From patchwork Mon Apr 10 18:06:10 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Blake X-Patchwork-Id: 13206559 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 06222C76196 for ; Mon, 10 Apr 2023 18:07:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230110AbjDJSH3 (ORCPT ); Mon, 10 Apr 2023 14:07:29 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48434 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230443AbjDJSHV (ORCPT ); Mon, 10 Apr 2023 14:07:21 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E08E62717 for ; Mon, 10 Apr 2023 11:06:24 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1681149984; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=oA7vC3IC/UfWw/nU7DhHbrgbZ80ejmkeIuMD8WFpxCo=; b=Ys0iOcxAjIr14afIDUK3EoNyo3GdOFoYt+0aqkxiSxc8S5jMxlWAEpJmpByM0DV4TTh7sZ o9yW9ZkoENTEldKa8THMBw8VhACOTTo6pU89r7Kvz7H62EyeqbbcID51U1fVkUR0QvLA2U BcVzqMi49lfoYXmsflLNcBCcSTS1nkg= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-494-S3Uh7-YpMo2AMJpLLugL-A-1; Mon, 10 Apr 2023 14:06:18 -0400 X-MC-Unique: S3Uh7-YpMo2AMJpLLugL-A-1 Received: from smtp.corp.redhat.com (int-mx09.intmail.prod.int.rdu2.redhat.com [10.11.54.9]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 3822985A5B1; Mon, 10 Apr 2023 18:06:18 +0000 (UTC) Received: from green.redhat.com (unknown [10.2.16.95]) by smtp.corp.redhat.com (Postfix) with ESMTP id 7DA0C492C13; Mon, 10 Apr 2023 18:06:17 +0000 (UTC) From: Eric Blake To: josef@toxicpanda.com, linux-block@vger.kernel.org, nbd@other.debian.org Cc: philipp.reisner@linbit.com, lars.ellenberg@linbit.com, christoph.boehmwalder@linbit.com, corbet@lwn.net, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v3 3/4] block nbd: use req.cookie instead of req.handle Date: Mon, 10 Apr 2023 13:06:10 -0500 Message-Id: <20230410180611.1051618-4-eblake@redhat.com> In-Reply-To: <20230410180611.1051618-1-eblake@redhat.com> References: <20230410180611.1051618-1-eblake@redhat.com> MIME-Version: 1.0 Content-type: text/plain X-Scanned-By: MIMEDefang 3.1 on 10.11.54.9 Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org The NBD spec was recently changed [1] to refer to the opaque client identifier as a 'cookie' rather than a 'handle', but has for a much longer time listed it as a 64-bit value, and declares that all values in the NBD protocol are sent in network byte order (big-endian). Because the value is opaque to the server, it doesn't usually matter what endianness we send as the client - as long as we are consistent that either we byte-swap on both write and read, or on neither, then we can match server replies back to our requests. That said, our internal use of the cookie is as a 64-bit number (well, as two 32-bit numbers concatenated together), rather than as 8 individual bytes; so prior to this commit, we ARE leaking the native endianness of our internals as a client out to the server. We don't know of any server that will actually inspect the opaque value and behave differently depending on whether a little-endian or big-endian client is sending requests, but since we DO log the cookie value, a wireshark capture of the network traffic is easier to correlate back to the kernel traffic of a big-endian host (where the u64 and char[8] representations are the same) than of a little-endian host (where if wireshark honors the NBD spec and displays a u64 in network byte order, it is byte-swapped from what the kernel logged). The fix in this patch is thus two-part: it now consistently uses network byte order for the opaque value (no difference to a big-endian machine, but an extra byteswap on a little-endian machine; probably in the noise compared to the overhead of network traffic in general), and now uses a 64-bit integer instead of char[8] as its preferred access to the opaque value (direct assignment instead of memcpy()). Signed-off-by: Eric Blake Reviewed-by: Josef Bacik --- v3: squash original 2/5 and 4/5 into one patch, to avoid intermediate duplication through a tmp variable [Ming]. Josef's R-b added, since the final outcome of the squash is unchanged. --- drivers/block/nbd.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c index 592cfa8b765a..94ae85400b46 100644 --- a/drivers/block/nbd.c +++ b/drivers/block/nbd.c @@ -606,7 +606,7 @@ static int nbd_send_cmd(struct nbd_device *nbd, struct nbd_cmd *cmd, int index) request.len = htonl(size); } handle = nbd_cmd_handle(cmd); - memcpy(request.handle, &handle, sizeof(handle)); + request.cookie = cpu_to_be64(handle); trace_nbd_send_request(&request, nbd->index, blk_mq_rq_from_pdu(cmd)); @@ -618,7 +618,7 @@ static int nbd_send_cmd(struct nbd_device *nbd, struct nbd_cmd *cmd, int index) trace_nbd_header_sent(req, handle); if (result < 0) { if (was_interrupted(result)) { - /* If we havne't sent anything we can just return BUSY, + /* If we haven't sent anything we can just return BUSY, * however if we have sent something we need to make * sure we only allow this req to be sent until we are * completely done. @@ -732,7 +732,7 @@ static struct nbd_cmd *nbd_handle_reply(struct nbd_device *nbd, int index, u32 tag; int ret = 0; - memcpy(&handle, reply->handle, sizeof(handle)); + handle = be64_to_cpu(reply->cookie); tag = nbd_handle_to_tag(handle); hwq = blk_mq_unique_tag_to_hwq(tag); if (hwq < nbd->tag_set.nr_hw_queues)