Re: [bug] ata subsystem related crash with latest -git

Jens Axboe
2007-10-18T17:14:42Z

On Thu, Oct 18 2007, Arjan van de Ven wrote:
> On Thu, 18 Oct 2007 09:55:04 -0700 (PDT)
> Linus Torvalds <torvalds@linux-foundation.org> wrote:
>
> >
> >
> > On Thu, 18 Oct 2007, Jens Axboe wrote:
> > > - unsigned long addr = page_to_phys(s->page) +
> > > s->offset;
> > > + unsigned long addr = page_to_phys(sg_page(s)) +
> > > s->offset;
> >
> > Umm. May I suggest (I haven't read the whole thread yet, maybe
> > somebody else already did) that
> >
> > static inline unsigned long sg_phys(struct scatterlist *sg)
> > {
> > return page_to_phys(sg_page(sg)) + sg->offset;
> > }
> >
> > would be a good thing to have?
> >
> > Very few drivers should care so much about the *page* itself (or the
> > offset). That's something that the generic allocation code etc cares
> > about, but the driver is almost bound to care mostly about the actual
> > DMA address
>
> .... but will that work for systems with IOMMU ? or is it fundamentally
> the wrong interface

They use foo_to_bus() on the address. sg_phys() should of course only be
used where the user previously did page_to_phys() on the sg page.

--
Jens Axboe