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 A4A52C433FE for ; Fri, 4 Nov 2022 13:13:50 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1oqwVL-00024n-BK; Fri, 04 Nov 2022 09:13:03 -0400 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 1oqwVK-00024O-DD for qemu-devel@nongnu.org; Fri, 04 Nov 2022 09:13:02 -0400 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 1oqwVH-0006tu-KJ for qemu-devel@nongnu.org; Fri, 04 Nov 2022 09:13:02 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1667567578; 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: in-reply-to:in-reply-to:references:references; bh=w3S6zsC7+ZpDgQZmNecvfWm4ZBk88gsEiuBCXbqxzpU=; b=exakQ10xHh06TbiylPsjSR7Yb3a64Wz4yifjS/GP/1AjIxetfZ0fxvJx2k4ubruz5Qhlvh T0DFmyQ1fTkH/oYTOu/3XWAlgXhjM4RsUq4q/8ljYd7fsl52TqlgtdZSKf5Ug1hzKRhM97 0TFhLw+woufawn82iYd7yYrXLTbSAQ4= 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-622-mUWVU5l_Ooi2gI_RN95EAQ-1; Fri, 04 Nov 2022 09:12:55 -0400 X-MC-Unique: mUWVU5l_Ooi2gI_RN95EAQ-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 DA53B857F90; Fri, 4 Nov 2022 13:12:54 +0000 (UTC) Received: from redhat.com (unknown [10.39.193.192]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 4D7D340C835A; Fri, 4 Nov 2022 13:12:53 +0000 (UTC) Date: Fri, 4 Nov 2022 14:12:51 +0100 From: Kevin Wolf To: Paolo Bonzini Cc: Emanuele Giuseppe Esposito , qemu-block@nongnu.org, Hanna Reitz , John Snow , Vladimir Sementsov-Ogievskiy , Eric Blake , Fam Zheng , qemu-devel@nongnu.org Subject: Re: [PATCH 2/9] block-copy: add missing coroutine_fn annotations Message-ID: References: <20221103134206.4041928-1-eesposit@redhat.com> <20221103134206.4041928-3-eesposit@redhat.com> <8f24c24c-ca61-108c-924b-39465a3c67fe@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.045, 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: , Sender: "Qemu-devel" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Am 04.11.2022 um 09:44 hat Paolo Bonzini geschrieben: > On 11/4/22 08:35, Emanuele Giuseppe Esposito wrote: > > But isn't it a bug also not to mark a function _only_ called by > > coroutine_fn? My point is that if this function is an implementation of > > a BlockDriver callback marked as coroutine_fn (like in patch 6 with > > vmdk), then it would make sense. > > If a function implements a coroutine_fn callback but does not suspend, then > it makes sense to mark it coroutine_fn. > > In general it's not a bug. In most cases it would only be a coincidence > that the function is called from a coroutine_fn. For example consider > bdrv_round_to_clusters(). Marking it coroutine_fn signals that it may > suspend now (it doesn't) or in the future. However it's only doing some > math based on the result of bdrv_get_info(), so it is extremely unlikely > that this will happen. > > In this case... oh wait. block_copy_is_cluster_allocated is calling > bdrv_is_allocated, and block_copy_reset_unallocated calls > block_copy_is_cluster_allocated. bdrv_is_allocated is a mixed > coroutine/non-coroutine function, and in this case it is useful to document > that bdrv_is_allocated will suspend. The patch is correct, only the commit > message is wrong. Ah, right, now I remember that this is what I had discussed with Emanuele. I knew that there was a reason for it... What we probably should really do is a bdrv_co_is_allocated() that doesn't go through the mixed function, but directly calls bdrv_co_common_block_status_above(). bdrv_is_allocated() is only a smaller wrapper anyway, so it wouldn't duplicate much code. I seem to remember that Emanuele had a few more bdrv_is_allocated() calls that actually took the coroutine path and could use the same new function. Kevin