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Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 From: David Howells To: netdev@vger.kernel.org Cc: David Howells , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Marc Dionne , linux-afs@lists.infradead.org, linux-kernel@vger.kernel.org Subject: [PATCH net-next] rxrpc: Fix overproduction of wakeups to recvmsg() MIME-Version: 1.0 Content-ID: <3386148.1676497685.1@warthog.procyon.org.uk> Content-Transfer-Encoding: quoted-printable Date: Wed, 15 Feb 2023 21:48:05 +0000 Message-ID: <3386149.1676497685@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 3.1 on 10.11.54.4 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Fix three cases of overproduction of wakeups: (1) rxrpc_input_split_jumbo() conditionally notifies the app that there's data for recvmsg() to collect if it queues some data - and then its only caller, rxrpc_input_data(), goes and wakes up recvmsg() anyway. Fix the rxrpc_input_data() to only do the wakeup in failure cases. (2) If a DATA packet is received for a call by the I/O thread whilst recvmsg() is busy draining the call's rx queue in the app thread, the call will left on the recvmsg() queue for recvmsg() to pick up, even though there isn't any data on it. This can cause an unexpected recvmsg() with a 0 return and no MSG_EOR set after the reply has been posted to a service call. Fix this by discarding pending calls from the recvmsg() queue that don't need servicing yet. (3) Not-yet-completed calls get requeued after having data read from them, even if they have no data to read. Fix this by only requeuing them if they have data waiting on them; if they don't, the I/O thread will requeue them when data arrives or they fail. Signed-off-by: David Howells cc: Marc Dionne cc: linux-afs@lists.infradead.org --- include/trace/events/rxrpc.h | 1 + net/rxrpc/input.c | 2 +- net/rxrpc/recvmsg.c | 16 +++++++++++++++- 3 files changed, 17 insertions(+), 2 deletions(-) diff --git a/include/trace/events/rxrpc.h b/include/trace/events/rxrpc.h index c3c0b0aa8381..4c53a5ef6257 100644 --- a/include/trace/events/rxrpc.h +++ b/include/trace/events/rxrpc.h @@ -318,6 +318,7 @@ EM(rxrpc_recvmsg_return, "RETN") \ EM(rxrpc_recvmsg_terminal, "TERM") \ EM(rxrpc_recvmsg_to_be_accepted, "TBAC") \ + EM(rxrpc_recvmsg_unqueue, "UNQU") \ E_(rxrpc_recvmsg_wait, "WAIT") =20 #define rxrpc_rtt_tx_traces \ diff --git a/net/rxrpc/input.c b/net/rxrpc/input.c index d68848fce51f..030d64f282f3 100644 --- a/net/rxrpc/input.c +++ b/net/rxrpc/input.c @@ -606,7 +606,7 @@ static void rxrpc_input_data(struct rxrpc_call *call, s= truct sk_buff *skb) rxrpc_proto_abort(call, sp->hdr.seq, rxrpc_badmsg_bad_jumbo); goto out_notify; } - skb =3D NULL; + return; =20 out_notify: trace_rxrpc_notify_socket(call->debug_id, serial); diff --git a/net/rxrpc/recvmsg.c b/net/rxrpc/recvmsg.c index 76eb2b9cd936..a482f88c5fc5 100644 --- a/net/rxrpc/recvmsg.c +++ b/net/rxrpc/recvmsg.c @@ -334,10 +334,23 @@ int rxrpc_recvmsg(struct socket *sock, struct msghdr = *msg, size_t len, =20 /* Find the next call and dequeue it if we're not just peeking. If we * do dequeue it, that comes with a ref that we will need to release. + * We also want to weed out calls that got requeued whilst we were + * shovelling data out. */ spin_lock(&rx->recvmsg_lock); l =3D rx->recvmsg_q.next; call =3D list_entry(l, struct rxrpc_call, recvmsg_link); + + if (!rxrpc_call_is_complete(call) && + skb_queue_empty(&call->recvmsg_queue)) { + list_del_init(&call->recvmsg_link); + spin_unlock(&rx->recvmsg_lock); + release_sock(&rx->sk); + trace_rxrpc_recvmsg(call->debug_id, rxrpc_recvmsg_unqueue, 0); + rxrpc_put_call(call, rxrpc_call_put_recvmsg); + goto try_again; + } + if (!(flags & MSG_PEEK)) list_del_init(&call->recvmsg_link); else @@ -402,7 +415,8 @@ int rxrpc_recvmsg(struct socket *sock, struct msghdr *m= sg, size_t len, if (rxrpc_call_has_failed(call)) goto call_failed; =20 - rxrpc_notify_socket(call); + if (!skb_queue_empty(&call->recvmsg_queue)) + rxrpc_notify_socket(call); goto not_yet_complete; =20 call_failed: