Re: [PATCH net 3/4] virtio-net: reset num_buf to 1 after linearizing packet

On 2018年05月21日 22:59, Michael S. Tsirkin wrote:

On Mon, May 21, 2018 at 04:35:05PM +0800, Jason Wang wrote:

quoted

If we successfully linearize the packets, num_buf were set to zero
which was wrong since we now have only 1 buffer to be used for e.g in
the error path of receive_mergeable(). Zero num_buf will lead the code
try to pop the buffers of next packet and drop it. Fixing this by set
num_buf to 1 if we successfully linearize the packet.

Fixes: 4941d472bf95 ("virtio-net: do not reset during XDP set")
Signed-off-by: Jason Wang <redacted>
---
  drivers/net/virtio_net.c | 1 +
  1 file changed, 1 insertion(+)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 6260d65..165a922 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c

@@ -722,6 +722,7 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
  						      &len);
  			if (!xdp_page)
  				goto err_xdp;
+			num_buf = 1;

So this is tweaked here for the benefit of err_skb below.
That's confusing and we won't remember to change it
if we change the error handling.

How about fixing the error path?


-        while (--num_buf) {
+        while (num_buf-- > 1) {

Seems more robust to me.

Looks good, will do this in V2.

Thanks

quoted

  			offset = VIRTIO_XDP_HEADROOM;
  		} else {
  			xdp_page = page;
-- 
2.7.4

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