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 E7BBAC5475B for ; Wed, 6 Mar 2024 09:26:18 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1rhnWt-0003rA-Ia; Wed, 06 Mar 2024 04:25:39 -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 1rhnWo-0003qg-Bb for qemu-devel@nongnu.org; Wed, 06 Mar 2024 04:25:35 -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 1rhnWm-00064x-Ox for qemu-devel@nongnu.org; Wed, 06 Mar 2024 04:25:34 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1709717132; h=from:from:reply-to: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=uKphg01lTWlRZH23K5sQIL7CoOAMCBi2VcuV4zcTz5E=; b=jM5UCZj+B62tghsM8nwYifHWIjLKQZUCRhH7zHUhBFUP6uqBHPwbCN8+SKZ6LRzf/4fSY8 k0F4BDDqDQ7PGrLCWVYV+dytsbClLKNIsfiLeUbaiEaskaI/vcf5JQnwyDroNowcj5P6PY Cc3Y1aHGiuQJFQ2LV3p4oU7j5Xu7dzE= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-262-Rc-krxP2NDK1UhhTI2uAbQ-1; Wed, 06 Mar 2024 04:25:28 -0500 X-MC-Unique: Rc-krxP2NDK1UhhTI2uAbQ-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.rdu2.redhat.com [10.11.54.3]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 256A0800265; Wed, 6 Mar 2024 09:25:28 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.115]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 076E1111DCFF; Wed, 6 Mar 2024 09:25:26 +0000 (UTC) Date: Wed, 6 Mar 2024 09:25:24 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Peter Xu Cc: Fabiano Rosas , qemu-devel@nongnu.org Subject: Re: [PATCH] migration/multifd: Don't fsync when closing QIOChannelFile Message-ID: References: <20240305174332.2553-1-farosas@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/2.2.12 (2023-09-09) X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.3 Received-SPF: pass client-ip=170.10.133.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -26 X-Spam_score: -2.7 X-Spam_bar: -- X-Spam_report: (-2.7 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.568, 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_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham 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: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Wed, Mar 06, 2024 at 08:52:41AM +0800, Peter Xu wrote: > On Tue, Mar 05, 2024 at 05:49:33PM +0000, Daniel P. Berrangé wrote: > > I don't think you should be removing this. Calling qio_channel_close() > > remains recommended best practice, even with fdatasync() removed, as > > it provides a strong guarantee that the FD is released which you don't > > get if you rely on the ref count being correctly decremented in all > > code paths. > > Hmm, I have the confusion on why ioc->fd is more special than the ioc > itself when leaked. It'll be a bug anyway if we leak any of them? Leaking > fds may also help us to find such issue easier (e.g. by seeing stale fds > under /proc). From that POV I tend to agree on the original proposal. Closing the FD would cause any registered I/O handlers callbacks to get POLLNVAL and may well trigger cleanup that will prevent the leak. With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|