PP_BUFFER_SIZE
kbuffer = kmalloc(min_t(size_t, count, PP_BUFFER_SIZE), GFP_KERNEL);
ssize_t need = min_t(unsigned long, count, PP_BUFFER_SIZE);
kbuffer = kmalloc(min_t(size_t, count, PP_BUFFER_SIZE), GFP_KERNEL);
ssize_t n = min_t(unsigned long, count - bytes_written, PP_BUFFER_SIZE);