----- 原始邮件 ----- > 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 <stefa...@redhat.com> > Cc: Michael S. Tsirkin <m...@redhat.com> > Signed-off-by: Jason Wang <jasow...@redhat.com> > --- > The patch was needed for stable. > --- > drivers/net/tun.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/drivers/net/tun.c b/drivers/net/tun.c > index 7cb105c..5537b65 100644 > --- a/drivers/net/tun.c > +++ b/drivers/net/tun.c > @@ -954,6 +954,11 @@ static struct sk_buff *tun_alloc_skb(struct tun_file > *tfile, > struct sock *sk = tfile->socket.sk; > struct sk_buff *skb; > int err; > + 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 >
Looks like reduce the linear here will cause callers' iov_pages() under estimation. Will send V2. > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majord...@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/