From: Alexander Duyck Date: Wed, 2 May 2012 21:18:59 +0000 (+0000) Subject: tcp: Fix truesize accounting in tcp_try_coalesce X-Git-Tag: v3.5-rc1~109^2~186 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=c73c3d9c49daae8acbac4cd14bcd81626887c0e6;p=platform%2Fkernel%2Flinux-3.10.git tcp: Fix truesize accounting in tcp_try_coalesce This patch addresses several issues in the way we were tracking the truesize in tcp_try_coalesce. First it was using ksize which prevents us from having a 0 sized head frag and getting a usable result. To resolve that this patch uses the end pointer which is set based off either ksize, or the frag_size supplied in build_skb. This allows us to compute the original truesize of the entire buffer and remove that value leaving us with just what was added as pages. The second issue was the use of skb->len if there is a mergeable head frag. We should only need to remove the size of an data aligned sk_buff from our current skb->truesize to compute the delta for a buffer with a reused head. By using skb->len the value of truesize was being artificially reduced which means that head frags could use more memory than buffers using standard allocations. Signed-off-by: Alexander Duyck Cc: Eric Dumazet Cc: Jeff Kirsher Acked-by: Eric Dumazet Signed-off-by: David S. Miller --- diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index c6f78e2..3cb273a 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -4565,12 +4565,10 @@ merge: 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); + delta = from->truesize - + SKB_TRUESIZE(skb_end_pointer(from) - from->head); copyfrags: + WARN_ON_ONCE(delta < len); memcpy(skb_shinfo(to)->frags + skb_shinfo(to)->nr_frags, skb_shinfo(from)->frags, skb_shinfo(from)->nr_frags * sizeof(skb_frag_t)); @@ -4600,7 +4598,7 @@ copyfrags: skb_fill_page_desc(to, skb_shinfo(to)->nr_frags, page, offset, skb_headlen(from)); *fragstolen = true; - delta = len; /* we dont know real truesize... */ + delta = from->truesize - SKB_DATA_ALIGN(sizeof(struct sk_buff)); goto copyfrags; } return false;