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=-7.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=no 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 B3A3FC433E0 for ; Thu, 23 Jul 2020 11:48:18 +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 7D7532080D for ; Thu, 23 Jul 2020 11:48:18 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="N8gp5GXb" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7D7532080D 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]:40204 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jyZhx-0002Q5-MB for qemu-devel@archiver.kernel.org; Thu, 23 Jul 2020 07:48:17 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:47208) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jyZhA-0001ni-IC for qemu-devel@nongnu.org; Thu, 23 Jul 2020 07:47:28 -0400 Received: from us-smtp-2.mimecast.com ([205.139.110.61]:42554 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 1jyZh8-0004HG-OX for qemu-devel@nongnu.org; Thu, 23 Jul 2020 07:47:28 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1595504846; 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=aw+utQchIAaOyMZYkIyk21M/hJdTe+EMHO96H0dBMz8=; b=N8gp5GXb9UDWJJGyiCk+Nve3svbU4l3/InOlRHxxVNH6/0Zi58J/IEttpcsCJ6Wfa6T4na lfsS+gfsykJB1JRr9i5M8f5+STXhVLnbQAE2BC+lQPnQJ2Lxs2Mh0nr/WKVtbGVKVEnko+ MtiL88ljo6NFt1CdM76fd76b6HyOc2g= 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-378-oyfBWoJ-MdO13pv6TlV4Ow-1; Thu, 23 Jul 2020 07:47:20 -0400 X-MC-Unique: oyfBWoJ-MdO13pv6TlV4Ow-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 597CA8005B0; Thu, 23 Jul 2020 11:47:19 +0000 (UTC) Received: from [10.3.112.189] (ovpn-112-189.phx2.redhat.com [10.3.112.189]) by smtp.corp.redhat.com (Postfix) with ESMTPS id C2BC15F7D8; Thu, 23 Jul 2020 11:47:18 +0000 (UTC) Subject: Re: [PATCH for-5.1] nbd: Fix large trim/zero requests To: Vladimir Sementsov-Ogievskiy , qemu-devel@nongnu.org References: <20200722212231.535072-1-eblake@redhat.com> From: Eric Blake Organization: Red Hat, Inc. Message-ID: Date: Thu, 23 Jul 2020 06:47:18 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=205.139.110.61; envelope-from=eblake@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/07/23 02:33:29 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-stable@nongnu.org, "open list:Network Block Dev..." Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 7/23/20 2:23 AM, Vladimir Sementsov-Ogievskiy wrote: > 23.07.2020 00:22, Eric Blake wrote: >> Although qemu as NBD client limits requests to <2G, the NBD protocol >> allows clients to send requests almost all the way up to 4G.  But >> because our block layer is not yet 64-bit clean, we accidentally wrap >> such requests into a negative size, and fail with EIO instead of >> performing the intended operation. >> >> @@ -2378,8 +2378,17 @@ 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 = 0; >> +        /* FIXME simplify this when blk_pwrite_zeroes switches to >> 64-bit */ >> +        while (ret == 0 && request->len) { >> +            int align = client->check_align ?: 1; >> +            int len = MIN(request->len, >> QEMU_ALIGN_DOWN(BDRV_REQUEST_MAX_BYTES, >> +                                                        align)); >> +            ret = blk_pwrite_zeroes(exp->blk, request->from + >> exp->dev_offset, >> +                                    len, flags); >> +            request->len -= len; >> +            request->from += len; >> +        } >>           return nbd_send_generic_reply(client, request->handle, ret, >>                                         "writing to file failed", errp); It's easy enough to audit that blk_pwrite_zeroes returns 0 (and not arbitrary positive) on success. >> >> @@ -2393,8 +2402,17 @@ 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 = 0; >> +        /* FIXME simplify this when blk_co_pdiscard switches to >> 64-bit */ >> +        while (ret == 0 && request->len) { > > Did you check all the paths not to return positive ret on success? I'd > prefer to compare ret >= 0 for this temporary code to not care of it And for blk_co_pdiscard, the audit is already right here in the patch: pre-patch, ret = blk_co_pdiscard, followed by... > >> +            int align = client->check_align ?: 1; >> +            int len = MIN(request->len, >> QEMU_ALIGN_DOWN(BDRV_REQUEST_MAX_BYTES, >> +                                                        align)); >> +            ret = blk_co_pdiscard(exp->blk, request->from + >> exp->dev_offset, >> +                                  len); >> +            request->len -= len; >> +            request->from += len; > > Hmm.. Modifying the function parameter. Safe now, as > nbd_handle_request() call is the last usage of request in nbd_trip(). > >> +        } >>           if (ret == 0 && request->flags & NBD_CMD_FLAG_FUA) { ...a check for ret == 0. >>               ret = blk_co_flush(exp->blk); >>           } >> > > Yes, I can respin the patch to use >= 0 as the check for success in both functions, but it doesn't change the behavior. -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3226 Virtualization: qemu.org | libvirt.org