linux-kernel - Re: [PATCH] writeback: Simplify wb_stat

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Message-ID: <fdccef73-4a99-51be-ba4a-9c7583fb5b73@suse.com>
Date:   Mon, 26 Jun 2017 23:59:09 +0300
From:   Nikolay Borisov <nborisov@...e.com>
To:     tj@...nel.org
Cc:     jack@...e.cz, axboe@...com, linux-kernel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] writeback: Simplify wb_stat_sum

[CC'ing Andrew since he seems to be taking those patches through -mm ]

On 23.06.2017 18:11, Nikolay Borisov wrote:
> wb_stat_sum disables interrupts and calls __wb_stat_sum which eventually calls
> __percpu_counter_sum. However, the percpu routine is already irq-safe. Simplify
> the code a bit by making wb_stat_sum directly call percpu_counter_sum_positive
> and not disable interrupts. Also remove the now-uneeded __wb_stat_sum which was
> just a wrapper over percpu_counter_sum_positive
> 
> Signed-off-by: Nikolay Borisov <nborisov@...e.com>
> ---
>  include/linux/backing-dev.h | 15 +--------------
>  1 file changed, 1 insertion(+), 14 deletions(-)
> 
> diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
> index e9c967b86054..854e1bdd0b2a 100644
> --- a/include/linux/backing-dev.h
> +++ b/include/linux/backing-dev.h
> @@ -84,22 +84,9 @@ static inline s64 wb_stat(struct bdi_writeback *wb, enum wb_stat_item item)
>  	return percpu_counter_read_positive(&wb->stat[item]);
>  }
>  
> -static inline s64 __wb_stat_sum(struct bdi_writeback *wb,
> -				enum wb_stat_item item)
> -{
> -	return percpu_counter_sum_positive(&wb->stat[item]);
> -}
> -
>  static inline s64 wb_stat_sum(struct bdi_writeback *wb, enum wb_stat_item item)
>  {
> -	s64 sum;
> -	unsigned long flags;
> -
> -	local_irq_save(flags);
> -	sum = __wb_stat_sum(wb, item);
> -	local_irq_restore(flags);
> -
> -	return sum;
> +	return percpu_counter_sum_positive(&wb->stat[item]);
>  }
>  
>  extern void wb_writeout_inc(struct bdi_writeback *wb);
>