linux-block.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
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


             reply	other threads:[~2021-03-03 16:41 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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=1614741726-28074-1-git-send-email-edwardh@synology.com \
    --to=edwardh@synology.com \
    --cc=axboe@kernel.dk \
    --cc=bingjingc@synology.com \
    --cc=cccheng@synology.com \
    --cc=linux-block@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=neilb@suse.com \
    --cc=s3t@synology.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).