linux-kernel - [PATCH V4 net 3/3] tuntap: correctly add the missing XDP flush

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Date:   Sat, 24 Feb 2018 11:32:26 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     mst@...hat.com, sergei.shtylyov@...entembedded.com,
        christoffer.dall@...aro.org, brouer@...hat.com,
        Jason Wang <jasowang@...hat.com>
Subject: [PATCH V4 net 3/3] tuntap: correctly add the missing XDP flush

We don't flush batched XDP packets through xdp_do_flush_map(), this
will cause packets stall at TX queue. Consider we don't do XDP on NAPI
poll(), the only possible fix is to call xdp_do_flush_map()
immediately after xdp_do_redirect().

Note, this in fact won't try to batch packets through devmap, we could
address in the future.

Reported-by: Christoffer Dall <christoffer.dall@...aro.org>
Fixes: 761876c857cb ("tap: XDP support")
Signed-off-by: Jason Wang <jasowang@...hat.com>
---
 drivers/net/tun.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 63d39fe6..7433bb2 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1663,6 +1663,7 @@ static struct sk_buff *tun_build_skb(struct tun_struct *tun,
 			get_page(alloc_frag->page);
 			alloc_frag->offset += buflen;
 			err = xdp_do_redirect(tun->dev, &xdp, xdp_prog);
+			xdp_do_flush_map();
 			if (err)
 				goto err_redirect;
 			rcu_read_unlock();
-- 
2.7.4