linux-kernel - Re: [PATCH v6 6/8] x86/resctrl: Move default control group creation during mount

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Date:   Tue, 8 Aug 2023 11:22:02 -0500
From:   "Moger, Babu" <babu.moger@....com>
To:     Reinette Chatre <reinette.chatre@...el.com>, corbet@....net,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de
Cc:     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, 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 v6 6/8] x86/resctrl: Move default control group creation
 during mount

Hi Reinette,

On 8/4/23 15:42, Reinette Chatre wrote:
> Hi Babu,
> 
> On 7/19/2023 4:22 PM, Babu Moger wrote:
>> The resctrl default control group is created during kernel init time. If
>> the new files are to be added to the default group during the mount based
>> on the mount option, then each file needs to be created separately and
>> call kernfs_activate.
>>
>> This can avoided if all the files are created during the mount and
>> destroyed during the umount. Move the root and default group creation
>> in rdt_get_tree and removal in rdt_kill_sb.
> 
> Please use () to indicate function names.

Sure.

> 
>>
>> Suggested-by: Reinette Chatre <reinette.chatre@...el.com>
>> Signed-off-by: Babu Moger <babu.moger@....com>
>> ---
> 
> ...
> 
>> @@ -3704,10 +3720,8 @@ static struct kernfs_syscall_ops rdtgroup_kf_syscall_ops = {
>>  	.show_options	= rdtgroup_show_options,
>>  };
>>  
>> -static int __init rdtgroup_setup_root(void)
>> +int rdtgroup_setup_root(void)
>>  {
>> -	int ret;
>> -
>>  	rdt_root = kernfs_create_root(&rdtgroup_kf_syscall_ops,
>>  				      KERNFS_ROOT_CREATE_DEACTIVATED |
>>  				      KERNFS_ROOT_EXTRA_OPEN_PERM_CHECK,
>> @@ -3715,28 +3729,17 @@ static int __init rdtgroup_setup_root(void)
>>  	if (IS_ERR(rdt_root))
>>  		return PTR_ERR(rdt_root);
>>  
>> -	mutex_lock(&rdtgroup_mutex);
>> -
>>  	rdtgroup_default.closid = 0;
>>  	rdtgroup_default.mon.rmid = 0;
>>  	rdtgroup_default.type = RDTCTRL_GROUP;
>> +	rdtgroup_default.mode = RDT_MODE_SHAREABLE;
>>  	INIT_LIST_HEAD(&rdtgroup_default.mon.crdtgrp_list);
>>  
>>  	list_add(&rdtgroup_default.rdtgroup_list, &rdt_all_groups);
>>  
>> -	ret = rdtgroup_add_files(kernfs_root_to_node(rdt_root), RFTYPE_CTRL_BASE);
>> -	if (ret) {
>> -		kernfs_destroy_root(rdt_root);
>> -		goto out;
>> -	}
>> -
>>  	rdtgroup_default.kn = kernfs_root_to_node(rdt_root);
>> -	kernfs_activate(rdtgroup_default.kn);
>>  
>> -out:
>> -	mutex_unlock(&rdtgroup_mutex);
>> -
>> -	return ret;
>> +	return 0;
>>  }
> 
> I am missing something here. Why is it now needed to re-initialize
> and add default resource group on every mount of resctrl? I expected
> only the kernfs related changes to move.

Yes. We can do that. I think I started with the previous version and went
that route. We dont have to change the default group initialization.
Will send new version soon.
Thanks
Babu Moger