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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,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 BD313C7618B for ; Thu, 25 Jul 2019 17:06:56 +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 93A86217D4 for ; Thu, 25 Jul 2019 17:06:56 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 93A86217D4 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]:34144 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hqhCh-0004UE-Qs for qemu-devel@archiver.kernel.org; Thu, 25 Jul 2019 13:06:55 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:57717) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hqhCV-00045o-Kq for qemu-devel@nongnu.org; Thu, 25 Jul 2019 13:06:44 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hqhCU-0001HK-F2 for qemu-devel@nongnu.org; Thu, 25 Jul 2019 13:06:43 -0400 Received: from mx1.redhat.com ([209.132.183.28]:45128) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hqhCN-0001Dl-O1; Thu, 25 Jul 2019 13:06:36 -0400 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id D7FD130C62A3; Thu, 25 Jul 2019 17:06:33 +0000 (UTC) Received: from [10.3.116.93] (ovpn-116-93.phx2.redhat.com [10.3.116.93]) by smtp.corp.redhat.com (Postfix) with ESMTPS id E558C620CE; Thu, 25 Jul 2019 17:06:29 +0000 (UTC) To: Kevin Wolf , qemu-block@nongnu.org References: <20190725162704.12622-1-kwolf@redhat.com> <20190725162704.12622-5-kwolf@redhat.com> From: Eric Blake Openpgp: preference=signencrypt Autocrypt: addr=eblake@redhat.com; keydata= xsBNBEvHyWwBCACw7DwsQIh0kAbUXyqhfiKAKOTVu6OiMGffw2w90Ggrp4bdVKmCaEXlrVLU xphBM8mb+wsFkU+pq9YR621WXo9REYVIl0FxKeQo9dyQBZ/XvmUMka4NOmHtFg74nvkpJFCD TUNzmqfcjdKhfFV0d7P/ixKQeZr2WP1xMcjmAQY5YvQ2lUoHP43m8TtpB1LkjyYBCodd+LkV GmCx2Bop1LSblbvbrOm2bKpZdBPjncRNob73eTpIXEutvEaHH72LzpzksfcKM+M18cyRH+nP sAd98xIbVjm3Jm4k4d5oQyE2HwOur+trk2EcxTgdp17QapuWPwMfhaNq3runaX7x34zhABEB AAHNHkVyaWMgQmxha2UgPGVibGFrZUByZWRoYXQuY29tPsLAegQTAQgAJAIbAwULCQgHAwUV CgkICwUWAgMBAAIeAQIXgAUCS8fL9QIZAQAKCRCnoWtKJSdDahBHCACbl/5FGkUqJ89GAjeX RjpAeJtdKhujir0iS4CMSIng7fCiGZ0fNJCpL5RpViSo03Q7l37ss+No+dJI8KtAp6ID+PMz wTJe5Egtv/KGUKSDvOLYJ9WIIbftEObekP+GBpWP2+KbpADsc7EsNd70sYxExD3liwVJYqLc Rw7so1PEIFp+Ni9A1DrBR5NaJBnno2PHzHPTS9nmZVYm/4I32qkLXOcdX0XElO8VPDoVobG6 gELf4v/vIImdmxLh/w5WctUpBhWWIfQDvSOW2VZDOihm7pzhQodr3QP/GDLfpK6wI7exeu3P pfPtqwa06s1pae3ad13mZGzkBdNKs1HEm8x6zsBNBEvHyWwBCADGkMFzFjmmyqAEn5D+Mt4P zPdO8NatsDw8Qit3Rmzu+kUygxyYbz52ZO40WUu7EgQ5kDTOeRPnTOd7awWDQcl1gGBXgrkR pAlQ0l0ReO57Q0eglFydLMi5bkwYhfY+TwDPMh3aOP5qBXkm4qIYSsxb8A+i00P72AqFb9Q7 3weG/flxSPApLYQE5qWGSXjOkXJv42NGS6o6gd4RmD6Ap5e8ACo1lSMPfTpGzXlt4aRkBfvb NCfNsQikLZzFYDLbQgKBA33BDeV6vNJ9Cj0SgEGOkYyed4I6AbU0kIy1hHAm1r6+sAnEdIKj cHi3xWH/UPrZW5flM8Kqo14OTDkI9EtlABEBAAHCwF8EGAEIAAkFAkvHyWwCGwwACgkQp6Fr SiUnQ2q03wgAmRFGDeXzc58NX0NrDijUu0zx3Lns/qZ9VrkSWbNZBFjpWKaeL1fdVeE4TDGm I5mRRIsStjQzc2R9b+2VBUhlAqY1nAiBDv0Qnt+9cLiuEICeUwlyl42YdwpmY0ELcy5+u6wz mK/jxrYOpzXKDwLq5k4X+hmGuSNWWAN3gHiJqmJZPkhFPUIozZUCeEc76pS/IUN72NfprZmF Dp6/QDjDFtfS39bHSWXKVZUbqaMPqlj/z6Ugk027/3GUjHHr8WkeL1ezWepYDY7WSoXwfoAL 2UXYsMAr/uUncSKlfjvArhsej0S4zbqim2ZY6S8aRWw94J3bSvJR+Nwbs34GPTD4Pg== Organization: Red Hat, Inc. Message-ID: Date: Thu, 25 Jul 2019 12:06:28 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: <20190725162704.12622-5-kwolf@redhat.com> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="aHNY1txYP3ICKVYuR6MnnVlputHCjbPZd" X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.46]); Thu, 25 Jul 2019 17:06:33 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: Re: [Qemu-devel] [PATCH 4/4] block-backend: Queue requests while drained 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: dplotnikov@virtuozzo.com, vsementsov@virtuozzo.com, den@virtuozzo.com, mreitz@redhat.com, qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --aHNY1txYP3ICKVYuR6MnnVlputHCjbPZd Content-Type: multipart/mixed; boundary="0dukJQ0Sg8RDpQQ8a9LvE9NNuICnNWOqs"; protected-headers="v1" From: Eric Blake To: Kevin Wolf , qemu-block@nongnu.org Cc: vsementsov@virtuozzo.com, den@virtuozzo.com, qemu-devel@nongnu.org, mreitz@redhat.com, dplotnikov@virtuozzo.com Message-ID: Subject: Re: [Qemu-devel] [PATCH 4/4] block-backend: Queue requests while drained References: <20190725162704.12622-1-kwolf@redhat.com> <20190725162704.12622-5-kwolf@redhat.com> In-Reply-To: <20190725162704.12622-5-kwolf@redhat.com> --0dukJQ0Sg8RDpQQ8a9LvE9NNuICnNWOqs Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 7/25/19 11:27 AM, Kevin Wolf wrote: > This fixes device like IDE that can still start new requests from I/O > handlers in the CPU thread while the block backend is drained. >=20 > The basic assumption is that in a drain section, no new requests should= > be allowed through a BlockBackend (blk_drained_begin/end don't exist, > we get drain sections only on the node level). However, there are two > special cases where requests should not be queued: >=20 > 1. Block jobs: We already make sure that block jobs are paused in a > drain section, so they won't start new requests. However, if the > drain_begin is called on the job's BlockBackend first, it can happen= > that we deadlock because the job stays busy until it reaches a pause= > point - which it can't if it's requests aren't processed any more. its (remember, "it's" is only okay if "it is" works as well) >=20 > The proper solution here would be to make all requests through the > job's filter node instead of using a BlockBackend. For now, just > disabling request queuin on the job BlockBackend is simpler. queuing >=20 > 2. In test cases where making requests through bdrv_* would be > cumbersome because we'd need a BdrvChild. As we already got the > functionality to disable request queuing from 1., use it in tests, > too, for convenience. >=20 --=20 Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3226 Virtualization: qemu.org | libvirt.org --0dukJQ0Sg8RDpQQ8a9LvE9NNuICnNWOqs-- --aHNY1txYP3ICKVYuR6MnnVlputHCjbPZd Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEccLMIrHEYCkn0vOqp6FrSiUnQ2oFAl054ZUACgkQp6FrSiUn Q2rWqggAqjYtBhIUeprgo/ygGsHE1X+8UETKqAH279EMZzDxrRsllvXNji7kAmJz J2YcQ6u8PriWinoQBd2URspLq0bpb+943vX4zl0osO/sncWOYWvNS8hEjIKPMcT0 k2EN/oT8rLrJf/oQ/kOeVsdbZAhHrKAUJTWqp2QZyvfpDxHENqfAqgKRffBsj0IK cJJqu85wRm4dTz2HluSbHUY8GHwXiO2Rk/Ud3B9oNn6Rf+R1E1hpb4+eDlq6etpm b16OXlDIbaet1Em6WY33DFIFfhjoffNwUQKbXT8frSwthzeq6hnGCs7FfibF9Zmc VNSq5NY/3PO5qZYo/Xly9TLsLBByYg== =p16F -----END PGP SIGNATURE----- --aHNY1txYP3ICKVYuR6MnnVlputHCjbPZd--