v2v: Abstract Convert_* modules from core v2v code.

Previously the core virt-v2v code had to know which Convert_* module
to call for each guest type (based on inspection).  After this change
the core code doesn't need to know that, but instead Convert_* modules
register their interest in particular guest types.

v2v/convert_linux.ml

@@ -56,8 +56,7 @@ let string_of_kernel_info ki =
     ki.ki_supports_virtio ki.ki_is_xen_kernel
 
 (* The conversion function. *)
-let rec convert ~keep_serial_console verbose (g : G.guestfs)
-    inspect source =
+let rec convert ~verbose ~keep_serial_console (g : G.guestfs) inspect source =
   (*----------------------------------------------------------------------*)
   (* Inspect the guest first.  We already did some basic inspection in
    * the common v2v.ml code, but that has to deal with generic guests
@@ -1242,3 +1241,13 @@ let rec convert ~keep_serial_console verbose (g : G.guestfs)
   } in
 
   guestcaps
+
+let () =
+  let matching = function
+    | { i_type = "linux";
+        i_distro = ("fedora"
+                       | "rhel" | "centos" | "scientificlinux" | "redhat-based"
+                       | "sles" | "suse-based" | "opensuse") } -> true
+    | _ -> false
+  in
+  Modules_list.register_convert_module matching "enterprise-linux" convert

v2v/convert_linux.mli

@@ -15,5 +15,3 @@
  * with this program; if not, write to the Free Software Foundation, Inc.,
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  *)
-
-val convert : keep_serial_console:bool -> bool -> Guestfs.guestfs -> Types.inspect -> Types.source -> Types.guestcaps

v2v/convert_windows.ml

@@ -41,7 +41,7 @@ module G = Guestfs
 
 type ('a, 'b) maybe = Either of 'a | Or of 'b
 
-let convert verbose (g : G.guestfs) inspect source =
+let convert ~verbose ~keep_serial_console (g : G.guestfs) inspect source =
   (* Get the data directory. *)
   let virt_tools_data_dir =
     try Sys.getenv "VIRT_TOOLS_DATA_DIR"
@@ -477,3 +477,10 @@ echo uninstalling Xen PV driver
   } in
 
   guestcaps
+
+let () =
+  let matching = function
+    | { i_type = "windows" } -> true
+    | _ -> false
+  in
+  Modules_list.register_convert_module matching "windows" convert

v2v/convert_windows.mli

@@ -15,5 +15,3 @@
  * with this program; if not, write to the Free Software Foundation, Inc.,
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  *)
-
-val convert : bool -> Guestfs.guestfs -> Types.inspect -> Types.source -> Types.guestcaps

v2v/modules_list.ml

@@ -26,3 +26,20 @@ and register_output_module name =
 
 let input_modules () = List.sort compare !input_modules
 and output_modules () = List.sort compare !output_modules
+
+type conversion_fn =
+  verbose:bool -> keep_serial_console:bool ->
+  Guestfs.guestfs -> Types.inspect -> Types.source -> Types.guestcaps
+
+let convert_modules = ref []
+
+let register_convert_module inspect_fn name conversion_fn =
+  convert_modules := (inspect_fn, (name, conversion_fn)) :: !convert_modules
+
+let find_convert_module inspect =
+  let rec loop = function
+    | [] -> raise Not_found
+    | (inspect_fn, ret) :: _ when inspect_fn inspect -> ret
+    | _ :: rest -> loop rest
+  in
+  loop !convert_modules

v2v/modules_list.mli

@@ -16,7 +16,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  *)
 
-(** List of input and output modules. *)
+(** List of input, output and conversion modules. *)
 
 val register_input_module : string -> unit
 (** Register an input module by name. *)
@@ -29,3 +29,17 @@ val input_modules : unit -> string list
 
 val output_modules : unit -> string list
 (** Return the list of output modules. *)
+
+type conversion_fn =
+  verbose:bool -> keep_serial_console:bool ->
+  Guestfs.guestfs -> Types.inspect -> Types.source -> Types.guestcaps
+
+val register_convert_module : (Types.inspect -> bool) -> string -> conversion_fn -> unit
+(** [register_convert_module inspect_fn name fn] registers a
+    conversion function [fn] that can accept any guest that matches
+    the [inspect_fn] function. *)
+
+val find_convert_module : Types.inspect -> string * conversion_fn
+(** [find_convert_module inspect] returns the name and conversion
+    function for the guest with inspection data in [inspect], else
+    throws [Not_found]. *)

v2v/v2v.ml

@@ -192,19 +192,16 @@ let rec main () =
       msg (f_"Converting %s to run on KVM") prod
     );
 
-    match inspect.i_type, inspect.i_distro with
-    | "linux", ("fedora"
-                   | "rhel" | "centos" | "scientificlinux" | "redhat-based"
-                   | "sles" | "suse-based" | "opensuse") ->
-        (* RHEV doesn't support serial console so remove any on conversion. *)
-        let keep_serial_console = output#keep_serial_console in
-        Convert_linux.convert ~keep_serial_console verbose g inspect source
+    (* RHEV doesn't support serial console so remove any on conversion. *)
+    let keep_serial_console = output#keep_serial_console in
 
-    | "windows", _ -> Convert_windows.convert verbose g inspect source
-
-    | typ, distro ->
-      error (f_"virt-v2v is unable to convert this guest type (%s/%s)")
-        typ distro in
+    let conversion_name, convert =
+      try Modules_list.find_convert_module inspect
+      with Not_found ->
+        error (f_"virt-v2v is unable to convert this guest type (%s/%s)")
+          inspect.i_type inspect.i_distro in
+    if verbose then printf "picked conversion module %s\n%!" conversion_name;
+    convert ~verbose ~keep_serial_console g inspect source in
 
   if do_copy then (
     (* Doing fstrim on all the filesystems reduces the transfer size