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Date: Sat, 17 Sep 2016 13:35:38 -0400 From: Neal Cardwell <ncardwell@...gle.com> To: David Miller <davem@...emloft.net> Cc: netdev@...r.kernel.org, Eric Dumazet <edumazet@...gle.com>, Soheil Hassas Yeganeh <soheil@...gle.com>, Neal Cardwell <ncardwell@...gle.com>, Yuchung Cheng <ycheng@...gle.com> Subject: [PATCH v2 net-next 05/16] tcp: switch back to proper tcp_skb_cb size check in tcp_init() From: Eric Dumazet <edumazet@...gle.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@...gle.com> Signed-off-by: Soheil Hassas Yeganeh <soheil@...gle.com> Signed-off-by: Neal Cardwell <ncardwell@...gle.com> Signed-off-by: Yuchung Cheng <ycheng@...gle.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)); percpu_counter_init(&tcp_sockets_allocated, 0, GFP_KERNEL); percpu_counter_init(&tcp_orphan_count, 0, GFP_KERNEL); -- 2.8.0.rc3.226.g39d4020
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