linux-kernel - Re: [PATCH v10 05/10] x86/resctrl: Unwind the errors inside rdt_enable

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Date:   Fri, 29 Sep 2023 18:22:26 +0300 (EEST)
From:   Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To:     Babu Moger <babu.moger@....com>
cc:     corbet@....net, Reinette Chatre <reinette.chatre@...el.com>,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        fenghua.yu@...el.com, dave.hansen@...ux.intel.com, x86@...nel.org,
        hpa@...or.com, paulmck@...nel.org, akpm@...ux-foundation.org,
        quic_neeraju@...cinc.com, rdunlap@...radead.org,
        damien.lemoal@...nsource.wdc.com, songmuchun@...edance.com,
        peterz@...radead.org, jpoimboe@...nel.org, pbonzini@...hat.com,
        chang.seok.bae@...el.com, pawan.kumar.gupta@...ux.intel.com,
        jmattson@...gle.com, daniel.sneddon@...ux.intel.com,
        sandipan.das@....com, tony.luck@...el.com, james.morse@....com,
        linux-doc@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        bagasdotme@...il.com, eranian@...gle.com,
        christophe.leroy@...roup.eu, jarkko@...nel.org,
        adrian.hunter@...el.com, quic_jiles@...cinc.com,
        peternewman@...gle.com
Subject: Re: [PATCH v10 05/10] x86/resctrl: Unwind the errors inside
 rdt_enable_ctx()

On Fri, 15 Sep 2023, Babu Moger wrote:

> rdt_enable_ctx() enables the features provided during resctrl mount.
> 
> Additions to rdt_enable_ctx() are required to also modify error paths
> of rdt_enable_ctx() callers to ensure correct unwinding if errors
> are encountered after calling rdt_enable_ctx(). This is error prone.
> 
> Introduce rdt_disable_ctx() to refactor the error unwinding of
> rdt_enable_ctx() to simplify future additions. This also simplifies
> cleanup in rdt_kill_sb().
> 
> Remove cdp_disable_all() as it is not used anymore after the refactor.
> 
> Suggested-by: Reinette Chatre <reinette.chatre@...el.com>
> Reviewed-by: Fenghua Yu <fenghua.yu@...el.com>
> Reviewed-by: Reinette Chatre <reinette.chatre@...el.com>
> Signed-off-by: Babu Moger <babu.moger@....com>
> ---
>  arch/x86/kernel/cpu/resctrl/rdtgroup.c | 53 ++++++++++++++++----------
>  1 file changed, 32 insertions(+), 21 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> index 35945b4bf196..3ea874c80c22 100644
> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> @@ -2290,14 +2290,6 @@ int resctrl_arch_set_cdp_enabled(enum resctrl_res_level l, bool enable)
>  	return 0;
>  }
>  
> -static void cdp_disable_all(void)
> -{
> -	if (resctrl_arch_get_cdp_enabled(RDT_RESOURCE_L3))
> -		resctrl_arch_set_cdp_enabled(RDT_RESOURCE_L3, false);
> -	if (resctrl_arch_get_cdp_enabled(RDT_RESOURCE_L2))
> -		resctrl_arch_set_cdp_enabled(RDT_RESOURCE_L2, false);
> -}
> -
>  /*
>   * We don't allow rdtgroup directories to be created anywhere
>   * except the root directory. Thus when looking for the rdtgroup
> @@ -2377,19 +2369,42 @@ static int mkdir_mondata_all(struct kernfs_node *parent_kn,
>  			     struct rdtgroup *prgrp,
>  			     struct kernfs_node **mon_data_kn);
>  
> +static void rdt_disable_ctx(void)
> +{
> +	resctrl_arch_set_cdp_enabled(RDT_RESOURCE_L3, false);
> +	resctrl_arch_set_cdp_enabled(RDT_RESOURCE_L2, false);
> +	set_mba_sc(false);
> +}
> +
>  static int rdt_enable_ctx(struct rdt_fs_context *ctx)
>  {
>  	int ret = 0;
>  
> -	if (ctx->enable_cdpl2)
> +	if (ctx->enable_cdpl2) {
>  		ret = resctrl_arch_set_cdp_enabled(RDT_RESOURCE_L2, true);
> +		if (ret)
> +			goto out_done;
> +	}
>  
> -	if (!ret && ctx->enable_cdpl3)
> +	if (ctx->enable_cdpl3) {
>  		ret = resctrl_arch_set_cdp_enabled(RDT_RESOURCE_L3, true);
> +		if (ret)
> +			goto out_cdpl2;
> +	}
>  
> -	if (!ret && ctx->enable_mba_mbps)
> +	if (ctx->enable_mba_mbps) {
>  		ret = set_mba_sc(true);
> +		if (ret)
> +			goto out_cdpl3;
> +	}
> +
> +	return 0;
>  
> +out_cdpl3:
> +	resctrl_arch_set_cdp_enabled(RDT_RESOURCE_L3, false);
> +out_cdpl2:
> +	resctrl_arch_set_cdp_enabled(RDT_RESOURCE_L2, false);
> +out_done:
>  	return ret;
>  }
>  
> @@ -2497,13 +2512,13 @@ static int rdt_get_tree(struct fs_context *fc)
>  	}
>  
>  	ret = rdt_enable_ctx(ctx);
> -	if (ret < 0)
> -		goto out_cdp;
> +	if (ret)
> +		goto out;
>  
>  	ret = schemata_list_create();
>  	if (ret) {
>  		schemata_list_destroy();
> -		goto out_mba;
> +		goto out_ctx;
>  	}
>  
>  	closid_init();
> @@ -2562,11 +2577,8 @@ static int rdt_get_tree(struct fs_context *fc)
>  	kernfs_remove(kn_info);
>  out_schemata_free:
>  	schemata_list_destroy();
> -out_mba:
> -	if (ctx->enable_mba_mbps)
> -		set_mba_sc(false);
> -out_cdp:
> -	cdp_disable_all();
> +out_ctx:
> +	rdt_disable_ctx();
>  out:
>  	rdt_last_cmd_clear();
>  	mutex_unlock(&rdtgroup_mutex);
> @@ -2798,12 +2810,11 @@ static void rdt_kill_sb(struct super_block *sb)
>  	cpus_read_lock();
>  	mutex_lock(&rdtgroup_mutex);
>  
> -	set_mba_sc(false);
> +	rdt_disable_ctx();
>  
>  	/*Put everything back to default values. */
>  	for_each_alloc_capable_rdt_resource(r)
>  		reset_all_ctrls(r);
> -	cdp_disable_all();
>  	rmdir_all_sub();
>  	rdt_pseudo_lock_release();
>  	rdtgroup_default.mode = RDT_MODE_SHAREABLE;
> 

Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>

-- 
 i.