bcachefs: for_each_btree_key_in_subvolume_upto()

New helper for looping over keys in a given subvolume
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/subvolume.h

@@ -31,6 +31,51 @@ int bch2_subvolume_get_snapshot(struct btree_trans *, u32, u32 *);
 int bch2_subvol_is_ro_trans(struct btree_trans *, u32);
 int bch2_subvol_is_ro(struct bch_fs *, u32);
 
+static inline struct bkey_s_c
+bch2_btree_iter_peek_in_subvolume_upto_type(struct btree_iter *iter, struct bpos end,
+					    u32 subvolid, unsigned flags)
+{
+	u32 snapshot;
+	int ret = bch2_subvolume_get_snapshot(iter->trans, subvolid, &snapshot);
+	if (ret)
+		return bkey_s_c_err(ret);
+
+	bch2_btree_iter_set_snapshot(iter, snapshot);
+	return bch2_btree_iter_peek_upto_type(iter, end, flags);
+}
+
+#define for_each_btree_key_in_subvolume_upto_continue(_trans, _iter,		\
+					 _end, _subvolid, _flags, _k, _do)	\
+({										\
+	struct bkey_s_c _k;							\
+	int _ret3 = 0;								\
+										\
+	do {									\
+		_ret3 = lockrestart_do(_trans, ({				\
+			(_k) = bch2_btree_iter_peek_in_subvolume_upto_type(&(_iter),	\
+						_end, _subvolid, (_flags));	\
+			if (!(_k).k)						\
+				break;						\
+										\
+			bkey_err(_k) ?: (_do);					\
+		}));								\
+	} while (!_ret3 && bch2_btree_iter_advance(&(_iter)));			\
+										\
+	bch2_trans_iter_exit((_trans), &(_iter));				\
+	_ret3;									\
+})
+
+#define for_each_btree_key_in_subvolume_upto(_trans, _iter, _btree_id,		\
+				_start, _end, _subvolid, _flags, _k, _do)	\
+({										\
+	struct btree_iter _iter;						\
+	bch2_trans_iter_init((_trans), &(_iter), (_btree_id),			\
+			     (_start), (_flags));				\
+										\
+	for_each_btree_key_in_subvolume_upto_continue(_trans, _iter,		\
+					_end, _subvolid, _flags, _k, _do);	\
+})
+
 int bch2_delete_dead_snapshots(struct bch_fs *);
 void bch2_delete_dead_snapshots_async(struct bch_fs *);