From: Edward Hsieh edwardh@synology.com
[ Upstream commit 60b6a7e6a0f4382cd689f9afdac816964fec2921 ]
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 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 Signed-off-by: Sasha Levin sashal@kernel.org --- 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 @@ 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);