On Thursday August 2, [EMAIL PROTECTED] wrote: > > This is pretty confusing. In all other places, bi_size -> #sector > conversion is done by rounding down but only in blk_rq_bio_prep() it's > being rounded up. > > Is my following reasoning correct? > > It was okay till now because unaligned requests don't get merged and > also haven't done partial completions (end_that_request_first with > partial count)? So till now, hard_nr_sectors and nr_sectors didn't > really matter for unaligned requests but now it matters because it's > considered while iterating over bvecs in rq.
Yes, that reasoning matches mine. > > If so, I think the correct thing to do would be changing bio_sectors() > to round up first or let block layer measure transfer in bytes not in > sectors. I don't think everyone would agree with the latter tho. I > (tentatively) think it would be better to represent length in bytes > tho. A lot of requests which aren't aligned to 512 bytes pass through > the block layer and the mismatch can result in subtle bugs. I suspect that having a byte count in 'struct request' would make sense too. However I would rather avoid making that change myself - I think it would require reading and understanding a lot more code.... I cannot see anything that would go wrong with rounding up bio_sectors unconditionally, so I think I will take that approach for this patch series. Thanks. NeilBrown - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
