FUJITA Tomonori wrote: > On Mon, 03 Mar 2008 18:21:13 +0900 > Tejun Heo <htejun@xxxxxxxxx> wrote: > >> FUJITA Tomonori wrote: >>>>> I can't see what changing the meaning of rq->data_len (and >>>>> investigating all the block drivers) gives us. >>>> No matter which way you go, you change the meaning of rq->data_len and >>>> you MUST inspect rq->data_len usage whichever way you go. >>> The patch doens't change that rq->data_len means the true data >>> length. But yeah, it breaks rq->data_len == sum(sg). So it might break >>> some drivers. >> Yeah, that's what I was saying. You end up breaking one of the two >> assumptions. As sglist is getting modified for any driver if it has DMA >> alignment set, whether rq->data_len is adjusted together or not, sglist >> and data_len usages have to be audited. > > My patch (well, James' original approach) doesn't affect drivers that > don't use drain buffer. rq->data_len still means the true data length > and rq->data_len is equal to sum(sg) for them. So right now we need to > audit only libata. Your patch does change sglist for any driver which sets DMA alignment. You'll definitely need to audit more than libata. > But your patch changes the meaning of rq->data_len. It affects all the > drivers. So it breaks non libata stuff, like the SMP handler. We need > to audit all the drivers. With both patches applied, sglist and data_len are adjusted only for libata, so only drivers which explicitly requested buffer size manipulation (currently only libata) need to be audited / updated. -- tejun -- To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
