Re: [RESEND PATCH v4 08/15] fs/resctrl: Add interface to display supported and active kernel-mode policy

Hi Babu,

On 8/13/26 9:04 AM, Babu Moger wrote:
> Hi Reinette,
> 
> On 8/12/26 18:38, Reinette Chatre wrote:
>> Hi Babu,
>>
>> On 8/12/26 3:57 PM, Moger, Babu wrote:
>>> On 8/10/2026 10:18 PM, Reinette Chatre wrote:
>>>> On 7/7/26 2:50 PM, Babu Moger wrote:
>>
>> ...
>>
>>>>> +         */
>>>>> +        rdtgrp = resctrl_kcfg.k_rdtgrp;
>>>>> +        if (!rdtgrp) {
>>>>> +            ret = -ENOENT;
>>>>> +            goto out_unlock;
>>>>
>>>> If this fails there needs to be content in last_cmd_status. Otherwise this
>>>> fails and then last_cmd_status reads "ok" or worse .. an old failure message.
>>>
>>> if (WARN_ON(!rdtgrp)) {
>>>      rdt_last_cmd_puts("Invalid kernel mode group\n");
>>>      ret = -ENOENT;
>>>      goto out_unlock;
>>> }
>> It is not clear to me why the WARN_ON() was added. Is the resource group not being
>> associated with kernel mode not a legitimate scenario if the kernel mode group was
>> re-assigned while the reader of this file was blocked on the mutex?
>>
> A valid group is required whenever any global mode is enabled.
> Reaching this condition without one is unexpected and should be
> treated as a bug.
> 
> To help catch this, I added a WARN_ON() to log the issue. I think
> updating last_cmd_status is reasonable as well and should provide
> the necessary user-visible error indication.

ah - thanks. I misread this snippet as an interaction with a resource group's
files.

Reinette