From: Edward Hsieh <[email protected]>
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.
The issue can be reproduced by md/raid5 read with bio cross chunks.
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 <[email protected]>
Reviewed-by: BingJing Chang <[email protected]>
Signed-off-by: Edward Hsieh <[email protected]>
---
block/bio.c | 13 ++++++-------
1 file changed, 6 insertions(+), 7 deletions(-)
diff --git a/block/bio.c b/block/bio.c
index 44205dfb6b60..1fab762e079b 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -1375,8 +1375,7 @@ 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)
{
@@ -1389,6 +1388,11 @@ 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
@@ -1402,11 +1406,6 @@ 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);
--
2.31.1
On Thu, Jun 24, 2021 at 08:30:30PM +0800, edwardh wrote:
> From: Edward Hsieh <[email protected]>
>
> 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.
>
> The issue can be reproduced by md/raid5 read with bio cross chunks.
>
> 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 <[email protected]>
> Reviewed-by: BingJing Chang <[email protected]>
> Signed-off-by: Edward Hsieh <[email protected]>
Looks good,
Reviewed-by: Christoph Hellwig <[email protected]>
On 6/24/21 6:30 AM, edwardh wrote:
> From: Edward Hsieh <[email protected]>
>
> 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.
>
> The issue can be reproduced by md/raid5 read with bio cross chunks.
>
> To fix, move trace completion into the loop for every chained bio to call.
Applied, thanks.
--
Jens Axboe