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>
---
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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