Messages in this thread | | | Date | Mon, 26 Jun 2023 17:36:52 +0200 | From | Stefano Garzarella <> | Subject | Re: [RFC PATCH v4 03/17] vsock/virtio: support to send non-linear skb |
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On Sat, Jun 03, 2023 at 11:49:25PM +0300, Arseniy Krasnov wrote: >For non-linear skb use its pages from fragment array as buffers in >virtio tx queue. These pages are already pinned by 'get_user_pages()' >during such skb creation. > >Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru> >--- > net/vmw_vsock/virtio_transport.c | 37 ++++++++++++++++++++++++++------ > 1 file changed, 31 insertions(+), 6 deletions(-) > >diff --git a/net/vmw_vsock/virtio_transport.c b/net/vmw_vsock/virtio_transport.c >index e95df847176b..6053d8341091 100644 >--- a/net/vmw_vsock/virtio_transport.c >+++ b/net/vmw_vsock/virtio_transport.c >@@ -100,7 +100,9 @@ virtio_transport_send_pkt_work(struct work_struct *work) > vq = vsock->vqs[VSOCK_VQ_TX]; > > for (;;) { >- struct scatterlist hdr, buf, *sgs[2]; >+ /* +1 is for packet header. */ >+ struct scatterlist *sgs[MAX_SKB_FRAGS + 1]; >+ struct scatterlist bufs[MAX_SKB_FRAGS + 1]; > int ret, in_sg = 0, out_sg = 0; > struct sk_buff *skb; > bool reply; >@@ -111,12 +113,35 @@ virtio_transport_send_pkt_work(struct work_struct *work) > > virtio_transport_deliver_tap_pkt(skb); > reply = virtio_vsock_skb_reply(skb); >+ sg_init_one(&bufs[0], virtio_vsock_hdr(skb), sizeof(*virtio_vsock_hdr(skb))); >+ sgs[out_sg++] = &bufs[0];
Can we use out_sg also to index bufs (here and in the rest of the code)?
E.g.
sg_init_one(&bufs[out_sg], ...) sgs[out_sg] = &bufs[out_sg]; ++out_sg;
... if (skb->len > 0) { sg_init_one(&bufs[out_sg], skb->data, skb->len); sgs[out_sg] = &bufs[out_sg]; ++out_sg; }
etc...
>+
For readability, I would move the smaller branch above:
if (!skb_is_nonlinear(skb)) { // small block ... } else { // big block ... }
>+ if (skb_is_nonlinear(skb)) { >+ struct skb_shared_info *si; >+ int i; >+ >+ si = skb_shinfo(skb); >+ >+ for (i = 0; i < si->nr_frags; i++) { >+ skb_frag_t *skb_frag = &si->frags[i]; >+ void *va = page_to_virt(skb_frag->bv_page); >+ >+ /* We will use 'page_to_virt()' for userspace page here, >+ * because virtio layer will call 'virt_to_phys()' later >+ * to fill buffer descriptor. We don't touch memory at >+ * "virtual" address of this page. >+ */ >+ sg_init_one(&bufs[i + 1], >+ va + skb_frag->bv_offset, >+ skb_frag->bv_len); >+ sgs[out_sg++] = &bufs[i + 1]; >+ } >+ } else { >+ if (skb->len > 0) {
Should we do the same check (skb->len > 0) for nonlinear skb as well? Or do the nonlinear ones necessarily have len > 0?
>+ sg_init_one(&bufs[1], skb->data, skb->len); >+ sgs[out_sg++] = &bufs[1]; >+ } > ^ Blank line that we can remove.
Stefano
>- sg_init_one(&hdr, virtio_vsock_hdr(skb), sizeof(*virtio_vsock_hdr(skb))); >- sgs[out_sg++] = &hdr; >- if (skb->len > 0) { >- sg_init_one(&buf, skb->data, skb->len); >- sgs[out_sg++] = &buf; > } > > ret = virtqueue_add_sgs(vq, sgs, out_sg, in_sg, skb, GFP_KERNEL); >-- >2.25.1 >
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