linux-kernel - Re: [PATCH v2 27/33] x86/intel_rdt_rdtgroup.c: Implement resctrl file system commands

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Date:   Thu, 8 Sep 2016 18:23:14 -0700
From:   Fenghua Yu <fenghua.yu@...el.com>
To:     Shaohua Li <shli@...com>
Cc:     Fenghua Yu <fenghua.yu@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <h.peter.anvin@...el.com>,
        Ingo Molnar <mingo@...e.hu>, Tony Luck <tony.luck@...el.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Tejun Heo <tj@...nel.org>, Borislav Petkov <bp@...e.de>,
        Stephane Eranian <eranian@...gle.com>,
        Marcelo Tosatti <mtosatti@...hat.com>,
        David Carrillo-Cisneros <davidcc@...gle.com>,
        Ravi V Shankar <ravi.v.shankar@...el.com>,
        Vikas Shivappa <vikas.shivappa@...ux.intel.com>,
        Sai Prakhya <sai.praneeth.prakhya@...el.com>,
        linux-kernel <linux-kernel@...r.kernel.org>, x86 <x86@...nel.org>
Subject: Re: [PATCH v2 27/33] x86/intel_rdt_rdtgroup.c: Implement resctrl
 file system commands

On Thu, Sep 08, 2016 at 03:04:12PM -0700, Shaohua Li wrote:
> On Thu, Sep 08, 2016 at 02:57:21AM -0700, Fenghua Yu wrote:
> >  /*
> >   * kernfs_root - find out the kernfs_root a kernfs_node belongs to
> > @@ -730,6 +749,110 @@ static void rdtgroup_destroy_locked(struct rdtgroup *rdtgrp)
> >  	kernfs_remove(rdtgrp->kn);
> >  }
> >  
> > +static int rdtgroup_mkdir(struct kernfs_node *parent_kn, const char *name,
> > +			umode_t mode)
> > +{
> > +	struct rdtgroup *parent, *rdtgrp;
> > +	struct rdtgroup_root *root;
> > +	struct kernfs_node *kn;
> > +	int ret;
> > +
> > +	if (parent_kn != root_rdtgrp->kn)
> > +		return -EPERM;
> > +
> 
> So we can't create nested groups. Is this limitation temporary? I don't see
> this is mentioned in the interface document.

Yes, we cannot create nested groups, i.e. up to one level of sub-directory
in the resctrl file system. This is different from cgroup.

I can add this info in the intel_rdt_ui.txt.

Thanks.

-Fenghua