qemu: migration: Disallow migration of read only disk

Currently Libvirt allows attempts to migrate read only disks. Qemu
cannot handle this as read only disks cannot be written to on the
destination system. The end result is a cryptic error message and a
failed migration.

This patch causes migration to fail earlier and provides a meaningful
error message stating that migrating read only disks is not supported.

Signed-off-by: Corey S. McQuay <csmcquay@linux.vnet.ibm.com>
Reviewed-by: Jason J. Herne <jjherne@linux.vnet.ibm.com>
Reviewed-by: Boris Fiuczynski <fiuczy@linux.vnet.ibm.com>

diff --git a/src/qemu/qemu_migration.c b/src/qemu/qemu_migration.c
index e2ca3303efd3c2d126114b0a468f7c5d28353dcc..1e7abc53f5b037cc079cbd9b18fccfcf6e0e018e 100644 (file)
--- a/src/qemu/qemu_migration.c
+++ b/src/qemu/qemu_migration.c
@@ -1765,6 +1765,12 @@ qemuMigrationStartNBDServer(virQEMUDriverPtr driver,
         if (!qemuMigrateDisk(disk, nmigrate_disks, migrate_disks))
             continue;
 
+        if (disk->src->readonly) {
+            virReportError(VIR_ERR_OPERATION_UNSUPPORTED,
+                           _("Cannot migrate read-only disk %s"), disk->dst);
+            goto cleanup;
+        }
+
         VIR_FREE(diskAlias);
         if (!(diskAlias = qemuAliasFromDisk(disk)))
             goto cleanup;