[RFC PATCH 6/7] qemuMigrationSrcRun: Don't attempt any storage migration if no disks will be migrated

[Peter Krempa <pkrempa@xxxxxxxxxx>]

Don't even try to setup storage migration if there are no eligible
disks.

This also fixes migration from older libvirts which didn't format an
empty <nbd/> element in the migration cookie if there weren't any disks
to migrate.

Signed-off-by: Peter Krempa <pkrempa@xxxxxxxxxx>
---
 src/qemu/qemu_migration.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/src/qemu/qemu_migration.c b/src/qemu/qemu_migration.c
index 9ea008836c..119459342e 100644
--- a/src/qemu/qemu_migration.c
+++ b/src/qemu/qemu_migration.c
@@ -312,6 +312,22 @@ qemuMigrationAnyCopyDisk(virDomainDiskDef const *disk,
 }


+static bool
+qemuMigrationHasAnyStorageMigrationDisks(virDomainDef *def,
+                                         const char **migrate_disks,
+                                         size_t nmigrate_disks)
+{
+    size_t i;
+
+    for (i = 0; i < def->ndisks; i++) {
+        if (qemuMigrationAnyCopyDisk(def->disks[i], nmigrate_disks, migrate_disks))
+            return true;
+    }
+
+    return false;
+}
+
+
 static int
 qemuMigrationDstPrecreateStorage(virDomainObj *vm,
                                  qemuMigrationCookieNBD *nbd,
@@ -4011,6 +4027,11 @@ qemuMigrationSrcRun(virQEMUDriver *driver,
               spec, spec->destType, spec->fwdType, dconn,
               NULLSTR(graphicsuri), nmigrate_disks, migrate_disks);

+    if (storageMigration)
+        storageMigration = qemuMigrationHasAnyStorageMigrationDisks(vm->def,
+                                                                    migrate_disks,
+                                                                    nmigrate_disks);
+
     if (storageMigration) {
         cookieFlags |= QEMU_MIGRATION_COOKIE_NBD;

-- 
2.30.2