CP-53555: Split unplug atomic into deactivate/detach

This consists of two parts, splitting the unplug function into
functionally equivalent deactivate and detach functions, and splitting
the VBD_unplug atomic itself's behaviour into two new atomics:
VBD_deactivate and VBD_detach

If the xenopsd_vbd_plug_unplug_legacy flag is true, the only difference
will be that VBD_unplug calls deactivate and detach sequentially instead
of unplug

If xenopsd_vbd_plug_unplug_legacy is false, the VBD_deactivate and
VBD_detach atomics will be used in place of VBD_unplug in all places
that it is used. This should still be functionally equivalent.

The purpose of this change is to allow optimisations in this area as
there are some situations where they do not need to be called at the
same time. For example we could skip detaching on reboot and only
deactivate and activate again reducing reboot time.

Signed-off-by: Steven Woods <[email protected]>

Author: snwoods

ocaml/xenopsd/lib/xenops_server.ml

@@ -130,6 +130,8 @@ type atomic =
   | VBD_epoch_end of (Vbd.id * disk)
   | VBD_set_qos of Vbd.id
   | VBD_unplug of Vbd.id * bool
+  | VBD_deactivate of Vbd.id * bool
+  | VBD_detach of Vbd.id
   | VBD_insert of Vbd.id * disk
   | VBD_set_active of Vbd.id * bool
   | VM_remove of Vm.id
@@ -211,6 +213,10 @@ let rec name_of_atomic = function
       "VBD_set_qos"
   | VBD_unplug _ ->
       "VBD_unplug"
+  | VBD_deactivate _ ->
+      "VBD_deactivate"
+  | VBD_detach _ ->
+      "VBD_detach"
   | VBD_insert _ ->
       "VBD_insert"
   | VBD_set_active _ ->
@@ -1600,6 +1606,14 @@ let vbd_plug vbd_id =
     serial_of "VBD.attach_and_activate" ~id:(VBD_DB.vm_of vbd_id)
       (VBD_attach vbd_id) (VBD_activate vbd_id) []
 
+let vbd_unplug vbd_id force =
+  if !xenopsd_vbd_plug_unplug_legacy then
+    VBD_unplug (vbd_id, force)
+  else
+    serial_of "VBD.deactivate_and_detach" ~id:(VBD_DB.vm_of vbd_id)
+      (VBD_deactivate (vbd_id, force))
+      (VBD_detach vbd_id) []
+
 let rec atomics_of_operation = function
   | VM_start (id, force) ->
       let vbds_rw, vbds_ro = VBD_DB.vbds id |> vbd_plug_sets in
@@ -1688,7 +1702,7 @@ let rec atomics_of_operation = function
         ]
       ; parallel_concat "Devices.unplug" ~id
           [
-            List.map (fun vbd -> VBD_unplug (vbd.Vbd.id, true)) vbds
+            List.map (fun vbd -> vbd_unplug vbd.Vbd.id true) vbds
           ; List.map (fun vif -> VIF_unplug (vif.Vif.id, true)) vifs
           ; List.map (fun pci -> PCI_unplug pci.Pci.id) pcis
           ]
@@ -1847,7 +1861,7 @@ let rec atomics_of_operation = function
   | VBD_hotplug id ->
       [VBD_set_active (id, true); vbd_plug id]
   | VBD_hotunplug (id, force) ->
-      [VBD_unplug (id, force); VBD_set_active (id, false)]
+      [vbd_unplug id force; VBD_set_active (id, false)]
   | VIF_hotplug id ->
       [VIF_set_active (id, true); VIF_plug id]
   | VIF_hotunplug (id, force) ->
@@ -2065,8 +2079,22 @@ let rec perform_atomic ~progress_callback ?result (op : atomic)
   | VBD_unplug (id, force) ->
       debug "VBD.unplug %s" (VBD_DB.string_of_id id) ;
       finally
-        (fun () -> B.VBD.unplug t (VBD_DB.vm_of id) (VBD_DB.read_exn id) force)
+        (fun () ->
+          B.VBD.deactivate t (VBD_DB.vm_of id) (VBD_DB.read_exn id) force ;
+          B.VBD.detach t (VBD_DB.vm_of id) (VBD_DB.read_exn id)
+        )
+        (fun () -> VBD_DB.signal id)
+  | VBD_deactivate (id, force) ->
+      debug "VBD.deactivate %s" (VBD_DB.string_of_id id) ;
+      finally
+        (fun () ->
+          B.VBD.deactivate t (VBD_DB.vm_of id) (VBD_DB.read_exn id) force
+        )
         (fun () -> VBD_DB.signal id)
+  | VBD_detach id ->
+      debug "VBD.detach %s" (VBD_DB.string_of_id id) ;
+      B.VBD.detach t (VBD_DB.vm_of id) (VBD_DB.read_exn id) ;
+      VBD_DB.signal id
   | VBD_insert (id, disk) -> (
       (* NB this is also used to "refresh" ie signal a qemu that it should
          re-open a device, useful for when a physical CDROM is inserted into the
@@ -2481,6 +2509,8 @@ and trigger_cleanup_after_failure_atom op t =
   | VBD_epoch_end (id, _)
   | VBD_set_qos id
   | VBD_unplug (id, _)
+  | VBD_deactivate (id, _)
+  | VBD_detach id
   | VBD_insert (id, _) ->
       immediate_operation dbg (fst id) (VBD_check_state id)
   | VIF_plug id

ocaml/xenopsd/lib/xenops_server_plugin.ml

@@ -211,7 +211,9 @@ module type S = sig
 
     val activate : Xenops_task.task_handle -> Vm.id -> Vbd.t -> unit
 
-    val unplug : Xenops_task.task_handle -> Vm.id -> Vbd.t -> bool -> unit
+    val deactivate : Xenops_task.task_handle -> Vm.id -> Vbd.t -> bool -> unit
+
+    val detach : Xenops_task.task_handle -> Vm.id -> Vbd.t -> unit
 
     val insert : Xenops_task.task_handle -> Vm.id -> Vbd.t -> disk -> unit
 

ocaml/xenopsd/lib/xenops_server_simulator.ml

@@ -677,7 +677,9 @@ module VBD = struct
 
   let activate _ (_vm : Vm.id) (_vbd : Vbd.t) = ()
 
-  let unplug _ vm vbd _ = with_lock m (remove_vbd vm vbd)
+  let deactivate _ vm vbd _ = with_lock m (remove_vbd vm vbd)
+
+  let detach _ _vm _vbd = ()
 
   let insert _ _vm _vbd _disk = ()
 

ocaml/xenopsd/lib/xenops_server_skeleton.ml

@@ -149,7 +149,9 @@ module VBD = struct
 
   let activate _ _ _ = unimplemented "VBD.activate"
 
-  let unplug _ _ _ _ = unimplemented "VBD.unplug"
+  let deactivate _ _ _ _ = unimplemented "VBD.deactivate"
+
+  let detach _ _ _ = unimplemented "VBD.detach"
 
   let insert _ _ _ _ = unimplemented "VBD.insert"
 

ocaml/xenopsd/xc/xenops_server_xen.ml

@@ -3886,22 +3886,22 @@ module VBD = struct
           )
           (fun () -> cleanup_attached_vdis vm vbd.id)
 
-  let unplug task vm vbd force =
+  let deactivate task vm vbd force =
     with_xc_and_xs (fun xc xs ->
         try
           (* On destroying the datapath
 
-             1. if the device has already been shutdown and deactivated (as in
-             suspend) we must call DP.destroy here to avoid leaks
+              1. if the device has already been shutdown and deactivated (as in
+              suspend) we must call DP.destroy here to avoid leaks
 
-             2. if the device is successfully shutdown here then we must call
-             DP.destroy because no-one else will
+              2. if the device is successfully shutdown here then we must call
+              DP.destroy because no-one else will
 
-             3. if the device shutdown is rejected then we should leave the DP
-             alone and rely on the event thread calling us again later. *)
+              3. if the device shutdown is rejected then we should leave the DP
+              alone and rely on the event thread calling us again later. *)
           let domid = domid_of_uuid ~xs (uuid_of_string vm) in
           (* If the device is gone then we don't need to shut it down but we do
-             need to free any storage resources. *)
+              need to free any storage resources. *)
           let dev =
             try
               Some (device_by_id xc xs vm (device_kind_of ~xs vbd) (id_of vbd))
@@ -3939,7 +3939,7 @@ module VBD = struct
                   vm (id_of vbd) ;
               (* this happens on normal shutdown too *)
               (* Case (1): success; Case (2): success; Case (3): an exception is
-                 thrown *)
+                  thrown *)
               with_tracing ~task ~name:"VBD_device_shutdown" @@ fun () ->
               Xenops_task.with_subtask task
                 (Printf.sprintf "Vbd.clean_shutdown %s" (id_of vbd))
@@ -3950,7 +3950,7 @@ module VBD = struct
             )
             dev ;
           (* We now have a shutdown device but an active DP: we should destroy
-             the DP if the backend is of type VDI *)
+              the DP if the backend is of type VDI *)
           finally
             (fun () ->
               with_tracing ~task ~name:"VBD_device_release" (fun () ->
@@ -3994,11 +3994,14 @@ module VBD = struct
               ()
             )
             (fun () ->
-              with_tracing ~task ~name:"VBD_dp_destroy" @@ fun () ->
+              with_tracing ~task ~name:"VBD_deactivate" @@ fun () ->
+              let vmid = Storage.vm_of_domid domid in
               match (domid, backend) with
-              | Some x, None | Some x, Some (VDI _) ->
-                  Storage.dp_destroy task
-                    (Storage.id_of (string_of_int x) vbd.Vbd.id)
+              | Some x, Some (VDI path) ->
+                  let sr, vdi = Storage.get_disk_by_name task path in
+                  let dp = Storage.id_of (string_of_int x) vbd.id in
+                  Storage.deactivate task dp sr vdi vmid
+              (* We don't need to detach Local or CDROM *)
               | _ ->
                   ()
             )
@@ -4007,6 +4010,46 @@ module VBD = struct
           raise (Xenopsd_error (Device_detach_rejected ("VBD", id_of vbd, s)))
     )
 
+  let detach task vm vbd =
+    with_xc_and_xs (fun xc xs ->
+        let domid = domid_of_uuid ~xs (uuid_of_string vm) in
+        let dev =
+          try
+            Some (device_by_id xc xs vm (device_kind_of ~xs vbd) (id_of vbd))
+          with
+          | Xenopsd_error (Does_not_exist (_, _)) ->
+              debug "VM = %s; VBD = %s; Ignoring missing domain" vm (id_of vbd) ;
+              None
+          | Xenopsd_error Device_not_connected ->
+              debug "VM = %s; VBD = %s; Ignoring missing device" vm (id_of vbd) ;
+              None
+        in
+        let backend =
+          match dev with
+          | None ->
+              None
+          | Some dv -> (
+            match
+              Rpcmarshal.unmarshal typ_of_backend
+                (Device.Generic.get_private_key ~xs dv _vdi_id
+                |> Jsonrpc.of_string
+                )
+            with
+            | Ok x ->
+                x
+            | Error (`Msg m) ->
+                internal_error "Failed to unmarshal VBD backend: %s" m
+          )
+        in
+        with_tracing ~task ~name:"VBD_dp_destroy" @@ fun () ->
+        match (domid, backend) with
+        | Some x, None | Some x, Some (VDI _) ->
+            Storage.dp_destroy task (Storage.id_of (string_of_int x) vbd.Vbd.id)
+        | _ ->
+            ()
+    ) ;
+    cleanup_attached_vdis vm vbd.id
+
   let insert task vm vbd d =
     on_frontend
       (fun xc xs frontend_domid domain_type ->