dm-linear.c

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/*
 * 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>
#include <linux/device-mapper.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;
    char dummy;

    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%c", &tmp, &dummy) != 1) {
        ti->error = "dm-linear: Invalid device sector";
        goto bad;
    }
    lc->start = tmp;

    if (dm_get_device(ti, argv[0], dm_table_get_mode(ti->table), &lc->dev)) {
        ti->error = "dm-linear: Device lookup failed";
        goto bad;
    }

    ti->num_flush_requests = 1;
    ti->num_discard_requests = 1;
    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 sector_t linear_map_sector(struct dm_target *ti, sector_t bi_sector)
{
    struct linear_c *lc = ti->private;

    return lc->start + dm_target_offset(ti, bi_sector);
}

static void linear_map_bio(struct dm_target *ti, struct bio *bio)
{
    struct linear_c *lc = ti->private;

    bio->bi_bdev = lc->dev->bdev;
    if (bio_sectors(bio))
        bio->bi_sector = linear_map_sector(ti, bio->bi_sector);
}

static int linear_map(struct dm_target *ti, struct bio *bio,
              union map_info *map_context)
{
    linear_map_bio(ti, bio);

    return DM_MAPIO_REMAPPED;
}

static int linear_status(struct dm_target *ti, status_type_t type,
             unsigned status_flags, char *result, unsigned 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, unsigned int cmd,
            unsigned long arg)
{
    struct linear_c *lc = (struct linear_c *) ti->private;
    struct dm_dev *dev = lc->dev;
    int r = 0;

    /*
     * Only pass ioctls through if the device sizes match exactly.
     */
    if (lc->start ||
        ti->len != i_size_read(dev->bdev->bd_inode) >> SECTOR_SHIFT)
        r = scsi_verify_blk_ioctl(NULL, cmd);

    return r ? : __blkdev_driver_ioctl(dev->bdev, dev->mode, cmd, arg);
}

static int linear_merge(struct dm_target *ti, struct bvec_merge_data *bvm,
            struct bio_vec *biovec, int max_size)
{
    struct linear_c *lc = ti->private;
    struct request_queue *q = bdev_get_queue(lc->dev->bdev);

    if (!q->merge_bvec_fn)
        return max_size;

    bvm->bi_bdev = lc->dev->bdev;
    bvm->bi_sector = linear_map_sector(ti, bvm->bi_sector);

    return min(max_size, q->merge_bvec_fn(q, bvm, biovec));
}

static int linear_iterate_devices(struct dm_target *ti,
                  iterate_devices_callout_fn fn, void *data)
{
    struct linear_c *lc = ti->private;

    return fn(ti, lc->dev, lc->start, ti->len, data);
}

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

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)
{
    dm_unregister_target(&linear_target);
}