linux-kernel - Re: [PATCH] blk-throttle: Fix incorrect display of io.max

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Message-ID: <0de07021-df77-4196-bb75-9ded88b74ce2@redhat.com>
Date: Thu, 30 May 2024 09:49:43 -0400
From: Waiman Long <longman@...hat.com>
To: Jens Axboe <axboe@...nel.dk>, Tejun Heo <tj@...nel.org>,
 Josef Bacik <josef@...icpanda.com>
Cc: cgroups@...r.kernel.org, linux-block@...r.kernel.org,
 linux-kernel@...r.kernel.org, Dan Schatzberg <schatzberg.dan@...il.com>,
 Ming Lei <ming.lei@...hat.com>, Justin Forbes <jforbes@...hat.com>,
 Yu Kuai <yukuai3@...wei.com>
Subject: Re: [PATCH] blk-throttle: Fix incorrect display of io.max


On 5/30/24 09:45, Waiman Long wrote:
> Commit bf20ab538c81 ("blk-throttle: remove CONFIG_BLK_DEV_THROTTLING_LOW")
> attempts to revert the code change introduced by commit cd5ab1b0fcb4
> ("blk-throttle: add .low interface").  However, it leaves behind the
> bps_conf[] and iops_conf[] fields in the throtl_grp structure which
> aren't set anywhere in the new blk-throttle.c code but are still being
> used by tg_prfill_limit() to display the limits in io.max. Now io.max
> always displays the following values if a block queue is used:
>
> 	<m>:<n> rbps=0 wbps=0 riops=0 wiops=0
>
> Fix this problem by removing bps_conf[] and iops_conf[] and use bps[]
> and iops[] instead to complete the revert.
>
> Fixes: bf20ab538c81 ("blk-throttle: remove CONFIG_BLK_DEV_THROTTLING_LOW")
> Reported-by: Justin Forbes <jforbes@...hat.com>
> Closes: https://github.com/containers/podman/issues/22701#issuecomment-2120627789
> Signed-off-by: Waiman Long <longman@...hat.com>
> ---
>   block/blk-throttle.c | 24 ++++++++++++------------
>   block/blk-throttle.h |  8 ++------
>   2 files changed, 14 insertions(+), 18 deletions(-)
>
> diff --git a/block/blk-throttle.c b/block/blk-throttle.c
> index d907040859f9..da619654f418 100644
> --- a/block/blk-throttle.c
> +++ b/block/blk-throttle.c
> @@ -1347,32 +1347,32 @@ static u64 tg_prfill_limit(struct seq_file *sf, struct blkg_policy_data *pd,
>   	bps_dft = U64_MAX;
>   	iops_dft = UINT_MAX;
>   
> -	if (tg->bps_conf[READ] == bps_dft &&
> -	    tg->bps_conf[WRITE] == bps_dft &&
> -	    tg->iops_conf[READ] == iops_dft &&
> -	    tg->iops_conf[WRITE] == iops_dft)
> +	if (tg->bps[READ] == bps_dft &&
> +	    tg->bps[WRITE] == bps_dft &&
> +	    tg->iops[READ] == iops_dft &&
> +	    tg->iops[WRITE] == iops_dft)
>   		return 0;
>   
>   	seq_printf(sf, "%s", dname);
> -	if (tg->bps_conf[READ] == U64_MAX)
> +	if (tg->bps[READ] == U64_MAX)
>   		seq_printf(sf, " rbps=max");
>   	else
> -		seq_printf(sf, " rbps=%llu", tg->bps_conf[READ]);
> +		seq_printf(sf, " rbps=%llu", tg->bps[READ]);
>   
> -	if (tg->bps_conf[WRITE] == U64_MAX)
> +	if (tg->bps[WRITE] == U64_MAX)
>   		seq_printf(sf, " wbps=max");
>   	else
> -		seq_printf(sf, " wbps=%llu", tg->bps_conf[WRITE]);
> +		seq_printf(sf, " wbps=%llu", tg->bps[WRITE]);
>   
> -	if (tg->iops_conf[READ] == UINT_MAX)
> +	if (tg->iops[READ] == UINT_MAX)
>   		seq_printf(sf, " riops=max");
>   	else
> -		seq_printf(sf, " riops=%u", tg->iops_conf[READ]);
> +		seq_printf(sf, " riops=%u", tg->iops[READ]);
>   
> -	if (tg->iops_conf[WRITE] == UINT_MAX)
> +	if (tg->iops[WRITE] == UINT_MAX)
>   		seq_printf(sf, " wiops=max");
>   	else
> -		seq_printf(sf, " wiops=%u", tg->iops_conf[WRITE]);
> +		seq_printf(sf, " wiops=%u", tg->iops[WRITE]);
>   
>   	seq_printf(sf, "\n");
>   	return 0;
> diff --git a/block/blk-throttle.h b/block/blk-throttle.h
> index 32503fd83a84..8c365541a275 100644
> --- a/block/blk-throttle.h
> +++ b/block/blk-throttle.h
> @@ -95,15 +95,11 @@ struct throtl_grp {
>   	bool has_rules_bps[2];
>   	bool has_rules_iops[2];
>   
> -	/* internally used bytes per second rate limits */
> +	/* bytes per second rate limits */
>   	uint64_t bps[2];
> -	/* user configured bps limits */
> -	uint64_t bps_conf[2];
>   
> -	/* internally used IOPS limits */
> +	/* IOPS limits */
>   	unsigned int iops[2];
> -	/* user configured IOPS limits */
> -	unsigned int iops_conf[2];
>   
>   	/* Number of bytes dispatched in current slice */
>   	uint64_t bytes_disp[2];

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