[PATCH net v2 2/2] virtio_net: get build_skb() buf by data ptr
From: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Date: 2021-06-01 06:40:05
Also in:
bpf, virtualization
Subsystem:
networking drivers, the rest, virtio net driver · Maintainers:
Andrew Lunn, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds, "Michael S. Tsirkin", Jason Wang
In the case of merge, the page passed into page_to_skb() may be a head page, not the page where the current data is located. So when trying to get the buf where the data is located, we should get buf based on headroom instead of offset. This patch solves this problem. But if you don't use this patch, the original code can also run, because if the page is not the page of the current data, the calculated tailroom will be less than 0, and will not enter the logic of build_skb() . The significance of this patch is to modify this logical problem, allowing more situations to use build_skb(). Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com> --- drivers/net/virtio_net.c | 17 ++++++----------- 1 file changed, 6 insertions(+), 11 deletions(-)
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 6b929aca155a..fa407eb8b457 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c@@ -401,18 +401,13 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi, /* If headroom is not 0, there is an offset between the beginning of the * data and the allocated space, otherwise the data and the allocated * space are aligned. + * + * Buffers with headroom use PAGE_SIZE as alloc size, see + * add_recvbuf_mergeable() + get_mergeable_buf_len() */ - if (headroom) { - /* Buffers with headroom use PAGE_SIZE as alloc size, - * see add_recvbuf_mergeable() + get_mergeable_buf_len() - */ - truesize = PAGE_SIZE; - tailroom = truesize - len - offset; - buf = page_address(page); - } else { - tailroom = truesize - len; - buf = p; - } + truesize = headroom ? PAGE_SIZE : truesize; + tailroom = truesize - len - headroom; + buf = p - headroom; len -= hdr_len; offset += hdr_padded_len;
--
2.31.0