linux-kernel - [PATCH v2] block: fix trace completion for chained bio

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Date:   Wed,  3 Mar 2021 11:22:06 +0800
From:   edwardh <edwardh@...ology.com>
To:     axboe@...nel.dk, neilb@...e.com
Cc:     linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        s3t@...ology.com, bingjingc@...ology.com, cccheng@...ology.com,
        Edward Hsieh <edwardh@...ology.com>
Subject: [PATCH v2] block: fix trace completion for chained bio

From: Edward Hsieh <edwardh@...ology.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@...ology.com>
Reviewed-by: BingJing Chang <bingjingc@...ology.com>
Signed-off-by: Edward Hsieh <edwardh@...ology.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