Re: [PATCH v12 2/7] virtio-pmem: Add virtio pmem driver

From: Cornelia Huck <cohuck@redhat.com>
To: Pankaj Gupta <pagupta@redhat.com>
Cc: rdunlap@infradead.org, jack@suse.cz, kvm@vger.kernel.org,
	mst@redhat.com, david@fromorbit.com, qemu-devel@nongnu.org,
	virtualization@lists.linux-foundation.org, dm-devel@redhat.com,
	adilger kernel <adilger.kernel@dilger.ca>,
	zwisler@kernel.org, aarcange@redhat.com,
	dave jiang <dave.jiang@intel.com>,
	jstaron@google.com, linux-nvdimm@lists.01.org,
	vishal l verma <vishal.l.verma@intel.com>,
	willy@infradead.org, hch@infradead.org,
	linux-acpi@vger.kernel.org, jmoyer@redhat.com,
	linux-ext4@vger.kernel.org, lenb@kernel.org, kilobyte@angband.pl,
	riel@surriel.com, yuval shaia <yuval.shaia@oracle.com>,
	stefanha@redhat.com, pbonzini@redhat.com,
	dan j williams <dan.j.williams@intel.com>,
	lcapitulino@redhat.com, nilal@redhat.com, tytso@mit.edu,
	xiaoguangrong eric <xiaoguangrong.eric@gmail.com>,
	snitzer@redhat.com, darrick wong <darrick.wong@oracle.com>,
	rjw@rjwysocki.net, linux-ker
Subject: Re: [PATCH v12 2/7] virtio-pmem: Add virtio pmem driver
Date: Wed, 12 Jun 2019 08:37:11 +0200	[thread overview]
Message-ID: <20190612083711.2c0cfd7e.cohuck__9487.12213882885$1560321550$gmane$org@redhat.com> (raw)
In-Reply-To: <1003601865.34513553.1560310490030.JavaMail.zimbra@redhat.com>

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, 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.

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

> 
> 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.

>         }
>  
>         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