netdev - [PATCH net] tcp: call sk_wmem_schedule before sk_mem

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Message-Id: <20210709154306.2276391-1-mailtalalahmad@gmail.com>
Date:   Fri,  9 Jul 2021 11:43:06 -0400
From:   Talal Ahmad <mailtalalahmad@...il.com>
To:     David Miller <davem@...emloft.net>
Cc:     netdev@...r.kernel.org, Talal Ahmad <talalahmad@...gle.com>,
        Willem de Bruijn <willemb@...gle.com>,
        Wei Wang <weiwan@...gle.com>,
        Soheil Hassas Yeganeh <soheil@...gle.com>,
        Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net] tcp: call sk_wmem_schedule before sk_mem_charge in zerocopy path

From: Talal Ahmad <talalahmad@...gle.com>

sk_wmem_schedule makes sure that sk_forward_alloc has enough
bytes for charging that is going to be done by sk_mem_charge.

In the transmit zerocopy path, there is sk_mem_charge but there was
no call to sk_wmem_schedule. This change adds that call.

Without this call to sk_wmem_schedule, sk_forward_alloc can go
negetive which is a bug because sk_forward_alloc is a per-socket
space that has been forward charged so this can't be negative.

Fixes: f214f915e7db ("tcp: enable MSG_ZEROCOPY")
Signed-off-by: Talal Ahmad <talalahmad@...gle.com>
Reviewed-by: Willem de Bruijn <willemb@...gle.com>
Reviewed-by: Wei Wang <weiwan@...gle.com>
Reviewed-by: Soheil Hassas Yeganeh <soheil@...gle.com>
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 net/ipv4/tcp.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index d5ab5f243640..8cb44040ec68 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -1375,6 +1375,9 @@ int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size)
 			}
 			pfrag->offset += copy;
 		} else {
+			if (!sk_wmem_schedule(sk, copy))
+				goto wait_for_space;
+
 			err = skb_zerocopy_iter_stream(sk, skb, msg, copy, uarg);
 			if (err == -EMSGSIZE || err == -EEXIST) {
 				tcp_mark_push(tp, skb);
-- 
2.32.0.93.g670b81a890-goog