From c208bdb93788cfd7982c35480f98e75d658719a7 Mon Sep 17 00:00:00 2001 From: Soheil Hassas Yeganeh Date: Thu, 10 Oct 2019 23:27:02 -0400 Subject: [PATCH] tcp: improve recv_skip_hint for tcp_zerocopy_receive tcp_zerocopy_receive() rounds down the zc->length a multiple of PAGE_SIZE. This results in two issues: - tcp_zerocopy_receive sets recv_skip_hint to the length of the receive queue if the zc->length input is smaller than the PAGE_SIZE, even though the data in receive queue could be zerocopied. - tcp_zerocopy_receive would set recv_skip_hint of 0, in cases where we have a little bit of data after the perfectly-sized packets. To fix these issues, do not store the rounded down value in zc->length. Round down the length passed to zap_page_range(), and return min(inq, zc->length) when the zap_range is 0. Signed-off-by: Soheil Hassas Yeganeh Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- net/ipv4/tcp.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index f98a1882e537..9f41a76c1c54 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -1739,8 +1739,8 @@ static int tcp_zerocopy_receive(struct sock *sk, struct tcp_zerocopy_receive *zc) { unsigned long address = (unsigned long)zc->address; + u32 length = 0, seq, offset, zap_len; const skb_frag_t *frags = NULL; - u32 length = 0, seq, offset; struct vm_area_struct *vma; struct sk_buff *skb = NULL; struct tcp_sock *tp; @@ -1767,12 +1767,12 @@ static int tcp_zerocopy_receive(struct sock *sk, seq = tp->copied_seq; inq = tcp_inq(sk); zc->length = min_t(u32, zc->length, inq); - zc->length &= ~(PAGE_SIZE - 1); - if (zc->length) { - zap_page_range(vma, address, zc->length); + zap_len = zc->length & ~(PAGE_SIZE - 1); + if (zap_len) { + zap_page_range(vma, address, zap_len); zc->recv_skip_hint = 0; } else { - zc->recv_skip_hint = inq; + zc->recv_skip_hint = zc->length; } ret = 0; while (length + PAGE_SIZE <= zc->length) { -- 2.11.0