if (unlikely(offsets.switch_old_end)) {
lib_ring_buffer_clear_noref(config, &buf->backend,
subbuf_index(offsets.old - 1, chan));
if (unlikely(offsets.switch_old_end)) {
lib_ring_buffer_clear_noref(config, &buf->backend,
subbuf_index(offsets.old - 1, chan));