linux-kernel - Re: [PATCH 5/6] bfq-iosched: move bfq_stat_recursive

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Date:   Fri, 7 Jun 2019 08:07:48 +0200
From:   Paolo Valente <paolo.valente@...aro.org>
To:     Christoph Hellwig <hch@....de>
Cc:     Jens Axboe <axboe@...nel.dk>, linux-block@...r.kernel.org,
        cgroups@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/6] bfq-iosched: move bfq_stat_recursive_sum into the
 only caller



> Il giorno 6 giu 2019, alle ore 12:26, Christoph Hellwig <hch@....de> ha scritto:
> 
> This function was moved from core block code and is way to generic.
> Fold it into the only caller and simplify it based on the actually
> passed arguments.
> 

Acked-by: Paolo Valente <paolo.valente@...aro.org>

> Signed-off-by: Christoph Hellwig <hch@....de>
> ---
> block/bfq-cgroup.c | 62 ++++++++++++++--------------------------------
> 1 file changed, 19 insertions(+), 43 deletions(-)
> 
> diff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c
> index a691dca7e966..d84302445e30 100644
> --- a/block/bfq-cgroup.c
> +++ b/block/bfq-cgroup.c
> @@ -80,47 +80,6 @@ static inline void bfq_stat_add_aux(struct bfq_stat *to,
> 		     &to->aux_cnt);
> }
> 
> -/**
> - * bfq_stat_recursive_sum - collect hierarchical bfq_stat
> - * @blkg: blkg of interest
> - * @pol: blkcg_policy which contains the bfq_stat
> - * @off: offset to the bfq_stat in blkg_policy_data or @blkg
> - *
> - * Collect the bfq_stat specified by @blkg, @pol and @off and all its
> - * online descendants and their aux counts.  The caller must be holding the
> - * queue lock for online tests.
> - *
> - * If @pol is NULL, bfq_stat is at @off bytes into @blkg; otherwise, it is
> - * at @off bytes into @blkg's blkg_policy_data of the policy.
> - */
> -static u64 bfq_stat_recursive_sum(struct blkcg_gq *blkg,
> -			    struct blkcg_policy *pol, int off)
> -{
> -	struct blkcg_gq *pos_blkg;
> -	struct cgroup_subsys_state *pos_css;
> -	u64 sum = 0;
> -
> -	lockdep_assert_held(&blkg->q->queue_lock);
> -
> -	rcu_read_lock();
> -	blkg_for_each_descendant_pre(pos_blkg, pos_css, blkg) {
> -		struct bfq_stat *stat;
> -
> -		if (!pos_blkg->online)
> -			continue;
> -
> -		if (pol)
> -			stat = (void *)blkg_to_pd(pos_blkg, pol) + off;
> -		else
> -			stat = (void *)blkg + off;
> -
> -		sum += bfq_stat_read(stat) + atomic64_read(&stat->aux_cnt);
> -	}
> -	rcu_read_unlock();
> -
> -	return sum;
> -}
> -
> /**
>  * blkg_prfill_stat - prfill callback for bfq_stat
>  * @sf: seq_file to print to
> @@ -1045,8 +1004,25 @@ static int bfqg_print_rwstat(struct seq_file *sf, void *v)
> static u64 bfqg_prfill_stat_recursive(struct seq_file *sf,
> 				      struct blkg_policy_data *pd, int off)
> {
> -	u64 sum = bfq_stat_recursive_sum(pd_to_blkg(pd),
> -					  &blkcg_policy_bfq, off);
> +	struct blkcg_gq *blkg = pd_to_blkg(pd);
> +	struct blkcg_gq *pos_blkg;
> +	struct cgroup_subsys_state *pos_css;
> +	u64 sum = 0;
> +
> +	lockdep_assert_held(&blkg->q->queue_lock);
> +
> +	rcu_read_lock();
> +	blkg_for_each_descendant_pre(pos_blkg, pos_css, blkg) {
> +		struct bfq_stat *stat;
> +
> +		if (!pos_blkg->online)
> +			continue;
> +
> +		stat = (void *)blkg_to_pd(pos_blkg, &blkcg_policy_bfq) + off;
> +		sum += bfq_stat_read(stat) + atomic64_read(&stat->aux_cnt);
> +	}
> +	rcu_read_unlock();
> +
> 	return __blkg_prfill_u64(sf, pd, sum);
> }
> 
> --
> 2.20.1
> 


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