From patchwork Mon Feb 24 23:41:39 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Howells X-Patchwork-Id: 13989085 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 29189207DEA for ; Mon, 24 Feb 2025 23:42:14 +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=1740440537; cv=none; b=HhmpDYYAhUTIlcesxG2khHVuHzd6SEzSF7vRsdBOASIBrAqWWhhI13i6e/uUKQ3Zue+rFqP6D3naGtHY8NxE1SGJjgM9N04b4EMDHE+upg27EK71DinkxPnIL5aw8K673HWb0P1PCGgQjykdfl198Et7VUhTJY64oQC1zeX1MjQ= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740440537; c=relaxed/simple; bh=GAF4rTI1DsGws7r7GRla1/im4tYifATcIPq/nactC60=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Rt35uK51VY1uQNhJbTXPgm5wr7634c52H4fP2euiitqzrQQ/YmdfhEbTet/8k/v2glXUhn+MjWrOTfo0oBMSEIB3oQwuSBMJ3gV5IsDIv7KuYcokvt9i09eTNFbo5zG8AUk+Y7I1vqSXL1urijcWBfenu8cE4/iJG71julUeZoE= 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=Li0nk5Qm; 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="Li0nk5Qm" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1740440533; 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=rJysTY3l6efKg+rxbSyGDPWajwbgdCVI4+yZliqv/jI=; b=Li0nk5QmcHjIjMzsy/JkC2sgWhnNxG3qKjBsze8E+AkTmHjv1y249WNT4DR1Xx1m7e7E0j aKSvyaxJnBiRYC+/V3p+oDjswiEOUS5Ndx11laSII7eOBmoXspJD14Igpz1VQTQpa/y5lx vdrLMQnBqWuXlDGaxsP0TrHF9HSrLsQ= Received: from mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-197-lKJIW5ZiOr-4stc6ovGtfA-1; Mon, 24 Feb 2025 18:42:10 -0500 X-MC-Unique: lKJIW5ZiOr-4stc6ovGtfA-1 X-Mimecast-MFC-AGG-ID: lKJIW5ZiOr-4stc6ovGtfA_1740440529 Received: from mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.93]) (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-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 7ED791800872; Mon, 24 Feb 2025 23:42:09 +0000 (UTC) Received: from warthog.procyon.org.com (unknown [10.42.28.9]) by mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 756B8180035F; Mon, 24 Feb 2025 23:42:06 +0000 (UTC) From: David Howells To: netdev@vger.kernel.org Cc: David Howells , Marc Dionne , Jakub Kicinski , "David S. Miller" , Eric Dumazet , Paolo Abeni , Christian Brauner , linux-afs@lists.infradead.org, linux-kernel@vger.kernel.org, Simon Horman Subject: [PATCH net-next 02/15] rxrpc: peer->mtu_lock is redundant Date: Mon, 24 Feb 2025 23:41:39 +0000 Message-ID: <20250224234154.2014840-3-dhowells@redhat.com> In-Reply-To: <20250224234154.2014840-1-dhowells@redhat.com> References: <20250224234154.2014840-1-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 10.30.177.93 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 throw a complaint: 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;