[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <dadb229a-d811-4542-a53f-3a78e559e639@linux.dev>
Date: Tue, 2 Jan 2024 14:58:00 -0800
From: Martin KaFai Lau <martin.lau@...ux.dev>
To: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
Cc: netdev@...r.kernel.org, magnus.karlsson@...el.com, bjorn@...nel.org,
echaudro@...hat.com, lorenzo@...nel.org, tirthendu.sarkar@...el.com,
bpf@...r.kernel.org, ast@...nel.org, daniel@...earbox.net, andrii@...nel.org
Subject: Re: [PATCH v3 bpf 2/4] xsk: fix usage of multi-buffer BPF helpers for
ZC XDP
On 12/21/23 5:26 AM, Maciej Fijalkowski wrote:
> This comes from __xdp_return() call with xdp_buff argument passed as
> NULL which is supposed to be consumed by xsk_buff_free() call.
>
> To address this properly, in ZC case, a node that represents the frag
> being removed has to be pulled out of xskb_list. Introduce
> appriopriate xsk helpers to do such node operation and use them
> accordingly within bpf_xdp_adjust_tail().
[ ... ]
> +static inline struct xdp_buff *xsk_buff_get_tail(struct xdp_buff *first)
> +{
> + struct xdp_buff_xsk *xskb = container_of(first, struct xdp_buff_xsk, xdp);
> + struct xdp_buff_xsk *frag;
> +
> + frag = list_last_entry(&xskb->pool->xskb_list, struct xdp_buff_xsk,
> + xskb_list_node);
> + return &frag->xdp;
> +}
> +
[ ... ]
> +static void __shrink_data(struct xdp_buff *xdp, struct xdp_mem_info *mem_info,
> + skb_frag_t *frag, int shrink)
> +{
> + if (mem_info->type == MEM_TYPE_XSK_BUFF_POOL) {
> + struct xdp_buff *tail = xsk_buff_get_tail(xdp);
> +
> + if (tail)
> + tail->data_end -= shrink;
> + }
> + skb_frag_size_sub(frag, shrink);
> +}
> +
> +static bool shrink_data(struct xdp_buff *xdp, skb_frag_t *frag, int shrink)
> +{
> + struct xdp_mem_info *mem_info = &xdp->rxq->mem;
> +
> + if (skb_frag_size(frag) == shrink) {
> + struct page *page = skb_frag_page(frag);
> + struct xdp_buff *zc_frag = NULL;
> +
> + if (mem_info->type == MEM_TYPE_XSK_BUFF_POOL) {
> + zc_frag = xsk_buff_get_tail(xdp);
> +
> + if (zc_frag) {
Based on the xsk_buff_get_tail(), would zc_frag ever be NULL?
> + xdp_buff_clear_frags_flag(zc_frag);
> + xsk_buff_del_tail(zc_frag);
> + }
> + }
> +
> + __xdp_return(page_address(page), mem_info, false, zc_frag);
and iiuc, this patch is fixing a bug when zc_frag is NULL and
MEM_TYPE_XSK_BUFF_POOL.
> + return true;
> + }
> + __shrink_data(xdp, mem_info, frag, shrink);
> + return false;
> +}
> +
Powered by blists - more mailing lists