From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alexander Duyck Subject: [PATCH 1/2] net: Stop decapitating clones that have a head_frag Date: Wed, 02 May 2012 20:38:56 -0700 Message-ID: <20120503033856.5482.70122.stgit@gitlad.jf.intel.com> References: <20120503033018.5482.89902.stgit@gitlad.jf.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Cc: davem@davemloft.net, Alexander Duyck , Eric Dumazet , Jeff Kirsher To: netdev@vger.kernel.org Return-path: Received: from mga09.intel.com ([134.134.136.24]:58896 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753137Ab2ECDim (ORCPT ); Wed, 2 May 2012 23:38:42 -0400 In-Reply-To: <20120503033018.5482.89902.stgit@gitlad.jf.intel.com> Sender: netdev-owner@vger.kernel.org List-ID: This change is meant ot prevent stealing the skb->head to use as a page in the event that the skb->head was cloned. This allows the other clones to track each other via shinfo->dataref. Without this we break down to two methods for tracking the reference count, one being dataref, the other being the page count. As a result it becomes difficult to track how many references there are to skb->head. Signed-off-by: Alexander Duyck Cc: Eric Dumazet Cc: Jeff Kirsher --- net/core/skbuff.c | 2 +- net/ipv4/tcp_input.c | 9 ++------- 2 files changed, 3 insertions(+), 8 deletions(-) diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 52ba2b5..8703754 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -1699,7 +1699,7 @@ static bool __skb_splice_bits(struct sk_buff *skb, struct pipe_inode_info *pipe, struct splice_pipe_desc *spd, struct sock *sk) { int seg; - bool head_is_linear = !skb->head_frag; + bool head_is_linear = !skb->head_frag || skb_cloned(skb); /* map the linear part : * If skb->head_frag is set, this 'linear' part is backed diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 2f696ef..c6f78e2 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -4589,7 +4589,7 @@ copyfrags: to->data_len += len; goto merge; } - if (from->head_frag) { + if (from->head_frag && !skb_cloned(from)) { struct page *page; unsigned int offset; @@ -4599,12 +4599,7 @@ copyfrags: offset = from->data - (unsigned char *)page_address(page); skb_fill_page_desc(to, skb_shinfo(to)->nr_frags, page, offset, skb_headlen(from)); - - if (skb_cloned(from)) - get_page(page); - else - *fragstolen = true; - + *fragstolen = true; delta = len; /* we dont know real truesize... */ goto copyfrags; }