On 2023/3/2 0:03, Alexander Lobakin wrote: > __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 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@xxxxxxxxx> > --- > 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); We both rely on both skb->pp_recycle and page->pp_magic to decide the page is really from page pool. So there was a few corner case problem when we are sharing a page for different skb in the driver level or calling skb_clone() or skb_try_coalesce(). see: https://github.com/torvalds/linux/commit/2cc3aeb5ecccec0d266813172fcd82b4b5fa5803 https://lore.kernel.org/netdev/MW5PR15MB51214C0513DB08A3607FBC1FBDE19@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/t/ https://lore.kernel.org/netdev/167475990764.1934330.11960904198087757911.stgit@localhost.localdomain/ As the 'struct xdp_frame' also use 'struct skb_shared_info' which is sharable, see xdp_get_shared_info_from_frame(). For now xdpf_clone() does not seems to handling frag page yet, so it should be fine for now. IMHO we should find a way to use per-page marker, instead of both per-skb and per-page markers, in order to avoid the above problem for xdp if xdp has a similar processing as skb, as suggested by Eric. https://lore.kernel.org/netdev/CANn89iKgZU4Q+THXupzZi4hETuKuCOvOB=iHpp5JzQTNv_Fg_A@xxxxxxxxxxxxxx/ > > /* Allow SKB to reuse area used by xdp_frame */ > xdp_scrub_frame(xdpf); >
