From nobody Sun Oct 5 21:17:19 2025 Delivered-To: importer@patchew.org Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Authentication-Results: mx.zohomail.com; dkim=fail; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=fail(p=none dis=none) header.from=redhat.com Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 1580492783635475.9927558670763; Fri, 31 Jan 2020 09:46:23 -0800 (PST) Received: from localhost ([::1]:57202 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ixaN3-0004Sj-AE for importer@patchew.org; Fri, 31 Jan 2020 12:46:21 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:41211) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ixaLW-0002c5-H0 for qemu-devel@nongnu.org; Fri, 31 Jan 2020 12:44:47 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ixaLV-0004Ix-Kb for qemu-devel@nongnu.org; Fri, 31 Jan 2020 12:44:46 -0500 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:27108 helo=us-smtp-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1ixaLV-0004HX-HA for qemu-devel@nongnu.org; Fri, 31 Jan 2020 12:44:45 -0500 Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-296-WL7OkWzdOqKhTIAEP-OaqQ-1; Fri, 31 Jan 2020 12:44:42 -0500 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id C2DA013F9; Fri, 31 Jan 2020 17:44:41 +0000 (UTC) Received: from blue.redhat.com (ovpn-116-181.phx2.redhat.com [10.3.116.181]) by smtp.corp.redhat.com (Postfix) with ESMTP id 530EC7FB60; Fri, 31 Jan 2020 17:44:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1580492684; 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=y3UezPAkLNH5PjZcf6ESIZM+p07nrMqbwQwde4FJnfw=; b=P4a+Z5CenmRzFF7kNHrABm+O4/k00axnwZV1mkUgNgOLtmHwm1pb0Q7zm1YHMoRBZlnrE9 /A4zn1EBMzh0HEcjFLwW8gVV4bThqEP3aAG6jk6xmgv2OwqL17hksUSmcY+U0+19mtVkfQ 6T9dOESt7dWDdWhGBPqjmoj/lqhnDI8= From: Eric Blake To: qemu-devel@nongnu.org Subject: [PATCH 04/17] block: Improve documentation of .bdrv_has_zero_init Date: Fri, 31 Jan 2020 11:44:23 -0600 Message-Id: <20200131174436.2961874-5-eblake@redhat.com> In-Reply-To: <20200131174436.2961874-1-eblake@redhat.com> References: <20200131174436.2961874-1-eblake@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-MC-Unique: WL7OkWzdOqKhTIAEP-OaqQ-1 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: quoted-printable X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 205.139.110.120 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: david.edmondson@oracle.com, Kevin Wolf , qemu-block@nongnu.org, mreitz@redhat.com Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: fail (Header signature does not verify) Content-Type: text/plain; charset="utf-8" Several drivers supply .bdrv_has_zero_init that returns 1, but lack the .bdrv_has_zero_init_truncate callback (parallels and qed outright, vdi in some scenarios). A literal reading of the existing documentation says such drivers are broken, because bdrv_has_zero_init_truncate() defaults to zero if the callback is missing; but in practice, the tie between the two functions is only relevant when truncate is supported. Clarify the documentation to make it obvious that this is okay. Fixes: 1dcaf527 Signed-off-by: Eric Blake --- include/block/block_int.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/include/block/block_int.h b/include/block/block_int.h index 640fb82c789e..77ab45dc87cf 100644 --- a/include/block/block_int.h +++ b/include/block/block_int.h @@ -444,7 +444,8 @@ struct BlockDriver { /* * Returns 1 if newly created images are guaranteed to contain only * zeros, 0 otherwise. - * Must return 0 if .bdrv_has_zero_init_truncate() returns 0. + * Must return 0 if .bdrv_co_truncate is set and + * .bdrv_has_zero_init_truncate() returns 0. */ int (*bdrv_has_zero_init)(BlockDriverState *bs); --=20 2.24.1