Re: [PATCH 7/10] i386 sg: add support for chaining scatterlists

[Jens Axboe <jens.axboe@oracle.com>]

On Wed, May 09 2007, Andrew Morton wrote:
> On Wed, 09 May 2007 20:03:29 +1000 Herbert Xu <herbert@gondor.apana.org.au> wrote:
> 
> > Jens Axboe <jens.axboe@oracle.com> wrote:
> > > 
> > > diff --git a/include/asm-i386/scatterlist.h b/include/asm-i386/scatterlist.h
> > > index d7e45a8..794b68c 100644
> > > --- a/include/asm-i386/scatterlist.h
> > > +++ b/include/asm-i386/scatterlist.h
> > > @@ -8,8 +8,11 @@ struct scatterlist {
> > >     unsigned int       offset;
> > >     dma_addr_t         dma_address;
> > >     unsigned int       length;
> > > +    struct scatterlist *next;
> > > };
> > 
> > BTW, the crypto layer's scatterlist already has a chaining mechanism
> > using the existing structure.  The only difference is that the chained
> > pointer is stored inside the 'struct page *' rather than a new pointer.
> 
> <greps-and-fails>
> 
> Which field in the page is it using?

crypto/scatterwalk.h:

static inline struct scatterlist *scatterwalk_sg_next(struct scatterlist
*sg)
{
        return (++sg)->length ? sg : (void *)sg->page;
}

it's just using the page pointer, not a pointer in the page structure.

-- 
Jens Axboe

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