From: edwardh <edwardh@synology.com>
To: axboe@kernel.dk, neilb@suse.com
Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
s3t@synology.com, bingjingc@synology.com, cccheng@synology.com,
Edward Hsieh <edwardh@synology.com>
Subject: [PATCH v2] block: fix trace completion for chained bio
Date: Wed, 3 Mar 2021 11:22:06 +0800 [thread overview]
Message-ID: <1614741726-28074-1-git-send-email-edwardh@synology.com> (raw)
From: Edward Hsieh <edwardh@synology.com>
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.
md/raid5 read with bio cross chunks can reproduce this issue.
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@synology.com>
Reviewed-by: BingJing Chang <bingjingc@synology.com>
Signed-off-by: Edward Hsieh <edwardh@synology.com>
---
block/bio.c | 13 ++++++-------
1 file changed, 6 insertions(+), 7 deletions(-)
diff --git a/block/bio.c b/block/bio.c
index a1c4d29..2ff72cb 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -1397,8 +1397,7 @@ 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)
{
@@ -1411,6 +1410,11 @@ void bio_endio(struct bio *bio)
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
@@ -1424,11 +1428,6 @@ void bio_endio(struct bio *bio)
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);
--
2.7.4
next reply other threads:[~2021-03-03 11:41 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-03 3:22 edwardh [this message]
2021-03-16 10:30 ` [PATCH v2] block: fix trace completion for chained bio Edward Hsieh
2021-03-22 21:22 ` NeilBrown
2021-04-23 8:04 ` Edward Hsieh
2021-05-10 2:06 ` Edward Hsieh
2021-05-25 9:37 ` Edward Hsieh
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