netdev - [PATCH net-next 6/8] mptcp: remove locking in mptcp_diag_fill

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Date:   Fri,  8 Apr 2022 12:45:59 -0700
From:   Mat Martineau <mathew.j.martineau@...ux.intel.com>
To:     netdev@...r.kernel.org
Cc:     Florian Westphal <fw@...len.de>, davem@...emloft.net,
        kuba@...nel.org, pabeni@...hat.com, matthieu.baerts@...sares.net,
        mptcp@...ts.linux.dev,
        Mat Martineau <mathew.j.martineau@...ux.intel.com>
Subject: [PATCH net-next 6/8] mptcp: remove locking in mptcp_diag_fill_info

From: Florian Westphal <fw@...len.de>

Problem is that listener iteration would call this from atomic context
so this locking is not allowed.

One way is to drop locks before calling the helper, but afaics the lock
isn't really needed, all values are fetched via READ_ONCE().

Signed-off-by: Florian Westphal <fw@...len.de>
Signed-off-by: Mat Martineau <mathew.j.martineau@...ux.intel.com>
---
 net/mptcp/sockopt.c | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/net/mptcp/sockopt.c b/net/mptcp/sockopt.c
index f949d22f52bd..826b0c1dae98 100644
--- a/net/mptcp/sockopt.c
+++ b/net/mptcp/sockopt.c
@@ -853,15 +853,11 @@ static int mptcp_getsockopt_first_sf_only(struct mptcp_sock *msk, int level, int
 
 void mptcp_diag_fill_info(struct mptcp_sock *msk, struct mptcp_info *info)
 {
-	struct sock *sk = &msk->sk.icsk_inet.sk;
 	u32 flags = 0;
-	bool slow;
 	u8 val;
 
 	memset(info, 0, sizeof(*info));
 
-	slow = lock_sock_fast(sk);
-
 	info->mptcpi_subflows = READ_ONCE(msk->pm.subflows);
 	info->mptcpi_add_addr_signal = READ_ONCE(msk->pm.add_addr_signaled);
 	info->mptcpi_add_addr_accepted = READ_ONCE(msk->pm.add_addr_accepted);
@@ -882,8 +878,6 @@ void mptcp_diag_fill_info(struct mptcp_sock *msk, struct mptcp_info *info)
 	info->mptcpi_snd_una = READ_ONCE(msk->snd_una);
 	info->mptcpi_rcv_nxt = READ_ONCE(msk->ack_seq);
 	info->mptcpi_csum_enabled = READ_ONCE(msk->csum_enabled);
-
-	unlock_sock_fast(sk, slow);
 }
 EXPORT_SYMBOL_GPL(mptcp_diag_fill_info);
 
-- 
2.35.1