linux-kernel - Re: [PATCH AUTOSEL 5.2 129/249] blk-iolatency: only account submitted bios

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Date:   Sun, 21 Jul 2019 20:39:50 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     Dennis Zhou <dennis@...nel.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Josef Bacik <josef@...icpanda.com>,
        Jens Axboe <axboe@...nel.dk>, linux-block@...r.kernel.org
Subject: Re: [PATCH AUTOSEL 5.2 129/249] blk-iolatency: only account
 submitted bios

On Mon, Jul 15, 2019 at 03:58:06PM -0400, Dennis Zhou wrote:
>On Mon, Jul 15, 2019 at 09:44:54AM -0400, Sasha Levin wrote:
>> From: Dennis Zhou <dennis@...nel.org>
>>
>> [ Upstream commit a3fb01ba5af066521f3f3421839e501bb2c71805 ]
>>
>> 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>
>> Signed-off-by: Jens Axboe <axboe@...nel.dk>
>> Signed-off-by: Sasha Levin <sashal@...nel.org>
>> ---
>>  block/blk-iolatency.c | 4 ++++
>>  1 file changed, 4 insertions(+)
>>
>> diff --git a/block/blk-iolatency.c b/block/blk-iolatency.c
>> index d22e61bced86..c91b84bb9d0a 100644
>> --- a/block/blk-iolatency.c
>> +++ b/block/blk-iolatency.c
>> @@ -600,6 +600,10 @@ 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;
>> --
>> 2.20.1
>>
>
>Hi Sasha,
>
>If you're going to pick this up, c9b3007feca0 ("blk-iolatency: fix
>STS_AGAIN handling") fixes this patch, so please pick that up too.

I've picked it up, thanks!

--
Thanks,
Sasha