CA-402901: Update leaked dp to Sr (#6171)

When add leaked datapath:
1. add leaked datapath to Sr.vdis
2. write to db file
3. log enhance

If there are storage exceptions raised when destroying datapath, the
procedure fails and the state of VDI becomes incorrect, which leads to
various abnormalresults in subsequent operations. To handle this, the
leaked datapath is designed to redestroy the datapath and refresh the
state before next storage operation via function
remove_datapaths_andthen_nolock. But this mechanism doesn't take effect
in current code.
This commit is to fix this bug. leaked datapath should be added to
Sr.vdis to make the leaked datapath really work. And write to db file to
avoid losing the leaked datapath if xapi restarts.

ocaml/xapi/storage_impl.ml

@@ -459,6 +459,10 @@ functor
         List.fold_left perform_one vdi_t ops
 
       let perform_nolock context ~dbg ~dp ~sr ~vdi ~vm this_op =
+        let __FUNCTION__ = "perform_nolock" in
+        debug "%s dp=%s, sr=%s, vdi=%s, vm=%s, op=%s" __FUNCTION__ dp
+          (s_of_sr sr) (s_of_vdi vdi) (s_of_vm vm)
+          (Vdi_automaton.string_of_op this_op) ;
         match Host.find sr !Host.host with
         | None ->
             raise (Storage_error (Sr_not_attached (s_of_sr sr)))
@@ -479,6 +483,15 @@ functor
                    						   superstate to superstate'. These may fail: if so we revert the
                    						   datapath+VDI state to the most appropriate value. *)
                 let ops = Vdi_automaton.( - ) superstate superstate' in
+                debug "%s %s -> %s: %s" __FUNCTION__
+                  (Vdi_automaton.string_of_state superstate)
+                  (Vdi_automaton.string_of_state superstate')
+                  (String.concat ", "
+                     (List.map
+                        (fun (op, _) -> Vdi_automaton.string_of_op op)
+                        ops
+                     )
+                  ) ;
                 side_effects context dbg dp sr sr_t vdi vdi_t vm ops
               with e ->
                 let e =
@@ -535,7 +548,8 @@ functor
                     )
                 with e ->
                   if not allow_leak then (
-                    ignore (Vdi.add_leaked dp vdi_t) ;
+                    Sr.replace vdi (Vdi.add_leaked dp vdi_t) sr_t ;
+                    Everything.to_file !host_state_path (Everything.make ()) ;
                     raise e
                   ) else (
                     (* allow_leak means we can forget this dp *)