Hi Jens and Neil,
Is there any feedback on this patch?
Thank you,
Edward Hsieh
On 3/3/2021 11:22 AM, Edward Hsieh wrote:
From: Edward Hsieh <edwardh@xxxxxxxxxxxx>
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@xxxxxxxxxxxx>
Reviewed-by: BingJing Chang <bingjingc@xxxxxxxxxxxx>
Signed-off-by: Edward Hsieh <edwardh@xxxxxxxxxxxx>
---
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);
