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FAILED: patch "[PATCH] dm: properly fix redundant bio-based IO accounting" failed to apply to 5.10-stable tree

PATCH [email protected] 1 participant 1 message Jan 29, 2022

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Stable branch Device mapper
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The patch below does not apply to the 5.10-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From b879f915bc48a18d4f4462729192435bb0f17052 Mon Sep 17 00:00:00 2001
From: Mike Snitzer <[email protected]>
Date: Fri, 28 Jan 2022 10:58:41 -0500
Subject: [PATCH] dm: properly fix redundant bio-based IO accounting

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 <[email protected]>
Reviewed-by Christoph Hellwig <[email protected]>
Cc [email protected]

Depends-on: e45c47d1f94e ("block: add bio_start_io_acct_time() to control start_time")

Signed-off-by Mike Snitzer <[email protected]>
Link https://lore.kernel.org/r/[email protected] open here
Signed-off-by Jens Axboe <[email protected]>
drivers/md/dm.c +3 -2
index 9849114b3c08..dcbd6d201619 100644
@@ -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_time(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),

@@ -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 = 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));