btree_iter_verify_locks(iter);
+	bch2_btree_trans_verify_locks(iter->trans);
 }
 
 /* Iterate across nodes (leaf and interior nodes) */
@@ -1274,9 +1277,9 @@ static inline struct bkey_s_c btree_iter_peek_uptodate(struct btree_iter *iter)
 			__bch2_btree_node_iter_peek_all(&l->iter, l->b));
 	}
 
-	if (debug_check_bkeys(iter->c) &&
+	if (debug_check_bkeys(iter->trans->c) &&
 	    !bkey_deleted(ret.k))
-		bch2_bkey_debugcheck(iter->c, l->b, ret);
+		bch2_bkey_debugcheck(iter->trans->c, l->b, ret);
 	return ret;
 }
 
@@ -1581,124 +1584,79 @@ struct bkey_s_c bch2_btree_iter_next_slot(struct btree_iter *iter)
 	return __bch2_btree_iter_peek_slot(iter);
 }
 
-void __bch2_btree_iter_init(struct btree_iter *iter, struct bch_fs *c,
-			    enum btree_id btree_id, struct bpos pos,
-			    unsigned locks_want, unsigned depth,
-			    unsigned flags)
+static inline void bch2_btree_iter_init(struct btree_trans *trans,
+			struct btree_iter *iter, enum btree_id btree_id,
+			struct bpos pos, unsigned flags)
 {
+	struct bch_fs *c = trans->c;
 	unsigned i;
 
-	EBUG_ON(depth >= BTREE_MAX_DEPTH);
-	EBUG_ON(locks_want > BTREE_MAX_DEPTH);
+	if (btree_id == BTREE_ID_EXTENTS &&
+	    !(flags & BTREE_ITER_NODES))
+		flags |= BTREE_ITER_IS_EXTENTS;
 
-	iter->c				= c;
+	iter->trans			= trans;
 	iter->pos			= pos;
 	bkey_init(&iter->k);
 	iter->k.p			= pos;
 	iter->flags			= flags;
 	iter->uptodate			= BTREE_ITER_NEED_TRAVERSE;
 	iter->btree_id			= btree_id;
-	iter->level			= depth;
-	iter->locks_want		= locks_want;
+	iter->level			= 0;
+	iter->locks_want		= flags & BTREE_ITER_INTENT ? 1 : 0;
 	iter->nodes_locked		= 0;
 	iter->nodes_intent_locked	= 0;
 	for (i = 0; i < ARRAY_SIZE(iter->l); i++)
 		iter->l[i].b		= NULL;
 	iter->l[iter->level].b		= BTREE_ITER_NOT_END;
-	iter->next			= iter;
 
 	prefetch(c->btree_roots[btree_id].b);
 }
 
-static void bch2_btree_iter_unlink(struct btree_iter *iter)
-{
-	struct btree_iter *linked;
-
-	__bch2_btree_iter_unlock(iter);
-
-	if (!btree_iter_linked(iter))
-		return;
-
-	for_each_linked_btree_iter(iter, linked)
-		if (linked->next == iter) {
-			linked->next = iter->next;
-			iter->next = iter;
-			return;
-		}
-
-	BUG();
-}
-
-static void bch2_btree_iter_link(struct btree_iter *iter, struct btree_iter *new)
-{
-	BUG_ON(btree_iter_linked(new));
-
-	new->next = iter->next;
-	iter->next = new;
-}
-
-void bch2_btree_iter_copy(struct btree_iter *dst, struct btree_iter *src)
-{
-	unsigned i;
-
-	__bch2_btree_iter_unlock(dst);
-	memcpy(dst, src, offsetof(struct btree_iter, next));
-
-	for (i = 0; i < BTREE_MAX_DEPTH; i++)
-		if (btree_node_locked(dst, i))
-			six_lock_increment(&dst->l[i].b->lock,
-					   __btree_lock_want(dst, i));
-}
-
 /* new transactional stuff: */
 
-static void btree_trans_verify(struct btree_trans *trans)
+int bch2_trans_iter_put(struct btree_trans *trans,
+			struct btree_iter *iter)
 {
-	unsigned i;
+	int ret = btree_iter_err(iter);
 
-	for (i = 0; i < trans->nr_iters; i++) {
-		struct btree_iter *iter = &trans->iters[i];
-
-		BUG_ON(btree_iter_linked(iter) !=
-		       ((trans->iters_linked & (1 << i)) &&
-			!is_power_of_2(trans->iters_linked)));
-	}
+	trans->iters_live	&= ~(1ULL << iter->idx);
+	return ret;
 }
 
-static inline unsigned btree_trans_iter_idx(struct btree_trans *trans,
-					    struct btree_iter *iter)
+static inline void __bch2_trans_iter_free(struct btree_trans *trans,
+					  unsigned idx)
 {
-	ssize_t idx = iter - trans->iters;
-
-	BUG_ON(idx < 0 || idx >= trans->nr_iters);
-	BUG_ON(!(trans->iters_live & (1ULL << idx)));
-
-	return idx;
+	__bch2_btree_iter_unlock(&trans->iters[idx]);
+	trans->iters_linked		&= ~(1ULL << idx);
+	trans->iters_live		&= ~(1ULL << idx);
+	trans->iters_touched		&= ~(1ULL << idx);
+	trans->iters_unlink_on_restart	&= ~(1ULL << idx);
+	trans->iters_unlink_on_commit	&= ~(1ULL << idx);
 }
 
-void bch2_trans_iter_put(struct btree_trans *trans,
+int bch2_trans_iter_free(struct btree_trans *trans,
 			 struct btree_iter *iter)
 {
-	ssize_t idx = btree_trans_iter_idx(trans, iter);
+	int ret = btree_iter_err(iter);
 
-	trans->iters_live	&= ~(1ULL << idx);
+	__bch2_trans_iter_free(trans, iter->idx);
+	return ret;
 }
 
-void bch2_trans_iter_free(struct btree_trans *trans,
-			  struct btree_iter *iter)
+int bch2_trans_iter_free_on_commit(struct btree_trans *trans,
+				   struct btree_iter *iter)
 {
-	ssize_t idx = btree_trans_iter_idx(trans, iter);
+	int ret = btree_iter_err(iter);
 
-	trans->iters_live	&= ~(1ULL << idx);
-	trans->iters_linked	&= ~(1ULL << idx);
-	bch2_btree_iter_unlink(iter);
+	trans->iters_unlink_on_commit |= 1ULL << iter->idx;
+	return ret;
 }
 
 static int btree_trans_realloc_iters(struct btree_trans *trans,
 				     unsigned new_size)
 {
 	void *new_iters, *new_updates;
-	unsigned i;
 
 	BUG_ON(new_size > BTREE_ITER_MAX);
 
@@ -1727,6 +1685,11 @@ success:
 	memcpy(new_updates, trans->updates,
 	       sizeof(struct btree_insert_entry) * trans->nr_updates);
 
+	if (IS_ENABLED(CONFIG_BCACHEFS_DEBUG))
+		memset(trans->iters, POISON_FREE,
+		       sizeof(struct btree_iter) * trans->nr_iters +
+		       sizeof(struct btree_insert_entry) * trans->nr_iters);
+
 	if (trans->iters != trans->iters_onstack)
 		kfree(trans->iters);
 
@@ -1734,20 +1697,6 @@ success:
 	trans->updates	= new_updates;
 	trans->size	= new_size;
 
-	for (i = 0; i < trans->nr_iters; i++)
-		trans->iters[i].next = &trans->iters[i];
-
-	if (trans->iters_linked) {
-		unsigned first_linked = __ffs(trans->iters_linked);
-
-		for (i = first_linked + 1; i < trans->nr_iters; i++)
-			if (trans->iters_linked & (1 << i))
-				bch2_btree_iter_link(&trans->iters[first_linked],
-						     &trans->iters[i]);
-	}
-
-	btree_trans_verify(trans);
-
 	if (trans->iters_live) {
 		trans_restart();
 		return -EINTR;
@@ -1761,8 +1710,31 @@ void bch2_trans_preload_iters(struct btree_trans *trans)
 	btree_trans_realloc_iters(trans, BTREE_ITER_MAX);
 }
 
+static int btree_trans_iter_alloc(struct btree_trans *trans)
+{
+	unsigned idx = ffz(trans->iters_linked);
+
+	if (idx < trans->nr_iters)
+		goto got_slot;
+
+	if (trans->nr_iters == trans->size) {
+		int ret = btree_trans_realloc_iters(trans, trans->size * 2);
+		if (ret)
+			return ret;
+	}
+
+	idx = trans->nr_iters++;
+	BUG_ON(trans->nr_iters > trans->size);
+
+	trans->iters[idx].idx = idx;
+got_slot:
+	BUG_ON(trans->iters_linked & (1ULL << idx));
+	trans->iters_linked |= 1ULL << idx;
+	return idx;
+}
+
 static struct btree_iter *__btree_trans_get_iter(struct btree_trans *trans,
-						 unsigned btree_id,
+						 unsigned btree_id, struct bpos pos,
 						 unsigned flags, u64 iter_id)
 {
 	struct btree_iter *iter;
@@ -1770,32 +1742,28 @@ static struct btree_iter *__btree_trans_get_iter(struct btree_trans *trans,
 
 	BUG_ON(trans->nr_iters > BTREE_ITER_MAX);
 
-	for (idx = 0; idx < trans->nr_iters; idx++)
-		if (trans->iters[idx].id == iter_id)
+	for (idx = 0; idx < trans->nr_iters; idx++) {
+		if (!(trans->iters_linked & (1ULL << idx)))
+			continue;
+
+		iter = &trans->iters[idx];
+		if (iter_id
+		    ? iter->id == iter_id
+		    : (iter->btree_id == btree_id &&
+		       !bkey_cmp(iter->pos, pos)))
 			goto found;
+	}
 	idx = -1;
 found:
 	if (idx < 0) {
-		idx = ffz(trans->iters_linked);
-		if (idx < trans->nr_iters)
-			goto got_slot;
+		idx = btree_trans_iter_alloc(trans);
+		if (idx < 0)
+			return ERR_PTR(idx);
 
-		BUG_ON(trans->nr_iters > trans->size);
-
-		if (trans->nr_iters == trans->size) {
-			int ret = btree_trans_realloc_iters(trans,
-							trans->size * 2);
-			if (ret)
-				return ERR_PTR(ret);
-		}
-
-		idx = trans->nr_iters++;
-		BUG_ON(trans->nr_iters > trans->size);
-got_slot:
 		iter = &trans->iters[idx];
 		iter->id = iter_id;
 
-		bch2_btree_iter_init(iter, trans->c, btree_id, POS_MIN, flags);
+		bch2_btree_iter_init(trans, iter, btree_id, pos, flags);
 	} else {
 		iter = &trans->iters[idx];
 
@@ -1803,17 +1771,10 @@ got_slot:
 		iter->flags |= flags & (BTREE_ITER_INTENT|BTREE_ITER_PREFETCH);
 	}
 
+	BUG_ON(iter->btree_id != btree_id);
 	BUG_ON(trans->iters_live & (1ULL << idx));
-	trans->iters_live |= 1ULL << idx;
-
-	if (trans->iters_linked &&
-	    !(trans->iters_linked & (1 << idx)))
-		bch2_btree_iter_link(&trans->iters[__ffs(trans->iters_linked)],
-				     iter);
-
-	trans->iters_linked |= 1ULL << idx;
-
-	btree_trans_verify(trans);
+	trans->iters_live	|= 1ULL << idx;
+	trans->iters_touched	|= 1ULL << idx;
 
 	BUG_ON(iter->btree_id != btree_id);
 	BUG_ON((iter->flags ^ flags) & BTREE_ITER_TYPE);
@@ -1827,26 +1788,66 @@ struct btree_iter *__bch2_trans_get_iter(struct btree_trans *trans,
 					 u64 iter_id)
 {
 	struct btree_iter *iter =
-		__btree_trans_get_iter(trans, btree_id, flags, iter_id);
+		__btree_trans_get_iter(trans, btree_id, pos, flags, iter_id);
 
 	if (!IS_ERR(iter))
 		bch2_btree_iter_set_pos(iter, pos);
 	return iter;
 }
 
-struct btree_iter *__bch2_trans_copy_iter(struct btree_trans *trans,
-					  struct btree_iter *src,
-					  u64 iter_id)
+struct btree_iter *bch2_trans_get_node_iter(struct btree_trans *trans,
+					    enum btree_id btree_id,
+					    struct bpos pos,
+					    unsigned locks_want,
+					    unsigned depth,
+					    unsigned flags)
 {
 	struct btree_iter *iter =
-		__btree_trans_get_iter(trans, src->btree_id,
-				       src->flags, iter_id);
+		__btree_trans_get_iter(trans, btree_id, pos,
+				       flags|BTREE_ITER_NODES, 0);
+	unsigned i;
+
+	BUG_ON(IS_ERR(iter));
+	BUG_ON(bkey_cmp(iter->pos, pos));
+
+	iter->locks_want = locks_want;
+	iter->level	= depth;
+
+	for (i = 0; i < ARRAY_SIZE(iter->l); i++)
+		iter->l[i].b		= NULL;
+	iter->l[iter->level].b		= BTREE_ITER_NOT_END;
 
-	if (!IS_ERR(iter))
-		bch2_btree_iter_copy(iter, src);
 	return iter;
 }
 
+struct btree_iter *bch2_trans_copy_iter(struct btree_trans *trans,
+					struct btree_iter *src)
+{
+	struct btree_iter *iter;
+	int i, idx;
+
+	idx = btree_trans_iter_alloc(trans);
+	if (idx < 0)
+		return ERR_PTR(idx);
+
+	trans->iters_live		|= 1ULL << idx;
+	trans->iters_touched		|= 1ULL << idx;
+	trans->iters_unlink_on_restart	|= 1ULL << idx;
+
+	iter = &trans->iters[idx];
+
+	memcpy(&iter->trans,
+	       &src->trans,
+	       (void *) &iter[1] - (void *) &iter->trans);
+
+	for (i = 0; i < BTREE_MAX_DEPTH; i++)
+		if (btree_node_locked(iter, i))
+			six_lock_increment(&iter->l[i].b->lock,
+					   __btree_lock_want(iter, i));
+
+	return &trans->iters[idx];
+}
+
 void *bch2_trans_kmalloc(struct btree_trans *trans,
 			 size_t size)
 {
@@ -1883,8 +1884,7 @@ int bch2_trans_unlock(struct btree_trans *trans)
 		unsigned idx = __ffs(iters);
 		struct btree_iter *iter = &trans->iters[idx];
 
-		if (iter->flags & BTREE_ITER_ERROR)
-			ret = -EIO;
+		ret = ret ?: btree_iter_err(iter);
 
 		__bch2_btree_iter_unlock(iter);
 		iters ^= 1 << idx;
@@ -1893,12 +1893,22 @@ int bch2_trans_unlock(struct btree_trans *trans)
 	return ret;
 }
 
+inline void bch2_trans_unlink_iters(struct btree_trans *trans, u64 iters)
+{
+	iters &= trans->iters_linked;
+	iters &= ~trans->iters_live;
+
+	while (iters) {
+		unsigned idx = __ffs64(iters);
+
+		iters &= ~(1ULL << idx);
+		__bch2_trans_iter_free(trans, idx);
+	}
+}
+
 void __bch2_trans_begin(struct btree_trans *trans)
 {
-	u64 linked_not_live;
-	unsigned idx;
-
-	btree_trans_verify(trans);
+	u64 iters_to_unlink;
 
 	/*
 	 * On transaction restart, the transaction isn't required to allocate
@@ -1908,24 +1918,23 @@ void __bch2_trans_begin(struct btree_trans *trans)
 	 * further (allocated an iter with a higher idx) than where the iter
 	 * was originally allocated:
 	 */
-	while (1) {
-		linked_not_live = trans->iters_linked & ~trans->iters_live;
-		if (!linked_not_live)
-			break;
+	iters_to_unlink = ~trans->iters_live &
+		((1ULL << fls64(trans->iters_live)) - 1);
 
-		idx = __ffs64(linked_not_live);
-		if (1ULL << idx > trans->iters_live)
-			break;
+	iters_to_unlink |= trans->iters_unlink_on_restart;
+	iters_to_unlink |= trans->iters_unlink_on_commit;
 
-		trans->iters_linked ^= 1 << idx;
-		bch2_btree_iter_unlink(&trans->iters[idx]);
-	}
+	trans->iters_live		= 0;
 
-	trans->iters_live	= 0;
-	trans->nr_updates	= 0;
-	trans->mem_top		= 0;
+	bch2_trans_unlink_iters(trans, iters_to_unlink);
 
-	btree_trans_verify(trans);
+	trans->iters_touched		= 0;
+	trans->iters_unlink_on_restart	= 0;
+	trans->iters_unlink_on_commit	= 0;
+	trans->nr_updates		= 0;
+	trans->mem_top			= 0;
+
+	bch2_btree_iter_traverse_all(trans);
 }
 
 void bch2_trans_init(struct btree_trans *trans, struct bch_fs *c)
diff --git a/libbcachefs/btree_iter.h b/libbcachefs/btree_iter.h
index 7c49a661..c05b2dac 100644
--- a/libbcachefs/btree_iter.h
+++ b/libbcachefs/btree_iter.h
@@ -24,11 +24,35 @@ static inline struct btree *btree_node_parent(struct btree_iter *iter,
 	return btree_iter_node(iter, b->level + 1);
 }
 
-static inline bool btree_iter_linked(const struct btree_iter *iter)
+static inline bool btree_trans_has_multiple_iters(const struct btree_trans *trans)
 {
-	return iter->next != iter;
+	return hweight64(trans->iters_linked) > 1;
 }
 
+static inline int btree_iter_err(const struct btree_iter *iter)
+{
+	return iter->flags & BTREE_ITER_ERROR ? -EIO : 0;
+}
+
+/* Iterate over iters within a transaction: */
+
+static inline struct btree_iter *
+__trans_next_iter(struct btree_trans *trans, unsigned idx)
+{
+	EBUG_ON(idx < trans->nr_iters && trans->iters[idx].idx != idx);
+
+	for (; idx < trans->nr_iters; idx++)
+		if (trans->iters_linked & (1ULL << idx))
+			return &trans->iters[idx];
+
+	return NULL;
+}
+
+#define trans_for_each_iter(_trans, _iter)				\
+	for (_iter = __trans_next_iter((_trans), 0);			\
+	     (_iter);							\
+	     _iter = __trans_next_iter((_trans), (_iter)->idx + 1))
+
 static inline bool __iter_has_node(const struct btree_iter *iter,
 				   const struct btree *b)
 {
@@ -45,59 +69,32 @@ static inline bool __iter_has_node(const struct btree_iter *iter,
 }
 
 static inline struct btree_iter *
-__next_linked_iter(struct btree_iter *iter, struct btree_iter *linked)
+__trans_next_iter_with_node(struct btree_trans *trans, struct btree *b,
+			    unsigned idx)
 {
-	return linked->next != iter ? linked->next : NULL;
+	EBUG_ON(idx < trans->nr_iters && trans->iters[idx].idx != idx);
+
+	for (; idx < trans->nr_iters; idx++)
+		if ((trans->iters_linked & (1ULL << idx)) &&
+		    __iter_has_node(&trans->iters[idx], b))
+			return &trans->iters[idx];
+
+	return NULL;
 }
 
-static inline struct btree_iter *
-__next_iter_with_node(struct btree_iter *iter, struct btree *b,
-		      struct btree_iter *linked)
-{
-	while (linked && !__iter_has_node(linked, b))
-		linked = __next_linked_iter(iter, linked);
-
-	return linked;
-}
-
-/**
- * for_each_btree_iter - iterate over all iterators linked with @_iter,
- * including @_iter
- */
-#define for_each_btree_iter(_iter, _linked)				\
-	for ((_linked) = (_iter); (_linked);				\
-	     (_linked) = __next_linked_iter(_iter, _linked))
-
-/**
- * for_each_btree_iter_with_node - iterate over all iterators linked with @_iter
- * that also point to @_b
- *
- * @_b is assumed to be locked by @_iter
- *
- * Filters out iterators that don't have a valid btree_node iterator for @_b -
- * i.e. iterators for which bch2_btree_node_relock() would not succeed.
- */
-#define for_each_btree_iter_with_node(_iter, _b, _linked)		\
-	for ((_linked) = (_iter);					\
-	     ((_linked) = __next_iter_with_node(_iter, _b, _linked));	\
-	     (_linked) = __next_linked_iter(_iter, _linked))
-
-/**
- * for_each_linked_btree_iter - iterate over all iterators linked with @_iter,
- * _not_ including @_iter
- */
-#define for_each_linked_btree_iter(_iter, _linked)			\
-	for ((_linked) = (_iter)->next;					\
-	     (_linked) != (_iter);					\
-	     (_linked) = (_linked)->next)
+#define trans_for_each_iter_with_node(_trans, _b, _iter)		\
+	for (_iter = __trans_next_iter_with_node((_trans), (_b), 0);	\
+	     (_iter);							\
+	     _iter = __trans_next_iter_with_node((_trans), (_b),	\
+						 (_iter)->idx + 1))
 
 #ifdef CONFIG_BCACHEFS_DEBUG
 void bch2_btree_iter_verify(struct btree_iter *, struct btree *);
-void bch2_btree_iter_verify_locks(struct btree_iter *);
+void bch2_btree_trans_verify_locks(struct btree_trans *);
 #else
 static inline void bch2_btree_iter_verify(struct btree_iter *iter,
 					  struct btree *b) {}
-static inline void bch2_btree_iter_verify_locks(struct btree_iter *iter) {}
+static inline void bch2_btree_trans_verify_locks(struct btree_trans *iter) {}
 #endif
 
 void bch2_btree_node_iter_fix(struct btree_iter *, struct btree *,
@@ -105,7 +102,9 @@ void bch2_btree_node_iter_fix(struct btree_iter *, struct btree *,
 			      unsigned, unsigned);
 
 int bch2_btree_iter_unlock(struct btree_iter *);
-bool bch2_btree_iter_relock(struct btree_iter *);
+
+bool bch2_btree_trans_relock(struct btree_trans *);
+void bch2_btree_trans_unlock(struct btree_trans *);
 
 bool __bch2_btree_iter_upgrade(struct btree_iter *, unsigned);
 bool __bch2_btree_iter_upgrade_nounlock(struct btree_iter *, unsigned);
@@ -137,6 +136,7 @@ void bch2_btree_iter_node_drop(struct btree_iter *, struct btree *);
 void bch2_btree_iter_reinit_node(struct btree_iter *, struct btree *);
 
 int __must_check bch2_btree_iter_traverse(struct btree_iter *);
+int bch2_btree_iter_traverse_all(struct btree_trans *);
 
 struct btree *bch2_btree_iter_peek_node(struct btree_iter *);
 struct btree *bch2_btree_iter_next_node(struct btree_iter *, unsigned);
@@ -151,22 +151,6 @@ struct bkey_s_c bch2_btree_iter_next_slot(struct btree_iter *);
 void bch2_btree_iter_set_pos_same_leaf(struct btree_iter *, struct bpos);
 void bch2_btree_iter_set_pos(struct btree_iter *, struct bpos);
 
-void __bch2_btree_iter_init(struct btree_iter *, struct bch_fs *,
-			   enum btree_id, struct bpos,
-			   unsigned , unsigned, unsigned);
-
-static inline void bch2_btree_iter_init(struct btree_iter *iter,
-			struct bch_fs *c, enum btree_id btree_id,
-			struct bpos pos, unsigned flags)
-{
-	__bch2_btree_iter_init(iter, c, btree_id, pos,
-			       flags & BTREE_ITER_INTENT ? 1 : 0, 0,
-			       (btree_id == BTREE_ID_EXTENTS
-				?  BTREE_ITER_IS_EXTENTS : 0)|flags);
-}
-
-void bch2_btree_iter_copy(struct btree_iter *, struct btree_iter *);
-
 static inline struct bpos btree_type_successor(enum btree_id id,
 					       struct bpos pos)
 {
@@ -208,31 +192,34 @@ static inline int btree_iter_cmp(const struct btree_iter *l,
 	return __btree_iter_cmp(l->btree_id, l->pos, r);
 }
 
+int bch2_trans_unlock(struct btree_trans *);
+
 /*
  * Unlocks before scheduling
  * Note: does not revalidate iterator
  */
-static inline void bch2_btree_iter_cond_resched(struct btree_iter *iter)
+static inline void bch2_trans_cond_resched(struct btree_trans *trans)
 {
 	if (need_resched()) {
-		bch2_btree_iter_unlock(iter);
+		bch2_trans_unlock(trans);
 		schedule();
 	} else if (race_fault()) {
-		bch2_btree_iter_unlock(iter);
+		bch2_trans_unlock(trans);
 	}
 }
 
-#define __for_each_btree_node(_iter, _c, _btree_id, _start,		\
+#define __for_each_btree_node(_trans, _iter, _btree_id, _start,	\
 			      _locks_want, _depth, _flags, _b)		\
-	for (__bch2_btree_iter_init((_iter), (_c), (_btree_id), _start,	\
-				    _locks_want, _depth,		\
-				    _flags|BTREE_ITER_NODES),		\
+	for (iter = bch2_trans_get_node_iter((_trans), (_btree_id),	\
+				_start, _locks_want, _depth, _flags),	\
 	     _b = bch2_btree_iter_peek_node(_iter);			\
 	     (_b);							\
 	     (_b) = bch2_btree_iter_next_node(_iter, _depth))
 
-#define for_each_btree_node(_iter, _c, _btree_id, _start, _flags, _b)	\
-	__for_each_btree_node(_iter, _c, _btree_id, _start, 0, 0, _flags, _b)
+#define for_each_btree_node(_trans, _iter, _btree_id, _start,		\
+			    _flags, _b)					\
+	__for_each_btree_node(_trans, _iter, _btree_id, _start,		\
+			      0, 0, _flags, _b)
 
 static inline struct bkey_s_c __bch2_btree_iter_peek(struct btree_iter *iter,
 						     unsigned flags)
@@ -245,16 +232,16 @@ static inline struct bkey_s_c __bch2_btree_iter_peek(struct btree_iter *iter,
 static inline struct bkey_s_c __bch2_btree_iter_next(struct btree_iter *iter,
 						     unsigned flags)
 {
-	bch2_btree_iter_cond_resched(iter);
+	bch2_trans_cond_resched(iter->trans);
 
 	return flags & BTREE_ITER_SLOTS
 		? bch2_btree_iter_next_slot(iter)
 		: bch2_btree_iter_next(iter);
 }
 
-#define for_each_btree_key(_iter, _c, _btree_id,  _start, _flags, _k)	\
-	for (bch2_btree_iter_init((_iter), (_c), (_btree_id),		\
-				  (_start), (_flags)),			\
+#define for_each_btree_key(_trans, _iter, _btree_id,  _start, _flags, _k)\
+	for (iter = bch2_trans_get_iter((_trans), (_btree_id),		\
+					(_start), (_flags)),		\
 	     (_k) = __bch2_btree_iter_peek(_iter, _flags);		\
 	     !IS_ERR_OR_NULL((_k).k);					\
 	     (_k) = __bch2_btree_iter_next(_iter, _flags))
@@ -264,7 +251,7 @@ static inline struct bkey_s_c __bch2_btree_iter_next(struct btree_iter *iter,
 	     !IS_ERR_OR_NULL((_k).k);					\
 	     (_k) = __bch2_btree_iter_next(_iter, _flags))
 
-static inline int btree_iter_err(struct bkey_s_c k)
+static inline int bkey_err(struct bkey_s_c k)
 {
 	return PTR_ERR_OR_ZERO(k.k);
 }
@@ -272,13 +259,16 @@ static inline int btree_iter_err(struct bkey_s_c k)
 /* new multiple iterator interface: */
 
 void bch2_trans_preload_iters(struct btree_trans *);
-void bch2_trans_iter_put(struct btree_trans *, struct btree_iter *);
-void bch2_trans_iter_free(struct btree_trans *, struct btree_iter *);
+int bch2_trans_iter_put(struct btree_trans *, struct btree_iter *);
+int bch2_trans_iter_free(struct btree_trans *, struct btree_iter *);
+int bch2_trans_iter_free_on_commit(struct btree_trans *, struct btree_iter *);
+
+void bch2_trans_unlink_iters(struct btree_trans *, u64);
 
 struct btree_iter *__bch2_trans_get_iter(struct btree_trans *, enum btree_id,
 					 struct bpos, unsigned, u64);
-struct btree_iter *__bch2_trans_copy_iter(struct btree_trans *,
-					  struct btree_iter *, u64);
+struct btree_iter *bch2_trans_copy_iter(struct btree_trans *,
+					struct btree_iter *);
 
 static __always_inline u64 __btree_iter_id(void)
 {
@@ -299,12 +289,9 @@ bch2_trans_get_iter(struct btree_trans *trans, enum btree_id btree_id,
 				     __btree_iter_id());
 }
 
-static __always_inline struct btree_iter *
-bch2_trans_copy_iter(struct btree_trans *trans, struct btree_iter *src)
-{
-
-	return __bch2_trans_copy_iter(trans, src, __btree_iter_id());
-}
+struct btree_iter *bch2_trans_get_node_iter(struct btree_trans *,
+				enum btree_id, struct bpos,
+				unsigned, unsigned, unsigned);
 
 void __bch2_trans_begin(struct btree_trans *);
 
@@ -314,7 +301,6 @@ static inline void bch2_trans_begin_updates(struct btree_trans *trans)
 }
 
 void *bch2_trans_kmalloc(struct btree_trans *, size_t);
-int bch2_trans_unlock(struct btree_trans *);
 void bch2_trans_init(struct btree_trans *, struct bch_fs *);
 int bch2_trans_exit(struct btree_trans *);
 
diff --git a/libbcachefs/btree_locking.h b/libbcachefs/btree_locking.h
index f565fa36..e9686197 100644
--- a/libbcachefs/btree_locking.h
+++ b/libbcachefs/btree_locking.h
@@ -163,8 +163,9 @@ static inline bool btree_node_lock_increment(struct btree_iter *iter,
 {
 	struct btree_iter *linked;
 
-	for_each_linked_btree_iter(iter, linked)
-		if (linked->l[level].b == b &&
+	trans_for_each_iter(iter->trans, linked)
+		if (linked != iter &&
+		    linked->l[level].b == b &&
 		    btree_node_locked_type(linked, level) >= want) {
 			six_lock_increment(&b->lock, want);
 			return true;
diff --git a/libbcachefs/btree_types.h b/libbcachefs/btree_types.h
index d566722a..3d869dd8 100644
--- a/libbcachefs/btree_types.h
+++ b/libbcachefs/btree_types.h
@@ -10,6 +10,7 @@
 
 struct open_bucket;
 struct btree_update;
+struct btree_trans;
 
 #define MAX_BSETS		3U
 
@@ -208,7 +209,9 @@ enum btree_iter_uptodate {
  * @nodes_intent_locked	- bitmask indicating which locks are intent locks
  */
 struct btree_iter {
-	struct bch_fs		*c;
+	u8			idx;
+
+	struct btree_trans	*trans;
 	struct bpos		pos;
 
 	u8			flags;
@@ -232,15 +235,6 @@ struct btree_iter {
 	struct bkey		k;
 
 	u64			id;
-
-	/*
-	 * Circular linked list of linked iterators: linked iterators share
-	 * locks (e.g. two linked iterators may have the same node intent
-	 * locked, or read and write locked, at the same time), and insertions
-	 * through one iterator won't invalidate the other linked iterators.
-	 */
-	/* Must come last: */
-	struct btree_iter	*next;
 };
 
 struct deferred_update {
@@ -275,8 +269,11 @@ struct btree_trans {
 	size_t			nr_restarts;
 	u64			commit_start;
 
-	u64			iters_live;
 	u64			iters_linked;
+	u64			iters_live;
+	u64			iters_touched;
+	u64			iters_unlink_on_restart;
+	u64			iters_unlink_on_commit;
 
 	u8			nr_iters;
 	u8			nr_updates;
diff --git a/libbcachefs/btree_update.h b/libbcachefs/btree_update.h
index ce5fa6b2..944b6c24 100644
--- a/libbcachefs/btree_update.h
+++ b/libbcachefs/btree_update.h
@@ -98,19 +98,13 @@ int bch2_btree_node_rewrite(struct bch_fs *c, struct btree_iter *,
 int bch2_btree_node_update_key(struct bch_fs *, struct btree_iter *,
 			       struct btree *, struct bkey_i_btree_ptr *);
 
-static inline void
-bch2_trans_update(struct btree_trans *trans,
-		  struct btree_insert_entry entry)
-{
-	BUG_ON(trans->nr_updates >= trans->nr_iters + 4);
-
-	trans->updates[trans->nr_updates++] = entry;
-}
-
 int bch2_trans_commit(struct btree_trans *,
 		      struct disk_reservation *,
 		      u64 *, unsigned);
 
+struct btree_insert_entry *bch2_trans_update(struct btree_trans *,
+					     struct btree_insert_entry);
+
 #define bch2_trans_do(_c, _journal_seq, _flags, _do)			\
 ({									\
 	struct btree_trans trans;					\
diff --git a/libbcachefs/btree_update_interior.c b/libbcachefs/btree_update_interior.c
index 47196c14..62021727 100644
--- a/libbcachefs/btree_update_interior.c
+++ b/libbcachefs/btree_update_interior.c
@@ -245,7 +245,7 @@ void bch2_btree_node_free_inmem(struct bch_fs *c, struct btree *b,
 {
 	struct btree_iter *linked;
 
-	for_each_btree_iter(iter, linked)
+	trans_for_each_iter(iter->trans, linked)
 		BUG_ON(linked->l[b->level].b == b);
 
 	/*
@@ -1437,7 +1437,7 @@ static void btree_split(struct btree_update *as, struct btree *b,
 
 	bch2_btree_node_free_inmem(c, b, iter);
 
-	bch2_btree_iter_verify_locks(iter);
+	bch2_btree_trans_verify_locks(iter->trans);
 
 	bch2_time_stats_update(&c->times[BCH_TIME_btree_node_split],
 			       start_time);
@@ -1473,7 +1473,7 @@ bch2_btree_insert_keys_interior(struct btree_update *as, struct btree *b,
 
 	btree_update_updated_node(as, b);
 
-	for_each_btree_iter_with_node(iter, b, linked)
+	trans_for_each_iter_with_node(iter->trans, b, linked)
 		bch2_btree_node_iter_peek(&linked->l[b->level].iter, b);
 
 	bch2_btree_iter_verify(iter, b);
@@ -1558,7 +1558,7 @@ int bch2_btree_split_leaf(struct bch_fs *c, struct btree_iter *iter,
 	 * We already have a disk reservation and open buckets pinned; this
 	 * allocation must not block:
 	 */
-	for_each_btree_iter(iter, linked)
+	trans_for_each_iter(iter->trans, linked)
 		if (linked->btree_id == BTREE_ID_EXTENTS)
 			flags |= BTREE_INSERT_USE_RESERVE;
 
@@ -1570,10 +1570,10 @@ int bch2_btree_split_leaf(struct bch_fs *c, struct btree_iter *iter,
 		if (flags & BTREE_INSERT_NOUNLOCK)
 			return -EINTR;
 
-		bch2_btree_iter_unlock(iter);
+		bch2_btree_trans_unlock(iter->trans);
 		down_read(&c->gc_lock);
 
-		if (btree_iter_linked(iter))
+		if (!bch2_btree_trans_relock(iter->trans))
 			ret = -EINTR;
 	}
 
@@ -1752,7 +1752,7 @@ retry:
 	if (!(flags & BTREE_INSERT_GC_LOCK_HELD))
 		up_read(&c->gc_lock);
 out:
-	bch2_btree_iter_verify_locks(iter);
+	bch2_btree_trans_verify_locks(iter->trans);
 
 	/*
 	 * Don't downgrade locks here: we're called after successful insert,
@@ -2035,10 +2035,10 @@ int bch2_btree_node_update_key(struct bch_fs *c, struct btree_iter *iter,
 		return -EINTR;
 
 	if (!down_read_trylock(&c->gc_lock)) {
-		bch2_btree_iter_unlock(iter);
+		bch2_btree_trans_unlock(iter->trans);
 		down_read(&c->gc_lock);
 
-		if (!bch2_btree_iter_relock(iter)) {
+		if (!bch2_btree_trans_relock(iter->trans)) {
 			ret = -EINTR;
 			goto err;
 		}
@@ -2049,15 +2049,15 @@ int bch2_btree_node_update_key(struct bch_fs *c, struct btree_iter *iter,
 		/* bch2_btree_reserve_get will unlock */
 		ret = bch2_btree_cache_cannibalize_lock(c, &cl);
 		if (ret) {
-			ret = -EINTR;
-
-			bch2_btree_iter_unlock(iter);
+			bch2_btree_trans_unlock(iter->trans);
 			up_read(&c->gc_lock);
 			closure_sync(&cl);
 			down_read(&c->gc_lock);
 
-			if (!bch2_btree_iter_relock(iter))
+			if (!bch2_btree_trans_relock(iter->trans)) {
+				ret = -EINTR;
 				goto err;
+			}
 		}
 
 		new_hash = bch2_btree_node_mem_alloc(c);
@@ -2078,12 +2078,12 @@ int bch2_btree_node_update_key(struct bch_fs *c, struct btree_iter *iter,
 		if (ret != -EINTR)
 			goto err;
 
-		bch2_btree_iter_unlock(iter);
+		bch2_btree_trans_unlock(iter->trans);
 		up_read(&c->gc_lock);
 		closure_sync(&cl);
 		down_read(&c->gc_lock);
 
-		if (!bch2_btree_iter_relock(iter))
+		if (!bch2_btree_trans_relock(iter->trans))
 			goto err;
 	}
 
diff --git a/libbcachefs/btree_update_leaf.c b/libbcachefs/btree_update_leaf.c
index e207b099..142230cf 100644
--- a/libbcachefs/btree_update_leaf.c
+++ b/libbcachefs/btree_update_leaf.c
@@ -50,25 +50,6 @@ static void btree_trans_unlock_write(struct btree_trans *trans)
 		bch2_btree_node_unlock_write(i->iter->l[0].b, i->iter);
 }
 
-static bool btree_trans_relock(struct btree_trans *trans)
-{
-	struct btree_insert_entry *i;
-
-	trans_for_each_update_iter(trans, i)
-		return bch2_btree_iter_relock(i->iter);
-	return true;
-}
-
-static void btree_trans_unlock(struct btree_trans *trans)
-{
-	struct btree_insert_entry *i;
-
-	trans_for_each_update_iter(trans, i) {
-		bch2_btree_iter_unlock(i->iter);
-		break;
-	}
-}
-
 static inline int btree_trans_cmp(struct btree_insert_entry l,
 				  struct btree_insert_entry r)
 {
@@ -421,8 +402,6 @@ static inline void btree_insert_entry_checks(struct btree_trans *trans,
 
 		EBUG_ON((i->iter->flags & BTREE_ITER_IS_EXTENTS) &&
 			!(trans->flags & BTREE_INSERT_ATOMIC));
-
-		bch2_btree_iter_verify_locks(i->iter);
 	}
 
 	BUG_ON(debug_check_bkeys(c) &&
@@ -450,14 +429,14 @@ static int bch2_trans_journal_preres_get(struct btree_trans *trans)
 	if (ret != -EAGAIN)
 		return ret;
 
-	btree_trans_unlock(trans);
+	bch2_btree_trans_unlock(trans);
 
 	ret = bch2_journal_preres_get(&c->journal,
 			&trans->journal_preres, u64s, 0);
 	if (ret)
 		return ret;
 
-	if (!btree_trans_relock(trans)) {
+	if (!bch2_btree_trans_relock(trans)) {
 		trans_restart(" (iter relock after journal preres get blocked)");
 		return -EINTR;
 	}
@@ -616,12 +595,9 @@ static inline int do_btree_insert_at(struct btree_trans *trans,
 		 * have been traversed/locked, depending on what the caller was
 		 * doing:
 		 */
-		trans_for_each_update_iter(trans, i) {
-			for_each_btree_iter(i->iter, linked)
-				if (linked->uptodate < BTREE_ITER_NEED_RELOCK)
-					linked->flags |= BTREE_ITER_NOUNLOCK;
-			break;
-		}
+		trans_for_each_iter(trans, linked)
+			if (linked->uptodate < BTREE_ITER_NEED_RELOCK)
+				linked->flags |= BTREE_ITER_NOUNLOCK;
 	}
 
 	trans_for_each_update_iter(trans, i)
@@ -706,20 +682,20 @@ int bch2_trans_commit_error(struct btree_trans *trans,
 				return ret;
 		}
 
-		if (btree_trans_relock(trans))
+		if (bch2_btree_trans_relock(trans))
 			return 0;
 
 		trans_restart(" (iter relock after marking replicas)");
 		ret = -EINTR;
 		break;
 	case BTREE_INSERT_NEED_JOURNAL_RES:
-		btree_trans_unlock(trans);
+		bch2_btree_trans_unlock(trans);
 
 		ret = bch2_trans_journal_res_get(trans, JOURNAL_RES_GET_CHECK);
 		if (ret)
 			return ret;
 
-		if (btree_trans_relock(trans))
+		if (bch2_btree_trans_relock(trans))
 			return 0;
 
 		trans_restart(" (iter relock after journal res get blocked)");
@@ -731,14 +707,11 @@ int bch2_trans_commit_error(struct btree_trans *trans,
 	}
 
 	if (ret == -EINTR) {
-		trans_for_each_update_iter(trans, i) {
-			int ret2 = bch2_btree_iter_traverse(i->iter);
-			if (ret2) {
-				trans_restart(" (traverse)");
-				return ret2;
-			}
+		int ret2 = bch2_btree_iter_traverse_all(trans);
 
-			BUG_ON(i->iter->uptodate > BTREE_ITER_NEED_PEEK);
+		if (ret2) {
+			trans_restart(" (traverse)");
+			return ret2;
 		}
 
 		/*
@@ -784,10 +757,9 @@ static int __bch2_trans_commit(struct btree_trans *trans,
 			goto err;
 		}
 
-		if (i->iter->flags & BTREE_ITER_ERROR) {
-			ret = -EIO;
+		ret = btree_iter_err(i->iter);
+		if (ret)
 			goto err;
-		}
 	}
 
 	ret = do_btree_insert_at(trans, stopped_at);
@@ -801,16 +773,10 @@ static int __bch2_trans_commit(struct btree_trans *trans,
 		bch2_btree_iter_downgrade(i->iter);
 err:
 	/* make sure we didn't drop or screw up locks: */
-	trans_for_each_update_iter(trans, i) {
-		bch2_btree_iter_verify_locks(i->iter);
-		break;
-	}
+	bch2_btree_trans_verify_locks(trans);
 
-	trans_for_each_update_iter(trans, i) {
-		for_each_btree_iter(i->iter, linked)
-			linked->flags &= ~BTREE_ITER_NOUNLOCK;
-		break;
-	}
+	trans_for_each_iter(trans, linked)
+		linked->flags &= ~BTREE_ITER_NOUNLOCK;
 
 	return ret;
 }
@@ -842,17 +808,16 @@ int bch2_trans_commit(struct btree_trans *trans,
 	trans->journal_seq	= journal_seq;
 	trans->flags		= flags;
 
-	bubble_sort(trans->updates, trans->nr_updates, btree_trans_cmp);
-
 	trans_for_each_update(trans, i)
 		btree_insert_entry_checks(trans, i);
+	bch2_btree_trans_verify_locks(trans);
 
 	if (unlikely(!(trans->flags & BTREE_INSERT_NOCHECK_RW) &&
 		     !percpu_ref_tryget(&c->writes))) {
 		if (likely(!(trans->flags & BTREE_INSERT_LAZY_RW)))
 			return -EROFS;
 
-		btree_trans_unlock(trans);
+		bch2_btree_trans_unlock(trans);
 
 		ret = bch2_fs_read_write_early(c);
 		if (ret)
@@ -860,7 +825,7 @@ int bch2_trans_commit(struct btree_trans *trans,
 
 		percpu_ref_get(&c->writes);
 
-		if (!btree_trans_relock(trans)) {
+		if (!bch2_btree_trans_relock(trans)) {
 			ret = -EINTR;
 			goto err;
 		}
@@ -885,10 +850,15 @@ out_noupdates:
 		trans->commit_start = 0;
 	}
 
-	trans->nr_updates = 0;
-
 	BUG_ON(!(trans->flags & BTREE_INSERT_ATOMIC) && ret == -EINTR);
 
+	bch2_trans_unlink_iters(trans, trans->iters_unlink_on_commit);
+	if (!ret) {
+		bch2_trans_unlink_iters(trans, ~trans->iters_touched);
+		trans->iters_touched = 0;
+	}
+	trans->nr_updates = 0;
+
 	return ret;
 err:
 	ret = bch2_trans_commit_error(trans, i, ret);
@@ -898,6 +868,26 @@ err:
 	goto out;
 }
 
+struct btree_insert_entry *bch2_trans_update(struct btree_trans *trans,
+					     struct btree_insert_entry entry)
+{
+	struct btree_insert_entry *i;
+
+	BUG_ON(trans->nr_updates >= trans->nr_iters + 4);
+
+	for (i = trans->updates;
+	     i < trans->updates + trans->nr_updates;
+	     i++)
+		if (btree_trans_cmp(entry, *i) < 0)
+			break;
+
+	memmove(&i[1], &i[0],
+		(void *) &trans->updates[trans->nr_updates] - (void *) i);
+	trans->nr_updates++;
+	*i = entry;
+	return i;
+}
+
 int bch2_btree_delete_at(struct btree_trans *trans,
 			 struct btree_iter *iter, unsigned flags)
 {
@@ -960,7 +950,7 @@ int bch2_btree_delete_range(struct bch_fs *c, enum btree_id id,
 	iter = bch2_trans_get_iter(&trans, id, start, BTREE_ITER_INTENT);
 
 	while ((k = bch2_btree_iter_peek(iter)).k &&
-	       !(ret = btree_iter_err(k)) &&
+	       !(ret = bkey_err(k)) &&
 	       bkey_cmp(iter->pos, end) < 0) {
 		unsigned max_sectors = KEY_SIZE_MAX & (~0 << c->block_bits);
 		/* really shouldn't be using a bare, unpadded bkey_i */
@@ -997,7 +987,7 @@ int bch2_btree_delete_range(struct bch_fs *c, enum btree_id id,
 		if (ret)
 			break;
 
-		bch2_btree_iter_cond_resched(iter);
+		bch2_trans_cond_resched(&trans);
 	}
 
 	bch2_trans_exit(&trans);
diff --git a/libbcachefs/chardev.c b/libbcachefs/chardev.c
index 4e33e7b8..82d90cde 100644
--- a/libbcachefs/chardev.c
+++ b/libbcachefs/chardev.c
@@ -302,8 +302,8 @@ static ssize_t bch2_data_job_read(struct file *file, char __user *buf,
 	struct bch_ioctl_data_event e = {
 		.type			= BCH_DATA_EVENT_PROGRESS,
 		.p.data_type		= ctx->stats.data_type,
-		.p.btree_id		= ctx->stats.iter.btree_id,
-		.p.pos			= ctx->stats.iter.pos,
+		.p.btree_id		= ctx->stats.btree_id,
+		.p.pos			= ctx->stats.pos,
 		.p.sectors_done		= atomic64_read(&ctx->stats.sectors_seen),
 		.p.sectors_total	= bch2_fs_usage_read_short(c).used,
 	};
diff --git a/libbcachefs/debug.c b/libbcachefs/debug.c
index e8a671a1..a22ac8d6 100644
--- a/libbcachefs/debug.c
+++ b/libbcachefs/debug.c
@@ -204,7 +204,8 @@ static ssize_t bch2_read_btree(struct file *file, char __user *buf,
 			       size_t size, loff_t *ppos)
 {
 	struct dump_iter *i = file->private_data;
-	struct btree_iter iter;
+	struct btree_trans trans;
+	struct btree_iter *iter;
 	struct bkey_s_c k;
 	int err;
 
@@ -219,18 +220,20 @@ static ssize_t bch2_read_btree(struct file *file, char __user *buf,
 	if (!i->size)
 		return i->ret;
 
-	bch2_btree_iter_init(&iter, i->c, i->id, i->from, BTREE_ITER_PREFETCH);
-	k = bch2_btree_iter_peek(&iter);
+	bch2_trans_init(&trans, i->c);
 
-	while (k.k && !(err = btree_iter_err(k))) {
+	iter = bch2_trans_get_iter(&trans, i->id, i->from, BTREE_ITER_PREFETCH);
+	k = bch2_btree_iter_peek(iter);
+
+	while (k.k && !(err = bkey_err(k))) {
 		bch2_bkey_val_to_text(&PBUF(i->buf), i->c, k);
 		i->bytes = strlen(i->buf);
 		BUG_ON(i->bytes >= PAGE_SIZE);
 		i->buf[i->bytes] = '\n';
 		i->bytes++;
 
-		k = bch2_btree_iter_next(&iter);
-		i->from = iter.pos;
+		k = bch2_btree_iter_next(iter);
+		i->from = iter->pos;
 
 		err = flush_buf(i);
 		if (err)
@@ -239,7 +242,7 @@ static ssize_t bch2_read_btree(struct file *file, char __user *buf,
 		if (!i->size)
 			break;
 	}
-	bch2_btree_iter_unlock(&iter);
+	bch2_trans_exit(&trans);
 
 	return err < 0 ? err : i->ret;
 }
@@ -255,7 +258,8 @@ static ssize_t bch2_read_btree_formats(struct file *file, char __user *buf,
 				       size_t size, loff_t *ppos)
 {
 	struct dump_iter *i = file->private_data;
-	struct btree_iter iter;
+	struct btree_trans trans;
+	struct btree_iter *iter;
 	struct btree *b;
 	int err;
 
@@ -270,7 +274,9 @@ static ssize_t bch2_read_btree_formats(struct file *file, char __user *buf,
 	if (!i->size || !bkey_cmp(POS_MAX, i->from))
 		return i->ret;
 
-	for_each_btree_node(&iter, i->c, i->id, i->from, 0, b) {
+	bch2_trans_init(&trans, i->c);
+
+	for_each_btree_node(&trans, iter, i->id, i->from, 0, b) {
 		bch2_btree_node_to_text(&PBUF(i->buf), i->c, b);
 		i->bytes = strlen(i->buf);
 		err = flush_buf(i);
@@ -288,7 +294,7 @@ static ssize_t bch2_read_btree_formats(struct file *file, char __user *buf,
 		if (!i->size)
 			break;
 	}
-	bch2_btree_iter_unlock(&iter);
+	bch2_trans_exit(&trans);
 
 	return err < 0 ? err : i->ret;
 }
@@ -304,7 +310,8 @@ static ssize_t bch2_read_bfloat_failed(struct file *file, char __user *buf,
 				       size_t size, loff_t *ppos)
 {
 	struct dump_iter *i = file->private_data;
-	struct btree_iter iter;
+	struct btree_trans trans;
+	struct btree_iter *iter;
 	struct bkey_s_c k;
 	struct btree *prev_node = NULL;
 	int err;
@@ -320,11 +327,13 @@ static ssize_t bch2_read_bfloat_failed(struct file *file, char __user *buf,
 	if (!i->size)
 		return i->ret;
 
-	bch2_btree_iter_init(&iter, i->c, i->id, i->from, BTREE_ITER_PREFETCH);
+	bch2_trans_init(&trans, i->c);
 
-	while ((k = bch2_btree_iter_peek(&iter)).k &&
-	       !(err = btree_iter_err(k))) {
-		struct btree_iter_level *l = &iter.l[0];
+	iter = bch2_trans_get_iter(&trans, i->id, i->from, BTREE_ITER_PREFETCH);
+
+	while ((k = bch2_btree_iter_peek(iter)).k &&
+	       !(err = bkey_err(k))) {
+		struct btree_iter_level *l = &iter->l[0];
 		struct bkey_packed *_k =
 			bch2_btree_node_iter_peek(&l->iter, l->b);
 
@@ -343,8 +352,8 @@ static ssize_t bch2_read_bfloat_failed(struct file *file, char __user *buf,
 		if (err)
 			break;
 
-		bch2_btree_iter_next(&iter);
-		i->from = iter.pos;
+		bch2_btree_iter_next(iter);
+		i->from = iter->pos;
 
 		err = flush_buf(i);
 		if (err)
@@ -353,7 +362,7 @@ static ssize_t bch2_read_bfloat_failed(struct file *file, char __user *buf,
 		if (!i->size)
 			break;
 	}
-	bch2_btree_iter_unlock(&iter);
+	bch2_trans_exit(&trans);
 
 	return err < 0 ? err : i->ret;
 }
diff --git a/libbcachefs/dirent.c b/libbcachefs/dirent.c
index 550561e6..58289fcc 100644
--- a/libbcachefs/dirent.c
+++ b/libbcachefs/dirent.c
@@ -330,11 +330,15 @@ out:
 
 int bch2_empty_dir(struct bch_fs *c, u64 dir_inum)
 {
-	struct btree_iter iter;
+	struct btree_trans trans;
+	struct btree_iter *iter;
 	struct bkey_s_c k;
 	int ret = 0;
 
-	for_each_btree_key(&iter, c, BTREE_ID_DIRENTS, POS(dir_inum, 0), 0, k) {
+	bch2_trans_init(&trans, c);
+
+	for_each_btree_key(&trans, iter, BTREE_ID_DIRENTS,
+			   POS(dir_inum, 0), 0, k) {
 		if (k.k->p.inode > dir_inum)
 			break;
 
@@ -343,7 +347,7 @@ int bch2_empty_dir(struct bch_fs *c, u64 dir_inum)
 			break;
 		}
 	}
-	bch2_btree_iter_unlock(&iter);
+	bch2_trans_exit(&trans);
 
 	return ret;
 }
@@ -352,7 +356,8 @@ int bch2_readdir(struct bch_fs *c, struct file *file,
 		 struct dir_context *ctx)
 {
 	struct bch_inode_info *inode = file_bch_inode(file);
-	struct btree_iter iter;
+	struct btree_trans trans;
+	struct btree_iter *iter;
 	struct bkey_s_c k;
 	struct bkey_s_c_dirent dirent;
 	unsigned len;
@@ -360,7 +365,9 @@ int bch2_readdir(struct bch_fs *c, struct file *file,
 	if (!dir_emit_dots(file, ctx))
 		return 0;
 
-	for_each_btree_key(&iter, c, BTREE_ID_DIRENTS,
+	bch2_trans_init(&trans, c);
+
+	for_each_btree_key(&trans, iter, BTREE_ID_DIRENTS,
 			   POS(inode->v.i_ino, ctx->pos), 0, k) {
 		if (k.k->type != KEY_TYPE_dirent)
 			continue;
@@ -386,7 +393,7 @@ int bch2_readdir(struct bch_fs *c, struct file *file,
 
 		ctx->pos = k.k->p.offset + 1;
 	}
-	bch2_btree_iter_unlock(&iter);
+	bch2_trans_exit(&trans);
 
 	return 0;
 }
diff --git a/libbcachefs/ec.c b/libbcachefs/ec.c
index ea6f4867..e5df9149 100644
--- a/libbcachefs/ec.c
+++ b/libbcachefs/ec.c
@@ -397,7 +397,8 @@ static void ec_block_io(struct bch_fs *c, struct ec_stripe_buf *buf,
 /* recovery read path: */
 int bch2_ec_read_extent(struct bch_fs *c, struct bch_read_bio *rbio)
 {
-	struct btree_iter iter;
+	struct btree_trans trans;
+	struct btree_iter *iter;
 	struct ec_stripe_buf *buf;
 	struct closure cl;
 	struct bkey_s_c k;
@@ -418,19 +419,21 @@ int bch2_ec_read_extent(struct bch_fs *c, struct bch_read_bio *rbio)
 	if (!buf)
 		return -ENOMEM;
 
-	bch2_btree_iter_init(&iter, c, BTREE_ID_EC,
-			     POS(0, stripe_idx),
-			     BTREE_ITER_SLOTS);
-	k = bch2_btree_iter_peek_slot(&iter);
-	if (btree_iter_err(k) || k.k->type != KEY_TYPE_stripe) {
+	bch2_trans_init(&trans, c);
+
+	iter = bch2_trans_get_iter(&trans, BTREE_ID_EC,
+				   POS(0, stripe_idx),
+				   BTREE_ITER_SLOTS);
+	k = bch2_btree_iter_peek_slot(iter);
+	if (bkey_err(k) || k.k->type != KEY_TYPE_stripe) {
 		__bcache_io_error(c,
 			"error doing reconstruct read: stripe not found");
 		kfree(buf);
-		return bch2_btree_iter_unlock(&iter) ?: -EIO;
+		return bch2_trans_exit(&trans) ?: -EIO;
 	}
 
 	bkey_reassemble(&buf->key.k_i, k);
-	bch2_btree_iter_unlock(&iter);
+	bch2_trans_exit(&trans);
 
 	v = &buf->key.v;
 
@@ -537,7 +540,7 @@ static int ec_stripe_mem_alloc(struct bch_fs *c,
 	if (!__ec_stripe_mem_alloc(c, idx, GFP_NOWAIT))
 		return 0;
 
-	bch2_btree_iter_unlock(iter);
+	bch2_btree_trans_unlock(iter->trans);
 
 	if (!__ec_stripe_mem_alloc(c, idx, GFP_KERNEL))
 		return -EINTR;
@@ -746,7 +749,7 @@ static int ec_stripe_update_ptrs(struct bch_fs *c,
 				   BTREE_ITER_INTENT);
 
 	while ((k = bch2_btree_iter_peek(iter)).k &&
-	       !(ret = btree_iter_err(k)) &&
+	       !(ret = bkey_err(k)) &&
 	       bkey_cmp(bkey_start_pos(k.k), pos->p) < 0) {
 		idx = extent_matches_stripe(c, &s->key.v, k);
 		if (idx < 0) {
@@ -1166,7 +1169,7 @@ static int __bch2_stripe_write_key(struct btree_trans *trans,
 	bch2_btree_iter_set_pos(iter, POS(0, idx));
 
 	k = bch2_btree_iter_peek_slot(iter);
-	ret = btree_iter_err(k);
+	ret = bkey_err(k);
 	if (ret)
 		return ret;
 
@@ -1237,7 +1240,8 @@ static void bch2_stripe_read_key(struct bch_fs *c, struct bkey_s_c k)
 int bch2_stripes_read(struct bch_fs *c, struct list_head *journal_replay_list)
 {
 	struct journal_replay *r;
-	struct btree_iter iter;
+	struct btree_trans trans;
+	struct btree_iter *iter;
 	struct bkey_s_c k;
 	int ret;
 
@@ -1245,12 +1249,14 @@ int bch2_stripes_read(struct bch_fs *c, struct list_head *journal_replay_list)
 	if (ret)
 		return ret;
 
-	for_each_btree_key(&iter, c, BTREE_ID_EC, POS_MIN, 0, k) {
+	bch2_trans_init(&trans, c);
+
+	for_each_btree_key(&trans, iter, BTREE_ID_EC, POS_MIN, 0, k) {
 		bch2_stripe_read_key(c, k);
-		bch2_btree_iter_cond_resched(&iter);
+		bch2_trans_cond_resched(&trans);
 	}
 
-	ret = bch2_btree_iter_unlock(&iter);
+	ret = bch2_trans_exit(&trans);
 	if (ret)
 		return ret;
 
@@ -1268,17 +1274,20 @@ int bch2_stripes_read(struct bch_fs *c, struct list_head *journal_replay_list)
 
 int bch2_ec_mem_alloc(struct bch_fs *c, bool gc)
 {
-	struct btree_iter iter;
+	struct btree_trans trans;
+	struct btree_iter *iter;
 	struct bkey_s_c k;
 	size_t i, idx = 0;
 	int ret = 0;
 
-	bch2_btree_iter_init(&iter, c, BTREE_ID_EC, POS(0, U64_MAX), 0);
+	bch2_trans_init(&trans, c);
 
-	k = bch2_btree_iter_prev(&iter);
+	iter = bch2_trans_get_iter(&trans, BTREE_ID_EC, POS(0, U64_MAX), 0);
+
+	k = bch2_btree_iter_prev(iter);
 	if (!IS_ERR_OR_NULL(k.k))
 		idx = k.k->p.offset + 1;
-	ret = bch2_btree_iter_unlock(&iter);
+	ret = bch2_trans_exit(&trans);
 	if (ret)
 		return ret;
 
diff --git a/libbcachefs/error.c b/libbcachefs/error.c
index 9505b6e6..e3747781 100644
--- a/libbcachefs/error.c
+++ b/libbcachefs/error.c
@@ -66,10 +66,20 @@ enum fsck_err_ret bch2_fsck_err(struct bch_fs *c, unsigned flags,
 	bool fix = false, print = true, suppressing = false;
 	char _buf[sizeof(s->buf)], *buf = _buf;
 
-	mutex_lock(&c->fsck_error_lock);
+	if (test_bit(BCH_FS_FSCK_DONE, &c->flags)) {
+		va_start(args, fmt);
+		vprintk(fmt, args);
+		va_end(args);
 
-	if (test_bit(BCH_FS_FSCK_DONE, &c->flags))
-		goto print;
+		if (c->opts.errors == BCH_ON_ERROR_CONTINUE &&
+		    flags & FSCK_CAN_FIX)
+			return FSCK_ERR_FIX;
+
+		bch2_inconsistent_error(c);
+		return FSCK_ERR_EXIT;
+	}
+
+	mutex_lock(&c->fsck_error_lock);
 
 	list_for_each_entry(s, &c->fsck_errors, list)
 		if (s->fmt == fmt)
diff --git a/libbcachefs/extents.c b/libbcachefs/extents.c
index 1ab951c9..aa2fc779 100644
--- a/libbcachefs/extents.c
+++ b/libbcachefs/extents.c
@@ -788,7 +788,8 @@ static bool bch2_extent_merge_inline(struct bch_fs *,
 				     struct bkey_packed *,
 				     bool);
 
-static void verify_extent_nonoverlapping(struct btree *b,
+static void verify_extent_nonoverlapping(struct bch_fs *c,
+					 struct btree *b,
 					 struct btree_node_iter *_iter,
 					 struct bkey_i *insert)
 {
@@ -797,6 +798,9 @@ static void verify_extent_nonoverlapping(struct btree *b,
 	struct bkey_packed *k;
 	struct bkey uk;
 
+	if (!expensive_debug_checks(c))
+		return;
+
 	iter = *_iter;
 	k = bch2_btree_node_iter_prev_filter(&iter, b, KEY_TYPE_discard);
 	BUG_ON(k &&
@@ -847,7 +851,7 @@ static void extent_bset_insert(struct bch_fs *c, struct btree_iter *iter,
 	BUG_ON(insert->k.u64s > bch_btree_keys_u64s_remaining(c, l->b));
 
 	EBUG_ON(bkey_deleted(&insert->k) || !insert->k.size);
-	verify_extent_nonoverlapping(l->b, &l->iter, insert);
+	verify_extent_nonoverlapping(c, l->b, &l->iter, insert);
 
 	node_iter = l->iter;
 	k = bch2_btree_node_iter_prev_filter(&node_iter, l->b, KEY_TYPE_discard);
@@ -1618,15 +1622,18 @@ static bool bch2_extent_merge_inline(struct bch_fs *c,
 bool bch2_check_range_allocated(struct bch_fs *c, struct bpos pos, u64 size,
 			       unsigned nr_replicas)
 {
-	struct btree_iter iter;
+	struct btree_trans trans;
+	struct btree_iter *iter;
 	struct bpos end = pos;
 	struct bkey_s_c k;
 	bool ret = true;
 
 	end.offset += size;
 
-	for_each_btree_key(&iter, c, BTREE_ID_EXTENTS, pos,
-			     BTREE_ITER_SLOTS, k) {
+	bch2_trans_init(&trans, c);
+
+	for_each_btree_key(&trans, iter, BTREE_ID_EXTENTS, pos,
+			   BTREE_ITER_SLOTS, k) {
 		if (bkey_cmp(bkey_start_pos(k.k), end) >= 0)
 			break;
 
@@ -1635,7 +1642,7 @@ bool bch2_check_range_allocated(struct bch_fs *c, struct bpos pos, u64 size,
 			break;
 		}
 	}
-	bch2_btree_iter_unlock(&iter);
+	bch2_trans_exit(&trans);
 
 	return ret;
 }
diff --git a/libbcachefs/fs-io.c b/libbcachefs/fs-io.c
index d3a03641..ef658ad0 100644
--- a/libbcachefs/fs-io.c
+++ b/libbcachefs/fs-io.c
@@ -251,7 +251,7 @@ static int sum_sector_overwrites(struct btree_trans *trans,
 		 * carefully not advancing past @new and thus whatever leaf node
 		 * @_iter currently points to:
 		 */
-		BUG_ON(btree_iter_err(old));
+		BUG_ON(bkey_err(old));
 
 		if (allocating &&
 		    !*allocating &&
@@ -322,10 +322,10 @@ static int bch2_extent_update(struct btree_trans *trans,
 	if (i_sectors_delta ||
 	    new_i_size > inode->ei_inode.bi_size) {
 		if (c->opts.new_inode_updates) {
-			bch2_btree_iter_unlock(extent_iter);
+			bch2_btree_trans_unlock(trans);
 			mutex_lock(&inode->ei_update_lock);
 
-			if (!bch2_btree_iter_relock(extent_iter)) {
+			if (!bch2_btree_trans_relock(trans)) {
 				mutex_unlock(&inode->ei_update_lock);
 				return -EINTR;
 			}
@@ -967,10 +967,11 @@ static void readpage_bio_extend(struct readpages_iter *iter,
 	}
 }
 
-static void bchfs_read(struct bch_fs *c, struct btree_iter *iter,
+static void bchfs_read(struct btree_trans *trans, struct btree_iter *iter,
 		       struct bch_read_bio *rbio, u64 inum,
 		       struct readpages_iter *readpages_iter)
 {
+	struct bch_fs *c = trans->c;
 	struct bio *bio = &rbio->bio;
 	int flags = BCH_READ_RETRY_IF_STALE|
 		BCH_READ_MAY_PROMOTE;
@@ -989,7 +990,7 @@ static void bchfs_read(struct bch_fs *c, struct btree_iter *iter,
 		BUG_ON(!k.k);
 
 		if (IS_ERR(k.k)) {
-			int ret = bch2_btree_iter_unlock(iter);
+			int ret = btree_iter_err(iter);
 			BUG_ON(!ret);
 			bcache_io_error(c, bio, "btree IO error %i", ret);
 			bio_endio(bio);
@@ -997,7 +998,7 @@ static void bchfs_read(struct bch_fs *c, struct btree_iter *iter,
 		}
 
 		bkey_reassemble(&tmp.k, k);
-		bch2_btree_iter_unlock(iter);
+		bch2_btree_trans_unlock(trans);
 		k = bkey_i_to_s_c(&tmp.k);
 
 		if (readpages_iter) {
@@ -1044,7 +1045,8 @@ int bch2_readpages(struct file *file, struct address_space *mapping,
 	struct bch_inode_info *inode = to_bch_ei(mapping->host);
 	struct bch_fs *c = inode->v.i_sb->s_fs_info;
 	struct bch_io_opts opts = io_opts(c, inode);
-	struct btree_iter iter;
+	struct btree_trans trans;
+	struct btree_iter *iter;
 	struct page *page;
 	struct readpages_iter readpages_iter;
 	int ret;
@@ -1052,8 +1054,10 @@ int bch2_readpages(struct file *file, struct address_space *mapping,
 	ret = readpages_iter_init(&readpages_iter, mapping, pages, nr_pages);
 	BUG_ON(ret);
 
-	bch2_btree_iter_init(&iter, c, BTREE_ID_EXTENTS, POS_MIN,
-			     BTREE_ITER_SLOTS);
+	bch2_trans_init(&trans, c);
+
+	iter = bch2_trans_get_iter(&trans, BTREE_ID_EXTENTS, POS_MIN,
+				   BTREE_ITER_SLOTS);
 
 	if (current->pagecache_lock != &mapping->add_lock)
 		pagecache_add_get(&mapping->add_lock);
@@ -1075,12 +1079,14 @@ int bch2_readpages(struct file *file, struct address_space *mapping,
 		rbio->bio.bi_end_io = bch2_readpages_end_io;
 		__bio_add_page(&rbio->bio, page, PAGE_SIZE, 0);
 
-		bchfs_read(c, &iter, rbio, inode->v.i_ino, &readpages_iter);
+		bchfs_read(&trans, iter, rbio, inode->v.i_ino,
+			   &readpages_iter);
 	}
 
 	if (current->pagecache_lock != &mapping->add_lock)
 		pagecache_add_put(&mapping->add_lock);
 
+	bch2_trans_exit(&trans);
 	kfree(readpages_iter.pages);
 
 	return 0;
@@ -1089,16 +1095,21 @@ int bch2_readpages(struct file *file, struct address_space *mapping,
 static void __bchfs_readpage(struct bch_fs *c, struct bch_read_bio *rbio,
 			     u64 inum, struct page *page)
 {
-	struct btree_iter iter;
+	struct btree_trans trans;
+	struct btree_iter *iter;
 
 	page_state_init_for_read(page);
 
 	bio_set_op_attrs(&rbio->bio, REQ_OP_READ, REQ_SYNC);
 	bio_add_page_contig(&rbio->bio, page);
 
-	bch2_btree_iter_init(&iter, c, BTREE_ID_EXTENTS, POS_MIN,
-			     BTREE_ITER_SLOTS);
-	bchfs_read(c, &iter, rbio, inum, NULL);
+	bch2_trans_init(&trans, c);
+	iter = bch2_trans_get_iter(&trans, BTREE_ID_EXTENTS, POS_MIN,
+				   BTREE_ITER_SLOTS);
+
+	bchfs_read(&trans, iter, rbio, inum, NULL);
+
+	bch2_trans_exit(&trans);
 }
 
 int bch2_readpage(struct file *file, struct page *page)
@@ -2097,7 +2108,7 @@ static int __bch2_fpunch(struct bch_fs *c, struct bch_inode_info *inode,
 				   BTREE_ITER_INTENT);
 
 	while ((k = bch2_btree_iter_peek(iter)).k &&
-	       !(ret = btree_iter_err(k)) &&
+	       !(ret = bkey_err(k)) &&
 	       bkey_cmp(iter->pos, end) < 0) {
 		struct disk_reservation disk_res =
 			bch2_disk_reservation_init(c, 0);
@@ -2120,7 +2131,7 @@ static int __bch2_fpunch(struct bch_fs *c, struct bch_inode_info *inode,
 		if (ret)
 			break;
 
-		bch2_btree_iter_cond_resched(iter);
+		bch2_trans_cond_resched(&trans);
 	}
 
 	bch2_trans_exit(&trans);
@@ -2132,13 +2143,14 @@ static inline int range_has_data(struct bch_fs *c,
 				  struct bpos start,
 				  struct bpos end)
 {
-
-	struct btree_iter iter;
+	struct btree_trans trans;
+	struct btree_iter *iter;
 	struct bkey_s_c k;
 	int ret = 0;
 
-	for_each_btree_key(&iter, c, BTREE_ID_EXTENTS,
-			   start, 0, k) {
+	bch2_trans_init(&trans, c);
+
+	for_each_btree_key(&trans, iter, BTREE_ID_EXTENTS, start, 0, k) {
 		if (bkey_cmp(bkey_start_pos(k.k), end) >= 0)
 			break;
 
@@ -2148,7 +2160,7 @@ static inline int range_has_data(struct bch_fs *c,
 		}
 	}
 
-	return bch2_btree_iter_unlock(&iter) ?: ret;
+	return bch2_trans_exit(&trans) ?: ret;
 }
 
 static int __bch2_truncate_page(struct bch_inode_info *inode,
@@ -2434,14 +2446,14 @@ static long bch2_fcollapse(struct bch_inode_info *inode,
 
 		ret = bch2_btree_iter_traverse(dst);
 		if (ret)
-			goto btree_iter_err;
+			goto bkey_err;
 
 		bch2_btree_iter_set_pos(src,
 			POS(dst->pos.inode, dst->pos.offset + (len >> 9)));
 
 		k = bch2_btree_iter_peek_slot(src);
-		if ((ret = btree_iter_err(k)))
-			goto btree_iter_err;
+		if ((ret = bkey_err(k)))
+			goto bkey_err;
 
 		bkey_reassemble(&copy.k, k);
 
@@ -2462,7 +2474,7 @@ static long bch2_fcollapse(struct bch_inode_info *inode,
 				dst, &copy.k,
 				0, true, true, NULL);
 		bch2_disk_reservation_put(c, &disk_res);
-btree_iter_err:
+bkey_err:
 		if (ret == -EINTR)
 			ret = 0;
 		if (ret)
@@ -2472,7 +2484,7 @@ btree_iter_err:
 		 * pointers... which isn't a _super_ serious problem...
 		 */
 
-		bch2_btree_iter_cond_resched(src);
+		bch2_trans_cond_resched(&trans);
 	}
 	bch2_trans_unlock(&trans);
 
@@ -2556,8 +2568,8 @@ static long bch2_fallocate(struct bch_inode_info *inode, int mode,
 		struct bkey_s_c k;
 
 		k = bch2_btree_iter_peek_slot(iter);
-		if ((ret = btree_iter_err(k)))
-			goto btree_iter_err;
+		if ((ret = bkey_err(k)))
+			goto bkey_err;
 
 		/* already reserved */
 		if (k.k->type == KEY_TYPE_reservation &&
@@ -2588,7 +2600,7 @@ static long bch2_fallocate(struct bch_inode_info *inode, int mode,
 					&quota_res,
 					sectors, true);
 			if (unlikely(ret))
-				goto btree_iter_err;
+				goto bkey_err;
 		}
 
 		if (reservation.v.nr_replicas < replicas ||
@@ -2596,7 +2608,7 @@ static long bch2_fallocate(struct bch_inode_info *inode, int mode,
 			ret = bch2_disk_reservation_get(c, &disk_res, sectors,
 							replicas, 0);
 			if (unlikely(ret))
-				goto btree_iter_err;
+				goto bkey_err;
 
 			reservation.v.nr_replicas = disk_res.nr_replicas;
 		}
@@ -2605,7 +2617,7 @@ static long bch2_fallocate(struct bch_inode_info *inode, int mode,
 				&disk_res, &quota_res,
 				iter, &reservation.k_i,
 				0, true, true, NULL);
-btree_iter_err:
+bkey_err:
 		bch2_quota_reservation_put(c, inode, &quota_res);
 		bch2_disk_reservation_put(c, &disk_res);
 		if (ret == -EINTR)
@@ -2710,7 +2722,8 @@ static loff_t bch2_seek_data(struct file *file, u64 offset)
 {
 	struct bch_inode_info *inode = file_bch_inode(file);
 	struct bch_fs *c = inode->v.i_sb->s_fs_info;
-	struct btree_iter iter;
+	struct btree_trans trans;
+	struct btree_iter *iter;
 	struct bkey_s_c k;
 	u64 isize, next_data = MAX_LFS_FILESIZE;
 	int ret;
@@ -2719,7 +2732,9 @@ static loff_t bch2_seek_data(struct file *file, u64 offset)
 	if (offset >= isize)
 		return -ENXIO;
 
-	for_each_btree_key(&iter, c, BTREE_ID_EXTENTS,
+	bch2_trans_init(&trans, c);
+
+	for_each_btree_key(&trans, iter, BTREE_ID_EXTENTS,
 			   POS(inode->v.i_ino, offset >> 9), 0, k) {
 		if (k.k->p.inode != inode->v.i_ino) {
 			break;
@@ -2730,7 +2745,7 @@ static loff_t bch2_seek_data(struct file *file, u64 offset)
 			break;
 	}
 
-	ret = bch2_btree_iter_unlock(&iter);
+	ret = bch2_trans_exit(&trans);
 	if (ret)
 		return ret;
 
@@ -2780,7 +2795,8 @@ static loff_t bch2_seek_hole(struct file *file, u64 offset)
 {
 	struct bch_inode_info *inode = file_bch_inode(file);
 	struct bch_fs *c = inode->v.i_sb->s_fs_info;
-	struct btree_iter iter;
+	struct btree_trans trans;
+	struct btree_iter *iter;
 	struct bkey_s_c k;
 	u64 isize, next_hole = MAX_LFS_FILESIZE;
 	int ret;
@@ -2789,7 +2805,9 @@ static loff_t bch2_seek_hole(struct file *file, u64 offset)
 	if (offset >= isize)
 		return -ENXIO;
 
-	for_each_btree_key(&iter, c, BTREE_ID_EXTENTS,
+	bch2_trans_init(&trans, c);
+
+	for_each_btree_key(&trans, iter, BTREE_ID_EXTENTS,
 			   POS(inode->v.i_ino, offset >> 9),
 			   BTREE_ITER_SLOTS, k) {
 		if (k.k->p.inode != inode->v.i_ino) {
@@ -2808,7 +2826,7 @@ static loff_t bch2_seek_hole(struct file *file, u64 offset)
 		}
 	}
 
-	ret = bch2_btree_iter_unlock(&iter);
+	ret = bch2_trans_exit(&trans);
 	if (ret)
 		return ret;
 
diff --git a/libbcachefs/fs.c b/libbcachefs/fs.c
index f0560675..cc91af0a 100644
--- a/libbcachefs/fs.c
+++ b/libbcachefs/fs.c
@@ -106,7 +106,7 @@ int __must_check bch2_write_inode_trans(struct btree_trans *trans,
 				void *p)
 {
 	struct bch_fs *c = trans->c;
-	struct btree_iter *iter;
+	struct btree_iter *iter = NULL;
 	struct bkey_inode_buf *inode_p;
 	int ret;
 
@@ -1113,7 +1113,8 @@ static int bch2_fiemap(struct inode *vinode, struct fiemap_extent_info *info,
 {
 	struct bch_fs *c = vinode->i_sb->s_fs_info;
 	struct bch_inode_info *ei = to_bch_ei(vinode);
-	struct btree_iter iter;
+	struct btree_trans trans;
+	struct btree_iter *iter;
 	struct bkey_s_c k;
 	BKEY_PADDED(k) tmp;
 	bool have_extent = false;
@@ -1122,7 +1123,9 @@ static int bch2_fiemap(struct inode *vinode, struct fiemap_extent_info *info,
 	if (start + len < start)
 		return -EINVAL;
 
-	for_each_btree_key(&iter, c, BTREE_ID_EXTENTS,
+	bch2_trans_init(&trans, c);
+
+	for_each_btree_key(&trans, iter, BTREE_ID_EXTENTS,
 			   POS(ei->v.i_ino, start >> 9), 0, k)
 		if (bkey_extent_is_data(k.k) ||
 		    k.k->type == KEY_TYPE_reservation) {
@@ -1143,7 +1146,7 @@ static int bch2_fiemap(struct inode *vinode, struct fiemap_extent_info *info,
 	if (have_extent)
 		ret = bch2_fill_extent(info, &tmp.k, FIEMAP_EXTENT_LAST);
 out:
-	bch2_btree_iter_unlock(&iter);
+	bch2_trans_exit(&trans);
 	return ret < 0 ? ret : 0;
 }
 
diff --git a/libbcachefs/fsck.c b/libbcachefs/fsck.c
index fb0cb9a4..5c2329d9 100644
--- a/libbcachefs/fsck.c
+++ b/libbcachefs/fsck.c
@@ -15,9 +15,27 @@
 
 #define QSTR(n) { { { .len = strlen(n) } }, .name = n }
 
-static int remove_dirent(struct bch_fs *c, struct btree_iter *iter,
+static s64 bch2_count_inode_sectors(struct btree_trans *trans, u64 inum)
+{
+	struct btree_iter *iter;
+	struct bkey_s_c k;
+	u64 sectors = 0;
+
+	for_each_btree_key(trans, iter, BTREE_ID_EXTENTS, POS(inum, 0), 0, k) {
+		if (k.k->p.inode != inum)
+			break;
+
+		if (bkey_extent_is_allocation(k.k))
+			sectors += k.k->size;
+	}
+
+	return bch2_trans_iter_free(trans, iter) ?: sectors;
+}
+
+static int remove_dirent(struct btree_trans *trans,
 			 struct bkey_s_c_dirent dirent)
 {
+	struct bch_fs *c = trans->c;
 	struct qstr name;
 	struct bch_inode_unpacked dir_inode;
 	struct bch_hash_info dir_hash_info;
@@ -34,8 +52,8 @@ static int remove_dirent(struct bch_fs *c, struct btree_iter *iter,
 	buf[name.len] = '\0';
 	name.name = buf;
 
-	/* Unlock iter so we don't deadlock, after copying name: */
-	bch2_btree_iter_unlock(iter);
+	/* Unlock so we don't deadlock, after copying name: */
+	bch2_btree_trans_unlock(trans);
 
 	ret = bch2_inode_find_by_inum(c, dir_inum, &dir_inode);
 	if (ret) {
@@ -125,29 +143,33 @@ static int walk_inode(struct bch_fs *c, struct inode_walker *w, u64 inum)
 
 struct hash_check {
 	struct bch_hash_info	info;
-	struct btree_trans	*trans;
 
 	/* start of current chain of hash collisions: */
 	struct btree_iter	*chain;
 
 	/* next offset in current chain of hash collisions: */
-	u64			next;
+	u64			chain_end;
 };
 
-static void hash_check_init(const struct bch_hash_desc desc,
-			    struct btree_trans *trans,
-			    struct hash_check *h)
+static void hash_check_init(struct hash_check *h)
 {
-	h->trans = trans;
-	h->chain = bch2_trans_get_iter(trans, desc.btree_id, POS_MIN, 0);
-	h->next = -1;
+	h->chain = NULL;
 }
 
-static void hash_check_set_inode(struct hash_check *h, struct bch_fs *c,
+static void hash_stop_chain(struct btree_trans *trans,
+			    struct hash_check *h)
+{
+	if (h->chain)
+		bch2_trans_iter_free(trans, h->chain);
+	h->chain = NULL;
+}
+
+static void hash_check_set_inode(struct btree_trans *trans,
+				 struct hash_check *h,
 				 const struct bch_inode_unpacked *bi)
 {
-	h->info = bch2_hash_info_init(c, bi);
-	h->next = -1;
+	h->info = bch2_hash_info_init(trans->c, bi);
+	hash_stop_chain(trans, h);
 }
 
 static int hash_redo_key(const struct bch_hash_desc desc,
@@ -168,8 +190,6 @@ static int hash_redo_key(const struct bch_hash_desc desc,
 	if (ret)
 		goto err;
 
-	bch2_btree_iter_unlock(k_iter);
-
 	bch2_hash_set(trans, desc, &h->info, k_iter->pos.inode,
 		      tmp, BCH_HASH_SET_MUST_CREATE);
 	ret = bch2_trans_commit(trans, NULL, NULL,
@@ -180,44 +200,32 @@ err:
 	return ret;
 }
 
-/* fsck hasn't been converted to new transactions yet: */
-static int fsck_hash_delete_at(const struct bch_hash_desc desc,
+static int fsck_hash_delete_at(struct btree_trans *trans,
+			       const struct bch_hash_desc desc,
 			       struct bch_hash_info *info,
-			       struct btree_iter *orig_iter)
+			       struct btree_iter *iter)
 {
-	struct btree_trans trans;
-	struct btree_iter *iter;
 	int ret;
-
-	bch2_btree_iter_unlock(orig_iter);
-
-	bch2_trans_init(&trans, orig_iter->c);
 retry:
-	bch2_trans_begin(&trans);
-
-	iter = bch2_trans_copy_iter(&trans, orig_iter);
-	if (IS_ERR(iter)) {
-		ret = PTR_ERR(iter);
-		goto err;
-	}
-
-	ret   = bch2_hash_delete_at(&trans, desc, info, iter) ?:
-		bch2_trans_commit(&trans, NULL, NULL,
+	ret   = bch2_hash_delete_at(trans, desc, info, iter) ?:
+		bch2_trans_commit(trans, NULL, NULL,
 				  BTREE_INSERT_ATOMIC|
 				  BTREE_INSERT_NOFAIL|
 				  BTREE_INSERT_LAZY_RW);
-err:
-	if (ret == -EINTR)
-		goto retry;
+	if (ret == -EINTR) {
+		ret = bch2_btree_iter_traverse(iter);
+		if (!ret)
+			goto retry;
+	}
 
-	bch2_trans_exit(&trans);
 	return ret;
 }
 
-static int hash_check_duplicates(const struct bch_hash_desc desc,
-				 struct hash_check *h, struct bch_fs *c,
-				 struct btree_iter *k_iter, struct bkey_s_c k)
+static int hash_check_duplicates(struct btree_trans *trans,
+			const struct bch_hash_desc desc, struct hash_check *h,
+			struct btree_iter *k_iter, struct bkey_s_c k)
 {
+	struct bch_fs *c = trans->c;
 	struct btree_iter *iter;
 	struct bkey_s_c k2;
 	char buf[200];
@@ -226,7 +234,7 @@ static int hash_check_duplicates(const struct bch_hash_desc desc,
 	if (!bkey_cmp(h->chain->pos, k_iter->pos))
 		return 0;
 
-	iter = bch2_trans_copy_iter(h->trans, h->chain);
+	iter = bch2_trans_copy_iter(trans, h->chain);
 	BUG_ON(IS_ERR(iter));
 
 	for_each_btree_key_continue(iter, 0, k2) {
@@ -238,7 +246,7 @@ static int hash_check_duplicates(const struct bch_hash_desc desc,
 				"duplicate hash table keys:\n%s",
 				(bch2_bkey_val_to_text(&PBUF(buf), c,
 						       k), buf))) {
-			ret = fsck_hash_delete_at(desc, &h->info, k_iter);
+			ret = fsck_hash_delete_at(trans, desc, &h->info, k_iter);
 			if (ret)
 				return ret;
 			ret = 1;
@@ -246,23 +254,39 @@ static int hash_check_duplicates(const struct bch_hash_desc desc,
 		}
 	}
 fsck_err:
-	bch2_trans_iter_free(h->trans, iter);
+	bch2_trans_iter_free(trans, iter);
 	return ret;
 }
 
-static bool key_has_correct_hash(const struct bch_hash_desc desc,
-				 struct hash_check *h, struct bch_fs *c,
-				 struct btree_iter *k_iter, struct bkey_s_c k)
+static void hash_set_chain_start(struct btree_trans *trans,
+			const struct bch_hash_desc desc,
+			struct hash_check *h,
+			struct btree_iter *k_iter, struct bkey_s_c k)
+{
+	bool hole = (k.k->type != KEY_TYPE_whiteout &&
+		     k.k->type != desc.key_type);
+
+	if (hole || k.k->p.offset > h->chain_end + 1)
+		hash_stop_chain(trans, h);
+
+	if (!hole) {
+		if (!h->chain) {
+			h->chain = bch2_trans_copy_iter(trans, k_iter);
+			BUG_ON(IS_ERR(h->chain));
+		}
+
+		h->chain_end = k.k->p.offset;
+	}
+}
+
+static bool key_has_correct_hash(struct btree_trans *trans,
+			const struct bch_hash_desc desc,
+			struct hash_check *h,
+			struct btree_iter *k_iter, struct bkey_s_c k)
 {
 	u64 hash;
 
-	if (k.k->type != KEY_TYPE_whiteout &&
-	    k.k->type != desc.key_type)
-		return true;
-
-	if (k.k->p.offset != h->next)
-		bch2_btree_iter_copy(h->chain, k_iter);
-	h->next = k.k->p.offset + 1;
+	hash_set_chain_start(trans, desc, h, k_iter, k);
 
 	if (k.k->type != desc.key_type)
 		return true;
@@ -273,22 +297,16 @@ static bool key_has_correct_hash(const struct bch_hash_desc desc,
 		hash <= k.k->p.offset;
 }
 
-static int hash_check_key(const struct bch_hash_desc desc,
-			  struct btree_trans *trans, struct hash_check *h,
-			  struct btree_iter *k_iter, struct bkey_s_c k)
+static int hash_check_key(struct btree_trans *trans,
+			const struct bch_hash_desc desc, struct hash_check *h,
+			struct btree_iter *k_iter, struct bkey_s_c k)
 {
 	struct bch_fs *c = trans->c;
 	char buf[200];
 	u64 hashed;
 	int ret = 0;
 
-	if (k.k->type != KEY_TYPE_whiteout &&
-	    k.k->type != desc.key_type)
-		return 0;
-
-	if (k.k->p.offset != h->next)
-		bch2_btree_iter_copy(h->chain, k_iter);
-	h->next = k.k->p.offset + 1;
+	hash_set_chain_start(trans, desc, h, k_iter, k);
 
 	if (k.k->type != desc.key_type)
 		return 0;
@@ -311,7 +329,7 @@ static int hash_check_key(const struct bch_hash_desc desc,
 		return 1;
 	}
 
-	ret = hash_check_duplicates(desc, h, c, k_iter, k);
+	ret = hash_check_duplicates(trans, desc, h, k_iter, k);
 fsck_err:
 	return ret;
 }
@@ -326,7 +344,7 @@ static int check_dirent_hash(struct btree_trans *trans, struct hash_check *h,
 	unsigned len;
 	u64 hash;
 
-	if (key_has_correct_hash(bch2_dirent_hash_desc, h, c, iter, *k))
+	if (key_has_correct_hash(trans, bch2_dirent_hash_desc, h, iter, *k))
 		return 0;
 
 	len = bch2_dirent_name_bytes(bkey_s_c_to_dirent(*k));
@@ -416,14 +434,17 @@ noinline_for_stack
 static int check_extents(struct bch_fs *c)
 {
 	struct inode_walker w = inode_walker_init();
-	struct btree_iter iter;
+	struct btree_trans trans;
+	struct btree_iter *iter;
 	struct bkey_s_c k;
 	u64 i_sectors;
 	int ret = 0;
 
+	bch2_trans_init(&trans, c);
+
 	bch_verbose(c, "checking extents");
 
-	for_each_btree_key(&iter, c, BTREE_ID_EXTENTS,
+	for_each_btree_key(&trans, iter, BTREE_ID_EXTENTS,
 			   POS(BCACHEFS_ROOT_INO, 0), 0, k) {
 		ret = walk_inode(c, &w, k.k->p.inode);
 		if (ret)
@@ -436,7 +457,7 @@ static int check_extents(struct bch_fs *c)
 			!S_ISREG(w.inode.bi_mode) && !S_ISLNK(w.inode.bi_mode), c,
 			"extent type %u for non regular file, inode %llu mode %o",
 			k.k->type, k.k->p.inode, w.inode.bi_mode)) {
-			bch2_btree_iter_unlock(&iter);
+			bch2_trans_unlock(&trans);
 
 			ret = bch2_inode_truncate(c, k.k->p.inode, 0);
 			if (ret)
@@ -448,14 +469,14 @@ static int check_extents(struct bch_fs *c)
 			w.have_inode &&
 			!(w.inode.bi_flags & BCH_INODE_I_SECTORS_DIRTY) &&
 			w.inode.bi_sectors !=
-			(i_sectors = bch2_count_inode_sectors(c, w.cur_inum)),
+			(i_sectors = bch2_count_inode_sectors(&trans, w.cur_inum)),
 			c, "i_sectors wrong: got %llu, should be %llu",
 			w.inode.bi_sectors, i_sectors)) {
 			struct bkey_inode_buf p;
 
 			w.inode.bi_sectors = i_sectors;
 
-			bch2_btree_iter_unlock(&iter);
+			bch2_trans_unlock(&trans);
 
 			bch2_inode_pack(&p, &w.inode);
 
@@ -469,7 +490,7 @@ static int check_extents(struct bch_fs *c)
 			}
 
 			/* revalidate iterator: */
-			k = bch2_btree_iter_peek(&iter);
+			k = bch2_btree_iter_peek(iter);
 		}
 
 		if (fsck_err_on(w.have_inode &&
@@ -478,7 +499,7 @@ static int check_extents(struct bch_fs *c)
 			k.k->p.offset > round_up(w.inode.bi_size, PAGE_SIZE) >> 9, c,
 			"extent type %u offset %llu past end of inode %llu, i_size %llu",
 			k.k->type, k.k->p.offset, k.k->p.inode, w.inode.bi_size)) {
-			bch2_btree_iter_unlock(&iter);
+			bch2_trans_unlock(&trans);
 
 			ret = bch2_inode_truncate(c, k.k->p.inode,
 						  w.inode.bi_size);
@@ -489,7 +510,7 @@ static int check_extents(struct bch_fs *c)
 	}
 err:
 fsck_err:
-	return bch2_btree_iter_unlock(&iter) ?: ret;
+	return bch2_trans_exit(&trans) ?: ret;
 }
 
 /*
@@ -517,7 +538,7 @@ static int check_dirents(struct bch_fs *c)
 	iter = bch2_trans_get_iter(&trans, BTREE_ID_DIRENTS,
 				   POS(BCACHEFS_ROOT_INO, 0), 0);
 
-	hash_check_init(bch2_dirent_hash_desc, &trans, &h);
+	hash_check_init(&h);
 
 	for_each_btree_key_continue(iter, 0, k) {
 		struct bkey_s_c_dirent d;
@@ -545,7 +566,7 @@ static int check_dirents(struct bch_fs *c)
 		}
 
 		if (w.first_this_inode && w.have_inode)
-			hash_check_set_inode(&h, c, &w.inode);
+			hash_check_set_inode(&trans, &h, &w.inode);
 
 		ret = check_dirent_hash(&trans, &h, iter, &k);
 		if (ret > 0) {
@@ -578,7 +599,7 @@ static int check_dirents(struct bch_fs *c)
 				".. dirent") ||
 		    fsck_err_on(memchr(d.v->d_name, '/', name_len), c,
 				"dirent name has invalid chars")) {
-			ret = remove_dirent(c, iter, d);
+			ret = remove_dirent(&trans, d);
 			if (ret)
 				goto err;
 			continue;
@@ -588,7 +609,7 @@ static int check_dirents(struct bch_fs *c)
 				"dirent points to own directory:\n%s",
 				(bch2_bkey_val_to_text(&PBUF(buf), c,
 						       k), buf))) {
-			ret = remove_dirent(c, iter, d);
+			ret = remove_dirent(&trans, d);
 			if (ret)
 				goto err;
 			continue;
@@ -605,7 +626,7 @@ static int check_dirents(struct bch_fs *c)
 				"dirent points to missing inode:\n%s",
 				(bch2_bkey_val_to_text(&PBUF(buf), c,
 						       k), buf))) {
-			ret = remove_dirent(c, iter, d);
+			ret = remove_dirent(&trans, d);
 			if (ret)
 				goto err;
 			continue;
@@ -641,6 +662,8 @@ static int check_dirents(struct bch_fs *c)
 
 		}
 	}
+
+	hash_stop_chain(&trans, &h);
 err:
 fsck_err:
 	return bch2_trans_exit(&trans) ?: ret;
@@ -668,7 +691,7 @@ static int check_xattrs(struct bch_fs *c)
 	iter = bch2_trans_get_iter(&trans, BTREE_ID_XATTRS,
 				   POS(BCACHEFS_ROOT_INO, 0), 0);
 
-	hash_check_init(bch2_xattr_hash_desc, &trans, &h);
+	hash_check_init(&h);
 
 	for_each_btree_key_continue(iter, 0, k) {
 		ret = walk_inode(c, &w, k.k->p.inode);
@@ -685,9 +708,10 @@ static int check_xattrs(struct bch_fs *c)
 		}
 
 		if (w.first_this_inode && w.have_inode)
-			hash_check_set_inode(&h, c, &w.inode);
+			hash_check_set_inode(&trans, &h, &w.inode);
 
-		ret = hash_check_key(bch2_xattr_hash_desc, &trans, &h, iter, k);
+		ret = hash_check_key(&trans, bch2_xattr_hash_desc,
+				     &h, iter, k);
 		if (ret)
 			goto fsck_err;
 	}
@@ -862,13 +886,16 @@ static int check_directory_structure(struct bch_fs *c,
 	struct inode_bitmap dirs_done = { NULL, 0 };
 	struct pathbuf path = { 0, 0, NULL };
 	struct pathbuf_entry *e;
-	struct btree_iter iter;
+	struct btree_trans trans;
+	struct btree_iter *iter;
 	struct bkey_s_c k;
 	struct bkey_s_c_dirent dirent;
 	bool had_unreachable;
 	u64 d_inum;
 	int ret = 0;
 
+	bch2_trans_init(&trans, c);
+
 	bch_verbose(c, "checking directory structure");
 
 	/* DFS: */
@@ -893,7 +920,7 @@ next:
 		if (e->offset == U64_MAX)
 			goto up;
 
-		for_each_btree_key(&iter, c, BTREE_ID_DIRENTS,
+		for_each_btree_key(&trans, iter, BTREE_ID_DIRENTS,
 				   POS(e->inum, e->offset + 1), 0, k) {
 			if (k.k->p.inode != e->inum)
 				break;
@@ -913,7 +940,7 @@ next:
 			if (fsck_err_on(inode_bitmap_test(&dirs_done, d_inum), c,
 					"directory %llu has multiple hardlinks",
 					d_inum)) {
-				ret = remove_dirent(c, &iter, dirent);
+				ret = remove_dirent(&trans, dirent);
 				if (ret)
 					goto err;
 				continue;
@@ -930,10 +957,14 @@ next:
 				goto err;
 			}
 
-			bch2_btree_iter_unlock(&iter);
+			ret = bch2_trans_iter_free(&trans, iter);
+			if (ret) {
+				bch_err(c, "btree error %i in fsck", ret);
+				goto err;
+			}
 			goto next;
 		}
-		ret = bch2_btree_iter_unlock(&iter);
+		ret = bch2_trans_iter_free(&trans, iter);
 		if (ret) {
 			bch_err(c, "btree error %i in fsck", ret);
 			goto err;
@@ -942,7 +973,7 @@ up:
 		path.nr--;
 	}
 
-	for_each_btree_key(&iter, c, BTREE_ID_INODES, POS_MIN, 0, k) {
+	for_each_btree_key(&trans, iter, BTREE_ID_INODES, POS_MIN, 0, k) {
 		if (k.k->type != KEY_TYPE_inode)
 			continue;
 
@@ -955,7 +986,7 @@ up:
 		if (fsck_err_on(!inode_bitmap_test(&dirs_done, k.k->p.inode), c,
 				"unreachable directory found (inum %llu)",
 				k.k->p.inode)) {
-			bch2_btree_iter_unlock(&iter);
+			bch2_btree_trans_unlock(&trans);
 
 			ret = reattach_inode(c, lostfound_inode, k.k->p.inode);
 			if (ret) {
@@ -965,7 +996,7 @@ up:
 			had_unreachable = true;
 		}
 	}
-	ret = bch2_btree_iter_unlock(&iter);
+	ret = bch2_trans_iter_free(&trans, iter);
 	if (ret)
 		goto err;
 
@@ -984,7 +1015,7 @@ out:
 	return ret;
 err:
 fsck_err:
-	ret = bch2_btree_iter_unlock(&iter) ?: ret;
+	ret = bch2_trans_exit(&trans) ?: ret;
 	goto out;
 }
 
@@ -1021,15 +1052,18 @@ noinline_for_stack
 static int bch2_gc_walk_dirents(struct bch_fs *c, nlink_table *links,
 			       u64 range_start, u64 *range_end)
 {
-	struct btree_iter iter;
+	struct btree_trans trans;
+	struct btree_iter *iter;
 	struct bkey_s_c k;
 	struct bkey_s_c_dirent d;
 	u64 d_inum;
 	int ret;
 
+	bch2_trans_init(&trans, c);
+
 	inc_link(c, links, range_start, range_end, BCACHEFS_ROOT_INO, false);
 
-	for_each_btree_key(&iter, c, BTREE_ID_DIRENTS, POS_MIN, 0, k) {
+	for_each_btree_key(&trans, iter, BTREE_ID_DIRENTS, POS_MIN, 0, k) {
 		switch (k.k->type) {
 		case KEY_TYPE_dirent:
 			d = bkey_s_c_to_dirent(k);
@@ -1045,32 +1079,15 @@ static int bch2_gc_walk_dirents(struct bch_fs *c, nlink_table *links,
 			break;
 		}
 
-		bch2_btree_iter_cond_resched(&iter);
+		bch2_trans_cond_resched(&trans);
 	}
-	ret = bch2_btree_iter_unlock(&iter);
+	ret = bch2_trans_exit(&trans);
 	if (ret)
 		bch_err(c, "error in fs gc: btree error %i while walking dirents", ret);
 
 	return ret;
 }
 
-s64 bch2_count_inode_sectors(struct bch_fs *c, u64 inum)
-{
-	struct btree_iter iter;
-	struct bkey_s_c k;
-	u64 sectors = 0;
-
-	for_each_btree_key(&iter, c, BTREE_ID_EXTENTS, POS(inum, 0), 0, k) {
-		if (k.k->p.inode != inum)
-			break;
-
-		if (bkey_extent_is_allocation(k.k))
-			sectors += k.k->size;
-	}
-
-	return bch2_btree_iter_unlock(&iter) ?: sectors;
-}
-
 static int check_inode_nlink(struct bch_fs *c,
 			     struct bch_inode_unpacked *lostfound_inode,
 			     struct bch_inode_unpacked *u,
@@ -1184,6 +1201,9 @@ static int check_inode(struct btree_trans *trans,
 	int ret = 0;
 
 	ret = bch2_inode_unpack(inode, &u);
+
+	bch2_btree_trans_unlock(trans);
+
 	if (bch2_fs_inconsistent_on(ret, c,
 			 "error unpacking inode %llu in fsck",
 			 inode.k->p.inode))
@@ -1252,7 +1272,7 @@ static int check_inode(struct btree_trans *trans,
 		bch_verbose(c, "recounting sectors for inode %llu",
 			    u.bi_inum);
 
-		sectors = bch2_count_inode_sectors(c, u.bi_inum);
+		sectors = bch2_count_inode_sectors(trans, u.bi_inum);
 		if (sectors < 0) {
 			bch_err(c, "error in fs gc: error %i "
 				"recounting inode sectors",
@@ -1303,7 +1323,7 @@ static int bch2_gc_walk_inodes(struct bch_fs *c,
 	nlinks_iter = genradix_iter_init(links, 0);
 
 	while ((k = bch2_btree_iter_peek(iter)).k &&
-	       !(ret2 = btree_iter_err(k))) {
+	       !(ret2 = bkey_err(k))) {
 peek_nlinks:	link = genradix_iter_peek(&nlinks_iter, links);
 
 		if (!link && (!k.k || iter->pos.inode >= range_end))
@@ -1323,12 +1343,6 @@ peek_nlinks:	link = genradix_iter_peek(&nlinks_iter, links);
 			link = &zero_links;
 
 		if (k.k && k.k->type == KEY_TYPE_inode) {
-			/*
-			 * Avoid potential deadlocks with iter for
-			 * truncate/rm/etc.:
-			 */
-			bch2_btree_iter_unlock(iter);
-
 			ret = check_inode(&trans, lostfound_inode, iter,
 					  bkey_s_c_to_inode(k), link);
 			BUG_ON(ret == -EINTR);
@@ -1345,7 +1359,7 @@ peek_nlinks:	link = genradix_iter_peek(&nlinks_iter, links);
 			genradix_iter_advance(&nlinks_iter, links);
 
 		bch2_btree_iter_next(iter);
-		bch2_btree_iter_cond_resched(iter);
+		bch2_trans_cond_resched(&trans);
 	}
 fsck_err:
 	bch2_trans_exit(&trans);
@@ -1399,7 +1413,7 @@ static int check_inodes_fast(struct bch_fs *c)
 	struct btree_iter *iter;
 	struct bkey_s_c k;
 	struct bkey_s_c_inode inode;
-	int ret = 0;
+	int ret = 0, ret2;
 
 	bch2_trans_init(&trans, c);
 
@@ -1423,12 +1437,9 @@ static int check_inodes_fast(struct bch_fs *c)
 		}
 	}
 
-	if (!ret)
-		ret = bch2_btree_iter_unlock(iter);
+	ret2 = bch2_trans_exit(&trans);
 
-	bch2_trans_exit(&trans);
-
-	return ret;
+	return ret ?: ret2;
 }
 
 /*
diff --git a/libbcachefs/fsck.h b/libbcachefs/fsck.h
index bc9caaf2..dc7ce687 100644
--- a/libbcachefs/fsck.h
+++ b/libbcachefs/fsck.h
@@ -1,7 +1,6 @@
 #ifndef _BCACHEFS_FSCK_H
 #define _BCACHEFS_FSCK_H
 
-s64 bch2_count_inode_sectors(struct bch_fs *, u64);
 int bch2_fsck(struct bch_fs *);
 
 #endif /* _BCACHEFS_FSCK_H */
diff --git a/libbcachefs/inode.c b/libbcachefs/inode.c
index a555a8af..58d58cc4 100644
--- a/libbcachefs/inode.c
+++ b/libbcachefs/inode.c
@@ -324,7 +324,7 @@ again:
 	while (1) {
 		struct bkey_s_c k = bch2_btree_iter_peek_slot(iter);
 
-		ret = btree_iter_err(k);
+		ret = bkey_err(k);
 		if (ret)
 			return ret;
 
@@ -400,7 +400,7 @@ int bch2_inode_rm(struct bch_fs *c, u64 inode_nr)
 		struct bkey_s_c k = bch2_btree_iter_peek_slot(iter);
 		u32 bi_generation = 0;
 
-		ret = btree_iter_err(k);
+		ret = bkey_err(k);
 		if (ret)
 			break;
 
@@ -448,13 +448,15 @@ int bch2_inode_rm(struct bch_fs *c, u64 inode_nr)
 int bch2_inode_find_by_inum(struct bch_fs *c, u64 inode_nr,
 			    struct bch_inode_unpacked *inode)
 {
-	struct btree_iter iter;
+	struct btree_trans trans;
+	struct btree_iter *iter;
 	struct bkey_s_c k;
 	int ret = -ENOENT;
 
-	for_each_btree_key(&iter, c, BTREE_ID_INODES,
-			   POS(inode_nr, 0),
-			   BTREE_ITER_SLOTS, k) {
+	bch2_trans_init(&trans, c);
+
+	for_each_btree_key(&trans, iter, BTREE_ID_INODES,
+			   POS(inode_nr, 0), BTREE_ITER_SLOTS, k) {
 		switch (k.k->type) {
 		case KEY_TYPE_inode:
 			ret = bch2_inode_unpack(bkey_s_c_to_inode(k), inode);
@@ -467,7 +469,7 @@ int bch2_inode_find_by_inum(struct bch_fs *c, u64 inode_nr,
 		break;
 	}
 
-	return bch2_btree_iter_unlock(&iter) ?: ret;
+	return bch2_trans_exit(&trans) ?: ret;
 }
 
 #ifdef CONFIG_BCACHEFS_DEBUG
diff --git a/libbcachefs/io.c b/libbcachefs/io.c
index 11b927e6..cc8a3c51 100644
--- a/libbcachefs/io.c
+++ b/libbcachefs/io.c
@@ -1245,27 +1245,28 @@ static void bch2_read_retry_nodecode(struct bch_fs *c, struct bch_read_bio *rbio
 				     struct bch_io_failures *failed,
 				     unsigned flags)
 {
-	struct btree_iter iter;
+	struct btree_trans trans;
+	struct btree_iter *iter;
 	BKEY_PADDED(k) tmp;
 	struct bkey_s_c k;
 	int ret;
 
 	flags &= ~BCH_READ_LAST_FRAGMENT;
 
-	bch2_btree_iter_init(&iter, c, BTREE_ID_EXTENTS,
-			     rbio->pos, BTREE_ITER_SLOTS);
+	bch2_trans_init(&trans, c);
+
+	iter = bch2_trans_get_iter(&trans, BTREE_ID_EXTENTS,
+				   rbio->pos, BTREE_ITER_SLOTS);
 retry:
 	rbio->bio.bi_status = 0;
 
-	k = bch2_btree_iter_peek_slot(&iter);
-	if (btree_iter_err(k)) {
-		bch2_btree_iter_unlock(&iter);
+	k = bch2_btree_iter_peek_slot(iter);
+	if (bkey_err(k))
 		goto err;
-	}
 
 	bkey_reassemble(&tmp.k, k);
 	k = bkey_i_to_s_c(&tmp.k);
-	bch2_btree_iter_unlock(&iter);
+	bch2_trans_unlock(&trans);
 
 	if (!bkey_extent_is_data(k.k) ||
 	    !bch2_extent_matches_ptr(c, bkey_i_to_s_c_extent(&tmp.k),
@@ -1282,25 +1283,30 @@ retry:
 		goto retry;
 	if (ret)
 		goto err;
-	goto out;
-err:
-	rbio->bio.bi_status = BLK_STS_IOERR;
 out:
 	bch2_rbio_done(rbio);
+	bch2_trans_exit(&trans);
+	return;
+err:
+	rbio->bio.bi_status = BLK_STS_IOERR;
+	goto out;
 }
 
 static void bch2_read_retry(struct bch_fs *c, struct bch_read_bio *rbio,
 			    struct bvec_iter bvec_iter, u64 inode,
 			    struct bch_io_failures *failed, unsigned flags)
 {
-	struct btree_iter iter;
+	struct btree_trans trans;
+	struct btree_iter *iter;
 	struct bkey_s_c k;
 	int ret;
 
+	bch2_trans_init(&trans, c);
+
 	flags &= ~BCH_READ_LAST_FRAGMENT;
 	flags |= BCH_READ_MUST_CLONE;
 retry:
-	for_each_btree_key(&iter, c, BTREE_ID_EXTENTS,
+	for_each_btree_key(&trans, iter, BTREE_ID_EXTENTS,
 			   POS(inode, bvec_iter.bi_sector),
 			   BTREE_ITER_SLOTS, k) {
 		BKEY_PADDED(k) tmp;
@@ -1308,7 +1314,7 @@ retry:
 
 		bkey_reassemble(&tmp.k, k);
 		k = bkey_i_to_s_c(&tmp.k);
-		bch2_btree_iter_unlock(&iter);
+		bch2_btree_trans_unlock(&trans);
 
 		bytes = min_t(unsigned, bvec_iter.bi_size,
 			      (k.k->p.offset - bvec_iter.bi_sector) << 9);
@@ -1333,12 +1339,12 @@ retry:
 	 * If we get here, it better have been because there was an error
 	 * reading a btree node
 	 */
-	ret = bch2_btree_iter_unlock(&iter);
-	BUG_ON(!ret);
-	__bcache_io_error(c, "btree IO error %i", ret);
+	BUG_ON(!btree_iter_err(iter));
+	__bcache_io_error(c, "btree IO error");
 err:
 	rbio->bio.bi_status = BLK_STS_IOERR;
 out:
+	bch2_trans_exit(&trans);
 	bch2_rbio_done(rbio);
 }
 
@@ -1834,12 +1840,14 @@ out_read_done:
 
 void bch2_read(struct bch_fs *c, struct bch_read_bio *rbio, u64 inode)
 {
-	struct btree_iter iter;
+	struct btree_trans trans;
+	struct btree_iter *iter;
 	struct bkey_s_c k;
 	unsigned flags = BCH_READ_RETRY_IF_STALE|
 		BCH_READ_MAY_PROMOTE|
 		BCH_READ_USER_MAPPED;
-	int ret;
+
+	bch2_trans_init(&trans, c);
 
 	BUG_ON(rbio->_state);
 	BUG_ON(flags & BCH_READ_NODECODE);
@@ -1848,7 +1856,7 @@ void bch2_read(struct bch_fs *c, struct bch_read_bio *rbio, u64 inode)
 	rbio->c = c;
 	rbio->start_time = local_clock();
 
-	for_each_btree_key(&iter, c, BTREE_ID_EXTENTS,
+	for_each_btree_key(&trans, iter, BTREE_ID_EXTENTS,
 			   POS(inode, rbio->bio.bi_iter.bi_sector),
 			   BTREE_ITER_SLOTS, k) {
 		BKEY_PADDED(k) tmp;
@@ -1860,7 +1868,7 @@ void bch2_read(struct bch_fs *c, struct bch_read_bio *rbio, u64 inode)
 		 */
 		bkey_reassemble(&tmp.k, k);
 		k = bkey_i_to_s_c(&tmp.k);
-		bch2_btree_iter_unlock(&iter);
+		bch2_btree_trans_unlock(&trans);
 
 		bytes = min_t(unsigned, rbio->bio.bi_iter.bi_size,
 			      (k.k->p.offset - rbio->bio.bi_iter.bi_sector) << 9);
@@ -1882,9 +1890,10 @@ void bch2_read(struct bch_fs *c, struct bch_read_bio *rbio, u64 inode)
 	 * If we get here, it better have been because there was an error
 	 * reading a btree node
 	 */
-	ret = bch2_btree_iter_unlock(&iter);
-	BUG_ON(!ret);
-	bcache_io_error(c, &rbio->bio, "btree IO error %i", ret);
+	BUG_ON(!btree_iter_err(iter));
+	bcache_io_error(c, &rbio->bio, "btree IO error");
+
+	bch2_trans_exit(&trans);
 	bch2_rbio_done(rbio);
 }
 
diff --git a/libbcachefs/journal_seq_blacklist.c b/libbcachefs/journal_seq_blacklist.c
index dd0e8d2f..5bac41cf 100644
--- a/libbcachefs/journal_seq_blacklist.c
+++ b/libbcachefs/journal_seq_blacklist.c
@@ -61,9 +61,12 @@ static void journal_seq_blacklist_flush(struct journal *j,
 	closure_init_stack(&cl);
 
 	for (i = 0;; i++) {
-		struct btree_iter iter;
+		struct btree_trans trans;
+		struct btree_iter *iter;
 		struct btree *b;
 
+		bch2_trans_init(&trans, c);
+
 		mutex_lock(&j->blacklist_lock);
 		if (i >= bl->nr_entries) {
 			mutex_unlock(&j->blacklist_lock);
@@ -72,17 +75,17 @@ static void journal_seq_blacklist_flush(struct journal *j,
 		n = bl->entries[i];
 		mutex_unlock(&j->blacklist_lock);
 
-		__bch2_btree_iter_init(&iter, c, n.btree_id, n.pos,
-				       0, 0, BTREE_ITER_NODES);
+		iter = bch2_trans_get_node_iter(&trans, n.btree_id, n.pos,
+						0, 0, 0);
 
-		b = bch2_btree_iter_peek_node(&iter);
+		b = bch2_btree_iter_peek_node(iter);
 
 		/* The node might have already been rewritten: */
 
 		if (b->data->keys.seq == n.seq) {
-			ret = bch2_btree_node_rewrite(c, &iter, n.seq, 0);
+			ret = bch2_btree_node_rewrite(c, iter, n.seq, 0);
 			if (ret) {
-				bch2_btree_iter_unlock(&iter);
+				bch2_trans_exit(&trans);
 				bch2_fs_fatal_error(c,
 					"error %i rewriting btree node with blacklisted journal seq",
 					ret);
@@ -91,7 +94,7 @@ static void journal_seq_blacklist_flush(struct journal *j,
 			}
 		}
 
-		bch2_btree_iter_unlock(&iter);
+		bch2_trans_exit(&trans);
 	}
 
 	for (i = 0;; i++) {
diff --git a/libbcachefs/migrate.c b/libbcachefs/migrate.c
index 58d7d3a3..88761d34 100644
--- a/libbcachefs/migrate.c
+++ b/libbcachefs/migrate.c
@@ -51,7 +51,7 @@ static int bch2_dev_usrdata_drop(struct bch_fs *c, unsigned dev_idx, int flags)
 
 
 	while ((k = bch2_btree_iter_peek(iter)).k &&
-	       !(ret = btree_iter_err(k))) {
+	       !(ret = bkey_err(k))) {
 		if (!bkey_extent_is_data(k.k) ||
 		    !bch2_extent_has_device(bkey_s_c_to_extent(k), dev_idx)) {
 			ret = bch2_mark_bkey_replicas(c, k);
@@ -105,7 +105,8 @@ static int bch2_dev_usrdata_drop(struct bch_fs *c, unsigned dev_idx, int flags)
 
 static int bch2_dev_metadata_drop(struct bch_fs *c, unsigned dev_idx, int flags)
 {
-	struct btree_iter iter;
+	struct btree_trans trans;
+	struct btree_iter *iter;
 	struct closure cl;
 	struct btree *b;
 	unsigned id;
@@ -115,13 +116,15 @@ static int bch2_dev_metadata_drop(struct bch_fs *c, unsigned dev_idx, int flags)
 	if (flags & BCH_FORCE_IF_METADATA_LOST)
 		return -EINVAL;
 
+	bch2_trans_init(&trans, c);
 	closure_init_stack(&cl);
 
 	mutex_lock(&c->replicas_gc_lock);
 	bch2_replicas_gc_start(c, 1 << BCH_DATA_BTREE);
 
 	for (id = 0; id < BTREE_ID_NR; id++) {
-		for_each_btree_node(&iter, c, id, POS_MIN, BTREE_ITER_PREFETCH, b) {
+		for_each_btree_node(&trans, iter, id, POS_MIN,
+				    BTREE_ITER_PREFETCH, b) {
 			__BKEY_PADDED(k, BKEY_BTREE_PTR_VAL_U64s_MAX) tmp;
 			struct bkey_i_btree_ptr *new_key;
 retry:
@@ -133,7 +136,7 @@ retry:
 				 * but got -EINTR after upgrading the iter, but
 				 * then raced and the node is now gone:
 				 */
-				bch2_btree_iter_downgrade(&iter);
+				bch2_btree_iter_downgrade(iter);
 
 				ret = bch2_mark_bkey_replicas(c, bkey_i_to_s_c(&b->key));
 				if (ret)
@@ -147,16 +150,16 @@ retry:
 				if (ret)
 					goto err;
 
-				ret = bch2_btree_node_update_key(c, &iter, b, new_key);
+				ret = bch2_btree_node_update_key(c, iter, b, new_key);
 				if (ret == -EINTR) {
-					b = bch2_btree_iter_peek_node(&iter);
+					b = bch2_btree_iter_peek_node(iter);
 					goto retry;
 				}
 				if (ret)
 					goto err;
 			}
 		}
-		bch2_btree_iter_unlock(&iter);
+		bch2_trans_iter_free(&trans, iter);
 	}
 
 	/* flush relevant btree updates */
@@ -170,14 +173,13 @@ retry:
 	}
 
 	ret = 0;
-out:
+err:
+	bch2_trans_exit(&trans);
+
 	ret = bch2_replicas_gc_end(c, ret);
 	mutex_unlock(&c->replicas_gc_lock);
 
 	return ret;
-err:
-	bch2_btree_iter_unlock(&iter);
-	goto out;
 }
 
 int bch2_dev_data_drop(struct bch_fs *c, unsigned dev_idx, int flags)
diff --git a/libbcachefs/move.c b/libbcachefs/move.c
index 3315bedc..1e7448ba 100644
--- a/libbcachefs/move.c
+++ b/libbcachefs/move.c
@@ -77,7 +77,7 @@ static int bch2_migrate_index_update(struct bch_write_op *op)
 		bool did_work = false;
 		int nr;
 
-		ret = btree_iter_err(k);
+		ret = bkey_err(k);
 		if (ret)
 			break;
 
@@ -486,6 +486,8 @@ int bch2_move_data(struct bch_fs *c,
 	struct moving_context ctxt = { .stats = stats };
 	struct bch_io_opts io_opts = bch2_opts_to_inode_opts(c->opts);
 	BKEY_PADDED(k) tmp;
+	struct btree_trans trans;
+	struct btree_iter *iter;
 	struct bkey_s_c k;
 	struct data_opts data_opts;
 	enum data_cmd data_cmd;
@@ -496,9 +498,14 @@ int bch2_move_data(struct bch_fs *c,
 	INIT_LIST_HEAD(&ctxt.reads);
 	init_waitqueue_head(&ctxt.wait);
 
+	bch2_trans_init(&trans, c);
+
 	stats->data_type = BCH_DATA_USER;
-	bch2_btree_iter_init(&stats->iter, c, BTREE_ID_EXTENTS, start,
-			     BTREE_ITER_PREFETCH);
+	stats->btree_id	= BTREE_ID_EXTENTS;
+	stats->pos	= POS_MIN;
+
+	iter = bch2_trans_get_iter(&trans, BTREE_ID_EXTENTS, start,
+				   BTREE_ITER_PREFETCH);
 
 	if (rate)
 		bch2_ratelimit_reset(rate);
@@ -508,7 +515,7 @@ int bch2_move_data(struct bch_fs *c,
 			delay = rate ? bch2_ratelimit_delay(rate) : 0;
 
 			if (delay) {
-				bch2_btree_iter_unlock(&stats->iter);
+				bch2_trans_unlock(&trans);
 				set_current_state(TASK_INTERRUPTIBLE);
 			}
 
@@ -521,16 +528,19 @@ int bch2_move_data(struct bch_fs *c,
 				schedule_timeout(delay);
 
 			if (unlikely(freezing(current))) {
-				bch2_btree_iter_unlock(&stats->iter);
+				bch2_trans_unlock(&trans);
 				move_ctxt_wait_event(&ctxt, list_empty(&ctxt.reads));
 				try_to_freeze();
 			}
 		} while (delay);
 peek:
-		k = bch2_btree_iter_peek(&stats->iter);
+		k = bch2_btree_iter_peek(iter);
+
+		stats->pos = iter->pos;
+
 		if (!k.k)
 			break;
-		ret = btree_iter_err(k);
+		ret = bkey_err(k);
 		if (ret)
 			break;
 		if (bkey_cmp(bkey_start_pos(k.k), end) >= 0)
@@ -543,7 +553,7 @@ peek:
 			struct bch_inode_unpacked inode;
 
 			/* don't hold btree locks while looking up inode: */
-			bch2_btree_iter_unlock(&stats->iter);
+			bch2_trans_unlock(&trans);
 
 			io_opts = bch2_opts_to_inode_opts(c->opts);
 			if (!bch2_inode_find_by_inum(c, k.k->p.inode, &inode))
@@ -568,7 +578,7 @@ peek:
 		/* unlock before doing IO: */
 		bkey_reassemble(&tmp.k, k);
 		k = bkey_i_to_s_c(&tmp.k);
-		bch2_btree_iter_unlock(&stats->iter);
+		bch2_trans_unlock(&trans);
 
 		ret2 = bch2_move_extent(c, &ctxt, wp, io_opts,
 					bkey_s_c_to_extent(k),
@@ -590,11 +600,11 @@ next:
 		atomic64_add(k.k->size * bch2_bkey_nr_dirty_ptrs(k),
 			     &stats->sectors_seen);
 next_nondata:
-		bch2_btree_iter_next(&stats->iter);
-		bch2_btree_iter_cond_resched(&stats->iter);
+		bch2_btree_iter_next(iter);
+		bch2_trans_cond_resched(&trans);
 	}
 out:
-	bch2_btree_iter_unlock(&stats->iter);
+	bch2_trans_exit(&trans);
 
 	move_ctxt_wait_event(&ctxt, list_empty(&ctxt.reads));
 	closure_sync(&ctxt.cl);
@@ -610,20 +620,23 @@ out:
 
 static int bch2_gc_data_replicas(struct bch_fs *c)
 {
-	struct btree_iter iter;
+	struct btree_trans trans;
+	struct btree_iter *iter;
 	struct bkey_s_c k;
 	int ret;
 
+	bch2_trans_init(&trans, c);
+
 	mutex_lock(&c->replicas_gc_lock);
 	bch2_replicas_gc_start(c, (1 << BCH_DATA_USER)|(1 << BCH_DATA_CACHED));
 
-	for_each_btree_key(&iter, c, BTREE_ID_EXTENTS, POS_MIN,
+	for_each_btree_key(&trans, iter, BTREE_ID_EXTENTS, POS_MIN,
 			   BTREE_ITER_PREFETCH, k) {
 		ret = bch2_mark_bkey_replicas(c, k);
 		if (ret)
 			break;
 	}
-	ret = bch2_btree_iter_unlock(&iter) ?: ret;
+	ret = bch2_trans_exit(&trans) ?: ret;
 
 	bch2_replicas_gc_end(c, ret);
 	mutex_unlock(&c->replicas_gc_lock);
@@ -633,24 +646,30 @@ static int bch2_gc_data_replicas(struct bch_fs *c)
 
 static int bch2_gc_btree_replicas(struct bch_fs *c)
 {
-	struct btree_iter iter;
+	struct btree_trans trans;
+	struct btree_iter *iter;
 	struct btree *b;
 	unsigned id;
 	int ret = 0;
 
+	bch2_trans_init(&trans, c);
+
 	mutex_lock(&c->replicas_gc_lock);
 	bch2_replicas_gc_start(c, 1 << BCH_DATA_BTREE);
 
 	for (id = 0; id < BTREE_ID_NR; id++) {
-		for_each_btree_node(&iter, c, id, POS_MIN, BTREE_ITER_PREFETCH, b) {
+		for_each_btree_node(&trans, iter, id, POS_MIN,
+				    BTREE_ITER_PREFETCH, b) {
 			ret = bch2_mark_bkey_replicas(c, bkey_i_to_s_c(&b->key));
 
-			bch2_btree_iter_cond_resched(&iter);
+			bch2_trans_cond_resched(&trans);
 		}
 
-		ret = bch2_btree_iter_unlock(&iter) ?: ret;
+		ret = bch2_trans_iter_free(&trans, iter) ?: ret;
 	}
 
+	bch2_trans_exit(&trans);
+
 	bch2_replicas_gc_end(c, ret);
 	mutex_unlock(&c->replicas_gc_lock);
 
@@ -663,16 +682,25 @@ static int bch2_move_btree(struct bch_fs *c,
 			   struct bch_move_stats *stats)
 {
 	struct bch_io_opts io_opts = bch2_opts_to_inode_opts(c->opts);
+	struct btree_trans trans;
+	struct btree_iter *iter;
 	struct btree *b;
 	unsigned id;
 	struct data_opts data_opts;
 	enum data_cmd cmd;
 	int ret = 0;
 
+	bch2_trans_init(&trans, c);
+
 	stats->data_type = BCH_DATA_BTREE;
 
 	for (id = 0; id < BTREE_ID_NR; id++) {
-		for_each_btree_node(&stats->iter, c, id, POS_MIN, BTREE_ITER_PREFETCH, b) {
+		stats->btree_id = id;
+
+		for_each_btree_node(&trans, iter, id, POS_MIN,
+				    BTREE_ITER_PREFETCH, b) {
+			stats->pos = iter->pos;
+
 			switch ((cmd = pred(c, arg,
 					    bkey_i_to_s_c(&b->key),
 					    &io_opts, &data_opts))) {
@@ -687,15 +715,17 @@ static int bch2_move_btree(struct bch_fs *c,
 				BUG();
 			}
 
-			ret = bch2_btree_node_rewrite(c, &stats->iter,
+			ret = bch2_btree_node_rewrite(c, iter,
 					b->data->keys.seq, 0) ?: ret;
 next:
-			bch2_btree_iter_cond_resched(&stats->iter);
+			bch2_trans_cond_resched(&trans);
 		}
 
-		ret = bch2_btree_iter_unlock(&stats->iter) ?: ret;
+		ret = bch2_trans_iter_free(&trans, iter) ?: ret;
 	}
 
+	bch2_trans_exit(&trans);
+
 	return ret;
 }
 
diff --git a/libbcachefs/move_types.h b/libbcachefs/move_types.h
index 832542a8..7703ce43 100644
--- a/libbcachefs/move_types.h
+++ b/libbcachefs/move_types.h
@@ -3,7 +3,8 @@
 
 struct bch_move_stats {
 	enum bch_data_type	data_type;
-	struct btree_iter	iter;
+	enum btree_id		btree_id;
+	struct bpos		pos;
 
 	atomic64_t		keys_moved;
 	atomic64_t		sectors_moved;
diff --git a/libbcachefs/quota.c b/libbcachefs/quota.c
index 6606e85c..b988a565 100644
--- a/libbcachefs/quota.c
+++ b/libbcachefs/quota.c
@@ -355,11 +355,14 @@ static int __bch2_quota_set(struct bch_fs *c, struct bkey_s_c k)
 
 static int bch2_quota_init_type(struct bch_fs *c, enum quota_types type)
 {
-	struct btree_iter iter;
+	struct btree_trans trans;
+	struct btree_iter *iter;
 	struct bkey_s_c k;
 	int ret = 0;
 
-	for_each_btree_key(&iter, c, BTREE_ID_QUOTAS, POS(type, 0),
+	bch2_trans_init(&trans, c);
+
+	for_each_btree_key(&trans, iter, BTREE_ID_QUOTAS, POS(type, 0),
 			   BTREE_ITER_PREFETCH, k) {
 		if (k.k->p.inode != type)
 			break;
@@ -369,7 +372,7 @@ static int bch2_quota_init_type(struct bch_fs *c, enum quota_types type)
 			break;
 	}
 
-	return bch2_btree_iter_unlock(&iter) ?: ret;
+	return bch2_trans_exit(&trans) ?: ret;
 }
 
 void bch2_fs_quota_exit(struct bch_fs *c)
@@ -413,7 +416,8 @@ int bch2_fs_quota_read(struct bch_fs *c)
 {
 	unsigned i, qtypes = enabled_qtypes(c);
 	struct bch_memquota_type *q;
-	struct btree_iter iter;
+	struct btree_trans trans;
+	struct btree_iter *iter;
 	struct bch_inode_unpacked u;
 	struct bkey_s_c k;
 	int ret;
@@ -428,7 +432,9 @@ int bch2_fs_quota_read(struct bch_fs *c)
 			return ret;
 	}
 
-	for_each_btree_key(&iter, c, BTREE_ID_INODES, POS_MIN,
+	bch2_trans_init(&trans, c);
+
+	for_each_btree_key(&trans, iter, BTREE_ID_INODES, POS_MIN,
 			   BTREE_ITER_PREFETCH, k) {
 		switch (k.k->type) {
 		case KEY_TYPE_inode:
@@ -442,7 +448,7 @@ int bch2_fs_quota_read(struct bch_fs *c)
 					KEY_TYPE_QUOTA_NOCHECK);
 		}
 	}
-	return bch2_btree_iter_unlock(&iter) ?: ret;
+	return bch2_trans_exit(&trans) ?: ret;
 }
 
 /* Enable/disable/delete quotas for an entire filesystem: */
@@ -725,7 +731,7 @@ static int bch2_set_quota(struct super_block *sb, struct kqid qid,
 				   BTREE_ITER_SLOTS|BTREE_ITER_INTENT);
 	k = bch2_btree_iter_peek_slot(iter);
 
-	ret = btree_iter_err(k);
+	ret = bkey_err(k);
 	if (unlikely(ret))
 		return ret;
 
diff --git a/libbcachefs/rebalance.c b/libbcachefs/rebalance.c
index 768c0284..d7698451 100644
--- a/libbcachefs/rebalance.c
+++ b/libbcachefs/rebalance.c
@@ -288,8 +288,8 @@ ssize_t bch2_rebalance_work_show(struct bch_fs *c, char *buf)
 	case REBALANCE_RUNNING:
 		pr_buf(&out, "running\n");
 		pr_buf(&out, "pos %llu:%llu\n",
-		       r->move_stats.iter.pos.inode,
-		       r->move_stats.iter.pos.offset);
+		       r->move_stats.pos.inode,
+		       r->move_stats.pos.offset);
 		break;
 	}
 
diff --git a/libbcachefs/str_hash.h b/libbcachefs/str_hash.h
index f78f07bd..f928ca99 100644
--- a/libbcachefs/str_hash.h
+++ b/libbcachefs/str_hash.h
@@ -203,13 +203,16 @@ int bch2_hash_needs_whiteout(struct btree_trans *trans,
 	for_each_btree_key_continue(iter, BTREE_ITER_SLOTS, k) {
 		if (k.k->type != desc.key_type &&
 		    k.k->type != KEY_TYPE_whiteout)
-			return false;
+			break;
 
 		if (k.k->type == desc.key_type &&
-		    desc.hash_bkey(info, k) <= start->pos.offset)
-			return true;
+		    desc.hash_bkey(info, k) <= start->pos.offset) {
+			bch2_trans_iter_free_on_commit(trans, iter);
+			return 1;
+		}
 	}
-	return btree_iter_err(k);
+
+	return bch2_trans_iter_free(trans, iter);
 }
 
 static __always_inline
@@ -220,6 +223,8 @@ int bch2_hash_set(struct btree_trans *trans,
 {
 	struct btree_iter *iter, *slot = NULL;
 	struct bkey_s_c k;
+	bool found = false;
+	int ret = 0;
 
 	iter = bch2_trans_get_iter(trans, desc.btree_id,
 			POS(inode, desc.hash_bkey(info, bkey_i_to_s_c(insert))),
@@ -250,21 +255,30 @@ int bch2_hash_set(struct btree_trans *trans,
 			goto not_found;
 	}
 
-	return btree_iter_err(k) ?: -ENOSPC;
-not_found:
-	if (flags & BCH_HASH_SET_MUST_REPLACE)
-		return -ENOENT;
+	if (slot)
+		bch2_trans_iter_free(trans, iter);
 
-	insert->k.p = slot->pos;
-	bch2_trans_update(trans, BTREE_INSERT_ENTRY(slot, insert));
-	return 0;
+	return bch2_trans_iter_free(trans, iter) ?: -ENOSPC;
 found:
-	if (flags & BCH_HASH_SET_MUST_CREATE)
-		return -EEXIST;
+	found = true;
+not_found:
 
-	insert->k.p = iter->pos;
-	bch2_trans_update(trans, BTREE_INSERT_ENTRY(iter, insert));
-	return 0;
+	if (!found && (flags & BCH_HASH_SET_MUST_REPLACE)) {
+		ret = -ENOENT;
+	} else if (found && (flags & BCH_HASH_SET_MUST_CREATE)) {
+		ret = -EEXIST;
+	} else {
+		if (!found && slot) {
+			bch2_trans_iter_free(trans, iter);
+			iter = slot;
+		}
+
+		insert->k.p = iter->pos;
+		bch2_trans_update(trans, BTREE_INSERT_ENTRY(iter, insert));
+		bch2_trans_iter_free_on_commit(trans, iter);
+	}
+
+	return ret;
 }
 
 static __always_inline
diff --git a/libbcachefs/sysfs.c b/libbcachefs/sysfs.c
index a6d70ce5..f9731513 100644
--- a/libbcachefs/sysfs.c
+++ b/libbcachefs/sysfs.c
@@ -281,7 +281,8 @@ static ssize_t show_fs_alloc_debug(struct bch_fs *c, char *buf)
 
 static ssize_t bch2_compression_stats(struct bch_fs *c, char *buf)
 {
-	struct btree_iter iter;
+	struct btree_trans trans;
+	struct btree_iter *iter;
 	struct bkey_s_c k;
 	u64 nr_uncompressed_extents = 0, uncompressed_sectors = 0,
 	    nr_compressed_extents = 0,
@@ -291,7 +292,9 @@ static ssize_t bch2_compression_stats(struct bch_fs *c, char *buf)
 	if (!test_bit(BCH_FS_STARTED, &c->flags))
 		return -EPERM;
 
-	for_each_btree_key(&iter, c, BTREE_ID_EXTENTS, POS_MIN, 0, k)
+	bch2_trans_init(&trans, c);
+
+	for_each_btree_key(&trans, iter, BTREE_ID_EXTENTS, POS_MIN, 0, k)
 		if (k.k->type == KEY_TYPE_extent) {
 			struct bkey_s_c_extent e = bkey_s_c_to_extent(k);
 			const union bch_extent_entry *entry;
@@ -313,7 +316,7 @@ static ssize_t bch2_compression_stats(struct bch_fs *c, char *buf)
 				break;
 			}
 		}
-	bch2_btree_iter_unlock(&iter);
+	bch2_trans_exit(&trans);
 
 	return scnprintf(buf, PAGE_SIZE,
 			"uncompressed data:\n"
diff --git a/libbcachefs/tests.c b/libbcachefs/tests.c
index c9362af5..a7b6fef2 100644
--- a/libbcachefs/tests.c
+++ b/libbcachefs/tests.c
@@ -88,11 +88,14 @@ static void test_delete_written(struct bch_fs *c, u64 nr)
 
 static void test_iterate(struct bch_fs *c, u64 nr)
 {
-	struct btree_iter iter;
+	struct btree_trans trans;
+	struct btree_iter *iter;
 	struct bkey_s_c k;
 	u64 i;
 	int ret;
 
+	bch2_trans_init(&trans, c);
+
 	delete_test_keys(c);
 
 	pr_info("inserting test keys");
@@ -112,28 +115,31 @@ static void test_iterate(struct bch_fs *c, u64 nr)
 
 	i = 0;
 
-	for_each_btree_key(&iter, c, BTREE_ID_DIRENTS, POS(0, 0), 0, k)
+	for_each_btree_key(&trans, iter, BTREE_ID_DIRENTS, POS(0, 0), 0, k)
 		BUG_ON(k.k->p.offset != i++);
-	bch2_btree_iter_unlock(&iter);
 
 	BUG_ON(i != nr);
 
 	pr_info("iterating backwards");
 
-	while (!IS_ERR_OR_NULL((k = bch2_btree_iter_prev(&iter)).k))
+	while (!IS_ERR_OR_NULL((k = bch2_btree_iter_prev(iter)).k))
 		BUG_ON(k.k->p.offset != --i);
-	bch2_btree_iter_unlock(&iter);
 
 	BUG_ON(i);
+
+	bch2_trans_exit(&trans);
 }
 
 static void test_iterate_extents(struct bch_fs *c, u64 nr)
 {
-	struct btree_iter iter;
+	struct btree_trans trans;
+	struct btree_iter *iter;
 	struct bkey_s_c k;
 	u64 i;
 	int ret;
 
+	bch2_trans_init(&trans, c);
+
 	delete_test_keys(c);
 
 	pr_info("inserting test extents");
@@ -154,32 +160,35 @@ static void test_iterate_extents(struct bch_fs *c, u64 nr)
 
 	i = 0;
 
-	for_each_btree_key(&iter, c, BTREE_ID_EXTENTS, POS(0, 0), 0, k) {
+	for_each_btree_key(&trans, iter, BTREE_ID_EXTENTS, POS(0, 0), 0, k) {
 		BUG_ON(bkey_start_offset(k.k) != i);
 		i = k.k->p.offset;
 	}
-	bch2_btree_iter_unlock(&iter);
 
 	BUG_ON(i != nr);
 
 	pr_info("iterating backwards");
 
-	while (!IS_ERR_OR_NULL((k = bch2_btree_iter_prev(&iter)).k)) {
+	while (!IS_ERR_OR_NULL((k = bch2_btree_iter_prev(iter)).k)) {
 		BUG_ON(k.k->p.offset != i);
 		i = bkey_start_offset(k.k);
 	}
-	bch2_btree_iter_unlock(&iter);
 
 	BUG_ON(i);
+
+	bch2_trans_exit(&trans);
 }
 
 static void test_iterate_slots(struct bch_fs *c, u64 nr)
 {
-	struct btree_iter iter;
+	struct btree_trans trans;
+	struct btree_iter *iter;
 	struct bkey_s_c k;
 	u64 i;
 	int ret;
 
+	bch2_trans_init(&trans, c);
+
 	delete_test_keys(c);
 
 	pr_info("inserting test keys");
@@ -199,11 +208,11 @@ static void test_iterate_slots(struct bch_fs *c, u64 nr)
 
 	i = 0;
 
-	for_each_btree_key(&iter, c, BTREE_ID_DIRENTS, POS(0, 0), 0, k) {
+	for_each_btree_key(&trans, iter, BTREE_ID_DIRENTS, POS(0, 0), 0, k) {
 		BUG_ON(k.k->p.offset != i);
 		i += 2;
 	}
-	bch2_btree_iter_unlock(&iter);
+	bch2_trans_iter_free(&trans, iter);
 
 	BUG_ON(i != nr * 2);
 
@@ -211,7 +220,7 @@ static void test_iterate_slots(struct bch_fs *c, u64 nr)
 
 	i = 0;
 
-	for_each_btree_key(&iter, c, BTREE_ID_DIRENTS, POS(0, 0),
+	for_each_btree_key(&trans, iter, BTREE_ID_DIRENTS, POS(0, 0),
 			   BTREE_ITER_SLOTS, k) {
 		BUG_ON(bkey_deleted(k.k) != (i & 1));
 		BUG_ON(k.k->p.offset != i++);
@@ -219,16 +228,20 @@ static void test_iterate_slots(struct bch_fs *c, u64 nr)
 		if (i == nr * 2)
 			break;
 	}
-	bch2_btree_iter_unlock(&iter);
+
+	bch2_trans_exit(&trans);
 }
 
 static void test_iterate_slots_extents(struct bch_fs *c, u64 nr)
 {
-	struct btree_iter iter;
+	struct btree_trans trans;
+	struct btree_iter *iter;
 	struct bkey_s_c k;
 	u64 i;
 	int ret;
 
+	bch2_trans_init(&trans, c);
+
 	delete_test_keys(c);
 
 	pr_info("inserting test keys");
@@ -249,12 +262,12 @@ static void test_iterate_slots_extents(struct bch_fs *c, u64 nr)
 
 	i = 0;
 
-	for_each_btree_key(&iter, c, BTREE_ID_EXTENTS, POS(0, 0), 0, k) {
+	for_each_btree_key(&trans, iter, BTREE_ID_EXTENTS, POS(0, 0), 0, k) {
 		BUG_ON(bkey_start_offset(k.k) != i + 8);
 		BUG_ON(k.k->size != 8);
 		i += 16;
 	}
-	bch2_btree_iter_unlock(&iter);
+	bch2_trans_iter_free(&trans, iter);
 
 	BUG_ON(i != nr);
 
@@ -262,7 +275,7 @@ static void test_iterate_slots_extents(struct bch_fs *c, u64 nr)
 
 	i = 0;
 
-	for_each_btree_key(&iter, c, BTREE_ID_EXTENTS, POS(0, 0),
+	for_each_btree_key(&trans, iter, BTREE_ID_EXTENTS, POS(0, 0),
 			   BTREE_ITER_SLOTS, k) {
 		BUG_ON(bkey_deleted(k.k) != !(i % 16));
 
@@ -273,7 +286,8 @@ static void test_iterate_slots_extents(struct bch_fs *c, u64 nr)
 		if (i == nr)
 			break;
 	}
-	bch2_btree_iter_unlock(&iter);
+
+	bch2_trans_exit(&trans);
 }
 
 /*
@@ -282,34 +296,40 @@ static void test_iterate_slots_extents(struct bch_fs *c, u64 nr)
  */
 static void test_peek_end(struct bch_fs *c, u64 nr)
 {
-	struct btree_iter iter;
+	struct btree_trans trans;
+	struct btree_iter *iter;
 	struct bkey_s_c k;
 
-	bch2_btree_iter_init(&iter, c, BTREE_ID_DIRENTS, POS_MIN, 0);
+	bch2_trans_init(&trans, c);
 
-	k = bch2_btree_iter_peek(&iter);
+	iter = bch2_trans_get_iter(&trans, BTREE_ID_DIRENTS, POS_MIN, 0);
+
+	k = bch2_btree_iter_peek(iter);
 	BUG_ON(k.k);
 
-	k = bch2_btree_iter_peek(&iter);
+	k = bch2_btree_iter_peek(iter);
 	BUG_ON(k.k);
 
-	bch2_btree_iter_unlock(&iter);
+	bch2_trans_exit(&trans);
 }
 
 static void test_peek_end_extents(struct bch_fs *c, u64 nr)
 {
-	struct btree_iter iter;
+	struct btree_trans trans;
+	struct btree_iter *iter;
 	struct bkey_s_c k;
 
-	bch2_btree_iter_init(&iter, c, BTREE_ID_EXTENTS, POS_MIN, 0);
+	bch2_trans_init(&trans, c);
 
-	k = bch2_btree_iter_peek(&iter);
+	iter = bch2_trans_get_iter(&trans, BTREE_ID_EXTENTS, POS_MIN, 0);
+
+	k = bch2_btree_iter_peek(iter);
 	BUG_ON(k.k);
 
-	k = bch2_btree_iter_peek(&iter);
+	k = bch2_btree_iter_peek(iter);
 	BUG_ON(k.k);
 
-	bch2_btree_iter_unlock(&iter);
+	bch2_trans_exit(&trans);
 }
 
 /* extent unit tests */
@@ -400,32 +420,35 @@ static void rand_insert(struct bch_fs *c, u64 nr)
 
 static void rand_lookup(struct bch_fs *c, u64 nr)
 {
+	struct btree_trans trans;
+	struct btree_iter *iter;
+	struct bkey_s_c k;
 	u64 i;
 
+	bch2_trans_init(&trans, c);
+
 	for (i = 0; i < nr; i++) {
-		struct btree_iter iter;
-		struct bkey_s_c k;
+		iter = bch2_trans_get_iter(&trans, BTREE_ID_DIRENTS,
+					   POS(0, test_rand()), 0);
 
-		bch2_btree_iter_init(&iter, c, BTREE_ID_DIRENTS,
-				     POS(0, test_rand()), 0);
-
-		k = bch2_btree_iter_peek(&iter);
-		bch2_btree_iter_unlock(&iter);
+		k = bch2_btree_iter_peek(iter);
+		bch2_trans_iter_free(&trans, iter);
 	}
+
+	bch2_trans_exit(&trans);
 }
 
 static void rand_mixed(struct bch_fs *c, u64 nr)
 {
+	struct btree_trans trans;
+	struct btree_iter *iter;
+	struct bkey_s_c k;
 	int ret;
 	u64 i;
 
+	bch2_trans_init(&trans, c);
+
 	for (i = 0; i < nr; i++) {
-		struct btree_trans trans;
-		struct btree_iter *iter;
-		struct bkey_s_c k;
-
-		bch2_trans_init(&trans, c);
-
 		iter = bch2_trans_get_iter(&trans, BTREE_ID_DIRENTS,
 					   POS(0, test_rand()), 0);
 
@@ -442,9 +465,10 @@ static void rand_mixed(struct bch_fs *c, u64 nr)
 			BUG_ON(ret);
 		}
 
-		bch2_trans_exit(&trans);
+		bch2_trans_iter_free(&trans, iter);
 	}
 
+	bch2_trans_exit(&trans);
 }
 
 static void rand_delete(struct bch_fs *c, u64 nr)
@@ -494,12 +518,15 @@ static void seq_insert(struct bch_fs *c, u64 nr)
 
 static void seq_lookup(struct bch_fs *c, u64 nr)
 {
-	struct btree_iter iter;
+	struct btree_trans trans;
+	struct btree_iter *iter;
 	struct bkey_s_c k;
 
-	for_each_btree_key(&iter, c, BTREE_ID_DIRENTS, POS_MIN, 0, k)
+	bch2_trans_init(&trans, c);
+
+	for_each_btree_key(&trans, iter, BTREE_ID_DIRENTS, POS_MIN, 0, k)
 		;
-	bch2_btree_iter_unlock(&iter);
+	bch2_trans_exit(&trans);
 }
 
 static void seq_overwrite(struct bch_fs *c, u64 nr)
diff --git a/libbcachefs/xattr.c b/libbcachefs/xattr.c
index b204b53b..5ba52a3f 100644
--- a/libbcachefs/xattr.c
+++ b/libbcachefs/xattr.c
@@ -270,12 +270,16 @@ ssize_t bch2_xattr_list(struct dentry *dentry, char *buffer, size_t buffer_size)
 {
 	struct bch_fs *c = dentry->d_sb->s_fs_info;
 	struct bch_inode_info *inode = to_bch_ei(dentry->d_inode);
-	struct btree_iter iter;
+	struct btree_trans trans;
+	struct btree_iter *iter;
 	struct bkey_s_c k;
 	u64 inum = dentry->d_inode->i_ino;
 	ssize_t ret = 0;
 
-	for_each_btree_key(&iter, c, BTREE_ID_XATTRS, POS(inum, 0), 0, k) {
+	bch2_trans_init(&trans, c);
+
+	for_each_btree_key(&trans, iter, BTREE_ID_XATTRS,
+			   POS(inum, 0), 0, k) {
 		BUG_ON(k.k->p.inode < inum);
 
 		if (k.k->p.inode > inum)
@@ -289,7 +293,7 @@ ssize_t bch2_xattr_list(struct dentry *dentry, char *buffer, size_t buffer_size)
 		if (ret < 0)
 			break;
 	}
-	bch2_btree_iter_unlock(&iter);
+	bch2_trans_exit(&trans);
 
 	if (ret < 0)
 		return ret;