EXTENT_BUFFER_STALE
clear_bit(EXTENT_BUFFER_STALE, &buf->bflags);
if (test_bit(EXTENT_BUFFER_STALE, &eb->bflags)) {
test_bit(EXTENT_BUFFER_STALE, &eb->bflags) &&
set_bit(EXTENT_BUFFER_STALE, &eb->bflags);