On Tue, 12 Nov 2013 18:02:57 +0800 Jason Wang <jasow...@redhat.com> 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 <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/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) I see no problem with this or the tuntap patch except that in both cases kernel coding style would prefer that you align the local variable declarations in a reverse pyramid, longest at the beginning, shortest at the end. - Greg -- 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/