/*
   * Squashfs - a compressed read only filesystem for Linux
   *
   * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008

   * Phillip Lougher <phillip@squashfs.org.uk>

   *
   * 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,
   * 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, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
   *
   * export.c
   */
  
  /*
   * This file implements code to make Squashfs filesystems exportable (NFS etc.)
   *
   * The export code uses an inode lookup table to map inode numbers passed in
   * filehandles to an inode location on disk.  This table is stored compressed
   * into metadata blocks.  A second index table is used to locate these.  This
   * second index table for speed of access (and because it is small) is read at
   * mount time and cached in memory.
   *
   * The inode lookup table is used only by the export code, inode disk
   * locations are directly encoded in directories, enabling direct access
   * without an intermediate lookup for all operations except the export ops.
   */
  
  #include <linux/fs.h>
  #include <linux/vfs.h>
  #include <linux/dcache.h>
  #include <linux/exportfs.h>

  #include <linux/slab.h>

  
  #include "squashfs_fs.h"
  #include "squashfs_fs_sb.h"
  #include "squashfs_fs_i.h"
  #include "squashfs.h"
  
  /*
   * Look-up inode number (ino) in table, returning the inode location.
   */
  static long long squashfs_inode_lookup(struct super_block *sb, int ino_num)
  {
  	struct squashfs_sb_info *msblk = sb->s_fs_info;
  	int blk = SQUASHFS_LOOKUP_BLOCK(ino_num - 1);
  	int offset = SQUASHFS_LOOKUP_BLOCK_OFFSET(ino_num - 1);
  	u64 start = le64_to_cpu(msblk->inode_lookup_table[blk]);
  	__le64 ino;
  	int err;
  
  	TRACE("Entered squashfs_inode_lookup, inode_number = %d
  ", ino_num);
  
  	err = squashfs_read_metadata(sb, &ino, &start, &offset, sizeof(ino));
  	if (err < 0)
  		return err;
  
  	TRACE("squashfs_inode_lookup, inode = 0x%llx
  ",
  		(u64) le64_to_cpu(ino));
  
  	return le64_to_cpu(ino);
  }
  
  
  static struct dentry *squashfs_export_iget(struct super_block *sb,
  	unsigned int ino_num)
  {
  	long long ino;
  	struct dentry *dentry = ERR_PTR(-ENOENT);
  
  	TRACE("Entered squashfs_export_iget
  ");
  
  	ino = squashfs_inode_lookup(sb, ino_num);
  	if (ino >= 0)
  		dentry = d_obtain_alias(squashfs_iget(sb, ino, ino_num));
  
  	return dentry;
  }
  
  
  static struct dentry *squashfs_fh_to_dentry(struct super_block *sb,
  		struct fid *fid, int fh_len, int fh_type)
  {
  	if ((fh_type != FILEID_INO32_GEN && fh_type != FILEID_INO32_GEN_PARENT)
  			|| fh_len < 2)
  		return NULL;
  
  	return squashfs_export_iget(sb, fid->i32.ino);
  }
  
  
  static struct dentry *squashfs_fh_to_parent(struct super_block *sb,
  		struct fid *fid, int fh_len, int fh_type)
  {
  	if (fh_type != FILEID_INO32_GEN_PARENT || fh_len < 4)
  		return NULL;
  
  	return squashfs_export_iget(sb, fid->i32.parent_ino);
  }
  
  
  static struct dentry *squashfs_get_parent(struct dentry *child)
  {

  	struct inode *inode = d_inode(child);

  	unsigned int parent_ino = squashfs_i(inode)->parent;
  
  	return squashfs_export_iget(inode->i_sb, parent_ino);
  }
  
  
  /*
   * Read uncompressed inode lookup table indexes off disk into memory
   */
  __le64 *squashfs_read_inode_lookup_table(struct super_block *sb,

  		u64 lookup_table_start, u64 next_table, unsigned int inodes)

  {
  	unsigned int length = SQUASHFS_LOOKUP_BLOCK_BYTES(inodes);

  	__le64 *table;

  
  	TRACE("In read_inode_lookup_table, length %d
  ", length);

  	/* Sanity check values */
  
  	/* there should always be at least one inode */
  	if (inodes == 0)
  		return ERR_PTR(-EINVAL);
  
  	/* length bytes should not extend into the next table - this check
  	 * also traps instances where lookup_table_start is incorrectly larger
  	 * than the next table start
  	 */
  	if (lookup_table_start + length > next_table)
  		return ERR_PTR(-EINVAL);
  
  	table = squashfs_read_table(sb, lookup_table_start, length);
  
  	/*
  	 * table[0] points to the first inode lookup table metadata block,
  	 * this should be less than lookup_table_start
  	 */

  	if (!IS_ERR(table) && le64_to_cpu(table[0]) >= lookup_table_start) {

  		kfree(table);
  		return ERR_PTR(-EINVAL);
  	}
  
  	return table;

  }
  
  
  const struct export_operations squashfs_export_ops = {
  	.fh_to_dentry = squashfs_fh_to_dentry,
  	.fh_to_parent = squashfs_fh_to_parent,
  	.get_parent = squashfs_get_parent
  };