LOCAL_BUF_LEN
char head[LOCAL_BUF_LEN];
char tmp[LOCAL_BUF_LEN];
BUG_ON(shift > LOCAL_BUF_LEN);
for (i = 0; i + shift < buf->len; i += LOCAL_BUF_LEN) {
this_len = min(LOCAL_BUF_LEN, buf->len - (i + shift));
this_shift = min(shift - shifted, LOCAL_BUF_LEN);