On Mon, Aug 26, 2024 at 05:40:37AM +0000, Michael Kelley wrote:
> From: Naman Jain <namjain@xxxxxxxxxxxxxxxxxxx> Sent: Sunday, August 25, 2024 10:32 PM
> >
> > On 8/25/2024 8:27 AM, Michael Kelley wrote:
> > > From: Naman Jain <namjain@xxxxxxxxxxxxxxxxxxx> Sent: Thursday, August 22, 2024 4:09 AM
> > >>
> > >> Rescind offer handling relies on rescind callbacks for some of the
> > >> resources cleanup, if they are registered. It does not unregister
> > >> vmbus device for the primary channel closure, when callback is
> > >> registered.
> > >> Add logic to unregister vmbus for the primary channel in rescind callback
> > >> to ensure channel removal and relid release, and to ensure rescind flag
> > >> is false when driver probe happens again.
> > >>
> > >> Fixes: ca3cda6fcf1e ("uio_hv_generic: add rescind support")
> > >> Signed-off-by: Naman Jain <namjain@xxxxxxxxxxxxxxxxxxx>
> > >> ---
> > >> drivers/hv/vmbus_drv.c | 1 +
> > >> drivers/uio/uio_hv_generic.c | 7 +++++++
> > >> 2 files changed, 8 insertions(+)
> > >>
> > >> diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
> > >> index c857dc3975be..4bae382a3eb4 100644
> > >> --- a/drivers/hv/vmbus_drv.c
> > >> +++ b/drivers/hv/vmbus_drv.c
> > >> @@ -1952,6 +1952,7 @@ void vmbus_device_unregister(struct hv_device *device_obj)
> > >> */
> > >> device_unregister(&device_obj->device);
> > >> }
> > >> +EXPORT_SYMBOL_GPL(vmbus_device_unregister);
> > >>
> > >> #ifdef CONFIG_ACPI
> > >> /*
> > >> diff --git a/drivers/uio/uio_hv_generic.c b/drivers/uio/uio_hv_generic.c
> > >> index c99890c16d29..ea26c0b460d6 100644
> > >> --- a/drivers/uio/uio_hv_generic.c
> > >> +++ b/drivers/uio/uio_hv_generic.c
> > >> @@ -121,6 +121,13 @@ static void hv_uio_rescind(struct vmbus_channel *channel)
> > >>
> > >> /* Wake up reader */
> > >> uio_event_notify(&pdata->info);
> > >> +
> > >> + /*
> > >> + * With rescind callback registered, rescind path will not unregister the device
> > >> + * when the primary channel is rescinded. Without it, next onoffer msg does not come.
> > >> + */
> > >> + if (!channel->primary_channel)
> > >> + vmbus_device_unregister(channel->device_obj);
> > >
> > > When the rescind callback is *not* set, vmbus_onoffer_rescind() makes the
> > > call to vmbus_device_unregister(). But it does so bracketed with get_device()/
> > > put_device(). Your code here does not do the bracketing. Is there a reason for
> > > the difference? Frankly, I'm not sure why vmbus_onoffer_rescind() does the
> > > bracketing, and I can't definitively say if it is really needed. So I guess I'm
> > > just asking if you know. :-)
> > >
> > > Michael
> >
> > IMHO, we have already NULL checked channel->device_obj and other couple
> > of things to make sure we are safe to clean this up. At other places as
> > well, I don't see the use of put and get device. So I think its not
> > required. I am open to suggestions.
> >
> > Regards,
> > Naman
>
> OK. I'm good with what you've said, and don't have any further suggestions.
> Go with what your patch already has. :-)
>
> Michael
Michael,
If we look at vmbus_onoffer_rescind function, hv_uio_rescind can only be called
if channel->device_obj is not NULL. By this if we conclude that hv_uio_rescind can
never be called for secondary channel I think we can simplify hv_uio_rescind
only for primary channel.
In the first patch of this series, instead of this:
+ struct hv_device *hv_dev = channel->primary_channel ?
+ channel->primary_channel->device_obj : channel->device_obj;
We can only have
+ struct hv_device *hv_dev = channel->device_obj;
In second patch, instead of this:
+ if (!channel->primary_channel)
+ vmbus_device_unregister(channel->device_obj);
We can only have:
+ vmbus_device_unregister(channel->device_obj);
Possibly WARN for secondary channel is also not required as that will never happen ?
- Saurabh
