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

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Message-Id: <20190523201018.49615-1-dennis@kernel.org>
Date:   Thu, 23 May 2019 16:10:18 -0400
From:   Dennis Zhou <dennis@...nel.org>
To:     Jens Axboe <axboe@...nel.dk>, Josef Bacik <josef@...icpanda.com>
Cc:     kernel-team@...com, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org, Dennis Zhou <dennis@...nel.org>
Subject: [PATCH] blk-iolatency: only account submitted bios

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