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bh=Na6LFAxvfpAY3dT78yZFmDnKhomLwTA8w3U/O1UEuR4=; b=ES9ST0bia5A/JwgIz9Z9506JVWiM5R/Sjt+rL6NBNu/IgrSLJew0L55JI6W3Thv1D2ouZv VewcpolPaSCqbX+kCI+3Sqf85VeZftc/B8tNv9aY2k1E6URlU2qcc6yonFbdKr3s28k2W6 UeVjNARbFWSP172e++ZUMto5Myi2Yss= X-MC-Unique: nLdUukXOOaC-dWG1HBoezg-1 From: Max Reitz To: qemu-block@nongnu.org Subject: [PATCH v7 17/47] block: Re-evaluate backing file handling in reopen Date: Thu, 25 Jun 2020 17:21:45 +0200 Message-Id: <20200625152215.941773-18-mreitz@redhat.com> In-Reply-To: <20200625152215.941773-1-mreitz@redhat.com> References: <20200625152215.941773-1-mreitz@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=mreitz@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: quoted-printable 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; Received-SPF: pass client-ip=207.211.31.81; envelope-from=mreitz@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/06/25 02:30:11 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] 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, 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_H3=-0.01, RCVD_IN_MSPIKE_WL=-0.01, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=_AUTOLEARN X-Spam_action: no action 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: Kevin Wolf , Vladimir Sementsov-Ogievskiy , qemu-devel@nongnu.org, Max Reitz 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" Reopening a node's backing child needs a bit of special handling because the "backing" child has different defaults than all other children (among other things). Adding filter support here is a bit more difficult than just using the child access functions. In fact, we often have to directly use bs->backing because these functions are about the "backing" child (which may or may not be the COW backing file). Signed-off-by: Max Reitz --- block.c | 46 ++++++++++++++++++++++++++++++++++++++-------- 1 file changed, 38 insertions(+), 8 deletions(-) diff --git a/block.c b/block.c index 712230ef5c..8131d0b5eb 100644 --- a/block.c +++ b/block.c @@ -4026,26 +4026,56 @@ static int bdrv_reopen_parse_backing(BDRVReopenStat= e *reopen_state, } } =20 + /* + * Ensure that @bs can really handle backing files, because we are + * about to give it one (or swap the existing one) + */ + if (bs->drv->is_filter) { + /* Filters always have a file or a backing child */ + if (!bs->backing) { + error_setg(errp, "'%s' is a %s filter node that does not suppo= rt a " + "backing child", bs->node_name, bs->drv->format_nam= e); + return -EINVAL; + } + } else if (!bs->drv->supports_backing) { + error_setg(errp, "Driver '%s' of node '%s' does not support backin= g " + "files", bs->drv->format_name, bs->node_name); + return -EINVAL; + } + /* * Find the "actual" backing file by skipping all links that point * to an implicit node, if any (e.g. a commit filter node). + * We cannot use any of the bdrv_skip_*() functions here because + * those return the first explicit node, while we are looking for + * its overlay here. */ overlay_bs =3D bs; - while (backing_bs(overlay_bs) && backing_bs(overlay_bs)->implicit) { - overlay_bs =3D backing_bs(overlay_bs); + while (bdrv_filter_or_cow_bs(overlay_bs) && + bdrv_filter_or_cow_bs(overlay_bs)->implicit) + { + overlay_bs =3D bdrv_filter_or_cow_bs(overlay_bs); } =20 /* If we want to replace the backing file we need some extra checks */ - if (new_backing_bs !=3D backing_bs(overlay_bs)) { + if (new_backing_bs !=3D bdrv_filter_or_cow_bs(overlay_bs)) { /* Check for implicit nodes between bs and its backing file */ if (bs !=3D overlay_bs) { error_setg(errp, "Cannot change backing link if '%s' has " "an implicit backing file", bs->node_name); return -EPERM; } - /* Check if the backing link that we want to replace is frozen */ - if (bdrv_is_backing_chain_frozen(overlay_bs, backing_bs(overlay_bs= ), - errp)) { + /* + * Check if the backing link that we want to replace is frozen. + * Note that + * bdrv_filter_or_cow_child(overlay_bs) =3D=3D overlay_bs->backing, + * because we know that overlay_bs =3D=3D bs, and that @bs + * either is a filter that uses ->backing or a COW format BDS + * with bs->drv->supports_backing =3D=3D true. + */ + if (bdrv_is_backing_chain_frozen(overlay_bs, + child_bs(overlay_bs->backing), er= rp)) + { return -EPERM; } reopen_state->replace_backing_bs =3D true; @@ -4196,7 +4226,7 @@ int bdrv_reopen_prepare(BDRVReopenState *reopen_state= , BlockReopenQueue *queue, * its metadata. Otherwise the 'backing' option can be omitted. */ if (drv->supports_backing && reopen_state->backing_missing && - (backing_bs(reopen_state->bs) || reopen_state->bs->backing_file[0]= )) { + (reopen_state->bs->backing || reopen_state->bs->backing_file[0])) { error_setg(errp, "backing is missing for '%s'", reopen_state->bs->node_name); ret =3D -EINVAL; @@ -4337,7 +4367,7 @@ void bdrv_reopen_commit(BDRVReopenState *reopen_state) * from bdrv_set_backing_hd()) has the new values. */ if (reopen_state->replace_backing_bs) { - BlockDriverState *old_backing_bs =3D backing_bs(bs); + BlockDriverState *old_backing_bs =3D child_bs(bs->backing); assert(!old_backing_bs || !old_backing_bs->implicit); /* Abort the permission update on the backing bs we're detaching */ if (old_backing_bs) { --=20 2.26.2