Re: [PATCH net-next] virtio-net: invoke zerocopy callback on xmit path if no tx napi
From: Willem de Bruijn <willemdebruijn.kernel@gmail.com>
Date: 2017-08-20 20:49:15
Also in:
virtualization
On Sat, Aug 19, 2017 at 2:38 AM, Koichiro Den [off-list ref] wrote:
Facing the possible unbounded delay relying on freeing on xmit path, we also better to invoke and clear the upper layer zerocopy callback beforehand to keep them from waiting for unbounded duration in vain.
Good point.
For instance, this removes the possible deadlock in the case that the upper layer is a zerocopy-enabled vhost-net. This does not apply if napi_tx is enabled since it will be called in reasonale time.
Indeed. Btw, I am gathering data to eventually make napi the default mode. But that is taking some time.
quoted hunk ↗ jump to hunk
Signed-off-by: Koichiro Den <redacted> --- drivers/net/virtio_net.c | 8 ++++++++ 1 file changed, 8 insertions(+)diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index 4302f313d9a7..f7deaa5b7b50 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c@@ -1290,6 +1290,14 @@ static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev) /* Don't wait up for transmitted skbs to be freed. */ if (!use_napi) { + if (skb_shinfo(skb)->tx_flags & SKBTX_DEV_ZEROCOPY) { + struct ubuf_info *uarg; + uarg = skb_shinfo(skb)->destructor_arg; + if (uarg->callback) + uarg->callback(uarg, true); + skb_shinfo(skb)->destructor_arg = NULL; + skb_shinfo(skb)->tx_flags &= ~SKBTX_DEV_ZEROCOPY; + }
Instead of open coding, this can use skb_zcopy_clear.
skb_orphan(skb);
nf_reset(skb);
}
--
2.9.4