netdev - [PATCH bpf 2/5] bpf: sockmap, added comments describing update proto rules

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Message-Id: <20231221232327.43678-3-john.fastabend@gmail.com>
Date: Thu, 21 Dec 2023 15:23:24 -0800
From: John Fastabend <john.fastabend@...il.com>
To: jakub@...udflare.com,
	rivendell7@...il.com,
	kuniyu@...zon.com
Cc: bpf@...r.kernel.org,
	netdev@...r.kernel.org
Subject: [PATCH bpf 2/5] bpf: sockmap, added comments describing update proto rules

Add a comment describing that the psock update proto callbback can be
called multiple times and this must be safe.

Signed-off-by: John Fastabend <john.fastabend@...il.com>
---
 include/linux/skmsg.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/include/linux/skmsg.h b/include/linux/skmsg.h
index c953b8c0d2f4..888a4b217829 100644
--- a/include/linux/skmsg.h
+++ b/include/linux/skmsg.h
@@ -100,6 +100,11 @@ struct sk_psock {
 	void (*saved_close)(struct sock *sk, long timeout);
 	void (*saved_write_space)(struct sock *sk);
 	void (*saved_data_ready)(struct sock *sk);
+	/* psock_update_sk_prot may be called with restore=false many times
+	 * so the handler must be safe for this case. It will be called
+	 * exactly once with restore=true when the psock is being destroyed
+	 * and psock refcnt is zero, but before an RCU grace period.
+	 */
 	int  (*psock_update_sk_prot)(struct sock *sk, struct sk_psock *psock,
 				     bool restore);
 	struct proto			*sk_proto;
-- 
2.33.0