rfs: annotate lockless accesses to sk->sk_rxhash

stable inclusion
from stable-v4.19.286
commit 9b3907c57b044d4709fcadd7b0690004fb310962
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I7J5UF


CVE: NA

--------------------------------

[ Upstream commit 1e5c647c ]

Add READ_ONCE()/WRITE_ONCE() on accesses to sk->sk_rxhash.

This also prevents a (smart ?) compiler to remove the condition in:

if (sk->sk_rxhash != newval)
	sk->sk_rxhash = newval;

We need the condition to avoid dirtying a shared cache line.

Fixes: fec5e652 ("rfs: Receive Flow Steering")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Yongqiang Liu <liuyongqiang13@huawei.com>