X-Git-Url: https://git.sesse.net/?a=blobdiff_plain;f=libbcachefs%2Fbtree_iter.c;h=f430ca83720673043b135128aa75b272a73dfaff;hb=46d51608693bddac162232133516e975f3b1e835;hp=af658390bd679f9dd56de95b1e75c327c896c6eb;hpb=3165f53b28b87b3c46c95763bae5e40a29166e2e;p=bcachefs-tools-debian

diff --git a/libbcachefs/btree_iter.c b/libbcachefs/btree_iter.c
index af65839..f430ca8 100644
--- a/libbcachefs/btree_iter.c
+++ b/libbcachefs/btree_iter.c
@@ -5,6 +5,7 @@
 #include "bkey_buf.h"
 #include "btree_cache.h"
 #include "btree_iter.h"
+#include "btree_journal_iter.h"
 #include "btree_key_cache.h"
 #include "btree_locking.h"
 #include "btree_update.h"
@@ -12,16 +13,12 @@
 #include "error.h"
 #include "extents.h"
 #include "journal.h"
-#include "recovery.h"
 #include "replicas.h"
-#include "subvolume.h"
+#include "snapshot.h"
+#include "trace.h"
 
-#include <linux/prandom.h>
+#include <linux/random.h>
 #include <linux/prefetch.h>
-#include <trace/events/bcachefs.h>
-
-static void btree_trans_verify_sorted(struct btree_trans *);
-inline void bch2_btree_path_check_sort(struct btree_trans *, struct btree_path *, int);
 
 static inline void btree_path_list_remove(struct btree_trans *, struct btree_path *);
 static inline void btree_path_list_add(struct btree_trans *, struct btree_path *,
@@ -29,7 +26,7 @@ static inline void btree_path_list_add(struct btree_trans *, struct btree_path *
 
 static inline unsigned long btree_iter_ip_allocated(struct btree_iter *iter)
 {
-#ifdef CONFIG_BCACHEFS_DEBUG
+#ifdef TRACK_PATH_ALLOCATED
 	return iter->ip_allocated;
 #else
 	return 0;
@@ -38,21 +35,6 @@ static inline unsigned long btree_iter_ip_allocated(struct btree_iter *iter)
 
 static struct btree_path *btree_path_alloc(struct btree_trans *, struct btree_path *);
 
-/*
- * Unlocks before scheduling
- * Note: does not revalidate iterator
- */
-static inline int bch2_trans_cond_resched(struct btree_trans *trans)
-{
-	if (need_resched() || race_fault()) {
-		bch2_trans_unlock(trans);
-		schedule();
-		return bch2_trans_relock(trans);
-	} else {
-		return 0;
-	}
-}
-
 static inline int __btree_path_cmp(const struct btree_path *l,
 				   enum btree_id	r_btree_id,
 				   bool			r_cached,
@@ -105,7 +87,7 @@ static inline struct bpos btree_iter_search_key(struct btree_iter *iter)
 	struct bpos pos = iter->pos;
 
 	if ((iter->flags & BTREE_ITER_IS_EXTENTS) &&
-	    bkey_cmp(pos, POS_MAX))
+	    !bkey_eq(pos, POS_MAX))
 		pos = bkey_successor(iter, pos);
 	return pos;
 }
@@ -113,13 +95,13 @@ static inline struct bpos btree_iter_search_key(struct btree_iter *iter)
 static inline bool btree_path_pos_before_node(struct btree_path *path,
 					      struct btree *b)
 {
-	return bpos_cmp(path->pos, b->data->min_key) < 0;
+	return bpos_lt(path->pos, b->data->min_key);
 }
 
 static inline bool btree_path_pos_after_node(struct btree_path *path,
 					     struct btree *b)
 {
-	return bpos_cmp(b->key.k.p, path->pos) < 0;
+	return bpos_gt(path->pos, b->key.k.p);
 }
 
 static inline bool btree_path_pos_in_node(struct btree_path *path,
@@ -145,7 +127,7 @@ static void bch2_btree_path_verify_cached(struct btree_trans *trans,
 
 	ck = (void *) path->l[0].b;
 	BUG_ON(ck->key.btree_id != path->btree_id ||
-	       bkey_cmp(ck->key.pos, path->pos));
+	       !bkey_eq(ck->key.pos, path->pos));
 
 	if (!locked)
 		btree_node_unlock(trans, path, 0);
@@ -212,6 +194,7 @@ err:
 
 	if (p) {
 		struct bkey uk = bkey_unpack_key(l->b, p);
+
 		bch2_bkey_to_text(&buf2, &uk);
 	} else {
 		prt_printf(&buf2, "(none)");
@@ -219,6 +202,7 @@ err:
 
 	if (k) {
 		struct bkey uk = bkey_unpack_key(l->b, k);
+
 		bch2_bkey_to_text(&buf3, &uk);
 	} else {
 		prt_printf(&buf3, "(none)");
@@ -242,7 +226,7 @@ static void bch2_btree_path_verify(struct btree_trans *trans,
 	for (i = 0; i < (!path->cached ? BTREE_MAX_DEPTH : 1); i++) {
 		if (!path->l[i].b) {
 			BUG_ON(!path->cached &&
-			       c->btree_roots[path->btree_id].b->c.level > i);
+			       bch2_btree_id_root(c, path->btree_id)->b->c.level > i);
 			break;
 		}
 
@@ -273,7 +257,7 @@ static void bch2_btree_iter_verify(struct btree_iter *iter)
 
 	BUG_ON(!(iter->flags & __BTREE_ITER_ALL_SNAPSHOTS) &&
 	       (iter->flags & BTREE_ITER_ALL_SNAPSHOTS) &&
-	       !btree_type_has_snapshots(iter->btree_id));
+	       !btree_type_has_snapshot_field(iter->btree_id));
 
 	if (iter->update_path)
 		bch2_btree_path_verify(trans, iter->update_path);
@@ -288,8 +272,8 @@ static void bch2_btree_iter_verify_entry_exit(struct btree_iter *iter)
 	BUG_ON(!(iter->flags & BTREE_ITER_ALL_SNAPSHOTS) &&
 	       iter->pos.snapshot != iter->snapshot);
 
-	BUG_ON(bkey_cmp(iter->pos, bkey_start_pos(&iter->k)) < 0 ||
-	       bkey_cmp(iter->pos, iter->k.p) > 0);
+	BUG_ON(bkey_lt(iter->pos, bkey_start_pos(&iter->k)) ||
+	       bkey_gt(iter->pos, iter->k.p));
 }
 
 static int bch2_btree_iter_verify_ret(struct btree_iter *iter, struct bkey_s_c k)
@@ -323,7 +307,7 @@ static int bch2_btree_iter_verify_ret(struct btree_iter *iter, struct bkey_s_c k
 	if (ret)
 		goto out;
 
-	if (!bkey_cmp(prev.k->p, k.k->p) &&
+	if (bkey_eq(prev.k->p, k.k->p) &&
 	    bch2_snapshot_is_ancestor(trans->c, iter->snapshot,
 				      prev.k->p.snapshot) > 0) {
 		struct printbuf buf1 = PRINTBUF, buf2 = PRINTBUF;
@@ -349,6 +333,8 @@ void bch2_assert_pos_locked(struct btree_trans *trans, enum btree_id id,
 	unsigned idx;
 	struct printbuf buf = PRINTBUF;
 
+	btree_trans_sort_paths(trans);
+
 	trans_for_each_path_inorder(trans, path, idx) {
 		int cmp = cmp_int(path->btree_id, id) ?:
 			cmp_int(path->cached, key_cache);
@@ -363,11 +349,11 @@ void bch2_assert_pos_locked(struct btree_trans *trans, enum btree_id id,
 			continue;
 
 		if (!key_cache) {
-			if (bkey_cmp(pos, path->l[0].b->data->min_key) >= 0 &&
-			    bkey_cmp(pos, path->l[0].b->key.k.p) <= 0)
+			if (bkey_ge(pos, path->l[0].b->data->min_key) &&
+			    bkey_le(pos, path->l[0].b->key.k.p))
 				return;
 		} else {
-			if (!bkey_cmp(pos, path->pos))
+			if (bkey_eq(pos, path->pos))
 				return;
 		}
 	}
@@ -376,7 +362,7 @@ void bch2_assert_pos_locked(struct btree_trans *trans, enum btree_id id,
 	bch2_bpos_to_text(&buf, pos);
 
 	panic("not locked: %s %s%s\n",
-	      bch2_btree_ids[id], buf.buf,
+	      bch2_btree_id_str(id), buf.buf,
 	      key_cache ? " cached" : "");
 }
 
@@ -502,7 +488,6 @@ fixup_done:
 	if (!bch2_btree_node_iter_end(node_iter) &&
 	    iter_current_key_modified &&
 	    b->c.level) {
-		struct bset_tree *t;
 		struct bkey_packed *k, *k2, *p;
 
 		k = bch2_btree_node_iter_peek_all(node_iter, b);
@@ -536,7 +521,7 @@ void bch2_btree_node_iter_fix(struct btree_trans *trans,
 			      unsigned clobber_u64s,
 			      unsigned new_u64s)
 {
-	struct bset_tree *t = bch2_bkey_to_bset(b, where);
+	struct bset_tree *t = bch2_bkey_to_bset_inlined(b, where);
 	struct btree_path *linked;
 
 	if (node_iter != &path->l[b->c.level].iter) {
@@ -591,6 +576,7 @@ static inline struct bkey_s_c btree_path_level_peek(struct btree_trans *trans,
 			bch2_btree_node_iter_peek(&l->iter, l->b));
 
 	path->pos = k.k ? k.k->p : l->b->key.k.p;
+	trans->paths_sorted = false;
 	bch2_btree_path_verify_level(trans, path, l - path->l);
 	return k;
 }
@@ -604,6 +590,7 @@ static inline struct bkey_s_c btree_path_level_prev(struct btree_trans *trans,
 			bch2_btree_node_iter_prev(&l->iter, l->b));
 
 	path->pos = k.k ? k.k->p : l->b->data->min_key;
+	trans->paths_sorted = false;
 	bch2_btree_path_verify_level(trans, path, l - path->l);
 	return k;
 }
@@ -642,22 +629,47 @@ static inline void __btree_path_level_init(struct btree_path *path,
 		bch2_btree_node_iter_peek(&l->iter, l->b);
 }
 
-inline void bch2_btree_path_level_init(struct btree_trans *trans,
-				       struct btree_path *path,
-				       struct btree *b)
+void bch2_btree_path_level_init(struct btree_trans *trans,
+				struct btree_path *path,
+				struct btree *b)
 {
 	BUG_ON(path->cached);
 
 	EBUG_ON(!btree_path_pos_in_node(path, b));
-	EBUG_ON(b->c.lock.state.seq & 1);
 
-	path->l[b->c.level].lock_seq = b->c.lock.state.seq;
+	path->l[b->c.level].lock_seq = six_lock_seq(&b->c.lock);
 	path->l[b->c.level].b = b;
 	__btree_path_level_init(path, b->c.level);
 }
 
 /* Btree path: fixups after btree node updates: */
 
+static void bch2_trans_revalidate_updates_in_node(struct btree_trans *trans, struct btree *b)
+{
+	struct bch_fs *c = trans->c;
+	struct btree_insert_entry *i;
+
+	trans_for_each_update(trans, i)
+		if (!i->cached &&
+		    i->level	== b->c.level &&
+		    i->btree_id	== b->c.btree_id &&
+		    bpos_cmp(i->k->k.p, b->data->min_key) >= 0 &&
+		    bpos_cmp(i->k->k.p, b->data->max_key) <= 0) {
+			i->old_v = bch2_btree_path_peek_slot(i->path, &i->old_k).v;
+
+			if (unlikely(trans->journal_replay_not_finished)) {
+				struct bkey_i *j_k =
+					bch2_journal_keys_peek_slot(c, i->btree_id, i->level,
+								    i->k->k.p);
+
+				if (j_k) {
+					i->old_k = j_k->k;
+					i->old_v = &j_k->v;
+				}
+			}
+		}
+}
+
 /*
  * A btree node is being replaced - update the iterator to point to the new
  * node:
@@ -675,12 +687,14 @@ void bch2_trans_node_add(struct btree_trans *trans, struct btree *b)
 
 			if (t != BTREE_NODE_UNLOCKED) {
 				btree_node_unlock(trans, path, b->c.level);
-				six_lock_increment(&b->c.lock, t);
+				six_lock_increment(&b->c.lock, (enum six_lock_type) t);
 				mark_btree_node_locked(trans, path, b->c.level, t);
 			}
 
 			bch2_btree_path_level_init(trans, path, b);
 		}
+
+	bch2_trans_revalidate_updates_in_node(trans, b);
 }
 
 /*
@@ -693,6 +707,8 @@ void bch2_trans_node_reinit_iter(struct btree_trans *trans, struct btree *b)
 
 	trans_for_each_path_with_node(trans, b, path)
 		__btree_path_level_init(path, b->c.level);
+
+	bch2_trans_revalidate_updates_in_node(trans, b);
 }
 
 /* Btree path: traverse, set_pos: */
@@ -703,7 +719,7 @@ static inline int btree_path_lock_root(struct btree_trans *trans,
 				       unsigned long trace_ip)
 {
 	struct bch_fs *c = trans->c;
-	struct btree *b, **rootp = &c->btree_roots[path->btree_id].b;
+	struct btree *b, **rootp = &bch2_btree_id_root(c, path->btree_id)->b;
 	enum six_lock_type lock_type;
 	unsigned i;
 	int ret;
@@ -747,7 +763,8 @@ static inline int btree_path_lock_root(struct btree_trans *trans,
 			for (i = path->level + 1; i < BTREE_MAX_DEPTH; i++)
 				path->l[i].b = NULL;
 
-			mark_btree_node_locked(trans, path, path->level, lock_type);
+			mark_btree_node_locked(trans, path, path->level,
+					       (enum btree_node_locked_type) lock_type);
 			bch2_btree_path_level_init(trans, path, b);
 			return 0;
 		}
@@ -764,7 +781,7 @@ static int btree_path_prefetch(struct btree_trans *trans, struct btree_path *pat
 	struct btree_node_iter node_iter = l->iter;
 	struct bkey_packed *k;
 	struct bkey_buf tmp;
-	unsigned nr = test_bit(BCH_FS_STARTED, &c->flags)
+	unsigned nr = test_bit(BCH_FS_started, &c->flags)
 		? (path->level > 1 ? 0 :  2)
 		: (path->level > 1 ? 1 : 16);
 	bool was_locked = btree_node_locked(path, path->level);
@@ -772,7 +789,7 @@ static int btree_path_prefetch(struct btree_trans *trans, struct btree_path *pat
 
 	bch2_bkey_buf_init(&tmp);
 
-	while (nr && !ret) {
+	while (nr-- && !ret) {
 		if (!bch2_btree_node_relock(trans, path, path->level))
 			break;
 
@@ -782,7 +799,7 @@ static int btree_path_prefetch(struct btree_trans *trans, struct btree_path *pat
 			break;
 
 		bch2_bkey_buf_unpack(&tmp, c, l->b, k);
-		ret = bch2_btree_node_prefetch(c, trans, path, tmp.k, path->btree_id,
+		ret = bch2_btree_node_prefetch(trans, path, tmp.k, path->btree_id,
 					       path->level - 1);
 	}
 
@@ -799,7 +816,7 @@ static int btree_path_prefetch_j(struct btree_trans *trans, struct btree_path *p
 	struct bch_fs *c = trans->c;
 	struct bkey_s_c k;
 	struct bkey_buf tmp;
-	unsigned nr = test_bit(BCH_FS_STARTED, &c->flags)
+	unsigned nr = test_bit(BCH_FS_started, &c->flags)
 		? (path->level > 1 ? 0 :  2)
 		: (path->level > 1 ? 1 : 16);
 	bool was_locked = btree_node_locked(path, path->level);
@@ -807,7 +824,7 @@ static int btree_path_prefetch_j(struct btree_trans *trans, struct btree_path *p
 
 	bch2_bkey_buf_init(&tmp);
 
-	while (nr && !ret) {
+	while (nr-- && !ret) {
 		if (!bch2_btree_node_relock(trans, path, path->level))
 			break;
 
@@ -817,7 +834,7 @@ static int btree_path_prefetch_j(struct btree_trans *trans, struct btree_path *p
 			break;
 
 		bch2_bkey_buf_reassemble(&tmp, c, k);
-		ret = bch2_btree_node_prefetch(c, trans, path, tmp.k, path->btree_id,
+		ret = bch2_btree_node_prefetch(trans, path, tmp.k, path->btree_id,
 					       path->level - 1);
 	}
 
@@ -884,7 +901,6 @@ static __always_inline int btree_path_down(struct btree_trans *trans,
 	struct btree *b;
 	unsigned level = path->level - 1;
 	enum six_lock_type lock_type = __btree_lock_want(path, level);
-	bool replay_done = test_bit(JOURNAL_REPLAY_DONE, &c->journal.flags);
 	struct bkey_buf tmp;
 	int ret;
 
@@ -892,7 +908,7 @@ static __always_inline int btree_path_down(struct btree_trans *trans,
 
 	bch2_bkey_buf_init(&tmp);
 
-	if (unlikely(!replay_done)) {
+	if (unlikely(trans->journal_replay_not_finished)) {
 		ret = btree_node_iter_and_journal_peek(trans, path, flags, &tmp);
 		if (ret)
 			goto err;
@@ -912,14 +928,16 @@ static __always_inline int btree_path_down(struct btree_trans *trans,
 	if (unlikely(ret))
 		goto err;
 
-	if (likely(replay_done && tmp.k->k.type == KEY_TYPE_btree_ptr_v2) &&
+	if (likely(!trans->journal_replay_not_finished &&
+		   tmp.k->k.type == KEY_TYPE_btree_ptr_v2) &&
 	    unlikely(b != btree_node_mem_ptr(tmp.k)))
 		btree_node_mem_ptr_set(trans, path, level + 1, b);
 
 	if (btree_node_read_locked(path, level + 1))
 		btree_node_unlock(trans, path, level + 1);
 
-	mark_btree_node_locked(trans, path, level, lock_type);
+	mark_btree_node_locked(trans, path, level,
+			       (enum btree_node_locked_type) lock_type);
 	path->level = level;
 	bch2_btree_path_level_init(trans, path, b);
 
@@ -929,15 +947,13 @@ err:
 	return ret;
 }
 
-static int btree_path_traverse_one(struct btree_trans *, struct btree_path *,
-				   unsigned, unsigned long);
 
 static int bch2_btree_path_traverse_all(struct btree_trans *trans)
 {
 	struct bch_fs *c = trans->c;
 	struct btree_path *path;
 	unsigned long trace_ip = _RET_IP_;
-	int ret = 0;
+	int i, ret = 0;
 
 	if (trans->in_traverse_all)
 		return -BCH_ERR_transaction_restart_in_traverse_all;
@@ -945,12 +961,12 @@ static int bch2_btree_path_traverse_all(struct btree_trans *trans)
 	trans->in_traverse_all = true;
 retry_all:
 	trans->restarted = 0;
-	trans->traverse_all_idx = U8_MAX;
+	trans->last_restarted_ip = 0;
 
 	trans_for_each_path(trans, path)
 		path->should_be_locked = false;
 
-	btree_trans_verify_sorted(trans);
+	btree_trans_sort_paths(trans);
 
 	bch2_trans_unlock(trans);
 	cond_resched();
@@ -967,34 +983,35 @@ retry_all:
 	}
 
 	/* Now, redo traversals in correct order: */
-	trans->traverse_all_idx = 0;
-	while (trans->traverse_all_idx < trans->nr_sorted) {
-		path = trans->paths + trans->sorted[trans->traverse_all_idx];
+	i = 0;
+	while (i < trans->nr_sorted) {
+		path = trans->paths + trans->sorted[i];
 
 		/*
 		 * Traversing a path can cause another path to be added at about
 		 * the same position:
 		 */
 		if (path->uptodate) {
-			ret = btree_path_traverse_one(trans, path, 0, _THIS_IP_);
+			__btree_path_get(path, false);
+			ret = bch2_btree_path_traverse_one(trans, path, 0, _THIS_IP_);
+			__btree_path_put(path, false);
+
 			if (bch2_err_matches(ret, BCH_ERR_transaction_restart) ||
-			    ret == -ENOMEM)
+			    bch2_err_matches(ret, ENOMEM))
 				goto retry_all;
 			if (ret)
 				goto err;
-			BUG_ON(path->uptodate);
 		} else {
-			trans->traverse_all_idx++;
+			i++;
 		}
 	}
 
 	/*
-	 * BTREE_ITER_NEED_RELOCK is ok here - if we called bch2_trans_unlock()
-	 * and relock(), relock() won't relock since path->should_be_locked
-	 * isn't set yet, which is all fine
+	 * We used to assert that all paths had been traversed here
+	 * (path->uptodate < BTREE_ITER_NEED_TRAVERSE); however, since
+	 * path->should_be_locked is not set yet, we might have unlocked and
+	 * then failed to relock a path - that's fine.
 	 */
-	trans_for_each_path(trans, path)
-		BUG_ON(path->uptodate >= BTREE_ITER_NEED_TRAVERSE);
 err:
 	bch2_btree_cache_cannibalize_unlock(c);
 
@@ -1004,14 +1021,9 @@ err:
 	return ret;
 }
 
-static inline bool btree_path_good_node(struct btree_trans *trans,
-					struct btree_path *path,
-					unsigned l, int check_pos)
+static inline bool btree_path_check_pos_in_node(struct btree_path *path,
+						unsigned l, int check_pos)
 {
-	if (!is_btree_node(path, l) ||
-	    !bch2_btree_node_relock(trans, path, l))
-		return false;
-
 	if (check_pos < 0 && btree_path_pos_before_node(path, path->l[l].b))
 		return false;
 	if (check_pos > 0 && btree_path_pos_after_node(path, path->l[l].b))
@@ -1019,6 +1031,15 @@ static inline bool btree_path_good_node(struct btree_trans *trans,
 	return true;
 }
 
+static inline bool btree_path_good_node(struct btree_trans *trans,
+					struct btree_path *path,
+					unsigned l, int check_pos)
+{
+	return is_btree_node(path, l) &&
+		bch2_btree_node_relock(trans, path, l) &&
+		btree_path_check_pos_in_node(path, l, check_pos);
+}
+
 static void btree_path_set_level_down(struct btree_trans *trans,
 				      struct btree_path *path,
 				      unsigned new_level)
@@ -1035,9 +1056,9 @@ static void btree_path_set_level_down(struct btree_trans *trans,
 	bch2_btree_path_verify(trans, path);
 }
 
-static inline unsigned btree_path_up_until_good_node(struct btree_trans *trans,
-						     struct btree_path *path,
-						     int check_pos)
+static noinline unsigned __btree_path_up_until_good_node(struct btree_trans *trans,
+							 struct btree_path *path,
+							 int check_pos)
 {
 	unsigned i, l = path->level;
 again:
@@ -1058,6 +1079,16 @@ again:
 	return l;
 }
 
+static inline unsigned btree_path_up_until_good_node(struct btree_trans *trans,
+						     struct btree_path *path,
+						     int check_pos)
+{
+	return likely(btree_node_locked(path, path->level) &&
+		      btree_path_check_pos_in_node(path, path->level, check_pos))
+		? path->level
+		: __btree_path_up_until_good_node(trans, path, check_pos);
+}
+
 /*
  * This is the main state machine for walking down the btree - walks down to a
  * specified depth
@@ -1067,17 +1098,20 @@ again:
  * On error, caller (peek_node()/peek_key()) must return NULL; the error is
  * stashed in the iterator and returned from bch2_trans_exit().
  */
-static int btree_path_traverse_one(struct btree_trans *trans,
-				   struct btree_path *path,
-				   unsigned flags,
-				   unsigned long trace_ip)
+int bch2_btree_path_traverse_one(struct btree_trans *trans,
+				 struct btree_path *path,
+				 unsigned flags,
+				 unsigned long trace_ip)
 {
 	unsigned depth_want = path->level;
-	int ret = trans->restarted;
+	int ret = -((int) trans->restarted);
 
 	if (unlikely(ret))
 		goto out;
 
+	if (unlikely(!trans->srcu_held))
+		bch2_trans_srcu_lock(trans);
+
 	/*
 	 * Ensure we obey path->should_be_locked: if it's set, we can't unlock
 	 * and re-traverse the path without a transaction restart:
@@ -1129,32 +1163,15 @@ static int btree_path_traverse_one(struct btree_trans *trans,
 
 	path->uptodate = BTREE_ITER_UPTODATE;
 out:
-	BUG_ON(bch2_err_matches(ret, BCH_ERR_transaction_restart) != !!trans->restarted);
+	if (bch2_err_matches(ret, BCH_ERR_transaction_restart) != !!trans->restarted)
+		panic("ret %s (%i) trans->restarted %s (%i)\n",
+		      bch2_err_str(ret), ret,
+		      bch2_err_str(trans->restarted), trans->restarted);
 	bch2_btree_path_verify(trans, path);
 	return ret;
 }
 
-int __must_check bch2_btree_path_traverse(struct btree_trans *trans,
-					  struct btree_path *path, unsigned flags)
-{
-	if (0 && IS_ENABLED(CONFIG_BCACHEFS_DEBUG)) {
-		unsigned restart_probability_bits = 4 << min(trans->restart_count, 32U);
-		u64 mask = ~(~0ULL << restart_probability_bits);
-
-		if ((prandom_u32() & mask) == mask) {
-			trace_and_count(trans->c, trans_restart_injected, trans, _RET_IP_);
-			return btree_trans_restart(trans, BCH_ERR_transaction_restart_fault_inject);
-		}
-	}
-
-	if (path->uptodate < BTREE_ITER_NEED_RELOCK)
-		return 0;
-
-	return  bch2_trans_cond_resched(trans) ?:
-		btree_path_traverse_one(trans, path, flags, _RET_IP_);
-}
-
-static void btree_path_copy(struct btree_trans *trans, struct btree_path *dst,
+static inline void btree_path_copy(struct btree_trans *trans, struct btree_path *dst,
 			    struct btree_path *src)
 {
 	unsigned i, offset = offsetof(struct btree_path, pos);
@@ -1163,12 +1180,12 @@ static void btree_path_copy(struct btree_trans *trans, struct btree_path *dst,
 	       (void *) src + offset,
 	       sizeof(struct btree_path) - offset);
 
-	for (i = 0; i < BTREE_MAX_DEPTH; i++)
-		if (btree_node_locked(dst, i))
-			six_lock_increment(&dst->l[i].b->c.lock,
-					   __btree_lock_want(dst, i));
+	for (i = 0; i < BTREE_MAX_DEPTH; i++) {
+		unsigned t = btree_node_locked_type(dst, i);
 
-	bch2_btree_path_check_sort(trans, dst, 0);
+		if (t != BTREE_NODE_UNLOCKED)
+			six_lock_increment(&dst->l[i].b->c.lock, t);
+	}
 }
 
 static struct btree_path *btree_path_clone(struct btree_trans *trans, struct btree_path *src,
@@ -1181,44 +1198,29 @@ static struct btree_path *btree_path_clone(struct btree_trans *trans, struct btr
 	return new;
 }
 
-inline struct btree_path * __must_check
-bch2_btree_path_make_mut(struct btree_trans *trans,
+__flatten
+struct btree_path *__bch2_btree_path_make_mut(struct btree_trans *trans,
 			 struct btree_path *path, bool intent,
 			 unsigned long ip)
 {
-	if (path->ref > 1 || path->preserve) {
-		__btree_path_put(path, intent);
-		path = btree_path_clone(trans, path, intent);
-		path->preserve = false;
-#ifdef CONFIG_BCACHEFS_DEBUG
-		path->ip_allocated = ip;
-#endif
-		btree_trans_verify_sorted(trans);
-	}
-
-	path->should_be_locked = false;
+	__btree_path_put(path, intent);
+	path = btree_path_clone(trans, path, intent);
+	path->preserve = false;
 	return path;
 }
 
 struct btree_path * __must_check
-bch2_btree_path_set_pos(struct btree_trans *trans,
+__bch2_btree_path_set_pos(struct btree_trans *trans,
 		   struct btree_path *path, struct bpos new_pos,
-		   bool intent, unsigned long ip)
+		   bool intent, unsigned long ip, int cmp)
 {
-	int cmp = bpos_cmp(new_pos, path->pos);
-	unsigned l = path->level;
-
-	EBUG_ON(trans->restarted);
+	bch2_trans_verify_not_in_restart(trans);
 	EBUG_ON(!path->ref);
 
-	if (!cmp)
-		return path;
-
 	path = bch2_btree_path_make_mut(trans, path, intent, ip);
 
-	path->pos = new_pos;
-
-	bch2_btree_path_check_sort(trans, path, cmp);
+	path->pos		= new_pos;
+	trans->paths_sorted	= false;
 
 	if (unlikely(path->cached)) {
 		btree_node_unlock(trans, path, 0);
@@ -1227,10 +1229,12 @@ bch2_btree_path_set_pos(struct btree_trans *trans,
 		goto out;
 	}
 
-	l = btree_path_up_until_good_node(trans, path, cmp);
+	unsigned level = btree_path_up_until_good_node(trans, path, cmp);
 
-	if (btree_path_node(path, l)) {
-		BUG_ON(!btree_node_locked(path, l));
+	if (btree_path_node(path, level)) {
+		struct btree_path_level *l = &path->l[level];
+
+		BUG_ON(!btree_node_locked(path, level));
 		/*
 		 * We might have to skip over many keys, or just a few: try
 		 * advancing the node iterator, and if we have to skip over too
@@ -1238,11 +1242,18 @@ bch2_btree_path_set_pos(struct btree_trans *trans,
 		 * is expensive).
 		 */
 		if (cmp < 0 ||
-		    !btree_path_advance_to_pos(path, &path->l[l], 8))
-			__btree_path_level_init(path, l);
+		    !btree_path_advance_to_pos(path, l, 8))
+			bch2_btree_node_iter_init(&l->iter, l->b, &path->pos);
+
+		/*
+		 * Iterators to interior nodes should always be pointed at the first non
+		 * whiteout:
+		 */
+		if (unlikely(level))
+			bch2_btree_node_iter_peek(&l->iter, l->b);
 	}
 
-	if (l != path->level) {
+	if (unlikely(level != path->level)) {
 		btree_path_set_dirty(path, BTREE_ITER_NEED_TRAVERSE);
 		__bch2_btree_path_unlock(trans, path);
 	}
@@ -1332,9 +1343,25 @@ static void bch2_path_put_nokeep(struct btree_trans *trans, struct btree_path *p
 	__bch2_path_free(trans, path);
 }
 
+void __noreturn bch2_trans_restart_error(struct btree_trans *trans, u32 restart_count)
+{
+	panic("trans->restart_count %u, should be %u, last restarted by %pS\n",
+	      trans->restart_count, restart_count,
+	      (void *) trans->last_begin_ip);
+}
+
+void __noreturn bch2_trans_in_restart_error(struct btree_trans *trans)
+{
+	panic("in transaction restart: %s, last restarted by %pS\n",
+	      bch2_err_str(trans->restarted),
+	      (void *) trans->last_restarted_ip);
+}
+
+noinline __cold
 void bch2_trans_updates_to_text(struct printbuf *buf, struct btree_trans *trans)
 {
 	struct btree_insert_entry *i;
+	struct btree_write_buffered_key *wb;
 
 	prt_printf(buf, "transaction updates for %s journal seq %llu",
 	       trans->fn, trans->journal_res.seq);
@@ -1345,7 +1372,7 @@ void bch2_trans_updates_to_text(struct printbuf *buf, struct btree_trans *trans)
 		struct bkey_s_c old = { &i->old_k, i->old_v };
 
 		prt_printf(buf, "update: btree=%s cached=%u %pS",
-		       bch2_btree_ids[i->btree_id],
+		       bch2_btree_id_str(i->btree_id),
 		       i->cached,
 		       (void *) i->ip_allocated);
 		prt_newline(buf);
@@ -1359,6 +1386,17 @@ void bch2_trans_updates_to_text(struct printbuf *buf, struct btree_trans *trans)
 		prt_newline(buf);
 	}
 
+	trans_for_each_wb_update(trans, wb) {
+		prt_printf(buf, "update: btree=%s wb=1 %pS",
+		       bch2_btree_id_str(wb->btree),
+		       (void *) i->ip_allocated);
+		prt_newline(buf);
+
+		prt_printf(buf, "  new ");
+		bch2_bkey_val_to_text(buf, trans->c, bkey_i_to_s_c(&wb->k));
+		prt_newline(buf);
+	}
+
 	printbuf_indent_sub(buf, 2);
 }
 
@@ -1372,50 +1410,71 @@ void bch2_dump_trans_updates(struct btree_trans *trans)
 	printbuf_exit(&buf);
 }
 
+noinline __cold
 void bch2_btree_path_to_text(struct printbuf *out, struct btree_path *path)
 {
 	prt_printf(out, "path: idx %2u ref %u:%u %c %c btree=%s l=%u pos ",
 		   path->idx, path->ref, path->intent_ref,
 		   path->preserve ? 'P' : ' ',
 		   path->should_be_locked ? 'S' : ' ',
-		   bch2_btree_ids[path->btree_id],
+		   bch2_btree_id_str(path->btree_id),
 		   path->level);
 	bch2_bpos_to_text(out, path->pos);
 
 	prt_printf(out, " locks %u", path->nodes_locked);
-#ifdef CONFIG_BCACHEFS_DEBUG
+#ifdef TRACK_PATH_ALLOCATED
 	prt_printf(out, " %pS", (void *) path->ip_allocated);
 #endif
 	prt_newline(out);
 }
 
-void bch2_trans_paths_to_text(struct printbuf *out, struct btree_trans *trans)
+static noinline __cold
+void __bch2_trans_paths_to_text(struct printbuf *out, struct btree_trans *trans,
+				bool nosort)
 {
 	struct btree_path *path;
 	unsigned idx;
 
+	if (!nosort)
+		btree_trans_sort_paths(trans);
+
 	trans_for_each_path_inorder(trans, path, idx)
 		bch2_btree_path_to_text(out, path);
 }
 
 noinline __cold
-void bch2_dump_trans_paths_updates(struct btree_trans *trans)
+void bch2_trans_paths_to_text(struct printbuf *out, struct btree_trans *trans)
+{
+	__bch2_trans_paths_to_text(out, trans, false);
+}
+
+static noinline __cold
+void __bch2_dump_trans_paths_updates(struct btree_trans *trans, bool nosort)
 {
 	struct printbuf buf = PRINTBUF;
 
-	bch2_trans_paths_to_text(&buf, trans);
+	__bch2_trans_paths_to_text(&buf, trans, nosort);
 	bch2_trans_updates_to_text(&buf, trans);
 
 	bch2_print_string_as_lines(KERN_ERR, buf.buf);
 	printbuf_exit(&buf);
 }
 
-noinline
+noinline __cold
+void bch2_dump_trans_paths_updates(struct btree_trans *trans)
+{
+	__bch2_dump_trans_paths_updates(trans, false);
+}
+
+noinline __cold
 static void bch2_trans_update_max_paths(struct btree_trans *trans)
 {
 	struct btree_transaction_stats *s = btree_trans_stats(trans);
 	struct printbuf buf = PRINTBUF;
 
+	if (!s)
+		return;
+
 	bch2_trans_paths_to_text(&buf, trans);
 
 	if (!buf.allocation_failure) {
@@ -1429,12 +1488,30 @@ static void bch2_trans_update_max_paths(struct btree_trans *trans)
 	}
 
 	printbuf_exit(&buf);
+
+	trans->nr_max_paths = hweight64(trans->paths_allocated);
+}
+
+noinline __cold
+int __bch2_btree_trans_too_many_iters(struct btree_trans *trans)
+{
+	if (trace_trans_restart_too_many_iters_enabled()) {
+		struct printbuf buf = PRINTBUF;
+
+		bch2_trans_paths_to_text(&buf, trans);
+		trace_trans_restart_too_many_iters(trans, _THIS_IP_, buf.buf);
+		printbuf_exit(&buf);
+	}
+
+	count_event(trans->c, trans_restart_too_many_iters);
+
+	return btree_trans_restart(trans, BCH_ERR_transaction_restart_too_many_iters);
 }
 
 static noinline void btree_path_overflow(struct btree_trans *trans)
 {
 	bch2_dump_trans_paths_updates(trans);
-	panic("trans path oveflow\n");
+	panic("trans path overflow\n");
 }
 
 static inline struct btree_path *btree_path_alloc(struct btree_trans *trans,
@@ -1448,19 +1525,25 @@ static inline struct btree_path *btree_path_alloc(struct btree_trans *trans,
 		btree_path_overflow(trans);
 
 	idx = __ffs64(~trans->paths_allocated);
-	trans->paths_allocated |= 1ULL << idx;
 
+	/*
+	 * Do this before marking the new path as allocated, since it won't be
+	 * initialized yet:
+	 */
 	if (unlikely(idx > trans->nr_max_paths))
 		bch2_trans_update_max_paths(trans);
 
-	path = &trans->paths[idx];
+	trans->paths_allocated |= 1ULL << idx;
 
+	path = &trans->paths[idx];
 	path->idx		= idx;
 	path->ref		= 0;
 	path->intent_ref	= 0;
 	path->nodes_locked	= 0;
+	path->alloc_seq++;
 
 	btree_path_list_add(trans, pos, path);
+	trans->paths_sorted = false;
 	return path;
 }
 
@@ -1474,10 +1557,11 @@ struct btree_path *bch2_path_get(struct btree_trans *trans,
 	bool intent = flags & BTREE_ITER_INTENT;
 	int i;
 
-	BUG_ON(trans->restarted);
-	btree_trans_verify_sorted(trans);
+	bch2_trans_verify_not_in_restart(trans);
 	bch2_trans_verify_locks(trans);
 
+	btree_trans_sort_paths(trans);
+
 	trans_for_each_path_inorder(trans, path, i) {
 		if (__btree_path_cmp(path,
 				     btree_id,
@@ -1510,10 +1594,10 @@ struct btree_path *bch2_path_get(struct btree_trans *trans,
 		path->nodes_locked		= 0;
 		for (i = 0; i < ARRAY_SIZE(path->l); i++)
 			path->l[i].b		= ERR_PTR(-BCH_ERR_no_btree_node_init);
-#ifdef CONFIG_BCACHEFS_DEBUG
+#ifdef TRACK_PATH_ALLOCATED
 		path->ip_allocated		= ip;
 #endif
-		btree_trans_verify_sorted(trans);
+		trans->paths_sorted		= false;
 	}
 
 	if (!(flags & BTREE_ITER_NOPRESERVE))
@@ -1532,12 +1616,12 @@ struct btree_path *bch2_path_get(struct btree_trans *trans,
 
 	locks_want = min(locks_want, BTREE_MAX_DEPTH);
 	if (locks_want > path->locks_want)
-		bch2_btree_path_upgrade_noupgrade_sibs(trans, path, locks_want);
+		bch2_btree_path_upgrade_noupgrade_sibs(trans, path, locks_want, NULL);
 
 	return path;
 }
 
-inline struct bkey_s_c bch2_btree_path_peek_slot(struct btree_path *path, struct bkey *u)
+struct bkey_s_c bch2_btree_path_peek_slot(struct btree_path *path, struct bkey *u)
 {
 
 	struct btree_path_level *l = path_l(path);
@@ -1554,17 +1638,18 @@ inline struct bkey_s_c bch2_btree_path_peek_slot(struct btree_path *path, struct
 		_k = bch2_btree_node_iter_peek_all(&l->iter, l->b);
 		k = _k ? bkey_disassemble(l->b, _k, u) : bkey_s_c_null;
 
-		EBUG_ON(k.k && bkey_deleted(k.k) && bpos_cmp(k.k->p, path->pos) == 0);
+		EBUG_ON(k.k && bkey_deleted(k.k) && bpos_eq(k.k->p, path->pos));
 
-		if (!k.k || bpos_cmp(path->pos, k.k->p))
+		if (!k.k || !bpos_eq(path->pos, k.k->p))
 			goto hole;
 	} else {
 		struct bkey_cached *ck = (void *) path->l[0].b;
 
 		EBUG_ON(ck &&
 			(path->btree_id != ck->key.btree_id ||
-			 bkey_cmp(path->pos, ck->key.pos)));
-		EBUG_ON(!ck || !ck->valid);
+			 !bkey_eq(path->pos, ck->key.pos)));
+		if (!ck || !ck->valid)
+			return bkey_s_c_null;
 
 		*u = ck->k->k;
 		k = bkey_i_to_s_c(ck->k);
@@ -1622,7 +1707,7 @@ struct btree *bch2_btree_iter_peek_node(struct btree_iter *iter)
 	if (!b)
 		goto out;
 
-	BUG_ON(bpos_cmp(b->key.k.p, iter->pos) < 0);
+	BUG_ON(bpos_lt(b->key.k.p, iter->pos));
 
 	bkey_init(&iter->k);
 	iter->k.p = iter->pos = b->key.k.p;
@@ -1641,6 +1726,17 @@ err:
 	goto out;
 }
 
+struct btree *bch2_btree_iter_peek_node_and_restart(struct btree_iter *iter)
+{
+	struct btree *b;
+
+	while (b = bch2_btree_iter_peek_node(iter),
+	       bch2_err_matches(PTR_ERR_OR_ZERO(b), BCH_ERR_transaction_restart))
+		bch2_trans_begin(iter->trans);
+
+	return b;
+}
+
 struct btree *bch2_btree_iter_next_node(struct btree_iter *iter)
 {
 	struct btree_trans *trans = iter->trans;
@@ -1648,7 +1744,7 @@ struct btree *bch2_btree_iter_next_node(struct btree_iter *iter)
 	struct btree *b = NULL;
 	int ret;
 
-	BUG_ON(trans->restarted);
+	bch2_trans_verify_not_in_restart(trans);
 	EBUG_ON(iter->path->cached);
 	bch2_btree_iter_verify(iter);
 
@@ -1674,7 +1770,7 @@ struct btree *bch2_btree_iter_next_node(struct btree_iter *iter)
 
 	b = btree_path_node(path, path->level + 1);
 
-	if (!bpos_cmp(iter->pos, b->key.k.p)) {
+	if (bpos_eq(iter->pos, b->key.k.p)) {
 		__btree_path_set_level_up(trans, path, path->level++);
 	} else {
 		/*
@@ -1717,31 +1813,23 @@ err:
 
 inline bool bch2_btree_iter_advance(struct btree_iter *iter)
 {
-	if (likely(!(iter->flags & BTREE_ITER_ALL_LEVELS))) {
-		struct bpos pos = iter->k.p;
-		bool ret = (iter->flags & BTREE_ITER_ALL_SNAPSHOTS
-			    ? bpos_cmp(pos, SPOS_MAX)
-			    : bkey_cmp(pos, SPOS_MAX)) != 0;
+	struct bpos pos = iter->k.p;
+	bool ret = !(iter->flags & BTREE_ITER_ALL_SNAPSHOTS
+		     ? bpos_eq(pos, SPOS_MAX)
+		     : bkey_eq(pos, SPOS_MAX));
 
-		if (ret && !(iter->flags & BTREE_ITER_IS_EXTENTS))
-			pos = bkey_successor(iter, pos);
-		bch2_btree_iter_set_pos(iter, pos);
-		return ret;
-	} else {
-		if (!btree_path_node(iter->path, iter->path->level))
-			return true;
-
-		iter->advanced = true;
-		return false;
-	}
+	if (ret && !(iter->flags & BTREE_ITER_IS_EXTENTS))
+		pos = bkey_successor(iter, pos);
+	bch2_btree_iter_set_pos(iter, pos);
+	return ret;
 }
 
 inline bool bch2_btree_iter_rewind(struct btree_iter *iter)
 {
 	struct bpos pos = bkey_start_pos(&iter->k);
-	bool ret = (iter->flags & BTREE_ITER_ALL_SNAPSHOTS
-		    ? bpos_cmp(pos, POS_MIN)
-		    : bkey_cmp(pos, POS_MIN)) != 0;
+	bool ret = !(iter->flags & BTREE_ITER_ALL_SNAPSHOTS
+		     ? bpos_eq(pos, POS_MIN)
+		     : bkey_eq(pos, POS_MIN));
 
 	if (ret && !(iter->flags & BTREE_ITER_IS_EXTENTS))
 		pos = bkey_predecessor(iter, pos);
@@ -1749,52 +1837,58 @@ inline bool bch2_btree_iter_rewind(struct btree_iter *iter)
 	return ret;
 }
 
-static inline struct bkey_i *btree_trans_peek_updates(struct btree_trans *trans,
-						      enum btree_id btree_id,
-						      struct bpos pos)
+static noinline
+struct bkey_i *__bch2_btree_trans_peek_updates(struct btree_iter *iter)
 {
 	struct btree_insert_entry *i;
 	struct bkey_i *ret = NULL;
 
-	trans_for_each_update(trans, i) {
-		if (i->btree_id < btree_id)
+	trans_for_each_update(iter->trans, i) {
+		if (i->btree_id < iter->btree_id)
 			continue;
-		if (i->btree_id > btree_id)
+		if (i->btree_id > iter->btree_id)
 			break;
-		if (bpos_cmp(i->k->k.p, pos) < 0)
+		if (bpos_lt(i->k->k.p, iter->path->pos))
 			continue;
 		if (i->key_cache_already_flushed)
 			continue;
-		if (!ret || bpos_cmp(i->k->k.p, ret->k.p) < 0)
+		if (!ret || bpos_lt(i->k->k.p, ret->k.p))
 			ret = i->k;
 	}
 
 	return ret;
 }
 
-struct bkey_i *bch2_btree_journal_peek(struct btree_trans *trans,
-				       struct btree_iter *iter,
-				       struct bpos start_pos,
-				       struct bpos end_pos)
+static inline struct bkey_i *btree_trans_peek_updates(struct btree_iter *iter)
 {
-	struct bkey_i *k;
-
-	if (bpos_cmp(start_pos, iter->journal_pos) < 0)
-		iter->journal_idx = 0;
-
-	k = bch2_journal_keys_peek_upto(trans->c, iter->btree_id, 0,
-					start_pos, end_pos,
-					&iter->journal_idx);
+	return iter->flags & BTREE_ITER_WITH_UPDATES
+		? __bch2_btree_trans_peek_updates(iter)
+		: NULL;
+}
 
-	iter->journal_pos = k ? k->k.p : end_pos;
-	return k;
+static struct bkey_i *bch2_btree_journal_peek(struct btree_trans *trans,
+					      struct btree_iter *iter,
+					      struct bpos end_pos)
+{
+	return bch2_journal_keys_peek_upto(trans->c, iter->btree_id,
+					   iter->path->level,
+					   iter->path->pos,
+					   end_pos,
+					   &iter->journal_idx);
 }
 
-struct bkey_i *bch2_btree_journal_peek_slot(struct btree_trans *trans,
-					    struct btree_iter *iter,
-					    struct bpos pos)
+static noinline
+struct bkey_s_c btree_trans_peek_slot_journal(struct btree_trans *trans,
+					      struct btree_iter *iter)
 {
-	return bch2_btree_journal_peek(trans, iter, pos, pos);
+	struct bkey_i *k = bch2_btree_journal_peek(trans, iter, iter->path->pos);
+
+	if (k) {
+		iter->k = k->k;
+		return bkey_i_to_s_c(k);
+	} else {
+		return bkey_s_c_null;
+	}
 }
 
 static noinline
@@ -1803,8 +1897,8 @@ struct bkey_s_c btree_trans_peek_journal(struct btree_trans *trans,
 					 struct bkey_s_c k)
 {
 	struct bkey_i *next_journal =
-		bch2_btree_journal_peek(trans, iter, iter->path->pos,
-				k.k ? k.k->p : iter->path->l[0].b->key.k.p);
+		bch2_btree_journal_peek(trans, iter,
+				k.k ? k.k->p : path_l(iter->path)->b->key.k.p);
 
 	if (next_journal) {
 		iter->k = next_journal->k;
@@ -1819,42 +1913,46 @@ struct bkey_s_c btree_trans_peek_journal(struct btree_trans *trans,
  * bkey_s_c_null:
  */
 static noinline
-struct bkey_s_c __btree_trans_peek_key_cache(struct btree_iter *iter, struct bpos pos)
+struct bkey_s_c btree_trans_peek_key_cache(struct btree_iter *iter, struct bpos pos)
 {
 	struct btree_trans *trans = iter->trans;
 	struct bch_fs *c = trans->c;
 	struct bkey u;
+	struct bkey_s_c k;
 	int ret;
 
+	if ((iter->flags & BTREE_ITER_KEY_CACHE_FILL) &&
+	    bpos_eq(iter->pos, pos))
+		return bkey_s_c_null;
+
 	if (!bch2_btree_key_cache_find(c, iter->btree_id, pos))
 		return bkey_s_c_null;
 
 	if (!iter->key_cache_path)
 		iter->key_cache_path = bch2_path_get(trans, iter->btree_id, pos,
 						     iter->flags & BTREE_ITER_INTENT, 0,
-						     iter->flags|BTREE_ITER_CACHED,
+						     iter->flags|BTREE_ITER_CACHED|
+						     BTREE_ITER_CACHED_NOFILL,
 						     _THIS_IP_);
 
 	iter->key_cache_path = bch2_btree_path_set_pos(trans, iter->key_cache_path, pos,
 					iter->flags & BTREE_ITER_INTENT,
 					btree_iter_ip_allocated(iter));
 
-	ret = bch2_btree_path_traverse(trans, iter->key_cache_path, iter->flags|BTREE_ITER_CACHED);
+	ret =   bch2_btree_path_traverse(trans, iter->key_cache_path,
+					 iter->flags|BTREE_ITER_CACHED) ?:
+		bch2_btree_path_relock(trans, iter->path, _THIS_IP_);
 	if (unlikely(ret))
 		return bkey_s_c_err(ret);
 
 	btree_path_set_should_be_locked(iter->key_cache_path);
 
-	return bch2_btree_path_peek_slot(iter->key_cache_path, &u);
-}
-
-static noinline
-struct bkey_s_c btree_trans_peek_key_cache(struct btree_iter *iter, struct bpos pos)
-{
-	struct bkey_s_c ret = __btree_trans_peek_key_cache(iter, pos);
-	int err = bkey_err(ret) ?: bch2_btree_path_relock(iter->trans, iter->path, _THIS_IP_);
-
-	return err ? bkey_s_c_err(err) : ret;
+	k = bch2_btree_path_peek_slot(iter->key_cache_path, &u);
+	if (k.k && !bkey_err(k)) {
+		iter->k = u;
+		k.k = &iter->k;
+	}
+	return k;
 }
 
 static struct bkey_s_c __bch2_btree_iter_peek(struct btree_iter *iter, struct bpos search_key)
@@ -1909,12 +2007,11 @@ static struct bkey_s_c __bch2_btree_iter_peek(struct btree_iter *iter, struct bp
 		if (unlikely(iter->flags & BTREE_ITER_WITH_JOURNAL))
 			k = btree_trans_peek_journal(trans, iter, k);
 
-		next_update = iter->flags & BTREE_ITER_WITH_UPDATES
-			? btree_trans_peek_updates(trans, iter->btree_id, search_key)
-			: NULL;
+		next_update = btree_trans_peek_updates(iter);
+
 		if (next_update &&
-		    bpos_cmp(next_update->k.p,
-			     k.k ? k.k->p : l->b->key.k.p) <= 0) {
+		    bpos_le(next_update->k.p,
+			    k.k ? k.k->p : l->b->key.k.p)) {
 			iter->k = next_update->k;
 			k = bkey_i_to_s_c(next_update);
 		}
@@ -1927,7 +2024,7 @@ static struct bkey_s_c __bch2_btree_iter_peek(struct btree_iter *iter, struct bp
 			 * whiteout, with a real key at the same position, since
 			 * in the btree deleted keys sort before non deleted.
 			 */
-			search_key = bpos_cmp(search_key, k.k->p)
+			search_key = !bpos_eq(search_key, k.k->p)
 				? k.k->p
 				: bpos_successor(k.k->p);
 			continue;
@@ -1935,7 +2032,7 @@ static struct bkey_s_c __bch2_btree_iter_peek(struct btree_iter *iter, struct bp
 
 		if (likely(k.k)) {
 			break;
-		} else if (likely(bpos_cmp(l->b->key.k.p, SPOS_MAX))) {
+		} else if (likely(!bpos_eq(l->b->key.k.p, SPOS_MAX))) {
 			/* Advance to next leaf node: */
 			search_key = bpos_successor(l->b->key.k.p);
 		} else {
@@ -1952,8 +2049,12 @@ out:
 }
 
 /**
- * bch2_btree_iter_peek: returns first key greater than or equal to iterator's
- * current position
+ * bch2_btree_iter_peek_upto() - returns first key greater than or equal to
+ * iterator's current position
+ * @iter:	iterator to peek from
+ * @end:	search limit: returns keys less than or equal to @end
+ *
+ * Returns:	key if found, or an error extractable with bkey_err().
  */
 struct bkey_s_c bch2_btree_iter_peek_upto(struct btree_iter *iter, struct bpos end)
 {
@@ -1963,7 +2064,7 @@ struct bkey_s_c bch2_btree_iter_peek_upto(struct btree_iter *iter, struct bpos e
 	struct bpos iter_pos;
 	int ret;
 
-	EBUG_ON(iter->flags & BTREE_ITER_ALL_LEVELS);
+	EBUG_ON((iter->flags & BTREE_ITER_FILTER_SNAPSHOTS) && bkey_eq(end, POS_MAX));
 
 	if (iter->update_path) {
 		bch2_path_put_nokeep(trans, iter->update_path,
@@ -1975,7 +2076,9 @@ struct bkey_s_c bch2_btree_iter_peek_upto(struct btree_iter *iter, struct bpos e
 
 	while (1) {
 		k = __bch2_btree_iter_peek(iter, search_key);
-		if (!k.k || bkey_err(k))
+		if (unlikely(!k.k))
+			goto end;
+		if (unlikely(bkey_err(k)))
 			goto out_no_locked;
 
 		/*
@@ -1985,19 +2088,16 @@ struct bkey_s_c bch2_btree_iter_peek_upto(struct btree_iter *iter, struct bpos e
 		 */
 		if (!(iter->flags & BTREE_ITER_IS_EXTENTS))
 			iter_pos = k.k->p;
-		else if (bkey_cmp(bkey_start_pos(k.k), iter->pos) > 0)
-			iter_pos = bkey_start_pos(k.k);
 		else
-			iter_pos = iter->pos;
+			iter_pos = bkey_max(iter->pos, bkey_start_pos(k.k));
 
-		if (bkey_cmp(iter_pos, end) > 0) {
-			bch2_btree_iter_set_pos(iter, end);
-			k = bkey_s_c_null;
-			goto out_no_locked;
-		}
+		if (unlikely(!(iter->flags & BTREE_ITER_IS_EXTENTS)
+			     ? bkey_gt(iter_pos, end)
+			     : bkey_ge(iter_pos, end)))
+			goto end;
 
 		if (iter->update_path &&
-		    bkey_cmp(iter->update_path->pos, k.k->p)) {
+		    !bkey_eq(iter->update_path->pos, k.k->p)) {
 			bch2_path_put_nokeep(trans, iter->update_path,
 					     iter->flags & BTREE_ITER_INTENT);
 			iter->update_path = NULL;
@@ -2027,6 +2127,11 @@ struct bkey_s_c bch2_btree_iter_peek_upto(struct btree_iter *iter, struct bpos e
 						iter->update_path, pos,
 						iter->flags & BTREE_ITER_INTENT,
 						_THIS_IP_);
+			ret = bch2_btree_path_traverse(trans, iter->update_path, iter->flags);
+			if (unlikely(ret)) {
+				k = bkey_s_c_err(ret);
+				goto out_no_locked;
+			}
 		}
 
 		/*
@@ -2059,8 +2164,8 @@ struct bkey_s_c bch2_btree_iter_peek_upto(struct btree_iter *iter, struct bpos e
 	btree_path_set_should_be_locked(iter->path);
 out_no_locked:
 	if (iter->update_path) {
-		if (iter->update_path->uptodate &&
-		    (ret = bch2_btree_path_relock(trans, iter->update_path, _THIS_IP_)))
+		ret = bch2_btree_path_relock(trans, iter->update_path, _THIS_IP_);
+		if (unlikely(ret))
 			k = bkey_s_c_err(ret);
 		else
 			btree_path_set_should_be_locked(iter->update_path);
@@ -2078,105 +2183,18 @@ out_no_locked:
 	bch2_btree_iter_verify_entry_exit(iter);
 
 	return k;
+end:
+	bch2_btree_iter_set_pos(iter, end);
+	k = bkey_s_c_null;
+	goto out_no_locked;
 }
 
 /**
- * bch2_btree_iter_peek_all_levels: returns the first key greater than or equal
- * to iterator's current position, returning keys from every level of the btree.
- * For keys at different levels of the btree that compare equal, the key from
- * the lower level (leaf) is returned first.
- */
-struct bkey_s_c bch2_btree_iter_peek_all_levels(struct btree_iter *iter)
-{
-	struct btree_trans *trans = iter->trans;
-	struct bkey_s_c k;
-	int ret;
-
-	EBUG_ON(iter->path->cached);
-	bch2_btree_iter_verify(iter);
-	BUG_ON(iter->path->level < iter->min_depth);
-	BUG_ON(!(iter->flags & BTREE_ITER_ALL_SNAPSHOTS));
-	EBUG_ON(!(iter->flags & BTREE_ITER_ALL_LEVELS));
-
-	while (1) {
-		iter->path = bch2_btree_path_set_pos(trans, iter->path, iter->pos,
-					iter->flags & BTREE_ITER_INTENT,
-					btree_iter_ip_allocated(iter));
-
-		ret = bch2_btree_path_traverse(trans, iter->path, iter->flags);
-		if (unlikely(ret)) {
-			/* ensure that iter->k is consistent with iter->pos: */
-			bch2_btree_iter_set_pos(iter, iter->pos);
-			k = bkey_s_c_err(ret);
-			goto out_no_locked;
-		}
-
-		/* Already at end? */
-		if (!btree_path_node(iter->path, iter->path->level)) {
-			k = bkey_s_c_null;
-			goto out_no_locked;
-		}
-
-		k = btree_path_level_peek_all(trans->c,
-				&iter->path->l[iter->path->level], &iter->k);
-
-		/* Check if we should go up to the parent node: */
-		if (!k.k ||
-		    (iter->advanced &&
-		     !bpos_cmp(path_l(iter->path)->b->key.k.p, iter->pos))) {
-			iter->pos = path_l(iter->path)->b->key.k.p;
-			btree_path_set_level_up(trans, iter->path);
-			iter->advanced = false;
-			continue;
-		}
-
-		/*
-		 * Check if we should go back down to a leaf:
-		 * If we're not in a leaf node, we only return the current key
-		 * if it exactly matches iter->pos - otherwise we first have to
-		 * go back to the leaf:
-		 */
-		if (iter->path->level != iter->min_depth &&
-		    (iter->advanced ||
-		     !k.k ||
-		     bpos_cmp(iter->pos, k.k->p))) {
-			btree_path_set_level_down(trans, iter->path, iter->min_depth);
-			iter->pos = bpos_successor(iter->pos);
-			iter->advanced = false;
-			continue;
-		}
-
-		/* Check if we should go to the next key: */
-		if (iter->path->level == iter->min_depth &&
-		    iter->advanced &&
-		    k.k &&
-		    !bpos_cmp(iter->pos, k.k->p)) {
-			iter->pos = bpos_successor(iter->pos);
-			iter->advanced = false;
-			continue;
-		}
-
-		if (iter->advanced &&
-		    iter->path->level == iter->min_depth &&
-		    bpos_cmp(k.k->p, iter->pos))
-			iter->advanced = false;
-
-		BUG_ON(iter->advanced);
-		BUG_ON(!k.k);
-		break;
-	}
-
-	iter->pos = k.k->p;
-	btree_path_set_should_be_locked(iter->path);
-out_no_locked:
-	bch2_btree_iter_verify(iter);
-
-	return k;
-}
-
-/**
- * bch2_btree_iter_next: returns first key greater than iterator's current
+ * bch2_btree_iter_next() - returns first key greater than iterator's current
  * position
+ * @iter:	iterator to peek from
+ *
+ * Returns:	key if found, or an error extractable with bkey_err().
  */
 struct bkey_s_c bch2_btree_iter_next(struct btree_iter *iter)
 {
@@ -2187,8 +2205,11 @@ struct bkey_s_c bch2_btree_iter_next(struct btree_iter *iter)
 }
 
 /**
- * bch2_btree_iter_peek_prev: returns first key less than or equal to
+ * bch2_btree_iter_peek_prev() - returns first key less than or equal to
  * iterator's current position
+ * @iter:	iterator to peek from
+ *
+ * Returns:	key if found, or an error extractable with bkey_err().
  */
 struct bkey_s_c bch2_btree_iter_peek_prev(struct btree_iter *iter)
 {
@@ -2229,13 +2250,11 @@ struct bkey_s_c bch2_btree_iter_peek_prev(struct btree_iter *iter)
 					  &iter->path->l[0], &iter->k);
 		if (!k.k ||
 		    ((iter->flags & BTREE_ITER_IS_EXTENTS)
-		     ? bpos_cmp(bkey_start_pos(k.k), search_key) >= 0
-		     : bpos_cmp(k.k->p, search_key) > 0))
+		     ? bpos_ge(bkey_start_pos(k.k), search_key)
+		     : bpos_gt(k.k->p, search_key)))
 			k = btree_path_level_prev(trans, iter->path,
 						  &iter->path->l[0], &iter->k);
 
-		bch2_btree_path_check_sort(trans, iter->path, 0);
-
 		if (likely(k.k)) {
 			if (iter->flags & BTREE_ITER_FILTER_SNAPSHOTS) {
 				if (k.k->p.snapshot == iter->snapshot)
@@ -2246,7 +2265,7 @@ struct bkey_s_c bch2_btree_iter_peek_prev(struct btree_iter *iter)
 				 * longer at the same _key_ (not pos), return
 				 * that candidate
 				 */
-				if (saved_path && bkey_cmp(k.k->p, saved_k.p)) {
+				if (saved_path && !bkey_eq(k.k->p, saved_k.p)) {
 					bch2_path_put_nokeep(trans, iter->path,
 						      iter->flags & BTREE_ITER_INTENT);
 					iter->path = saved_path;
@@ -2281,7 +2300,7 @@ got_key:
 			}
 
 			break;
-		} else if (likely(bpos_cmp(iter->path->l[0].b->data->min_key, POS_MIN))) {
+		} else if (likely(!bpos_eq(iter->path->l[0].b->data->min_key, POS_MIN))) {
 			/* Advance to previous leaf node: */
 			search_key = bpos_predecessor(iter->path->l[0].b->data->min_key);
 		} else {
@@ -2292,10 +2311,10 @@ got_key:
 		}
 	}
 
-	EBUG_ON(bkey_cmp(bkey_start_pos(k.k), iter->pos) > 0);
+	EBUG_ON(bkey_gt(bkey_start_pos(k.k), iter->pos));
 
 	/* Extents can straddle iter->pos: */
-	if (bkey_cmp(k.k->p, iter->pos) < 0)
+	if (bkey_lt(k.k->p, iter->pos))
 		iter->pos = k.k->p;
 
 	if (iter->flags & BTREE_ITER_FILTER_SNAPSHOTS)
@@ -2313,8 +2332,11 @@ out_no_locked:
 }
 
 /**
- * bch2_btree_iter_prev: returns first key less than iterator's current
+ * bch2_btree_iter_prev() - returns first key less than iterator's current
  * position
+ * @iter:	iterator to peek from
+ *
+ * Returns:	key if found, or an error extractable with bkey_err().
  */
 struct bkey_s_c bch2_btree_iter_prev(struct btree_iter *iter)
 {
@@ -2333,7 +2355,6 @@ struct bkey_s_c bch2_btree_iter_peek_slot(struct btree_iter *iter)
 
 	bch2_btree_iter_verify(iter);
 	bch2_btree_iter_verify_entry_exit(iter);
-	EBUG_ON(iter->flags & BTREE_ITER_ALL_LEVELS);
 	EBUG_ON(iter->path->level && (iter->flags & BTREE_ITER_WITH_KEY_CACHE));
 
 	/* extents can't span inode numbers: */
@@ -2360,25 +2381,19 @@ struct bkey_s_c bch2_btree_iter_peek_slot(struct btree_iter *iter)
 	    !(iter->flags & (BTREE_ITER_IS_EXTENTS|BTREE_ITER_FILTER_SNAPSHOTS))) {
 		struct bkey_i *next_update;
 
-		if ((iter->flags & BTREE_ITER_WITH_UPDATES) &&
-		    (next_update = btree_trans_peek_updates(trans,
-						iter->btree_id, search_key)) &&
-		    !bpos_cmp(next_update->k.p, iter->pos)) {
+		if ((next_update = btree_trans_peek_updates(iter)) &&
+		    bpos_eq(next_update->k.p, iter->pos)) {
 			iter->k = next_update->k;
 			k = bkey_i_to_s_c(next_update);
 			goto out;
 		}
 
 		if (unlikely(iter->flags & BTREE_ITER_WITH_JOURNAL) &&
-		    (next_update = bch2_btree_journal_peek_slot(trans,
-					iter, iter->pos))) {
-			iter->k = next_update->k;
-			k = bkey_i_to_s_c(next_update);
+		    (k = btree_trans_peek_slot_journal(trans, iter)).k)
 			goto out;
-		}
 
 		if (unlikely(iter->flags & BTREE_ITER_WITH_KEY_CACHE) &&
-		    (k = __btree_trans_peek_key_cache(iter, iter->pos)).k) {
+		    (k = btree_trans_peek_key_cache(iter, iter->pos)).k) {
 			if (!bkey_err(k))
 				iter->k = *k.k;
 			/* We're not returning a key from iter->path: */
@@ -2386,17 +2401,19 @@ struct bkey_s_c bch2_btree_iter_peek_slot(struct btree_iter *iter)
 		}
 
 		k = bch2_btree_path_peek_slot(iter->path, &iter->k);
+		if (unlikely(!k.k))
+			goto out_no_locked;
 	} else {
 		struct bpos next;
+		struct bpos end = iter->pos;
+
+		if (iter->flags & BTREE_ITER_IS_EXTENTS)
+			end.offset = U64_MAX;
 
 		EBUG_ON(iter->path->level);
 
 		if (iter->flags & BTREE_ITER_INTENT) {
 			struct btree_iter iter2;
-			struct bpos end = iter->pos;
-
-			if (iter->flags & BTREE_ITER_IS_EXTENTS)
-				end.offset = U64_MAX;
 
 			bch2_trans_copy_iter(&iter2, iter);
 			k = bch2_btree_iter_peek_upto(&iter2, end);
@@ -2409,7 +2426,7 @@ struct bkey_s_c bch2_btree_iter_peek_slot(struct btree_iter *iter)
 		} else {
 			struct bpos pos = iter->pos;
 
-			k = bch2_btree_iter_peek(iter);
+			k = bch2_btree_iter_peek_upto(iter, end);
 			if (unlikely(bkey_err(k)))
 				bch2_btree_iter_set_pos(iter, pos);
 			else
@@ -2421,7 +2438,7 @@ struct bkey_s_c bch2_btree_iter_peek_slot(struct btree_iter *iter)
 
 		next = k.k ? bkey_start_pos(k.k) : POS_MAX;
 
-		if (bkey_cmp(iter->pos, next) < 0) {
+		if (bkey_lt(iter->pos, next)) {
 			bkey_init(&iter->k);
 			iter->k.p = iter->pos;
 
@@ -2466,29 +2483,43 @@ struct bkey_s_c bch2_btree_iter_prev_slot(struct btree_iter *iter)
 	return bch2_btree_iter_peek_slot(iter);
 }
 
-/* new transactional stuff: */
-
-static inline void btree_path_verify_sorted_ref(struct btree_trans *trans,
-						struct btree_path *path)
+struct bkey_s_c bch2_btree_iter_peek_and_restart_outlined(struct btree_iter *iter)
 {
-	EBUG_ON(path->sorted_idx >= trans->nr_sorted);
-	EBUG_ON(trans->sorted[path->sorted_idx] != path->idx);
-	EBUG_ON(!(trans->paths_allocated & (1ULL << path->idx)));
+	struct bkey_s_c k;
+
+	while (btree_trans_too_many_iters(iter->trans) ||
+	       (k = bch2_btree_iter_peek_type(iter, iter->flags),
+		bch2_err_matches(bkey_err(k), BCH_ERR_transaction_restart)))
+		bch2_trans_begin(iter->trans);
+
+	return k;
 }
 
-static inline void btree_trans_verify_sorted_refs(struct btree_trans *trans)
-{
+/* new transactional stuff: */
+
 #ifdef CONFIG_BCACHEFS_DEBUG
+static void btree_trans_verify_sorted_refs(struct btree_trans *trans)
+{
+	struct btree_path *path;
 	unsigned i;
 
-	for (i = 0; i < trans->nr_sorted; i++)
-		btree_path_verify_sorted_ref(trans, trans->paths + trans->sorted[i]);
-#endif
+	BUG_ON(trans->nr_sorted != hweight64(trans->paths_allocated));
+
+	trans_for_each_path(trans, path) {
+		BUG_ON(path->sorted_idx >= trans->nr_sorted);
+		BUG_ON(trans->sorted[path->sorted_idx] != path->idx);
+	}
+
+	for (i = 0; i < trans->nr_sorted; i++) {
+		unsigned idx = trans->sorted[i];
+
+		EBUG_ON(!(trans->paths_allocated & (1ULL << idx)));
+		BUG_ON(trans->paths[idx].sorted_idx != i);
+	}
 }
 
 static void btree_trans_verify_sorted(struct btree_trans *trans)
 {
-#ifdef CONFIG_BCACHEFS_DEBUG
 	struct btree_path *path, *prev = NULL;
 	unsigned i;
 
@@ -2497,51 +2528,54 @@ static void btree_trans_verify_sorted(struct btree_trans *trans)
 
 	trans_for_each_path_inorder(trans, path, i) {
 		if (prev && btree_path_cmp(prev, path) > 0) {
-			bch2_dump_trans_paths_updates(trans);
+			__bch2_dump_trans_paths_updates(trans, true);
 			panic("trans paths out of order!\n");
 		}
 		prev = path;
 	}
-#endif
 }
+#else
+static inline void btree_trans_verify_sorted_refs(struct btree_trans *trans) {}
+static inline void btree_trans_verify_sorted(struct btree_trans *trans) {}
+#endif
 
-static inline void btree_path_swap(struct btree_trans *trans,
-				   struct btree_path *l, struct btree_path *r)
+void __bch2_btree_trans_sort_paths(struct btree_trans *trans)
 {
-	swap(l->sorted_idx, r->sorted_idx);
-	swap(trans->sorted[l->sorted_idx],
-	     trans->sorted[r->sorted_idx]);
+	int i, l = 0, r = trans->nr_sorted, inc = 1;
+	bool swapped;
 
-	btree_path_verify_sorted_ref(trans, l);
-	btree_path_verify_sorted_ref(trans, r);
-}
-
-inline void bch2_btree_path_check_sort(struct btree_trans *trans, struct btree_path *path,
-				       int cmp)
-{
-	struct btree_path *n;
+	btree_trans_verify_sorted_refs(trans);
 
-	if (cmp <= 0) {
-		n = prev_btree_path(trans, path);
-		if (n && btree_path_cmp(n, path) > 0) {
-			do {
-				btree_path_swap(trans, n, path);
-				n = prev_btree_path(trans, path);
-			} while (n && btree_path_cmp(n, path) > 0);
+	if (trans->paths_sorted)
+		goto out;
 
-			goto out;
+	/*
+	 * Cocktail shaker sort: this is efficient because iterators will be
+	 * mostly sorted.
+	 */
+	do {
+		swapped = false;
+
+		for (i = inc > 0 ? l : r - 2;
+		     i + 1 < r && i >= l;
+		     i += inc) {
+			if (btree_path_cmp(trans->paths + trans->sorted[i],
+					   trans->paths + trans->sorted[i + 1]) > 0) {
+				swap(trans->sorted[i], trans->sorted[i + 1]);
+				trans->paths[trans->sorted[i]].sorted_idx = i;
+				trans->paths[trans->sorted[i + 1]].sorted_idx = i + 1;
+				swapped = true;
+			}
 		}
-	}
 
-	if (cmp >= 0) {
-		n = next_btree_path(trans, path);
-		if (n && btree_path_cmp(path, n) > 0) {
-			do {
-				btree_path_swap(trans, path, n);
-				n = next_btree_path(trans, path);
-			} while (n && btree_path_cmp(path, n) > 0);
-		}
-	}
+		if (inc > 0)
+			--r;
+		else
+			l++;
+		inc = -inc;
+	} while (swapped);
+
+	trans->paths_sorted = true;
 out:
 	btree_trans_verify_sorted(trans);
 }
@@ -2552,15 +2586,18 @@ static inline void btree_path_list_remove(struct btree_trans *trans,
 	unsigned i;
 
 	EBUG_ON(path->sorted_idx >= trans->nr_sorted);
-
+#ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
+	trans->nr_sorted--;
+	memmove_u64s_down_small(trans->sorted + path->sorted_idx,
+				trans->sorted + path->sorted_idx + 1,
+				DIV_ROUND_UP(trans->nr_sorted - path->sorted_idx, 8));
+#else
 	array_remove_item(trans->sorted, trans->nr_sorted, path->sorted_idx);
-
+#endif
 	for (i = path->sorted_idx; i < trans->nr_sorted; i++)
 		trans->paths[trans->sorted[i]].sorted_idx = i;
 
 	path->sorted_idx = U8_MAX;
-
-	btree_trans_verify_sorted_refs(trans);
 }
 
 static inline void btree_path_list_add(struct btree_trans *trans,
@@ -2569,16 +2606,17 @@ static inline void btree_path_list_add(struct btree_trans *trans,
 {
 	unsigned i;
 
-	btree_trans_verify_sorted_refs(trans);
-
-	path->sorted_idx = pos ? pos->sorted_idx + 1 : 0;
-
-	if (trans->in_traverse_all &&
-	    trans->traverse_all_idx != U8_MAX &&
-	    trans->traverse_all_idx >= path->sorted_idx)
-		trans->traverse_all_idx++;
+	path->sorted_idx = pos ? pos->sorted_idx + 1 : trans->nr_sorted;
 
+#ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
+	memmove_u64s_up_small(trans->sorted + path->sorted_idx + 1,
+			      trans->sorted + path->sorted_idx,
+			      DIV_ROUND_UP(trans->nr_sorted - path->sorted_idx, 8));
+	trans->nr_sorted++;
+	trans->sorted[path->sorted_idx] = path->idx;
+#else
 	array_insert_item(trans->sorted, trans->nr_sorted, path->sorted_idx, path->idx);
+#endif
 
 	for (i = path->sorted_idx; i < trans->nr_sorted; i++)
 		trans->paths[trans->sorted[i]].sorted_idx = i;
@@ -2588,12 +2626,12 @@ static inline void btree_path_list_add(struct btree_trans *trans,
 
 void bch2_trans_iter_exit(struct btree_trans *trans, struct btree_iter *iter)
 {
-	if (iter->path)
-		bch2_path_put(trans, iter->path,
-			      iter->flags & BTREE_ITER_INTENT);
 	if (iter->update_path)
 		bch2_path_put_nokeep(trans, iter->update_path,
 			      iter->flags & BTREE_ITER_INTENT);
+	if (iter->path)
+		bch2_path_put(trans, iter->path,
+			      iter->flags & BTREE_ITER_INTENT);
 	if (iter->key_cache_path)
 		bch2_path_put(trans, iter->key_cache_path,
 			      iter->flags & BTREE_ITER_INTENT);
@@ -2602,72 +2640,14 @@ void bch2_trans_iter_exit(struct btree_trans *trans, struct btree_iter *iter)
 	iter->key_cache_path = NULL;
 }
 
-static inline void __bch2_trans_iter_init(struct btree_trans *trans,
-					  struct btree_iter *iter,
-					  unsigned btree_id, struct bpos pos,
-					  unsigned locks_want,
-					  unsigned depth,
-					  unsigned flags,
-					  unsigned long ip)
-{
-	if (trans->restarted)
-		panic("bch2_trans_iter_init(): in transaction restart, %s by %pS\n",
-		      bch2_err_str(trans->restarted),
-		      (void *) trans->last_restarted_ip);
-
-	if (flags & BTREE_ITER_ALL_LEVELS)
-		flags |= BTREE_ITER_ALL_SNAPSHOTS|__BTREE_ITER_ALL_SNAPSHOTS;
-
-	if (!(flags & (BTREE_ITER_ALL_SNAPSHOTS|BTREE_ITER_NOT_EXTENTS)) &&
-	    btree_node_type_is_extents(btree_id))
-		flags |= BTREE_ITER_IS_EXTENTS;
-
-	if (!(flags & __BTREE_ITER_ALL_SNAPSHOTS) &&
-	    !btree_type_has_snapshots(btree_id))
-		flags &= ~BTREE_ITER_ALL_SNAPSHOTS;
-
-	if (!(flags & BTREE_ITER_ALL_SNAPSHOTS) &&
-	    btree_type_has_snapshots(btree_id))
-		flags |= BTREE_ITER_FILTER_SNAPSHOTS;
-
-	if (!test_bit(JOURNAL_REPLAY_DONE, &trans->c->journal.flags))
-		flags |= BTREE_ITER_WITH_JOURNAL;
-
-	iter->trans	= trans;
-	iter->path	= NULL;
-	iter->update_path = NULL;
-	iter->key_cache_path = NULL;
-	iter->btree_id	= btree_id;
-	iter->min_depth	= depth;
-	iter->flags	= flags;
-	iter->snapshot	= pos.snapshot;
-	iter->pos	= pos;
-	iter->k.type	= KEY_TYPE_deleted;
-	iter->k.p	= pos;
-	iter->k.size	= 0;
-	iter->journal_idx = 0;
-	iter->journal_pos = POS_MIN;
-#ifdef CONFIG_BCACHEFS_DEBUG
-	iter->ip_allocated = ip;
-#endif
-
-	iter->path = bch2_path_get(trans, btree_id, iter->pos,
-				   locks_want, depth, flags, ip);
-}
-
-void bch2_trans_iter_init(struct btree_trans *trans,
+void bch2_trans_iter_init_outlined(struct btree_trans *trans,
 			  struct btree_iter *iter,
-			  unsigned btree_id, struct bpos pos,
+			  enum btree_id btree_id, struct bpos pos,
 			  unsigned flags)
 {
-	if (!btree_id_cached(trans->c, btree_id)) {
-		flags &= ~BTREE_ITER_CACHED;
-		flags &= ~BTREE_ITER_WITH_KEY_CACHE;
-	} else if (!(flags & BTREE_ITER_CACHED))
-		flags |= BTREE_ITER_WITH_KEY_CACHE;
-
-	__bch2_trans_iter_init(trans, iter, btree_id, pos,
-			       0, 0, flags, _RET_IP_);
+	bch2_trans_iter_init_common(trans, iter, btree_id, pos, 0, 0,
+			       bch2_btree_iter_flags(trans, btree_id, flags),
+			       _RET_IP_);
 }
 
 void bch2_trans_node_iter_init(struct btree_trans *trans,
@@ -2678,11 +2658,16 @@ void bch2_trans_node_iter_init(struct btree_trans *trans,
 			       unsigned depth,
 			       unsigned flags)
 {
-	__bch2_trans_iter_init(trans, iter, btree_id, pos, locks_want, depth,
-			       BTREE_ITER_NOT_EXTENTS|
-			       __BTREE_ITER_ALL_SNAPSHOTS|
-			       BTREE_ITER_ALL_SNAPSHOTS|
-			       flags, _RET_IP_);
+	flags |= BTREE_ITER_NOT_EXTENTS;
+	flags |= __BTREE_ITER_ALL_SNAPSHOTS;
+	flags |= BTREE_ITER_ALL_SNAPSHOTS;
+
+	bch2_trans_iter_init_common(trans, iter, btree_id, pos, locks_want, depth,
+			       __bch2_btree_iter_flags(trans, btree_id, flags),
+			       _RET_IP_);
+
+	iter->min_depth	= depth;
+
 	BUG_ON(iter->path->locks_want	 < min(locks_want, BTREE_MAX_DEPTH));
 	BUG_ON(iter->path->level	!= depth);
 	BUG_ON(iter->min_depth		!= depth);
@@ -2703,6 +2688,7 @@ void *__bch2_trans_kmalloc(struct btree_trans *trans, size_t size)
 	unsigned new_top = trans->mem_top + size;
 	size_t old_bytes = trans->mem_bytes;
 	size_t new_bytes = roundup_pow_of_two(new_top);
+	int ret;
 	void *new_mem;
 	void *p;
 
@@ -2710,15 +2696,27 @@ void *__bch2_trans_kmalloc(struct btree_trans *trans, size_t size)
 
 	WARN_ON_ONCE(new_bytes > BTREE_TRANS_MEM_MAX);
 
-	new_mem = krealloc(trans->mem, new_bytes, GFP_NOFS);
-	if (!new_mem && new_bytes <= BTREE_TRANS_MEM_MAX) {
-		new_mem = mempool_alloc(&trans->c->btree_trans_mem_pool, GFP_KERNEL);
-		new_bytes = BTREE_TRANS_MEM_MAX;
-		kfree(trans->mem);
-	}
+	new_mem = krealloc(trans->mem, new_bytes, GFP_NOWAIT|__GFP_NOWARN);
+	if (unlikely(!new_mem)) {
+		bch2_trans_unlock(trans);
+
+		new_mem = krealloc(trans->mem, new_bytes, GFP_KERNEL);
+		if (!new_mem && new_bytes <= BTREE_TRANS_MEM_MAX) {
+			new_mem = mempool_alloc(&trans->c->btree_trans_mem_pool, GFP_KERNEL);
+			new_bytes = BTREE_TRANS_MEM_MAX;
+			kfree(trans->mem);
+		}
 
-	if (!new_mem)
-		return ERR_PTR(-ENOMEM);
+		if (!new_mem)
+			return ERR_PTR(-BCH_ERR_ENOMEM_trans_kmalloc);
+
+		trans->mem = new_mem;
+		trans->mem_bytes = new_bytes;
+
+		ret = bch2_trans_relock(trans);
+		if (ret)
+			return ERR_PTR(ret);
+	}
 
 	trans->mem = new_mem;
 	trans->mem_bytes = new_bytes;
@@ -2734,10 +2732,44 @@ void *__bch2_trans_kmalloc(struct btree_trans *trans, size_t size)
 	return p;
 }
 
+static inline void check_srcu_held_too_long(struct btree_trans *trans)
+{
+	WARN(trans->srcu_held && time_after(jiffies, trans->srcu_lock_time + HZ * 10),
+	     "btree trans held srcu lock (delaying memory reclaim) for %lu seconds",
+	     (jiffies - trans->srcu_lock_time) / HZ);
+}
+
+void bch2_trans_srcu_unlock(struct btree_trans *trans)
+{
+	if (trans->srcu_held) {
+		struct bch_fs *c = trans->c;
+		struct btree_path *path;
+
+		trans_for_each_path(trans, path)
+			if (path->cached && !btree_node_locked(path, 0))
+				path->l[0].b = ERR_PTR(-BCH_ERR_no_btree_node_srcu_reset);
+
+		check_srcu_held_too_long(trans);
+		srcu_read_unlock(&c->btree_trans_barrier, trans->srcu_idx);
+		trans->srcu_held = false;
+	}
+}
+
+void bch2_trans_srcu_lock(struct btree_trans *trans)
+{
+	if (!trans->srcu_held) {
+		trans->srcu_idx = srcu_read_lock(&trans->c->btree_trans_barrier);
+		trans->srcu_lock_time	= jiffies;
+		trans->srcu_held = true;
+	}
+}
+
 /**
  * bch2_trans_begin() - reset a transaction after a interrupted attempt
  * @trans: transaction to reset
  *
+ * Returns:	current restart counter, to be used with trans_was_restarted()
+ *
  * While iterating over nodes or updating nodes a attempt to lock a btree node
  * may return BCH_ERR_transaction_restart when the trylock fails. When this
  * occurs bch2_trans_begin() should be called and the transaction retried.
@@ -2745,20 +2777,13 @@ void *__bch2_trans_kmalloc(struct btree_trans *trans, size_t size)
 u32 bch2_trans_begin(struct btree_trans *trans)
 {
 	struct btree_path *path;
+	u64 now;
 
 	bch2_trans_reset_updates(trans);
 
 	trans->restart_count++;
 	trans->mem_top			= 0;
 
-	if (trans->fs_usage_deltas) {
-		trans->fs_usage_deltas->used = 0;
-		memset((void *) trans->fs_usage_deltas +
-		       offsetof(struct replicas_delta_list, memset_start), 0,
-		       (void *) &trans->fs_usage_deltas->memset_end -
-		       (void *) &trans->fs_usage_deltas->memset_start);
-	}
-
 	trans_for_each_path(trans, path) {
 		path->should_be_locked = false;
 
@@ -2781,57 +2806,57 @@ u32 bch2_trans_begin(struct btree_trans *trans)
 			path->preserve = false;
 	}
 
+	now = local_clock();
 	if (!trans->restarted &&
 	    (need_resched() ||
-	     ktime_get_ns() - trans->last_begin_time > BTREE_TRANS_MAX_LOCK_HOLD_TIME_NS)) {
-		bch2_trans_unlock(trans);
-		cond_resched();
-		bch2_trans_relock(trans);
+	     now - trans->last_begin_time > BTREE_TRANS_MAX_LOCK_HOLD_TIME_NS)) {
+		drop_locks_do(trans, (cond_resched(), 0));
+		now = local_clock();
 	}
+	trans->last_begin_time = now;
+
+	if (unlikely(trans->srcu_held &&
+		     time_after(jiffies, trans->srcu_lock_time + msecs_to_jiffies(10))))
+		bch2_trans_srcu_unlock(trans);
 
-	trans->last_restarted_ip = _RET_IP_;
-	if (trans->restarted)
+	trans->last_begin_ip = _RET_IP_;
+	if (trans->restarted) {
 		bch2_btree_path_traverse_all(trans);
+		trans->notrace_relock_fail = false;
+	}
 
-	trans->last_begin_time = ktime_get_ns();
 	return trans->restart_count;
 }
 
-void bch2_trans_verify_not_restarted(struct btree_trans *trans, u32 restart_count)
-{
-	if (trans_was_restarted(trans, restart_count))
-		panic("trans->restart_count %u, should be %u, last restarted by %pS\n",
-		      trans->restart_count, restart_count,
-		      (void *) trans->last_restarted_ip);
-}
-
-static void bch2_trans_alloc_paths(struct btree_trans *trans, struct bch_fs *c)
+static struct btree_trans *bch2_trans_alloc(struct bch_fs *c)
 {
-	size_t paths_bytes	= sizeof(struct btree_path) * BTREE_ITER_MAX;
-	size_t updates_bytes	= sizeof(struct btree_insert_entry) * BTREE_ITER_MAX;
-	void *p = NULL;
+	struct btree_trans *trans;
 
-	BUG_ON(trans->used_mempool);
-
-#ifdef __KERNEL__
-	p = this_cpu_xchg(c->btree_paths_bufs->path , NULL);
-#endif
-	if (!p)
-		p = mempool_alloc(&trans->c->btree_paths_pool, GFP_NOFS);
+	if (IS_ENABLED(__KERNEL__)) {
+		trans = this_cpu_xchg(c->btree_trans_bufs->trans, NULL);
+		if (trans)
+			return trans;
+	}
 
-	trans->paths		= p; p += paths_bytes;
-	trans->updates		= p; p += updates_bytes;
+	trans = mempool_alloc(&c->btree_trans_pool, GFP_NOFS);
+	/*
+	 * paths need to be zeroed, bch2_check_for_deadlock looks at
+	 * paths in other threads
+	 */
+	memset(&trans->paths, 0, sizeof(trans->paths));
+	return trans;
 }
 
-static inline unsigned bch2_trans_get_fn_idx(struct btree_trans *trans, struct bch_fs *c,
-					const char *fn)
+const char *bch2_btree_transaction_fns[BCH_TRANSACTIONS_NR];
+
+unsigned bch2_trans_get_fn_idx(const char *fn)
 {
 	unsigned i;
 
-	for (i = 0; i < ARRAY_SIZE(c->btree_transaction_fns); i++)
-		if (!c->btree_transaction_fns[i] ||
-		    c->btree_transaction_fns[i] == fn) {
-			c->btree_transaction_fns[i] = fn;
+	for (i = 0; i < ARRAY_SIZE(bch2_btree_transaction_fns); i++)
+		if (!bch2_btree_transaction_fns[i] ||
+		    bch2_btree_transaction_fns[i] == fn) {
+			bch2_btree_transaction_fns[i] = fn;
 			return i;
 		}
 
@@ -2839,26 +2864,30 @@ static inline unsigned bch2_trans_get_fn_idx(struct btree_trans *trans, struct b
 	return i;
 }
 
-void __bch2_trans_init(struct btree_trans *trans, struct bch_fs *c, const char *fn)
+struct btree_trans *__bch2_trans_get(struct bch_fs *c, unsigned fn_idx)
 	__acquires(&c->btree_trans_barrier)
 {
+	struct btree_trans *trans;
 	struct btree_transaction_stats *s;
-	struct btree_trans *pos;
 
-	BUG_ON(lock_class_is_held(&bch2_btree_node_lock_key));
+	bch2_assert_btree_nodes_not_locked();
+
+	trans = bch2_trans_alloc(c);
 
 	memset(trans, 0, sizeof(*trans));
 	trans->c		= c;
-	trans->fn		= fn;
-	trans->last_begin_time	= ktime_get_ns();
-	trans->fn_idx		= bch2_trans_get_fn_idx(trans, c, fn);
+	trans->fn		= fn_idx < ARRAY_SIZE(bch2_btree_transaction_fns)
+		? bch2_btree_transaction_fns[fn_idx] : NULL;
+	trans->last_begin_time	= local_clock();
+	trans->fn_idx		= fn_idx;
 	trans->locking_wait.task = current;
+	trans->journal_replay_not_finished =
+		unlikely(!test_bit(JOURNAL_REPLAY_DONE, &c->journal.flags)) &&
+		atomic_inc_not_zero(&c->journal_keys.ref);
 	closure_init_stack(&trans->ref);
 
-	bch2_trans_alloc_paths(trans, c);
-
 	s = btree_trans_stats(trans);
-	if (s) {
+	if (s && s->max_mem) {
 		unsigned expected_mem_bytes = roundup_pow_of_two(s->max_mem);
 
 		trans->mem = kmalloc(expected_mem_bytes, GFP_KERNEL);
@@ -2869,22 +2898,42 @@ void __bch2_trans_init(struct btree_trans *trans, struct bch_fs *c, const char *
 		} else {
 			trans->mem_bytes = expected_mem_bytes;
 		}
+	}
 
+	if (s) {
 		trans->nr_max_paths = s->nr_max_paths;
+		trans->wb_updates_size = s->wb_updates_size;
 	}
 
-	trans->srcu_idx = srcu_read_lock(&c->btree_trans_barrier);
+	trans->srcu_idx		= srcu_read_lock(&c->btree_trans_barrier);
+	trans->srcu_lock_time	= jiffies;
+	trans->srcu_held	= true;
+
+	if (IS_ENABLED(CONFIG_BCACHEFS_DEBUG_TRANSACTIONS)) {
+		struct btree_trans *pos;
 
-	mutex_lock(&c->btree_trans_lock);
-	list_for_each_entry(pos, &c->btree_trans_list, list) {
-		if (trans->locking_wait.task->pid < pos->locking_wait.task->pid) {
-			list_add_tail(&trans->list, &pos->list);
-			goto list_add_done;
+		seqmutex_lock(&c->btree_trans_lock);
+		list_for_each_entry(pos, &c->btree_trans_list, list) {
+			/*
+			 * We'd much prefer to be stricter here and completely
+			 * disallow multiple btree_trans in the same thread -
+			 * but the data move path calls bch2_write when we
+			 * already have a btree_trans initialized.
+			 */
+			BUG_ON(trans->locking_wait.task->pid == pos->locking_wait.task->pid &&
+			       bch2_trans_locked(pos));
+
+			if (trans->locking_wait.task->pid < pos->locking_wait.task->pid) {
+				list_add_tail(&trans->list, &pos->list);
+				goto list_add_done;
+			}
 		}
-	}
-	list_add_tail(&trans->list, &c->btree_trans_list);
+		list_add_tail(&trans->list, &c->btree_trans_list);
 list_add_done:
-	mutex_unlock(&c->btree_trans_lock);
+		seqmutex_unlock(&c->btree_trans_lock);
+	}
+
+	return trans;
 }
 
 static void check_btree_paths_leaked(struct btree_trans *trans)
@@ -2902,14 +2951,14 @@ leaked:
 	trans_for_each_path(trans, path)
 		if (path->ref)
 			printk(KERN_ERR "  btree %s %pS\n",
-			       bch2_btree_ids[path->btree_id],
+			       bch2_btree_id_str(path->btree_id),
 			       (void *) path->ip_allocated);
 	/* Be noisy about this: */
 	bch2_fatal_error(c);
 #endif
 }
 
-void bch2_trans_exit(struct btree_trans *trans)
+void bch2_trans_put(struct btree_trans *trans)
 	__releases(&c->btree_trans_barrier)
 {
 	struct btree_insert_entry *i;
@@ -2918,6 +2967,12 @@ void bch2_trans_exit(struct btree_trans *trans)
 
 	bch2_trans_unlock(trans);
 
+	if (IS_ENABLED(CONFIG_BCACHEFS_DEBUG_TRANSACTIONS)) {
+		seqmutex_lock(&c->btree_trans_lock);
+		list_del(&trans->list);
+		seqmutex_unlock(&c->btree_trans_lock);
+	}
+
 	closure_sync(&trans->ref);
 
 	if (s)
@@ -2929,13 +2984,10 @@ void bch2_trans_exit(struct btree_trans *trans)
 
 	check_btree_paths_leaked(trans);
 
-	mutex_lock(&c->btree_trans_lock);
-	list_del(&trans->list);
-	mutex_unlock(&c->btree_trans_lock);
-
-	srcu_read_unlock(&c->btree_trans_barrier, trans->srcu_idx);
-
-	bch2_journal_preres_put(&c->journal, &trans->journal_preres);
+	if (trans->srcu_held) {
+		check_srcu_held_too_long(trans);
+		srcu_read_unlock(&c->btree_trans_barrier, trans->srcu_idx);
+	}
 
 	kfree(trans->extra_journal_entries.data);
 
@@ -2948,23 +3000,19 @@ void bch2_trans_exit(struct btree_trans *trans)
 			kfree(trans->fs_usage_deltas);
 	}
 
+	if (unlikely(trans->journal_replay_not_finished))
+		bch2_journal_keys_put(c);
+
 	if (trans->mem_bytes == BTREE_TRANS_MEM_MAX)
 		mempool_free(trans->mem, &c->btree_trans_mem_pool);
 	else
 		kfree(trans->mem);
 
-#ifdef __KERNEL__
-	/*
-	 * Userspace doesn't have a real percpu implementation:
-	 */
-	trans->paths = this_cpu_xchg(c->btree_paths_bufs->path, trans->paths);
-#endif
-
-	if (trans->paths)
-		mempool_free(trans->paths, &c->btree_paths_pool);
-
-	trans->mem	= (void *) 0x1;
-	trans->paths	= (void *) 0x1;
+	/* Userspace doesn't have a real percpu implementation: */
+	if (IS_ENABLED(__KERNEL__))
+		trans = this_cpu_xchg(c->btree_trans_bufs->trans, trans);
+	if (trans)
+		mempool_free(trans, &c->btree_trans_pool);
 }
 
 static void __maybe_unused
@@ -2977,12 +3025,12 @@ bch2_btree_bkey_cached_common_to_text(struct printbuf *out,
 
 	rcu_read_lock();
 	owner = READ_ONCE(b->lock.owner);
-	pid = owner ? owner->pid : 0;;
+	pid = owner ? owner->pid : 0;
 	rcu_read_unlock();
 
 	prt_tab(out);
 	prt_printf(out, "%px %c l=%u %s:", b, b->cached ? 'c' : 'b',
-		   b->level, bch2_btree_ids[b->btree_id]);
+		   b->level, bch2_btree_id_str(b->btree_id));
 	bch2_bpos_to_text(out, btree_node_pos(b));
 
 	prt_tab(out);
@@ -2995,16 +3043,17 @@ void bch2_btree_trans_to_text(struct printbuf *out, struct btree_trans *trans)
 	struct btree_path *path;
 	struct btree_bkey_cached_common *b;
 	static char lock_types[] = { 'r', 'i', 'w' };
-	unsigned l;
+	struct task_struct *task = READ_ONCE(trans->locking_wait.task);
+	unsigned l, idx;
 
 	if (!out->nr_tabstops) {
 		printbuf_tabstop_push(out, 16);
 		printbuf_tabstop_push(out, 32);
 	}
 
-	prt_printf(out, "%i %s\n", trans->locking_wait.task->pid, trans->fn);
+	prt_printf(out, "%i %s\n", task ? task->pid : 0, trans->fn);
 
-	trans_for_each_path(trans, path) {
+	trans_for_each_path_safe(trans, path, idx) {
 		if (!path->nodes_locked)
 			continue;
 
@@ -3012,7 +3061,7 @@ void bch2_btree_trans_to_text(struct printbuf *out, struct btree_trans *trans)
 		       path->idx,
 		       path->cached ? 'c' : 'b',
 		       path->level,
-		       bch2_btree_ids[path->btree_id]);
+		       bch2_btree_id_str(path->btree_id));
 		bch2_bpos_to_text(out, path->pos);
 		prt_newline(out);
 
@@ -3029,7 +3078,9 @@ void bch2_btree_trans_to_text(struct printbuf *out, struct btree_trans *trans)
 
 	b = READ_ONCE(trans->locking);
 	if (b) {
-		prt_str(out, "  want");
+		prt_printf(out, "  blocked for %lluus on",
+			   div_u64(local_clock() - trans->locking_wait.start_time,
+				   1000));
 		prt_newline(out);
 		prt_printf(out, "    %c", lock_types[trans->locking_wait.lock_want]);
 		bch2_btree_bkey_cached_common_to_text(out, b);
@@ -3039,26 +3090,53 @@ void bch2_btree_trans_to_text(struct printbuf *out, struct btree_trans *trans)
 
 void bch2_fs_btree_iter_exit(struct bch_fs *c)
 {
+	struct btree_transaction_stats *s;
+	struct btree_trans *trans;
+	int cpu;
+
+	trans = list_first_entry_or_null(&c->btree_trans_list, struct btree_trans, list);
+	if (trans)
+		panic("%s leaked btree_trans\n", trans->fn);
+
+	if (c->btree_trans_bufs)
+		for_each_possible_cpu(cpu)
+			kfree(per_cpu_ptr(c->btree_trans_bufs, cpu)->trans);
+	free_percpu(c->btree_trans_bufs);
+
+	for (s = c->btree_transaction_stats;
+	     s < c->btree_transaction_stats + ARRAY_SIZE(c->btree_transaction_stats);
+	     s++) {
+		kfree(s->max_paths_text);
+		bch2_time_stats_exit(&s->lock_hold_times);
+	}
+
 	if (c->btree_trans_barrier_initialized)
 		cleanup_srcu_struct(&c->btree_trans_barrier);
 	mempool_exit(&c->btree_trans_mem_pool);
-	mempool_exit(&c->btree_paths_pool);
+	mempool_exit(&c->btree_trans_pool);
 }
 
 int bch2_fs_btree_iter_init(struct bch_fs *c)
 {
-	unsigned i, nr = BTREE_ITER_MAX;
+	struct btree_transaction_stats *s;
 	int ret;
 
-	for (i = 0; i < ARRAY_SIZE(c->btree_transaction_stats); i++)
-		mutex_init(&c->btree_transaction_stats[i].lock);
+	for (s = c->btree_transaction_stats;
+	     s < c->btree_transaction_stats + ARRAY_SIZE(c->btree_transaction_stats);
+	     s++) {
+		bch2_time_stats_init(&s->lock_hold_times);
+		mutex_init(&s->lock);
+	}
 
 	INIT_LIST_HEAD(&c->btree_trans_list);
-	mutex_init(&c->btree_trans_lock);
+	seqmutex_init(&c->btree_trans_lock);
+
+	c->btree_trans_bufs = alloc_percpu(struct btree_trans_buf);
+	if (!c->btree_trans_bufs)
+		return -ENOMEM;
 
-	ret   = mempool_init_kmalloc_pool(&c->btree_paths_pool, 1,
-			sizeof(struct btree_path) * nr +
-			sizeof(struct btree_insert_entry) * nr) ?:
+	ret   = mempool_init_kmalloc_pool(&c->btree_trans_pool, 1,
+					  sizeof(struct btree_trans)) ?:
 		mempool_init_kmalloc_pool(&c->btree_trans_mem_pool, 1,
 					  BTREE_TRANS_MEM_MAX) ?:
 		init_srcu_struct(&c->btree_trans_barrier);