Re: [PATCH 05/13] blkcg: associate blkg when associating a device

[Christoph Hellwig]

> diff --git a/include/linux/bio.h b/include/linux/bio.h
> index 62715a5a4f32..8bc9d9b29fd3 100644
> --- a/include/linux/bio.h
> +++ b/include/linux/bio.h
> @@ -486,6 +486,12 @@ extern unsigned int bvec_nr_vecs(unsigned short idx);
>  extern const char *bio_devname(struct bio *bio, char *buffer);
>  
>  #define bio_set_dev(bio, bdev) 			\
> +do {						\
> +	bio_set_dev_only(bio, bdev);		\
> +	bio_associate_blkg(bio);		\
> +} while (0)
> +
> +#define bio_set_dev_only(bio, bdev)		\

This lacks any explanation on when you would use bio_set_dev_only or
bio_set_dev.  Please document why we need both and why you'd choose or
the other.