drivers/md/dm-dust.c - linux - Git at Google

 // 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");
	// 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");