efipart_readwrite
rc = efipart_readwrite(blkio, rw, blk, x, blkbuf);
rc = efipart_readwrite(blkio, F_READ, blk, x,
rc = efipart_readwrite(blkio, F_READ, blk, x,
rc = efipart_readwrite(blkio, F_WRITE, blk, x, blkbuf);