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=-3.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS 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 52182C433E0 for ; Tue, 16 Mar 2021 16:18:23 +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 B0B53650FD for ; Tue, 16 Mar 2021 16:18:22 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B0B53650FD Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=yandex-team.ru Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:41710 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lMCOj-0007to-QE for qemu-devel@archiver.kernel.org; Tue, 16 Mar 2021 12:18:21 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:38640) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lMCFD-0006ff-Gq; Tue, 16 Mar 2021 12:08:33 -0400 Received: from forwardcorp1j.mail.yandex.net ([5.45.199.163]:57518) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lMCF7-0004Cb-G1; Tue, 16 Mar 2021 12:08:29 -0400 Received: from iva8-d077482f1536.qloud-c.yandex.net (iva8-d077482f1536.qloud-c.yandex.net [IPv6:2a02:6b8:c0c:2f26:0:640:d077:482f]) by forwardcorp1j.mail.yandex.net (Yandex) with ESMTP id 3D2A62E1631; Tue, 16 Mar 2021 19:08:19 +0300 (MSK) Received: from iva4-f06c35e68a0a.qloud-c.yandex.net (iva4-f06c35e68a0a.qloud-c.yandex.net [2a02:6b8:c0c:152e:0:640:f06c:35e6]) by iva8-d077482f1536.qloud-c.yandex.net (mxbackcorp/Yandex) with ESMTP id XIQteJaG60-8F0SDKNp; Tue, 16 Mar 2021 19:08:19 +0300 Precedence: bulk DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yandex-team.ru; s=default; t=1615910899; bh=ceqrQ/RafpeRjEmwXtioHLb1J1XT++0JQqci/qcboR0=; h=In-Reply-To:Message-ID:Subject:To:From:Cc:References:Date; b=uK2LTj76Q3PS/Oolhp0kYC7hDWbB7e+EbhKurIy5mbObPY1rilnvvj0qS/bnuu4Aq D3NmfVs6PSxR3w2VWOwTk5za3e06kEcgF081Ne2ofI8551GT34697ewIZeoxrvSSj+ qizthkznZc+5xbpBu0KPLsfj2gJCGpnb261/GZ54= Authentication-Results: iva8-d077482f1536.qloud-c.yandex.net; dkim=pass header.i=@yandex-team.ru Received: from dynamic-iva.dhcp.yndx.net (dynamic-iva.dhcp.yndx.net [2a02:6b8:b080:8817::1:e]) by iva4-f06c35e68a0a.qloud-c.yandex.net (smtpcorp/Yandex) with ESMTPSA id xtUhbkAfI5-8Fni9DZE; Tue, 16 Mar 2021 19:08:15 +0300 (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)) (Client certificate not present) Date: Tue, 16 Mar 2021 19:08:13 +0300 From: Roman Kagan To: Vladimir Sementsov-Ogievskiy Subject: Re: [PATCH 7/7] block/nbd: stop manipulating in_flight counter Message-ID: Mail-Followup-To: Roman Kagan , Vladimir Sementsov-Ogievskiy , qemu-devel@nongnu.org, yc-core@yandex-team.ru, Eric Blake , Max Reitz , Kevin Wolf , qemu-block@nongnu.org References: <20210315060611.2989049-1-rvkagan@yandex-team.ru> <20210315060611.2989049-8-rvkagan@yandex-team.ru> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Received-SPF: pass client-ip=5.45.199.163; envelope-from=rvkagan@yandex-team.ru; helo=forwardcorp1j.mail.yandex.net X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kevin Wolf , qemu-block@nongnu.org, qemu-devel@nongnu.org, Max Reitz , yc-core@yandex-team.ru Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Mon, Mar 15, 2021 at 11:15:44PM +0300, Vladimir Sementsov-Ogievskiy wrote: > 15.03.2021 09:06, Roman Kagan wrote: > > As the reconnect logic no longer interferes with drained sections, it > > appears unnecessary to explicitly manipulate the in_flight counter. > > > > Fixes: 5ad81b4946 ("nbd: Restrict connection_co reentrance") > > And here you actually allow qemu_aio_coroutine_enter() call in > nbd_client_attach_aio_context_bh() to enter connection_co in any yield > point which is possible during drained section. The analysis should be > done to be sure that all these yield points are safe for reentering by > external qemu_aio_coroutine_enter(). (By external I mean not by the > actual enter() we are waiting for at the yield() point. For example > qemu_channel_yield() supports reentering.. And therefore (as I > understand after fast looking through) nbd_read() should support > reentering too.. I'll do a more thorough analysis of how safe it is. FWIW this hasn't triggered any test failures yet, but that assert in patch 3 didn't ever go off either so I'm not sure I can trust the tests on this. Thanks, Roman.