virtio_net: optimize mergeable_xdp_get_buf()

The previous patch, in order to facilitate review, I do not do any
modification. This patch has made some optimization on the top.

* remove some repeated logics in this function.
* add fast check for passing without any alloc.

Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index a75745dfe2e1e59776ba34402c1f8306e7411148..3c3602982ea2ca5c989f293c18471c4e42bebb3f 100644 (file)
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -1196,6 +1196,11 @@ static void *mergeable_xdp_get_buf(struct virtnet_info *vi,
         */
        *frame_sz = truesize;
 
+       if (likely(headroom >= virtnet_get_headroom(vi) &&
+                  (*num_buf == 1 || xdp_prog->aux->xdp_has_frags))) {
+               return page_address(*page) + offset;
+       }
+
        /* 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.
@@ -1204,22 +1209,15 @@ static void *mergeable_xdp_get_buf(struct virtnet_info *vi,
         * 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))) {
+       if (!xdp_prog->aux->xdp_has_frags) {
                /* 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)
                        return NULL;
-               offset = VIRTIO_XDP_HEADROOM;
-
-               put_page(*page);
-               *page = xdp_page;
-       } else if (unlikely(headroom < virtnet_get_headroom(vi))) {
+       } else {
                xdp_room = SKB_DATA_ALIGN(VIRTIO_XDP_HEADROOM +
                                          sizeof(struct skb_shared_info));
                if (*len + xdp_room > PAGE_SIZE)
@@ -1231,14 +1229,15 @@ static void *mergeable_xdp_get_buf(struct virtnet_info *vi,
 
                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;
        }
 
-       return page_address(*page) + offset;
+       *frame_sz = PAGE_SIZE;
+
+       put_page(*page);
+
+       *page = xdp_page;
+
+       return page_address(*page) + VIRTIO_XDP_HEADROOM;
 }
 
 static struct sk_buff *receive_mergeable(struct net_device *dev,