From patchwork Tue Feb 18 19:22:45 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Howells X-Patchwork-Id: 13980654 X-Patchwork-Delegate: kuba@kernel.org Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0379721B9C7 for ; Tue, 18 Feb 2025 19:23:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739906593; cv=none; b=syb0wJR7CM/sPb0mldwKzlHXGn3CwVJWP/7MLhscfsbc2RbcL0cyh1H9A3nTt2Q5r4hLN8cOPiYnPdh5fc0qNwY6ohdkY5Pt8Ls3jw70MGeaGCrtSmWXIrYzkU2sj/Ic8SOC4rB8LlnkSTzJN1lg4ZqXizSf4TQflp7a9Sk09w8= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739906593; c=relaxed/simple; bh=54+1wSTWK34HQr0H/R006mkjjB9f/D+FONo/jgiEPf8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=IZG3KfZ7ZgGeeV1qhJ9JkkpEGuYriOFiKSDhjatbTAyA3IQ8mSGpCsj/UyI2lkiGF1/hJcHC7pKf1bZIZeqihvCVE2B4fhwMiFyvyUURGfUR9Hgownr2G817aeZqN0/5S+jFCyHMl6QJyO14qXaFi/jq5tmWY0Zf7fNvLGWyU2c= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=U8pqrClL; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="U8pqrClL" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1739906590; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=3BBat5EO7Q9cBS+sJTTtoikXXonGuQ1MFgftGhda40Q=; b=U8pqrClLEHqZvifjqhOi36WmJbwNGBVoO5fdkaZyyitvZ2Amp/BBpVxtVpfOd80w3zuJHL qj2LCGn3BuXdVNnO+2iIIc7VsGOrvAdZBJgO0ztviGj7m7dfvsZxx572Iq6FMkprlzxwan quplC4TsMoaCGUCpEX7rybHnqKtZ6Ww= Received: from mx-prod-mc-01.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-677-22pJpuW7PPuXM6-9ovXNoA-1; Tue, 18 Feb 2025 14:23:06 -0500 X-MC-Unique: 22pJpuW7PPuXM6-9ovXNoA-1 X-Mimecast-MFC-AGG-ID: 22pJpuW7PPuXM6-9ovXNoA_1739906585 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 45F4F19783B7; Tue, 18 Feb 2025 19:23:05 +0000 (UTC) Received: from warthog.procyon.org.com (unknown [10.42.28.9]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id D8D8D180034D; Tue, 18 Feb 2025 19:23:01 +0000 (UTC) From: David Howells To: netdev@vger.kernel.org Cc: David Howells , Marc Dionne , Jakub Kicinski , "David S. Miller" , Eric Dumazet , Paolo Abeni , linux-afs@lists.infradead.org, linux-kernel@vger.kernel.org, Simon Horman Subject: [PATCH net 2/5] rxrpc: peer->mtu_lock is redundant Date: Tue, 18 Feb 2025 19:22:45 +0000 Message-ID: <20250218192250.296870-3-dhowells@redhat.com> In-Reply-To: <20250218192250.296870-1-dhowells@redhat.com> References: <20250218192250.296870-1-dhowells@redhat.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 X-Patchwork-Delegate: kuba@kernel.org The peer->mtu_lock is only used to lock around writes to peer->max_data - and nothing else; further, all such writes take place in the I/O thread and the lock is only ever write-locked and never read-locked. In a couple of places, the write_seqcount_begin() is wrapped in preempt_disable/enable(), but not in all places. This can cause lockdep to complain: WARNING: CPU: 0 PID: 1549 at include/linux/seqlock.h:221 rxrpc_input_ack_trailer+0x305/0x430 ... RIP: 0010:rxrpc_input_ack_trailer+0x305/0x430 Fix this by just getting rid of the lock. Fixes: eeaedc5449d9 ("rxrpc: Implement path-MTU probing using padded PING ACKs (RFC8899)") Signed-off-by: David Howells cc: Marc Dionne cc: Jakub Kicinski cc: "David S. Miller" cc: Eric Dumazet cc: Paolo Abeni cc: Simon Horman cc: linux-afs@lists.infradead.org cc: netdev@vger.kernel.org --- net/rxrpc/ar-internal.h | 1 - net/rxrpc/input.c | 2 -- net/rxrpc/peer_event.c | 9 +-------- net/rxrpc/peer_object.c | 1 - 4 files changed, 1 insertion(+), 12 deletions(-) diff --git a/net/rxrpc/ar-internal.h b/net/rxrpc/ar-internal.h index 5e740c486203..a64a0cab1bf7 100644 --- a/net/rxrpc/ar-internal.h +++ b/net/rxrpc/ar-internal.h @@ -360,7 +360,6 @@ struct rxrpc_peer { u8 pmtud_jumbo; /* Max jumbo packets for the MTU */ bool ackr_adv_pmtud; /* T if the peer advertises path-MTU */ unsigned int ackr_max_data; /* Maximum data advertised by peer */ - seqcount_t mtu_lock; /* Lockless MTU access management */ unsigned int if_mtu; /* Local interface MTU (- hdrsize) for this peer */ unsigned int max_data; /* Maximum packet data capacity for this peer */ unsigned short hdrsize; /* header size (IP + UDP + RxRPC) */ diff --git a/net/rxrpc/input.c b/net/rxrpc/input.c index 9047ba13bd31..24aceb183c2c 100644 --- a/net/rxrpc/input.c +++ b/net/rxrpc/input.c @@ -810,9 +810,7 @@ static void rxrpc_input_ack_trailer(struct rxrpc_call *call, struct sk_buff *skb if (max_mtu < peer->max_data) { trace_rxrpc_pmtud_reduce(peer, sp->hdr.serial, max_mtu, rxrpc_pmtud_reduce_ack); - write_seqcount_begin(&peer->mtu_lock); peer->max_data = max_mtu; - write_seqcount_end(&peer->mtu_lock); } max_data = umin(max_mtu, peer->max_data); diff --git a/net/rxrpc/peer_event.c b/net/rxrpc/peer_event.c index bc283da9ee40..7f4729234957 100644 --- a/net/rxrpc/peer_event.c +++ b/net/rxrpc/peer_event.c @@ -130,9 +130,7 @@ static void rxrpc_adjust_mtu(struct rxrpc_peer *peer, unsigned int mtu) peer->pmtud_bad = max_data + 1; trace_rxrpc_pmtud_reduce(peer, 0, max_data, rxrpc_pmtud_reduce_icmp); - write_seqcount_begin(&peer->mtu_lock); peer->max_data = max_data; - write_seqcount_end(&peer->mtu_lock); } } @@ -408,13 +406,8 @@ void rxrpc_input_probe_for_pmtud(struct rxrpc_connection *conn, rxrpc_serial_t a } max_data = umin(max_data, peer->ackr_max_data); - if (max_data != peer->max_data) { - preempt_disable(); - write_seqcount_begin(&peer->mtu_lock); + if (max_data != peer->max_data) peer->max_data = max_data; - write_seqcount_end(&peer->mtu_lock); - preempt_enable(); - } jumbo = max_data + sizeof(struct rxrpc_jumbo_header); jumbo /= RXRPC_JUMBO_SUBPKTLEN; diff --git a/net/rxrpc/peer_object.c b/net/rxrpc/peer_object.c index 0fcc87f0409f..2ddc8ed68742 100644 --- a/net/rxrpc/peer_object.c +++ b/net/rxrpc/peer_object.c @@ -235,7 +235,6 @@ struct rxrpc_peer *rxrpc_alloc_peer(struct rxrpc_local *local, gfp_t gfp, peer->service_conns = RB_ROOT; seqlock_init(&peer->service_conn_lock); spin_lock_init(&peer->lock); - seqcount_init(&peer->mtu_lock); peer->debug_id = atomic_inc_return(&rxrpc_debug_id); peer->recent_srtt_us = UINT_MAX; peer->cong_ssthresh = RXRPC_TX_MAX_WINDOW;