On Fri, 1 Oct 2010 16:56:17 -0700, "Venkateswararao Jujjuri (JV)" <jvrao@xxxxxxxxxxxxxxxxxx> wrote:
> If there is not enough space for the PDU on the VirtIO ring, current
> code returns -EIO propagating the error to user.
>
> This patch introduced a wqit_queue on the channel, and lets the process
> wait on this queue until VirtIO ring frees up.
>
> Signed-off-by: Venkateswararao Jujjuri <jvrao@xxxxxxxxxxxxxxxxxx>
> ---
> net/9p/trans_virtio.c | 44 +++++++++++++++++++++++++++++++++++++-------
> 1 files changed, 37 insertions(+), 7 deletions(-)
>
> diff --git a/net/9p/trans_virtio.c b/net/9p/trans_virtio.c
> index 0df84bf..2de5144 100644
> --- a/net/9p/trans_virtio.c
> +++ b/net/9p/trans_virtio.c
> @@ -75,6 +75,8 @@ struct virtio_chan {
> struct p9_client *client;
> struct virtio_device *vdev;
> struct virtqueue *vq;
> + int ring_bufs_avail;
> + wait_queue_head_t *vc_wq;
>
> /* Scatterlist: can be too big for stack. */
> struct scatterlist sg[VIRTQUEUE_NUM];
> @@ -141,15 +143,21 @@ static void req_done(struct virtqueue *vq)
> do {
> spin_lock_irqsave(&chan->lock, flags);
> rc = virtqueue_get_buf(chan->vq, &len);
> - spin_unlock_irqrestore(&chan->lock, flags);
>
> if (rc != NULL) {
> + if (!chan->ring_bufs_avail) {
> + chan->ring_bufs_avail = 1;
> + wake_up(chan->vc_wq);
> + }
> + spin_unlock_irqrestore(&chan->lock, flags);
> P9_DPRINTK(P9_DEBUG_TRANS, ": rc %p\n", rc);
> P9_DPRINTK(P9_DEBUG_TRANS, ": lookup tag %d\n",
> rc->tag);
> req = p9_tag_lookup(chan->client, rc->tag);
> req->status = REQ_STATUS_RCVD;
> p9_client_cb(chan->client, req);
> + } else {
> + spin_unlock_irqrestore(&chan->lock, flags);
> }
> } while (rc != NULL);
> }
> @@ -212,6 +220,7 @@ p9_virtio_request(struct p9_client *client, struct p9_req_t *req)
>
> P9_DPRINTK(P9_DEBUG_TRANS, "9p debug: virtio request\n");
>
> +req_retry:
> req->status = REQ_STATUS_SENT;
>
> spin_lock_irqsave(&chan->lock, flags);
> @@ -222,10 +231,21 @@ p9_virtio_request(struct p9_client *client, struct p9_req_t *req)
>
> err = virtqueue_add_buf(chan->vq, chan->sg, out, in, req->tc);
> if (err < 0) {
> - spin_unlock_irqrestore(&chan->lock, flags);
> - P9_DPRINTK(P9_DEBUG_TRANS,
> - "9p debug: virtio rpc add_buf returned failure");
> - return -EIO;
> + if (err == -ENOSPC) {
> + chan->ring_bufs_avail = 0;
> + spin_unlock_irqrestore(&chan->lock, flags);
> + err = wait_event_interruptible_timeout(*chan->vc_wq,
> + chan->ring_bufs_avail,
> + HZ/4);
Why do we need this to be _timeout ? Also if interrupted by a signal we do
want to return to user space with -EIO right ? Or we loop here always ?
> + P9_DPRINTK(P9_DEBUG_TRANS, "9p:Retry virtio request\n");
> + goto req_retry;
> + } else {
> + spin_unlock_irqrestore(&chan->lock, flags);
> + P9_DPRINTK(P9_DEBUG_TRANS,
> + "9p debug: "
> + "virtio rpc add_buf returned failure");
> + return -EIO;
> + }
> }
-aneesh
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