| Message ID | 1474236233-28511-6-git-send-email-ncardwell@google.com |
|---|---|
| State | Changes Requested, archived |
| Delegated to: | David Miller |
| Headers | show |
> From: "Neal Cardwell" <ncardwell@google.com> > To: "David Miller" <davem@davemloft.net> > Cc: netdev@vger.kernel.org, "Eric Dumazet" <edumazet@google.com>, "Soheil Hassas Yeganeh" <soheil@google.com>, "Neal > Cardwell" <ncardwell@google.com>, "Yuchung Cheng" <ycheng@google.com> > Sent: Sunday, September 18, 2016 6:03:42 PM > Subject: [PATCH v3 net-next 05/16] tcp: switch back to proper tcp_skb_cb size check in tcp_init() > > From: Eric Dumazet <edumazet@google.com> > > Revert to the tcp_skb_cb size check that tcp_init() had before commit > b4772ef879a8 ("net: use common macro for assering skb->cb[] available > size in protocol families"). As related commit 744d5a3e9fe2 ("net: > move skb->dropcount to skb->cb[]") explains, the > sock_skb_cb_check_size() mechanism was added to ensure that there is > space for dropcount, "for protocol families using it". But TCP is not > a protocol using dropcount, so tcp_init() doesn't need to provision > space for dropcount in the skb->cb[], and thus we can revert to the > older form of the tcp_skb_cb size check. Doing so allows TCP to use 4 > more bytes of the skb->cb[] space. > > Fixes: b4772ef879a8 ("net: use common macro for assering skb->cb[] available > size in protocol families") > Signed-off-by: Eric Dumazet <edumazet@google.com> > Signed-off-by: Soheil Hassas Yeganeh <soheil@google.com> > Signed-off-by: Neal Cardwell <ncardwell@google.com> > Signed-off-by: Yuchung Cheng <ycheng@google.com> > --- > net/ipv4/tcp.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c > index 5b0b49c..53798e1 100644 > --- a/net/ipv4/tcp.c > +++ b/net/ipv4/tcp.c > @@ -3244,11 +3244,12 @@ static void __init tcp_init_mem(void) > > void __init tcp_init(void) > { > - unsigned long limit; > int max_rshare, max_wshare, cnt; > + unsigned long limit; > + struct sk_buff *skb; > unsigned int i; > > - sock_skb_cb_check_size(sizeof(struct tcp_skb_cb)); > + BUILD_BUG_ON(sizeof(struct tcp_skb_cb) > sizeof(skb->cb)); > The skb local variable could be avoided via: BUILD_BUG_ON(sizeof(struct tcp_skb_cb) > FIELD_SIZEOF(struct sk_buff, cb)); > percpu_counter_init(&tcp_sockets_allocated, 0, GFP_KERNEL); > percpu_counter_init(&tcp_orphan_count, 0, GFP_KERNEL); > -- > 2.8.0.rc3.226.g39d4020 > >
On Mon, Sep 19, 2016 at 7:37 AM, Lance Richardson <lrichard@redhat.com> wrote: > The skb local variable could be avoided via: > > BUILD_BUG_ON(sizeof(struct tcp_skb_cb) > FIELD_SIZEOF(struct sk_buff, cb)); > Right you are, thanks !
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 5b0b49c..53798e1 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -3244,11 +3244,12 @@ static void __init tcp_init_mem(void) void __init tcp_init(void) { - unsigned long limit; int max_rshare, max_wshare, cnt; + unsigned long limit; + struct sk_buff *skb; unsigned int i; - sock_skb_cb_check_size(sizeof(struct tcp_skb_cb)); + BUILD_BUG_ON(sizeof(struct tcp_skb_cb) > sizeof(skb->cb)); percpu_counter_init(&tcp_sockets_allocated, 0, GFP_KERNEL); percpu_counter_init(&tcp_orphan_count, 0, GFP_KERNEL);