text: /*
   * Copyright (C) 2001 Sistina Software (UK) Limited.
   *
   * This file is released under the GPL.
   */
  
  #include "dm.h"
  
  #include <linux/module.h>
  #include <linux/init.h>
  #include <linux/blkdev.h>
  #include <linux/bio.h>
  #include <linux/slab.h>
  
  /*
   * Linear: maps a linear range of a device.
   */
  struct linear_c {
  	struct dm_dev *dev;
  	sector_t start;
  };
  
  /*
   * Construct a linear mapping: <dev_path> <offset>
   */
  static int linear_ctr(struct dm_target *ti, unsigned int argc, char **argv)
  {
  	struct linear_c *lc;
  
  	if (argc != 2) {
  		ti->error = "dm-linear: Invalid argument count";
  		return -EINVAL;
  	}
  
  	lc = kmalloc(sizeof(*lc), GFP_KERNEL);
  	if (lc == NULL) {
  		ti->error = "dm-linear: Cannot allocate linear context";
  		return -ENOMEM;
  	}
  
  	if (sscanf(argv[1], SECTOR_FORMAT, &lc->start) != 1) {
  		ti->error = "dm-linear: Invalid device sector";
  		goto bad;
  	}
  
  	if (dm_get_device(ti, argv[0], lc->start, ti->len,
  			  dm_table_get_mode(ti->table), &lc->dev)) {
  		ti->error = "dm-linear: Device lookup failed";
  		goto bad;
  	}
  
  	ti->private = lc;
  	return 0;
  
        bad:
  	kfree(lc);
  	return -EINVAL;
  }
  
  static void linear_dtr(struct dm_target *ti)
  {
  	struct linear_c *lc = (struct linear_c *) ti->private;
  
  	dm_put_device(ti, lc->dev);
  	kfree(lc);
  }
  
  static int linear_map(struct dm_target *ti, struct bio *bio)
  {
  	struct linear_c *lc = (struct linear_c *) ti->private;
  
  	bio->bi_bdev = lc->dev->bdev;
  	bio->bi_sector = lc->start + (bio->bi_sector - ti->begin);
  
  	return 1;
  }
  
  static int linear_status(struct dm_target *ti, status_type_t type,
  			 char *result, unsigned int maxlen)
  {
  	struct linear_c *lc = (struct linear_c *) ti->private;
  	char buffer[32];
  
  	switch (type) {
  	case STATUSTYPE_INFO:
  		result[0] = '\0';
  		break;
  
  	case STATUSTYPE_TABLE:
  		format_dev_t(buffer, lc->dev->bdev->bd_dev);
  		snprintf(result, maxlen, "%s " SECTOR_FORMAT, buffer, lc->start);
  		break;
  	}
  	return 0;
  }
  
  static struct target_type linear_target = {
  	.name   = "linear",
  	.module = THIS_MODULE,
  	.ctr    = linear_ctr,
  	.dtr    = linear_dtr,
  	.map    = linear_map,
  	.status = linear_status,
  };
  
  int __init dm_linear_init(void)
  {
  	int r = dm_register_target(&linear_target);
  
  	if (r < 0)
  		DMERR("linear: register failed %d", r);
  
  	return r;
  }
  
  void dm_linear_exit(void)
  {
  	int r = dm_unregister_target(&linear_target);
  
  	if (r < 0)
  		DMERR("linear: unregister failed %d", r);
  }
  