netdev - Re: [PATCH v4 6/9] drivers/base/power: add dpm_sysfs_change

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Date:   Mon, 24 Feb 2020 19:00:20 +0100
From:   Christian Brauner <christian.brauner@...ntu.com>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>, Pavel Machek <pavel@....cz>,
        Jakub Kicinski <kuba@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Stephen Hemminger <stephen@...workplumber.org>,
        Linux PM <linux-pm@...r.kernel.org>
Subject: Re: [PATCH v4 6/9] drivers/base/power: add dpm_sysfs_change_owner()

On Mon, Feb 24, 2020 at 06:56:03PM +0100, Rafael J. Wysocki wrote:
> On Mon, Feb 24, 2020 at 6:21 PM Christian Brauner
> <christian.brauner@...ntu.com> wrote:
> >
> > Add a helper to change the owner of a device's power entries. This
> > needs to happen when the ownership of a device is changed, e.g. when
> > moving network devices between network namespaces.
> > This function will be used to correctly account for ownership changes,
> > e.g. when moving network devices between network namespaces.
> >
> > Signed-off-by: Christian Brauner <christian.brauner@...ntu.com>
> > ---
> > /* v2 */
> > - "Rafael J. Wysocki" <rafael@...nel.org>:
> >   -  Fold if (dev->power.wakeup && dev->power.wakeup->dev) check into
> >      if (device_can_wakeup(dev)) check since the former can never be true if
> >      the latter is false.
> >
> > - Christian Brauner <christian.brauner@...ntu.com>:
> >   - Place (dev->power.wakeup && dev->power.wakeup->dev) check under
> >     CONFIG_PM_SLEEP ifdefine since it will wakeup_source will only be available
> >     when this config option is set.
> >
> > /* v3 */
> > -  Greg Kroah-Hartman <gregkh@...uxfoundation.org>:
> >    - Add explicit uid/gid parameters.
> >
> > /* v4 */
> > - "Rafael J. Wysocki" <rafael@...nel.org>:
> >    - Remove in-function #ifdef in favor of separate helper that is a nop
> >      whenver !CONFIG_PM_SLEEP.
> > ---
> >  drivers/base/core.c        |  4 +++
> >  drivers/base/power/power.h |  3 ++
> >  drivers/base/power/sysfs.c | 61 +++++++++++++++++++++++++++++++++++++-
> >  3 files changed, 67 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/base/core.c b/drivers/base/core.c
> > index 988f34ce2eb0..fb8b7990f6fd 100644
> > --- a/drivers/base/core.c
> > +++ b/drivers/base/core.c
> > @@ -3552,6 +3552,10 @@ int device_change_owner(struct device *dev, kuid_t kuid, kgid_t kgid)
> >         if (error)
> >                 goto out;
> >
> > +       error = dpm_sysfs_change_owner(dev, kuid, kgid);
> > +       if (error)
> > +               goto out;
> > +
> >  #ifdef CONFIG_BLOCK
> >         if (sysfs_deprecated && dev->class == &block_class)
> >                 goto out;
> > diff --git a/drivers/base/power/power.h b/drivers/base/power/power.h
> > index 444f5c169a0b..54292cdd7808 100644
> > --- a/drivers/base/power/power.h
> > +++ b/drivers/base/power/power.h
> > @@ -74,6 +74,7 @@ extern int pm_qos_sysfs_add_flags(struct device *dev);
> >  extern void pm_qos_sysfs_remove_flags(struct device *dev);
> >  extern int pm_qos_sysfs_add_latency_tolerance(struct device *dev);
> >  extern void pm_qos_sysfs_remove_latency_tolerance(struct device *dev);
> > +extern int dpm_sysfs_change_owner(struct device *dev, kuid_t kuid, kgid_t kgid);
> >
> >  #else /* CONFIG_PM */
> >
> > @@ -88,6 +89,8 @@ static inline void pm_runtime_remove(struct device *dev) {}
> >
> >  static inline int dpm_sysfs_add(struct device *dev) { return 0; }
> >  static inline void dpm_sysfs_remove(struct device *dev) {}
> > +static inline int dpm_sysfs_change_owner(struct device *dev, kuid_t kuid,
> > +                                        kgid_t kgid) { return 0; }
> >
> >  #endif
> >
> > diff --git a/drivers/base/power/sysfs.c b/drivers/base/power/sysfs.c
> > index d7d82db2e4bc..d2955784d98d 100644
> > --- a/drivers/base/power/sysfs.c
> > +++ b/drivers/base/power/sysfs.c
> > @@ -480,6 +480,20 @@ static ssize_t wakeup_last_time_ms_show(struct device *dev,
> >         return enabled ? sprintf(buf, "%lld\n", msec) : sprintf(buf, "\n");
> >  }
> >
> > +static int dpm_sysfs_wakeup_change_owner(struct device *dev, kuid_t kuid,
> > +                                        kgid_t kgid)
> > +{
> > +       int rc = 0;
> > +
> > +       if (dev->power.wakeup && dev->power.wakeup->dev) {
> > +               rc = device_change_owner(dev->power.wakeup->dev, kuid, kgid);
> > +               if (rc)
> > +                       return rc;
> > +       }
> > +
> > +       return rc;
> 
> Why not to do
> 
> if (dev->power.wakeup && dev->power.wakeup->dev)
>         return device_change_owner(dev->power.wakeup->dev, kuid, kgid);
> 
> return 0;
> 
> here instead?

Yeah, sure, can do.

Christian