// SPDX-License-Identifier: GPL-2.0
  /*
   * Copyright (c) 2018 Red Hat, Inc.
   *
   * This is a test "dust" device, which fails reads on specified
   * sectors, emulating the behavior of a hard disk drive sending
   * a "Read Medium Error" sense.
   *
   */
  
  #include <linux/device-mapper.h>
  #include <linux/module.h>
  #include <linux/rbtree.h>
  
  #define DM_MSG_PREFIX "dust"
  
  struct badblock {
  	struct rb_node node;
  	sector_t bb;
  };
  
  struct dust_device {
  	struct dm_dev *dev;
  	struct rb_root badblocklist;
  	unsigned long long badblock_count;
  	spinlock_t dust_lock;
  	unsigned int blksz;

  	int sect_per_block_shift;

  	unsigned int sect_per_block;
  	sector_t start;
  	bool fail_read_on_bb:1;
  	bool quiet_mode:1;
  };
  
  static struct badblock *dust_rb_search(struct rb_root *root, sector_t blk)
  {
  	struct rb_node *node = root->rb_node;
  
  	while (node) {
  		struct badblock *bblk = rb_entry(node, struct badblock, node);
  
  		if (bblk->bb > blk)
  			node = node->rb_left;
  		else if (bblk->bb < blk)
  			node = node->rb_right;
  		else
  			return bblk;
  	}
  
  	return NULL;
  }
  
  static bool dust_rb_insert(struct rb_root *root, struct badblock *new)
  {
  	struct badblock *bblk;
  	struct rb_node **link = &root->rb_node, *parent = NULL;
  	sector_t value = new->bb;
  
  	while (*link) {
  		parent = *link;
  		bblk = rb_entry(parent, struct badblock, node);
  
  		if (bblk->bb > value)
  			link = &(*link)->rb_left;
  		else if (bblk->bb < value)
  			link = &(*link)->rb_right;
  		else
  			return false;
  	}
  
  	rb_link_node(&new->node, parent, link);
  	rb_insert_color(&new->node, root);
  
  	return true;
  }
  
  static int dust_remove_block(struct dust_device *dd, unsigned long long block)
  {
  	struct badblock *bblock;
  	unsigned long flags;
  
  	spin_lock_irqsave(&dd->dust_lock, flags);

  	bblock = dust_rb_search(&dd->badblocklist, block);

  
  	if (bblock == NULL) {
  		if (!dd->quiet_mode) {
  			DMERR("%s: block %llu not found in badblocklist",
  			      __func__, block);
  		}
  		spin_unlock_irqrestore(&dd->dust_lock, flags);
  		return -EINVAL;
  	}
  
  	rb_erase(&bblock->node, &dd->badblocklist);
  	dd->badblock_count--;
  	if (!dd->quiet_mode)
  		DMINFO("%s: badblock removed at block %llu", __func__, block);
  	kfree(bblock);
  	spin_unlock_irqrestore(&dd->dust_lock, flags);
  
  	return 0;
  }
  
  static int dust_add_block(struct dust_device *dd, unsigned long long block)
  {
  	struct badblock *bblock;
  	unsigned long flags;
  
  	bblock = kmalloc(sizeof(*bblock), GFP_KERNEL);
  	if (bblock == NULL) {
  		if (!dd->quiet_mode)
  			DMERR("%s: badblock allocation failed", __func__);
  		return -ENOMEM;
  	}
  
  	spin_lock_irqsave(&dd->dust_lock, flags);

  	bblock->bb = block;

  	if (!dust_rb_insert(&dd->badblocklist, bblock)) {
  		if (!dd->quiet_mode) {
  			DMERR("%s: block %llu already in badblocklist",
  			      __func__, block);
  		}
  		spin_unlock_irqrestore(&dd->dust_lock, flags);
  		kfree(bblock);
  		return -EINVAL;
  	}
  
  	dd->badblock_count++;
  	if (!dd->quiet_mode)
  		DMINFO("%s: badblock added at block %llu", __func__, block);
  	spin_unlock_irqrestore(&dd->dust_lock, flags);
  
  	return 0;
  }
  
  static int dust_query_block(struct dust_device *dd, unsigned long long block)
  {
  	struct badblock *bblock;
  	unsigned long flags;
  
  	spin_lock_irqsave(&dd->dust_lock, flags);

  	bblock = dust_rb_search(&dd->badblocklist, block);

  	if (bblock != NULL)
  		DMINFO("%s: block %llu found in badblocklist", __func__, block);
  	else
  		DMINFO("%s: block %llu not found in badblocklist", __func__, block);
  	spin_unlock_irqrestore(&dd->dust_lock, flags);
  
  	return 0;
  }
  
  static int __dust_map_read(struct dust_device *dd, sector_t thisblock)
  {
  	struct badblock *bblk = dust_rb_search(&dd->badblocklist, thisblock);
  
  	if (bblk)
  		return DM_MAPIO_KILL;
  
  	return DM_MAPIO_REMAPPED;
  }
  
  static int dust_map_read(struct dust_device *dd, sector_t thisblock,
  			 bool fail_read_on_bb)
  {
  	unsigned long flags;
  	int ret = DM_MAPIO_REMAPPED;
  
  	if (fail_read_on_bb) {

  		thisblock >>= dd->sect_per_block_shift;

  		spin_lock_irqsave(&dd->dust_lock, flags);
  		ret = __dust_map_read(dd, thisblock);
  		spin_unlock_irqrestore(&dd->dust_lock, flags);
  	}
  
  	return ret;
  }
  
  static void __dust_map_write(struct dust_device *dd, sector_t thisblock)
  {
  	struct badblock *bblk = dust_rb_search(&dd->badblocklist, thisblock);
  
  	if (bblk) {
  		rb_erase(&bblk->node, &dd->badblocklist);
  		dd->badblock_count--;
  		kfree(bblk);
  		if (!dd->quiet_mode) {
  			sector_div(thisblock, dd->sect_per_block);
  			DMINFO("block %llu removed from badblocklist by write",
  			       (unsigned long long)thisblock);
  		}
  	}
  }
  
  static int dust_map_write(struct dust_device *dd, sector_t thisblock,
  			  bool fail_read_on_bb)
  {
  	unsigned long flags;
  
  	if (fail_read_on_bb) {

  		thisblock >>= dd->sect_per_block_shift;

  		spin_lock_irqsave(&dd->dust_lock, flags);
  		__dust_map_write(dd, thisblock);
  		spin_unlock_irqrestore(&dd->dust_lock, flags);
  	}
  
  	return DM_MAPIO_REMAPPED;
  }
  
  static int dust_map(struct dm_target *ti, struct bio *bio)
  {
  	struct dust_device *dd = ti->private;
  	int ret;
  
  	bio_set_dev(bio, dd->dev->bdev);
  	bio->bi_iter.bi_sector = dd->start + dm_target_offset(ti, bio->bi_iter.bi_sector);
  
  	if (bio_data_dir(bio) == READ)
  		ret = dust_map_read(dd, bio->bi_iter.bi_sector, dd->fail_read_on_bb);
  	else
  		ret = dust_map_write(dd, bio->bi_iter.bi_sector, dd->fail_read_on_bb);
  
  	return ret;
  }
  
  static bool __dust_clear_badblocks(struct rb_root *tree,
  				   unsigned long long count)
  {
  	struct rb_node *node = NULL, *nnode = NULL;
  
  	nnode = rb_first(tree);
  	if (nnode == NULL) {
  		BUG_ON(count != 0);
  		return false;
  	}
  
  	while (nnode) {
  		node = nnode;
  		nnode = rb_next(node);
  		rb_erase(node, tree);
  		count--;
  		kfree(node);
  	}
  	BUG_ON(count != 0);
  	BUG_ON(tree->rb_node != NULL);
  
  	return true;
  }
  
  static int dust_clear_badblocks(struct dust_device *dd)
  {
  	unsigned long flags;
  	struct rb_root badblocklist;
  	unsigned long long badblock_count;
  
  	spin_lock_irqsave(&dd->dust_lock, flags);
  	badblocklist = dd->badblocklist;
  	badblock_count = dd->badblock_count;
  	dd->badblocklist = RB_ROOT;
  	dd->badblock_count = 0;
  	spin_unlock_irqrestore(&dd->dust_lock, flags);
  
  	if (!__dust_clear_badblocks(&badblocklist, badblock_count))
  		DMINFO("%s: no badblocks found", __func__);
  	else
  		DMINFO("%s: badblocks cleared", __func__);
  
  	return 0;
  }
  
  /*
   * Target parameters:
   *
   * <device_path> <offset> <blksz>
   *
   * device_path: path to the block device
   * offset: offset to data area from start of device_path
   * blksz: block size (minimum 512, maximum 1073741824, must be a power of 2)
   */
  static int dust_ctr(struct dm_target *ti, unsigned int argc, char **argv)
  {
  	struct dust_device *dd;
  	unsigned long long tmp;
  	char dummy;
  	unsigned int blksz;
  	unsigned int sect_per_block;
  	sector_t DUST_MAX_BLKSZ_SECTORS = 2097152;
  	sector_t max_block_sectors = min(ti->len, DUST_MAX_BLKSZ_SECTORS);
  
  	if (argc != 3) {
  		ti->error = "Invalid argument count";
  		return -EINVAL;
  	}
  
  	if (kstrtouint(argv[2], 10, &blksz) || !blksz) {
  		ti->error = "Invalid block size parameter";
  		return -EINVAL;
  	}
  
  	if (blksz < 512) {
  		ti->error = "Block size must be at least 512";
  		return -EINVAL;
  	}
  
  	if (!is_power_of_2(blksz)) {
  		ti->error = "Block size must be a power of 2";
  		return -EINVAL;
  	}
  
  	if (to_sector(blksz) > max_block_sectors) {
  		ti->error = "Block size is too large";
  		return -EINVAL;
  	}
  
  	sect_per_block = (blksz >> SECTOR_SHIFT);
  
  	if (sscanf(argv[1], "%llu%c", &tmp, &dummy) != 1 || tmp != (sector_t)tmp) {
  		ti->error = "Invalid device offset sector";
  		return -EINVAL;
  	}
  
  	dd = kzalloc(sizeof(struct dust_device), GFP_KERNEL);
  	if (dd == NULL) {
  		ti->error = "Cannot allocate context";
  		return -ENOMEM;
  	}
  
  	if (dm_get_device(ti, argv[0], dm_table_get_mode(ti->table), &dd->dev)) {
  		ti->error = "Device lookup failed";
  		kfree(dd);
  		return -EINVAL;
  	}
  
  	dd->sect_per_block = sect_per_block;
  	dd->blksz = blksz;
  	dd->start = tmp;

  	dd->sect_per_block_shift = __ffs(sect_per_block);

  	/*
  	 * Whether to fail a read on a "bad" block.
  	 * Defaults to false; enabled later by message.
  	 */
  	dd->fail_read_on_bb = false;
  
  	/*
  	 * Initialize bad block list rbtree.
  	 */
  	dd->badblocklist = RB_ROOT;
  	dd->badblock_count = 0;
  	spin_lock_init(&dd->dust_lock);
  
  	dd->quiet_mode = false;
  
  	BUG_ON(dm_set_target_max_io_len(ti, dd->sect_per_block) != 0);
  
  	ti->num_discard_bios = 1;
  	ti->num_flush_bios = 1;
  	ti->private = dd;
  
  	return 0;
  }
  
  static void dust_dtr(struct dm_target *ti)
  {
  	struct dust_device *dd = ti->private;
  
  	__dust_clear_badblocks(&dd->badblocklist, dd->badblock_count);
  	dm_put_device(ti, dd->dev);
  	kfree(dd);
  }
  
  static int dust_message(struct dm_target *ti, unsigned int argc, char **argv,
  			char *result_buf, unsigned int maxlen)
  {
  	struct dust_device *dd = ti->private;
  	sector_t size = i_size_read(dd->dev->bdev->bd_inode) >> SECTOR_SHIFT;
  	bool invalid_msg = false;
  	int result = -EINVAL;
  	unsigned long long tmp, block;
  	unsigned long flags;
  	char dummy;
  
  	if (argc == 1) {
  		if (!strcasecmp(argv[0], "addbadblock") ||
  		    !strcasecmp(argv[0], "removebadblock") ||
  		    !strcasecmp(argv[0], "queryblock")) {
  			DMERR("%s requires an additional argument", argv[0]);
  		} else if (!strcasecmp(argv[0], "disable")) {
  			DMINFO("disabling read failures on bad sectors");
  			dd->fail_read_on_bb = false;
  			result = 0;
  		} else if (!strcasecmp(argv[0], "enable")) {
  			DMINFO("enabling read failures on bad sectors");
  			dd->fail_read_on_bb = true;
  			result = 0;
  		} else if (!strcasecmp(argv[0], "countbadblocks")) {
  			spin_lock_irqsave(&dd->dust_lock, flags);
  			DMINFO("countbadblocks: %llu badblock(s) found",
  			       dd->badblock_count);
  			spin_unlock_irqrestore(&dd->dust_lock, flags);
  			result = 0;
  		} else if (!strcasecmp(argv[0], "clearbadblocks")) {
  			result = dust_clear_badblocks(dd);
  		} else if (!strcasecmp(argv[0], "quiet")) {
  			if (!dd->quiet_mode)
  				dd->quiet_mode = true;
  			else
  				dd->quiet_mode = false;
  			result = 0;
  		} else {
  			invalid_msg = true;
  		}
  	} else if (argc == 2) {
  		if (sscanf(argv[1], "%llu%c", &tmp, &dummy) != 1)
  			return result;
  
  		block = tmp;
  		sector_div(size, dd->sect_per_block);

  		if (block > size) {

  			DMERR("selected block value out of range");
  			return result;
  		}
  
  		if (!strcasecmp(argv[0], "addbadblock"))
  			result = dust_add_block(dd, block);
  		else if (!strcasecmp(argv[0], "removebadblock"))
  			result = dust_remove_block(dd, block);
  		else if (!strcasecmp(argv[0], "queryblock"))
  			result = dust_query_block(dd, block);
  		else
  			invalid_msg = true;
  
  	} else
  		DMERR("invalid number of arguments '%d'", argc);
  
  	if (invalid_msg)
  		DMERR("unrecognized message '%s' received", argv[0]);
  
  	return result;
  }
  
  static void dust_status(struct dm_target *ti, status_type_t type,
  			unsigned int status_flags, char *result, unsigned int maxlen)
  {
  	struct dust_device *dd = ti->private;
  	unsigned int sz = 0;
  
  	switch (type) {
  	case STATUSTYPE_INFO:
  		DMEMIT("%s %s %s", dd->dev->name,
  		       dd->fail_read_on_bb ? "fail_read_on_bad_block" : "bypass",
  		       dd->quiet_mode ? "quiet" : "verbose");
  		break;
  
  	case STATUSTYPE_TABLE:
  		DMEMIT("%s %llu %u", dd->dev->name,
  		       (unsigned long long)dd->start, dd->blksz);
  		break;
  	}
  }
  
  static int dust_prepare_ioctl(struct dm_target *ti, struct block_device **bdev)
  {
  	struct dust_device *dd = ti->private;
  	struct dm_dev *dev = dd->dev;
  
  	*bdev = dev->bdev;
  
  	/*
  	 * Only pass ioctls through if the device sizes match exactly.
  	 */
  	if (dd->start ||
  	    ti->len != i_size_read(dev->bdev->bd_inode) >> SECTOR_SHIFT)
  		return 1;
  
  	return 0;
  }
  
  static int dust_iterate_devices(struct dm_target *ti, iterate_devices_callout_fn fn,
  				void *data)
  {
  	struct dust_device *dd = ti->private;
  
  	return fn(ti, dd->dev, dd->start, ti->len, data);
  }
  
  static struct target_type dust_target = {
  	.name = "dust",
  	.version = {1, 0, 0},
  	.module = THIS_MODULE,
  	.ctr = dust_ctr,
  	.dtr = dust_dtr,
  	.iterate_devices = dust_iterate_devices,
  	.map = dust_map,
  	.message = dust_message,
  	.status = dust_status,
  	.prepare_ioctl = dust_prepare_ioctl,
  };

  static int __init dm_dust_init(void)

  {
  	int result = dm_register_target(&dust_target);
  
  	if (result < 0)
  		DMERR("dm_register_target failed %d", result);
  
  	return result;
  }

  static void __exit dm_dust_exit(void)

  {
  	dm_unregister_target(&dust_target);
  }
  
  module_init(dm_dust_init);
  module_exit(dm_dust_exit);
  
  MODULE_DESCRIPTION(DM_NAME " dust test target");
  MODULE_AUTHOR("Bryan Gurney <dm-devel@redhat.com>");
  MODULE_LICENSE("GPL");