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dm-linear.c

/*
 * Copyright (C) 2001-2003 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>

#define DM_MSG_PREFIX "linear"

/*
 * 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;
      unsigned long long tmp;

      if (argc != 2) {
            ti->error = "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], "%llu", &tmp) != 1) {
            ti->error = "dm-linear: Invalid device sector";
            goto bad;
      }
      lc->start = tmp;

      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,
                  union map_info *map_context)
{
      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 DM_MAPIO_REMAPPED;
}

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;

      switch (type) {
      case STATUSTYPE_INFO:
            result[0] = '\0';
            break;

      case STATUSTYPE_TABLE:
            snprintf(result, maxlen, "%s %llu", lc->dev->name,
                        (unsigned long long)lc->start);
            break;
      }
      return 0;
}

static int linear_ioctl(struct dm_target *ti, struct inode *inode,
                  struct file *filp, unsigned int cmd,
                  unsigned long arg)
{
      struct linear_c *lc = (struct linear_c *) ti->private;
      struct block_device *bdev = lc->dev->bdev;
      struct file fake_file = {};
      struct dentry fake_dentry = {};

      fake_file.f_mode = lc->dev->mode;
      fake_file.f_path.dentry = &fake_dentry;
      fake_dentry.d_inode = bdev->bd_inode;

      return blkdev_driver_ioctl(bdev->bd_inode, &fake_file, bdev->bd_disk, cmd, arg);
}

static struct target_type linear_target = {
      .name   = "linear",
      .version= {1, 0, 2},
      .module = THIS_MODULE,
      .ctr    = linear_ctr,
      .dtr    = linear_dtr,
      .map    = linear_map,
      .status = linear_status,
      .ioctl  = linear_ioctl,
};

int __init dm_linear_init(void)
{
      int r = dm_register_target(&linear_target);

      if (r < 0)
            DMERR("register failed %d", r);

      return r;
}

void dm_linear_exit(void)
{
      int r = dm_unregister_target(&linear_target);

      if (r < 0)
            DMERR("unregister failed %d", r);
}

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