linux-kernel - [PATCH 4.15 076/122] tuntap: correctly add the missing XDP flush

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Message-Id: <20180307191740.280849456@linuxfoundation.org>
Date:   Wed,  7 Mar 2018 11:38:08 -0800
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Christoffer Dall <christoffer.dall@...aro.org>,
        Jason Wang <jasowang@...hat.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 4.15 076/122] tuntap: correctly add the missing XDP flush

4.15-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jason Wang <jasowang@...hat.com>


[ Upstream commit 1bb4f2e868a2891ab8bc668b8173d6ccb8c4ce6f ]

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>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/net/tun.c |    1 +
 1 file changed, 1 insertion(+)

--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1490,6 +1490,7 @@ static struct sk_buff *tun_build_skb(str
 			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();