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From:   SeongJae Park <sj@kernel.org>
To:     xiakaixu1987@gmail.com
Cc:     sj@kernel.org, akpm@linux-foundation.org, damon@lists.linux.dev,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        Kaixu Xia <kaixuxia@tencent.com>
Subject: Re: [PATCH] mm/damon/sysfs: simplify the judgement whether kdamonds are busy
Date:   Mon,  5 Sep 2022 18:20:17 +0000
Message-Id: <20220905182017.50625-1-sj@kernel.org>
In-Reply-To: <1662302166-13216-1-git-send-email-kaixuxia@tencent.com>
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Hi Kaixu,

On Sun, 4 Sep 2022 22:36:06 +0800 xiakaixu1987@gmail.com wrote:

> From: Kaixu Xia <kaixuxia@tencent.com>
> 
> It is unnecessary to get the number of the running kdamond to judge
> whether kdamonds are busy. Here we can use the
> damon_sysfs_kdamond_running() helper and return -EBUSY directly
> when finding a running kdamond. Meanwhile, merging with the judgement
> that a kdamond has current sysfs command callback request to make
> the code more clear.
> 
> Signed-off-by: Kaixu Xia <kaixuxia@tencent.com>

Reviewed-by: SeongJae Park <sj@kernel.org>


Thanks,
SJ

> ---
>  mm/damon/sysfs.c | 25 +++++++------------------
>  1 file changed, 7 insertions(+), 18 deletions(-)
> 
> diff --git a/mm/damon/sysfs.c b/mm/damon/sysfs.c
> index 7488e27c87c3..fe6c6870cf86 100644
> --- a/mm/damon/sysfs.c
> +++ b/mm/damon/sysfs.c
> @@ -2657,23 +2657,18 @@ static void damon_sysfs_kdamonds_rm_dirs(struct damon_sysfs_kdamonds *kdamonds)
>  	kdamonds->kdamonds_arr = NULL;
>  }
>  
> -static int damon_sysfs_nr_running_ctxs(struct damon_sysfs_kdamond **kdamonds,
> +static bool damon_sysfs_kdamonds_busy(struct damon_sysfs_kdamond **kdamonds,
>  		int nr_kdamonds)
>  {
> -	int nr_running_ctxs = 0;
>  	int i;
>  
>  	for (i = 0; i < nr_kdamonds; i++) {
> -		struct damon_ctx *ctx = kdamonds[i]->damon_ctx;
> -
> -		if (!ctx)
> -			continue;
> -		mutex_lock(&ctx->kdamond_lock);
> -		if (ctx->kdamond)
> -			nr_running_ctxs++;
> -		mutex_unlock(&ctx->kdamond_lock);
> +		if (damon_sysfs_kdamond_running(kdamonds[i]) ||
> +		    damon_sysfs_cmd_request.kdamond == kdamonds[i])
> +			return true;
>  	}
> -	return nr_running_ctxs;
> +
> +	return false;
>  }
>  
>  static int damon_sysfs_kdamonds_add_dirs(struct damon_sysfs_kdamonds *kdamonds,
> @@ -2682,15 +2677,9 @@ static int damon_sysfs_kdamonds_add_dirs(struct damon_sysfs_kdamonds *kdamonds,
>  	struct damon_sysfs_kdamond **kdamonds_arr, *kdamond;
>  	int err, i;
>  
> -	if (damon_sysfs_nr_running_ctxs(kdamonds->kdamonds_arr, kdamonds->nr))
> +	if (damon_sysfs_kdamonds_busy(kdamonds->kdamonds_arr, kdamonds->nr))
>  		return -EBUSY;
>  
> -	for (i = 0; i < kdamonds->nr; i++) {
> -		if (damon_sysfs_cmd_request.kdamond ==
> -				kdamonds->kdamonds_arr[i])
> -			return -EBUSY;
> -	}
> -
>  	damon_sysfs_kdamonds_rm_dirs(kdamonds);
>  	if (!nr_kdamonds)
>  		return 0;
> -- 
> 2.27.0
> 
>