CA-143836: Add VDI.revert API call

The API function is needed to be able to forward it across the pool and
to block other operations on the VDI while it's running.

It's unused for the time being.

Co-authored-by: John Else <john.else@citrix.com>
Signed-off-by: Pau Ruiz Safont <pau.safont@vates.tech>
(cherry picked from commit 6c95e34)

Author: psafont

ocaml/idl/datamodel.ml

@@ -4275,6 +4275,7 @@ module SR = struct
         ; ("vdi_generate_config", "Generating the configuration of the VDI")
         ; ("vdi_resize_online", "Resizing the VDI online")
         ; ("vdi_update", "Refreshing the fields on the VDI")
+        ; ("vdi_revert", "Reverting a VDI to the snapshot")
         ; ("pbd_create", "Creating a PBD for this SR")
         ; ("pbd_destroy", "Destroying one of this SR's PBDs")
         ]
@@ -5476,6 +5477,16 @@ module VDI = struct
          different SR. The destination SR must be visible to the guest."
       ~allowed_roles:_R_VM_POWER_ADMIN ()
 
+  let revert =
+    call ~name:"revert" ~in_oss_since:None ~lifecycle:[]
+      ~params:
+        [(Ref _vdi, "snapshot", "The snapshot to which we want to revert")]
+      ~doc:
+        "Copy the contents of a snapshot to the VDI it's related to. The \
+         original contents of the VDI are lost."
+      ~errs:[Api_errors.unimplemented_in_sm_backend]
+      ~allowed_roles:_R_VM_POWER_ADMIN ~doc_tags:[Snapshots] ()
+
   let introduce_params first_rel =
     [
       {
@@ -6258,6 +6269,7 @@ module VDI = struct
         ; data_destroy
         ; list_changed_blocks
         ; get_nbd_info
+        ; revert
         ]
       ~contents:
         ([

ocaml/tests/record_util/old_record_util.ml

@@ -360,6 +360,8 @@ let sr_operation_to_string : API.storage_operations -> string = function
       "VDI.resize_online"
   | `vdi_update ->
       "VDI.update"
+  | `vdi_revert ->
+      "VDI.revert"
 
 let vbd_operation_to_string = function
   | `attach ->

ocaml/xapi-cli-server/record_util.ml

@@ -175,6 +175,8 @@ let sr_operation_to_string : API.storage_operations -> string = function
       "VDI.resize_online"
   | `vdi_update ->
       "VDI.update"
+  | `vdi_revert ->
+      "VDI.revert"
   | `pbd_create ->
       "PBD.create"
   | `pbd_destroy ->

ocaml/xapi/message_forwarding.ml

@@ -5563,6 +5563,23 @@ functor
             forward_vdi_op ~local_fn ~__context ~self:vdi ~remote_fn
         )
 
+      let revert ~__context ~snapshot =
+        let ( let@ ) f x = f x in
+        let doc = "VDI.revert" in
+        info "%s: snapshot = '%s'" doc (vdi_uuid ~__context snapshot) ;
+        let local_fn = Local.VDI.revert ~snapshot in
+        let remote_fn = Client.VDI.revert ~snapshot in
+        let sr = Db.VDI.get_SR ~__context ~self:snapshot in
+        let vdi = Db.VDI.get_snapshot_of ~__context ~self:snapshot in
+        let op () =
+          forward_vdi_op ~local_fn ~__context ~self:snapshot ~remote_fn
+        in
+        let@ () =
+          with_sr_andor_vdi ~__context ~sr:(sr, `vdi_revert)
+            ~vdi:(snapshot, `revert_to) ~doc
+        in
+        with_sr_andor_vdi ~__context ~vdi:(vdi, `revert_from) ~doc op
+
       let copy ~__context ~vdi ~sr ~base_vdi ~into_vdi =
         info "VDI.copy: VDI = '%s'; SR = '%s'; base_vdi = '%s'; into_vdi = '%s'"
           (vdi_uuid ~__context vdi) (sr_uuid ~__context sr)

ocaml/xapi/xapi_sr_operations.ml

@@ -48,6 +48,7 @@ let all_ops : API.storage_operations_set =
   ; `vdi_list_changed_blocks
   ; `vdi_set_on_boot
   ; `vdi_introduce
+  ; `vdi_revert
   ; `update
   ; `pbd_create
   ; `pbd_destroy
@@ -89,6 +90,7 @@ let sm_cap_table : (API.storage_operations * _) list =
   ; (`vdi_list_changed_blocks, Vdi_configure_cbt)
   ; (`vdi_set_on_boot, Vdi_reset_on_boot)
   ; (`update, Sr_update)
+  ; (`vdi_revert, Vdi_revert)
   ; (* We fake clone ourselves *)
     (`vdi_snapshot, Vdi_snapshot)
   ]

ocaml/xapi/xapi_vdi.ml

@@ -1118,6 +1118,32 @@ let clone ~__context ~vdi ~driver_params =
       )
   )
 
+let revert' ~__context ~snapshot =
+  let module C = Storage_interface.StorageAPI (Idl.Exn.GenClient (struct
+    let rpc = Storage_access.rpc
+  end)) in
+  let sr = Db.VDI.get_SR ~__context ~self:snapshot in
+  Sm.assert_pbd_is_plugged ~__context ~sr ;
+  Xapi_vdi_helpers.assert_managed ~__context ~vdi:snapshot ;
+  let snapshot_rec = Db.VDI.get_record ~__context ~self:snapshot in
+
+  let task = Context.get_task_id __context in
+  let snapshot_info =
+    Storage_smapiv1.vdi_info_of_vdi_rec __context snapshot_rec
+  in
+  let sr' =
+    Db.SR.get_uuid ~__context ~self:sr |> Storage_interface.Sr.of_string
+  in
+  (* We don't use transform_storage_exn because of the fallback below *)
+  C.VDI.revert (Ref.string_of task) sr' snapshot_info
+
+let revert ~__context ~snapshot =
+  Storage_utils.transform_storage_exn @@ fun () ->
+  try revert' ~__context ~snapshot
+  with Storage_interface.Storage_error (Unimplemented _) ->
+    let msg = [Ref.string_of (Db.VDI.get_SR ~__context ~self:snapshot)] in
+    raise Api_errors.(Server_error (unimplemented_in_sm_backend, msg))
+
 let copy ~__context ~vdi ~sr ~base_vdi ~into_vdi =
   Xapi_vdi_helpers.assert_managed ~__context ~vdi ;
   let task_id = Ref.string_of (Context.get_task_id __context) in

ocaml/xapi/xapi_vdi.mli

@@ -258,3 +258,5 @@ val _get_nbd_info :
     [get_server_certificate] function can be provided to avoid querying the real
     certificate using the Client module, which is what {!get_nbd_info} does,
     which would cause the unit test to fail. *)
+
+val revert : __context:Context.t -> snapshot:[`VDI] Ref.t -> unit