Re: [PATCH] block: fix residual byte count handling

[FUJITA Tomonori <tomof@acm.org>]

On Mon, 03 Mar 2008 22:38:55 +0900
Tejun Heo <htejun@gmail.com> wrote:

> FUJITA Tomonori wrote:
> > On Mon, 03 Mar 2008 18:21:13 +0900
> > Tejun Heo <htejun@gmail.com> 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.

I overlook it. Where does it changes sglist?