From: Richard W.M. Jones <rjones@redhat.com> <"Richard W.M. Jones <rjones@redhat.com>">
Date: Wed, 16 Apr 2008 11:08:54 +0000 (+0100)
Subject: LVM2 parsing complete and working.
X-Git-Tag: 1.0.4~24^2~7
X-Git-Url: http://git.annexia.org/?p=virt-top.git;a=commitdiff_plain;h=81593022de32f72e6dd7430519009cb70659eab6

LVM2 parsing complete and working.
---

diff --git a/virt-df/virt_df_lvm2.ml b/virt-df/virt_df_lvm2.ml
index 314586e..6a8f573 100644
--- a/virt-df/virt_df_lvm2.ml
+++ b/virt-df/virt_df_lvm2.ml
@@ -33,6 +33,63 @@ let plugin_name = "LVM2"
 let sector_size = 512
 let sector_size64 = 512L
 
+(*----------------------------------------------------------------------*)
+(* Block device which can do linear maps, same as the kernel dm-linear.c *)
+class linear_map_device name extent_size segments =
+  (* The segments are passed containing (start_extent, extent_count, ...)
+   * but it's easier to deal with (start_extent, end_extent, ...) so
+   * rewrite them.
+   *)
+  let segments = List.map
+    (fun (start_extent, extent_count, dev, pvoffset) ->
+       (start_extent, start_extent +^ extent_count, dev, pvoffset)
+    ) segments in
+
+  (* Calculate the size of the device (in bytes).  Note that because
+   * of the random nature of the mapping this doesn't imply that we can
+   * satisfy any read request up to the full size.
+   *)
+  let size_in_extents =
+    List.fold_left max 0L
+      (List.map (fun (_, end_extent, _, _) -> end_extent) segments) in
+  let size = size_in_extents *^ extent_size in
+object
+  inherit device
+  method name = name
+  method size = size
+
+  (* Read method checks which segment the request lies inside and
+   * maps it to the underlying device.  If there is no mapping then
+   * we have to return an error.
+   *
+   * The request must lie inside a single extent, otherwise this is
+   * also an error (XXX - should lift this restriction, however default
+   * extent size is 4 MB so we probably won't hit this very often).
+   *)
+  method read offset len =
+    let offset_in_extents = offset /^ extent_size in
+
+    (* Check we don't cross an extent boundary. *)
+    if (offset +^ Int64.of_int (len-1)) /^ extent_size <> offset_in_extents
+    then invalid_arg "linear_map_device: request crosses extent boundary";
+
+    if offset_in_extents < 0L || offset_in_extents >= size_in_extents then
+      invalid_arg "linear_map_device: read outside device";
+
+    let rec loop = function
+      | [] ->
+	  invalid_arg "linear_map_device: offset not mapped"
+      | (start_extent, end_extent, dev, pvoffset) :: rest ->
+	  eprintf "pvoffset = %Ld\n" pvoffset;
+	  if start_extent <= offset_in_extents &&
+	     offset_in_extents < end_extent
+	  then dev#read (offset +^ pvoffset *^ extent_size) len
+	  else loop rest
+    in
+    loop segments
+end
+
+(*----------------------------------------------------------------------*)
 (* Probe to see if it's an LVM2 PV. *)
 let rec probe_pv lvm_plugin_id dev =
   try
@@ -107,6 +164,7 @@ and read_metadata dev offset32 len32 =
    *)
   dev#read offset64 (Int64.to_int len64)
 
+(*----------------------------------------------------------------------*)
 (* 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
@@ -129,13 +187,13 @@ let rec list_lvs devs =
 	     dev)
   ) pvs in
 
-  (* Print the parsed metadata.
-  List.iter (
-    fun (uuid, (metadata, dev)) ->
-      eprintf "metadata for UUID %s:\n" uuid;
-      output_metadata stderr metadata
-  ) pvs;
-  *)
+  (* Print the parsed metadata. *)
+  if !debug then
+    List.iter (
+      fun (uuid, (metadata, dev)) ->
+	eprintf "metadata for PV UUID %s on %s:\n" uuid dev#name;
+	output_metadata stderr metadata
+    ) pvs;
 
   (* Scan for volume groups.  The first entry in the metadata
    * appears to be the volume group name.  This gives us a
@@ -191,18 +249,76 @@ let rec list_lvs devs =
   and get_meta field meta =
     match List.assoc field meta with
     | Metadata md -> md
-    | _ -> raise Not_found in
+    | _ -> raise Not_found
+  and get_stripes field meta =		(* List of (string,int) pairs. *)
+    match List.assoc field meta with
+    | List xs ->
+	let rec loop = function
+	  | [] -> []
+	  | String pvname :: Int offset :: xs ->
+	      (pvname, offset) :: loop xs
+	  | _ -> raise Not_found
+	in
+	loop xs
+    | _ -> raise Not_found
   in
 
+  (* The volume groups refer to the physical volumes using their
+   * own naming system ("pv0", "pv1", etc.) instead of PV UUIDs.
+   *
+   * Each PV also has a start (in sectors) & count (in extents)
+   * of the writable area (the bit after the superblock and metadata)
+   * which normally starts at sector 384.
+   *
+   * Create a PV device (simple offset + size) and a map from PV
+   * names to these devices.
+   *)
+  let vgs = List.map (
+    fun (vgname, (pvuuids, vgmeta)) ->
+      let pvdevs, extent_size =
+	try
+	  (* NB: extent_size is in sectors here - we convert to bytes. *)
+	  let extent_size = get_int "extent_size" vgmeta 0 (1024*1024) in
+	  let extent_size = Int64.of_int extent_size *^ sector_size64 in
+
+	  (* Get the physical_volumes section of the metadata. *)
+	  let pvdevs = get_meta "physical_volumes" vgmeta in
+
+	  List.filter_map (
+	    function
+	    | (pvname, Metadata meta) ->
+		(* Get the UUID. *)
+		let pvuuid = get_string "id" meta in
+		let pvuuid = canonical_uuid pvuuid in
+
+		(* Get the underlying physical device. *)
+		let _, dev = List.assoc pvuuid pvs in
+
+		(* Construct a PV device. *)
+		let pe_start = get_int64 "pe_start" meta in
+		let pe_start = pe_start *^ sector_size64 in
+		let pe_count = get_int64 "pe_count" meta in
+		let pe_count = pe_count *^ extent_size in
+		let pvdev = new offset_device pvuuid pe_start pe_count dev in
+
+		Some (pvname, pvdev)
+	    | _ ->
+		None
+	  ) pvdevs, extent_size
+	with
+	  (* Something went wrong - just return an empty map. *)
+	  Not_found -> [], 0L in
+      (vgname, (pvuuids, vgmeta, pvdevs, extent_size))
+  ) vgs in
+
   (* Scan for logical volumes.  Each VG contains several LVs.
    * This gives us a list of LVs within each VG (hence extends
    * the vgs variable).
    *)
   let vgs = List.map (
-    fun (vgname, (pvuuids, vgmeta)) ->
+    fun (vgname, (pvuuids, vgmeta, pvdevs, extent_size)) ->
       let lvs =
 	try
-	  let extent_size = get_int "extent_size" vgmeta 0 (256*1024) in
 	  let lvs = get_meta "logical_volumes" vgmeta in
 	  let lvs = List.filter_map (
 	    function
@@ -225,15 +341,29 @@ let rec list_lvs devs =
 			 let extent_count =
 			   get_int64 "extent_count" segmeta in
 			 let segtype = get_string "type" segmeta in
+
+			 (* Can only handle striped segments at the
+			  * moment. XXX
+			  *)
 			 if segtype <> "striped" then raise Not_found;
+
 			 let stripe_count =
 			   get_int "stripe_count" segmeta 0 1024 in
-			 (* let stripes =  in *)
+			 let stripes = get_stripes "stripes" segmeta in
+
+			 if List.length stripes <> stripe_count then
+			   raise Not_found;
 
-			 (start_extent, extent_count, stripe_count)
+			 (* Can only handle linear striped segments at
+			  * the moment. XXX
+			  *)
+			 if stripe_count <> 1 then raise Not_found;
+			 let pvname, pvoffset = List.hd stripes in
+
+			 (start_extent, extent_count, pvname, pvoffset)
 		     ) segments in
 
-		   Some (lvname, (lvmeta, segments))
+		   Some (lvname, segments)
 		 with
 		   (* Something went wrong with segments - omit this LV. *)
 		   Not_found -> None)
@@ -245,19 +375,58 @@ let rec list_lvs devs =
 	  Not_found ->
 	    (* Something went wrong - assume no LVs found. *)
 	    [] in
-      (vgname, (pvuuids, vgmeta, lvs))
+      (vgname, (pvuuids, vgmeta, pvdevs, extent_size, lvs))
   ) vgs in
 
   (* Print the LVs. *)
-  if !debug then
+  if !debug then (
     List.iter (
-      fun (vgname, (pvuuids, vgmeta, lvs)) ->
-	let lvnames = List.map fst lvs in
-	eprintf "VG %s contains LVs: %s\n%!" vgname (String.concat ", " lvnames)
+      fun (vgname, (pvuuids, vgmeta, pvdevs, extent_size, lvs)) ->
+	eprintf "VG %s: (extent_size = %Ld bytes)\n" vgname extent_size;
+	List.iter (
+	  fun (lvname, segments) ->
+	    eprintf "  %s/%s:\n" vgname lvname;
+	    List.iter (
+	      fun (start_extent, extent_count, pvname, pvoffset) ->
+		eprintf "    start %Ld count %Ld at %s:%Ld\n"
+		  start_extent extent_count pvname pvoffset
+	    ) segments
+	) lvs
     ) vgs;
+    flush stderr
+  );
+
+  (* Finally we can set up devices for the LVs. *)
+  let lvs =
+    List.map (
+      fun (vgname, (pvuuid, vgmeta, pvdevs, extent_size, lvs)) ->
+	try
+	  List.map (
+	    fun (lvname, segments) ->
+	      let name = vgname ^ "/" ^ lvname in
+	      let segments = List.map (
+		fun (start_extent, extent_count, pvname, pvoffset) ->
+		  (* Get the PV device. *)
+		  let pvdev = List.assoc pvname pvdevs in
+
+		  (* Extents                 mapped to:             *)
+		  (start_extent, extent_count,          pvdev, pvoffset)
+	      ) segments in
+
+	      (* Create a linear mapping device. *)
+	      let lv_dev = new linear_map_device name extent_size segments in
+
+	      { lv_dev = lv_dev }
+	  ) lvs
+	with
+	  Not_found -> []
+    ) vgs in
+  let lvs = List.concat lvs in
 
-  []
+  (* Return the list of LV devices. *)
+  lvs
 
+(*----------------------------------------------------------------------*)
 (* Register with main code. *)
 let () =
   lvm_type_register plugin_name probe_pv list_lvs