netdev - [PATCH RFC net-next 1/4] net: add SK_WMEM_ALLOC

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Message-ID: <20251008104612.1824200-2-edumazet@google.com>
Date: Wed,  8 Oct 2025 10:46:08 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>
Cc: Simon Horman <horms@...nel.org>, Kuniyuki Iwashima <kuniyu@...gle.com>, 
	Willem de Bruijn <willemb@...gle.com>, netdev@...r.kernel.org, eric.dumazet@...il.com, 
	Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH RFC net-next 1/4] net: add SK_WMEM_ALLOC_BIAS constant

sk->sk_wmem_alloc is initialized to 1, and sk_wmem_alloc_get()
takes care of this initial value.

Add SK_WMEM_ALLOC_BIAS define to not spread this magic value.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 include/net/sock.h | 3 ++-
 net/atm/common.c   | 2 +-
 net/core/sock.c    | 5 ++---
 3 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/include/net/sock.h b/include/net/sock.h
index 60bcb13f045c3144609908a36960528b33e4f71c..2794bc5c565424491a064049d3d76c3fb7ba1ed8 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -2303,6 +2303,7 @@ static inline int skb_copy_to_page_nocache(struct sock *sk, struct iov_iter *fro
 	return 0;
 }
 
+#define SK_WMEM_ALLOC_BIAS 1
 /**
  * sk_wmem_alloc_get - returns write allocations
  * @sk: socket
@@ -2311,7 +2312,7 @@ static inline int skb_copy_to_page_nocache(struct sock *sk, struct iov_iter *fro
  */
 static inline int sk_wmem_alloc_get(const struct sock *sk)
 {
-	return refcount_read(&sk->sk_wmem_alloc) - 1;
+	return refcount_read(&sk->sk_wmem_alloc) - SK_WMEM_ALLOC_BIAS;
 }
 
 /**
diff --git a/net/atm/common.c b/net/atm/common.c
index 881c7f259dbd46be35d71e558a73eb2f26223963..cecc71a8bee1176518a2d63b4613dbd243543695 100644
--- a/net/atm/common.c
+++ b/net/atm/common.c
@@ -157,7 +157,7 @@ int vcc_create(struct net *net, struct socket *sock, int protocol, int family, i
 	memset(&vcc->local, 0, sizeof(struct sockaddr_atmsvc));
 	memset(&vcc->remote, 0, sizeof(struct sockaddr_atmsvc));
 	vcc->qos.txtp.max_sdu = 1 << 16; /* for meta VCs */
-	refcount_set(&sk->sk_wmem_alloc, 1);
+	refcount_set(&sk->sk_wmem_alloc, SK_WMEM_ALLOC_BIAS);
 	atomic_set(&sk->sk_rmem_alloc, 0);
 	vcc->push = NULL;
 	vcc->pop = NULL;
diff --git a/net/core/sock.c b/net/core/sock.c
index dc03d4b5909a2a68aee84eb9a153b2c3970f6b32..542cfa16ee125f6c8487237c9040695d42794087 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -2313,7 +2313,7 @@ struct sock *sk_alloc(struct net *net, int family, gfp_t priority,
 		}
 
 		sock_net_set(sk, net);
-		refcount_set(&sk->sk_wmem_alloc, 1);
+		refcount_set(&sk->sk_wmem_alloc, SK_WMEM_ALLOC_BIAS);
 
 		mem_cgroup_sk_alloc(sk);
 		cgroup_sk_alloc(&sk->sk_cgrp_data);
@@ -2494,8 +2494,7 @@ struct sock *sk_clone_lock(const struct sock *sk, const gfp_t priority)
 
 	atomic_set(&newsk->sk_rmem_alloc, 0);
 
-	/* sk_wmem_alloc set to one (see sk_free() and sock_wfree()) */
-	refcount_set(&newsk->sk_wmem_alloc, 1);
+	refcount_set(&newsk->sk_wmem_alloc, SK_WMEM_ALLOC_BIAS);
 
 	atomic_set(&newsk->sk_omem_alloc, 0);
 	sk_init_common(newsk);
-- 
2.51.0.710.ga91ca5db03-goog