[dm-devel] [PATCH] dm: fix dm_stats accounting

[Mikulas Patocka]

Exactly the same sector number and length must be passed to both calls of
dm_stats_account_io, otherwise its per-zone in_flight counters go out of
sync. This patch fixes it.

Signed-off-by: Mikulas Patocka <mpatocka at redhat.com>

---
 drivers/md/dm.c |   10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

Index: linux-dm/drivers/md/dm.c
===================================================================
--- linux-dm.orig/drivers/md/dm.c	2022-02-11 15:32:56.000000000 +0100
+++ linux-dm/drivers/md/dm.c	2022-02-11 15:40:11.000000000 +0100
@@ -487,16 +487,20 @@ 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;
+
 	bio_start_io_acct_remapped(bio, io->start_time,
-				   io->orig_bio->bi_bdev);
+				   orig_bio->bi_bdev);
 
 	if (unlikely(dm_stats_used(&io->md->stats)))
-		dm_stats_account_io(&io->md->stats, bio_data_dir(bio),
-				    bio->bi_iter.bi_sector, bio_sectors(bio),
+		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);
 }