Re: [PATCH v1 1/7] vfio/ccw: create a parent struct

[Eric Farman <farman@linux.ibm.com>]

On Fri, 2022-10-28 at 12:51 -0400, Matthew Rosato wrote:
> On 10/19/22 12:21 PM, Eric Farman wrote:
> > Move the stuff associated with the mdev parent (and thus the
> > subchannel struct) into its own struct, and leave the rest in
> > the existing private structure.
> > 
> > The subchannel will point to the parent, and the parent will point
> > to the private, for the areas where one or both are needed. Further
> > separation of these structs will follow.
> > 
> > Signed-off-by: Eric Farman <farman@linux.ibm.com>
> > ---
> >  drivers/s390/cio/vfio_ccw_drv.c     | 104 ++++++++++++++++++++----
> > ----
> >  drivers/s390/cio/vfio_ccw_ops.c     |   9 ++-
> >  drivers/s390/cio/vfio_ccw_parent.h  |  28 ++++++++
> >  drivers/s390/cio/vfio_ccw_private.h |   5 --
> >  4 files changed, 112 insertions(+), 34 deletions(-)
> >  create mode 100644 drivers/s390/cio/vfio_ccw_parent.h
> > 
> > diff --git a/drivers/s390/cio/vfio_ccw_drv.c
> > b/drivers/s390/cio/vfio_ccw_drv.c
> > index 7f5402fe857a..634760ca0dea 100644
> > --- a/drivers/s390/cio/vfio_ccw_drv.c
> > +++ b/drivers/s390/cio/vfio_ccw_drv.c
> > @@ -20,6 +20,7 @@
> >  #include "chp.h"
> >  #include "ioasm.h"
> >  #include "css.h"
> > +#include "vfio_ccw_parent.h"
> >  #include "vfio_ccw_private.h"
> >  
> >  struct workqueue_struct *vfio_ccw_work_q;
> > @@ -36,7 +37,8 @@ debug_info_t *vfio_ccw_debug_trace_id;
> >   */
> >  int vfio_ccw_sch_quiesce(struct subchannel *sch)
> >  {
> > -       struct vfio_ccw_private *private = dev_get_drvdata(&sch-
> > >dev);
> > +       struct vfio_ccw_parent *parent = dev_get_drvdata(&sch-
> > >dev);
> > +       struct vfio_ccw_private *private = dev_get_drvdata(&parent-
> > >dev);
> >         DECLARE_COMPLETION_ONSTACK(completion);
> >         int iretry, ret = 0;
> >  
> > @@ -51,19 +53,21 @@ int vfio_ccw_sch_quiesce(struct subchannel
> > *sch)
> >                         break;
> >                 }
> >  
> > -               /*
> > -                * Flush all I/O and wait for
> > -                * cancel/halt/clear completion.
> > -                */
> > -               private->completion = &completion;
> > -               spin_unlock_irq(sch->lock);
> > +               if (private) {
> 
> Is it valid to ever reach this code with private == NULL?  If no,
> then this should probably be a WARN_ON upfront?

Hrm, the caller jumps from private -> subchannel, so it would be weird
if we couldn't then go back the other way. Probably impossible, I'll
unwind these whitespace changes and put the WARN_ON on top. Thanks for
the tip.

> 
> > +                       /*
> > +                        * Flush all I/O and wait for
> > +                        * cancel/halt/clear completion.
> > +                        */
> > +                       private->completion = &completion;
> > +                       spin_unlock_irq(sch->lock);
> >  
> > -               if (ret == -EBUSY)
> > -                       wait_for_completion_timeout(&completion,
> > 3*HZ);
> > +                       if (ret == -EBUSY)
> > +                               wait_for_completion_timeout(&comple
> > tion, 3*HZ);
> >  
> > -               private->completion = NULL;
> > -               flush_workqueue(vfio_ccw_work_q);
> > -               spin_lock_irq(sch->lock);
> > +                       private->completion = NULL;
> > +                       flush_workqueue(vfio_ccw_work_q);
> > +                       spin_lock_irq(sch->lock);
> > +               }
> >                 ret = cio_disable_subchannel(sch);
> >         } while (ret == -EBUSY);
> >  
> 
> .. snip ..
> 
> > diff --git a/drivers/s390/cio/vfio_ccw_parent.h
> > b/drivers/s390/cio/vfio_ccw_parent.h
> > new file mode 100644
> > index 000000000000..834c00077802
> > --- /dev/null
> > +++ b/drivers/s390/cio/vfio_ccw_parent.h
> > @@ -0,0 +1,28 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +/*
> > + * MDEV Parent contents for vfio_ccw driver
> > + *
> > + * Copyright IBM Corp. 2022
> > + */
> > +
> > +#ifndef _VFIO_CCW_PARENT_H_
> > +#define _VFIO_CCW_PARENT_H_
> > +
> > +#include <linux/mdev.h>
> > +
> > +/**
> > + * struct vfio_ccw_parent
> > + *
> > + * @dev: embedded device struct
> > + * @parent: parent data structures for mdevs created
> > + * @mdev_type(s): identifying information for mdevs created
> > + */
> > +struct vfio_ccw_parent {
> > +       struct device           dev;
> > +
> > +       struct mdev_parent      parent;
> > +       struct mdev_type        mdev_type;
> > +       struct mdev_type        *mdev_types[1];
> > +};
> 
> Structure itself seems fine, but any reason we need a new file for
> it?
> 

Not really. I could leave it in _private.h, but that file is just a
dumping ground for everything so I thought this would be a good
opportunity to start to cleaning that up. But it wouldn't bother me to
leave that whole process to another day too.