linux-kernel - Re: [PATCH v7 6/8] x86/resctrl: Move default control group creation during mount

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Message-ID: <b9eed930-1a8d-7cf7-0515-1f9d33089953@amd.com>
Date:   Wed, 16 Aug 2023 14:14:14 -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 v7 6/8] x86/resctrl: Move default control group creation
 during mount

Hi Reinette,

On 8/15/23 17:50, Reinette Chatre wrote:
> Hi Babu,
> 
> Please do note that the subject is no longer accurate.

Changing to

x86/resctrl: Move default group file creation during mount

> 
> On 8/11/2023 1:10 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 based on the mount
>> option, then each file needs to be created separately and call
>> kernfs_activate() again.
>>
>> This can be avoided if all the files are created during the mount and
>> destroyed during the umount. So, move the default group creation
>> in rdt_get_tree() and removal in rdt_kill_sb().
> 
> How about a slight rewording (please feel free to change):
> 
>   The default resource group and its files are created during kernel
>   init time. Upcoming changes will make some resctrl files optional
>   based on a mount parameter. If optional files are to be added to the
>   default group based on the mount option, then each new file needs to
>   be created separately and call kernfs_activate() again.
> 
>   Create all files of the default resource group during resctrl
>   mount, destroyed during unmount, to avoid scattering resctrl
>   file addition across two separate code flows.

Sure. Looks good. thanks

> 
> 
>>
>> Suggested-by: Reinette Chatre <reinette.chatre@...el.com>
>> Signed-off-by: Babu Moger <babu.moger@....com>
>> ---
>>  arch/x86/kernel/cpu/resctrl/internal.h |    1 +
>>  arch/x86/kernel/cpu/resctrl/rdtgroup.c |   50 +++++++++++++++++---------------
>>  2 files changed, 27 insertions(+), 24 deletions(-)
>>
>> diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
>> index 37800724e002..2bd92c0c3b0c 100644
>> --- a/arch/x86/kernel/cpu/resctrl/internal.h
>> +++ b/arch/x86/kernel/cpu/resctrl/internal.h
>> @@ -602,5 +602,6 @@ void rdt_domain_reconfigure_cdp(struct rdt_resource *r);
>>  void __init thread_throttle_mode_init(void);
>>  void __init mbm_config_rftype_init(const char *config);
>>  void rdt_staged_configs_clear(void);
>> +int rdtgroup_setup_root(struct rdt_fs_context *ctx);
>>  
>>  #endif /* _ASM_X86_RESCTRL_INTERNAL_H */
>> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> index 0805fac04401..a7453c93bad4 100644
>> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> @@ -2521,10 +2521,14 @@ static int rdt_get_tree(struct fs_context *fc)
>>  		goto out;
>>  	}
>>  
>> -	ret = rdt_enable_ctx(ctx);
>> +	ret = rdtgroup_setup_root(ctx);
>>  	if (ret)
>>  		goto out;
>>  
>> +	ret = rdt_enable_ctx(ctx);
>> +	if (ret)
>> +		goto out_root;
>> +
>>  	ret = schemata_list_create();
>>  	if (ret) {
>>  		schemata_list_destroy();
>> @@ -2533,6 +2537,12 @@ static int rdt_get_tree(struct fs_context *fc)
>>  
>>  	closid_init();
>>  
>> +	ret = rdtgroup_add_files(rdtgroup_default.kn, RFTYPE_CTRL_BASE);
>> +	if (ret)
>> +		goto out_schemata_free;
>> +
>> +	kernfs_activate(rdtgroup_default.kn);
>> +
>>  	ret = rdtgroup_create_info_dir(rdtgroup_default.kn);
>>  	if (ret < 0)
>>  		goto out_schemata_free;
>> @@ -2589,6 +2599,8 @@ static int rdt_get_tree(struct fs_context *fc)
>>  	schemata_list_destroy();
>>  out_ctx:
>>  	rdt_disable_ctx(ctx);
>> +out_root:
>> +	kernfs_destroy_root(rdt_root);
> 
> Please ensure that all rdtgroup_setup_root() cleanup is done
> here. It seems to me that rdtgroup_default.kn can be left pointing
> to freed memory. Since this cleanup is done multiple places (here
> and rdt_kill_sb()) it may help to create a helper.

Ok. Sure. Will do.

-- 
Thanks
Babu Moger