perf_data_size
userpg->data_size = perf_data_size(rb);
atomic_long_sub((perf_data_size(rb) >> PAGE_SHIFT) + 1 - rb->mmap_locked,
if (aux_offset < perf_data_size(rb) + PAGE_SIZE)
perf_data_size(rb),
long max_size = perf_data_size(rb);