Re: [PATCH v4] sd: Check for unaligned partial completion

[Bart Van Assche <Bart.VanAssche@sandisk.com>]

On Wed, 2017-02-15 at 11:12 +0900, Damien Le Moal wrote:
> +			resid = round_up(resid, sector_size);
> +			if (resid < good_bytes)
> +				good_bytes -= resid;
> +			else
> +				good_bytes = 0;
> +			scsi_set_resid(SCpnt, resid);

Hello Damien,

If the Data-Out buffer is smaller than a single logical block, can the above
code cause resid to exceed the Data-Out buffer size? I think we should avoid
to convert a residual overflow into a residual underflow. Additionally, will
round_up() work correctly if resid is negative (residual underflow)? How
about using the following (untested) code instead of the above?

if (resid > 0) {
        resid = min(good_bytes, round_up(resid, sector_size));
        good_bytes -= resid;
        scsi_set_resid(SCpnt, resid);
}

Thanks,

Bart.