Re: [Qemu-devel] [PATCH v9 2/7] virtio-pmem: Add virtio pmem driver

[Jakub Staroń]

On 5/14/19 7:54 AM, Pankaj Gupta wrote:
> +             if (!list_empty(&vpmem->req_list)) {
> +                     req_buf = list_first_entry(&vpmem->req_list,
> +                                     struct virtio_pmem_request, list);
> +                     req_buf->wq_buf_avail = true;
> +                     wake_up(&req_buf->wq_buf);
> +                     list_del(&req_buf->list);
Yes, this change is the right one, thank you!

> +      /*
> +       * If virtqueue_add_sgs returns -ENOSPC then req_vq virtual
> +       * queue does not have free descriptor. We add the request
> +       * to req_list and wait for host_ack to wake us up when free
> +       * slots are available.
> +       */
> +     while ((err = virtqueue_add_sgs(vpmem->req_vq, sgs, 1, 1, req,
> +                                     GFP_ATOMIC)) == -ENOSPC) {
> +
> +             dev_err(&vdev->dev, "failed to send command to virtio pmem" \
> +                     "device, no free slots in the virtqueue\n");
> +             req->wq_buf_avail = false;
> +             list_add_tail(&req->list, &vpmem->req_list);
> +             spin_unlock_irqrestore(&vpmem->pmem_lock, flags);
> +
> +             /* A host response results in "host_ack" getting called */
> +             wait_event(req->wq_buf, req->wq_buf_avail);
> +             spin_lock_irqsave(&vpmem->pmem_lock, flags);
> +     }
> +     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.
> +      */
> +     if (err || !err1) {
> +             dev_info(&vdev->dev, "failed to send command to virtio pmem 
> device\n");
> +             err = -EIO;
> +     } else {
> +             /* A host repsonse results in "host_ack" getting called */
> +             wait_event(req->host_acked, req->done);
> +             err = req->ret;
> +I confirm that the failures I was facing with the `-ENOSPC` error path are 
> not present in v9.

Best,
Jakub Staron