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Subject[PATCH 2/3] vhost-net: Unify the code of mergeable and big buffer handling
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Codes duplication were found between the handling of mergeable and big
buffers, so this patch tries to unify them. This could be easily done
by adding a quota to the get_rx_bufs() which is used to limit the
number of buffers it returns (for mergeable buffer, the quota is
simply UIO_MAXIOV, for big buffers, the quota is just 1), and then the
previous handle_rx_mergeable() could be resued also for big buffers.

Signed-off-by: Jason Wang <jasowang@redhat.com>
---
drivers/vhost/net.c | 128 +++------------------------------------------------
1 files changed, 7 insertions(+), 121 deletions(-)
diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 95e49de..c32a2e4 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -227,6 +227,7 @@ static int peek_head_len(struct sock *sk)
* @iovcount - returned count of io vectors we fill
* @log - vhost log
* @log_num - log offset
+ * @quota - headcount quota, 1 for big buffer
* returns number of buffer heads allocated, negative on error
*/
static int get_rx_bufs(struct vhost_virtqueue *vq,
@@ -234,7 +235,8 @@ static int get_rx_bufs(struct vhost_virtqueue *vq,
int datalen,
unsigned *iovcount,
struct vhost_log *log,
- unsigned *log_num)
+ unsigned *log_num,
+ unsigned int quota)
{
unsigned int out, in;
int seg = 0;
@@ -242,7 +244,7 @@ static int get_rx_bufs(struct vhost_virtqueue *vq,
unsigned d;
int r, nlogs = 0;

- while (datalen > 0) {
+ while (datalen > 0 && headcount < quota) {
if (unlikely(seg >= UIO_MAXIOV)) {
r = -ENOBUFS;
goto err;
@@ -282,116 +284,7 @@ err:

/* Expects to be always run from workqueue - which acts as
* read-size critical section for our kind of RCU. */
-static void handle_rx_big(struct vhost_net *net)
-{
- struct vhost_virtqueue *vq = &net->dev.vqs[VHOST_NET_VQ_RX];
- unsigned out, in, log, s;
- int head;
- struct vhost_log *vq_log;
- struct msghdr msg = {
- .msg_name = NULL,
- .msg_namelen = 0,
- .msg_control = NULL, /* FIXME: get and handle RX aux data. */
- .msg_controllen = 0,
- .msg_iov = vq->iov,
- .msg_flags = MSG_DONTWAIT,
- };
-
- struct virtio_net_hdr hdr = {
- .flags = 0,
- .gso_type = VIRTIO_NET_HDR_GSO_NONE
- };
-
- size_t len, total_len = 0;
- int err;
- size_t hdr_size;
- struct socket *sock = rcu_dereference(vq->private_data);
- if (!sock || skb_queue_empty(&sock->sk->sk_receive_queue))
- return;
-
- mutex_lock(&vq->mutex);
- vhost_disable_notify(vq);
- hdr_size = vq->vhost_hlen;
-
- vq_log = unlikely(vhost_has_feature(&net->dev, VHOST_F_LOG_ALL)) ?
- vq->log : NULL;
-
- for (;;) {
- head = vhost_get_vq_desc(&net->dev, vq, vq->iov,
- ARRAY_SIZE(vq->iov),
- &out, &in,
- vq_log, &log);
- /* On error, stop handling until the next kick. */
- if (unlikely(head < 0))
- break;
- /* OK, now we need to know about added descriptors. */
- if (head == vq->num) {
- if (unlikely(vhost_enable_notify(vq))) {
- /* They have slipped one in as we were
- * doing that: check again. */
- vhost_disable_notify(vq);
- continue;
- }
- /* Nothing new? Wait for eventfd to tell us
- * they refilled. */
- break;
- }
- /* We don't need to be notified again. */
- if (out) {
- vq_err(vq, "Unexpected descriptor format for RX: "
- "out %d, int %d\n",
- out, in);
- break;
- }
- /* Skip header. TODO: support TSO/mergeable rx buffers. */
- s = move_iovec_hdr(vq->iov, vq->hdr, hdr_size, in);
- msg.msg_iovlen = in;
- len = iov_length(vq->iov, in);
- /* Sanity check */
- if (!len) {
- vq_err(vq, "Unexpected header len for RX: "
- "%zd expected %zd\n",
- iov_length(vq->hdr, s), hdr_size);
- break;
- }
- err = sock->ops->recvmsg(NULL, sock, &msg,
- len, MSG_DONTWAIT | MSG_TRUNC);
- /* TODO: Check specific error and bomb out unless EAGAIN? */
- if (err < 0) {
- vhost_discard_vq_desc(vq, 1);
- break;
- }
- /* TODO: Should check and handle checksum. */
- if (err > len) {
- pr_debug("Discarded truncated rx packet: "
- " len %d > %zd\n", err, len);
- vhost_discard_vq_desc(vq, 1);
- continue;
- }
- len = err;
- err = memcpy_toiovec(vq->hdr, (unsigned char *)&hdr, hdr_size);
- if (err) {
- vq_err(vq, "Unable to write vnet_hdr at addr %p: %d\n",
- vq->iov->iov_base, err);
- break;
- }
- len += hdr_size;
- vhost_add_used_and_signal(&net->dev, vq, head, len);
- if (unlikely(vq_log))
- vhost_log_write(vq, vq_log, log, len);
- total_len += len;
- if (unlikely(total_len >= VHOST_NET_WEIGHT)) {
- vhost_poll_queue(&vq->poll);
- break;
- }
- }
-
- mutex_unlock(&vq->mutex);
-}
-
-/* Expects to be always run from workqueue - which acts as
- * read-size critical section for our kind of RCU. */
-static void handle_rx_mergeable(struct vhost_net *net)
+static void handle_rx(struct vhost_net *net)
{
struct vhost_virtqueue *vq = &net->dev.vqs[VHOST_NET_VQ_RX];
unsigned uninitialized_var(in), log;
@@ -431,7 +324,8 @@ static void handle_rx_mergeable(struct vhost_net *net)
sock_len += sock_hlen;
vhost_len = sock_len + vhost_hlen;
headcount = get_rx_bufs(vq, vq->heads, vhost_len,
- &in, vq_log, &log);
+ &in, vq_log, &log,
+ likely(mergeable) ? UIO_MAXIOV : 1);
/* On error, stop handling until the next kick. */
if (unlikely(headcount < 0))
break;
@@ -497,14 +391,6 @@ static void handle_rx_mergeable(struct vhost_net *net)
mutex_unlock(&vq->mutex);
}

-static void handle_rx(struct vhost_net *net)
-{
- if (vhost_has_feature(&net->dev, VIRTIO_NET_F_MRG_RXBUF))
- handle_rx_mergeable(net);
- else
- handle_rx_big(net);
-}
-
static void handle_tx_kick(struct vhost_work *work)
{
struct vhost_virtqueue *vq = container_of(work, struct vhost_virtqueue,


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