Re: [PATCH 1/5] block: Implement support for WRITE SAME

[Vivek Goyal <vgoyal@redhat.com>]

On Mon, Jan 30, 2012 at 07:31:28PM -0500, Martin K. Petersen wrote:

[..]
> --- a/block/elevator.c
> +++ b/block/elevator.c
> @@ -82,6 +82,12 @@ int elv_rq_merge_ok(struct request *rq, struct bio *bio)
>  		return 0;
>  
>  	/*
> +	 * Don't merge write same requests
> +	 */
> +	if ((bio->bi_rw & REQ_WRITE_SAME) || (rq->bio->bi_rw & REQ_WRITE_SAME))
> +		return 0;
> +


[..]
>  #define rq_mergeable(rq)	\
>  	(!((rq)->cmd_flags & RQ_NOMERGE_FLAGS) && \
> -	 (((rq)->cmd_flags & REQ_DISCARD) || \
> -	  (rq)->cmd_type == REQ_TYPE_FS))
> +	 (((rq)->cmd_flags & REQ_DISCARD || \
> +	   (rq)->cmd_flags & REQ_WRITE_SAME ||	\
> +	   (rq)->cmd_type == REQ_TYPE_FS)))

In elv_rq_merge_ok() we don't allow merge of WRITE_SAME requests but
in rq_mergeable() we do say that requests having WRITE_SAME can be merged.

Thanks
Vivek