[Devel] [PATCH v2 rh7 1/2] fs/writeback: per-CT fs writeback

[Vladimir Davydov]

On Tue, Jan 19, 2016 at 07:14:29PM +0300, Andrey Ryabinin wrote:
...
> @@ -1004,6 +1022,8 @@ static long wb_check_background_flush(struct bdi_writeback *wb)
>  			.for_background	= 1,
>  			.range_cyclic	= 1,
>  			.reason		= WB_REASON_BACKGROUND,
> +			.filter_ub	= 0,
> +			.ub		= NULL,

Please don't initialize struct fields to 0 - this is done automatically.
It increases churn and complicates rebases.

>  		};
>  
>  		return wb_writeback(wb, &work);
> @@ -1038,6 +1058,8 @@ static long wb_check_old_data_flush(struct bdi_writeback *wb)
...
> @@ -157,8 +193,10 @@ bool ub_should_skip_writeback(struct user_beancounter *ub, struct inode *inode)
>  
>  	rcu_read_lock();
>  	dirtied_ub = rcu_dereference(inode->i_mapping->dirtied_ub);
> -	ret = !dirtied_ub || (dirtied_ub != ub &&
> -			!test_bit(UB_DIRTY_EXCEEDED, &dirtied_ub->ub_flags));
> +	if (ub)
> +		ret = (ub != dirtied_ub);
> +	else
> +		ret = (dirtied_ub && !ub_over_bground_thresh());

No need to check all beancounters here.
__ub_over_bground_thresh(dirtied_ub) should be enough.

>  	rcu_read_unlock();
>  
>  	return ret;