netdev - [PATCH net-next 6/8] mptcp: avoid lock

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Date:   Fri, 12 Feb 2021 15:59:59 -0800
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, mptcp@...ts.01.org, matthieu.baerts@...sares.net,
        Mat Martineau <mathew.j.martineau@...ux.intel.com>
Subject: [PATCH net-next 6/8] mptcp: avoid lock_fast usage in accept path

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

Once event support is added this may need to allocate memory while msk
lock is held with softirqs disabled.

Not using lock_fast also allows to do the allocation with GFP_KERNEL.

Signed-off-by: Florian Westphal <fw@...len.de>
Signed-off-by: Mat Martineau <mathew.j.martineau@...ux.intel.com>
---
 net/mptcp/protocol.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 56240b87d464..fe6da1b77723 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -3260,9 +3260,8 @@ static int mptcp_stream_accept(struct socket *sock, struct socket *newsock,
 		struct mptcp_sock *msk = mptcp_sk(newsock->sk);
 		struct mptcp_subflow_context *subflow;
 		struct sock *newsk = newsock->sk;
-		bool slowpath;
 
-		slowpath = lock_sock_fast(newsk);
+		lock_sock(newsk);
 
 		/* PM/worker can now acquire the first subflow socket
 		 * lock without racing with listener queue cleanup,
@@ -3288,7 +3287,7 @@ static int mptcp_stream_accept(struct socket *sock, struct socket *newsock,
 			if (!ssk->sk_socket)
 				mptcp_sock_graft(ssk, newsock);
 		}
-		unlock_sock_fast(newsk, slowpath);
+		release_sock(newsk);
 	}
 
 	if (inet_csk_listen_poll(ssock->sk))
-- 
2.30.1