Commit b879f915 authored by Mike Snitzer's avatar Mike Snitzer Committed by Jens Axboe
Browse files

dm: properly fix redundant bio-based IO accounting 



Record the start_time for a bio but defer the starting block core's IO
accounting until after IO is submitted using bio_start_io_acct_time().

This approach avoids the need to mess around with any of the
individual IO stats in response to a bio_split() that follows bio
submission.

Reported-by: default avatarBud Brown <bubrown@redhat.com>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Cc: stable@vger.kernel.org
Depends-on: e45c47d1 ("block: add bio_start_io_acct_time() to control start_time")
Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
Link: https://lore.kernel.org/r/20220128155841.39644-4-snitzer@redhat.com


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent f524d9c9

drivers/md/dm.c

+3 −2
Original line number Diff line number Diff line
@@ -489,7 +489,7 @@ static void start_io_acct(struct dm_io *io) 
	struct mapped_device *md = io->md;

	struct bio *bio = io->orig_bio;



	io->start_time = bio_start_io_acct(bio);

	bio_start_io_acct_time(bio, io->start_time);

	if (unlikely(dm_stats_used(&md->stats)))

		dm_stats_account_io(&md->stats, bio_data_dir(bio),

				    bio->bi_iter.bi_sector, bio_sectors(bio),
@@ -535,7 +535,7 @@ static struct dm_io *alloc_io(struct mapped_device *md, struct bio *bio) 
	io->md = md;

	spin_lock_init(&io->endio_lock);



	start_io_acct(io);

	io->start_time = jiffies;



	return io;

}
@@ -1482,6 +1482,7 @@ static void __split_and_process_bio(struct mapped_device *md, 
			submit_bio_noacct(bio);

		}

	}

	start_io_acct(ci.io);



	/* drop the extra reference count */

	dm_io_dec_pending(ci.io, errno_to_blk_status(error));