From patchwork Mon Apr 16 16:58:42 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Max Reitz X-Patchwork-Id: 898796 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=pass (mailfrom) smtp.mailfrom=nongnu.org (client-ip=2001:4830:134:3::11; helo=lists.gnu.org; envelope-from=qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org; receiver=) Authentication-Results: ozlabs.org; dmarc=fail (p=none dis=none) header.from=redhat.com Received: from lists.gnu.org (lists.gnu.org [IPv6:2001:4830:134:3::11]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 40Pvr61ccCz9s3G for ; Tue, 17 Apr 2018 03:04:38 +1000 (AEST) Received: from localhost ([::1]:58482 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1f87YS-0002ul-5P for incoming@patchwork.ozlabs.org; Mon, 16 Apr 2018 13:04:36 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:60491) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1f87T8-0007SY-LP for qemu-devel@nongnu.org; Mon, 16 Apr 2018 12:59:07 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1f87T7-0003Fp-TS for qemu-devel@nongnu.org; Mon, 16 Apr 2018 12:59:06 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:54380 helo=mx1.redhat.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1f87T5-0003DP-DE; Mon, 16 Apr 2018 12:59:03 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id DCA137CBBA; Mon, 16 Apr 2018 16:59:02 +0000 (UTC) Received: from localhost (unknown [10.40.205.23]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 7C6B22142F5C; Mon, 16 Apr 2018 16:59:02 +0000 (UTC) From: Max Reitz To: qemu-block@nongnu.org Date: Mon, 16 Apr 2018 18:58:42 +0200 Message-Id: <20180416165849.28864-3-mreitz@redhat.com> In-Reply-To: <20180416165849.28864-1-mreitz@redhat.com> References: <20180416165849.28864-1-mreitz@redhat.com> X-Scanned-By: MIMEDefang 2.78 on 10.11.54.6 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.2]); Mon, 16 Apr 2018 16:59:02 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.2]); Mon, 16 Apr 2018 16:59:02 +0000 (UTC) for IP:'10.11.54.6' DOMAIN:'int-mx06.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'mreitz@redhat.com' RCPT:'' X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 66.187.233.73 Subject: [Qemu-devel] [PATCH 2/9] block: BLK_PERM_WRITE includes ..._UNCHANGED X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kevin Wolf , Fam Zheng , qemu-devel@nongnu.org, Stefan Hajnoczi , Max Reitz Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: "Qemu-devel" Currently we never actually check whether the WRITE_UNCHANGED permission has been taken for unchanging writes. But the one check that is commented out checks both WRITE and WRITE_UNCHANGED; and considering that WRITE_UNCHANGED is already documented as being weaker then WRITE, we should probably explicitly document WRITE to include WRITE_UNCHANGED. Signed-off-by: Max Reitz Reviewed-by: Stefan Hajnoczi Reviewed-by: Alberto Garcia --- include/block/block.h | 3 +++ 1 file changed, 3 insertions(+) diff --git a/include/block/block.h b/include/block/block.h index cdec3639a3..397b5e8d44 100644 --- a/include/block/block.h +++ b/include/block/block.h @@ -205,6 +205,9 @@ enum { * This permission (which is weaker than BLK_PERM_WRITE) is both enough and * required for writes to the block node when the caller promises that * the visible disk content doesn't change. + * + * As the BLK_PERM_WRITE permission is strictly stronger, either is + * sufficient to perform an unchanging write. */ BLK_PERM_WRITE_UNCHANGED = 0x04,