diff mbox series

block: fix trace completion for chained bio

Message ID 1607406731-25553-1-git-send-email-edwardh@synology.com (mailing list archive)
State New, archived
Headers show
Series block: fix trace completion for chained bio | expand

Commit Message

edwardh Dec. 8, 2020, 5:52 a.m. UTC 
From: Edward Hsieh <edwardh@synology.com>

For chained bio, trace_block_bio_complete in bio_endio is called only by
the parent bio once upon all chained bio completed. However, the sector and
the size for the parent bio are modified in bio_split. Therefore,
the size of the complete events might not match the queue events.

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 mbox series

Patch

diff --git a/block/bio.c b/block/bio.c
index fa01bef3..d202d6b 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -1411,8 +1411,7 @@  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)
 {
@@ -1425,6 +1424,11 @@  void bio_endio(struct bio *bio)
 	if (bio->bi_disk)
 		rq_qos_done_bio(bio->bi_disk->queue, bio);
 
+	if (bio->bi_disk && bio_flagged(bio, BIO_TRACE_COMPLETION)) {
+		trace_block_bio_complete(bio->bi_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
@@ -1438,11 +1442,6 @@  void bio_endio(struct bio *bio)
 		goto again;
 	}
 
-	if (bio->bi_disk && bio_flagged(bio, BIO_TRACE_COMPLETION)) {
-		trace_block_bio_complete(bio->bi_disk->queue, bio);
-		bio_clear_flag(bio, BIO_TRACE_COMPLETION);
-	}
-
 	blk_throtl_bio_endio(bio);
 	/* release cgroup info */
 	bio_uninit(bio);