Revert "Rewrite update_vm_links"

This reverts commit a4f516f.

Signed-off-by: Changlei Li <changlei.li@cloud.com>

Author: changlei-li

ocaml/xapi/import.ml

@@ -2103,27 +2103,37 @@ let update_vdi_links ~__context state =
   in
   List.iter go state.table
 
-(* Same as [update_vdi_links] but over VMs instead. *)
 let update_vm_links ~__context state =
-  let resolve_import =
-    let tbl = Hashtbl.create 16 in
-    let go (_, a, b) = Hashtbl.replace tbl a (Ref.of_string b) in
-    List.iter go state.table ;
-    fun r ->
-      Hashtbl.find_opt tbl (Ref.string_of r) |> Option.value ~default:Ref.null
-  in
-  let update x =
-    let x_r = Db.VM.get_record ~__context ~self:x in
-    let parent = resolve_import x_r.API.vM_parent in
-    let snapshot_of = resolve_import x_r.API.vM_snapshot_of in
-    Db.VM.set_parent ~__context ~self:x ~value:parent ;
-    Db.VM.set_snapshot_of ~__context ~self:x ~value:snapshot_of ;
-    Db.VM.set_is_a_snapshot ~__context ~self:x ~value:(snapshot_of <> Ref.null)
-  in
-  let go (cls, _, r) =
-    if cls = Datamodel_common._vm then update (Ref.of_string r)
+  let aux (cls, _, ref) =
+    let ref = Ref.of_string ref in
+    ( if
+        cls = Datamodel_common._vm
+        && Db.VM.get_is_a_snapshot ~__context ~self:ref
+      then
+        let snapshot_of = Db.VM.get_snapshot_of ~__context ~self:ref in
+        if snapshot_of <> Ref.null then (
+          debug "lookup for snapshot_of = '%s'" (Ref.string_of snapshot_of) ;
+          log_reraise
+            ("Failed to find the VM which is snapshot of "
+            ^ Db.VM.get_name_label ~__context ~self:ref
+            )
+            (fun table ->
+              let snapshot_of = (lookup snapshot_of) table in
+              Db.VM.set_snapshot_of ~__context ~self:ref ~value:snapshot_of
+            )
+            state.table
+        )
+    ) ;
+    if cls = Datamodel_common._vm then (
+      let parent = Db.VM.get_parent ~__context ~self:ref in
+      debug "lookup for parent = '%s'" (Ref.string_of parent) ;
+      try
+        let parent = lookup parent state.table in
+        Db.VM.set_parent ~__context ~self:ref ~value:parent
+      with _ -> debug "no parent found"
+    )
   in
-  List.iter go state.table
+  List.iter aux state.table
 
 let check_references ~__context (table : table) =
   let is_export_reference r =