resize: Get the partition table type of the source disk earlier.

Also we only permit MBR (DOS) and GPT partition tables.  In theory
previously we allowed other partition table types, but it is unlikely
that it would have worked in reality.

diff --git a/resize/resize.ml b/resize/resize.ml
index ef279cd..275e7e0 100644 (file)
--- a/resize/resize.ml
+++ b/resize/resize.ml
@@ -258,6 +258,19 @@ let () =
     error "%s: file is too small to be a disk image (%Ld bytes)"
       outfile outsize
 
+(* Get the source partition type. *)
+type parttype = MBR | GPT        (* Only these are supported by virt-resize. *)
+
+let parttype, parttype_string =
+  let pt = g#part_get_parttype "/dev/sda" in
+  if debug then eprintf "partition table type: %s\n%!" pt;
+
+  match pt with
+  | "msdos" -> MBR, "msdos"
+  | "gpt" -> GPT, "gpt"
+  | _ ->
+    error "%s: unknown partition table type\nvirt-resize only supports MBR (DOS) and GPT partition tables." infile
+
 (* Build a data structure describing the source disk's partition layout. *)
 type partition = {
   p_name : string;               (* Device name, like /dev/sda1. *)
@@ -761,10 +774,7 @@ let () =
  * carefully move the backup GPT (and rewrite those references) or
  * recreate the whole partition table from scratch.
  *)
-let g, parttype =
-  let parttype = g#part_get_parttype "/dev/sda" in
-  if debug then eprintf "partition table type: %s\n%!" parttype;
-
+let g =
   (* Try hard to initialize the partition table.  This might involve
    * relaunching another handle.
    *)
@@ -774,7 +784,7 @@ let g, parttype =
   let last_error = ref "" in
   let rec initialize_partition_table g attempts =
     let ok =
-      try g#part_init "/dev/sdb" parttype; true
+      try g#part_init "/dev/sdb" parttype_string; true
       with G.Error error -> last_error := error; false in
     if ok then g, true
     else if attempts > 0 then (
@@ -792,7 +802,7 @@ let g, parttype =
   if not ok then
     error "Failed to initialize the partition table on the target disk.  You need to wipe or recreate the target disk and then run virt-resize again.\n\nThe underlying error was: %s" !last_error;
 
-  g, parttype
+  g
 
 (* Copy the bootloader across.
  * Don't disturb the partition table that we just wrote.
@@ -807,7 +817,7 @@ let () =
     ignore (g#pwrite_device "/dev/sdb" bootsect 0L);
 
     let start =
-      if parttype <> "gpt" then 512L
+      if parttype <> GPT then 512L
       else
         (* XXX With 4K sectors does GPT just fit more entries in a
          * sector, or does it always use 34 sectors?