X-Git-Url: https://git.sesse.net/?a=blobdiff_plain;f=libbcachefs%2Fbtree_iter.c;h=929f33dff5d7bb6ce99a1f3e91172ec320813de2;hb=8d8a9f3e9bdd1d84fbbe0531e81977cc9044654a;hp=3977bb1fd8345bb8b9c0b970e56f15e3f9fcb853;hpb=1b2d60826974e31b9894b6d5aa59b0e7e62823cd;p=bcachefs-tools-debian

diff --git a/libbcachefs/btree_iter.c b/libbcachefs/btree_iter.c
index 3977bb1..929f33d 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"
@@ -12,13 +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 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 *,
@@ -35,21 +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,
@@ -241,7 +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;
 		}
 
@@ -272,7 +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);
@@ -377,7 +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" : "");
 }
 
@@ -503,7 +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);
@@ -652,9 +636,8 @@ void bch2_btree_path_level_init(struct btree_trans *trans,
 	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);
 }
@@ -704,7 +687,7 @@ 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);
 			}
 
@@ -736,7 +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;
@@ -780,7 +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;
 		}
@@ -797,7 +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);
@@ -815,7 +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);
 	}
 
@@ -832,7 +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);
@@ -850,7 +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);
 	}
 
@@ -952,7 +936,8 @@ static __always_inline int btree_path_down(struct btree_trans *trans,
 	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);
 
@@ -976,6 +961,7 @@ static int bch2_btree_path_traverse_all(struct btree_trans *trans)
 	trans->in_traverse_all = true;
 retry_all:
 	trans->restarted = 0;
+	trans->last_restarted_ip = 0;
 
 	trans_for_each_path(trans, path)
 		path->should_be_locked = false;
@@ -991,7 +977,7 @@ retry_all:
 		closure_init_stack(&cl);
 
 		do {
-			ret = bch2_btree_cache_cannibalize_lock(c, &cl);
+			ret = bch2_btree_cache_cannibalize_lock(trans, &cl);
 			closure_sync(&cl);
 		} while (ret);
 	}
@@ -1011,7 +997,7 @@ retry_all:
 			__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;
@@ -1023,11 +1009,11 @@ retry_all:
 	/*
 	 * 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 we might have unlocked and
+	 * path->should_be_locked is not set yet, we might have unlocked and
 	 * then failed to relock a path - that's fine.
 	 */
 err:
-	bch2_btree_cache_cannibalize_unlock(c);
+	bch2_btree_cache_cannibalize_unlock(trans);
 
 	trans->in_traverse_all = false;
 
@@ -1123,6 +1109,9 @@ int bch2_btree_path_traverse_one(struct btree_trans *trans,
 	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:
@@ -1174,17 +1163,10 @@ int bch2_btree_path_traverse_one(struct btree_trans *trans,
 
 	path->uptodate = BTREE_ITER_UPTODATE;
 out:
-	if (bch2_err_matches(ret, BCH_ERR_transaction_restart) != !!trans->restarted) {
-		struct printbuf buf = PRINTBUF;
-
-		prt_printf(&buf, "ret %s (%i) trans->restarted %s (%i)\n",
-			   bch2_err_str(ret), ret,
-			   bch2_err_str(trans->restarted), trans->restarted);
-#ifdef CONFIG_BCACHEFS_DEBUG
-		bch2_prt_backtrace(&buf, &trans->last_restarted);
-#endif
-		panic("%s", buf.buf);
-	}
+	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;
 }
@@ -1232,8 +1214,6 @@ __bch2_btree_path_set_pos(struct btree_trans *trans,
 		   struct btree_path *path, struct bpos new_pos,
 		   bool intent, unsigned long ip, int cmp)
 {
-	unsigned level = path->level;
-
 	bch2_trans_verify_not_in_restart(trans);
 	EBUG_ON(!path->ref);
 
@@ -1249,7 +1229,7 @@ __bch2_btree_path_set_pos(struct btree_trans *trans,
 		goto out;
 	}
 
-	level = 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, level)) {
 		struct btree_path_level *l = &path->l[level];
@@ -1318,7 +1298,7 @@ static inline void __bch2_path_free(struct btree_trans *trans, struct btree_path
 {
 	__bch2_btree_path_unlock(trans, path);
 	btree_path_list_remove(trans, path);
-	trans->paths_allocated &= ~(1ULL << path->idx);
+	__clear_bit(path->idx, trans->paths_allocated);
 }
 
 void bch2_path_put(struct btree_trans *trans, struct btree_path *path, bool intent)
@@ -1363,18 +1343,18 @@ static void bch2_path_put_nokeep(struct btree_trans *trans, struct btree_path *p
 	__bch2_path_free(trans, path);
 }
 
-void bch2_trans_restart_error(struct btree_trans *trans, u32 restart_count)
+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 bch2_trans_in_restart_error(struct btree_trans *trans)
+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_begin_ip);
+	      (void *) trans->last_restarted_ip);
 }
 
 noinline __cold
@@ -1392,7 +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);
@@ -1408,7 +1388,7 @@ void bch2_trans_updates_to_text(struct printbuf *buf, struct btree_trans *trans)
 
 	trans_for_each_wb_update(trans, wb) {
 		prt_printf(buf, "update: btree=%s wb=1 %pS",
-		       bch2_btree_ids[wb->btree],
+		       bch2_btree_id_str(wb->btree),
 		       (void *) i->ip_allocated);
 		prt_newline(buf);
 
@@ -1437,7 +1417,7 @@ void bch2_btree_path_to_text(struct printbuf *out, struct btree_path *path)
 		   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);
 
@@ -1448,7 +1428,7 @@ void bch2_btree_path_to_text(struct printbuf *out, struct btree_path *path)
 	prt_newline(out);
 }
 
-noinline __cold
+static noinline __cold
 void __bch2_trans_paths_to_text(struct printbuf *out, struct btree_trans *trans,
 				bool nosort)
 {
@@ -1468,7 +1448,7 @@ void bch2_trans_paths_to_text(struct printbuf *out, struct btree_trans *trans)
 	__bch2_trans_paths_to_text(out, trans, false);
 }
 
-noinline __cold
+static noinline __cold
 void __bch2_dump_trans_paths_updates(struct btree_trans *trans, bool nosort)
 {
 	struct printbuf buf = PRINTBUF;
@@ -1491,6 +1471,7 @@ static void bch2_trans_update_max_paths(struct btree_trans *trans)
 {
 	struct btree_transaction_stats *s = btree_trans_stats(trans);
 	struct printbuf buf = PRINTBUF;
+	size_t nr = bitmap_weight(trans->paths_allocated, BTREE_ITER_MAX);
 
 	if (!s)
 		return;
@@ -1499,9 +1480,8 @@ static void bch2_trans_update_max_paths(struct btree_trans *trans)
 
 	if (!buf.allocation_failure) {
 		mutex_lock(&s->lock);
-		if (s->nr_max_paths < hweight64(trans->paths_allocated)) {
-			s->nr_max_paths = trans->nr_max_paths =
-				hweight64(trans->paths_allocated);
+		if (nr > s->nr_max_paths) {
+			s->nr_max_paths = nr;
 			swap(s->max_paths_text, buf.buf);
 		}
 		mutex_unlock(&s->lock);
@@ -1509,26 +1489,41 @@ static void bch2_trans_update_max_paths(struct btree_trans *trans)
 
 	printbuf_exit(&buf);
 
-	trans->nr_max_paths = hweight64(trans->paths_allocated);
+	trans->nr_max_paths = nr;
+}
+
+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,
 						  struct btree_path *pos)
 {
 	struct btree_path *path;
-	unsigned idx;
+	size_t idx = find_first_zero_bit(trans->paths_allocated, BTREE_ITER_MAX);
 
-	if (unlikely(trans->paths_allocated ==
-		     ~((~0ULL << 1) << (BTREE_ITER_MAX - 1))))
+	if (unlikely(idx == BTREE_ITER_MAX))
 		btree_path_overflow(trans);
 
-	idx = __ffs64(~trans->paths_allocated);
+	BUG_ON(idx > BTREE_ITER_MAX);
 
 	/*
 	 * Do this before marking the new path as allocated, since it won't be
@@ -1537,13 +1532,14 @@ static inline struct btree_path *btree_path_alloc(struct btree_trans *trans,
 	if (unlikely(idx > trans->nr_max_paths))
 		bch2_trans_update_max_paths(trans);
 
-	trans->paths_allocated |= 1ULL << idx;
+	__set_bit(idx, trans->paths_allocated);
 
 	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;
@@ -1619,7 +1615,7 @@ 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;
 }
@@ -1729,6 +1725,17 @@ 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;
@@ -1805,23 +1812,15 @@ 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_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;
+	struct bpos pos = iter->k.p;
+	bool ret = !(iter->flags & BTREE_ITER_ALL_SNAPSHOTS
+		     ? bpos_eq(pos, SPOS_MAX)
+		     : bkey_eq(pos, SPOS_MAX));
 
-		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)
@@ -1866,23 +1865,15 @@ static inline struct bkey_i *btree_trans_peek_updates(struct btree_iter *iter)
 		: NULL;
 }
 
-struct bkey_i *bch2_btree_journal_peek(struct btree_trans *trans,
-				       struct btree_iter *iter,
-				       struct bpos end_pos)
+static struct bkey_i *bch2_btree_journal_peek(struct btree_trans *trans,
+					      struct btree_iter *iter,
+					      struct bpos end_pos)
 {
-	struct bkey_i *k;
-
-	if (bpos_lt(iter->path->pos, iter->journal_pos))
-		iter->journal_idx = 0;
-
-	k = bch2_journal_keys_peek_upto(trans->c, iter->btree_id,
-					iter->path->level,
-					iter->path->pos,
-					end_pos,
-					&iter->journal_idx);
-
-	iter->journal_pos = k ? k->k.p : end_pos;
-	return k;
+	return bch2_journal_keys_peek_upto(trans->c, iter->btree_id,
+					   iter->path->level,
+					   iter->path->pos,
+					   end_pos,
+					   &iter->journal_idx);
 }
 
 static noinline
@@ -2057,8 +2048,12 @@ 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)
 {
@@ -2068,7 +2063,6 @@ 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) {
@@ -2195,102 +2189,11 @@ end:
 }
 
 /**
- * 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_eq(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_eq(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_eq(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_eq(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)
 {
@@ -2301,8 +2204,11 @@ 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)
 {
@@ -2425,8 +2331,11 @@ 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)
 {
@@ -2445,7 +2354,6 @@ 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: */
@@ -2574,6 +2482,18 @@ struct bkey_s_c bch2_btree_iter_prev_slot(struct btree_iter *iter)
 	return bch2_btree_iter_peek_slot(iter);
 }
 
+struct bkey_s_c bch2_btree_iter_peek_and_restart_outlined(struct btree_iter *iter)
+{
+	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;
+}
+
 /* new transactional stuff: */
 
 #ifdef CONFIG_BCACHEFS_DEBUG
@@ -2582,7 +2502,7 @@ static void btree_trans_verify_sorted_refs(struct btree_trans *trans)
 	struct btree_path *path;
 	unsigned i;
 
-	BUG_ON(trans->nr_sorted != hweight64(trans->paths_allocated));
+	BUG_ON(trans->nr_sorted != bitmap_weight(trans->paths_allocated, BTREE_ITER_MAX));
 
 	trans_for_each_path(trans, path) {
 		BUG_ON(path->sorted_idx >= trans->nr_sorted);
@@ -2592,7 +2512,7 @@ static void btree_trans_verify_sorted_refs(struct btree_trans *trans)
 	for (i = 0; i < trans->nr_sorted; i++) {
 		unsigned idx = trans->sorted[i];
 
-		EBUG_ON(!(trans->paths_allocated & (1ULL << idx)));
+		BUG_ON(!test_bit(idx, trans->paths_allocated));
 		BUG_ON(trans->paths[idx].sorted_idx != i);
 	}
 }
@@ -2705,12 +2625,12 @@ 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);
@@ -2719,19 +2639,9 @@ 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_inlined(struct btree_trans *trans,
-			  struct btree_iter *iter,
-			  unsigned btree_id, struct bpos pos,
-			  unsigned flags)
-{
-	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_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)
 {
 	bch2_trans_iter_init_common(trans, iter, btree_id, pos, 0, 0,
@@ -2747,9 +2657,9 @@ void bch2_trans_node_iter_init(struct btree_trans *trans,
 			       unsigned depth,
 			       unsigned flags)
 {
-       flags |= BTREE_ITER_NOT_EXTENTS;
-       flags |= __BTREE_ITER_ALL_SNAPSHOTS;
-       flags |= BTREE_ITER_ALL_SNAPSHOTS;
+	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),
@@ -2777,6 +2687,7 @@ 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;
 
@@ -2784,15 +2695,27 @@ 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;
@@ -2808,24 +2731,44 @@ void *__bch2_trans_kmalloc(struct btree_trans *trans, size_t size)
 	return p;
 }
 
-static noinline void bch2_trans_reset_srcu_lock(struct btree_trans *trans)
+static inline void check_srcu_held_too_long(struct btree_trans *trans)
 {
-	struct bch_fs *c = trans->c;
-	struct btree_path *path;
+	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);
+}
 
-	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);
+void bch2_trans_srcu_unlock(struct btree_trans *trans)
+{
+	if (trans->srcu_held) {
+		struct bch_fs *c = trans->c;
+		struct btree_path *path;
 
-	srcu_read_unlock(&c->btree_trans_barrier, trans->srcu_idx);
-	trans->srcu_idx = srcu_read_lock(&c->btree_trans_barrier);
-	trans->srcu_lock_time	= jiffies;
+		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.
@@ -2833,6 +2776,7 @@ static noinline void bch2_trans_reset_srcu_lock(struct btree_trans *trans)
 u32 bch2_trans_begin(struct btree_trans *trans)
 {
 	struct btree_path *path;
+	u64 now;
 
 	bch2_trans_reset_updates(trans);
 
@@ -2861,16 +2805,18 @@ u32 bch2_trans_begin(struct btree_trans *trans)
 			path->preserve = false;
 	}
 
+	now = local_clock();
 	if (!trans->restarted &&
 	    (need_resched() ||
-	     local_clock() - 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(time_after(jiffies, trans->srcu_lock_time + msecs_to_jiffies(10))))
-		bch2_trans_reset_srcu_lock(trans);
+	if (unlikely(trans->srcu_held &&
+		     time_after(jiffies, trans->srcu_lock_time + msecs_to_jiffies(10))))
+		bch2_trans_srcu_unlock(trans);
 
 	trans->last_begin_ip = _RET_IP_;
 	if (trans->restarted) {
@@ -2878,26 +2824,26 @@ u32 bch2_trans_begin(struct btree_trans *trans)
 		trans->notrace_relock_fail = false;
 	}
 
-	trans->last_begin_time = local_clock();
 	return trans->restart_count;
 }
 
-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;
-
-	BUG_ON(trans->used_mempool);
+	struct btree_trans *trans;
 
-#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;
 }
 
 const char *bch2_btree_transaction_fns[BCH_TRANSACTIONS_NR];
@@ -2917,12 +2863,13 @@ unsigned bch2_trans_get_fn_idx(const char *fn)
 	return i;
 }
 
-void __bch2_trans_init(struct btree_trans *trans, struct bch_fs *c, unsigned fn_idx)
+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;
 
-	BUG_ON(lock_class_is_held(&bch2_btree_node_lock_key));
+	trans = bch2_trans_alloc(c);
 
 	memset(trans, 0, sizeof(*trans));
 	trans->c		= c;
@@ -2932,11 +2879,10 @@ void __bch2_trans_init(struct btree_trans *trans, struct bch_fs *c, unsigned fn_
 	trans->fn_idx		= fn_idx;
 	trans->locking_wait.task = current;
 	trans->journal_replay_not_finished =
-		!test_bit(JOURNAL_REPLAY_DONE, &c->journal.flags);
+		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 && s->max_mem) {
 		unsigned expected_mem_bytes = roundup_pow_of_two(s->max_mem);
@@ -2956,14 +2902,24 @@ void __bch2_trans_init(struct btree_trans *trans, struct bch_fs *c, unsigned fn_
 		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);
+		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;
@@ -2971,8 +2927,10 @@ void __bch2_trans_init(struct btree_trans *trans, struct bch_fs *c, unsigned fn_
 		}
 		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)
@@ -2990,14 +2948,14 @@ 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;
@@ -3006,6 +2964,12 @@ 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)
@@ -3017,16 +2981,11 @@ void bch2_trans_exit(struct btree_trans *trans)
 
 	check_btree_paths_leaked(trans);
 
-	if (IS_ENABLED(CONFIG_BCACHEFS_DEBUG_TRANSACTIONS)) {
-		mutex_lock(&c->btree_trans_lock);
-		list_del(&trans->list);
-		mutex_unlock(&c->btree_trans_lock);
+	if (trans->srcu_held) {
+		check_srcu_held_too_long(trans);
+		srcu_read_unlock(&c->btree_trans_barrier, trans->srcu_idx);
 	}
 
-	srcu_read_unlock(&c->btree_trans_barrier, trans->srcu_idx);
-
-	bch2_journal_preres_put(&c->journal, &trans->journal_preres);
-
 	kfree(trans->extra_journal_entries.data);
 
 	if (trans->fs_usage_deltas) {
@@ -3038,27 +2997,19 @@ 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);
-
-#ifdef CONFIG_BCACHEFS_DEBUG
-	darray_exit(&trans->last_restarted);
-#endif
-
-	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
@@ -3076,7 +3027,7 @@ bch2_btree_bkey_cached_common_to_text(struct printbuf *out,
 
 	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);
@@ -3089,16 +3040,17 @@ 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;
 
@@ -3106,7 +3058,7 @@ 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);
 
@@ -3136,6 +3088,17 @@ 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);
@@ -3147,13 +3110,12 @@ void bch2_fs_btree_iter_exit(struct bch_fs *c)
 	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)
 {
 	struct btree_transaction_stats *s;
-	unsigned nr = BTREE_ITER_MAX;
 	int ret;
 
 	for (s = c->btree_transaction_stats;
@@ -3164,11 +3126,14 @@ int bch2_fs_btree_iter_init(struct bch_fs *c)
 	}
 
 	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);