CA-424844 Revert PR #6915 (#6952)

Revert PR #6915. There is a regression fail when the cross-pool SXM for
a VM with snapshot. The VDI snapshot_of data is missing.

Author: changlei-li

ocaml/xapi/import.ml

@@ -2076,57 +2076,37 @@ let handlers =
   ; (Datamodel_common._vtpm, VTPMHandler.handle)
   ]
 
-(* If snapshot_of(x) = y, and both x and y are freshly imported VDIs,
-   the field must be rewritten to a real database reference. The same
-   relationship formed by parental links must be preserved as well.
-
-   We can't do this on-the-fly during an import because we can't
-   guarantee that the VDIs will be imported in reverse topological
-   order of the relation induced by snapshot_of. *)
-let update_vdi_links ~__context state =
-  (* Map an exported reference to a (freshly) imported reference, or
-     null if it's not present in the import. *)
-  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.VDI.get_record ~__context ~self:x in
-    let parent = resolve_import x_r.API.vDI_parent in
-    let snapshot_of = resolve_import x_r.API.vDI_snapshot_of in
-    Db.VDI.set_parent ~__context ~self:x ~value:parent ;
-    Db.VDI.set_snapshot_of ~__context ~self:x ~value:snapshot_of ;
-    Db.VDI.set_is_a_snapshot ~__context ~self:x ~value:(snapshot_of <> Ref.null)
-  in
-  let go (cls, _, r) =
-    if cls = Datamodel_common._vdi then update (Ref.of_string r)
-  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 update_snapshot_and_parent_links ~__context state =
+  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 =
@@ -2174,8 +2154,7 @@ let handle_all __context config rpc session_id (xs : obj list) =
           false
     in
     if not dry_run then (
-      update_vm_links ~__context state ;
-      update_vdi_links ~__context state ;
+      update_snapshot_and_parent_links ~__context state ;
       check_references ~__context state.table
     ) ;
     state