(* 'df' command for virtual domains.
   (C) Copyright 2007 Richard W.M. Jones, Red Hat Inc.
   http://libvirt.org/

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

   Support for EXT2/EXT3 filesystems.
*)

open Unix
open Printf

open Diskimage_impl

open Int63.Operators

let ( +* ) = Int32.add
let ( -* ) = Int32.sub
let ( ** ) = Int32.mul
let ( /* ) = Int32.div

(* The fields in an ext2/3 superblock. *)
type ext2_sb = {
  s_inodes_count : int32;
  s_blocks_count : int32;
  s_r_blocks_count : int32;
  s_free_blocks_count : int32;
  s_free_inodes_count : int32;
  s_first_data_block : int32;
  s_log_block_size : int32;
  s_log_frag_size : int32;
  s_blocks_per_group : int32;
  s_frags_per_group : int32;
  s_inodes_per_group : int32;
  s_mtime : int32;
  s_wtime : int32;
  s_mnt_count : int;
  s_max_mnt_count : int;
  s_state : int;
  s_errors : int;
  s_minor_rev_level : int;
  s_lastcheck : int32;
  s_checkinterval : int32;
  s_creator_os : int32;
  s_rev_level : int32;
  s_def_resuid : int;
  s_def_resgid : int;
  s_first_ino : int32;
  s_inode_size : int;
  s_block_group_nr : int;
  s_feature_compat : int32;
  s_feature_incompat : int32;
  s_feature_ro_compat : int32;
  s_uuid : string;
  s_volume_name : string;
  s_last_mounted : string;
  s_algorithm_usage_bitmap : int32;
  s_prealloc_blocks : int;
  s_prealloc_dir_blocks : int;
  s_reserved_gdt_blocks : int;
  s_journal_uuid : string;
  s_journal_inum : int32;
  s_journal_dev : int32;
  s_last_orphan : int32;
  s_hash_seed0 : int32;
  s_hash_seed1 : int32;
  s_hash_seed2 : int32;
  s_hash_seed3 : int32;
  s_def_hash_version : int;
  s_reserved_char_pad : int;
  s_reserved_word_pad : int;
  s_default_mount_opts : int32;
  s_first_meta_bg : int32;

  (* Computed fields, don't appear in superblock: *)
  block_size : int63;
  groups_count : int63;
}

(* Private data functions. *)
let attach_private_data, get_private_data =
  private_data_functions (fun {fs_cb = {fs_cb_uq = u}} -> u)

let id = "ext2"
let superblock_offset = ~^1024
let superblock_len = ~^1024

(* Parse ext2/3 superblock and return a big structure containing
 * all the fields.  Also there are some extra fields which don't
 * appear in the superblock itself, but are computed from other fields.
 *
 * If the device doesn't contain a superblock, raises Not_found.
 *)
let parse_ext2_sb dev =
  (* Load the superblock. *)
  let bits = dev#read_bitstring superblock_offset superblock_len in

  (* The structure is straight from /usr/include/linux/ext3_fs.h *)
  bitmatch bits with
  | { s_inodes_count : 32 : littleendian;	(* Inodes count *)
      s_blocks_count : 32 : littleendian;	(* Blocks count *)
      s_r_blocks_count : 32 : littleendian;	(* Reserved blocks count *)
      s_free_blocks_count : 32 : littleendian;	(* Free blocks count *)
      s_free_inodes_count : 32 : littleendian;	(* Free inodes count *)
      s_first_data_block : 32 : littleendian;	(* First Data Block *)
      s_log_block_size : 32 : littleendian;	(* Block size *)
      s_log_frag_size : 32 : littleendian;	(* Fragment size *)
      s_blocks_per_group : 32 : littleendian;	(* # Blocks per group *)
      s_frags_per_group : 32 : littleendian;	(* # Fragments per group *)
      s_inodes_per_group : 32 : littleendian;	(* # Inodes per group *)
      s_mtime : 32 : littleendian;		(* Mount time *)
      s_wtime : 32 : littleendian;		(* Write time *)
      s_mnt_count : 16 : littleendian;		(* Mount count *)
      s_max_mnt_count : 16 : littleendian;	(* Maximal mount count *)
      0xef53 : 16 : littleendian;		(* Magic signature *)
      s_state : 16 : littleendian;		(* File system state *)
      s_errors : 16 : littleendian;		(* Behaviour when detecting errors *)
      s_minor_rev_level : 16 : littleendian;	(* minor revision level *)
      s_lastcheck : 32 : littleendian;		(* time of last check *)
      s_checkinterval : 32 : littleendian;	(* max. time between checks *)
      s_creator_os : 32 : littleendian;		(* OS *)
      s_rev_level : 32 : littleendian;		(* Revision level *)
      s_def_resuid : 16 : littleendian;		(* Default uid for reserved blocks *)
      s_def_resgid : 16 : littleendian;		(* Default gid for reserved blocks *)
      s_first_ino : 32 : littleendian;		(* First non-reserved inode *)
      s_inode_size : 16 : littleendian;		(* size of inode structure *)
      s_block_group_nr : 16 : littleendian;	(* block group # of this superblock *)
      s_feature_compat : 32 : littleendian;	(* compatible feature set *)
      s_feature_incompat : 32 : littleendian;	(* incompatible feature set *)
      s_feature_ro_compat : 32 : littleendian;	(* readonly-compatible feature set *)
      s_uuid : 128 : string;		        (* 128-bit uuid for volume *)
      s_volume_name : 128 : string;	        (* volume name *)
      s_last_mounted : 512 : string;	        (* directory where last mounted *)
      s_algorithm_usage_bitmap : 32 : littleendian; (* For compression *)
      s_prealloc_blocks : 8;	                (* Nr of blocks to try to preallocate*)
      s_prealloc_dir_blocks : 8;	        (* Nr to preallocate for dirs *)
      s_reserved_gdt_blocks : 16 : littleendian;(* Per group desc for online growth *)
      s_journal_uuid : 128 : string;	        (* uuid of journal superblock *)
      s_journal_inum : 32 : littleendian;	(* inode number of journal file *)
      s_journal_dev : 32 : littleendian;	(* device number of journal file *)
      s_last_orphan : 32 : littleendian;	(* start of list of inodes to delete *)
      s_hash_seed0 : 32 : littleendian;		(* HTREE hash seed *)
      s_hash_seed1 : 32 : littleendian;
      s_hash_seed2 : 32 : littleendian;
      s_hash_seed3 : 32 : littleendian;
      s_def_hash_version : 8;	                (* Default hash version to use *)
      s_reserved_char_pad : 8;
      s_reserved_word_pad : 16 : littleendian;
      s_default_mount_opts : 32 : littleendian;
      s_first_meta_bg : 32 : littleendian } ->	(* First metablock block group *)

      (* Work out the block size in bytes. *)
      let block_size = ~^1024 <^< Int32.to_int s_log_block_size in

      (* Number of groups. *)
      let groups_count =
	Int63.of_int32 (
	  (s_blocks_count -* s_first_data_block -* 1l)
          /* s_blocks_per_group +* 1l
	) in

      { s_inodes_count = s_inodes_count;
	s_blocks_count = s_blocks_count;
	s_r_blocks_count = s_r_blocks_count;
	s_free_blocks_count = s_free_blocks_count;
	s_free_inodes_count = s_free_inodes_count;
	s_first_data_block = s_first_data_block;
	s_log_block_size = s_log_block_size;
	s_log_frag_size = s_log_frag_size;
	s_blocks_per_group = s_blocks_per_group;
	s_frags_per_group = s_frags_per_group;
	s_inodes_per_group = s_inodes_per_group;
	s_mtime = s_mtime;
	s_wtime = s_wtime;
	s_mnt_count = s_mnt_count;
	s_max_mnt_count = s_max_mnt_count;
	s_state = s_state;
	s_errors = s_errors;
	s_minor_rev_level = s_minor_rev_level;
	s_lastcheck = s_lastcheck;
	s_checkinterval = s_checkinterval;
	s_creator_os = s_creator_os;
	s_rev_level = s_rev_level;
	s_def_resuid = s_def_resuid;
	s_def_resgid = s_def_resgid;
	s_first_ino = s_first_ino;
	s_inode_size = s_inode_size;
	s_block_group_nr = s_block_group_nr;
	s_feature_compat = s_feature_compat;
	s_feature_incompat = s_feature_incompat;
	s_feature_ro_compat = s_feature_ro_compat;
	s_uuid = s_uuid;
	s_volume_name = s_volume_name;
	s_last_mounted = s_last_mounted;
	s_algorithm_usage_bitmap = s_algorithm_usage_bitmap;
	s_prealloc_blocks = s_prealloc_blocks;
	s_prealloc_dir_blocks = s_prealloc_dir_blocks;
	s_reserved_gdt_blocks = s_reserved_gdt_blocks;
	s_journal_uuid = s_journal_uuid;
	s_journal_inum = s_journal_inum;
	s_journal_dev = s_journal_dev;
	s_last_orphan = s_last_orphan;
	s_hash_seed0 = s_hash_seed0;
	s_hash_seed1 = s_hash_seed1;
	s_hash_seed2 = s_hash_seed2;
	s_hash_seed3 = s_hash_seed3;
	s_def_hash_version = s_def_hash_version;
	s_reserved_char_pad = s_reserved_char_pad;
	s_reserved_word_pad = s_reserved_word_pad;
	s_default_mount_opts = s_default_mount_opts;
	s_first_meta_bg = s_first_meta_bg;
	block_size = block_size;
	groups_count = groups_count }

  | { _ } ->
      raise Not_found			(* Not an EXT2/3 superblock. *)

let rec probe dev =
  let sb = parse_ext2_sb dev in		(* May raise Not_found. *)

(*
      (* Number of group descriptors per block. *)
      let s_inodes_per_block = s_blocksize / 
	let s_desc_per_block = block_size / s_inodes_per_block in
	let db_count =
	  (s_groups_count +^ s_desc_per_block -^ 1L)
	  /^ s_desc_per_block
*)

   (* Calculate the block overhead (used by superblocks, inodes, etc.)
    * See fs/ext2/super.c.
    *)
   let overhead = Int63.of_int32 sb.s_first_data_block in
   let overhead = (* XXX *) overhead in

   (* The blocksize of the filesystem is likely to be quite different
    * from that of the underlying device, so create an overlay device
    * with the natural filesystem blocksize.
    *)
   let fs_dev = new blocksize_overlay sb.block_size dev in

   let fs = {
     fs_cb = callbacks ();
     fs_dev = fs_dev;

     fs_blocksize = sb.block_size;
     fs_blocks_total = Int63.of_int32 sb.s_blocks_count -^ overhead;

     fs_is_swap = false;

     fs_blocks_reserved = Int63.of_int32 sb.s_r_blocks_count;
     fs_blocks_avail = Int63.of_int32 sb.s_free_blocks_count;
     fs_blocks_used =
       Int63.of_int32 sb.s_blocks_count -^ overhead
       -^ Int63.of_int32 sb.s_free_blocks_count;
     fs_inodes_total = Int63.of_int32 sb.s_inodes_count;
     fs_inodes_reserved = ~^0;	(* XXX? *)
     fs_inodes_avail = Int63.of_int32 sb.s_free_inodes_count;
     fs_inodes_used = Int63.of_int32 sb.s_inodes_count
       (*-^ 0*)
       -^ Int63.of_int32 sb.s_free_inodes_count;
   } in

   (* Attach the original superblock as private data so we can
    * get to it quickly in other callbacks.
    *)
   attach_private_data fs sb;
   fs

and offset_is_free _ _ = false

and callbacks =
  let i = ref 0 in
  fun () -> {
    fs_cb_uq = (incr i; !i);
    fs_cb_name = id;
    fs_cb_printable_name = "Linux ext2/3";
    fs_cb_offset_is_free = offset_is_free;
  }

(* Register the plugin. *)
let () = register_plugin ~filesystem:probe id