diff mbox series

[v3,3/3] dm: properly fix redundant bio-based IO accounting

Message ID 20220128041753.32195-4-snitzer@redhat.com (mailing list archive)
State New, archived
Headers show
Series block/dm: fix bio-based DM IO accounting | expand

Commit Message

Mike Snitzer Jan. 28, 2022, 4:17 a.m. UTC 
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: Bud Brown <bubrown@redhat.com>
Cc: stable@vger.kernel.org
Depends-on: f9893e1da2e3 ("block: add bio_start_io_acct_time() to control start_time")
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
---
 drivers/md/dm.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

Comments

Christoph Hellwig Jan. 28, 2022, 6:14 a.m. UTC | #1 
On Thu, Jan 27, 2022 at 11:17:53PM -0500, Mike Snitzer wrote:
> 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.

Looks good:

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

Patch

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 9849114b3c08..144436301a57 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -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 = READ_ONCE(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));