netdev - [PATCH bpf-next v2 2/3] xdp: recycle Page Pool backed skbs built from XDP frames

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Date:   Fri,  3 Mar 2023 14:32:31 +0100
From:   Alexander Lobakin <aleksander.lobakin@...el.com>
To:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <martin.lau@...ux.dev>
Cc:     Alexander Lobakin <aleksander.lobakin@...el.com>,
        Maciej Fijalkowski <maciej.fijalkowski@...el.com>,
        Larysa Zaremba <larysa.zaremba@...el.com>,
        Toke Høiland-Jørgensen <toke@...hat.com>,
        Song Liu <song@...nel.org>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        Menglong Dong <imagedong@...cent.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>, bpf@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH bpf-next v2 2/3] xdp: recycle Page Pool backed skbs built from XDP frames

__xdp_build_skb_from_frame() state(d):

/* Until page_pool get SKB return path, release DMA here */

Page Pool got skb pages recycling in April 2021, but missed this
function.

xdp_release_frame() is relevant only for Page Pool backed frames and it
detaches the page from the corresponding page_pool in order to make it
freeable via page_frag_free(). It can instead just mark the output skb
as eligible for recycling if the frame is backed by a pp. No change for
other memory model types (the same condition check as before).
cpumap redirect and veth on Page Pool drivers now become zero-alloc (or
almost).

Signed-off-by: Alexander Lobakin <aleksander.lobakin@...el.com>
---
 net/core/xdp.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/core/xdp.c b/net/core/xdp.c
index 8c92fc553317..a2237cfca8e9 100644
--- a/net/core/xdp.c
+++ b/net/core/xdp.c
@@ -658,8 +658,8 @@ struct sk_buff *__xdp_build_skb_from_frame(struct xdp_frame *xdpf,
 	 * - RX ring dev queue index	(skb_record_rx_queue)
 	 */
 
-	/* Until page_pool get SKB return path, release DMA here */
-	xdp_release_frame(xdpf);
+	if (xdpf->mem.type == MEM_TYPE_PAGE_POOL)
+		skb_mark_for_recycle(skb);
 
 	/* Allow SKB to reuse area used by xdp_frame */
 	xdp_scrub_frame(xdpf);
-- 
2.39.2