linux-kernel - Re: [PATCH 1/4] sched/fair: free allocated memory on error in alloc_fair_sched

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Message-ID: <ZLasCKO4KA5Pgvdd@chenyu5-mobl2>
Date:   Tue, 18 Jul 2023 23:13:12 +0800
From:   Chen Yu <yu.c.chen@...el.com>
To:     Aaron Lu <aaron.lu@...el.com>
CC:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Daniel Jordan <daniel.m.jordan@...cle.com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        "Valentin Schneider" <vschneid@...hat.com>,
        Tim Chen <tim.c.chen@...el.com>,
        "Nitin Tekchandani" <nitin.tekchandani@...el.com>,
        Waiman Long <longman@...hat.com>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/4] sched/fair: free allocated memory on error in
 alloc_fair_sched_group()

On 2023-07-18 at 21:41:17 +0800, Aaron Lu wrote:
> There is one struct cfs_rq and one struct se on each cpu for a taskgroup
> and when allocation for tg->cfs_rq[X] failed, the already allocated
> tg->cfs_rq[0]..tg->cfs_rq[X-1] should be freed. The same for tg->se.
> 
> Signed-off-by: Aaron Lu <aaron.lu@...el.com>
> ---
>  kernel/sched/fair.c | 23 ++++++++++++++++-------
>  1 file changed, 16 insertions(+), 7 deletions(-)
> 
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index a80a73909dc2..0f913487928d 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -12443,10 +12443,10 @@ int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
>  
>  	tg->cfs_rq = kcalloc(nr_cpu_ids, sizeof(cfs_rq), GFP_KERNEL);
>  	if (!tg->cfs_rq)
> -		goto err;
> +		return 0;
>  	tg->se = kcalloc(nr_cpu_ids, sizeof(se), GFP_KERNEL);
>  	if (!tg->se)
> -		goto err;
> +		goto err_free_rq_pointer;
>  
>  	tg->shares = NICE_0_LOAD;
>  
> @@ -12456,12 +12456,12 @@ int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
>  		cfs_rq = kzalloc_node(sizeof(struct cfs_rq),
>  				      GFP_KERNEL, cpu_to_node(i));
>  		if (!cfs_rq)
> -			goto err;
> +			goto err_free;
>  
>  		se = kzalloc_node(sizeof(struct sched_entity_stats),
>  				  GFP_KERNEL, cpu_to_node(i));
>  		if (!se)
> -			goto err_free_rq;
> +			goto err_free;
>  
>  		init_cfs_rq(cfs_rq);
>  		init_tg_cfs_entry(tg, cfs_rq, se, i, parent->se[i]);
> @@ -12470,9 +12470,18 @@ int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
>  
>  	return 1;
>  
> -err_free_rq:
> -	kfree(cfs_rq);
> -err:
> +err_free:
> +	for_each_possible_cpu(i) {
> +		kfree(tg->cfs_rq[i]);
> +		kfree(tg->se[i]);
> +
> +		if (!tg->cfs_rq[i] && !tg->se[i])
> +			break;
> +	}
> +	kfree(tg->se);
> +err_free_rq_pointer:
> +	kfree(tg->cfs_rq);
> +
Not sure if I overlooked, if alloc_fair_sched_group() fails in sched_create_group(),
would sched_free_group()->free_fair_sched_group() do the cleanup?

thanks,
Chenyu