On Tue, Aug 18, 2020 at 4:58 AM Miaohe Lin <linmia...@huawei.com> wrote:
>
> The npages test against MAX_SKB_FRAGS can be relaxed if we succeed to
> allocate high order pages as the note in comment said.
>
> Signed-off-by: Miaohe Lin <linmia...@huawei.com>
> ---
> net/core/skbuff.c | 11 ++++-------
> 1 file changed, 4 insertions(+), 7 deletions(-)
>
> diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> index 2f7dd689bccc..ca432bbfd90b 100644
> --- a/net/core/skbuff.c
> +++ b/net/core/skbuff.c
> @@ -5758,13 +5758,6 @@ struct sk_buff *alloc_skb_with_frags(unsigned long
> header_len,
> struct page *page;
> int i;
>
> - *errcode = -EMSGSIZE;
> - /* Note this test could be relaxed, if we succeed to allocate
> - * high order pages...
> - */
> - if (npages > MAX_SKB_FRAGS)
> - return NULL;
> -
> *errcode = -ENOBUFS;
> skb = alloc_skb(header_len, gfp_mask);
> if (!skb)
> @@ -5775,6 +5768,10 @@ struct sk_buff *alloc_skb_with_frags(unsigned long
> header_len,
> for (i = 0; npages > 0; i++) {
> int order = max_page_order;
>
> + if (unlikely(i >= MAX_SKB_FRAGS)) {
> + *errcode = -EMSGSIZE;
> + goto failure;
> + }
> while (order) {
> if (npages >= 1 << order) {
> page = alloc_pages((gfp_mask &
> ~__GFP_DIRECT_RECLAIM) |
> --
> 2.19.1
We do not want this change.
This interface is used by datagram providers, we do not want to claim
they can safely use skb allocations over 64KB.
Returning -EMSGSIZE should not depend on availability of high-order pages.
The comment was a hint, but we need first a valid user before
considering expanding the interface.
