/*
   *  linux/fs/ext2/xip.c
   *
   * Copyright (C) 2005 IBM Corporation
   * Author: Carsten Otte (cotte@de.ibm.com)
   */
  
  #include <linux/mm.h>
  #include <linux/fs.h>
  #include <linux/genhd.h>
  #include <linux/buffer_head.h>
  #include <linux/ext2_fs_sb.h>
  #include <linux/ext2_fs.h>

  #include <linux/blkdev.h>

  #include "ext2.h"
  #include "xip.h"
  
  static inline int

  __inode_direct_access(struct inode *inode, sector_t block,

  		      void **kaddr, unsigned long *pfn)

  {

  	struct block_device *bdev = inode->i_sb->s_bdev;

  	const struct block_device_operations *ops = bdev->bd_disk->fops;

  	sector_t sector;
  
  	sector = block * (PAGE_SIZE / 512); /* ext2 block to bdev sector */

  
  	BUG_ON(!ops->direct_access);
  	return ops->direct_access(bdev, sector, kaddr, pfn);

  }

  static inline int

  __ext2_get_block(struct inode *inode, pgoff_t pgoff, int create,

  		   sector_t *result)
  {
  	struct buffer_head tmp;
  	int rc;
  
  	memset(&tmp, 0, sizeof(struct buffer_head));

  	rc = ext2_get_block(inode, pgoff, &tmp, create);

  	*result = tmp.b_blocknr;
  
  	/* did we get a sparse block (hole in the file)? */

  	if (!tmp.b_blocknr && !rc) {

  		BUG_ON(create);
  		rc = -ENODATA;
  	}
  
  	return rc;
  }

  int

  ext2_clear_xip_target(struct inode *inode, sector_t block)

  {

  	void *kaddr;
  	unsigned long pfn;

  	int rc;

  	rc = __inode_direct_access(inode, block, &kaddr, &pfn);

  	if (!rc)

  		clear_page(kaddr);

  	return rc;

  }
  
  void ext2_xip_verify_sb(struct super_block *sb)
  {
  	struct ext2_sb_info *sbi = EXT2_SB(sb);

  	if ((sbi->s_mount_opt & EXT2_MOUNT_XIP) &&
  	    !sb->s_bdev->bd_disk->fops->direct_access) {
  		sbi->s_mount_opt &= (~EXT2_MOUNT_XIP);

  		ext2_msg(sb, KERN_WARNING,
  			     "warning: ignoring xip option - "
  			     "not supported by bdev");

  	}
  }

  int ext2_get_xip_mem(struct address_space *mapping, pgoff_t pgoff, int create,
  				void **kmem, unsigned long *pfn)

  {
  	int rc;

  	sector_t block;

  	/* first, retrieve the sector number */

  	rc = __ext2_get_block(mapping->host, pgoff, create, &block);

  	if (rc)

  		return rc;

  	/* retrieve address of the target data */

  	rc = __inode_direct_access(mapping->host, block, kmem, pfn);
  	return rc;

  }