On Thu, Jun 24, 2021 at 08:30:30PM +0800, edwardh wrote:

From: Edward Hsieh <redacted>

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 <redacted>
Reviewed-by: BingJing Chang <redacted>
Signed-off-by: Edward Hsieh <redacted>

Looks good,

Reviewed-by: Christoph Hellwig <hch@lst.de>