/*
 *  nilfs2.c - New Implementation of Log filesystem
 *
 *  Written by Jiro SEKIBA <jir@unicus.jp>
 *
 *  Copyright (C) 2003,2004,2005,2007,2008,2010  Free Software Foundation, Inc.
 *
 *  GRUB 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 3 of the License, or
 *  (at your option) any later version.
 *
 *  GRUB 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 GRUB.  If not, see <https://www.gnu.org/licenses/>.
 */


/* Filetype information as used in inodes.  */
#define FILETYPE_INO_MASK	0170000
#define FILETYPE_INO_REG	0100000
#define FILETYPE_INO_DIRECTORY	0040000
#define FILETYPE_INO_SYMLINK	0120000

#include <grub/err.h>
#include <grub/file.h>
#include <grub/mm.h>
#include <grub/misc.h>
#include <grub/disk.h>
#include <grub/types.h>
#include <grub/fshelp.h>
#include <r_types.h>

#define NILFS_INODE_BMAP_SIZE	7

#define NILFS_SUPORT_REV	2

/* Magic value used to identify an nilfs2 filesystem.  */
#define	NILFS2_SUPER_MAGIC	0x3434
/* nilfs btree node flag.  */
#define NILFS_BTREE_NODE_ROOT   0x01

/* nilfs btree node level. */
#define NILFS_BTREE_LEVEL_DATA          0
#define NILFS_BTREE_LEVEL_NODE_MIN      (NILFS_BTREE_LEVEL_DATA + 1)
#define NILFS_BTREE_LEVEL_MAX           14

struct grub_nilfs2_inode
{
  grub_uint64_t i_blocks;
  grub_uint64_t i_size;
  grub_uint64_t i_ctime;
  grub_uint64_t i_mtime;
  grub_uint32_t i_ctime_nsec;
  grub_uint32_t i_mtime_nsec;
  grub_uint32_t i_uid;
  grub_uint32_t i_gid;
  grub_uint16_t i_mode;
  grub_uint16_t i_links_count;
  grub_uint32_t i_flags;
  grub_uint64_t i_bmap[NILFS_INODE_BMAP_SIZE];
#define i_device_code	i_bmap[0]
  grub_uint64_t i_xattr;
  grub_uint32_t i_generation;
  grub_uint32_t i_pad;
};

struct grub_nilfs2_super_root
{
  grub_uint32_t sr_sum;
  grub_uint16_t sr_bytes;
  grub_uint16_t sr_flags;
  grub_uint64_t sr_nongc_ctime;
  struct grub_nilfs2_inode sr_dat;
  struct grub_nilfs2_inode sr_cpfile;
  struct grub_nilfs2_inode sr_sufile;
};

struct grub_nilfs2_super_block
{
  grub_uint32_t s_rev_level;
  grub_uint16_t s_minor_rev_level;
  grub_uint16_t s_magic;
  grub_uint16_t s_bytes;
  grub_uint16_t s_flags;
  grub_uint32_t s_crc_seed;
  grub_uint32_t s_sum;
  grub_uint32_t s_log_block_size;
  grub_uint64_t s_nsegments;
  grub_uint64_t s_dev_size;
  grub_uint64_t s_first_data_block;
  grub_uint32_t s_blocks_per_segment;
  grub_uint32_t s_r_segments_percentage;
  grub_uint64_t s_last_cno;
  grub_uint64_t s_last_pseg;
  grub_uint64_t s_last_seq;
  grub_uint64_t s_free_blocks_count;
  grub_uint64_t s_ctime;
  grub_uint64_t s_mtime;
  grub_uint64_t s_wtime;
  grub_uint16_t s_mnt_count;
  grub_uint16_t s_max_mnt_count;
  grub_uint16_t s_state;
  grub_uint16_t s_errors;
  grub_uint64_t s_lastcheck;
  grub_uint32_t s_checkinterval;
  grub_uint32_t s_creator_os;
  grub_uint16_t s_def_resuid;
  grub_uint16_t s_def_resgid;
  grub_uint32_t s_first_ino;
  grub_uint16_t s_inode_size;
  grub_uint16_t s_dat_entry_size;
  grub_uint16_t s_checkpoint_size;
  grub_uint16_t s_segment_usage_size;
  grub_uint8_t s_uuid[16];
  char s_volume_name[16];
  char s_last_mounted[64];
  grub_uint32_t s_c_interval;
  grub_uint32_t s_c_block_max;
  grub_uint32_t s_reserved[192];
};
R_PACKED (
struct grub_nilfs2_dir_entry
{
  grub_uint64_t inode;
  grub_uint16_t rec_len;
  grub_uint8_t name_len;
  grub_uint8_t file_type;
});

enum
{
  NILFS_FT_UNKNOWN,
  NILFS_FT_REG_FILE,
  NILFS_FT_DIR,
  NILFS_FT_CHRDEV,
  NILFS_FT_BLKDEV,
  NILFS_FT_FIFO,
  NILFS_FT_SOCK,
  NILFS_FT_SYMLINK,
  NILFS_FT_MAX
};

struct grub_nilfs2_finfo
{
  grub_uint64_t fi_ino;
  grub_uint64_t fi_cno;
  grub_uint32_t fi_nblocks;
  grub_uint32_t fi_ndatablk;
};

struct grub_nilfs2_binfo_v
{
  grub_uint64_t bi_vblocknr;
  grub_uint64_t bi_blkoff;
};

struct grub_nilfs2_binfo_dat
{
  grub_uint64_t bi_blkoff;
  grub_uint8_t bi_level;
  grub_uint8_t bi_pad[7];
};

union grub_nilfs2_binfo
{
  struct grub_nilfs2_binfo_v bi_v;
  struct grub_nilfs2_binfo_dat bi_dat;
};

struct grub_nilfs2_segment_summary
{
  grub_uint32_t ss_datasum;
  grub_uint32_t ss_sumsum;
  grub_uint32_t ss_magic;
  grub_uint16_t ss_bytes;
  grub_uint16_t ss_flags;
  grub_uint64_t ss_seq;
  grub_uint64_t ss_create;
  grub_uint64_t ss_next;
  grub_uint32_t ss_nblocks;
  grub_uint32_t ss_nfinfo;
  grub_uint32_t ss_sumbytes;
  grub_uint32_t ss_pad;
};

struct grub_nilfs2_btree_node
{
  grub_uint8_t bn_flags;
  grub_uint8_t bn_level;
  grub_uint16_t bn_nchildren;
  grub_uint32_t bn_pad;
};

struct grub_nilfs2_palloc_group_desc
{
  grub_uint32_t pg_nfrees;
};

struct grub_nilfs2_dat_entry
{
  grub_uint64_t de_blocknr;
  grub_uint64_t de_start;
  grub_uint64_t de_end;
  grub_uint64_t de_rsv;
};

struct grub_nilfs2_snapshot_list
{
  grub_uint64_t ssl_next;
  grub_uint64_t ssl_prev;
};

struct grub_nilfs2_cpfile_header
{
  grub_uint64_t ch_ncheckpoints;
  grub_uint64_t ch_nsnapshots;
  struct grub_nilfs2_snapshot_list ch_snapshot_list;
};

struct grub_nilfs2_checkpoint
{
  grub_uint32_t cp_flags;
  grub_uint32_t cp_checkpoints_count;
  struct grub_nilfs2_snapshot_list cp_snapshot_list;
  grub_uint64_t cp_cno;
  grub_uint64_t cp_create;
  grub_uint64_t cp_nblk_inc;
  grub_uint64_t cp_inodes_count;
  grub_uint64_t cp_blocks_count;
  struct grub_nilfs2_inode cp_ifile_inode;
};


#define NILFS_BMAP_LARGE	0x1
#define NILFS_BMAP_SIZE	(NILFS_INODE_BMAP_SIZE * sizeof(grub_uint64_t))

/* nilfs extra padding for nonroot btree node. */
#define NILFS_BTREE_NODE_EXTRA_PAD_SIZE (sizeof(grub_uint64_t))
#define NILFS_BTREE_ROOT_SIZE	NILFS_BMAP_SIZE
#define NILFS_BTREE_ROOT_NCHILDREN_MAX \
 ((NILFS_BTREE_ROOT_SIZE - sizeof(struct nilfs_btree_node)) / \
  (sizeof(grub_uint64_t) + sizeof(grub_uint64_t)) )


struct grub_fshelp_node
{
  struct grub_nilfs2_data *data;
  struct grub_nilfs2_inode inode;
  grub_uint64_t ino;
  int inode_read;
};

struct grub_nilfs2_data
{
  struct grub_nilfs2_super_block sblock;
  struct grub_nilfs2_super_root sroot;
  struct grub_nilfs2_inode ifile;
  grub_disk_t disk;
  struct grub_nilfs2_inode *inode;
  struct grub_fshelp_node diropen;
};

/* Log2 size of nilfs2 block in 512 blocks.  */
#define LOG2_NILFS2_BLOCK_SIZE(data)			\
	(grub_le_to_cpu32 (data->sblock.s_log_block_size) + 1)

/* Log2 size of nilfs2 block in bytes.  */
#define LOG2_BLOCK_SIZE(data)					\
	(grub_le_to_cpu32 (data->sblock.s_log_block_size) + 10)

/* The size of an nilfs2 block in bytes.  */
#define NILFS2_BLOCK_SIZE(data)		(1 << LOG2_BLOCK_SIZE (data))

static grub_uint64_t
grub_nilfs2_dat_translate (struct grub_nilfs2_data *data, grub_uint64_t key);

static inline unsigned long
grub_nilfs2_palloc_entries_per_group (struct grub_nilfs2_data *data)
{
  return 1UL << (LOG2_BLOCK_SIZE (data) + 3);
}

static inline grub_uint64_t
grub_nilfs2_palloc_group (struct grub_nilfs2_data *data,
			  grub_uint64_t nr, grub_uint32_t * offset)
{
  return grub_divmod64 (nr, grub_nilfs2_palloc_entries_per_group (data),
			offset);
}

static inline grub_uint32_t
grub_nilfs2_palloc_groups_per_desc_block (struct grub_nilfs2_data *data)
{
  return NILFS2_BLOCK_SIZE (data) /
    sizeof (struct grub_nilfs2_palloc_group_desc);
}

static inline grub_uint32_t
grub_nilfs2_entries_per_block (struct grub_nilfs2_data *data,
			       unsigned long entry_size)
{
  return NILFS2_BLOCK_SIZE (data) / entry_size;
}


static inline grub_uint32_t
grub_nilfs2_blocks_per_group (struct grub_nilfs2_data *data,
			      unsigned long entry_size)
{
  return grub_div_roundup (grub_nilfs2_palloc_entries_per_group (data),
			   grub_nilfs2_entries_per_block (data,
							  entry_size)) + 1;
}

static inline grub_uint32_t
grub_nilfs2_blocks_per_desc_block (struct grub_nilfs2_data *data,
				   unsigned long entry_size)
{
  return grub_nilfs2_palloc_groups_per_desc_block (data) *
    grub_nilfs2_blocks_per_group (data, entry_size) + 1;
}

static inline grub_uint32_t
grub_nilfs2_palloc_desc_block_offset (struct grub_nilfs2_data *data,
				      unsigned long group,
				      unsigned long entry_size)
{
  grub_uint32_t desc_block =
    group / grub_nilfs2_palloc_groups_per_desc_block (data);
  return desc_block * grub_nilfs2_blocks_per_desc_block (data, entry_size);
}

static inline grub_uint32_t
grub_nilfs2_palloc_bitmap_block_offset (struct grub_nilfs2_data *data,
					unsigned long group,
					unsigned long entry_size)
{
  unsigned long desc_offset = group %
    grub_nilfs2_palloc_groups_per_desc_block (data);

  return grub_nilfs2_palloc_desc_block_offset (data, group, entry_size) + 1 +
    desc_offset * grub_nilfs2_blocks_per_group (data, entry_size);
}

static inline grub_uint32_t
grub_nilfs2_palloc_entry_offset (struct grub_nilfs2_data *data,
				 grub_uint64_t nr, unsigned long entry_size)
{
  unsigned long group;
  grub_uint32_t group_offset;

  group = grub_nilfs2_palloc_group (data, nr, &group_offset);

  return grub_nilfs2_palloc_bitmap_block_offset (data, group,
						 entry_size) + 1 +
    group_offset / grub_nilfs2_entries_per_block (data, entry_size);

}

static inline struct grub_nilfs2_btree_node *
grub_nilfs2_btree_get_root (struct grub_nilfs2_inode *inode)
{
  return (struct grub_nilfs2_btree_node *) &inode->i_bmap[0];
}

static inline int
grub_nilfs2_btree_get_level (struct grub_nilfs2_btree_node *node)
{
  return node->bn_level;
}

static inline grub_uint64_t *
grub_nilfs2_btree_node_dkeys (struct grub_nilfs2_btree_node *node)
{
  return (grub_uint64_t *) ((char *) (node + 1) +
			    ((node->bn_flags & NILFS_BTREE_NODE_ROOT) ?
			     0 : NILFS_BTREE_NODE_EXTRA_PAD_SIZE));
}

static inline grub_uint64_t
grub_nilfs2_btree_node_get_key (struct grub_nilfs2_btree_node *node,
				int index)
{
  return grub_le_to_cpu64 (*(grub_nilfs2_btree_node_dkeys (node) + index));
}

static inline int
grub_nilfs2_btree_node_lookup (struct grub_nilfs2_btree_node *node,
			       grub_uint64_t key, int *indexp)
{
  grub_uint64_t nkey;
  int index, low, high, s;

  low = 0;
  high = grub_le_to_cpu16 (node->bn_nchildren) - 1;
  index = 0;
  s = 0;
  while (low <= high)
    {
      index = (low + high) / 2;
      nkey = grub_nilfs2_btree_node_get_key (node, index);
      if (nkey == key)
	{
	  *indexp = index;
	  return 1;
	}
      else if (nkey < key)
	{
	  low = index + 1;
	  s = -1;
	}
      else
	{
	  high = index - 1;
	  s = 1;
	}
    }

  if (node->bn_level > NILFS_BTREE_LEVEL_NODE_MIN)
    {
      if (s > 0 && index > 0)
	index--;
    }
  else if (s < 0)
    index++;

  *indexp = index;
  return s == 0;
}

static inline int
grub_nilfs2_btree_node_nchildren_max (struct grub_nilfs2_data *data,
				      struct grub_nilfs2_btree_node *node)
{
  int node_children_max = ((NILFS2_BLOCK_SIZE (data) -
			    sizeof (struct grub_nilfs2_btree_node) -
			    NILFS_BTREE_NODE_EXTRA_PAD_SIZE) /
			   (sizeof (grub_uint64_t) + sizeof (grub_uint64_t)));

  return (node->bn_flags & NILFS_BTREE_NODE_ROOT) ? 3 : node_children_max;
}

static inline grub_uint64_t *
grub_nilfs2_btree_node_dptrs (struct grub_nilfs2_data *data,
			      struct grub_nilfs2_btree_node *node)
{
  return (grub_uint64_t *) (grub_nilfs2_btree_node_dkeys (node) +
			    grub_nilfs2_btree_node_nchildren_max (data,
								  node));
}

static inline grub_uint64_t
grub_nilfs2_btree_node_get_ptr (struct grub_nilfs2_data *data,
				struct grub_nilfs2_btree_node *node,
				int index)
{
  return
    grub_le_to_cpu64 (*(grub_nilfs2_btree_node_dptrs (data, node) + index));
}

static inline int
grub_nilfs2_btree_get_nonroot_node (struct grub_nilfs2_data *data,
				    grub_uint64_t ptr, void *block)
{
  grub_disk_t disk = data->disk;
  unsigned int nilfs2_block_count = (1 << LOG2_NILFS2_BLOCK_SIZE (data));

  return grub_disk_read (disk, ptr * nilfs2_block_count, 0,
			 NILFS2_BLOCK_SIZE (data), block);
}

static grub_uint64_t
grub_nilfs2_btree_lookup (struct grub_nilfs2_data *data,
			  struct grub_nilfs2_inode *inode,
			  grub_uint64_t key, int need_translate)
{
  struct grub_nilfs2_btree_node *node;
#ifndef _MSC_VER
  unsigned char block[NILFS2_BLOCK_SIZE (data)];
#else
  unsigned char * block = grub_malloc(NILFS2_BLOCK_SIZE (data));
#endif
  grub_uint64_t ptr;
  int level, found, index;

  node = grub_nilfs2_btree_get_root (inode);
  level = grub_nilfs2_btree_get_level (node);

  found = grub_nilfs2_btree_node_lookup (node, key, &index);
  ptr = grub_nilfs2_btree_node_get_ptr (data, node, index);
  if (need_translate)
    ptr = grub_nilfs2_dat_translate (data, ptr);

  for (level--; level >= NILFS_BTREE_LEVEL_NODE_MIN; level--)
    {
      grub_nilfs2_btree_get_nonroot_node (data, ptr, block);
      if (grub_errno)
	{
	  return -1;
	}
      node = (struct grub_nilfs2_btree_node *) block;

      if (node->bn_level != level)
	{
	  grub_error (GRUB_ERR_BAD_FS, "btree level mismatch\n");
	  return -1;
	}

      if (!found)
	found = grub_nilfs2_btree_node_lookup (node, key, &index);
      else
	index = 0;

      if (index < grub_nilfs2_btree_node_nchildren_max (data, node))
	{
	  ptr = grub_nilfs2_btree_node_get_ptr (data, node, index);
	  if (need_translate)
	    ptr = grub_nilfs2_dat_translate (data, ptr);
	}
      else
	{
	  grub_error (GRUB_ERR_BAD_FS, "btree corruption\n");
	  return -1;
	}
    }

  if (!found)
    return -1;

  return ptr;
}

static inline grub_uint64_t
grub_nilfs2_direct_lookup (struct grub_nilfs2_inode *inode, grub_uint64_t key)
{
  return grub_le_to_cpu64 (inode->i_bmap[1 + key]);
}

static inline grub_uint64_t
grub_nilfs2_bmap_lookup (struct grub_nilfs2_data *data,
			 struct grub_nilfs2_inode *inode,
			 grub_uint64_t key, int need_translate)
{
  struct grub_nilfs2_btree_node *root = grub_nilfs2_btree_get_root (inode);
  if (root->bn_flags & NILFS_BMAP_LARGE)
    return grub_nilfs2_btree_lookup (data, inode, key, need_translate);
  else
    {
      grub_uint64_t ptr;
      ptr = grub_nilfs2_direct_lookup (inode, key);
      if (need_translate)
	ptr = grub_nilfs2_dat_translate (data, ptr);
      return ptr;
    }
}

static grub_uint64_t
grub_nilfs2_dat_translate (struct grub_nilfs2_data *data, grub_uint64_t key)
{
  struct grub_nilfs2_dat_entry entry;
  grub_disk_t disk = data->disk;
  grub_uint64_t pptr;
  grub_uint32_t blockno, offset;
  unsigned int nilfs2_block_count = (1 << LOG2_NILFS2_BLOCK_SIZE (data));

  blockno = grub_nilfs2_palloc_entry_offset (data, key,
					     sizeof (struct
						     grub_nilfs2_dat_entry));

  grub_divmod64 (key * sizeof (struct grub_nilfs2_dat_entry),
		 NILFS2_BLOCK_SIZE (data), &offset);

  pptr = grub_nilfs2_bmap_lookup (data, &data->sroot.sr_dat, blockno, 0);
  if (pptr == (grub_uint64_t) - 1)
    {
      grub_error (GRUB_ERR_BAD_FS, "btree lookup failure");
      return -1;
    }

  grub_disk_read (disk, pptr * nilfs2_block_count, offset,
		  sizeof (struct grub_nilfs2_dat_entry), &entry);

  return grub_le_to_cpu64 (entry.de_blocknr);
}


static grub_disk_addr_t
grub_nilfs2_read_block (grub_fshelp_node_t node, grub_disk_addr_t fileblock)
{
  struct grub_nilfs2_data *data = node->data;
  struct grub_nilfs2_inode *inode = &node->inode;
  grub_uint64_t pptr = -1;

  pptr = grub_nilfs2_bmap_lookup (data, inode, fileblock, 1);
  if (pptr == (grub_uint64_t) - 1)
    {
      grub_error (GRUB_ERR_BAD_FS, "btree lookup failure");
      return -1;
    }

  return pptr;
}

/* Read LEN bytes from the file described by DATA starting with byte
   POS.  Return the amount of read bytes in READ.  */
static grub_ssize_t
grub_nilfs2_read_file (grub_fshelp_node_t node,
		       void (*read_hook) (grub_disk_addr_t
					  sector,
					  unsigned offset,
					  unsigned length,
					  void *closure),
		       void *closure, int flags,
		       int pos, grub_size_t len, char *buf)
{
  return grub_fshelp_read_file (node->data->disk, node, read_hook, closure,
				flags, pos, len, buf, grub_nilfs2_read_block,
				grub_le_to_cpu64 (node->inode.i_size),
				LOG2_NILFS2_BLOCK_SIZE (node->data));

}

static grub_err_t
grub_nilfs2_read_checkpoint (struct grub_nilfs2_data *data,
			     grub_uint64_t cpno,
			     struct grub_nilfs2_checkpoint *cpp)
{
  grub_uint64_t blockno;
  grub_uint32_t offset;
  grub_uint64_t pptr;
  grub_disk_t disk = data->disk;
  unsigned int nilfs2_block_count = (1 << LOG2_NILFS2_BLOCK_SIZE (data));

  /* Assume sizeof(struct grub_nilfs2_cpfile_header) <
     sizeof(struct grub_nilfs2_checkpoint).
   */
  blockno = grub_divmod64 (cpno, NILFS2_BLOCK_SIZE (data) /
			   sizeof (struct grub_nilfs2_checkpoint), &offset);

  pptr = grub_nilfs2_bmap_lookup (data, &data->sroot.sr_cpfile, blockno, 1);
  if (pptr == (grub_uint64_t) - 1)
    {
      return grub_error (GRUB_ERR_BAD_FS, "btree lookup failure");
    }

  return grub_disk_read (disk, pptr * nilfs2_block_count,
			 offset * sizeof (struct grub_nilfs2_checkpoint),
			 sizeof (struct grub_nilfs2_checkpoint), cpp);
}

static inline grub_err_t
grub_nilfs2_read_last_checkpoint (struct grub_nilfs2_data *data,
				  struct grub_nilfs2_checkpoint *cpp)
{
  return grub_nilfs2_read_checkpoint (data,
				      grub_le_to_cpu64 (data->
							sblock.s_last_cno),
				      cpp);
}

/* Read the inode INO for the file described by DATA into INODE.  */
static grub_err_t
grub_nilfs2_read_inode (struct grub_nilfs2_data *data,
			grub_uint64_t ino, struct grub_nilfs2_inode *inodep)
{
  grub_uint64_t blockno;
  unsigned int offset;
  grub_uint64_t pptr;
  grub_disk_t disk = data->disk;
  unsigned int nilfs2_block_count = (1 << LOG2_NILFS2_BLOCK_SIZE (data));

  blockno = grub_nilfs2_palloc_entry_offset (data, ino,
					     sizeof (struct
						     grub_nilfs2_inode));

  grub_divmod64 (sizeof (struct grub_nilfs2_inode) * ino,
		 NILFS2_BLOCK_SIZE (data), &offset);
  pptr = grub_nilfs2_bmap_lookup (data, &data->ifile, blockno, 1);
  if (pptr == (grub_uint64_t) - 1)
    {
      return grub_error (GRUB_ERR_BAD_FS, "btree lookup failure");
    }

  return grub_disk_read (disk, pptr * nilfs2_block_count, offset,
			 sizeof (struct grub_nilfs2_inode), inodep);
}

static int
grub_nilfs2_valid_sb (struct grub_nilfs2_super_block *sbp)
{
  if (grub_le_to_cpu16 (sbp->s_magic) != NILFS2_SUPER_MAGIC)
    return 0;

  if (grub_le_to_cpu32 (sbp->s_rev_level) != NILFS_SUPORT_REV)
    return 0;

  return 1;
}

static struct grub_nilfs2_data *
grub_nilfs2_mount (grub_disk_t disk)
{
  struct grub_nilfs2_data *data;
  struct grub_nilfs2_segment_summary ss;
  struct grub_nilfs2_checkpoint last_checkpoint;
  grub_uint64_t last_pseg;
  grub_uint32_t nblocks;
  unsigned int nilfs2_block_count;

  data = grub_malloc (sizeof (struct grub_nilfs2_data));
  if (!data)
    return 0;

  /* Read the superblock.  */
  grub_disk_read (disk, 1 * 2, 0, sizeof (struct grub_nilfs2_super_block),
		  &data->sblock);
  if (grub_errno)
    goto fail;

  /* Make sure this is an nilfs2 filesystem.  */
  if (!grub_nilfs2_valid_sb (&data->sblock))
    {
      grub_error (GRUB_ERR_BAD_FS, "not a nilfs2 filesystem");
      goto fail;
    }

  nilfs2_block_count = (1 << LOG2_NILFS2_BLOCK_SIZE (data));

  /* Read the last segment summary. */
  last_pseg = grub_le_to_cpu64 (data->sblock.s_last_pseg);
  grub_disk_read (disk, last_pseg * nilfs2_block_count, 0,
		  sizeof (struct grub_nilfs2_segment_summary), &ss);

  if (grub_errno)
    goto fail;

  /* Read the super root block. */
  nblocks = grub_le_to_cpu32 (ss.ss_nblocks);
  grub_disk_read (disk, (last_pseg + (nblocks - 1)) * nilfs2_block_count, 0,
		  sizeof (struct grub_nilfs2_super_root), &data->sroot);

  if (grub_errno)
    goto fail;

  data->disk = disk;

  grub_nilfs2_read_last_checkpoint (data, &last_checkpoint);

  if (grub_errno)
    goto fail;

  grub_memcpy (&data->ifile, &last_checkpoint.cp_ifile_inode,
	       sizeof (struct grub_nilfs2_inode));

  data->diropen.data = data;
  data->diropen.ino = 2;
  data->diropen.inode_read = 1;
  data->inode = &data->diropen.inode;

  grub_nilfs2_read_inode (data, 2, data->inode);

  return data;

fail:
  if (grub_errno == GRUB_ERR_OUT_OF_RANGE)
    grub_error (GRUB_ERR_BAD_FS, "not a nilfs2 filesystem");

  grub_free (data);
  return 0;
}

static char *
grub_nilfs2_read_symlink (grub_fshelp_node_t node)
{
  char *symlink;
  struct grub_fshelp_node *diro = node;

  if (!diro->inode_read)
    {
      grub_nilfs2_read_inode (diro->data, diro->ino, &diro->inode);
      if (grub_errno)
	return 0;
    }

  symlink = grub_malloc (grub_le_to_cpu64 (diro->inode.i_size) + 1);
  if (!symlink)
    return 0;

  grub_nilfs2_read_file (diro, 0, 0, 0, 0,
			 grub_le_to_cpu64 (diro->inode.i_size), symlink);
  if (grub_errno)
    {
      grub_free (symlink);
      return 0;
    }

  symlink[grub_le_to_cpu64 (diro->inode.i_size)] = '\0';
  return symlink;
}

static int
grub_nilfs2_iterate_dir (grub_fshelp_node_t dir,
			 int (*hook) (const char *filename,
				      enum grub_fshelp_filetype filetype,
				      grub_fshelp_node_t node,
				      void *closure),
			 void *closure)
{
  unsigned int fpos = 0;
  struct grub_fshelp_node *diro = (struct grub_fshelp_node *) dir;

  if (!diro->inode_read)
    {
      grub_nilfs2_read_inode (diro->data, diro->ino, &diro->inode);
      if (grub_errno)
	return 0;
    }

  /* Iterate files.  */
  if (hook)
  while (fpos < grub_le_to_cpu64 (diro->inode.i_size))
    {
      struct grub_nilfs2_dir_entry dirent;

      grub_nilfs2_read_file (diro, 0, 0, 0, fpos,
			     sizeof (struct grub_nilfs2_dir_entry),
			     (char *) &dirent);
      if (grub_errno)
	return 0;

      if (dirent.rec_len == 0)
	return 0;

      if (dirent.name_len != 0)
	{
#ifndef _MSC_VER
	  char filename[dirent.name_len + 1];
#else
	  char * filename = grub_malloc(dirent.name_len + 1);
#endif
	  struct grub_fshelp_node *fdiro;
	  enum grub_fshelp_filetype type = GRUB_FSHELP_UNKNOWN;

	  grub_nilfs2_read_file (diro, 0, 0, 0,
				 fpos + sizeof (struct grub_nilfs2_dir_entry),
				 dirent.name_len, filename);
	  if (grub_errno)
	    return 0;

	  fdiro = grub_malloc (sizeof (struct grub_fshelp_node));
	  if (!fdiro)
	    return 0;

	  fdiro->data = diro->data;
	  fdiro->ino = grub_le_to_cpu64 (dirent.inode);

	  filename[dirent.name_len] = '\0';

	  if (dirent.file_type != NILFS_FT_UNKNOWN)
	    {
	      fdiro->inode_read = 0;

	      if (dirent.file_type == NILFS_FT_DIR)
		type = GRUB_FSHELP_DIR;
	      else if (dirent.file_type == NILFS_FT_SYMLINK)
		type = GRUB_FSHELP_SYMLINK;
	      else if (dirent.file_type == NILFS_FT_REG_FILE)
		type = GRUB_FSHELP_REG;
	    }
	  else
	    {
	      /* The filetype can not be read from the dirent, read
	         the inode to get more information.  */
	      grub_nilfs2_read_inode (diro->data,
				      grub_le_to_cpu64 (dirent.inode),
				      &fdiro->inode);
	      if (grub_errno)
		{
		  grub_free (fdiro);
		  return 0;
		}

	      fdiro->inode_read = 1;

	      if ((grub_le_to_cpu16 (fdiro->inode.i_mode)
		   & FILETYPE_INO_MASK) == FILETYPE_INO_DIRECTORY)
		type = GRUB_FSHELP_DIR;
	      else if ((grub_le_to_cpu16 (fdiro->inode.i_mode)
			& FILETYPE_INO_MASK) == FILETYPE_INO_SYMLINK)
		type = GRUB_FSHELP_SYMLINK;
	      else if ((grub_le_to_cpu16 (fdiro->inode.i_mode)
			& FILETYPE_INO_MASK) == FILETYPE_INO_REG)
		type = GRUB_FSHELP_REG;
	    }

	  if (hook (filename, type, fdiro, closure))
	    return 1;
	}

      fpos += grub_le_to_cpu16 (dirent.rec_len);
    }

  return 0;
}

/* Open a file named NAME and initialize FILE.  */
static grub_err_t
grub_nilfs2_open (struct grub_file *file, const char *name)
{
  struct grub_nilfs2_data *data = NULL;
  struct grub_fshelp_node *fdiro = 0;

  data = grub_nilfs2_mount (file->device->disk);
  if (!data)
    goto fail;

  grub_fshelp_find_file (name, &data->diropen, &fdiro,
			 grub_nilfs2_iterate_dir, 0, grub_nilfs2_read_symlink,
			 GRUB_FSHELP_REG);
  if (grub_errno)
    goto fail;

  if (!fdiro->inode_read)
    {
      grub_nilfs2_read_inode (data, fdiro->ino, &fdiro->inode);
      if (grub_errno)
	goto fail;
    }

  grub_memcpy (data->inode, &fdiro->inode, sizeof (struct grub_nilfs2_inode));
  grub_free (fdiro);

  file->size = grub_le_to_cpu64 (data->inode->i_size);
  file->data = data;
  file->offset = 0;

  return 0;

fail:
  if (fdiro != &data->diropen)
    grub_free (fdiro);
  grub_free (data);

  return grub_errno;
}

static grub_err_t
grub_nilfs2_close (grub_file_t file)
{
  grub_free (file->data);

  return GRUB_ERR_NONE;
}

/* Read LEN bytes data from FILE into BUF.  */
static grub_ssize_t
grub_nilfs2_read (grub_file_t file, char *buf, grub_size_t len)
{
  struct grub_nilfs2_data *data = (struct grub_nilfs2_data *) file->data;

  return grub_nilfs2_read_file (&data->diropen, file->read_hook, file->closure,
				file->flags, file->offset, len, buf);
}

struct grub_nilfs2_dir_closure
{
  int (*hook) (const char *filename,
	       const struct grub_dirhook_info *info,
	       void *closure);
  void *closure;
  struct grub_nilfs2_data *data;
};

static int
iterate (const char *filename,
	 enum grub_fshelp_filetype filetype,
	 grub_fshelp_node_t node,
	 void *closure)
{
  struct grub_nilfs2_dir_closure *c = closure;
  struct grub_dirhook_info info;
  grub_memset (&info, 0, sizeof (info));
  if (!node->inode_read)
    {
      grub_nilfs2_read_inode (c->data, node->ino, &node->inode);
      if (!grub_errno)
	node->inode_read = 1;
      grub_errno = GRUB_ERR_NONE;
    }
  if (node->inode_read)
    {
      info.mtimeset = 1;
      info.mtime = grub_le_to_cpu64 (node->inode.i_mtime);
    }

  info.dir = ((filetype & GRUB_FSHELP_TYPE_MASK) == GRUB_FSHELP_DIR);
  grub_free (node);
  return c->hook (filename, &info, c->closure);
}

static grub_err_t
grub_nilfs2_dir (grub_device_t device, const char *path,
		 int (*hook) (const char *filename,
			      const struct grub_dirhook_info * info,
			      void *closure),
		 void *closure)
{
  struct grub_nilfs2_data *data = 0;
  struct grub_fshelp_node *fdiro = 0;
  struct grub_nilfs2_dir_closure c;

  data = grub_nilfs2_mount (device->disk);
  if (!data)
    goto fail;

  grub_fshelp_find_file (path, &data->diropen, &fdiro,
			 grub_nilfs2_iterate_dir, 0, grub_nilfs2_read_symlink,
			 GRUB_FSHELP_DIR);
  if (grub_errno)
    goto fail;

  c.hook = hook;
  c.closure = closure;
  c.data = data;
  grub_nilfs2_iterate_dir (fdiro, iterate, &c);

fail:
  if (fdiro != &data->diropen)
    grub_free (fdiro);
  grub_free (data);

  return grub_errno;
}

static grub_err_t
grub_nilfs2_label (grub_device_t device, char **label)
{
  struct grub_nilfs2_data *data;
  grub_disk_t disk = device->disk;

  data = grub_nilfs2_mount (disk);
  if (data)
    *label = grub_strndup (data->sblock.s_volume_name, 14);
  else
    *label = NULL;

  grub_free (data);

  return grub_errno;
}

static grub_err_t
grub_nilfs2_uuid (grub_device_t device, char **uuid)
{
  struct grub_nilfs2_data *data;
  grub_disk_t disk = device->disk;

  data = grub_nilfs2_mount (disk);
  if (data)
    {
      *uuid =
	grub_xasprintf
	("%02x%02x%02x%02x-%02x%02x-%02x%02x-%02x%0x-%02x%02x%02x%02x%02x%02x",
	 data->sblock.s_uuid[0], data->sblock.s_uuid[1],
	 data->sblock.s_uuid[2], data->sblock.s_uuid[3],
	 data->sblock.s_uuid[4], data->sblock.s_uuid[5],
	 data->sblock.s_uuid[6], data->sblock.s_uuid[7],
	 data->sblock.s_uuid[8], data->sblock.s_uuid[9],
	 data->sblock.s_uuid[10], data->sblock.s_uuid[11],
	 data->sblock.s_uuid[12], data->sblock.s_uuid[13],
	 data->sblock.s_uuid[14], data->sblock.s_uuid[15]);
    }
  else
    *uuid = NULL;

  grub_free (data);

  return grub_errno;
}

/* Get mtime.  */
static grub_err_t
grub_nilfs2_mtime (grub_device_t device, grub_int32_t * tm)
{
  struct grub_nilfs2_data *data;
  grub_disk_t disk = device->disk;

  data = grub_nilfs2_mount (disk);
  if (!data)
    *tm = 0;
  else
    *tm = (grub_int32_t) grub_le_to_cpu64 (data->sblock.s_mtime);

  grub_free (data);

  return grub_errno;
}


struct grub_fs grub_nilfs2_fs = {
  .name = "nilfs2",
  .dir = grub_nilfs2_dir,
  .open = grub_nilfs2_open,
  .read = grub_nilfs2_read,
  .close = grub_nilfs2_close,
  .label = grub_nilfs2_label,
  .uuid = grub_nilfs2_uuid,
  .mtime = grub_nilfs2_mtime,
#ifdef GRUB_UTIL
  .reserved_first_sector = 1,
#endif
  .next = 0
};
