linux-kernel - Re: [PATCH] blk-iolatency: only account submitted bios

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Message-ID: <20190615165149.GA96756@dennisz-mbp.dhcp.thefacebook.com>
Date:   Sat, 15 Jun 2019 12:51:49 -0400
From:   Dennis Zhou <dennis@...nel.org>
To:     Jens Axboe <axboe@...nel.dk>
Cc:     Dennis Zhou <dennis@...nel.org>,
        Josef Bacik <josef@...icpanda.com>, kernel-team@...com,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] blk-iolatency: only account submitted bios

Hi Jens,

On Thu, May 23, 2019 at 04:10:18PM -0400, Dennis Zhou wrote:
> As is, iolatency recognizes done_bio and cleanup as ending paths. If a
> request is marked REQ_NOWAIT and fails to get a request, the bio is
> cleaned up via rq_qos_cleanup() and ended in bio_wouldblock_error().
> This results in underflowing the inflight counter. Fix this by only
> accounting bios that were actually submitted.
> 
> Signed-off-by: Dennis Zhou <dennis@...nel.org>
> Cc: Josef Bacik <josef@...icpanda.com>
> ---
>  block/blk-iolatency.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/block/blk-iolatency.c b/block/blk-iolatency.c
> index 507212d75ee2..58bac44ba78a 100644
> --- a/block/blk-iolatency.c
> +++ b/block/blk-iolatency.c
> @@ -599,6 +599,10 @@ static void blkcg_iolatency_done_bio(struct rq_qos *rqos, struct bio *bio)
>  	if (!blkg || !bio_flagged(bio, BIO_TRACKED))
>  		return;
>  
> +	/* We didn't actually submit this bio, don't account it. */
> +	if (bio->bi_status == BLK_STS_AGAIN)
> +		return;
> +
>  	iolat = blkg_to_lat(bio->bi_blkg);
>  	if (!iolat)
>  		return;
> -- 
> 2.17.1
> 

Can you please take a look at this?

Thanks,
Dennis