netdev - [PATCH net-next 26/35] rxrpc: Remove RCU from peer->error

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Message-ID: <166982748290.621383.837780227002133853.stgit@warthog.procyon.org.uk>
Date:   Wed, 30 Nov 2022 16:58:02 +0000
From:   David Howells <dhowells@...hat.com>
To:     netdev@...r.kernel.org
Cc:     Marc Dionne <marc.dionne@...istor.com>,
        linux-afs@...ts.infradead.org, dhowells@...hat.com,
        linux-afs@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH net-next 26/35] rxrpc: Remove RCU from peer->error_targets
 list

Remove the RCU requirements from the peer's list of error targets so that
the error distributor can call sleeping functions.

Signed-off-by: David Howells <dhowells@...hat.com>
cc: Marc Dionne <marc.dionne@...istor.com>
cc: linux-afs@...ts.infradead.org
---

 net/rxrpc/call_accept.c |    6 ++++++
 net/rxrpc/call_object.c |    2 +-
 net/rxrpc/conn_client.c |    4 ++++
 net/rxrpc/conn_object.c |    6 +++---
 net/rxrpc/output.c      |    6 ------
 net/rxrpc/peer_event.c  |   15 ++++++++++++++-
 6 files changed, 28 insertions(+), 11 deletions(-)

diff --git a/net/rxrpc/call_accept.c b/net/rxrpc/call_accept.c
index 8bc327aa2beb..5f978b0b2404 100644
--- a/net/rxrpc/call_accept.c
+++ b/net/rxrpc/call_accept.c
@@ -433,6 +433,12 @@ struct rxrpc_call *rxrpc_new_incoming_call(struct rxrpc_local *local,
 	 */
 	rxrpc_put_call(call, rxrpc_call_put_discard_prealloc);
 
+	if (hlist_unhashed(&call->error_link)) {
+		spin_lock(&call->peer->lock);
+		hlist_add_head(&call->error_link, &call->peer->error_targets);
+		spin_unlock(&call->peer->lock);
+	}
+
 	_leave(" = %p{%d}", call, call->debug_id);
 	return call;
 
diff --git a/net/rxrpc/call_object.c b/net/rxrpc/call_object.c
index 96a7edd3a842..7570b4e67bc5 100644
--- a/net/rxrpc/call_object.c
+++ b/net/rxrpc/call_object.c
@@ -442,7 +442,7 @@ void rxrpc_incoming_call(struct rxrpc_sock *rx,
 	rcu_assign_pointer(conn->channels[chan].call, call);
 
 	spin_lock(&conn->peer->lock);
-	hlist_add_head_rcu(&call->error_link, &conn->peer->error_targets);
+	hlist_add_head(&call->error_link, &conn->peer->error_targets);
 	spin_unlock(&conn->peer->lock);
 
 	rxrpc_start_call_timer(call);
diff --git a/net/rxrpc/conn_client.c b/net/rxrpc/conn_client.c
index ab3dd22fadc0..3c7b1bdec0db 100644
--- a/net/rxrpc/conn_client.c
+++ b/net/rxrpc/conn_client.c
@@ -786,6 +786,10 @@ void rxrpc_expose_client_call(struct rxrpc_call *call)
 		if (chan->call_counter >= INT_MAX)
 			set_bit(RXRPC_CONN_DONT_REUSE, &conn->flags);
 		trace_rxrpc_client(conn, channel, rxrpc_client_exposed);
+
+		spin_lock(&call->peer->lock);
+		hlist_add_head(&call->error_link, &call->peer->error_targets);
+		spin_unlock(&call->peer->lock);
 	}
 }
 
diff --git a/net/rxrpc/conn_object.c b/net/rxrpc/conn_object.c
index c2e05ea29f12..5a39255ea014 100644
--- a/net/rxrpc/conn_object.c
+++ b/net/rxrpc/conn_object.c
@@ -215,9 +215,9 @@ void rxrpc_disconnect_call(struct rxrpc_call *call)
 	call->peer->cong_ssthresh = call->cong_ssthresh;
 
 	if (!hlist_unhashed(&call->error_link)) {
-		spin_lock_bh(&call->peer->lock);
-		hlist_del_rcu(&call->error_link);
-		spin_unlock_bh(&call->peer->lock);
+		spin_lock(&call->peer->lock);
+		hlist_del_init(&call->error_link);
+		spin_unlock(&call->peer->lock);
 	}
 
 	if (rxrpc_is_client_call(call))
diff --git a/net/rxrpc/output.c b/net/rxrpc/output.c
index c8147e50060b..71963b4523be 100644
--- a/net/rxrpc/output.c
+++ b/net/rxrpc/output.c
@@ -394,12 +394,6 @@ int rxrpc_send_data_packet(struct rxrpc_call *call, struct rxrpc_txbuf *txb)
 
 	_enter("%x,{%d}", txb->seq, txb->len);
 
-	if (hlist_unhashed(&call->error_link)) {
-		spin_lock_bh(&call->peer->lock);
-		hlist_add_head_rcu(&call->error_link, &call->peer->error_targets);
-		spin_unlock_bh(&call->peer->lock);
-	}
-
 	/* Each transmission of a Tx packet needs a new serial number */
 	serial = atomic_inc_return(&conn->serial);
 	txb->wire.serial = htonl(serial);
diff --git a/net/rxrpc/peer_event.c b/net/rxrpc/peer_event.c
index 94f63fb1bd67..97d017ca3dc4 100644
--- a/net/rxrpc/peer_event.c
+++ b/net/rxrpc/peer_event.c
@@ -207,11 +207,24 @@ static void rxrpc_distribute_error(struct rxrpc_peer *peer, int error,
 				   enum rxrpc_call_completion compl)
 {
 	struct rxrpc_call *call;
+	HLIST_HEAD(error_targets);
+
+	spin_lock(&peer->lock);
+	hlist_move_list(&peer->error_targets, &error_targets);
+
+	while (!hlist_empty(&error_targets)) {
+		call = hlist_entry(error_targets.first,
+				   struct rxrpc_call, error_link);
+		hlist_del_init(&call->error_link);
+		spin_unlock(&peer->lock);
 
-	hlist_for_each_entry_rcu(call, &peer->error_targets, error_link) {
 		rxrpc_see_call(call, rxrpc_call_see_distribute_error);
 		rxrpc_set_call_completion(call, compl, 0, -error);
+
+		spin_lock(&peer->lock);
 	}
+
+	spin_unlock(&peer->lock);
 }
 
 /*