Re: [PATCH 01/17] mm: don't include <linux/blk-cgroup.h> in <linux/writeback.h>

[Bart Van Assche <bvanassche@xxxxxxx>]

On 9/20/21 5:33 AM, Christoph Hellwig wrote:
> -static inline struct cgroup_subsys_state *
> -wbc_blkcg_css(struct writeback_control *wbc)
> -{
>   #ifdef CONFIG_CGROUP_WRITEBACK
> -	if (wbc->wb)
> -		return wbc->wb->blkcg_css;
> -#endif
> -	return blkcg_root_css;
> -}
> +#define wbc_blkcg_css(wbc) \
> +	((wbc)->wb ? (wbc)->wb->blkcg_css : blkcg_root_css)
> +#else
> +#define wbc_blkcg_css(wbc)		(blkcg_root_css)
> +#endif /* CONFIG_CGROUP_WRITEBACK */

This change may introduce annoying set-but-not-used warnings
with CONFIG_CGROUP_WRITEBACK=n. How about changing (blkcg_root_css)
into ((wbc), blkcg_root_css) to prevent this?

Thanks,

Bart.