bcachefs: Add iter->idx

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/btree_iter.c

@@ -1606,24 +1606,12 @@ static inline void bch2_btree_iter_init(struct btree_trans *trans,
 
 /* new transactional stuff: */
 
-static inline unsigned btree_trans_iter_idx(struct btree_trans *trans,
-					    struct btree_iter *iter)
-{
-	ssize_t idx = iter - trans->iters;
-
-	EBUG_ON(idx < 0 || idx >= trans->nr_iters);
-	EBUG_ON(!(trans->iters_linked & (1ULL << idx)));
-
-	return idx;
-}
-
 int bch2_trans_iter_put(struct btree_trans *trans,
 			struct btree_iter *iter)
 {
-	ssize_t idx = btree_trans_iter_idx(trans, iter);
 	int ret = btree_iter_err(iter);
 
-	trans->iters_live	&= ~(1ULL << idx);
+	trans->iters_live	&= ~(1ULL << iter->idx);
 	return ret;
 }
 
@@ -1643,7 +1631,7 @@ int bch2_trans_iter_free(struct btree_trans *trans,
 {
 	int ret = btree_iter_err(iter);
 
-	__bch2_trans_iter_free(trans, btree_trans_iter_idx(trans, iter));
+	__bch2_trans_iter_free(trans, iter->idx);
 	return ret;
 }
 
@@ -1652,8 +1640,7 @@ int bch2_trans_iter_free_on_commit(struct btree_trans *trans,
 {
 	int ret = btree_iter_err(iter);
 
-	trans->iters_unlink_on_commit |=
-		1ULL << btree_trans_iter_idx(trans, iter);
+	trans->iters_unlink_on_commit |= 1ULL << iter->idx;
 	return ret;
 }
 
@@ -1729,6 +1716,8 @@ static int btree_trans_iter_alloc(struct btree_trans *trans)
 
 	idx = trans->nr_iters++;
 	BUG_ON(trans->nr_iters > trans->size);
+
+	trans->iters[idx].idx = idx;
 got_slot:
 	BUG_ON(trans->iters_linked & (1ULL << idx));
 	trans->iters_linked |= 1ULL << idx;
@@ -1826,6 +1815,7 @@ struct btree_iter *bch2_trans_copy_iter(struct btree_trans *trans,
 					struct btree_iter *src)
 {
 	struct btree_iter *iter;
+	unsigned offset = offsetof(struct btree_iter, trans);
 	int i, idx;
 
 	idx = btree_trans_iter_alloc(trans);
@@ -1837,7 +1827,10 @@ struct btree_iter *bch2_trans_copy_iter(struct btree_trans *trans,
 	trans->iters_unlink_on_restart	|= 1ULL << idx;
 
 	iter = &trans->iters[idx];
-	*iter = *src;
+
+	memcpy((void *) iter + offset,
+	       (void *)  src + offset,
+	       sizeof(*iter) - offset);
 
 	for (i = 0; i < BTREE_MAX_DEPTH; i++)
 		if (btree_node_locked(iter, i))

fs/bcachefs/btree_iter.h

@@ -36,15 +36,11 @@ static inline int btree_iter_err(const struct btree_iter *iter)
 /* Iterate over iters within a transaction: */
 
 static inline struct btree_iter *
-__trans_next_iter(struct btree_trans *trans, struct btree_iter *iter)
+__trans_next_iter(struct btree_trans *trans, unsigned idx)
 {
-	unsigned idx;
+	EBUG_ON(idx < trans->nr_iters && trans->iters[idx].idx != idx);
 
-	/* XXX expensive pointer subtraction: */
-
-	for (idx = iter - trans->iters;
-	     idx < trans->nr_iters;
-	     idx++)
+	for (; idx < trans->nr_iters; idx++)
 		if (trans->iters_linked & (1ULL << idx))
 			return &trans->iters[idx];
 
@@ -52,9 +48,9 @@ __trans_next_iter(struct btree_trans *trans, struct btree_iter *iter)
 }
 
 #define trans_for_each_iter(_trans, _iter)				\
-	for (_iter = (_trans)->iters;					\
-	     (_iter = __trans_next_iter((_trans), _iter));		\
-	     _iter++)
+	for (_iter = __trans_next_iter((_trans), 0);			\
+	     (_iter);							\
+	     _iter = __trans_next_iter((_trans), (_iter)->idx + 1))
 
 static inline bool __iter_has_node(const struct btree_iter *iter,
 				   const struct btree *b)
@@ -73,30 +69,23 @@ static inline bool __iter_has_node(const struct btree_iter *iter,
 
 static inline struct btree_iter *
 __trans_next_iter_with_node(struct btree_trans *trans, struct btree *b,
-			    struct btree_iter *iter)
+			    unsigned idx)
 {
-	unsigned idx;
-
-	/* XXX expensive pointer subtraction: */
-
-	for (idx = iter - trans->iters;
-	     idx < trans->nr_iters;
-	     idx++) {
-		if (!(trans->iters_linked & (1ULL << idx)))
-			continue;
+	EBUG_ON(idx < trans->nr_iters && trans->iters[idx].idx != idx);
 
-		iter = &trans->iters[idx];
-		if (__iter_has_node(iter, b))
-			return iter;
-	}
+	for (; idx < trans->nr_iters; idx++)
+		if ((trans->iters_linked & (1ULL << idx)) &&
+		    __iter_has_node(&trans->iters[idx], b))
+			return &trans->iters[idx];
 
 	return NULL;
 }
 
 #define trans_for_each_iter_with_node(_trans, _b, _iter)		\
-	for (_iter = (_trans)->iters;					\
-	     (_iter = __trans_next_iter_with_node((_trans), (_b), _iter));\
-	     _iter++)
+	for (_iter = __trans_next_iter_with_node((_trans), (_b), 0);	\
+	     (_iter);							\
+	     _iter = __trans_next_iter_with_node((_trans), (_b),	\
+						 (_iter)->idx + 1))
 
 #ifdef CONFIG_BCACHEFS_DEBUG
 void bch2_btree_iter_verify(struct btree_iter *, struct btree *);

fs/bcachefs/btree_types.h

@@ -210,6 +210,8 @@ enum btree_iter_uptodate {
  * @nodes_intent_locked	- bitmask indicating which locks are intent locks
  */
 struct btree_iter {
+	u8			idx;
+
 	struct btree_trans	*trans;
 	struct bpos		pos;