ubifs_wbuf_seek_nolock
err = ubifs_wbuf_seek_nolock(wbuf, gc_lnum, 0);
err = ubifs_wbuf_seek_nolock(wbuf, lnum, offs);
err = ubifs_wbuf_seek_nolock(&c->jheads[b->bud->jhead].wbuf,
int ubifs_wbuf_seek_nolock(struct ubifs_wbuf *wbuf, int lnum, int offs);