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

Jens Axboe
2007-10-18T13:56:38Z

On Thu, Oct 18 2007, Benny Halevy wrote:
> On Oct. 18, 2007, 15:32 +0200, Jens Axboe <jens.axboe@oracle.com> wrote:
> > static inline struct scatterlist *sg_next(struct scatterlist *sg)
> > {
> > - sg++;
> > -
> > - if (unlikely(sg_is_chain(sg)))
> > +#ifdef CONFIG_DEBUG_SG
> > + BUG_ON(sg->sg_magic != SG_MAGIC);
> > +#endif
> > + if (sg_is_last(sg))
> > + sg = NULL;
> > + else if (sg_is_chain(sg))
> > sg = sg_chain_ptr(sg);
> > + else
> > + sg++;
> >
>
> Jens, again, please correct me if I'm wrong, but when sg points at the
> entry right before a chain entry this implementation of sg_next will
> return a pointer to the chain entry here, which I believe it must not.
>
> > return sg;
> > }
> >
>
> here's how I think sg_next should be implemented:
>
> */
> static inline struct scatterlist *sg_next(struct scatterlist *sg)
> {
> +#ifdef CONFIG_DEBUG_SG
> + BUG_ON(sg->sg_magic != SG_MAGIC);
> +#endif
> + if (sg_is_last(sg))
> + return NULL;
> +
> sg++;
>
> if (unlikely(sg_is_chain(sg)))
> sg = sg_chain_ptr(sg);
>
> return sg;
> }

Yep, thanks for catching that!

--
Jens Axboe