Read out the actual metadata.

[virt-top.git] / virt-df / virt_df_lvm2.ml

diff --git a/virt-df/virt_df_lvm2.ml b/virt-df/virt_df_lvm2.ml
index 4247dc3..afcab66 100644 (file)
--- a/virt-df/virt_df_lvm2.ml
+++ b/virt-df/virt_df_lvm2.ml
@@ -24,33 +24,86 @@ open Printf
 open Virt_df_gettext.Gettext
 open Virt_df
 
+let plugin_name = "LVM2"
+
 let sector_size = 512
 let sector_size64 = 512L
 
-let pv_label_offset = sector_size64
-
-let rec probe_pv dev =
-  try ignore (read_pv_label dev); true
-  with _ -> false
+(* Probe to see if it's an LVM2 PV.  Look for the "LABELONE" label. *)
+let rec probe_pv lvm_plugin_id dev =
+  try
+    let uuid, _ = read_pv_label dev in
+    if debug then
+      eprintf "LVM2 detected PV UUID %s\n%!" uuid;
+    { lvm_plugin_id = lvm_plugin_id; pv_uuid = uuid }
+  with exn ->
+    if debug then prerr_endline (Printexc.to_string exn);
+    raise Not_found
 
 and read_pv_label dev =
-  (* Load the second sector. *)
-  let bits = dev#read_bitstring pv_label_offset sector_size in
+  (* Load the first 8 sectors.  I found by experimentation that
+   * the second sector contains the header ("LABELONE" etc) and
+   * the nineth sector contains some additional information about
+   * the location of the current metadata.
+   *)
+  let bits = dev#read_bitstring 0L (9 * sector_size) in
+
+  (*Bitmatch.hexdump_bitstring stdout bits;*)
 
   bitmatch bits with
-  | labelone : 8*8 : bitstring;                (* "LABELONE" *)
-    padding : 16*8 : bitstring;
+  | sector0 : sector_size*8 : bitstring; (* sector 0 *)
+    labelone : 8*8 : bitstring;                (* "LABELONE" *)
+    padding : 16*8 : bitstring;                (* Seems to contain something. *)
     lvm2_ver : 8*8 : bitstring;                (* "LVM2 001" *)
-    uuid : 32*8 : bitstring            (* UUID *)
+    uuid : 32*8 : bitstring;           (* UUID *)
+    padding2 : (sector_size-64)*8 : bitstring; (* to end of second sector *)
+    sector234567 : sector_size*8 * 6 : bitstring; (* sectors 2-6 *)
+    padding3 : 0x28*8 : bitstring;      (* start of sector 8 *)
+    metadata_offset : 32 : littleendian;(* metadata offset *)
+    padding4 : 4*8 : bitstring;
+    metadata_length : 32 : littleendian        (* length of metadata (bytes) *)
       when Bitmatch.string_of_bitstring labelone = "LABELONE" &&
-       Bitmatch.string_of_bitstring lvm2_ver = "LVM2 001" ->
-    uuid
+          Bitmatch.string_of_bitstring lvm2_ver = "LVM2 001" ->
+    let metadata_offset = metadata_offset +* 0x1000_l in
+    let metadata = read_metadata dev metadata_offset metadata_length in
+    (*prerr_endline metadata;*)
+    let uuid = Bitmatch.string_of_bitstring uuid in
+
+    uuid, metadata
+
   | _ ->
-    invalid_arg (sprintf "read_pv_label: %s: not an LVM2 physical volume"
-                  dev#name)
+    invalid_arg
+      (sprintf "LVM2: read_pv_label: %s: not an LVM2 physical volume" dev#name)
+
+and read_metadata dev offset32 len32 =
+  if debug then
+    eprintf "metadata: offset 0x%lx len %ld bytes\n" offset32 len32;
+
+  (* Check the offset and length are sensible. *)
+  let offset64 =
+    if offset32 <= Int32.max_int then Int64.of_int32 offset32
+    else invalid_arg "LVM2: read_metadata: metadata offset too large" in
+  let len64 =
+    if len32 <= 2_147_483_647_l then Int64.of_int32 len32
+    else invalid_arg "LVM2: read_metadata: metadata length too large" in
+
+  if offset64 <= 0x1200L || offset64 >= dev#size
+    || len64 <= 0L || offset64 +^ len64 >= dev#size then
+      invalid_arg "LVM2: read_metadata: bad metadata offset or length";
+
+  (* If it is outside the disk boundaries, this will throw an exception,
+   * otherwise it will read and return the metadata string.
+   *)
+  dev#read offset64 (Int64.to_int len64)
 
-let list_lvs devs = []
+(* We are passed a list of devices which we previously identified
+ * as PVs belonging to us.  From these produce a list of all LVs
+ * (as devices) and return them.  Note that we don't try to detect
+ * what is on these LVs - that will be done in the main code.
+ *)
+let list_lvs devs =
+  []
 
 (* Register with main code. *)
 let () =
-  lvm_type_register "LVM2" probe_pv list_lvs
+  lvm_type_register plugin_name probe_pv list_lvs