From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Wang Subject: [PATCH net 2/2] macvtap: limit head length of skb allocated Date: Tue, 12 Nov 2013 18:02:57 +0800 Message-ID: <1384250577-20330-2-git-send-email-jasowang@redhat.com> References: <1384250577-20330-1-git-send-email-jasowang@redhat.com> Cc: Jason Wang To: davem@davemloft.net, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, mst@redhat.com, stefanha@redhat.com Return-path: Received: from mx1.redhat.com ([209.132.183.28]:5421 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754583Ab3KLKDL (ORCPT ); Tue, 12 Nov 2013 05:03:11 -0500 In-Reply-To: <1384250577-20330-1-git-send-email-jasowang@redhat.com> Sender: netdev-owner@vger.kernel.org List-ID: We currently use hdr_len as a hint of head length which is advertised by guest. But when guest advertise a very big value, it can lead to an 64K+ allocating of kmalloc() which has a very high possibility of failure when host memory is fragmented or under heavy stress. The huge hdr_len also reduce the effect of zerocopy or even disable if a gso skb is linearized in guest. To solves those issues, this patch introduces an upper limit (PAGE_SIZE) of the head, which guarantees an order 0 allocation each time. Cc: Stefan Hajnoczi Cc: Michael S. Tsirkin Signed-off-by: Jason Wang --- The patch was needed for stable. --- drivers/net/macvtap.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c index 9dccb1e..7ee6f9d 100644 --- a/drivers/net/macvtap.c +++ b/drivers/net/macvtap.c @@ -523,6 +523,11 @@ static inline struct sk_buff *macvtap_alloc_skb(struct sock *sk, size_t prepad, int noblock, int *err) { struct sk_buff *skb; + int good_linear = SKB_MAX_HEAD(prepad); + + /* Don't use huge linear part */ + if (linear > good_linear) + linear = good_linear; /* Under a page? Don't bother with paged skb. */ if (prepad + len < PAGE_SIZE || !linear) -- 1.8.3.2