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@intel.com>
Link: https://lore.kernel.org/r/20230313215553.1045175-4-aleksander.lobakin@intel.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/net/core/xdp.c b/net/core/xdp.c
index 8c92fc5..a2237cf 100644 (file)
--- 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);