Re: [Qemu-devel] [PATCH v8 2/6] virtio-pmem: Add virtio pmem driver

[David Hildenbrand]

>>
>>> +   }
>>> +
>>> +   /* When host has read buffer, this completes via host_ack */
>>
>> "A host repsonse results in "host_ack" getting called" ... ?
>>
>>> +   wait_event(req->host_acked, req->done);
>>> +   err = req->ret;
>>> +ret:
>>> +   kfree(req);
>>> +   return err;
>>> +};
>>> +
>>> +/* The asynchronous flush callback function */
>>> +int async_pmem_flush(struct nd_region *nd_region, struct bio *bio)
>>> +{
>>> +   int rc = 0;
>>> +
>>> +   /* 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) {
>>> +           struct bio *child = bio_alloc(GFP_ATOMIC, 0);
>>> +
>>> +           if (!child)
>>> +                   return -ENOMEM;
>>> +           bio_copy_dev(child, bio);
>>> +           child->bi_opf = REQ_PREFLUSH;
>>> +           child->bi_iter.bi_sector = -1;
>>> +           bio_chain(child, bio);
>>> +           submit_bio(child);
>>
>> return 0;
>>
>> Then, drop the "else" case and "int rc" and do directly
>>
>> if (virtio_pmem_flush(nd_region))
>>      return -EIO;
> 
> and another 'return 0' here :)
> 
> I don't like return from multiple places instead I prefer
> single exit point from function.

Makes this function more complicated than necessary. I agree when there
are locks involved.

>  
>>
>>> +
>>> +   return 0;
>>> +};
>>> +
>>> +static int virtio_pmem_probe(struct virtio_device *vdev)
>>> +{
>>> +   int err = 0;
>>> +   struct resource res;
>>> +   struct virtio_pmem *vpmem;
>>> +   struct nd_region_desc ndr_desc = {};
>>> +   int nid = dev_to_node(&vdev->dev);
>>> +   struct nd_region *nd_region;
>>
>> Nit: use reverse Christmas tree layout :)
> 
> Done.
> 
>>
>>> +
>>> +   if (!vdev->config->get) {
>>> +           dev_err(&vdev->dev, "%s failure: config access disabled\n",
>>> +                   __func__);
>>> +           return -EINVAL;
>>> +   }
>>> +
>>> +   vpmem = devm_kzalloc(&vdev->dev, sizeof(*vpmem), GFP_KERNEL);
>>> +   if (!vpmem) {
>>> +           err = -ENOMEM;
>>> +           goto out_err;
>>> +   }
>>> +
>>> +   vpmem->vdev = vdev;
>>> +   vdev->priv = vpmem;
>>> +   err = init_vq(vpmem);
>>> +   if (err)
>>> +           goto out_err;
>>> +
>>> +   virtio_cread(vpmem->vdev, struct virtio_pmem_config,
>>> +                   start, &vpmem->start);
>>> +   virtio_cread(vpmem->vdev, struct virtio_pmem_config,
>>> +                   size, &vpmem->size);
>>> +
>>> +   res.start = vpmem->start;
>>> +   res.end   = vpmem->start + vpmem->size-1;
>>> +   vpmem->nd_desc.provider_name = "virtio-pmem";
>>> +   vpmem->nd_desc.module = THIS_MODULE;
>>> +
>>> +   vpmem->nvdimm_bus = nvdimm_bus_register(&vdev->dev,
>>> +                                           &vpmem->nd_desc);
>>> +   if (!vpmem->nvdimm_bus)
>>> +           goto out_vq;
>>> +
>>> +   dev_set_drvdata(&vdev->dev, vpmem->nvdimm_bus);
>>> +
>>> +   ndr_desc.res = &res;
>>> +   ndr_desc.numa_node = nid;
>>> +   ndr_desc.flush = async_pmem_flush;
>>> +   set_bit(ND_REGION_PAGEMAP, &ndr_desc.flags);
>>> +   set_bit(ND_REGION_ASYNC, &ndr_desc.flags);
>>> +   nd_region = nvdimm_pmem_region_create(vpmem->nvdimm_bus, &ndr_desc);
>>> +
>>
>> I'd drop this empty line.
> 
> hmm.
> 

The common pattern after allocating something, immediately check for it
in the next line (like you do throughout this patch ;) )

...
>> You are not freeing "vdev->priv".
> 
> vdev->priv is vpmem which is allocated using devm API.

I'm confused. Looking at drivers/virtio/virtio_balloon.c:

static void virtballoon_remove(struct virtio_device *vdev)
{
        struct virtio_balloon *vb = vdev->priv;

        ...

        kfree(vb);
}

I think you should do the same here, vdev->priv is allocated in
virtio_pmem_probe.

But maybe I am missing something important here :)

>>
>>> +   nvdimm_bus_unregister(nvdimm_bus);
>>> +   vdev->config->del_vqs(vdev);
>>> +   vdev->config->reset(vdev);
>>> +}
>>> +

-- 

Thanks,

David / dhildenb