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block: fix trace completion for chained bio

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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: fbbaf700e7 ("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>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20210624123030.27014-1-edwardh@synology.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Edward Hsieh 2021-06-24 20:30:30 +08:00 committed by Jens Axboe
parent ddcc5c544e
commit 60b6a7e6a0
1 changed files with 6 additions and 7 deletions
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13
block/bio.c
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@ -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 @@ again:
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 @@ again:
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);