On Thu, Jan 27 2022 at 5:56P -0500,
Mike Snitzer <snitzer@xxxxxxxxxx> 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.
>
> Reported-by: Bud Brown <bubrown@xxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> Depends-on: f9893e1da2e3 ("block: add bio_start_io_acct_time() to control start_time")
> Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
> ---
> drivers/md/dm.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> 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(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),
This should be calling bio_start_io_acct_time().
I updated the header but somehow dropped the code change before
sending.
Mike
> @@ -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));
> --
> 2.15.0
>
