On Thu, May 10 2007, Benny Halevy wrote: > Jens Axboe wrote: > > +#define sg_is_chain(sg) ((unsigned long) (sg)->page & 0x01) > > +#define sg_chain_ptr(sg) \ > > + ((struct scatterlist *) ((unsigned long) (sg)->page & ~0x01)) > > + > > +/* > > + * We overload the meaning of ->page for sg chaining. If the LSB is > > + * set, the page member contains a pointer to the next sgtable. > > + */ > > +static inline struct scatterlist *sg_next(struct scatterlist *sg) > > +{ > > + if (sg_is_chain(sg)) > > + return sg_chain_ptr(sg); > > + > > + return sg + 1; > > +} > > Jens, should sg_next ever return the sg containing the chain link? > If sg points at the entry right before the link entry, don't we > want to skip it? > > E.g.: > > static inline struct scatterlist *sg_next(struct scatterlist *sg) > { > struct scatterlist *next; > > /* just in case, shouldn't really ever be here */ > if (sg_is_chain(sg)) > return sg_chain_ptr(sg); > > next = sg + 1; > > if (sg_is_chain(next)) > return sg_chain_ptr(next); > > return next; > }
You are right, I got that mixed up, I changed the setup to overloading ->page right before posting it. So: static inline struct scatterlist *sg_next(struct scatterlist *sg) { sg++; if (unlikely(sg_is_chain(sg))) sg = sg_chain_ptr(sg); return sg; } -- Jens Axboe - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/