Re: [PATCH 10/16] virtio_net: use virtqueue_add_sgs[] for command buffers.

It's a bit cleaner to hand multiple sgs, rather than one big one.

Signed-off-by: Rusty Russell <redacted>
---
 drivers/net/virtio_net.c |   50 ++++++++++++++++++++++------------------------
 1 file changed, 24 insertions(+), 26 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 8ca69c0..63ac5c1 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c

@@ -39,7 +39,6 @@ module_param(gso, bool, 0444);
 #define MAX_PACKET_LEN (ETH_HLEN + VLAN_HLEN + ETH_DATA_LEN)
 #define GOOD_COPY_LEN	128
 
-#define VIRTNET_SEND_COMMAND_SG_MAX    2
 #define VIRTNET_DRIVER_VERSION "1.0.0"
 
 struct virtnet_stats {

@@ -831,32 +830,32 @@ static void virtnet_netpoll(struct net_device *dev)
  * never fail unless improperly formated.
  */
 static bool virtnet_send_command(struct virtnet_info *vi, u8 class, u8 cmd,
-				 struct scatterlist *data, int out, int in)
+				 struct scatterlist *out,
+				 struct scatterlist *in)
 {
-	struct scatterlist *s, sg[VIRTNET_SEND_COMMAND_SG_MAX + 2];
+	struct scatterlist *sgs[4], hdr, stat;
 	struct virtio_net_ctrl_hdr ctrl;
 	virtio_net_ctrl_ack status = ~0;
-	unsigned int tmp;
-	int i;
+	unsigned out_num = 0, in_num = 0, tmp;
 
 	/* Caller should know better */
-	BUG_ON(!virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_VQ) ||
-		(out + in > VIRTNET_SEND_COMMAND_SG_MAX));
-
-	out++; /* Add header */
-	in++; /* Add return status */
+	BUG_ON(!virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_VQ));
 
-	ctrl.class = class;
-	ctrl.cmd = cmd;

+	/* Add header */
+	sg_init_one(&hdr, &ctrl, sizeof(ctrl));
+	sgs[out_num++] = &hdr;
 
-	sg_init_table(sg, out + in);
+	if (out)
+		sgs[out_num++] = out;
+	if (in)
+		sgs[out_num + in_num++] = in;
 
-	sg_set_buf(&sg[0], &ctrl, sizeof(ctrl));
-	for_each_sg(data, s, out + in - 2, i)
-		sg_set_buf(&sg[i + 1], sg_virt(s), s->length);
-	sg_set_buf(&sg[out + in - 1], &status, sizeof(status));
+	/* Add return status. */
+	sg_init_one(&stat, &status, sizeof(status));
+	sgs[out_num + in_num++] = &hdr;
 
-	BUG_ON(virtqueue_add_buf(vi->cvq, sg, out, in, vi, GFP_ATOMIC) < 0);
+	BUG_ON(virtqueue_add_sgs(vi->cvq, sgs, out_num, in_num, vi, GFP_ATOMIC)
+	       < 0);
 
 	virtqueue_kick(vi->cvq);
 

@@ -874,8 +873,7 @@ static void virtnet_ack_link_announce(struct virtnet_info *vi)
 {
 	rtnl_lock();
 	if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_ANNOUNCE,
-				  VIRTIO_NET_CTRL_ANNOUNCE_ACK, NULL,
-				  0, 0))
+				  VIRTIO_NET_CTRL_ANNOUNCE_ACK, NULL, NULL))
 		dev_warn(&vi->dev->dev, "Failed to ack link announce.\n");
 	rtnl_unlock();
 }

@@ -893,7 +891,7 @@ static int virtnet_set_queues(struct virtnet_info *vi, u16 queue_pairs)
 	sg_init_one(&sg, &s, sizeof(s));
 
 	if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_MQ,
-				  VIRTIO_NET_CTRL_MQ_VQ_PAIRS_SET, &sg, 1, 0)){
+				  VIRTIO_NET_CTRL_MQ_VQ_PAIRS_SET, &sg, NULL)) {
 		dev_warn(&dev->dev, "Fail to set num of queue pairs to %d\n",
 			 queue_pairs);
 		return -EINVAL;

@@ -940,7 +938,7 @@ static void virtnet_set_rx_mode(struct net_device *dev)
 
 	if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_RX,
 				  VIRTIO_NET_CTRL_RX_PROMISC,
-				  sg, 1, 0))
+				  sg, NULL))
 		dev_warn(&dev->dev, "Failed to %sable promisc mode.\n",
 			 promisc ? "en" : "dis");
 

@@ -948,7 +946,7 @@ static void virtnet_set_rx_mode(struct net_device *dev)
 
 	if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_RX,
 				  VIRTIO_NET_CTRL_RX_ALLMULTI,
-				  sg, 1, 0))
+				  sg, NULL))
 		dev_warn(&dev->dev, "Failed to %sable allmulti mode.\n",
 			 allmulti ? "en" : "dis");
 

@@ -987,7 +985,7 @@ static void virtnet_set_rx_mode(struct net_device *dev)
 
 	if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_MAC,
 				  VIRTIO_NET_CTRL_MAC_TABLE_SET,
-				  sg, 2, 0))
+				  sg, NULL))
 		dev_warn(&dev->dev, "Failed to set MAC fitler table.\n");
 
 	kfree(buf);

@@ -1001,7 +999,7 @@ static int virtnet_vlan_rx_add_vid(struct net_device *dev, u16 vid)
 	sg_init_one(&sg, &vid, sizeof(vid));
 
 	if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_VLAN,
-				  VIRTIO_NET_CTRL_VLAN_ADD, &sg, 1, 0))
+				  VIRTIO_NET_CTRL_VLAN_ADD, &sg, NULL))
 		dev_warn(&dev->dev, "Failed to add VLAN ID %d.\n", vid);
 	return 0;
 }

@@ -1014,7 +1012,7 @@ static int virtnet_vlan_rx_kill_vid(struct net_device *dev, u16 vid)
 	sg_init_one(&sg, &vid, sizeof(vid));
 
 	if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_VLAN,
-				  VIRTIO_NET_CTRL_VLAN_DEL, &sg, 1, 0))
+				  VIRTIO_NET_CTRL_VLAN_DEL, &sg, NULL))
 		dev_warn(&dev->dev, "Failed to kill VLAN ID %d.\n", vid);
 	return 0;
 }