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Thu, 25 Jun 2020 15:22:56 +0000 (UTC) Received: from localhost (ovpn-113-182.ams2.redhat.com [10.36.113.182]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 653D8579A3; Thu, 25 Jun 2020 15:22:56 +0000 (UTC) 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 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+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" 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(BDRVReopenState *reopen_state, } } + /* + * 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 support a " + "backing child", bs->node_name, bs->drv->format_name); + return -EINVAL; + } + } else if (!bs->drv->supports_backing) { + error_setg(errp, "Driver '%s' of node '%s' does not support backing " + "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 = bs; - while (backing_bs(overlay_bs) && backing_bs(overlay_bs)->implicit) { - overlay_bs = backing_bs(overlay_bs); + while (bdrv_filter_or_cow_bs(overlay_bs) && + bdrv_filter_or_cow_bs(overlay_bs)->implicit) + { + overlay_bs = bdrv_filter_or_cow_bs(overlay_bs); } /* If we want to replace the backing file we need some extra checks */ - if (new_backing_bs != backing_bs(overlay_bs)) { + if (new_backing_bs != bdrv_filter_or_cow_bs(overlay_bs)) { /* Check for implicit nodes between bs and its backing file */ if (bs != 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) == overlay_bs->backing, + * because we know that overlay_bs == bs, and that @bs + * either is a filter that uses ->backing or a COW format BDS + * with bs->drv->supports_backing == true. + */ + if (bdrv_is_backing_chain_frozen(overlay_bs, + child_bs(overlay_bs->backing), errp)) + { return -EPERM; } reopen_state->replace_backing_bs = 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 = -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 = backing_bs(bs); + BlockDriverState *old_backing_bs = 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) {