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Date:   Wed, 12 Jun 2019 06:50:34 -0400 (EDT)
From:   Pankaj Gupta <pagupta@redhat.com>
To:     Cornelia Huck <cohuck@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH v12 2/7] virtio-pmem: Add virtio pmem
 driver
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Thread-Topic: virtio-pmem: Add virtio pmem driver
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> 
> Hi Pankaj,
> 
> On Tue, 11 Jun 2019 23:34:50 -0400 (EDT)
> Pankaj Gupta <pagupta@redhat.com> wrote:
> 
> > Hi Cornelia,
> > 
> > > On Tue, 11 Jun 2019 22:07:57 +0530
> > > Pankaj Gupta <pagupta@redhat.com> wrote:
> 
> 
> > > > +	err1 = virtqueue_kick(vpmem->req_vq);
> > > > +	spin_unlock_irqrestore(&vpmem->pmem_lock, flags);
> > > > +	/*
> > > > +	 * virtqueue_add_sgs failed with error different than -ENOSPC, we
> > > > can't
> > > > +	 * do anything about that.
> > > > +	 */
> > > 
> > > Does it make sense to kick if you couldn't add at all?
> > 
> > When we could not add because of -ENOSPC we are waiting and when buffer is
> > added
> > then only we do a kick. For any other error which might be a rare
> > occurrence, I think
> > kick is harmless here and keeps the code clean?
> 
> Yes, I agree it does not hurt. Let's keep it as-is.

Sure.

> 
> 
> > Sure, Thank you. Attaching below on top changes on current patch2 based on
> > your suggestions. Let me know if these are okay and then will send official
> > v13 to for upstream merging.
> 
> Looks good to me, except for one change.

Sure. Will send v13 shortly.

> 
> [Again sorry for the late review, did not want to get the version
> numbers up :)]

Thank you :)

> 
> > 
> > Thanks,
> > Pankaj
> > 
> > ===============
> > 
> > diff --git a/drivers/nvdimm/nd_virtio.c b/drivers/nvdimm/nd_virtio.c
> > index efc535723517..5b8d2367da0b 100644
> > --- a/drivers/nvdimm/nd_virtio.c
> > +++ b/drivers/nvdimm/nd_virtio.c
> > @@ -10,7 +10,7 @@
> >  #include "nd.h"
> >  
> >   /* The interrupt handler */
> > -void host_ack(struct virtqueue *vq)
> > +void virtio_pmem_host_ack(struct virtqueue *vq)
> >  {
> >         struct virtio_pmem *vpmem = vq->vdev->priv;
> >         struct virtio_pmem_request *req_data, *req_buf;
> > @@ -32,10 +32,10 @@ void host_ack(struct virtqueue *vq)
> >         }
> >         spin_unlock_irqrestore(&vpmem->pmem_lock, flags);
> >  }
> > -EXPORT_SYMBOL_GPL(host_ack);
> > +EXPORT_SYMBOL_GPL(virtio_pmem_host_ack);
> >  
> >   /* The request submission function */
> > -int virtio_pmem_flush(struct nd_region *nd_region)
> > +static int virtio_pmem_flush(struct nd_region *nd_region)
> >  {
> >         struct virtio_device *vdev = nd_region->provider_data;
> >         struct virtio_pmem *vpmem  = vdev->priv;
> > @@ -69,7 +69,7 @@ int virtio_pmem_flush(struct nd_region *nd_region)
> >         while ((err = virtqueue_add_sgs(vpmem->req_vq, sgs, 1, 1, req_data,
> >                                         GFP_ATOMIC)) == -ENOSPC) {
> >  
> > -               dev_err(&vdev->dev, "failed to send command to virtio pmem
> > device, no free slots in the virtqueue\n");
> > +               dev_info(&vdev->dev, "failed to send command to virtio pmem
> > device, no free slots in the virtqueue\n");
> >                 req_data->wq_buf_avail = false;
> >                 list_add_tail(&req_data->list, &vpmem->req_list);
> >                 spin_unlock_irqrestore(&vpmem->pmem_lock, flags);
> > @@ -90,7 +90,8 @@ int virtio_pmem_flush(struct nd_region *nd_region)
> >         } else {
> >                 /* A host repsonse results in "host_ack" getting called */
> >                 wait_event(req_data->host_acked, req_data->done);
> > -               err = virtio32_to_cpu(vdev, req_data->resp.ret);
> > +               if ((err = virtio32_to_cpu(vdev, req_data->resp.ret)))
> > +                       err = -EIO;
> 
> Hm, why are you making this change? I think the previous code was fine.

Yes, Something came to my mind while making the change but I agree will keep
this as it was before.

> 
> >         }
> >  
> >         kfree(req_data);
> > @@ -100,7 +101,8 @@ int virtio_pmem_flush(struct nd_region *nd_region)
> >  /* The asynchronous flush callback function */
> >  int async_pmem_flush(struct nd_region *nd_region, struct bio *bio)
> >  {
> > -       /* Create child bio for asynchronous flush and chain with
> > +       /*
> > +        * Create child bio for asynchronous flush and chain with
> >          * parent bio. Otherwise directly call nd_region flush.
> >          */
> >         if (bio && bio->bi_iter.bi_sector != -1) {
> > diff --git a/drivers/nvdimm/virtio_pmem.c b/drivers/nvdimm/virtio_pmem.c
> > index b60ebd8cd2fd..5e3d07b47e0c 100644
> > --- a/drivers/nvdimm/virtio_pmem.c
> > +++ b/drivers/nvdimm/virtio_pmem.c
> > @@ -19,7 +19,7 @@ static int init_vq(struct virtio_pmem *vpmem)
> >  {
> >         /* single vq */
> >         vpmem->req_vq = virtio_find_single_vq(vpmem->vdev,
> > -                                               host_ack, "flush_queue");
> > +                                       virtio_pmem_host_ack,
> > "flush_queue");
> >         if (IS_ERR(vpmem->req_vq))
> >                 return PTR_ERR(vpmem->req_vq);
> >  
> > diff --git a/drivers/nvdimm/virtio_pmem.h b/drivers/nvdimm/virtio_pmem.h
> > index 6e47521be158..998efbc7660c 100644
> > --- a/drivers/nvdimm/virtio_pmem.h
> > +++ b/drivers/nvdimm/virtio_pmem.h
> > @@ -50,6 +50,6 @@ struct virtio_pmem {
> >         uint64_t size;
> >  };
> >  
> > -void host_ack(struct virtqueue *vq);
> > +void virtio_pmem_host_ack(struct virtqueue *vq);
> >  int async_pmem_flush(struct nd_region *nd_region, struct bio *bio);
> >  #endif
> 
> 
>