tcp: fix zerocopy and notsent_lowat issues (4f661542) · Commits · 戴 / test

My recent patch had at least three problems : 1) TX zerocopy wants notification when skb is acknowledged, thus we need to call skb_zcopy_clear() if the skb is cached into sk->sk_tx_skb_cache 2) Some applications might expect precise EPOLLOUT notifications, so we need to update sk->sk_wmem_queued and call sk_mem_uncharge() from sk_wmem_free_skb() in all cases. The SOCK_QUEUE_SHRUNK flag must also be set. 3) Reuse of saved skb should have used skb_cloned() instead of simply checking if the fast clone has been freed. Fixes: ("tcp: add one skb cache for tx") Signed-off-by:

Eric Dumazet <edumazet@google.com> Cc: Willem de Bruijn <willemb@google.com> Cc: Soheil Hassas Yeganeh <soheil@google.com> Acked-by:

Soheil Hassas Yeganeh <soheil@google.com> Tested-by:

Holger Hoffstätte <holger@applied-asynchrony.com> Signed-off-by:

David S. Miller <davem@davemloft.net>

include/net/sock.h

+4 −3

Original line number	Diff line number	Diff line
		@@ -1465,13 +1465,14 @@ static inline void sk_mem_uncharge(struct sock *sk, int size)

		static inline void sk_wmem_free_skb(struct sock sk, struct sk_buff skb)
		{
		sock_set_flag(sk, SOCK_QUEUE_SHRUNK);
		sk->sk_wmem_queued -= skb->truesize;
		sk_mem_uncharge(sk, skb->truesize);
		if (!sk->sk_tx_skb_cache) {
		skb_zcopy_clear(skb, true);
		sk->sk_tx_skb_cache = skb;
		return;
		}
		sock_set_flag(sk, SOCK_QUEUE_SHRUNK);
		sk->sk_wmem_queued -= skb->truesize;
		sk_mem_uncharge(sk, skb->truesize);
		__kfree_skb(skb);
		}

net/ipv4/tcp.c

+3 −10

Original line number	Diff line number	Diff line
		@@ -865,14 +865,9 @@ struct sk_buff sk_stream_alloc_skb(struct sock sk, int size, gfp_t gfp,
		{
		struct sk_buff *skb;

		if (likely(!size)) {
		skb = sk->sk_tx_skb_cache;
		if (skb && !size) {
		const struct sk_buff_fclones *fclones;

		fclones = container_of(skb, struct sk_buff_fclones, skb1);
		if (refcount_read(&fclones->fclone_ref) == 1) {
		sk->sk_wmem_queued -= skb->truesize;
		sk_mem_uncharge(sk, skb->truesize);
		if (skb && !skb_cloned(skb)) {
		skb->truesize -= skb->data_len;
		sk->sk_tx_skb_cache = NULL;
		pskb_trim(skb, 0);
		@@ -2543,8 +2538,6 @@ void tcp_write_queue_purge(struct sock *sk)
		tcp_rtx_queue_purge(sk);
		skb = sk->sk_tx_skb_cache;
		if (skb) {
		sk->sk_wmem_queued -= skb->truesize;
		sk_mem_uncharge(sk, skb->truesize);
		__kfree_skb(skb);
		sk->sk_tx_skb_cache = NULL;
		}

Admin message