On Fri, Nov 15, 2019 at 03:55:41PM -0500, Vivek Goyal wrote:
>  /* Callback from libvhost-user */
>  static void fv_set_features(VuDev *dev, uint64_t features)
>  {
> +    struct fv_VuDev *vud = container_of(dev, struct fv_VuDev, dev);
> +    struct fuse_session *se = vud->se;
> +
> +    if ((1 << VIRTIO_FS_F_NOTIFICATION) & features) {

For consistency 1ull should be used.  That way the reader does not have
to check the bit position to verify that the bitmap isn't truncated at
32 bits.

> +        vud->notify_enabled = true;
> +        se->notify_enabled = true;

Only one copy of this field is needed.  vud has a pointer to se.

> +    }
>  }
>  
>  /*
> @@ -662,6 +671,65 @@ static void fv_queue_worker(gpointer data, gpointer user_data)
>      free(req);
>  }
>  
> +static void *fv_queue_notify_thread(void *opaque)
> +{
> +    struct fv_QueueInfo *qi = opaque;
> +
> +    fuse_log(FUSE_LOG_INFO, "%s: Start for queue %d kick_fd %d\n", __func__,
> +             qi->qidx, qi->kick_fd);
> +
> +    while (1) {
> +        struct pollfd pf[2];
> +
> +        pf[0].fd = qi->kick_fd;
> +        pf[0].events = POLLIN;
> +        pf[0].revents = 0;
> +        pf[1].fd = qi->kill_fd;
> +        pf[1].events = POLLIN;
> +        pf[1].revents = 0;
> +
> +        fuse_log(FUSE_LOG_DEBUG, "%s: Waiting for Queue %d event\n", __func__,
> +                 qi->qidx);
> +        int poll_res = ppoll(pf, 2, NULL, NULL);
> +
> +        if (poll_res == -1) {
> +            if (errno == EINTR) {
> +                fuse_log(FUSE_LOG_INFO, "%s: ppoll interrupted, going around\n",
> +                         __func__);
> +                continue;
> +            }
> +            fuse_log(FUSE_LOG_ERR, "fv_queue_thread ppoll: %m\n");
> +            break;
> +        }
> +        assert(poll_res >= 1);
> +        if (pf[0].revents & (POLLERR | POLLHUP | POLLNVAL)) {
> +            fuse_log(FUSE_LOG_ERR, "%s: Unexpected poll revents %x Queue %d\n",
> +                     __func__, pf[0].revents, qi->qidx);
> +             break;
> +        }
> +        if (pf[1].revents & (POLLERR | POLLHUP | POLLNVAL)) {
> +            fuse_log(FUSE_LOG_ERR, "%s: Unexpected poll revents %x Queue %d"
> +                     "killfd\n", __func__, pf[1].revents, qi->qidx);
> +            break;
> +        }
> +        if (pf[1].revents) {
> +            fuse_log(FUSE_LOG_INFO, "%s: kill event on queue %d - quitting\n",
> +                     __func__, qi->qidx);
> +            break;
> +        }
> +        assert(pf[0].revents & POLLIN);
> +        fuse_log(FUSE_LOG_DEBUG, "%s: Got queue event on Queue %d\n", __func__,
> +                 qi->qidx);
> +
> +        eventfd_t evalue;
> +        if (eventfd_read(qi->kick_fd, &evalue)) {
> +            fuse_log(FUSE_LOG_ERR, "Eventfd_read for queue: %m\n");
> +            break;
> +        }
> +    }
> +    return NULL;
> +}

It's difficult to review function without any actual functionality using
the virtqueue.  I'm not sure a thread is even needed since the device
only needs to get a buffer when it has a notification for the driver.
I'll have to wait for the following patches to see what happens here...

> @@ -378,12 +382,23 @@ static void vuf_set_status(VirtIODevice *vdev, uint8_t status)
>      }
>  }
>  
> -static uint64_t vuf_get_features(VirtIODevice *vdev,
> -                                      uint64_t requested_features,
> -                                      Error **errp)
> +static uint64_t vuf_get_features(VirtIODevice *vdev, uint64_t features,
> +                                 Error **errp)
>  {
> -    /* No feature bits used yet */
> -    return requested_features;
> +    VHostUserFS *fs = VHOST_USER_FS(vdev);
> +
> +    virtio_add_feature(&features, VIRTIO_FS_F_NOTIFICATION);
> +
> +    return vhost_get_features(&fs->vhost_dev, user_feature_bits, features);
> +}
> +
> +static void vuf_set_features(VirtIODevice *vdev, uint64_t features)
> +{
> +    VHostUserFS *fs = VHOST_USER_FS(vdev);
> +
> +    if (virtio_has_feature(features, VIRTIO_FS_F_NOTIFICATION)) {
> +        fs->notify_enabled = true;

This field is unused, please remove it.