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/trans_virtio.c b/net/9p/trans_virtio.c
index 8ae0859..c8f3f72 100644
--- a/net/9p/trans_virtio.c
+++ b/net/9p/trans_virtio.c
@@ -75,6 +75,8 @@
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 @@
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_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 @@
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 @@
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 @@
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);
}