From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.4 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 919F5C433E1 for ; Wed, 19 Aug 2020 19:34:27 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 61C26207BB for ; Wed, 19 Aug 2020 19:34:27 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="V0r6seC0" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 61C26207BB Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:49210 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1k8Tqs-0004X1-Lj for qemu-devel@archiver.kernel.org; Wed, 19 Aug 2020 15:34:26 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:47808) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1k8TqC-0003m3-Jn for qemu-devel@nongnu.org; Wed, 19 Aug 2020 15:33:44 -0400 Received: from us-smtp-1.mimecast.com ([207.211.31.81]:20994 helo=us-smtp-delivery-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1k8Tq9-0001Z2-3D for qemu-devel@nongnu.org; Wed, 19 Aug 2020 15:33:44 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1597865619; 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=n8gYDUhf1ZlJOPVEZPjAfjw1s+gDKRXRueaC6mAZQLo=; b=V0r6seC041b3oAUXhdMjz6rwfJvmThLkttDzO1XDkOfgPHH/OSHiD9ABpShbFQMGWexysi vjQDfqllCQNgN/d+oxYtsESCJoANpqeg6LZ//ziQ3xfCR5nUKo4WVMCynOJY3Ahtpnn22a ReH1sq0kwsrpliuXTbnd5f8vVwxcalo= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-395-9OP0q50hPbOMG8RT3N94pw-1; Wed, 19 Aug 2020 15:33:38 -0400 X-MC-Unique: 9OP0q50hPbOMG8RT3N94pw-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 392B964080; Wed, 19 Aug 2020 19:33:37 +0000 (UTC) Received: from [10.3.112.136] (ovpn-112-136.phx2.redhat.com [10.3.112.136]) by smtp.corp.redhat.com (Postfix) with ESMTPS id CAA0526DD4; Wed, 19 Aug 2020 19:33:36 +0000 (UTC) Subject: Re: [RFC PATCH 06/22] qemu-nbd: Use raw block driver for --offset To: Kevin Wolf , qemu-block@nongnu.org References: <20200813162935.210070-1-kwolf@redhat.com> <20200813162935.210070-7-kwolf@redhat.com> From: Eric Blake Organization: Red Hat, Inc. Message-ID: <4f9e0b0e-3f70-6237-86b3-c43c29847a0d@redhat.com> Date: Wed, 19 Aug 2020 14:33:36 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 MIME-Version: 1.0 In-Reply-To: <20200813162935.210070-7-kwolf@redhat.com> Content-Language: en-US X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=eblake@redhat.com X-Mimecast-Spam-Score: 0.002 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=207.211.31.81; envelope-from=eblake@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/08/19 01:46:53 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -40 X-Spam_score: -4.1 X-Spam_bar: ---- X-Spam_report: (-4.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-1, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: qemu-devel@nongnu.org, mreitz@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 8/13/20 11:29 AM, Kevin Wolf wrote: > Instead of implementing qemu-nbd --offset in the NBD code, just put a > raw block node with the requested offset on top of the user image and > rely on that doing the job. > > This does not only simplify the nbd_export_new() interface and bring it > closer to the set of options that the nbd-server-add QMP command offers, > but in fact it also eliminates a potential source for bugs in the NBD > code which previously had to add the offset manually in all relevant > places. Yay! This patch alone is worth having, regardless of the fate of the rest of the series: no change in end-user functionality, but by making qemu-nbd turn it into proper syntactic sugar, we've reduced the maintenance burden of duplicated code. > > Signed-off-by: Kevin Wolf > --- > include/block/nbd.h | 4 ++-- > blockdev-nbd.c | 9 +-------- > nbd/server.c | 34 +++++++++++++++++----------------- > qemu-nbd.c | 27 ++++++++++++--------------- > 4 files changed, 32 insertions(+), 42 deletions(-) > > +++ b/nbd/server.c > @@ -89,7 +89,6 @@ struct NBDExport { > BlockBackend *blk; > char *name; > char *description; > - uint64_t dev_offset; > uint64_t size; I'm trying to figure out if we can also drop 'size' here. If we do, the consequence would be that an NBD client could ask for beyond-EOF I/O, and presumably the block layer would reject that gracefully (although not necessarily with the same errno as NBD currently reports). I'm fine leaving it alone in this patch, though. > @@ -1569,7 +1574,7 @@ NBDExport *nbd_export_new(BlockDriverState *bs, uint64_t dev_offset, > exp->nbdflags |= (NBD_FLAG_SEND_TRIM | NBD_FLAG_SEND_WRITE_ZEROES | > NBD_FLAG_SEND_FAST_ZERO); > } > - assert(size <= INT64_MAX - dev_offset); > + assert(size <= INT64_MAX); As Max caught, this is now dead code. > @@ -2386,8 +2388,7 @@ static coroutine_fn int nbd_handle_request(NBDClient *client, > if (request->flags & NBD_CMD_FLAG_FAST_ZERO) { > flags |= BDRV_REQ_NO_FALLBACK; > } > - ret = blk_pwrite_zeroes(exp->blk, request->from + exp->dev_offset, > - request->len, flags); > + ret = blk_pwrite_zeroes(exp->blk, request->from, request->len, flags); > return nbd_send_generic_reply(client, request->handle, ret, > "writing to file failed", errp); > > @@ -2401,8 +2402,7 @@ static coroutine_fn int nbd_handle_request(NBDClient *client, > "flush failed", errp); > > case NBD_CMD_TRIM: > - ret = blk_co_pdiscard(exp->blk, request->from + exp->dev_offset, > - request->len); > + ret = blk_co_pdiscard(exp->blk, request->from, request->len); Merge conflicts with 890cbccb08; should be obvious enough to resolve, though. > +++ b/qemu-nbd.c > @@ -523,7 +523,6 @@ int main(int argc, char **argv) > const char *port = NULL; > char *sockpath = NULL; > char *device = NULL; > - int64_t fd_size; > QemuOpts *sn_opts = NULL; > const char *sn_id_or_name = NULL; > const char *sopt = "hVb:o:p:rsnc:dvk:e:f:tl:x:T:D:B:L"; > @@ -1028,6 +1027,17 @@ int main(int argc, char **argv) > } > bs = blk_bs(blk); > > + if (dev_offset) { > + QDict *raw_opts = qdict_new(); > + qdict_put_str(raw_opts, "driver", "raw"); > + qdict_put_str(raw_opts, "file", bs->node_name); > + qdict_put_int(raw_opts, "offset", dev_offset); Huh. When 0bc16997f5 got rid of the --partition option, it also got rid of the only way that the NBD driver could clamp down requests to a range smaller than the end of the file. Now that you are adding a raw driver in the mix, that ability to clamp the end of the range (aka a --size option, in addition to an --offset option) may be worth reinstating. But that can be done as a separate patch, if at all (and whether qemu-nbd should do it, or qemu-storage-daemon, or whether we just point people at 'nbdkit --filter=partition', is part of that discussion). But for this patch, it looks like you are making a straight-across conversion. > + bs = bdrv_open(NULL, NULL, raw_opts, flags, &error_fatal); > + blk_remove_bs(blk); > + blk_insert_bs(blk, bs, &error_fatal); > + bdrv_unref(bs); > + } > + Slick. Reviewed-by: Eric Blake -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3226 Virtualization: qemu.org | libvirt.org