Re: [PATCH] Fix discard requests accounting in the diskstats

[Andrew Morton]

On Fri, 17 Apr 2009 11:44:49 +0530
Nikanth Karthikesan <knikanth@xxxxxxx> wrote:

> --- a/include/linux/blkdev.h
> +++ b/include/linux/blkdev.h
> @@ -667,7 +667,9 @@ static inline void blk_clear_queue_full(struct request_queue *q, int sync)
>  	(REQ_NOMERGE | REQ_STARTED | REQ_HARDBARRIER | REQ_SOFTBARRIER)
>  #define rq_mergeable(rq)	\
>  	(!((rq)->cmd_flags & RQ_NOMERGE_FLAGS) && \
> -	 (blk_discard_rq(rq) || blk_fs_request((rq))))
> +	 (blk_discard_rq(rq) || blk_fs_request(rq)))
> +#define rq_accountable(rq)	\
> +	(blk_discard_rq(rq) || blk_fs_request(rq))

Both these macros reference their argument multiple times and are
potentially buggy and/or inefficient if passed an expression with
side-effects.

There was (afaict) no reason for them to have been implemented as
macros.

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