[dm-devel] [PATCH 42/41] dm: convey that all flushes are processed as empty

[Christoph Hellwig]

On Tue, Sep 07, 2010 at 07:49:18PM -0400, Mike Snitzer wrote:
>  		if (!(bio->bi_rw & REQ_FLUSH) || !bio->bi_size) {
> +			/* done with normal IO or empty flush */
>  			trace_block_bio_complete(md->queue, bio);
>  			bio_endio(bio, io_error);
>  		} else {

To clarify this further I'd reorder the checks:

		if ((bio->bi_rw & REQ_FLUSH) && bio->bi_size) {
			/*
			 * Preflush done, ...
			 */
		} else {
		}

> @@ -1302,20 +1302,17 @@ static void __split_and_process_bio(struct mapped_device *md, struct bio *bio)
>  	ci.sector = bio->bi_sector;
>  	ci.idx = bio->bi_idx;
>  
> +	start_io_acct(ci.io);
>  	if (!is_flush) {

no need for the is_flush anymore now that it's only used once.  Again,
I think avoiding negatives without a reason in if statement usually
makes the code a bit more clear.