#define EXTENT_FLAG_PREALLOC 3 /* pre-allocated extent */
#define EXTENT_FLAG_LOGGING 4 /* Logging this extent */
#define EXTENT_FLAG_FILLING 5 /* Filling in a preallocated extent */
+#define EXTENT_FLAG_FS_MAPPING 6 /* filesystem extent mapping type */
struct extent_map {
struct rb_node rb_node;