linux-kernel - [PATCH 5.15 043/171] dm: revert partial fix for redundant bio-based IO accounting

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Date:   Mon, 31 Jan 2022 11:55:08 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Mike Snitzer <snitzer@...hat.com>,
        Jens Axboe <axboe@...nel.dk>
Subject: [PATCH 5.15 043/171] dm: revert partial fix for redundant bio-based IO accounting

From: Mike Snitzer <snitzer@...hat.com>

commit f524d9c95fab54783d0038f7a3e8c014d5b56857 upstream.

Reverts a1e1cb72d9649 ("dm: fix redundant IO accounting for bios that
need splitting") because it was too narrow in scope (only addressed
redundant 'sectors[]' accounting and not ios, nsecs[], etc).

Cc: stable@...r.kernel.org
Signed-off-by: Mike Snitzer <snitzer@...hat.com>
Link: https://lore.kernel.org/r/20220128155841.39644-3-snitzer@redhat.com
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/md/dm.c |   15 ---------------
 1 file changed, 15 deletions(-)

--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1514,9 +1514,6 @@ static void init_clone_info(struct clone
 	ci->sector = bio->bi_iter.bi_sector;
 }
 
-#define __dm_part_stat_sub(part, field, subnd)	\
-	(part_stat_get(part, field) -= (subnd))
-
 /*
  * Entry point to split a bio into clones and submit them to the targets.
  */
@@ -1553,18 +1550,6 @@ static blk_qc_t __split_and_process_bio(
 						  GFP_NOIO, &md->queue->bio_split);
 			ci.io->orig_bio = b;
 
-			/*
-			 * Adjust IO stats for each split, otherwise upon queue
-			 * reentry there will be redundant IO accounting.
-			 * NOTE: this is a stop-gap fix, a proper fix involves
-			 * significant refactoring of DM core's bio splitting
-			 * (by eliminating DM's splitting and just using bio_split)
-			 */
-			part_stat_lock();
-			__dm_part_stat_sub(dm_disk(md)->part0,
-					   sectors[op_stat_group(bio_op(bio))], ci.sector_count);
-			part_stat_unlock();
-
 			bio_chain(b, bio);
 			trace_block_split(b, bio->bi_iter.bi_sector);
 			ret = submit_bio_noacct(bio);