qemu: backup: Fix backup of disk skipped in an intermediate checkpoint

If a disk is not captured by one of the intermediate checkpoints the
code would fail, but we can easily calculate the bitmaps to merge
correctly by skipping over checkpoints which don't describe the disk.
Signed-off-by: NPeter Krempa <pkrempa@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>

src/qemu/qemu_backup.c

@@ -240,6 +240,30 @@ qemuBackupDiskPrepareOneBitmapsChain(virDomainMomentDefPtr *incremental,
     for (incridx = 0; incremental[incridx]; incridx++) {
         g_autoptr(virJSONValue) tmp = virJSONValueNewArray();
         virStorageSourcePtr tmpsrc = NULL;
+        virDomainCheckpointDefPtr chkdef = (virDomainCheckpointDefPtr) incremental[incridx];
+        bool checkpoint_has_disk = false;
+        size_t i;
+
+        for (i = 0; i < chkdef->ndisks; i++) {
+            if (STRNEQ_NULLABLE(diskdst, chkdef->disks[i].name))
+                continue;
+
+            if (chkdef->disks[i].type == VIR_DOMAIN_CHECKPOINT_TYPE_BITMAP)
+                checkpoint_has_disk = true;
+
+            break;
+        }
+
+        if (!checkpoint_has_disk) {
+            if (!incremental[incridx + 1]) {
+                virReportError(VIR_ERR_INVALID_ARG,
+                               _("disk '%s' not found in checkpoint '%s'"),
+                               diskdst, incremental[incridx]->name);
+                return NULL;
+            }
+
+            continue;
+        }
 
         if (qemuBackupGetBitmapMergeRange(n, incremental[incridx]->name,
                                           &tmp, &tmpsrc, diskdst,

tests/qemublocktest.c

@@ -727,6 +727,12 @@ testQemuBackupGetIncrementalMoment(const char *name)
     if (!(checkpoint = virDomainCheckpointDefNew()))
         abort();
 
+    checkpoint->disks = g_new0(virDomainCheckpointDiskDef, 1);
+    checkpoint->ndisks = 1;
+
+    checkpoint->disks[0].name = g_strdup("testdisk");
+    checkpoint->disks[0].type = VIR_DOMAIN_CHECKPOINT_TYPE_BITMAP;
+
     checkpoint->parent.name = g_strdup(name);
 
     return (virDomainMomentDefPtr) checkpoint;