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Date: Wed, 02 May 2012 20:39:01 -0700 From: Alexander Duyck <alexander.h.duyck@...el.com> To: netdev@...r.kernel.org Cc: davem@...emloft.net, Alexander Duyck <alexander.h.duyck@...el.com>, Eric Dumazet <edumazet@...gle.com>, Jeff Kirsher <jeffrey.t.kirsher@...el.com> Subject: [PATCH 2/2] tcp: cleanup tcp_try_coalesce This change is mostly meant to help improve the readability of tcp_try_coalesce. I had a few issues since there were several points when the code would test for a conditional, fail, then succeed on another conditional take some action, and then follow a goto back into the previous conditional. I just tore all of that apart and made the whole thing one linear flow with a single goto. Also there were multiple ways of computing the delta, the one for head_frag made the least amount of sense to me since we were only dropping the sk_buff so I have updated the logic for the stolen head case so that delta is only truesize - sizeof(skb_buff), and for the case where we are dropping the head as well it is truesize - SKB_TRUESIZE(skb_end_pointer - head). This way we can also account for the head_frag with headlen == 0. Signed-off-by: Alexander Duyck <alexander.h.duyck@...el.com> Cc: Eric Dumazet <edumazet@...gle.com> Cc: Jeff Kirsher <jeffrey.t.kirsher@...el.com> --- net/ipv4/tcp_input.c | 80 +++++++++++++++++++++++++++----------------------- 1 files changed, 43 insertions(+), 37 deletions(-) diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index c6f78e2..23bc3ff 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -4548,62 +4548,68 @@ static bool tcp_try_coalesce(struct sock *sk, int i, delta, len = from->len; *fragstolen = false; + if (tcp_hdr(from)->fin || skb_cloned(to)) return false; + if (len <= skb_tailroom(to)) { BUG_ON(skb_copy_bits(from, 0, skb_put(to, len), len)); -merge: - NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPRCVCOALESCE); - TCP_SKB_CB(to)->end_seq = TCP_SKB_CB(from)->end_seq; - TCP_SKB_CB(to)->ack_seq = TCP_SKB_CB(from)->ack_seq; - return true; + goto merge; } if (skb_has_frag_list(to) || skb_has_frag_list(from)) return false; - if (skb_headlen(from) == 0 && - (skb_shinfo(to)->nr_frags + - skb_shinfo(from)->nr_frags <= MAX_SKB_FRAGS)) { - WARN_ON_ONCE(from->head_frag); - delta = from->truesize - ksize(from->head) - - SKB_DATA_ALIGN(sizeof(struct sk_buff)); - - WARN_ON_ONCE(delta < len); -copyfrags: - memcpy(skb_shinfo(to)->frags + skb_shinfo(to)->nr_frags, - skb_shinfo(from)->frags, - skb_shinfo(from)->nr_frags * sizeof(skb_frag_t)); - skb_shinfo(to)->nr_frags += skb_shinfo(from)->nr_frags; - - if (skb_cloned(from)) - for (i = 0; i < skb_shinfo(from)->nr_frags; i++) - skb_frag_ref(from, i); - else - skb_shinfo(from)->nr_frags = 0; - - to->truesize += delta; - atomic_add(delta, &sk->sk_rmem_alloc); - sk_mem_charge(sk, delta); - to->len += len; - to->data_len += len; - goto merge; - } - if (from->head_frag && !skb_cloned(from)) { + if (skb_headlen(from) != 0) { struct page *page; unsigned int offset; - if (skb_shinfo(to)->nr_frags + skb_shinfo(from)->nr_frags >= MAX_SKB_FRAGS) + if (skb_shinfo(to)->nr_frags + + skb_shinfo(from)->nr_frags >= MAX_SKB_FRAGS) + return false; + + if (!from->head_frag || skb_cloned(from)) return false; + + delta = from->truesize - sizeof(struct sk_buff); + page = virt_to_head_page(from->head); offset = from->data - (unsigned char *)page_address(page); + skb_fill_page_desc(to, skb_shinfo(to)->nr_frags, page, offset, skb_headlen(from)); *fragstolen = true; - delta = len; /* we dont know real truesize... */ - goto copyfrags; + } else { + if (skb_shinfo(to)->nr_frags + + skb_shinfo(from)->nr_frags > MAX_SKB_FRAGS) + return false; + + delta = from->truesize - + SKB_TRUESIZE(skb_end_pointer(from) - from->head); } - return false; + + memcpy(skb_shinfo(to)->frags + skb_shinfo(to)->nr_frags, + skb_shinfo(from)->frags, + skb_shinfo(from)->nr_frags * sizeof(skb_frag_t)); + skb_shinfo(to)->nr_frags += skb_shinfo(from)->nr_frags; + + if (!skb_cloned(from)) + skb_shinfo(from)->nr_frags = 0; + + for (i = 0; i < skb_shinfo(from)->nr_frags; i++) + skb_frag_ref(from, i); + + to->truesize += delta; + atomic_add(delta, &sk->sk_rmem_alloc); + sk_mem_charge(sk, delta); + to->len += len; + to->data_len += len; + +merge: + NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPRCVCOALESCE); + TCP_SKB_CB(to)->end_seq = TCP_SKB_CB(from)->end_seq; + TCP_SKB_CB(to)->ack_seq = TCP_SKB_CB(from)->ack_seq; + return true; } static void kfree_skb_partial(struct sk_buff *skb, bool head_stolen) -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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