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Message-ID: <20110917060249.32666.21024.stgit@dhcp-91-7.nay.redhat.com.englab.nay.redhat.com>
Date: Sat, 17 Sep 2011 14:02:49 +0800
From: Jason Wang <jasowang@...hat.com>
To: krkumar2@...ibm.com, eric.dumazet@...il.com, mst@...hat.com,
netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
virtualization@...ts.linux-foundation.org, davem@...emloft.net
Cc: kvm@...r.kernel.org, rusty@...tcorp.com.au, qemu-devel@...gnu.org,
mirq-linux@...e.qmqm.pl, joe@...ches.com, shemminger@...tta.com
Subject: [net-next RFC V2 PATCH 4/5] tuntap: multiqueue support
This patch adds multiqueue support for tap device by allowing multiple
sockets to be attached to a tap device. Then we could parallize packets
transmission/reception by put them into different socket.
Following steps were used when choose tx queues:
1 For the packets comes from multiqueue nics, we would just choose the
tx queue based on the which physical queue the packets comes from.
2 Otherwise we try to use rxhash to choose the queue.
3 If all above fails, we always use the first queue.
In order to let the tx path lockless, like macvtap, netif_tx_loch_bh()
isr eplaced by RCU and NETIF_F_LLTX to synchronize between hot path
and systemcall.
Signed-off-by: Jason Wang <jasowang@...hat.com>
---
drivers/net/tun.c | 358 +++++++++++++++++++++++++++++++++--------------------
1 files changed, 223 insertions(+), 135 deletions(-)
diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index dc768e0..ec29f85 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -108,6 +108,8 @@ struct tap_filter {
unsigned char addr[FLT_EXACT_COUNT][ETH_ALEN];
};
+#define MAX_TAP_QUEUES (NR_CPUS < 16 ? NR_CPUS : 16)
+
struct tun_file {
struct sock sk;
struct socket socket;
@@ -115,16 +117,18 @@ struct tun_file {
int vnet_hdr_sz;
struct tap_filter txflt;
atomic_t count;
- struct tun_struct *tun;
+ struct tun_struct __rcu *tun;
struct net *net;
struct fasync_struct *fasync;
unsigned int flags;
+ u16 queue_index;
};
struct tun_sock;
struct tun_struct {
- struct tun_file *tfile;
+ struct tun_file *tfiles[MAX_TAP_QUEUES];
+ unsigned int numqueues;
unsigned int flags;
uid_t owner;
gid_t group;
@@ -139,80 +143,160 @@ struct tun_struct {
#endif
};
-static int tun_attach(struct tun_struct *tun, struct file *file)
+static DEFINE_SPINLOCK(tun_lock);
+
+/*
+ * tun_get_queue(): calculate the queue index
+ * - if skbs comes from mq nics, we can just borrow
+ * - if not, calculate from the hash
+ */
+static struct tun_file *tun_get_queue(struct net_device *dev,
+ struct sk_buff *skb)
{
- struct tun_file *tfile = file->private_data;
- int err;
+ struct tun_struct *tun = netdev_priv(dev);
+ struct tun_file *tfile = NULL;
+ int numqueues = tun->numqueues;
+ __u32 rxq;
- ASSERT_RTNL();
+ BUG_ON(!rcu_read_lock_held());
- netif_tx_lock_bh(tun->dev);
+ if (!numqueues)
+ goto out;
- err = -EINVAL;
- if (tfile->tun)
+ if (numqueues == 1) {
+ tfile = rcu_dereference(tun->tfiles[0]);
goto out;
+ }
- err = -EBUSY;
- if (tun->tfile)
+ if (likely(skb_rx_queue_recorded(skb))) {
+ rxq = skb_get_rx_queue(skb);
+
+ while (unlikely(rxq >= numqueues))
+ rxq -= numqueues;
+
+ tfile = rcu_dereference(tun->tfiles[rxq]);
goto out;
+ }
- err = 0;
- tfile->tun = tun;
- tun->tfile = tfile;
- netif_carrier_on(tun->dev);
- dev_hold(tun->dev);
- sock_hold(&tfile->sk);
- atomic_inc(&tfile->count);
+ /* Check if we can use flow to select a queue */
+ rxq = skb_get_rxhash(skb);
+ if (rxq) {
+ u32 idx = ((u64)rxq * numqueues) >> 32;
+ tfile = rcu_dereference(tun->tfiles[idx]);
+ goto out;
+ }
+ tfile = rcu_dereference(tun->tfiles[0]);
out:
- netif_tx_unlock_bh(tun->dev);
- return err;
+ return tfile;
}
-static void __tun_detach(struct tun_struct *tun)
+static int tun_detach(struct tun_file *tfile, bool clean)
{
- struct tun_file *tfile = tun->tfile;
- /* Detach from net device */
- netif_tx_lock_bh(tun->dev);
- netif_carrier_off(tun->dev);
- tun->tfile = NULL;
- netif_tx_unlock_bh(tun->dev);
-
- /* Drop read queue */
- skb_queue_purge(&tfile->socket.sk->sk_receive_queue);
-
- /* Drop the extra count on the net device */
- dev_put(tun->dev);
-}
+ struct tun_struct *tun;
+ struct net_device *dev = NULL;
+ bool destroy = false;
-static void tun_detach(struct tun_struct *tun)
-{
- rtnl_lock();
- __tun_detach(tun);
- rtnl_unlock();
-}
+ spin_lock(&tun_lock);
-static struct tun_struct *__tun_get(struct tun_file *tfile)
-{
- struct tun_struct *tun = NULL;
+ tun = rcu_dereference_protected(tfile->tun,
+ lockdep_is_held(&tun_lock));
+ if (tun) {
+ u16 index = tfile->queue_index;
+ BUG_ON(index > tun->numqueues);
+ BUG_ON(!tun->tfiles[tun->numqueues - 1]);
+ dev = tun->dev;
+
+ rcu_assign_pointer(tun->tfiles[index],
+ tun->tfiles[tun->numqueues - 1]);
+ tun->tfiles[index]->queue_index = index;
+ rcu_assign_pointer(tfile->tun, NULL);
+ --tun->numqueues;
+ sock_put(&tfile->sk);
- if (atomic_inc_not_zero(&tfile->count))
- tun = tfile->tun;
+ if (tun->numqueues == 0 && !(tun->flags & TUN_PERSIST))
+ destroy = true;
+ }
+
+ spin_unlock(&tun_lock);
+
+ synchronize_rcu();
+ if (clean)
+ sock_put(&tfile->sk);
- return tun;
+ if (destroy) {
+ rtnl_lock();
+ if (dev->reg_state == NETREG_REGISTERED)
+ unregister_netdevice(dev);
+ rtnl_unlock();
+ }
+
+ return 0;
}
-static struct tun_struct *tun_get(struct file *file)
+static void tun_detach_all(struct net_device *dev)
{
- return __tun_get(file->private_data);
+ struct tun_struct *tun = netdev_priv(dev);
+ struct tun_file *tfile, *tfile_list[MAX_TAP_QUEUES];
+ int i, j = 0;
+
+ spin_lock(&tun_lock);
+
+ for (i = 0; i < MAX_TAP_QUEUES && tun->numqueues; i++) {
+ tfile = rcu_dereference_protected(tun->tfiles[i],
+ lockdep_is_held(&tun_lock));
+ BUG_ON(!tfile);
+ wake_up_all(&tfile->wq.wait);
+ tfile_list[j++] = tfile;
+ rcu_assign_pointer(tfile->tun, NULL);
+ --tun->numqueues;
+ }
+ BUG_ON(tun->numqueues != 0);
+ spin_unlock(&tun_lock);
+
+ synchronize_rcu();
+ for(--j; j >= 0; j--)
+ sock_put(&tfile_list[j]->sk);
}
-static void tun_put(struct tun_struct *tun)
+static int tun_attach(struct tun_struct *tun, struct file *file)
{
- struct tun_file *tfile = tun->tfile;
+ struct tun_file *tfile = file->private_data;
+ int err;
+
+ ASSERT_RTNL();
+
+ spin_lock(&tun_lock);
+
+ err = -EINVAL;
+ if (rcu_dereference_protected(tfile->tun, lockdep_is_held(&tun_lock)))
+ goto out;
+
+ err = -EBUSY;
+ if (!(tun->flags & TUN_TAP_MQ) &&
+ rcu_dereference_protected(tun->tfiles[0],
+ lockdep_is_held(&tun_lock))) {
+ /* Multiqueue is only for TAP */
+ goto out;
+ }
+
+ if (tun->numqueues == MAX_TAP_QUEUES)
+ goto out;
+
+ err = 0;
+ tfile->queue_index = tun->numqueues;
+ rcu_assign_pointer(tfile->tun, tun);
+ rcu_assign_pointer(tun->tfiles[tun->numqueues], tfile);
+ sock_hold(&tfile->sk);
+ tun->numqueues++;
+
+ if (tun->numqueues == 1)
+ netif_carrier_on(tun->dev);
- if (atomic_dec_and_test(&tfile->count))
- tun_detach(tfile->tun);
+ /* device is allowed to go away first, so no need to hold extra refcnt. */
+out:
+ spin_unlock(&tun_lock);
+ return err;
}
/* TAP filtering */
@@ -332,16 +416,7 @@ static const struct ethtool_ops tun_ethtool_ops;
/* Net device detach from fd. */
static void tun_net_uninit(struct net_device *dev)
{
- struct tun_struct *tun = netdev_priv(dev);
- struct tun_file *tfile = tun->tfile;
-
- /* Inform the methods they need to stop using the dev.
- */
- if (tfile) {
- wake_up_all(&tfile->wq.wait);
- if (atomic_dec_and_test(&tfile->count))
- __tun_detach(tun);
- }
+ tun_detach_all(dev);
}
/* Net device open. */
@@ -361,10 +436,10 @@ static int tun_net_close(struct net_device *dev)
/* Net device start xmit */
static netdev_tx_t tun_net_xmit(struct sk_buff *skb, struct net_device *dev)
{
- struct tun_struct *tun = netdev_priv(dev);
- struct tun_file *tfile = tun->tfile;
+ struct tun_file *tfile = NULL;
- tun_debug(KERN_INFO, tun, "tun_net_xmit %d\n", skb->len);
+ rcu_read_lock();
+ tfile = tun_get_queue(dev, skb);
/* Drop packet if interface is not attached */
if (!tfile)
@@ -381,7 +456,7 @@ static netdev_tx_t tun_net_xmit(struct sk_buff *skb, struct net_device *dev)
goto drop;
if (skb_queue_len(&tfile->socket.sk->sk_receive_queue) >= dev->tx_queue_len) {
- if (!(tun->flags & TUN_ONE_QUEUE)) {
+ if (!(tfile->flags & TUN_ONE_QUEUE) && !(tfile->flags && TUN_TAP_MQ)) {
/* Normal queueing mode. */
/* Packet scheduler handles dropping of further packets. */
netif_stop_queue(dev);
@@ -390,7 +465,7 @@ static netdev_tx_t tun_net_xmit(struct sk_buff *skb, struct net_device *dev)
* error is more appropriate. */
dev->stats.tx_fifo_errors++;
} else {
- /* Single queue mode.
+ /* Single queue mode or multi queue mode.
* Driver handles dropping of all packets itself. */
goto drop;
}
@@ -408,9 +483,11 @@ static netdev_tx_t tun_net_xmit(struct sk_buff *skb, struct net_device *dev)
kill_fasync(&tfile->fasync, SIGIO, POLL_IN);
wake_up_interruptible_poll(&tfile->wq.wait, POLLIN |
POLLRDNORM | POLLRDBAND);
+ rcu_read_unlock();
return NETDEV_TX_OK;
drop:
+ rcu_read_unlock();
dev->stats.tx_dropped++;
kfree_skb(skb);
return NETDEV_TX_OK;
@@ -526,16 +603,22 @@ static void tun_net_init(struct net_device *dev)
static unsigned int tun_chr_poll(struct file *file, poll_table * wait)
{
struct tun_file *tfile = file->private_data;
- struct tun_struct *tun = __tun_get(tfile);
+ struct tun_struct *tun = NULL;
struct sock *sk;
unsigned int mask = 0;
- if (!tun)
+ if (!tfile)
return POLLERR;
- sk = tfile->socket.sk;
+ rcu_read_lock();
+ tun = rcu_dereference(tfile->tun);
+ if (!tun) {
+ rcu_read_unlock();
+ return POLLERR;
+ }
+ rcu_read_unlock();
- tun_debug(KERN_INFO, tun, "tun_chr_poll\n");
+ sk = &tfile->sk;
poll_wait(file, &tfile->wq.wait, wait);
@@ -547,10 +630,12 @@ static unsigned int tun_chr_poll(struct file *file, poll_table * wait)
sock_writeable(sk)))
mask |= POLLOUT | POLLWRNORM;
- if (tun->dev->reg_state != NETREG_REGISTERED)
+ rcu_read_lock();
+ tun = rcu_dereference(tfile->tun);
+ if (!tun || tun->dev->reg_state != NETREG_REGISTERED)
mask = POLLERR;
+ rcu_read_unlock();
- tun_put(tun);
return mask;
}
@@ -706,11 +791,12 @@ static ssize_t tun_get_user(struct tun_file *tfile,
skb_shinfo(skb)->gso_segs = 0;
}
- tun = __tun_get(tfile);
+ rcu_read_lock();
+ tun = rcu_dereference(tfile->tun);
if (!tun) {
+ rcu_read_unlock();
return -EBADFD;
}
-
switch (tfile->flags & TUN_TYPE_MASK) {
case TUN_TUN_DEV:
skb->dev = tun->dev;
@@ -719,27 +805,29 @@ static ssize_t tun_get_user(struct tun_file *tfile,
skb->protocol = eth_type_trans(skb, tun->dev);
break;
}
-
- netif_rx_ni(skb);
tun->dev->stats.rx_packets++;
tun->dev->stats.rx_bytes += len;
- tun_put(tun);
+ rcu_read_unlock();
+
+ netif_rx_ni(skb);
+
return count;
err_free:
count = -EINVAL;
kfree_skb(skb);
err:
- tun = __tun_get(tfile);
+ rcu_read_lock();
+ tun = rcu_dereference(tfile->tun);
if (!tun) {
+ rcu_read_unlock();
return -EBADFD;
}
-
if (drop)
tun->dev->stats.rx_dropped++;
if (error)
tun->dev->stats.rx_frame_errors++;
- tun_put(tun);
+ rcu_read_unlock();
return count;
}
@@ -832,12 +920,13 @@ static ssize_t tun_put_user(struct tun_file *tfile,
skb_copy_datagram_const_iovec(skb, 0, iv, total, len);
total += skb->len;
- tun = __tun_get(tfile);
+ rcu_read_lock();
+ tun = rcu_dereference(tfile->tun);
if (tun) {
tun->dev->stats.tx_packets++;
tun->dev->stats.tx_bytes += len;
- tun_put(tun);
}
+ rcu_read_unlock();
return total;
}
@@ -867,28 +956,31 @@ static ssize_t tun_do_read(struct tun_file *tfile,
break;
}
- tun = __tun_get(tfile);
+ rcu_read_lock();
+ tun = rcu_dereference(tfile->tun);
if (!tun) {
- ret = -EIO;
+ ret = -EBADFD;
+ rcu_read_unlock();
break;
}
if (tun->dev->reg_state != NETREG_REGISTERED) {
ret = -EIO;
- tun_put(tun);
+ rcu_read_unlock();
break;
}
- tun_put(tun);
+ rcu_read_unlock();
/* Nothing to read, let's sleep */
schedule();
continue;
}
- tun = __tun_get(tfile);
+ rcu_read_lock();
+ tun = rcu_dereference(tfile->tun);
if (tun) {
netif_wake_queue(tun->dev);
- tun_put(tun);
}
+ rcu_read_unlock();
ret = tun_put_user(tfile, skb, iv, len);
kfree_skb(skb);
@@ -1028,6 +1120,9 @@ static int tun_flags(struct tun_struct *tun)
if (tun->flags & TUN_VNET_HDR)
flags |= IFF_VNET_HDR;
+ if (tun->flags & TUN_TAP_MQ)
+ flags |= IFF_MULTI_QUEUE;
+
return flags;
}
@@ -1107,6 +1202,10 @@ static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr)
/* TAP device */
flags |= TUN_TAP_DEV;
name = "tap%d";
+ if (ifr->ifr_flags & IFF_MULTI_QUEUE) {
+ flags |= TUN_TAP_MQ;
+ name = "mqtap%d";
+ }
} else
return -EINVAL;
@@ -1132,6 +1231,8 @@ static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr)
dev->hw_features = NETIF_F_SG | NETIF_F_FRAGLIST |
TUN_USER_FEATURES;
dev->features = dev->hw_features;
+ if (ifr->ifr_flags & IFF_MULTI_QUEUE)
+ dev->features |= NETIF_F_LLTX;
err = register_netdevice(tun->dev);
if (err < 0)
@@ -1164,6 +1265,11 @@ static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr)
else
tun->flags &= ~TUN_VNET_HDR;
+ if (ifr->ifr_flags & IFF_MULTI_QUEUE)
+ tun->flags |= TUN_TAP_MQ;
+ else
+ tun->flags &= ~TUN_TAP_MQ;
+
/* Cache flags from tun device */
tfile->flags = tun->flags;
/* Make sure persistent devices do not get stuck in
@@ -1254,38 +1360,39 @@ static long __tun_chr_ioctl(struct file *file, unsigned int cmd,
(unsigned int __user*)argp);
}
- rtnl_lock();
-
- tun = __tun_get(tfile);
- if (cmd == TUNSETIFF && !tun) {
+ ret = 0;
+ if (cmd == TUNSETIFF) {
+ rtnl_lock();
ifr.ifr_name[IFNAMSIZ-1] = '\0';
-
ret = tun_set_iff(tfile->net, file, &ifr);
-
+ rtnl_unlock();
if (ret)
- goto unlock;
-
+ return ret;
if (copy_to_user(argp, &ifr, ifreq_len))
- ret = -EFAULT;
- goto unlock;
+ return -EFAULT;
+ return ret;
}
+ rtnl_lock();
+
+ rcu_read_lock();
+
ret = -EBADFD;
+ tun = rcu_dereference(tfile->tun);
if (!tun)
goto unlock;
- tun_debug(KERN_INFO, tun, "tun_chr_ioctl cmd %d\n", cmd);
- ret = 0;
- switch (cmd) {
+ switch(cmd) {
case TUNGETIFF:
ret = tun_get_iff(current->nsproxy->net_ns, tun, &ifr);
+ rcu_read_unlock();
if (ret)
- break;
+ goto out;
if (copy_to_user(argp, &ifr, ifreq_len))
ret = -EFAULT;
- break;
+ goto out;
case TUNSETNOCSUM:
/* Disable/Enable checksum */
@@ -1347,9 +1454,10 @@ static long __tun_chr_ioctl(struct file *file, unsigned int cmd,
/* Get hw address */
memcpy(ifr.ifr_hwaddr.sa_data, tun->dev->dev_addr, ETH_ALEN);
ifr.ifr_hwaddr.sa_family = tun->dev->type;
+ rcu_read_unlock();
if (copy_to_user(argp, &ifr, ifreq_len))
ret = -EFAULT;
- break;
+ goto out;
case SIOCSIFHWADDR:
/* Set hw address */
@@ -1365,9 +1473,9 @@ static long __tun_chr_ioctl(struct file *file, unsigned int cmd,
}
unlock:
+ rcu_read_unlock();
+out:
rtnl_unlock();
- if (tun)
- tun_put(tun);
return ret;
}
@@ -1539,31 +1647,8 @@ static int tun_chr_open(struct inode *inode, struct file * file)
static int tun_chr_close(struct inode *inode, struct file *file)
{
struct tun_file *tfile = file->private_data;
- struct tun_struct *tun;
-
- tun = __tun_get(tfile);
- if (tun) {
- struct net_device *dev = tun->dev;
-
- tun_debug(KERN_INFO, tun, "tun_chr_close\n");
-
- __tun_detach(tun);
-
- /* If desirable, unregister the netdevice. */
- if (!(tun->flags & TUN_PERSIST)) {
- rtnl_lock();
- if (dev->reg_state == NETREG_REGISTERED)
- unregister_netdevice(dev);
- rtnl_unlock();
- }
-
- /* drop the reference that netdevice holds */
- sock_put(&tfile->sk);
-
- }
- /* drop the reference that file holds */
- sock_put(&tfile->sk);
+ tun_detach(tfile, true);
return 0;
}
@@ -1691,14 +1776,17 @@ static void tun_cleanup(void)
* holding a reference to the file for as long as the socket is in use. */
struct socket *tun_get_socket(struct file *file)
{
- struct tun_struct *tun;
+ struct tun_struct *tun = NULL;
struct tun_file *tfile = file->private_data;
if (file->f_op != &tun_fops)
return ERR_PTR(-EINVAL);
- tun = tun_get(file);
- if (!tun)
+ rcu_read_lock();
+ tun = rcu_dereference(tfile->tun);
+ if (!tun) {
+ rcu_read_unlock();
return ERR_PTR(-EBADFD);
- tun_put(tun);
+ }
+ rcu_read_unlock();
return &tfile->socket;
}
EXPORT_SYMBOL_GPL(tun_get_socket);
--
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