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 A619DC5478C for ; Fri, 1 Mar 2024 17:50:49 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1rg71n-0006FJ-M6; Fri, 01 Mar 2024 12:50:35 -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 1rg71m-0006Ev-3o for qemu-devel@nongnu.org; Fri, 01 Mar 2024 12:50:34 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rg71k-0001C1-7U for qemu-devel@nongnu.org; Fri, 01 Mar 2024 12:50:33 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1709315431; 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:in-reply-to:in-reply-to: references:references; bh=/Y465+ptn/nUZiasWZbpBFilVca+31DZltQTGQGGTIg=; b=AHVFrFFeqqZrjqMLDXoqdh12XmZHrDlbzyJFBqrWwS1GRZljiBP9ZaPVb3XCGLiUvNf+v4 80RAdkKKxcVmdi2s3Y7KJFyDQQQThSjOW6wDk7T+nUFVcihP/reQ2zmSIA2Kc1BZLn9tRk 8saefQ1J1h9dqGufiYOuS/wSYidIxEs= 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-245-MN7yrHZBMb-do9TWrzdD_w-1; Fri, 01 Mar 2024 12:50:28 -0500 X-MC-Unique: MN7yrHZBMb-do9TWrzdD_w-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (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 D1F77185A784; Fri, 1 Mar 2024 17:50:27 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.50]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 17DB739D6D; Fri, 1 Mar 2024 17:50:25 +0000 (UTC) Date: Fri, 1 Mar 2024 17:50:24 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Prasad Pandit Cc: peterx@redhat.com, qemu-devel@nongnu.org, Fabiano Rosas Subject: Re: [PATCH] migration/multifd: Document two places for mapped-ram Message-ID: References: <20240301091524.39900-1-peterx@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/2.2.12 (2023-09-09) X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.5 Received-SPF: pass client-ip=170.10.129.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -21 X-Spam_score: -2.2 X-Spam_bar: -- X-Spam_report: (-2.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.096, 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, 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 Fri, Mar 01, 2024 at 11:17:10PM +0530, Prasad Pandit wrote: > Hello Petr, > > On Fri, 1 Mar 2024 at 14:46, wrote: > > + * An explicitly close() on the channel here is normally not > > explicitly -> explicit > > > + * required, but can be helpful for "file:" iochannels, where it > > + * will include an fdatasync() to make sure the data is flushed to > > + * the disk backend. > > * an fdatasync() -> fdatasync() > > * qio_channel_close > -> ioc_klass->io_close = qio_channel_file_close; > -> qemu_close(fioc->fd) > -> close(fd); > > It does not seem to call fdatasync() before close(fd); > > - qio_channel_file_new_path(filename, O_CREAT | O_WRONLY | O_TRUNC, ...) The documented behaviour reliant on another pending patch: https://lists.nongnu.org/archive/html/qemu-devel/2024-02/msg07046.html > > Maybe the qio_channel..() calls above should include the 'O_DSYNC' > flag as well? But that will do fdatasync() work at each write(2) call > I think, not sure if that is okay. > > > + * > > + * The object_unref() cannot guarantee that because: (1) finalize() > > + * of the iochannel is only triggered on the last reference, and > > + * it's not guaranteed that we always hold the last refcount when > > + * reaching here, and, (2) even if finalize() is invoked, it only > > + * does a close(fd) without data flush. > > + */ > > * object_unref > -> object_finalize > -> object_deinit > -> type->instance_finalize > -> qio_channel_file_finalize > -> qemu_close(ioc->fd); > > * I hope I'm looking at the right code here. (Sorry if I'm not) 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 :|