linux-kernel - Re: [PATCH v4 13/16] selftests/resctrl: Convert ctrlgrp & mongrp to pointers

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Date: Thu, 30 May 2024 14:44:57 +0300 (EEST)
From: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To: Reinette Chatre <reinette.chatre@...el.com>
cc: linux-kselftest@...r.kernel.org, Shuah Khan <shuah@...nel.org>, 
    Babu Moger <babu.moger@....com>, 
    Maciej Wieczór-Retman <maciej.wieczor-retman@...el.com>, 
    LKML <linux-kernel@...r.kernel.org>, Fenghua Yu <fenghua.yu@...el.com>, 
    Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [PATCH v4 13/16] selftests/resctrl: Convert ctrlgrp & mongrp to
 pointers

On Wed, 29 May 2024, Reinette Chatre wrote:

> Hi Ilpo,
> 
> On 5/20/24 5:30 AM, Ilpo Järvinen wrote:
> > The struct resctrl_val_param has control and monitor groups as char
> > arrays but they are not supposed to be mutated within resctrl_val().
> > 
> > Convert the ctrlgrp and mongrp char array within resctrl_val_param to
> > plain const char pointers and adjust the strlen() based checks to
> > check NULL instead.
> > 
> > Convert !grp_name check in create_grp() into internal sanity check by
> > returning error if the caller asked to create a group but doesn't
> > provide a name for the group. The existing code already abides this by
> > only calling create_grp() if mongrp is non-NULL so the error should
> > never be returned with the current selftests (ctrlgrp is never NULL).
> > 
> > Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
> > ---
> > 
> > v3:
> > - Removed wrong comment
> > - Changed grp_name check to return -1 on fail (internal sanity check)
> > ---
> >   tools/testing/selftests/resctrl/resctrl.h   |  4 ++--
> >   tools/testing/selftests/resctrl/resctrlfs.c | 15 +++++----------
> >   2 files changed, 7 insertions(+), 12 deletions(-)
> > 
> > diff --git a/tools/testing/selftests/resctrl/resctrl.h
> > b/tools/testing/selftests/resctrl/resctrl.h
> > index 5967389038d4..a999fbc13fd3 100644
> > --- a/tools/testing/selftests/resctrl/resctrl.h
> > +++ b/tools/testing/selftests/resctrl/resctrl.h
> > @@ -91,8 +91,8 @@ struct resctrl_test {
> >    */
> >   struct resctrl_val_param {
> >   	char		*resctrl_val;
> > -	char		ctrlgrp[64];
> > -	char		mongrp[64];
> > +	const char	*ctrlgrp;
> > +	const char	*mongrp;
> >   	char		filename[64];
> >   	unsigned long	mask;
> >   	int		num_of_runs;
> > diff --git a/tools/testing/selftests/resctrl/resctrlfs.c
> > b/tools/testing/selftests/resctrl/resctrlfs.c
> > index a0e84157eb63..6b4448588666 100644
> > --- a/tools/testing/selftests/resctrl/resctrlfs.c
> > +++ b/tools/testing/selftests/resctrl/resctrlfs.c
> > @@ -464,13 +464,8 @@ static int create_grp(const char *grp_name, char *grp,
> > const char *parent_grp)
> >   	struct dirent *ep;
> >   	DIR *dp;
> >   -	/*
> > -	 * At this point, we are guaranteed to have resctrl FS mounted and if
> > -	 * length of grp_name == 0, it means, user wants to use root con_mon
> > -	 * grp, so do nothing
> > -	 */
> > -	if (strlen(grp_name) == 0)
> > -		return 0;
> > +	if (!grp_name)
> > +		return -1;
> 
> As I said during review of v2, this should not be an error. I went back to
> read
> your comments and the argument that this is done for benefit of API is unclear
> since
> the default control group does not have a name, exactly what create_grp()
> supports
> when not returning an error in this case.

Okay, I did not know about this expectation related to the default control 
group because it's not used anywhere in the selftest code that always 
provides a ctrlgrp name.

I'll change it to return 0.

-- 
 i.