From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [PATCH net 2/2] macvtap: limit head length of skb allocated Date: Tue, 12 Nov 2013 13:20:35 +0200 Message-ID: <20131112112035.GB28597@redhat.com> References: <1384250577-20330-1-git-send-email-jasowang@redhat.com> <1384250577-20330-2-git-send-email-jasowang@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: davem@davemloft.net, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, stefanha@redhat.com To: Jason Wang Return-path: Received: from mx1.redhat.com ([209.132.183.28]:43441 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751559Ab3KLLmL (ORCPT ); Tue, 12 Nov 2013 06:42:11 -0500 Content-Disposition: inline In-Reply-To: <1384250577-20330-2-git-send-email-jasowang@redhat.com> Sender: netdev-owner@vger.kernel.org List-ID: On Tue, Nov 12, 2013 at 06:02:57PM +0800, Jason Wang wrote: > 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 Acked-by: Michael S. Tsirkin > --- > 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 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/