From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: Re: [PATCH 1/2 v2] af-packet: Use existing netdev reference for bound sockets. Date: Fri, 27 May 2011 05:42:25 +0200 Message-ID: <1306467745.2543.60.camel@edumazet-laptop> References: <1306454141-1634-1-git-send-email-greearb@candelatech.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: netdev@vger.kernel.org To: greearb@candelatech.com Return-path: Received: from mail-wy0-f174.google.com ([74.125.82.174]:36688 "EHLO mail-wy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753731Ab1E0Dma (ORCPT ); Thu, 26 May 2011 23:42:30 -0400 Received: by wya21 with SMTP id 21so951642wya.19 for ; Thu, 26 May 2011 20:42:29 -0700 (PDT) In-Reply-To: <1306454141-1634-1-git-send-email-greearb@candelatech.com> Sender: netdev-owner@vger.kernel.org List-ID: Le jeudi 26 mai 2011 =C3=A0 16:55 -0700, greearb@candelatech.com a =C3=A9= crit : > From: Ben Greear >=20 > This saves a network device lookup on each packet transmitted, > for sockets that are bound to a network device. >=20 > Signed-off-by: Ben Greear > --- >=20 > v2: Remove un-used ifindex, lookup dev in else branch. >=20 > :100644 100644 4005b24... f9b807d... M net/packet/af_packet.c > net/packet/af_packet.c | 27 +++++++++++++++------------ > 1 files changed, 15 insertions(+), 12 deletions(-) >=20 > diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c > index 4005b24..f9b807d 100644 > --- a/net/packet/af_packet.c > +++ b/net/packet/af_packet.c > @@ -989,7 +989,8 @@ static int tpacket_snd(struct packet_sock *po, st= ruct msghdr *msg) > struct sk_buff *skb; > struct net_device *dev; > __be16 proto; > - int ifindex, err, reserve =3D 0; > + bool need_rls_dev =3D false; > + int err, reserve =3D 0; > void *ph; > struct sockaddr_ll *saddr =3D (struct sockaddr_ll *)msg->msg_name; > int tp_len, size_max; > @@ -1001,7 +1002,7 @@ static int tpacket_snd(struct packet_sock *po, = struct msghdr *msg) > =20 > err =3D -EBUSY; > if (saddr =3D=3D NULL) { > - ifindex =3D po->ifindex; > + dev =3D po->prot_hook.dev; > proto =3D po->num; > addr =3D NULL; > } else { > @@ -1012,12 +1013,12 @@ static int tpacket_snd(struct packet_sock *po= , struct msghdr *msg) > + offsetof(struct sockaddr_ll, > sll_addr))) > goto out; > - ifindex =3D saddr->sll_ifindex; > proto =3D saddr->sll_protocol; > addr =3D saddr->sll_addr; > + dev =3D dev_get_by_index(sock_net(&po->sk), saddr->sll_ifindex); > + need_rls_dev =3D true; > } > =20 > - dev =3D dev_get_by_index(sock_net(&po->sk), ifindex); > err =3D -ENXIO; > if (unlikely(dev =3D=3D NULL)) > goto out; > @@ -1103,7 +1104,8 @@ out_status: > __packet_set_status(po, ph, status); > kfree_skb(skb); > out_put: > - dev_put(dev); > + if (need_rls_dev) > + dev_put(dev); > out: > mutex_unlock(&po->pg_vec_lock); > return err; > @@ -1141,8 +1143,9 @@ static int packet_snd(struct socket *sock, > struct sk_buff *skb; > struct net_device *dev; > __be16 proto; > + bool need_rls_dev =3D false; > unsigned char *addr; > - int ifindex, err, reserve =3D 0; > + int err, reserve =3D 0; > struct virtio_net_hdr vnet_hdr =3D { 0 }; > int offset =3D 0; > int vnet_hdr_len; > @@ -1160,7 +1163,7 @@ static int packet_snd(struct socket *sock, > */ > =20 > if (saddr =3D=3D NULL) { > - ifindex =3D po->ifindex; > + dev =3D po->prot_hook.dev; > proto =3D po->num; > addr =3D NULL; > } else { > @@ -1169,13 +1172,12 @@ static int packet_snd(struct socket *sock, > goto out; > if (msg->msg_namelen < (saddr->sll_halen + offsetof(struct sockadd= r_ll, sll_addr))) > goto out; > - ifindex =3D saddr->sll_ifindex; > proto =3D saddr->sll_protocol; > addr =3D saddr->sll_addr; > + dev =3D dev_get_by_index(sock_net(sk), saddr->sll_ifindex); > + need_rls_dev =3D true; > } > =20 > - > - dev =3D dev_get_by_index(sock_net(sk), ifindex); > err =3D -ENXIO; > if (dev =3D=3D NULL) > goto out_unlock; > @@ -1315,14 +1317,15 @@ static int packet_snd(struct socket *sock, > if (err > 0 && (err =3D net_xmit_errno(err)) !=3D 0) > goto out_unlock; > =20 > - dev_put(dev); > + if (need_rls_dev) > + dev_put(dev); > =20 > return len; > =20 > out_free: > kfree_skb(skb); > out_unlock: > - if (dev) > + if (dev && need_rls_dev) > dev_put(dev); > out: > return err; Hmmm, I wonder why you want this Ben. IMHO this is buggy, because we can sleep in this function. We must take a ref on device (its really cheap these days, now we have = a percpu device refcnt)