packet: less dev_put() calls

- packet_sendmsg_spkt() can use dev_get_by_name_rcu() to avoid touching device refcount.

- packet_getname_spkt() & packet_getname() can use dev_get_by_index_rcu() to
  avoid touching device refcount too.

tpacket_snd() & packet_snd() can not use RCU yet because they can sleep when
allocating skb.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 12 insertions, 10 deletions

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 95ef64e4189a..91d246d34780 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -437,7 +437,8 @@ static int packet_sendmsg_spkt(struct kiocb *iocb, struct socket *sock,
          */
 
         saddr->spkt_device[13] = 0;
-        dev = dev_get_by_name(sock_net(sk), saddr->spkt_device);
+        rcu_read_lock();
+        dev = dev_get_by_name_rcu(sock_net(sk), saddr->spkt_device);
         err = -ENODEV;
         if (dev == NULL)
                 goto out_unlock;
@@ -500,14 +501,13 @@ static int packet_sendmsg_spkt(struct kiocb *iocb, struct socket *sock,
          */
 
         dev_queue_xmit(skb);
-        dev_put(dev);
+        rcu_read_unlock();
         return len;
 
 out_free:
         kfree_skb(skb);
 out_unlock:
-        if (dev)
-                dev_put(dev);
+        rcu_read_unlock();
         return err;
 }
 
@@ -1518,12 +1518,13 @@ static int packet_getname_spkt(struct socket *sock, struct sockaddr *uaddr,
                 return -EOPNOTSUPP;
 
         uaddr->sa_family = AF_PACKET;
-        dev = dev_get_by_index(sock_net(sk), pkt_sk(sk)->ifindex);
-        if (dev) {
+        rcu_read_lock();
+        dev = dev_get_by_index_rcu(sock_net(sk), pkt_sk(sk)->ifindex);
+        if (dev)
                 strlcpy(uaddr->sa_data, dev->name, 15);
-                dev_put(dev);
-        } else
+        else
                 memset(uaddr->sa_data, 0, 14);
+        rcu_read_unlock();
         *uaddr_len = sizeof(*uaddr);
 
         return 0;
@@ -1543,16 +1544,17 @@ static int packet_getname(struct socket *sock, struct sockaddr *uaddr,
         sll->sll_family = AF_PACKET;
         sll->sll_ifindex = po->ifindex;
         sll->sll_protocol = po->num;
-        dev = dev_get_by_index(sock_net(sk), po->ifindex);
+        rcu_read_lock();
+        dev = dev_get_by_index_rcu(sock_net(sk), po->ifindex);
         if (dev) {
                 sll->sll_hatype = dev->type;
                 sll->sll_halen = dev->addr_len;
                 memcpy(sll->sll_addr, dev->dev_addr, dev->addr_len);
-                dev_put(dev);
         } else {
                 sll->sll_hatype = 0;    /* Bad: we have no ARPHRD_UNSPEC */
                 sll->sll_halen = 0;
         }
+        rcu_read_unlock();
         *uaddr_len = offsetof(struct sockaddr_ll, sll_addr) + sll->sll_halen;
 
         return 0;