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 <stefa...@redhat.com>
> Cc: Michael S. Tsirkin <m...@redhat.com>
> Signed-off-by: Jason Wang <jasow...@redhat.com>
Acked-by: Michael S. Tsirkin <m...@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)
> --
> 1.8.3.2
>
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