Re: [PATCH 05/14] block: don't call blk_status_to_errno() for success status

[Pavel Begunkov <asml.silence@gmail.com>]

On 10/17/21 01:37, Jens Axboe wrote:
> We only need to call it to resolve the blk_status_t -> errno mapping
> if the status is different than BLK_STS_OK. Check that it is before
> doing so.
> 
> Suggested-by: Christoph Hellwig <hch@infradead.org>
> Signed-off-by: Jens Axboe <axboe@kernel.dk>
> ---
>   block/blk-mq.c | 6 ++++--
>   1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index ffccc5f0f66a..fa5b12200404 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -676,9 +676,11 @@ static void blk_account_io_completion(struct request *req, unsigned int bytes)
>   bool blk_update_request(struct request *req, blk_status_t error,
>   		unsigned int nr_bytes)
>   {
> -	int total_bytes;
> +	int total_bytes, blk_errno = 0;
>   
> -	trace_block_rq_complete(req, blk_status_to_errno(error), nr_bytes);
> +	if (unlikely(error != BLK_STS_OK))
> +		blk_errno = blk_status_to_errno(error);
> +	trace_block_rq_complete(req, blk_errno, nr_bytes);

Last time I checked relevant asm, the inference of arguments was done
under the trace branch, so no extra work if tracing is not active.


>   
>   	if (!req->bio)
>   		return false;
> 

-- 
Pavel Begunkov