Re: [PATCH net-next] virtio-net: realign page_to_skb() after merges

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在 2021/8/3 上午1:57, Jakub Kicinski 写道:
We ended up merging two versions of the same patch set:

commit 8fb7da9e9907 ("virtio_net: get build_skb() buf by data ptr")
commit 5c37711d9f27 ("virtio-net: fix for unable to handle page fault for address")

into net, and

commit 7bf64460e3b2 ("virtio-net: get build_skb() buf by data ptr")
commit 6c66c147b9a4 ("virtio-net: fix for unable to handle page fault for address")

into net-next. Redo the merge from commit 126285651b7f ("Merge
ra.kernel.org:/pub/scm/linux/kernel/git/netdev/net"), so that
the most recent code remains.

Acked-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>


Acked-by: Jason Wang <jasowang@xxxxxxxxxx>


---
  drivers/net/virtio_net.c | 27 ++++++++-------------------
  1 file changed, 8 insertions(+), 19 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 56c3f8519093..74482a52f076 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -380,7 +380,7 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi,
  				   struct page *page, unsigned int offset,
  				   unsigned int len, unsigned int truesize,
  				   bool hdr_valid, unsigned int metasize,
-				   bool whole_page)
+				   unsigned int headroom)
  {
  	struct sk_buff *skb;
  	struct virtio_net_hdr_mrg_rxbuf *hdr;
@@ -398,28 +398,16 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi,
  	else
  		hdr_padded_len = sizeof(struct padded_vnet_hdr);
- /* If whole_page, there is an offset between the beginning of the
+	/* 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 (whole_page) {
-		/* Buffers with whole_page use PAGE_SIZE as alloc size,
-		 * see add_recvbuf_mergeable() + get_mergeable_buf_len()
-		 */
-		truesize = PAGE_SIZE;
-
-		/* page maybe head page, so we should get the buf by p, not the
-		 * page
-		 */
-		tailroom = truesize - len - offset_in_page(p);
-		buf = (char *)((unsigned long)p & PAGE_MASK);
-	} 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;
@@ -978,7 +966,8 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
  				put_page(page);
  				head_skb = page_to_skb(vi, rq, xdp_page, offset,
  						       len, PAGE_SIZE, false,
-						       metasize, true);
+						       metasize,
+						       VIRTIO_XDP_HEADROOM);
  				return head_skb;
  			}
  			break;
@@ -1029,7 +1018,7 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
  	rcu_read_unlock();
head_skb = page_to_skb(vi, rq, page, offset, len, truesize, !xdp_prog,
-			       metasize, !!headroom);
+			       metasize, headroom);
  	curr_skb = head_skb;
if (unlikely(!curr_skb))

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