From: Peter Krempa <pkrempa@redhat.com>
Date: Wed, 6 May 2020 15:41:12 +0000 (+0200)
Subject: qemu: snapshot: Allow snapshots of read-only disks when we can create them
X-Git-Tag: v6.4.0-rc1~106
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=fe574ea1f52daebddfdc91dd27234059c375e4bf;p=thirdparty%2Flibvirt.git

qemu: snapshot: Allow snapshots of read-only disks when we can create them

With -blockdev or when reusing externally created images and thus
without the need for formatting the image we actually can support
snapshots of read-only disks. Arguably it's not very useful so they are
not done by default but users of libvirt such as oVirt are actually
using this.

https://bugzilla.redhat.com/show_bug.cgi?id=1832204

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>
---

diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index 63b4a49c3c..a98a2986f5 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -14687,7 +14687,7 @@ qemuDomainSnapshotPrepareDiskExternal(virDomainObjPtr vm,
     int err;
     int rc;
 
-    if (disk->src->readonly) {
+    if (disk->src->readonly && !(reuse || blockdev)) {
         virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
                        _("external snapshot for readonly disk %s "
                          "is not supported"), disk->dst);