[Drbd-dev] [RFC PATCH 01/17] block: make generic_make_request handle arbitrarily sized bios

[Christoph Hellwig]

> +void blk_queue_split(struct request_queue *q, struct bio **bio,
> +		     struct bio_set *bs)
> +{
> +	struct bio *split;
> +
> +	if ((*bio)->bi_rw & REQ_DISCARD)
> +		split = blk_bio_discard_split(q, *bio, bs);
> +	else if ((*bio)->bi_rw & REQ_WRITE_SAME)
> +		split = blk_bio_write_same_split(q, *bio, bs);
> +	else
> +		split = blk_bio_segment_split(q, *bio, q->bio_split);
> +
> +	if (split) {
> +		bio_chain(split, *bio);
> +		generic_make_request(*bio);
> +		*bio = split;
> +	}
> +}
> +EXPORT_SYMBOL(blk_queue_split);

I think blk_queue_split needs to explicitly skip BLOCK_PC bios.  Those
are SCSI pass through ioctls that we can't split due to their opaque
nature.