dnode_cursor_next
dnode_cursor_next(zfs, c, foff));
bp = dnode_cursor_next(zfs, c,
dnode_cursor_next(zfs, c, 0));
blksz, loc, dnode_cursor_next(zfs, c, (i + 1) * blksz));
blkptr_t *dnode_cursor_next(zfs_opt_t *, struct dnode_cursor *, off_t);