net/9p: Add waitq to VirtIO transport.

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@linux.vnet.ibm.com>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>

diff --git a/net/9p/client.c b/net/9p/client.c
index 2bc99e9..bc7b035 100644 (file)
--- a/net/9p/client.c
+++ b/net/9p/client.c
@@ -583,7 +583,8 @@ p9_client_rpc(struct p9_client *c, int8_t type, const char *fmt, ...)
 
        err = c->trans_mod->request(c, req);
        if (err < 0) {
-               c->status = Disconnected;
+               if (err != -ERESTARTSYS)
+                       c->status = Disconnected;
                goto reterr;
        }
 

diff --git a/net/9p/trans_virtio.c b/net/9p/trans_virtio.c
index 8ae0859..c8f3f72 100644 (file)
--- 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 +231,23 @@ 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(*chan->vc_wq,
+                                                       chan->ring_bufs_avail);
+                       if (err  == -ERESTARTSYS)
+                               return err;
+
+                       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;
+               }
        }
 
        virtqueue_kick(chan->vq);
@@ -304,14 +326,23 @@ static int p9_virtio_probe(struct virtio_device *vdev)
        chan->tag_len = tag_len;
        err = sysfs_create_file(&(vdev->dev.kobj), &dev_attr_mount_tag.attr);
        if (err) {
-               kfree(tag);
-               goto out_free_vq;
+               goto out_free_tag;
        }
+       chan->vc_wq = kmalloc(sizeof(wait_queue_head_t), GFP_KERNEL);
+       if (!chan->vc_wq) {
+               err = -ENOMEM;
+               goto out_free_tag;
+       }
+       init_waitqueue_head(chan->vc_wq);
+       chan->ring_bufs_avail = 1;
+
        mutex_lock(&virtio_9p_lock);
        list_add_tail(&chan->chan_list, &virtio_chan_list);
        mutex_unlock(&virtio_9p_lock);
        return 0;
 
+out_free_tag:
+       kfree(tag);
 out_free_vq:
        vdev->config->del_vqs(vdev);
        kfree(chan);
@@ -385,6 +416,7 @@ static void p9_virtio_remove(struct virtio_device *vdev)
        mutex_unlock(&virtio_9p_lock);
        sysfs_remove_file(&(vdev->dev.kobj), &dev_attr_mount_tag.attr);
        kfree(chan->tag);
+       kfree(chan->vc_wq);
        kfree(chan);
 
 }