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[PATCH 4.9 53/78] btrfs: replace: Reset on-disk dev stats value after replace




4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Misono Tomohiro <misono.tomohiro@xxxxxxxxxxxxxx>

[ Upstream commit 1e7e1f9e3aba00c9b9c323bfeeddafe69ff21ff6 ]

on-disk devs stats value is updated in btrfs_run_dev_stats(),
which is called during commit transaction, if device->dev_stats_ccnt
is not zero.

Since current replace operation does not touch dev_stats_ccnt,
on-disk dev stats value is not updated. Therefore "btrfs device stats"
may return old device's value after umount/mount
(Example: See "btrfs ins dump-t -t DEV $DEV" after btrfs/100 finish).

Fix this by just incrementing dev_stats_ccnt in
btrfs_dev_replace_finishing() when replace is succeeded and this will
update the values.

Signed-off-by: Misono Tomohiro <misono.tomohiro@xxxxxxxxxxxxxx>
Reviewed-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 fs/btrfs/dev-replace.c |    6 ++++++
 1 file changed, 6 insertions(+)

--- a/fs/btrfs/dev-replace.c
+++ b/fs/btrfs/dev-replace.c
@@ -586,6 +586,12 @@ static int btrfs_dev_replace_finishing(s
 	btrfs_rm_dev_replace_unblocked(fs_info);
 
 	/*
+	 * Increment dev_stats_ccnt so that btrfs_run_dev_stats() will
+	 * update on-disk dev stats value during commit transaction
+	 */
+	atomic_inc(&tgt_device->dev_stats_ccnt);
+
+	/*
 	 * this is again a consistent state where no dev_replace procedure
 	 * is running, the target device is part of the filesystem, the
 	 * source device is not part of the filesystem anymore and its 1st