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Message-Id: <20210712061012.579182430@linuxfoundation.org>
Date: Mon, 12 Jul 2021 08:07:04 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-kernel@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
stable@...r.kernel.org, Wade Liang <wadel@...ology.com>,
BingJing Chang <bingjingc@...ology.com>,
Edward Hsieh <edwardh@...ology.com>,
Christoph Hellwig <hch@....de>, Jens Axboe <axboe@...nel.dk>,
Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.12 341/700] block: fix trace completion for chained bio
From: Edward Hsieh <edwardh@...ology.com>
[ Upstream commit 60b6a7e6a0f4382cd689f9afdac816964fec2921 ]
For chained bio, trace_block_bio_complete in bio_endio is currently called
only by the parent bio once upon all chained bio completed.
However, the sector and size for the parent bio are modified in bio_split.
Therefore, the size and sector of the complete events might not match the
queue events in blktrace.
The original fix of bio completion trace <fbbaf700e7b1> ("block: trace
completion of all bios.") wants multiple complete events to correspond
to one queue event but missed this.
The issue can be reproduced by md/raid5 read with bio cross chunks.
To fix, move trace completion into the loop for every chained bio to call.
Fixes: fbbaf700e7b1 ("block: trace completion of all bios.")
Reviewed-by: Wade Liang <wadel@...ology.com>
Reviewed-by: BingJing Chang <bingjingc@...ology.com>
Signed-off-by: Edward Hsieh <edwardh@...ology.com>
Reviewed-by: Christoph Hellwig <hch@....de>
Link: https://lore.kernel.org/r/20210624123030.27014-1-edwardh@synology.com
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
block/bio.c | 13 ++++++-------
1 file changed, 6 insertions(+), 7 deletions(-)
diff --git a/block/bio.c b/block/bio.c
index 50e579088aca..b00c5a88a743 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -1412,8 +1412,7 @@ static inline bool bio_remaining_done(struct bio *bio)
*
* bio_endio() can be called several times on a bio that has been chained
* using bio_chain(). The ->bi_end_io() function will only be called the
- * last time. At this point the BLK_TA_COMPLETE tracing event will be
- * generated if BIO_TRACE_COMPLETION is set.
+ * last time.
**/
void bio_endio(struct bio *bio)
{
@@ -1426,6 +1425,11 @@ again:
if (bio->bi_bdev)
rq_qos_done_bio(bio->bi_bdev->bd_disk->queue, bio);
+ if (bio->bi_bdev && bio_flagged(bio, BIO_TRACE_COMPLETION)) {
+ trace_block_bio_complete(bio->bi_bdev->bd_disk->queue, bio);
+ bio_clear_flag(bio, BIO_TRACE_COMPLETION);
+ }
+
/*
* Need to have a real endio function for chained bios, otherwise
* various corner cases will break (like stacking block devices that
@@ -1439,11 +1443,6 @@ again:
goto again;
}
- if (bio->bi_bdev && bio_flagged(bio, BIO_TRACE_COMPLETION)) {
- trace_block_bio_complete(bio->bi_bdev->bd_disk->queue, bio);
- bio_clear_flag(bio, BIO_TRACE_COMPLETION);
- }
-
blk_throtl_bio_endio(bio);
/* release cgroup info */
bio_uninit(bio);
--
2.30.2
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