From nobody Thu Nov 6 19:05:22 2025 Delivered-To: importer@patchew.org Received-SPF: pass (zoho.com: domain of gnu.org designates 208.118.235.17 as permitted sender) client-ip=208.118.235.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Authentication-Results: mx.zoho.com; spf=pass (zoho.com: domain of gnu.org designates 208.118.235.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; Return-Path: Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) by mx.zohomail.com with SMTPS id 1488227118613747.2116233263644; Mon, 27 Feb 2017 12:25:18 -0800 (PST) Received: from localhost ([::1]:56590 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ciRrB-0003uH-CK for importer@patchew.org; Mon, 27 Feb 2017 15:25:17 -0500 Received: from eggs.gnu.org ([2001:4830:134:3::10]:56773) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ciRcd-0007or-4O for qemu-devel@nongnu.org; Mon, 27 Feb 2017 15:10:16 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ciRcb-0002zb-Rk for qemu-devel@nongnu.org; Mon, 27 Feb 2017 15:10:15 -0500 Received: from mx1.redhat.com ([209.132.183.28]:35452) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1ciRcZ-0002yV-94; Mon, 27 Feb 2017 15:10:11 -0500 Received: from int-mx11.intmail.prod.int.phx2.redhat.com (int-mx11.intmail.prod.int.phx2.redhat.com [10.5.11.24]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 7D58EC04B311; Mon, 27 Feb 2017 20:10:11 +0000 (UTC) Received: from noname.redhat.com (ovpn-116-148.ams2.redhat.com [10.36.116.148]) by int-mx11.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id v1RK9n8K003294; Mon, 27 Feb 2017 15:10:09 -0500 From: Kevin Wolf To: qemu-block@nongnu.org Date: Mon, 27 Feb 2017 21:09:08 +0100 Message-Id: <1488226184-9044-8-git-send-email-kwolf@redhat.com> In-Reply-To: <1488226184-9044-1-git-send-email-kwolf@redhat.com> References: <1488226184-9044-1-git-send-email-kwolf@redhat.com> X-Scanned-By: MIMEDefang 2.68 on 10.5.11.24 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.31]); Mon, 27 Feb 2017 20:10:11 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 209.132.183.28 Subject: [Qemu-devel] [PATCH v2 07/43] block: Default .bdrv_child_perm() for format drivers 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: kwolf@redhat.com, jcody@redhat.com, famz@redhat.com, qemu-devel@nongnu.org, mreitz@redhat.com Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail: RSF_0 Z_629925259 SPT_0 Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Almost all format drivers have the same characteristics as far as permissions are concerned: They have one or more children for storing their own data and, more importantly, metadata (can be written to and grow even without external write requests, must be protected against other writers and present consistent data) and optionally a backing file (this is just data, so like for a filter, it only depends on what the parent nodes need). This provides a default implementation that can be shared by most of our format drivers. Signed-off-by: Kevin Wolf --- block.c | 43 +++++++++++++++++++++++++++++++++++++++++++ include/block/block_int.h | 8 ++++++++ 2 files changed, 51 insertions(+) diff --git a/block.c b/block.c index 597da9a..20dd1c5 100644 --- a/block.c +++ b/block.c @@ -1554,6 +1554,49 @@ void bdrv_filter_default_perms(BlockDriverState *bs,= BdrvChild *c, (c->shared_perm & DEFAULT_PERM_UNCHANGED); } =20 +void bdrv_format_default_perms(BlockDriverState *bs, BdrvChild *c, + const BdrvChildRole *role, + uint64_t perm, uint64_t shared, + uint64_t *nperm, uint64_t *nshared) +{ + bool backing =3D (role =3D=3D &child_backing); + assert(role =3D=3D &child_backing || role =3D=3D &child_file); + + if (!backing) { + /* Apart from the modifications below, the same permissions are + * forwarded and left alone as for filters */ + bdrv_filter_default_perms(bs, c, role, perm, shared, &perm, &share= d); + + /* Format drivers may touch metadata even if the guest doesn't wri= te */ + if (!bdrv_is_read_only(bs)) { + perm |=3D BLK_PERM_WRITE | BLK_PERM_RESIZE; + } + + /* bs->file always needs to be consistent because of the metadata.= We + * can never allow other users to resize or write to it. */ + perm |=3D BLK_PERM_CONSISTENT_READ; + shared &=3D ~(BLK_PERM_WRITE | BLK_PERM_RESIZE); + } else { + /* We want consistent read from backing files if the parent needs = it. + * No other operations are performed on backing files. */ + perm &=3D BLK_PERM_CONSISTENT_READ; + + /* If the parent can deal with changing data, we're okay with a + * writable and resizable backing file. */ + /* TODO Require !(perm & BLK_PERM_CONSISTENT_READ), too? */ + if (shared & BLK_PERM_WRITE) { + shared =3D BLK_PERM_WRITE | BLK_PERM_RESIZE; + } else { + shared =3D 0; + } + + shared |=3D BLK_PERM_CONSISTENT_READ | BLK_PERM_GRAPH_MOD | + BLK_PERM_WRITE_UNCHANGED; + } + + *nperm =3D perm; + *nshared =3D shared; +} =20 static void bdrv_replace_child(BdrvChild *child, BlockDriverState *new_bs) { diff --git a/include/block/block_int.h b/include/block/block_int.h index 17f4c2d..eb0598e 100644 --- a/include/block/block_int.h +++ b/include/block/block_int.h @@ -880,6 +880,14 @@ void bdrv_filter_default_perms(BlockDriverState *bs, B= drvChild *c, uint64_t perm, uint64_t shared, uint64_t *nperm, uint64_t *nshared); =20 +/* Default implementation for BlockDriver.bdrv_child_perm() that can be us= ed by + * (non-raw) image formats: Like above for bs->backing, but for bs->file it + * requires WRITE | RESIZE for read-write images, always requires + * CONSISTENT_READ and doesn't share WRITE. */ +void bdrv_format_default_perms(BlockDriverState *bs, BdrvChild *c, + const BdrvChildRole *role, + uint64_t perm, uint64_t shared, + uint64_t *nperm, uint64_t *nshared); =20 const char *bdrv_get_parent_name(const BlockDriverState *bs); void blk_dev_change_media_cb(BlockBackend *blk, bool load); --=20 1.8.3.1