On Fri, Feb 11 2022 at 10:03P -0500,
Mikulas Patocka <mpatocka@xxxxxxxxxx> wrote:
> If a bio was split to multiple targets, only one target's sub-range was
> counted. This patch changes it so that all the targets' ranges are
> counted.
>
> Note that calls to bio_start_io_acct_remapped and bio_end_io_acct must
> match, so we maintain a counter how many times we have called
> bio_start_io_acct_remapped. When the io finishes, we call end_io_acct
> repeatedly.
>
> Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
Sorry but I'm not understanding, because any split that is needed due
to target boundaries will occur and the remainder (destined for other
targets) gets recursively submit_bio_noacct()'d back to the DM device.
So why do you think this wasn't happening properly?
Mike
>
> ---
> drivers/md/dm-core.h | 2 +-
> drivers/md/dm.c | 39 ++++++++++++++++++++-------------------
> 2 files changed, 21 insertions(+), 20 deletions(-)
>
> Index: linux-dm/drivers/md/dm-core.h
> ===================================================================
> --- linux-dm.orig/drivers/md/dm-core.h 2022-02-11 15:44:33.000000000 +0100
> +++ linux-dm/drivers/md/dm-core.h 2022-02-11 15:44:33.000000000 +0100
> @@ -230,7 +230,7 @@ struct dm_io {
> atomic_t io_count;
> struct bio *orig_bio;
> unsigned long start_time;
> - int was_accounted;
> + atomic_t n_accounted;
> spinlock_t lock;
> struct dm_stats_aux stats_aux;
> /* last member of dm_target_io is 'struct bio' */
> Index: linux-dm/drivers/md/dm.c
> ===================================================================
> --- linux-dm.orig/drivers/md/dm.c 2022-02-11 15:44:33.000000000 +0100
> +++ linux-dm/drivers/md/dm.c 2022-02-11 15:52:04.000000000 +0100
> @@ -487,27 +487,30 @@ EXPORT_SYMBOL_GPL(dm_start_time_ns_from_
>
> static void start_io_acct(struct dm_io *io, struct bio *bio)
> {
> - struct bio *orig_bio;
> -
> - /* Ensure IO accounting is only ever started once */
> - if (xchg(&io->was_accounted, 1) == 1)
> - return;
> -
> - orig_bio = io->orig_bio;
> + struct bio *orig_bio = io->orig_bio;
>
> bio_start_io_acct_remapped(bio, io->start_time,
> orig_bio->bi_bdev);
>
> - if (unlikely(dm_stats_used(&io->md->stats)))
> + if (unlikely(dm_stats_used(&io->md->stats))) {
> + if (unlikely(atomic_inc_return(&io->n_accounted) != 1))
> + return;
> dm_stats_account_io(&io->md->stats, bio_data_dir(orig_bio),
> orig_bio->bi_iter.bi_sector, bio_sectors(orig_bio),
> false, 0, &io->stats_aux);
> + } else {
> + atomic_inc(&io->n_accounted);
> + }
> }
>
> -static void end_io_acct(struct mapped_device *md, struct bio *bio,
> +static void end_io_acct(struct mapped_device *md, unsigned n_accounted, struct bio *bio,
> unsigned long start_time, struct dm_stats_aux *stats_aux)
> {
> - bio_end_io_acct(bio, start_time);
> + if (unlikely(!n_accounted))
> + return;
> + do {
> + bio_end_io_acct(bio, start_time);
> + } while (unlikely(--n_accounted));
>
> if (unlikely(dm_stats_used(&md->stats)))
> dm_stats_account_io(&md->stats, bio_data_dir(bio),
> @@ -536,7 +539,7 @@ static struct dm_io *alloc_io(struct map
> spin_lock_init(&io->lock);
>
> io->start_time = jiffies;
> - io->was_accounted = 0;
> + io->n_accounted = (atomic_t)ATOMIC_INIT(0);
>
> return io;
> }
> @@ -793,7 +796,7 @@ void dm_io_dec_pending(struct dm_io *io,
> blk_status_t io_error;
> struct bio *bio;
> struct mapped_device *md = io->md;
> - bool was_accounted = false;
> + int n_accounted;
> unsigned long start_time = 0;
> struct dm_stats_aux stats_aux;
>
> @@ -827,14 +830,12 @@ void dm_io_dec_pending(struct dm_io *io,
> }
>
> io_error = io->status;
> - if (io->was_accounted) {
> - was_accounted = true;
> - start_time = io->start_time;
> - stats_aux = io->stats_aux;
> - }
> + n_accounted = atomic_read(&io->n_accounted);
> + start_time = io->start_time;
> + stats_aux = io->stats_aux;
> +
> free_io(io);
> - if (was_accounted)
> - end_io_acct(md, bio, start_time, &stats_aux);
> + end_io_acct(md, n_accounted, bio, start_time, &stats_aux);
>
> /* nudge anyone waiting on suspend queue */
> if (unlikely(wq_has_sleeper(&md->wait)))
>
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