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

Benny Halevy
2007-10-18T13:50:48Z

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;
}