/*
 * 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/dax.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;
        int ret;

        if (argc != 2) {
                ti->error = "Invalid argument count";
                return -EINVAL;
        }

        lc = kmalloc(sizeof(*lc), GFP_KERNEL);
        if (lc == NULL) {
                ti->error = "Cannot allocate linear context";
                return -ENOMEM;
        }

        ret = -EINVAL;
        if (sscanf(argv[1], "%llu%c", &tmp, &dummy) != 1) {
                ti->error = "Invalid device sector";
                goto bad;
        }
        lc->start = tmp;

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

        ti->num_flush_bios = 1;
        ti->num_discard_bios = 1;
        ti->num_write_same_bios = 1;
        ti->num_write_zeroes_bios = 1;
        ti->private = lc;
        return 0;

      bad:
        kfree(lc);
        return ret;
}

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_set_dev(bio, lc->dev->bdev);
        if (bio_sectors(bio) || bio_op(bio) == REQ_OP_ZONE_RESET)
                bio->bi_iter.bi_sector =
                        linear_map_sector(ti, bio->bi_iter.bi_sector);
}

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

        return DM_MAPIO_REMAPPED;
}

static int linear_end_io(struct dm_target *ti, struct bio *bio,
                         blk_status_t *error)
{
        struct linear_c *lc = ti->private;

        if (!*error && bio_op(bio) == REQ_OP_ZONE_REPORT)
                dm_remap_zone_report(ti, bio, lc->start);

        return DM_ENDIO_DONE;
}

static void 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;
        }
}

static int linear_prepare_ioctl(struct dm_target *ti,
                struct block_device **bdev, fmode_t *mode)
{
        struct linear_c *lc = (struct linear_c *) ti->private;
        struct dm_dev *dev = lc->dev;

        *bdev = dev->bdev;

        /*
         * Only pass ioctls through if the device sizes match exactly.
         */
        if (lc->start ||
            ti->len != i_size_read(dev->bdev->bd_inode) >> SECTOR_SHIFT)
                return 1;
        return 0;
}

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 long linear_dax_direct_access(struct dm_target *ti, pgoff_t pgoff,
                long nr_pages, void **kaddr, pfn_t *pfn)
{
        long ret;
        struct linear_c *lc = ti->private;
        struct block_device *bdev = lc->dev->bdev;
        struct dax_device *dax_dev = lc->dev->dax_dev;
        sector_t dev_sector, sector = pgoff * PAGE_SECTORS;

        dev_sector = linear_map_sector(ti, sector);
        ret = bdev_dax_pgoff(bdev, dev_sector, nr_pages * PAGE_SIZE, &pgoff);
        if (ret)
                return ret;
        return dax_direct_access(dax_dev, pgoff, nr_pages, kaddr, pfn);
}

static size_t linear_dax_copy_from_iter(struct dm_target *ti, pgoff_t pgoff,
                void *addr, size_t bytes, struct iov_iter *i)
{
        struct linear_c *lc = ti->private;
        struct block_device *bdev = lc->dev->bdev;
        struct dax_device *dax_dev = lc->dev->dax_dev;
        sector_t dev_sector, sector = pgoff * PAGE_SECTORS;

        dev_sector = linear_map_sector(ti, sector);
        if (bdev_dax_pgoff(bdev, dev_sector, ALIGN(bytes, PAGE_SIZE), &pgoff))
                return 0;
        return dax_copy_from_iter(dax_dev, pgoff, addr, bytes, i);
}

static struct target_type linear_target = {
        .name   = "linear",
        .version = {1, 4, 0},
        .features = DM_TARGET_PASSES_INTEGRITY | DM_TARGET_ZONED_HM,
        .module = THIS_MODULE,
        .ctr    = linear_ctr,
        .dtr    = linear_dtr,
        .map    = linear_map,
        .end_io = linear_end_io,
        .status = linear_status,
        .prepare_ioctl = linear_prepare_ioctl,
        .iterate_devices = linear_iterate_devices,
        .direct_access = linear_dax_direct_access,
        .dax_copy_from_iter = linear_dax_copy_from_iter,
};

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);
}