Re: [PATCH V3] block: fix the DISCARD request merge

[Christoph Hellwig]

> -	/*
> -	 * not contiguous
> -	 */
> -	if (blk_rq_pos(req) + blk_rq_sectors(req) != blk_rq_pos(next))
> -		return NULL;
> -

As suggested previously I think we want something like blk_try_merge
and its return values here.  Maybe a blk_try_req_merge that takes
requests instead of bios.