在 2023/3/28 20:04, Xuan Zhuo 写道:
Separating the logic of preparation for xdp from receive_mergeable.
The purpose of this is to simplify the logic of execution of XDP.
The main logic here is that when headroom is insufficient, we need to
allocate a new page and calculate offset. It should be noted that if
there is new page, the variable page will refer to the new page.
Signed-off-by: Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx>
---
drivers/net/virtio_net.c | 135 ++++++++++++++++++++++-----------------
1 file changed, 77 insertions(+), 58 deletions(-)
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 4d2bf1ce0730..bb426958cdd4 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -1162,6 +1162,79 @@ static int virtnet_build_xdp_buff_mrg(struct net_device *dev,
return 0;
}
+static void *mergeable_xdp_prepare(struct virtnet_info *vi,
+ struct receive_queue *rq,
+ struct bpf_prog *xdp_prog,
+ void *ctx,
+ unsigned int *frame_sz,
+ int *num_buf,
+ struct page **page,
+ int offset,
+ unsigned int *len,
+ struct virtio_net_hdr_mrg_rxbuf *hdr)
+{
+ unsigned int truesize = mergeable_ctx_to_truesize(ctx);
+ unsigned int headroom = mergeable_ctx_to_headroom(ctx);
+ struct page *xdp_page;
+ unsigned int xdp_room;
+
+ /* Transient failure which in theory could occur if
+ * in-flight packets from before XDP was enabled reach
+ * the receive path after XDP is loaded.
+ */
+ if (unlikely(hdr->hdr.gso_type))
+ return NULL;
+
+ /* Now XDP core assumes frag size is PAGE_SIZE, but buffers
+ * with headroom may add hole in truesize, which
+ * make their length exceed PAGE_SIZE. So we disabled the
+ * hole mechanism for xdp. See add_recvbuf_mergeable().
+ */
+ *frame_sz = truesize;
+
+ /* This happens when headroom is not enough because
+ * of the buffer was prefilled before XDP is set.
+ * This should only happen for the first several packets.
+ * In fact, vq reset can be used here to help us clean up
+ * the prefilled buffers, but many existing devices do not
+ * support it, and we don't want to bother users who are
+ * using xdp normally.
+ */
+ if (!xdp_prog->aux->xdp_has_frags &&
+ (*num_buf > 1 || headroom < virtnet_get_headroom(vi))) {
+ /* linearize data for XDP */
+ xdp_page = xdp_linearize_page(rq, num_buf,
+ *page, offset,
+ VIRTIO_XDP_HEADROOM,
+ len);
+
+ if (!xdp_page)
+ return NULL;
+ } else if (unlikely(headroom < virtnet_get_headroom(vi))) {
+ xdp_room = SKB_DATA_ALIGN(VIRTIO_XDP_HEADROOM +
+ sizeof(struct skb_shared_info));
+ if (*len + xdp_room > PAGE_SIZE)
+ return NULL;
+
+ xdp_page = alloc_page(GFP_ATOMIC);
+ if (!xdp_page)
+ return NULL;
+
+ memcpy(page_address(xdp_page) + VIRTIO_XDP_HEADROOM,
+ page_address(*page) + offset, *len);
+ } else {
+ return page_address(*page) + offset;
This makes the code a little harder to be read than the original code.
Why not do a verbatim moving without introducing new logic? (Or
introducing new logic on top?)
Thanks
+ }
+
+ *frame_sz = PAGE_SIZE;
+
+ put_page(*page);
+
+ *page = xdp_page;
+
+ return page_address(xdp_page) + VIRTIO_XDP_HEADROOM;
+}
+
static struct sk_buff *receive_mergeable(struct net_device *dev,
struct virtnet_info *vi,
struct receive_queue *rq,
@@ -1181,7 +1254,7 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
unsigned int headroom = mergeable_ctx_to_headroom(ctx);
unsigned int tailroom = headroom ? sizeof(struct skb_shared_info) : 0;
unsigned int room = SKB_DATA_ALIGN(headroom + tailroom);
- unsigned int frame_sz, xdp_room;
+ unsigned int frame_sz;
int err;
head_skb = NULL;
@@ -1211,65 +1284,11 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
u32 act;
int i;
- /* Transient failure which in theory could occur if
- * in-flight packets from before XDP was enabled reach
- * the receive path after XDP is loaded.
- */
- if (unlikely(hdr->hdr.gso_type))
+ data = mergeable_xdp_prepare(vi, rq, xdp_prog, ctx, &frame_sz, &num_buf, &page,
+ offset, &len, hdr);
+ if (!data)
goto err_xdp;
- /* Now XDP core assumes frag size is PAGE_SIZE, but buffers
- * with headroom may add hole in truesize, which
- * make their length exceed PAGE_SIZE. So we disabled the
- * hole mechanism for xdp. See add_recvbuf_mergeable().
- */
- frame_sz = truesize;
-
- /* This happens when headroom is not enough because
- * of the buffer was prefilled before XDP is set.
- * This should only happen for the first several packets.
- * In fact, vq reset can be used here to help us clean up
- * the prefilled buffers, but many existing devices do not
- * support it, and we don't want to bother users who are
- * using xdp normally.
- */
- if (!xdp_prog->aux->xdp_has_frags &&
- (num_buf > 1 || headroom < virtnet_get_headroom(vi))) {
- /* linearize data for XDP */
- xdp_page = xdp_linearize_page(rq, &num_buf,
- page, offset,
- VIRTIO_XDP_HEADROOM,
- &len);
- frame_sz = PAGE_SIZE;
-
- if (!xdp_page)
- goto err_xdp;
- offset = VIRTIO_XDP_HEADROOM;
-
- put_page(page);
- page = xdp_page;
- } else if (unlikely(headroom < virtnet_get_headroom(vi))) {
- xdp_room = SKB_DATA_ALIGN(VIRTIO_XDP_HEADROOM +
- sizeof(struct skb_shared_info));
- if (len + xdp_room > PAGE_SIZE)
- goto err_xdp;
-
- xdp_page = alloc_page(GFP_ATOMIC);
- if (!xdp_page)
- goto err_xdp;
-
- memcpy(page_address(xdp_page) + VIRTIO_XDP_HEADROOM,
- page_address(page) + offset, len);
- frame_sz = PAGE_SIZE;
- offset = VIRTIO_XDP_HEADROOM;
-
- put_page(page);
- page = xdp_page;
- } else {
- xdp_page = page;
- }
-
- data = page_address(xdp_page) + offset;
err = virtnet_build_xdp_buff_mrg(dev, vi, rq, &xdp, data, len, frame_sz,
&num_buf, &xdp_frags_truesz, stats);
if (unlikely(err))
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