On Mon, Nov 14, 2016 at 10:03:20AM +1100, NeilBrown wrote: > I would suggest adding a "bi_dev_private" field to the bio which is for > use by the lowest-level driver (much as bi_private is for use by the > top-level initiator). > That could be in a union with any or all of: > unsigned int bi_phys_segments; > unsigned int bi_seg_front_size; > unsigned int bi_seg_back_size; > > (any driver that needs those, would see a 'request' rather than a 'bio' > and so could use rq->special) > > raid5.c could then use bi_dev_private (or bi_special, or whatever it is call). All the three above fields are those that could go away with a full implementation of the multipage bvec scheme. So any field for driver use would still be be overhead. If it's just for raid5 it could be a smaller 16 bit (or maybe even just 8 bit) one. -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
