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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id D9CE9C4332F for ; Thu, 10 Nov 2022 17:47:07 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1otBdJ-0001Da-09; Thu, 10 Nov 2022 12:46:33 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1otBdH-0001D7-6d for qemu-devel@nongnu.org; Thu, 10 Nov 2022 12:46:31 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1otBdF-0005DG-9d for qemu-devel@nongnu.org; Thu, 10 Nov 2022 12:46:30 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1668102388; 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=gNSXoGsb1MyjjZh3k3wUX/1a0zqzZ3ELTDM0moh8/ho=; b=I2Z6ecAbcqu0nVV3XFv5Isr4kFnF82MrD7zRTm4cSrSixHLNFQYcH2zUqxjnTUWd2jGb+X YHnYKdaND84vVrr4HDJMLr54aXQSV15FTA0sImAmNhrDb6W6BzBPu3CX+5h3w5mNGdevL9 LLlvykEB2LTgTz4JEe3iY7c2SvXxf8o= 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-260-vT2wlnqFOGmWZY6piEHuuw-1; Thu, 10 Nov 2022 12:46:25 -0500 X-MC-Unique: vT2wlnqFOGmWZY6piEHuuw-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.rdu2.redhat.com [10.11.54.1]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 17C8C185A79C; Thu, 10 Nov 2022 17:46:25 +0000 (UTC) Received: from redhat.com (unknown [10.39.195.15]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 53EA640C83DF; Thu, 10 Nov 2022 17:46:24 +0000 (UTC) Date: Thu, 10 Nov 2022 18:46:23 +0100 From: Kevin Wolf To: Hanna Reitz Cc: qemu-block@nongnu.org, qemu-devel@nongnu.org, Stefan Hajnoczi Subject: Re: [PATCH v2 0/3] block: Start/end drain on correct AioContext Message-ID: References: <20221107151321.211175-1-hreitz@redhat.com> <4b94c12a-13d3-67a0-f46b-631c40e2b2cb@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <4b94c12a-13d3-67a0-f46b-631c40e2b2cb@redhat.com> X-Scanned-By: MIMEDefang 3.1 on 10.11.54.1 Received-SPF: pass client-ip=170.10.133.124; envelope-from=kwolf@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, 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=-0.001, 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: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Am 10.11.2022 um 17:11 hat Hanna Reitz geschrieben: > On 10.11.22 15:01, Kevin Wolf wrote: > > Am 07.11.2022 um 16:13 hat Hanna Reitz geschrieben: > > > Hi, > > > > > > v1 cover letter: > > > https://lists.nongnu.org/archive/html/qemu-block/2022-09/msg00389.html > > > > > > bdrv_replace_child_noperm() drains the child via > > > bdrv_parent_drained_{begin,end}_single(). When it removes a child, the > > > bdrv_parent_drained_end_single() at its end will be called on an empty > > > child, making the BDRV_POLL_WHILE() in it poll the main AioContext > > > (because c->bs is NULL). > > > > > > That’s wrong, though, because it’s supposed to operate on the parent. > > > bdrv_parent_drained_end_single_no_poll() will have scheduled any BHs in > > > the parents’ AioContext, which may be anything, not necessarily the main > > > context. Therefore, we must poll the parent’s context. > > > > > > Patch 3 does this for both bdrv_parent_drained_{begin,end}_single(). > > > Patch 1 ensures that we can legally call > > > bdrv_child_get_parent_aio_context() from those I/O context functions, > > > and patch 2 fixes blk_do_set_aio_context() to not cause an assertion > > > failure if it beginning a drain can end up in blk_get_aio_context() > > > before blk->ctx has been updated. > > Thanks, applied to the block branch. > > Thanks! > > I tested your drain series, and it does indeed fix the bug, too. > (Sorry for the delay, I thought it’d take less time to write an > iotest...) Thanks for testing, it's good to have this confirmed. > > I would still be interested in a test case as a follow-up. > > Got it working now and sent as “tests/stream-under-throttle: New test”. Great! I'll take a look. Kevin