bcachefs: Trace where btree iterators are allocated

This will help with iterator overflow bugs.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/btree_iter.c

@@ -1912,13 +1912,14 @@ static struct btree_iter *btree_trans_iter_alloc(struct btree_trans *trans)
 			struct btree_iter *iter;
 
 			trans_for_each_iter(trans, iter) {
-				pr_err("iter: btree %s pos %llu:%llu%s%s%s",
+				pr_err("iter: btree %s pos %llu:%llu%s%s%s %pf",
 				       bch2_btree_ids[iter->btree_id],
 				       iter->pos.inode,
 				       iter->pos.offset,
 				       (trans->iters_live & (1ULL << iter->idx)) ? " live" : "",
 				       (trans->iters_touched & (1ULL << iter->idx)) ? " touched" : "",
-				       iter->flags & BTREE_ITER_KEEP_UNTIL_COMMIT ? " keep" : "");
+				       iter->flags & BTREE_ITER_KEEP_UNTIL_COMMIT ? " keep" : "",
+				       (void *) iter->ip_allocated);
 			}
 
 			panic("trans iter oveflow\n");
@@ -2025,7 +2026,7 @@ static struct btree_iter *__btree_trans_get_iter(struct btree_trans *trans,
 	return iter;
 }
 
-struct btree_iter *bch2_trans_get_iter(struct btree_trans *trans,
+struct btree_iter *__bch2_trans_get_iter(struct btree_trans *trans,
 					 enum btree_id btree_id,
 					 struct bpos pos, unsigned flags)
 {
@@ -2064,7 +2065,7 @@ struct btree_iter *bch2_trans_get_node_iter(struct btree_trans *trans,
 	return iter;
 }
 
-struct btree_iter *bch2_trans_copy_iter(struct btree_trans *trans,
+struct btree_iter *__bch2_trans_copy_iter(struct btree_trans *trans,
 					struct btree_iter *src)
 {
 	struct btree_iter *iter;

fs/bcachefs/btree_iter.h

@@ -257,10 +257,35 @@ int bch2_trans_iter_free(struct btree_trans *, struct btree_iter *);
 
 void bch2_trans_unlink_iters(struct btree_trans *);
 
-struct btree_iter *bch2_trans_get_iter(struct btree_trans *, enum btree_id,
+struct btree_iter *__bch2_trans_get_iter(struct btree_trans *, enum btree_id,
 					 struct bpos, unsigned);
-struct btree_iter *bch2_trans_copy_iter(struct btree_trans *,
+
+static inline struct btree_iter *
+bch2_trans_get_iter(struct btree_trans *trans, enum btree_id btree_id,
+		    struct bpos pos, unsigned flags)
+{
+	struct btree_iter *iter =
+		__bch2_trans_get_iter(trans, btree_id, pos, flags);
+
+	if (!IS_ERR(iter))
+		iter->ip_allocated = _THIS_IP_;
+	return 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)
+{
+	struct btree_iter *iter =
+		__bch2_trans_copy_iter(trans, src);
+
+	if (!IS_ERR(iter))
+		iter->ip_allocated = _THIS_IP_;
+	return iter;
+
+}
+
 struct btree_iter *bch2_trans_get_node_iter(struct btree_trans *,
 				enum btree_id, struct bpos,
 				unsigned, unsigned, unsigned);

fs/bcachefs/btree_types.h

@@ -256,6 +256,7 @@ struct btree_iter {
 	 * bch2_btree_iter_next_slot() can correctly advance pos.
 	 */
 	struct bkey		k;
+	unsigned long		ip_allocated;
 };
 
 static inline enum btree_iter_type btree_iter_type(struct btree_iter *iter)