X-Git-Url: https://git.sesse.net/?a=blobdiff_plain;f=libbcachefs%2Fbtree_iter.h;h=24772538e4cc74ada59851bd7847dd5ece5ea122;hb=HEAD;hp=ab35fcd8b8b4d10e132486bf709c0766d1be4a66;hpb=1952c0790c74e4e81d7066a19aabc5c55a13f10f;p=bcachefs-tools-debian

diff --git a/libbcachefs/btree_iter.h b/libbcachefs/btree_iter.h
index ab35fcd..2477253 100644
--- a/libbcachefs/btree_iter.h
+++ b/libbcachefs/btree_iter.h
@@ -4,301 +4,881 @@
 
 #include "bset.h"
 #include "btree_types.h"
+#include "trace.h"
 
-static inline void btree_iter_set_dirty(struct btree_iter *iter,
-					enum btree_iter_uptodate u)
+static inline int __bkey_err(const struct bkey *k)
 {
-	iter->uptodate = max_t(unsigned, iter->uptodate, u);
+	return PTR_ERR_OR_ZERO(k);
 }
 
-static inline struct btree *btree_iter_node(struct btree_iter *iter,
+#define bkey_err(_k)	__bkey_err((_k).k)
+
+static inline void __btree_path_get(struct btree_path *path, bool intent)
+{
+	path->ref++;
+	path->intent_ref += intent;
+}
+
+static inline bool __btree_path_put(struct btree_path *path, bool intent)
+{
+	EBUG_ON(!path->ref);
+	EBUG_ON(!path->intent_ref && intent);
+	path->intent_ref -= intent;
+	return --path->ref == 0;
+}
+
+static inline void btree_path_set_dirty(struct btree_path *path,
+					enum btree_path_uptodate u)
+{
+	path->uptodate = max_t(unsigned, path->uptodate, u);
+}
+
+static inline struct btree *btree_path_node(struct btree_path *path,
 					    unsigned level)
 {
-	return level < BTREE_MAX_DEPTH ? iter->l[level].b : NULL;
+	return level < BTREE_MAX_DEPTH ? path->l[level].b : NULL;
 }
 
-static inline bool btree_node_lock_seq_matches(const struct btree_iter *iter,
+static inline bool btree_node_lock_seq_matches(const struct btree_path *path,
 					const struct btree *b, unsigned level)
 {
+	return path->l[level].lock_seq == six_lock_seq(&b->c.lock);
+}
+
+static inline struct btree *btree_node_parent(struct btree_path *path,
+					      struct btree *b)
+{
+	return btree_path_node(path, b->c.level + 1);
+}
+
+/* Iterate over paths within a transaction: */
+
+void __bch2_btree_trans_sort_paths(struct btree_trans *);
+
+static inline void btree_trans_sort_paths(struct btree_trans *trans)
+{
+	if (!IS_ENABLED(CONFIG_BCACHEFS_DEBUG) &&
+	    trans->paths_sorted)
+		return;
+	__bch2_btree_trans_sort_paths(trans);
+}
+
+static inline unsigned long *trans_paths_nr(struct btree_path *paths)
+{
+	return &container_of(paths, struct btree_trans_paths, paths[0])->nr_paths;
+}
+
+static inline unsigned long *trans_paths_allocated(struct btree_path *paths)
+{
+	unsigned long *v = trans_paths_nr(paths);
+	return v - BITS_TO_LONGS(*v);
+}
+
+#define trans_for_each_path_idx_from(_paths_allocated, _nr, _idx, _start)\
+	for (_idx = _start;						\
+	     (_idx = find_next_bit(_paths_allocated, _nr, _idx)) < _nr;	\
+	     _idx++)
+
+static inline struct btree_path *
+__trans_next_path(struct btree_trans *trans, unsigned *idx)
+{
+	unsigned long *w = trans->paths_allocated + *idx / BITS_PER_LONG;
 	/*
-	 * We don't compare the low bits of the lock sequence numbers because
-	 * @iter might have taken a write lock on @b, and we don't want to skip
-	 * the linked iterator if the sequence numbers were equal before taking
-	 * that write lock. The lock sequence number is incremented by taking
-	 * and releasing write locks and is even when unlocked:
+	 * Open coded find_next_bit(), because
+	 *  - this is fast path, we can't afford the function call
+	 *  - and we know that nr_paths is a multiple of BITS_PER_LONG,
 	 */
-	return iter->l[level].lock_seq >> 1 == b->lock.state.seq >> 1;
+	while (*idx < trans->nr_paths) {
+		unsigned long v = *w >> (*idx & (BITS_PER_LONG - 1));
+		if (v) {
+			*idx += __ffs(v);
+			return trans->paths + *idx;
+		}
+
+		*idx += BITS_PER_LONG;
+		*idx &= ~(BITS_PER_LONG - 1);
+		w++;
+	}
+
+	return NULL;
 }
 
-static inline struct btree *btree_node_parent(struct btree_iter *iter,
-					      struct btree *b)
+/*
+ * This version is intended to be safe for use on a btree_trans that is owned by
+ * another thread, for bch2_btree_trans_to_text();
+ */
+#define trans_for_each_path_from(_trans, _path, _idx, _start)		\
+	for (_idx = _start;						\
+	     (_path = __trans_next_path((_trans), &_idx));		\
+	     _idx++)
+
+#define trans_for_each_path(_trans, _path, _idx)			\
+	trans_for_each_path_from(_trans, _path, _idx, 1)
+
+static inline struct btree_path *next_btree_path(struct btree_trans *trans, struct btree_path *path)
 {
-	return btree_iter_node(iter, b->level + 1);
+	unsigned idx = path ? path->sorted_idx + 1 : 0;
+
+	EBUG_ON(idx > trans->nr_sorted);
+
+	return idx < trans->nr_sorted
+		? trans->paths + trans->sorted[idx]
+		: NULL;
 }
 
-static inline bool btree_trans_has_multiple_iters(const struct btree_trans *trans)
+static inline struct btree_path *prev_btree_path(struct btree_trans *trans, struct btree_path *path)
 {
-	return hweight64(trans->iters_linked) > 1;
+	unsigned idx = path ? path->sorted_idx : trans->nr_sorted;
+
+	return idx
+		? trans->paths + trans->sorted[idx - 1]
+		: NULL;
 }
 
-static inline int btree_iter_err(const struct btree_iter *iter)
+#define trans_for_each_path_idx_inorder(_trans, _iter)			\
+	for (_iter = (struct trans_for_each_path_inorder_iter) { 0 };	\
+	     (_iter.path_idx = trans->sorted[_iter.sorted_idx],		\
+	      _iter.sorted_idx < (_trans)->nr_sorted);			\
+	     _iter.sorted_idx++)
+
+struct trans_for_each_path_inorder_iter {
+	btree_path_idx_t	sorted_idx;
+	btree_path_idx_t	path_idx;
+};
+
+#define trans_for_each_path_inorder(_trans, _path, _iter)		\
+	for (_iter = (struct trans_for_each_path_inorder_iter) { 0 };	\
+	     (_iter.path_idx = trans->sorted[_iter.sorted_idx],		\
+	      _path = (_trans)->paths + _iter.path_idx,			\
+	      _iter.sorted_idx < (_trans)->nr_sorted);			\
+	     _iter.sorted_idx++)
+
+#define trans_for_each_path_inorder_reverse(_trans, _path, _i)		\
+	for (_i = trans->nr_sorted - 1;					\
+	     ((_path) = (_trans)->paths + trans->sorted[_i]), (_i) >= 0;\
+	     --_i)
+
+static inline bool __path_has_node(const struct btree_path *path,
+				   const struct btree *b)
 {
-	return iter->flags & BTREE_ITER_ERROR ? -EIO : 0;
+	return path->l[b->c.level].b == b &&
+		btree_node_lock_seq_matches(path, b, b->c.level);
 }
 
-/* Iterate over iters within a transaction: */
+static inline struct btree_path *
+__trans_next_path_with_node(struct btree_trans *trans, struct btree *b,
+			    unsigned *idx)
+{
+	struct btree_path *path;
 
-#define trans_for_each_iter_all(_trans, _iter)				\
-	for (_iter = (_trans)->iters;					\
-	     _iter < (_trans)->iters + (_trans)->nr_iters;		\
+	while ((path = __trans_next_path(trans, idx)) &&
+		!__path_has_node(path, b))
+	       (*idx)++;
+
+	return path;
+}
+
+#define trans_for_each_path_with_node(_trans, _b, _path, _iter)		\
+	for (_iter = 1;							\
+	     (_path = __trans_next_path_with_node((_trans), (_b), &_iter));\
 	     _iter++)
 
-static inline struct btree_iter *
-__trans_next_iter(struct btree_trans *trans, unsigned idx)
+btree_path_idx_t __bch2_btree_path_make_mut(struct btree_trans *, btree_path_idx_t,
+					    bool, unsigned long);
+
+static inline btree_path_idx_t __must_check
+bch2_btree_path_make_mut(struct btree_trans *trans,
+			 btree_path_idx_t path, bool intent,
+			 unsigned long ip)
 {
-	EBUG_ON(idx < trans->nr_iters && trans->iters[idx].idx != idx);
+	if (trans->paths[path].ref > 1 ||
+	    trans->paths[path].preserve)
+		path = __bch2_btree_path_make_mut(trans, path, intent, ip);
+	trans->paths[path].should_be_locked = false;
+	return path;
+}
 
-	for (; idx < trans->nr_iters; idx++)
-		if (trans->iters_linked & (1ULL << idx))
-			return &trans->iters[idx];
+btree_path_idx_t __must_check
+__bch2_btree_path_set_pos(struct btree_trans *, btree_path_idx_t,
+			  struct bpos, bool, unsigned long);
 
-	return NULL;
+static inline btree_path_idx_t __must_check
+bch2_btree_path_set_pos(struct btree_trans *trans,
+			btree_path_idx_t path, struct bpos new_pos,
+			bool intent, unsigned long ip)
+{
+	return !bpos_eq(new_pos, trans->paths[path].pos)
+		? __bch2_btree_path_set_pos(trans, path, new_pos, intent, ip)
+		: path;
 }
 
-#define trans_for_each_iter(_trans, _iter)				\
-	for (_iter = __trans_next_iter((_trans), 0);			\
-	     (_iter);							\
-	     _iter = __trans_next_iter((_trans), (_iter)->idx + 1))
+int __must_check bch2_btree_path_traverse_one(struct btree_trans *,
+					      btree_path_idx_t,
+					      unsigned, unsigned long);
 
-static inline bool __iter_has_node(const struct btree_iter *iter,
-				   const struct btree *b)
+static inline int __must_check bch2_btree_path_traverse(struct btree_trans *trans,
+					  btree_path_idx_t path, unsigned flags)
 {
-	return iter->l[b->level].b == b &&
-		btree_node_lock_seq_matches(iter, b, b->level);
+	if (trans->paths[path].uptodate < BTREE_ITER_NEED_RELOCK)
+		return 0;
+
+	return bch2_btree_path_traverse_one(trans, path, flags, _RET_IP_);
 }
 
-static inline struct btree_iter *
-__trans_next_iter_with_node(struct btree_trans *trans, struct btree *b,
-			    unsigned idx)
+btree_path_idx_t bch2_path_get(struct btree_trans *, enum btree_id, struct bpos,
+				 unsigned, unsigned, unsigned, unsigned long);
+struct bkey_s_c bch2_btree_path_peek_slot(struct btree_path *, struct bkey *);
+
+/*
+ * bch2_btree_path_peek_slot() for a cached iterator might return a key in a
+ * different snapshot:
+ */
+static inline struct bkey_s_c bch2_btree_path_peek_slot_exact(struct btree_path *path, struct bkey *u)
 {
-	struct btree_iter *iter = __trans_next_iter(trans, idx);
+	struct bkey_s_c k = bch2_btree_path_peek_slot(path, u);
 
-	while (iter && !__iter_has_node(iter, b))
-		iter = __trans_next_iter(trans, iter->idx + 1);
+	if (k.k && bpos_eq(path->pos, k.k->p))
+		return k;
 
-	return iter;
+	bkey_init(u);
+	u->p = path->pos;
+	return (struct bkey_s_c) { u, NULL };
 }
 
-#define trans_for_each_iter_with_node(_trans, _b, _iter)		\
-	for (_iter = __trans_next_iter_with_node((_trans), (_b), 0);	\
-	     (_iter);							\
-	     _iter = __trans_next_iter_with_node((_trans), (_b),	\
-						 (_iter)->idx + 1))
+struct bkey_i *bch2_btree_journal_peek_slot(struct btree_trans *,
+					struct btree_iter *, struct bpos);
+
+void bch2_btree_path_level_init(struct btree_trans *, struct btree_path *, struct btree *);
+
+int __bch2_trans_mutex_lock(struct btree_trans *, struct mutex *);
+
+static inline int bch2_trans_mutex_lock(struct btree_trans *trans, struct mutex *lock)
+{
+	return mutex_trylock(lock)
+		? 0
+		: __bch2_trans_mutex_lock(trans, lock);
+}
 
 #ifdef CONFIG_BCACHEFS_DEBUG
-void bch2_btree_trans_verify_iters(struct btree_trans *, struct btree *);
-void bch2_btree_trans_verify_locks(struct btree_trans *);
+void bch2_trans_verify_paths(struct btree_trans *);
+void bch2_assert_pos_locked(struct btree_trans *, enum btree_id,
+			    struct bpos, bool);
 #else
-static inline void bch2_btree_trans_verify_iters(struct btree_trans *trans,
-						 struct btree *b) {}
-static inline void bch2_btree_trans_verify_locks(struct btree_trans *iter) {}
+static inline void bch2_trans_verify_paths(struct btree_trans *trans) {}
+static inline void bch2_assert_pos_locked(struct btree_trans *trans, enum btree_id id,
+					  struct bpos pos, bool key_cache) {}
 #endif
 
-void bch2_btree_iter_fix_key_modified(struct btree_iter *, struct btree *,
-					   struct bkey_packed *);
-void bch2_btree_node_iter_fix(struct btree_iter *, struct btree *,
-			      struct btree_node_iter *, struct bkey_packed *,
-			      unsigned, unsigned);
+void bch2_btree_path_fix_key_modified(struct btree_trans *trans,
+				      struct btree *, struct bkey_packed *);
+void bch2_btree_node_iter_fix(struct btree_trans *trans, struct btree_path *,
+			      struct btree *, struct btree_node_iter *,
+			      struct bkey_packed *, unsigned, unsigned);
 
-bool bch2_trans_relock(struct btree_trans *);
-void bch2_trans_unlock(struct btree_trans *);
+int bch2_btree_path_relock_intent(struct btree_trans *, struct btree_path *);
 
-bool __bch2_btree_iter_upgrade(struct btree_iter *, unsigned);
-bool __bch2_btree_iter_upgrade_nounlock(struct btree_iter *, unsigned);
+void bch2_path_put(struct btree_trans *, btree_path_idx_t, bool);
+
+int bch2_trans_relock(struct btree_trans *);
+int bch2_trans_relock_notrace(struct btree_trans *);
+void bch2_trans_unlock(struct btree_trans *);
+void bch2_trans_unlock_long(struct btree_trans *);
+bool bch2_trans_locked(struct btree_trans *);
 
-static inline bool bch2_btree_iter_upgrade(struct btree_iter *iter,
-					   unsigned new_locks_want)
+static inline int trans_was_restarted(struct btree_trans *trans, u32 restart_count)
 {
-	new_locks_want = min(new_locks_want, BTREE_MAX_DEPTH);
+	return restart_count != trans->restart_count
+		? -BCH_ERR_transaction_restart_nested
+		: 0;
+}
+
+void __noreturn bch2_trans_restart_error(struct btree_trans *, u32);
 
-	return iter->locks_want < new_locks_want
-		? (!iter->trans->nounlock
-		   ? __bch2_btree_iter_upgrade(iter, new_locks_want)
-		   : __bch2_btree_iter_upgrade_nounlock(iter, new_locks_want))
-		: iter->uptodate <= BTREE_ITER_NEED_PEEK;
+static inline void bch2_trans_verify_not_restarted(struct btree_trans *trans,
+						   u32 restart_count)
+{
+	if (trans_was_restarted(trans, restart_count))
+		bch2_trans_restart_error(trans, restart_count);
 }
 
-void __bch2_btree_iter_downgrade(struct btree_iter *, unsigned);
+void __noreturn bch2_trans_in_restart_error(struct btree_trans *);
+
+static inline void bch2_trans_verify_not_in_restart(struct btree_trans *trans)
+{
+	if (trans->restarted)
+		bch2_trans_in_restart_error(trans);
+}
 
-static inline void bch2_btree_iter_downgrade(struct btree_iter *iter)
+__always_inline
+static int btree_trans_restart_nounlock(struct btree_trans *trans, int err)
 {
-	if (iter->locks_want > (iter->flags & BTREE_ITER_INTENT) ? 1 : 0)
-		__bch2_btree_iter_downgrade(iter, 0);
+	BUG_ON(err <= 0);
+	BUG_ON(!bch2_err_matches(-err, BCH_ERR_transaction_restart));
+
+	trans->restarted = err;
+	trans->last_restarted_ip = _THIS_IP_;
+	return -err;
 }
 
-void bch2_btree_iter_node_replace(struct btree_iter *, struct btree *);
-void bch2_btree_iter_node_drop(struct btree_iter *, struct btree *);
+__always_inline
+static int btree_trans_restart(struct btree_trans *trans, int err)
+{
+	btree_trans_restart_nounlock(trans, err);
+	return -err;
+}
 
-void bch2_btree_iter_reinit_node(struct btree_iter *, struct btree *);
+bool bch2_btree_node_upgrade(struct btree_trans *,
+			     struct btree_path *, unsigned);
 
-int __must_check __bch2_btree_iter_traverse(struct btree_iter *);
+void __bch2_btree_path_downgrade(struct btree_trans *, struct btree_path *, unsigned);
 
-static inline int __must_check
-bch2_btree_iter_traverse(struct btree_iter *iter)
+static inline void bch2_btree_path_downgrade(struct btree_trans *trans,
+					     struct btree_path *path)
 {
-	return iter->uptodate >= BTREE_ITER_NEED_RELOCK
-		? __bch2_btree_iter_traverse(iter)
-		: 0;
+	unsigned new_locks_want = path->level + !!path->intent_ref;
+
+	if (path->locks_want > new_locks_want)
+		__bch2_btree_path_downgrade(trans, path, new_locks_want);
 }
 
-int bch2_btree_iter_traverse_all(struct btree_trans *);
+void bch2_trans_downgrade(struct btree_trans *);
+
+void bch2_trans_node_add(struct btree_trans *trans, struct btree_path *, struct btree *);
+void bch2_trans_node_reinit_iter(struct btree_trans *, struct btree *);
+
+int __must_check __bch2_btree_iter_traverse(struct btree_iter *iter);
+int __must_check bch2_btree_iter_traverse(struct btree_iter *);
 
 struct btree *bch2_btree_iter_peek_node(struct btree_iter *);
+struct btree *bch2_btree_iter_peek_node_and_restart(struct btree_iter *);
 struct btree *bch2_btree_iter_next_node(struct btree_iter *);
 
-struct bkey_s_c bch2_btree_iter_peek(struct btree_iter *);
+struct bkey_s_c bch2_btree_iter_peek_upto(struct btree_iter *, struct bpos);
 struct bkey_s_c bch2_btree_iter_next(struct btree_iter *);
 
-struct bkey_s_c bch2_btree_iter_peek_with_updates(struct btree_iter *);
-struct bkey_s_c bch2_btree_iter_next_with_updates(struct btree_iter *);
+static inline struct bkey_s_c bch2_btree_iter_peek(struct btree_iter *iter)
+{
+	return bch2_btree_iter_peek_upto(iter, SPOS_MAX);
+}
 
 struct bkey_s_c bch2_btree_iter_peek_prev(struct btree_iter *);
 struct bkey_s_c bch2_btree_iter_prev(struct btree_iter *);
 
 struct bkey_s_c bch2_btree_iter_peek_slot(struct btree_iter *);
 struct bkey_s_c bch2_btree_iter_next_slot(struct btree_iter *);
+struct bkey_s_c bch2_btree_iter_prev_slot(struct btree_iter *);
 
-void bch2_btree_iter_set_pos_same_leaf(struct btree_iter *, struct bpos);
-void __bch2_btree_iter_set_pos(struct btree_iter *, struct bpos, bool);
-void bch2_btree_iter_set_pos(struct btree_iter *, struct bpos);
+bool bch2_btree_iter_advance(struct btree_iter *);
+bool bch2_btree_iter_rewind(struct btree_iter *);
 
-static inline int btree_iter_cmp(const struct btree_iter *l,
-				 const struct btree_iter *r)
+static inline void __bch2_btree_iter_set_pos(struct btree_iter *iter, struct bpos new_pos)
 {
-	return cmp_int(l->btree_id, r->btree_id) ?: bkey_cmp(l->pos, r->pos);
+	iter->k.type = KEY_TYPE_deleted;
+	iter->k.p.inode		= iter->pos.inode	= new_pos.inode;
+	iter->k.p.offset	= iter->pos.offset	= new_pos.offset;
+	iter->k.p.snapshot	= iter->pos.snapshot	= new_pos.snapshot;
+	iter->k.size = 0;
 }
 
-/*
- * Unlocks before scheduling
- * Note: does not revalidate iterator
- */
-static inline int bch2_trans_cond_resched(struct btree_trans *trans)
+static inline void bch2_btree_iter_set_pos(struct btree_iter *iter, struct bpos new_pos)
+{
+	struct btree_trans *trans = iter->trans;
+
+	if (unlikely(iter->update_path))
+		bch2_path_put(trans, iter->update_path,
+			      iter->flags & BTREE_ITER_INTENT);
+	iter->update_path = 0;
+
+	if (!(iter->flags & BTREE_ITER_ALL_SNAPSHOTS))
+		new_pos.snapshot = iter->snapshot;
+
+	__bch2_btree_iter_set_pos(iter, new_pos);
+}
+
+static inline void bch2_btree_iter_set_pos_to_extent_start(struct btree_iter *iter)
+{
+	BUG_ON(!(iter->flags & BTREE_ITER_IS_EXTENTS));
+	iter->pos = bkey_start_pos(&iter->k);
+}
+
+static inline void bch2_btree_iter_set_snapshot(struct btree_iter *iter, u32 snapshot)
+{
+	struct bpos pos = iter->pos;
+
+	iter->snapshot = snapshot;
+	pos.snapshot = snapshot;
+	bch2_btree_iter_set_pos(iter, pos);
+}
+
+void bch2_trans_iter_exit(struct btree_trans *, struct btree_iter *);
+
+static inline unsigned __bch2_btree_iter_flags(struct btree_trans *trans,
+					       unsigned btree_id,
+					       unsigned flags)
+{
+	if (!(flags & (BTREE_ITER_ALL_SNAPSHOTS|BTREE_ITER_NOT_EXTENTS)) &&
+	    btree_id_is_extents(btree_id))
+		flags |= BTREE_ITER_IS_EXTENTS;
+
+	if (!(flags & __BTREE_ITER_ALL_SNAPSHOTS) &&
+	    !btree_type_has_snapshot_field(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 (trans->journal_replay_not_finished)
+		flags |= BTREE_ITER_WITH_JOURNAL;
+
+	return flags;
+}
+
+static inline unsigned bch2_btree_iter_flags(struct btree_trans *trans,
+					     unsigned btree_id,
+					     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;
+
+	return __bch2_btree_iter_flags(trans, btree_id, flags);
+}
+
+static inline void bch2_trans_iter_init_common(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 (need_resched() || race_fault()) {
-		bch2_trans_unlock(trans);
-		schedule();
-		return bch2_trans_relock(trans) ? 0 : -EINTR;
+	iter->trans		= trans;
+	iter->update_path	= 0;
+	iter->key_cache_path	= 0;
+	iter->btree_id		= btree_id;
+	iter->min_depth		= 0;
+	iter->flags		= flags;
+	iter->snapshot		= pos.snapshot;
+	iter->pos		= pos;
+	iter->k			= POS_KEY(pos);
+	iter->journal_idx	= 0;
+#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_outlined(struct btree_trans *, struct btree_iter *,
+			  enum btree_id, struct bpos, unsigned);
+
+static inline void bch2_trans_iter_init(struct btree_trans *trans,
+			  struct btree_iter *iter,
+			  unsigned btree_id, struct bpos pos,
+			  unsigned flags)
+{
+	if (__builtin_constant_p(btree_id) &&
+	    __builtin_constant_p(flags))
+		bch2_trans_iter_init_common(trans, iter, btree_id, pos, 0, 0,
+				bch2_btree_iter_flags(trans, btree_id, flags),
+				_THIS_IP_);
+	else
+		bch2_trans_iter_init_outlined(trans, iter, btree_id, pos, flags);
+}
+
+void bch2_trans_node_iter_init(struct btree_trans *, struct btree_iter *,
+			       enum btree_id, struct bpos,
+			       unsigned, unsigned, unsigned);
+void bch2_trans_copy_iter(struct btree_iter *, struct btree_iter *);
+
+static inline void set_btree_iter_dontneed(struct btree_iter *iter)
+{
+	struct btree_trans *trans = iter->trans;
+
+	if (!trans->restarted)
+		btree_iter_path(trans, iter)->preserve = false;
+}
+
+void *__bch2_trans_kmalloc(struct btree_trans *, size_t);
+
+static inline void *bch2_trans_kmalloc(struct btree_trans *trans, size_t size)
+{
+	size = roundup(size, 8);
+
+	if (likely(trans->mem_top + size <= trans->mem_bytes)) {
+		void *p = trans->mem + trans->mem_top;
+
+		trans->mem_top += size;
+		memset(p, 0, size);
+		return p;
 	} else {
-		return 0;
+		return __bch2_trans_kmalloc(trans, size);
 	}
 }
 
-#define __for_each_btree_node(_trans, _iter, _btree_id, _start,	\
-			      _locks_want, _depth, _flags, _b)		\
-	for (iter = bch2_trans_get_node_iter((_trans), (_btree_id),	\
-				_start, _locks_want, _depth, _flags),	\
-	     _b = bch2_btree_iter_peek_node(_iter);			\
-	     (_b);							\
-	     (_b) = bch2_btree_iter_next_node(_iter))
+static inline void *bch2_trans_kmalloc_nomemzero(struct btree_trans *trans, size_t size)
+{
+	size = round_up(size, 8);
 
-#define for_each_btree_node(_trans, _iter, _btree_id, _start,		\
-			    _flags, _b)					\
-	__for_each_btree_node(_trans, _iter, _btree_id, _start,		\
-			      0, 0, _flags, _b)
+	if (likely(trans->mem_top + size <= trans->mem_bytes)) {
+		void *p = trans->mem + trans->mem_top;
+
+		trans->mem_top += size;
+		return p;
+	} else {
+		return __bch2_trans_kmalloc(trans, size);
+	}
+}
 
-static inline struct bkey_s_c __bch2_btree_iter_peek(struct btree_iter *iter,
-						     unsigned flags)
+static inline struct bkey_s_c __bch2_bkey_get_iter(struct btree_trans *trans,
+				struct btree_iter *iter,
+				unsigned btree_id, struct bpos pos,
+				unsigned flags, unsigned type)
 {
-	return flags & BTREE_ITER_SLOTS
-		? bch2_btree_iter_peek_slot(iter)
-		: bch2_btree_iter_peek(iter);
+	struct bkey_s_c k;
+
+	bch2_trans_iter_init(trans, iter, btree_id, pos, flags);
+	k = bch2_btree_iter_peek_slot(iter);
+
+	if (!bkey_err(k) && type && k.k->type != type)
+		k = bkey_s_c_err(-BCH_ERR_ENOENT_bkey_type_mismatch);
+	if (unlikely(bkey_err(k)))
+		bch2_trans_iter_exit(trans, iter);
+	return k;
 }
 
-static inline struct bkey_s_c __bch2_btree_iter_next(struct btree_iter *iter,
-						     unsigned flags)
+static inline struct bkey_s_c bch2_bkey_get_iter(struct btree_trans *trans,
+				struct btree_iter *iter,
+				unsigned btree_id, struct bpos pos,
+				unsigned flags)
 {
-	return flags & BTREE_ITER_SLOTS
-		? bch2_btree_iter_next_slot(iter)
-		: bch2_btree_iter_next(iter);
+	return __bch2_bkey_get_iter(trans, iter, btree_id, pos, flags, 0);
 }
 
-static inline int bkey_err(struct bkey_s_c k)
+#define bch2_bkey_get_iter_typed(_trans, _iter, _btree_id, _pos, _flags, _type)\
+	bkey_s_c_to_##_type(__bch2_bkey_get_iter(_trans, _iter,			\
+				       _btree_id, _pos, _flags, KEY_TYPE_##_type))
+
+static inline int __bch2_bkey_get_val_typed(struct btree_trans *trans,
+				unsigned btree_id, struct bpos pos,
+				unsigned flags, unsigned type,
+				unsigned val_size, void *val)
 {
-	return PTR_ERR_OR_ZERO(k.k);
+	struct btree_iter iter;
+	struct bkey_s_c k;
+	int ret;
+
+	k = __bch2_bkey_get_iter(trans, &iter, btree_id, pos, flags, type);
+	ret = bkey_err(k);
+	if (!ret) {
+		unsigned b = min_t(unsigned, bkey_val_bytes(k.k), val_size);
+
+		memcpy(val, k.v, b);
+		if (unlikely(b < sizeof(*val)))
+			memset((void *) val + b, 0, sizeof(*val) - b);
+		bch2_trans_iter_exit(trans, &iter);
+	}
+
+	return ret;
 }
 
-#define for_each_btree_key(_trans, _iter, _btree_id,			\
-			   _start, _flags, _k, _ret)			\
-	for ((_ret) = PTR_ERR_OR_ZERO((_iter) =				\
-			bch2_trans_get_iter((_trans), (_btree_id),	\
-					    (_start), (_flags))) ?:	\
-		      PTR_ERR_OR_ZERO(((_k) =				\
-			__bch2_btree_iter_peek(_iter, _flags)).k);	\
-	     !_ret && (_k).k;						\
-	     (_ret) = PTR_ERR_OR_ZERO(((_k) =				\
-			__bch2_btree_iter_next(_iter, _flags)).k))
-
-#define for_each_btree_key_continue(_iter, _flags, _k, _ret)		\
-	for ((_k) = __bch2_btree_iter_peek(_iter, _flags);		\
-	     !((_ret) = bkey_err(_k)) && (_k).k;			\
-	     (_k) = __bch2_btree_iter_next(_iter, _flags))
+#define bch2_bkey_get_val_typed(_trans, _btree_id, _pos, _flags, _type, _val)\
+	__bch2_bkey_get_val_typed(_trans, _btree_id, _pos, _flags,	\
+				  KEY_TYPE_##_type, sizeof(*_val), _val)
 
-/* new multiple iterator interface: */
+void bch2_trans_srcu_unlock(struct btree_trans *);
 
-int bch2_trans_iter_put(struct btree_trans *, struct btree_iter *);
-int bch2_trans_iter_free(struct btree_trans *, struct btree_iter *);
+u32 bch2_trans_begin(struct btree_trans *);
 
-void bch2_trans_unlink_iters(struct btree_trans *);
+/*
+ * XXX
+ * this does not handle transaction restarts from bch2_btree_iter_next_node()
+ * correctly
+ */
+#define __for_each_btree_node(_trans, _iter, _btree_id, _start,		\
+			      _locks_want, _depth, _flags, _b, _ret)	\
+	for (bch2_trans_node_iter_init((_trans), &(_iter), (_btree_id),	\
+				_start, _locks_want, _depth, _flags);	\
+	     (_b) = bch2_btree_iter_peek_node_and_restart(&(_iter)),	\
+	     !((_ret) = PTR_ERR_OR_ZERO(_b)) && (_b);			\
+	     (_b) = bch2_btree_iter_next_node(&(_iter)))
 
-struct btree_iter *__bch2_trans_get_iter(struct btree_trans *, enum btree_id,
-					 struct bpos, unsigned);
+#define for_each_btree_node(_trans, _iter, _btree_id, _start,		\
+			    _flags, _b, _ret)				\
+	__for_each_btree_node(_trans, _iter, _btree_id, _start,		\
+			      0, 0, _flags, _b, _ret)
 
-static inline struct btree_iter *
-bch2_trans_get_iter(struct btree_trans *trans, enum btree_id btree_id,
-		    struct bpos pos, unsigned flags)
+static inline struct bkey_s_c bch2_btree_iter_peek_prev_type(struct btree_iter *iter,
+							     unsigned flags)
 {
-	struct btree_iter *iter =
-		__bch2_trans_get_iter(trans, btree_id, pos, flags);
+	return  flags & BTREE_ITER_SLOTS      ? bch2_btree_iter_peek_slot(iter) :
+						bch2_btree_iter_peek_prev(iter);
+}
 
-	if (!IS_ERR(iter))
-		iter->ip_allocated = _THIS_IP_;
-	return iter;
+static inline struct bkey_s_c bch2_btree_iter_peek_type(struct btree_iter *iter,
+							unsigned flags)
+{
+	return  flags & BTREE_ITER_SLOTS      ? bch2_btree_iter_peek_slot(iter) :
+						bch2_btree_iter_peek(iter);
 }
 
-struct btree_iter *__bch2_trans_copy_iter(struct btree_trans *,
-					struct btree_iter *);
-static inline struct btree_iter *
-bch2_trans_copy_iter(struct btree_trans *trans, struct btree_iter *src)
+static inline struct bkey_s_c bch2_btree_iter_peek_upto_type(struct btree_iter *iter,
+							     struct bpos end,
+							     unsigned flags)
 {
-	struct btree_iter *iter =
-		__bch2_trans_copy_iter(trans, src);
+	if (!(flags & BTREE_ITER_SLOTS))
+		return bch2_btree_iter_peek_upto(iter, end);
 
-	if (!IS_ERR(iter))
-		iter->ip_allocated = _THIS_IP_;
-	return iter;
+	if (bkey_gt(iter->pos, end))
+		return bkey_s_c_null;
 
+	return bch2_btree_iter_peek_slot(iter);
 }
 
-struct btree_iter *bch2_trans_get_node_iter(struct btree_trans *,
-				enum btree_id, struct bpos,
-				unsigned, unsigned, unsigned);
+int __bch2_btree_trans_too_many_iters(struct btree_trans *);
 
-#define TRANS_RESET_NOTRAVERSE		(1 << 0)
+static inline int btree_trans_too_many_iters(struct btree_trans *trans)
+{
+	if (bitmap_weight(trans->paths_allocated, trans->nr_paths) > BTREE_ITER_INITIAL - 8)
+		return __bch2_btree_trans_too_many_iters(trans);
 
-void bch2_trans_reset(struct btree_trans *, unsigned);
+	return 0;
+}
+
+/*
+ * goto instead of loop, so that when used inside for_each_btree_key2()
+ * break/continue work correctly
+ */
+#define lockrestart_do(_trans, _do)					\
+({									\
+	__label__ transaction_restart;					\
+	u32 _restart_count;						\
+	int _ret2;							\
+transaction_restart:							\
+	_restart_count = bch2_trans_begin(_trans);			\
+	_ret2 = (_do);							\
+									\
+	if (bch2_err_matches(_ret2, BCH_ERR_transaction_restart))	\
+		goto transaction_restart;				\
+									\
+	if (!_ret2)							\
+		bch2_trans_verify_not_restarted(_trans, _restart_count);\
+	_ret2;								\
+})
+
+/*
+ * nested_lockrestart_do(), nested_commit_do():
+ *
+ * These are like lockrestart_do() and commit_do(), with two differences:
+ *
+ *  - We don't call bch2_trans_begin() unless we had a transaction restart
+ *  - We return -BCH_ERR_transaction_restart_nested if we succeeded after a
+ *  transaction restart
+ */
+#define nested_lockrestart_do(_trans, _do)				\
+({									\
+	u32 _restart_count, _orig_restart_count;			\
+	int _ret2;							\
+									\
+	_restart_count = _orig_restart_count = (_trans)->restart_count;	\
+									\
+	while (bch2_err_matches(_ret2 = (_do), BCH_ERR_transaction_restart))\
+		_restart_count = bch2_trans_begin(_trans);		\
+									\
+	if (!_ret2)							\
+		bch2_trans_verify_not_restarted(_trans, _restart_count);\
+									\
+	_ret2 ?: trans_was_restarted(_trans, _restart_count);		\
+})
+
+#define for_each_btree_key_upto(_trans, _iter, _btree_id,		\
+				_start, _end, _flags, _k, _do)		\
+({									\
+	struct btree_iter _iter;					\
+	struct bkey_s_c _k;						\
+	int _ret3 = 0;							\
+									\
+	bch2_trans_iter_init((_trans), &(_iter), (_btree_id),		\
+			     (_start), (_flags));			\
+									\
+	do {								\
+		_ret3 = lockrestart_do(_trans, ({			\
+			(_k) = bch2_btree_iter_peek_upto_type(&(_iter),	\
+						_end, (_flags));	\
+			if (!(_k).k)					\
+				break;					\
+									\
+			bkey_err(_k) ?: (_do);				\
+		}));							\
+	} while (!_ret3 && bch2_btree_iter_advance(&(_iter)));		\
+									\
+	bch2_trans_iter_exit((_trans), &(_iter));			\
+	_ret3;								\
+})
 
-static inline void bch2_trans_begin(struct btree_trans *trans)
+#define for_each_btree_key(_trans, _iter, _btree_id,			\
+			   _start, _flags, _k, _do)			\
+	for_each_btree_key_upto(_trans, _iter, _btree_id, _start,	\
+				 SPOS_MAX, _flags, _k, _do)
+
+#define for_each_btree_key_reverse(_trans, _iter, _btree_id,		\
+				   _start, _flags, _k, _do)		\
+({									\
+	struct btree_iter _iter;					\
+	struct bkey_s_c _k;						\
+	int _ret3 = 0;							\
+									\
+	bch2_trans_iter_init((_trans), &(_iter), (_btree_id),		\
+			     (_start), (_flags));			\
+									\
+	do {								\
+		_ret3 = lockrestart_do(_trans, ({			\
+			(_k) = bch2_btree_iter_peek_prev_type(&(_iter),	\
+							(_flags));	\
+			if (!(_k).k)					\
+				break;					\
+									\
+			bkey_err(_k) ?: (_do);				\
+		}));							\
+	} while (!_ret3 && bch2_btree_iter_rewind(&(_iter)));		\
+									\
+	bch2_trans_iter_exit((_trans), &(_iter));			\
+	_ret3;								\
+})
+
+#define for_each_btree_key_commit(_trans, _iter, _btree_id,		\
+				  _start, _iter_flags, _k,		\
+				  _disk_res, _journal_seq, _commit_flags,\
+				  _do)					\
+	for_each_btree_key(_trans, _iter, _btree_id, _start, _iter_flags, _k,\
+			    (_do) ?: bch2_trans_commit(_trans, (_disk_res),\
+					(_journal_seq), (_commit_flags)))
+
+#define for_each_btree_key_reverse_commit(_trans, _iter, _btree_id,	\
+				  _start, _iter_flags, _k,		\
+				  _disk_res, _journal_seq, _commit_flags,\
+				  _do)					\
+	for_each_btree_key_reverse(_trans, _iter, _btree_id, _start, _iter_flags, _k,\
+			    (_do) ?: bch2_trans_commit(_trans, (_disk_res),\
+					(_journal_seq), (_commit_flags)))
+
+#define for_each_btree_key_upto_commit(_trans, _iter, _btree_id,	\
+				  _start, _end, _iter_flags, _k,	\
+				  _disk_res, _journal_seq, _commit_flags,\
+				  _do)					\
+	for_each_btree_key_upto(_trans, _iter, _btree_id, _start, _end, _iter_flags, _k,\
+			    (_do) ?: bch2_trans_commit(_trans, (_disk_res),\
+					(_journal_seq), (_commit_flags)))
+
+struct bkey_s_c bch2_btree_iter_peek_and_restart_outlined(struct btree_iter *);
+
+static inline struct bkey_s_c
+__bch2_btree_iter_peek_and_restart(struct btree_trans *trans,
+				   struct btree_iter *iter, unsigned flags)
 {
-	return bch2_trans_reset(trans, 0);
+	struct bkey_s_c k;
+
+	while (btree_trans_too_many_iters(trans) ||
+	       (k = bch2_btree_iter_peek_type(iter, flags),
+		bch2_err_matches(bkey_err(k), BCH_ERR_transaction_restart)))
+		bch2_trans_begin(trans);
+
+	return k;
 }
 
-void *bch2_trans_kmalloc(struct btree_trans *, size_t);
-void bch2_trans_init(struct btree_trans *, struct bch_fs *, unsigned, size_t);
-int bch2_trans_exit(struct btree_trans *);
+#define for_each_btree_key_old(_trans, _iter, _btree_id,		\
+			   _start, _flags, _k, _ret)			\
+	for (bch2_trans_iter_init((_trans), &(_iter), (_btree_id),	\
+				  (_start), (_flags));			\
+	     (_k) = __bch2_btree_iter_peek_and_restart((_trans), &(_iter), _flags),\
+	     !((_ret) = bkey_err(_k)) && (_k).k;			\
+	     bch2_btree_iter_advance(&(_iter)))
+
+#define for_each_btree_key_upto_norestart(_trans, _iter, _btree_id,	\
+			   _start, _end, _flags, _k, _ret)		\
+	for (bch2_trans_iter_init((_trans), &(_iter), (_btree_id),	\
+				  (_start), (_flags));			\
+	     (_k) = bch2_btree_iter_peek_upto_type(&(_iter), _end, _flags),\
+	     !((_ret) = bkey_err(_k)) && (_k).k;			\
+	     bch2_btree_iter_advance(&(_iter)))
+
+#define for_each_btree_key_upto_continue_norestart(_iter, _end, _flags, _k, _ret)\
+	for (;									\
+	     (_k) = bch2_btree_iter_peek_upto_type(&(_iter), _end, _flags),	\
+	     !((_ret) = bkey_err(_k)) && (_k).k;				\
+	     bch2_btree_iter_advance(&(_iter)))
 
-void bch2_btree_trans_to_text(struct printbuf *, struct bch_fs *);
+#define for_each_btree_key_norestart(_trans, _iter, _btree_id,		\
+			   _start, _flags, _k, _ret)			\
+	for_each_btree_key_upto_norestart(_trans, _iter, _btree_id, _start,\
+					  SPOS_MAX, _flags, _k, _ret)
+
+#define for_each_btree_key_continue_norestart(_iter, _flags, _k, _ret)	\
+	for_each_btree_key_upto_continue_norestart(_iter, SPOS_MAX, _flags, _k, _ret)
+
+/*
+ * This should not be used in a fastpath, without first trying _do in
+ * nonblocking mode - it will cause excessive transaction restarts and
+ * potentially livelocking:
+ */
+#define drop_locks_do(_trans, _do)					\
+({									\
+	bch2_trans_unlock(_trans);					\
+	_do ?: bch2_trans_relock(_trans);				\
+})
+
+#define allocate_dropping_locks_errcode(_trans, _do)			\
+({									\
+	gfp_t _gfp = GFP_NOWAIT|__GFP_NOWARN;				\
+	int _ret = _do;							\
+									\
+	if (bch2_err_matches(_ret, ENOMEM)) {				\
+		_gfp = GFP_KERNEL;					\
+		_ret = drop_locks_do(trans, _do);			\
+	}								\
+	_ret;								\
+})
+
+#define allocate_dropping_locks(_trans, _ret, _do)			\
+({									\
+	gfp_t _gfp = GFP_NOWAIT|__GFP_NOWARN;				\
+	typeof(_do) _p = _do;						\
+									\
+	_ret = 0;							\
+	if (unlikely(!_p)) {						\
+		_gfp = GFP_KERNEL;					\
+		_ret = drop_locks_do(trans, ((_p = _do), 0));		\
+	}								\
+	_p;								\
+})
+
+void bch2_trans_updates_to_text(struct printbuf *, struct btree_trans *);
+void bch2_trans_paths_to_text(struct printbuf *, struct btree_trans *);
+void bch2_dump_trans_updates(struct btree_trans *);
+void bch2_dump_trans_paths_updates(struct btree_trans *);
+
+struct btree_trans *__bch2_trans_get(struct bch_fs *, unsigned);
+void bch2_trans_put(struct btree_trans *);
+
+extern const char *bch2_btree_transaction_fns[BCH_TRANSACTIONS_NR];
+unsigned bch2_trans_get_fn_idx(const char *);
+
+#define bch2_trans_get(_c)						\
+({									\
+	static unsigned trans_fn_idx;					\
+									\
+	if (unlikely(!trans_fn_idx))					\
+		trans_fn_idx = bch2_trans_get_fn_idx(__func__);		\
+	__bch2_trans_get(_c, trans_fn_idx);				\
+})
+
+void bch2_btree_trans_to_text(struct printbuf *, struct btree_trans *);
 
 void bch2_fs_btree_iter_exit(struct bch_fs *);
+void bch2_fs_btree_iter_init_early(struct bch_fs *);
 int bch2_fs_btree_iter_init(struct bch_fs *);
 
 #endif /* _BCACHEFS_BTREE_ITER_H */