We can reserve the skb. When sending fails, NETDEV_TX_BUSY or
xskq_prod_reserve fails. As long as skb is successfully generated and
successfully configured, we can reserve skb if we encounter exceptions
later.
Especially when NETDEV_TX_BUSY fails, there is no need to deal with
the problem that xskq_prod_reserve has been updated.
Signed-off-by: Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx>
---
include/net/xdp_sock.h | 3 +++
net/xdp/xsk.c | 36 +++++++++++++++++++++++++++---------
2 files changed, 30 insertions(+), 9 deletions(-)
diff --git a/include/net/xdp_sock.h b/include/net/xdp_sock.h
index 4f4e93b..fead0c9 100644
--- a/include/net/xdp_sock.h
+++ b/include/net/xdp_sock.h
@@ -76,6 +76,9 @@ struct xdp_sock {
struct mutex mutex;
struct xsk_queue *fq_tmp; /* Only as tmp storage before bind */
struct xsk_queue *cq_tmp; /* Only as tmp storage before bind */
+
+ struct sk_buff *skb_undone;
+ bool skb_undone_reserve;
};
#ifdef CONFIG_XDP_SOCKETS
diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
index e28c682..1051024 100644
--- a/net/xdp/xsk.c
+++ b/net/xdp/xsk.c
@@ -435,6 +435,19 @@ static int xsk_generic_xmit(struct sock *sk)
if (xs->queue_id >= xs->dev->real_num_tx_queues)
goto out;
+ if (xs->skb_undone) {
+ if (xs->skb_undone_reserve) {
+ if (xskq_prod_reserve(xs->pool->cq))
+ goto out;
+
+ xs->skb_undone_reserve = false;
+ }
+
+ skb = xs->skb_undone;
+ xs->skb_undone = NULL;
+ goto xmit;
+ }
+
while (xskq_cons_peek_desc(xs->tx, &desc, xs->pool)) {
char *buffer;
u64 addr;
@@ -454,12 +467,7 @@ static int xsk_generic_xmit(struct sock *sk)
addr = desc.addr;
buffer = xsk_buff_raw_get_data(xs->pool, addr);
err = skb_store_bits(skb, 0, buffer, len);
- /* This is the backpressure mechanism for the Tx path.
- * Reserve space in the completion queue and only proceed
- * if there is space in it. This avoids having to implement
- * any buffering in the Tx path.
- */
- if (unlikely(err) || xskq_prod_reserve(xs->pool->cq)) {
+ if (unlikely(err)) {
kfree_skb(skb);
goto out;
}
@@ -470,12 +478,22 @@ static int xsk_generic_xmit(struct sock *sk)
skb_shinfo(skb)->destructor_arg = (void *)(long)desc.addr;
skb->destructor = xsk_destruct_skb;
+ /* This is the backpressure mechanism for the Tx path.
+ * Reserve space in the completion queue and only proceed
+ * if there is space in it. This avoids having to implement
+ * any buffering in the Tx path.
+ */
+ if (xskq_prod_reserve(xs->pool->cq)) {
+ xs->skb_undone_reserve = true;
+ xs->skb_undone = skb;
+ goto out;
+ }
+
+xmit:
err = __dev_direct_xmit(skb, xs->queue_id);
if (err == NETDEV_TX_BUSY) {
/* Tell user-space to retry the send */
- skb->destructor = sock_wfree;
- /* Free skb without triggering the perf drop trace */
- consume_skb(skb);
+ xs->skb_undone = skb;
err = -EAGAIN;
goto out;
}
--
1.8.3.1
