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Message-Id: <20190326153455.155399-1-edumazet@google.com>
Date: Tue, 26 Mar 2019 08:34:55 -0700
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>
Cc: netdev <netdev@...r.kernel.org>,
Eric Dumazet <edumazet@...gle.com>,
Eric Dumazet <eric.dumazet@...il.com>,
Willem de Bruijn <willemb@...gle.com>,
Soheil Hassas Yeganeh <soheil@...gle.com>
Subject: [PATCH v2 net-next] tcp: fix zerocopy and notsent_lowat issues
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: 472c2e07eef0 ("tcp: add one skb cache for tx")
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Cc: Willem de Bruijn <willemb@...gle.com>
Cc: Soheil Hassas Yeganeh <soheil@...gle.com>
---
include/net/sock.h | 9 +++++----
net/ipv4/tcp.c | 13 +++----------
2 files changed, 8 insertions(+), 14 deletions(-)
diff --git a/include/net/sock.h b/include/net/sock.h
index 577d91fb56267371c6bc5ae65f7454deba726bd6..7fa2232785226bcafd46b230559964fd16f3c4f4 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -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)
{
- if (!sk->sk_tx_skb_cache) {
- 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);
+ if (!sk->sk_tx_skb_cache) {
+ skb_zcopy_clear(skb, true);
+ sk->sk_tx_skb_cache = skb;
+ return;
+ }
__kfree_skb(skb);
}
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 29b94edf05f9357d3a33744d677827ce624738ae..82bd707c03472f2cebb1a90d5f1c13acc821468f 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -865,14 +865,9 @@ struct sk_buff *sk_stream_alloc_skb(struct sock *sk, int size, gfp_t gfp,
{
struct sk_buff *skb;
- 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 (likely(!size)) {
+ skb = sk->sk_tx_skb_cache;
+ 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;
}
--
2.21.0.392.gf8f6787159e-goog
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