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Btrfsctl was removed in 2012, now the function btrfs_control_ioctl()
is only used for devices ioctls. So update the comment.
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Su Yue <Damenly_Su@gmx.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>