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

[Babu Moger]

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.

thanks
Babu