diff --git a/Documentation/device-mapper/dm-dust.txt b/Documentation/device-mapper/dm-dust.txt
new file mode 100644
index 000000000000..e0b6fa0b9f25
--- /dev/null
+++ b/Documentation/device-mapper/dm-dust.txt
@@ -0,0 +1,271 @@
+dm-dust
+=======
+
+This target emulates the behavior of bad sectors at arbitrary
+locations, and the ability to enable the emulation of the failures
+at an arbitrary time.
+
+This target behaves similarly to a linear target.  At a given time,
+the user can send a message to the target to start failing read
+requests on specific blocks (to emulate the behavior of a hard disk
+drive with bad sectors).
+
+When the failure behavior is enabled (i.e.: when the output of
+"dmsetup status" displays "fail_read_on_bad_block"), reads of blocks
+in the "bad block list" will fail with EIO ("Input/output error").
+
+Writes of blocks in the "bad block list will result in the following:
+
+1. Remove the block from the "bad block list".
+2. Successfully complete the write.
+
+This emulates the "remapped sector" behavior of a drive with bad
+sectors.
+
+Normally, a drive that is encountering bad sectors will most likely
+encounter more bad sectors, at an unknown time or location.
+With dm-dust, the user can use the "addbadblock" and "removebadblock"
+messages to add arbitrary bad blocks at new locations, and the
+"enable" and "disable" messages to modulate the state of whether the
+configured "bad blocks" will be treated as bad, or bypassed.
+This allows the pre-writing of test data and metadata prior to
+simulating a "failure" event where bad sectors start to appear.
+
+Table parameters:
+-----------------
+<device_path> <blksz>
+
+Mandatory parameters:
+    <device_path>: path to the block device.
+    <blksz>: block size in bytes
+	     (minimum 512, maximum 1073741824, must be a power of 2)
+
+Usage instructions:
+-------------------
+
+First, find the size (in 512-byte sectors) of the device to be used:
+
+$ sudo blockdev --getsz /dev/vdb1
+33552384
+
+Create the dm-dust device:
+(For a device with a block size of 512 bytes)
+$ sudo dmsetup create dust1 --table '0 33552384 dust /dev/vdb1 512'
+
+(For a device with a block size of 4096 bytes)
+$ sudo dmsetup create dust1 --table '0 33552384 dust /dev/vdb1 4096'
+
+Check the status of the read behavior ("bypass" indicates that all I/O
+will be passed through to the underlying device):
+$ sudo dmsetup status dust1
+0 33552384 dust 252:17 bypass
+
+$ sudo dd if=/dev/mapper/dust1 of=/dev/null bs=512 count=128 iflag=direct
+128+0 records in
+128+0 records out
+
+$ sudo dd if=/dev/zero of=/dev/mapper/dust1 bs=512 count=128 oflag=direct
+128+0 records in
+128+0 records out
+
+Adding and removing bad blocks:
+-------------------------------
+
+At any time (i.e.: whether the device has the "bad block" emulation
+enabled or disabled), bad blocks may be added or removed from the
+device via the "addbadblock" and "removebadblock" messages:
+
+$ sudo dmsetup message dust1 0 addbadblock 60
+kernel: device-mapper: dust: badblock added at block 60
+
+$ sudo dmsetup message dust1 0 addbadblock 67
+kernel: device-mapper: dust: badblock added at block 67
+
+$ sudo dmsetup message dust1 0 addbadblock 72
+kernel: device-mapper: dust: badblock added at block 72
+
+These bad blocks will be stored in the "bad block list".
+While the device is in "bypass" mode, reads and writes will succeed:
+
+$ sudo dmsetup status dust1
+0 33552384 dust 252:17 bypass
+
+Enabling block read failures:
+-----------------------------
+
+To enable the "fail read on bad block" behavior, send the "enable" message:
+
+$ sudo dmsetup message dust1 0 enable
+kernel: device-mapper: dust: enabling read failures on bad sectors
+
+$ sudo dmsetup status dust1
+0 33552384 dust 252:17 fail_read_on_bad_block
+
+With the device in "fail read on bad block" mode, attempting to read a
+block will encounter an "Input/output error":
+
+$ sudo dd if=/dev/mapper/dust1 of=/dev/null bs=512 count=1 skip=67 iflag=direct
+dd: error reading '/dev/mapper/dust1': Input/output error
+0+0 records in
+0+0 records out
+0 bytes copied, 0.00040651 s, 0.0 kB/s
+
+...and writing to the bad blocks will remove the blocks from the list,
+therefore emulating the "remap" behavior of hard disk drives:
+
+$ sudo dd if=/dev/zero of=/dev/mapper/dust1 bs=512 count=128 oflag=direct
+128+0 records in
+128+0 records out
+
+kernel: device-mapper: dust: block 60 removed from badblocklist by write
+kernel: device-mapper: dust: block 67 removed from badblocklist by write
+kernel: device-mapper: dust: block 72 removed from badblocklist by write
+kernel: device-mapper: dust: block 87 removed from badblocklist by write
+
+Bad block add/remove error handling:
+------------------------------------
+
+Attempting to add a bad block that already exists in the list will
+result in an "Invalid argument" error, as well as a helpful message:
+
+$ sudo dmsetup message dust1 0 addbadblock 88
+device-mapper: message ioctl on dust1  failed: Invalid argument
+kernel: device-mapper: dust: block 88 already in badblocklist
+
+Attempting to remove a bad block that doesn't exist in the list will
+result in an "Invalid argument" error, as well as a helpful message:
+
+$ sudo dmsetup message dust1 0 removebadblock 87
+device-mapper: message ioctl on dust1  failed: Invalid argument
+kernel: device-mapper: dust: block 87 not found in badblocklist
+
+Counting the number of bad blocks in the bad block list:
+--------------------------------------------------------
+
+To count the number of bad blocks configured in the device, run the
+following message command:
+
+$ sudo dmsetup message dust1 0 countbadblocks
+
+A message will print with the number of bad blocks currently
+configured on the device:
+
+kernel: device-mapper: dust: countbadblocks: 895 badblock(s) found
+
+Querying for specific bad blocks:
+---------------------------------
+
+To find out if a specific block is in the bad block list, run the
+following message command:
+
+$ sudo dmsetup message dust1 0 queryblock 72
+
+The following message will print if the block is in the list:
+device-mapper: dust: queryblock: block 72 found in badblocklist
+
+The following message will print if the block is in the list:
+device-mapper: dust: queryblock: block 72 not found in badblocklist
+
+The "queryblock" message command will work in both the "enabled"
+and "disabled" modes, allowing the verification of whether a block
+will be treated as "bad" without having to issue I/O to the device,
+or having to "enable" the bad block emulation.
+
+Clearing the bad block list:
+----------------------------
+
+To clear the bad block list (without needing to individually run
+a "removebadblock" message command for every block), run the
+following message command:
+
+$ sudo dmsetup message dust1 0 clearbadblocks
+
+After clearing the bad block list, the following message will appear:
+
+kernel: device-mapper: dust: clearbadblocks: badblocks cleared
+
+If there were no bad blocks to clear, the following message will
+appear:
+
+kernel: device-mapper: dust: clearbadblocks: no badblocks found
+
+Message commands list:
+----------------------
+
+Below is a list of the messages that can be sent to a dust device:
+
+Operations on blocks (requires a <blknum> argument):
+
+addbadblock <blknum>
+queryblock <blknum>
+removebadblock <blknum>
+
+...where <blknum> is a block number within range of the device
+  (corresponding to the block size of the device.)
+
+Single argument message commands:
+
+countbadblocks
+clearbadblocks
+disable
+enable
+quiet
+
+Device removal:
+---------------
+
+When finished, remove the device via the "dmsetup remove" command:
+
+$ sudo dmsetup remove dust1
+
+Quiet mode:
+-----------
+
+On test runs with many bad blocks, it may be desirable to avoid
+excessive logging (from bad blocks added, removed, or "remapped").
+This can be done by enabling "quiet mode" via the following message:
+
+$ sudo dmsetup message dust1 0 quiet
+
+This will suppress log messages from add / remove / removed by write
+operations.  Log messages from "countbadblocks" or "queryblock"
+message commands will still print in quiet mode.
+
+The status of quiet mode can be seen by running "dmsetup status":
+
+$ sudo dmsetup status dust1
+0 33552384 dust 252:17 fail_read_on_bad_block quiet
+
+To disable quiet mode, send the "quiet" message again:
+
+$ sudo dmsetup message dust1 0 quiet
+
+$ sudo dmsetup status dust1
+0 33552384 dust 252:17 fail_read_on_bad_block verbose
+
+(The presence of "verbose" indicates normal logging.)
+
+"Why not...?"
+-------------
+
+scsi_debug has a "medium error" mode that can fail reads on one
+specified sector (sector 0x1234, hardcoded in the source code), but
+it uses RAM for the persistent storage, which drastically decreases
+the potential device size.
+
+dm-flakey fails all I/O from all block locations at a specified time
+frequency, and not a given point in time.
+
+When a bad sector occurs on a hard disk drive, reads to that sector
+are failed by the device, usually resulting in an error code of EIO
+("I/O error") or ENODATA ("No data available").  However, a write to
+the sector may succeed, and result in the sector becoming readable
+after the device controller no longer experiences errors reading the
+sector (or after a reallocation of the sector).  However, there may
+be bad sectors that occur on the device in the future, in a different,
+unpredictable location.
+
+This target seeks to provide a device that can exhibit the behavior
+of a bad sector at a known sector location, at a known time, based
+on a large storage device (at least tens of gigabytes, not occupying
+system memory).
diff --git a/drivers/md/Kconfig b/drivers/md/Kconfig
index 2557f198e175..db269a348b20 100644
--- a/drivers/md/Kconfig
+++ b/drivers/md/Kconfig
@@ -436,6 +436,15 @@ config DM_DELAY
 
 	If unsure, say N.
 
+config DM_DUST
+	tristate "Bad sector simulation target"
+	depends on BLK_DEV_DM
+	---help---
+	A target that simulates bad sector behavior.
+	Useful for testing.
+
+	If unsure, say N.
+
 config DM_INIT
 	bool "DM \"dm-mod.create=\" parameter support"
 	depends on BLK_DEV_DM=y
diff --git a/drivers/md/Makefile b/drivers/md/Makefile
index a52b703e588e..be7a6eb92abc 100644
--- a/drivers/md/Makefile
+++ b/drivers/md/Makefile
@@ -48,6 +48,7 @@ obj-$(CONFIG_DM_BUFIO)		+= dm-bufio.o
 obj-$(CONFIG_DM_BIO_PRISON)	+= dm-bio-prison.o
 obj-$(CONFIG_DM_CRYPT)		+= dm-crypt.o
 obj-$(CONFIG_DM_DELAY)		+= dm-delay.o
+obj-$(CONFIG_DM_DUST)		+= dm-dust.o
 obj-$(CONFIG_DM_FLAKEY)		+= dm-flakey.o
 obj-$(CONFIG_DM_MULTIPATH)	+= dm-multipath.o dm-round-robin.o
 obj-$(CONFIG_DM_MULTIPATH_QL)	+= dm-queue-length.o
diff --git a/drivers/md/dm-dust.c b/drivers/md/dm-dust.c
new file mode 100644
index 000000000000..662406aae660
--- /dev/null
+++ b/drivers/md/dm-dust.c
@@ -0,0 +1,516 @@
+// 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/version.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;
+	bool fail_read_on_bb;
+	struct rb_root badblocklist;
+	unsigned long long badblock_count;
+	spinlock_t dust_lock;
+	unsigned int blksz;
+	unsigned int sect_per_block;
+	bool quiet_mode;
+};
+
+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;
+}
+
+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 * dd->sect_per_block);
+
+	if (bblock == NULL) {
+		if (!dd->quiet_mode)
+			DMERR("removebadblock: block %llu not found in badblocklist",
+			      block);
+		spin_unlock_irqrestore(&dd->dust_lock, flags);
+		return -EINVAL;
+	}
+
+	rb_erase(&bblock->node, &dd->badblocklist);
+	dd->badblock_count--;
+	if (!dd->quiet_mode)
+		DMINFO("removebadblock: badblock removed at block %llu", 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("addbadblock: badblock allocation failed");
+		return -ENOMEM;
+	}
+
+	spin_lock_irqsave(&dd->dust_lock, flags);
+	bblock->bb = block * dd->sect_per_block;
+	if (!dust_rb_insert(&dd->badblocklist, bblock)) {
+		if (!dd->quiet_mode)
+			DMERR("addbadblock: block %llu already in badblocklist",
+			      block);
+		spin_unlock_irqrestore(&dd->dust_lock, flags);
+		kfree(bblock);
+		return -EINVAL;
+	}
+
+	dd->badblock_count++;
+	if (!dd->quiet_mode)
+		DMINFO("addbadblock: badblock added at block %llu", 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 * dd->sect_per_block);
+
+	if (bblock != NULL)
+		DMINFO("queryblock: block %llu found in badblocklist", block);
+	else
+		DMINFO("queryblock: block %llu not found in badblocklist",
+		       block);
+
+	spin_unlock_irqrestore(&dd->dust_lock, flags);
+	return 0;
+}
+
+static int dust_mod_r_failbad(struct dust_device *dd, sector_t thisblock)
+{
+	unsigned long flags;
+	struct badblock *bblk;
+
+	spin_lock_irqsave(&dd->dust_lock, flags);
+	bblk = dust_rb_search(&dd->badblocklist, thisblock);
+
+	if (bblk) {
+		spin_unlock_irqrestore(&dd->dust_lock, flags);
+		return DM_MAPIO_KILL;
+	}
+
+	spin_unlock_irqrestore(&dd->dust_lock, flags);
+	return DM_MAPIO_REMAPPED;
+}
+
+static int dust_map_read(struct dust_device *dd, sector_t thisblock,
+			 bool fail_read_on_bb)
+{
+	int ret;
+
+	if (fail_read_on_bb) {
+		ret = dust_mod_r_failbad(dd, thisblock);
+		return ret;
+	}
+
+	return DM_MAPIO_REMAPPED;
+}
+
+static void dust_mod_w_remapbad(struct dust_device *dd, sector_t thisblock)
+{
+	unsigned long flags;
+	struct badblock *bblk;
+
+	spin_lock_irqsave(&dd->dust_lock, flags);
+	bblk = dust_rb_search(&dd->badblocklist, thisblock);
+
+	if (bblk) {
+		rb_erase(&bblk->node, &dd->badblocklist);
+		dd->badblock_count--;
+		kfree(bblk);
+		if (!dd->quiet_mode)
+			DMINFO("block %llu removed from badblocklist by write",
+				(unsigned long long)thisblock / dd->sect_per_block);
+}
+
+	spin_unlock_irqrestore(&dd->dust_lock, flags);
+}
+
+static int dust_map_write(struct dust_device *dd, sector_t thisblock,
+			  bool fail_read_on_bb)
+{
+	if (fail_read_on_bb)
+		dust_mod_w_remapbad(dd, thisblock);
+
+	return DM_MAPIO_REMAPPED;
+}
+
+static inline void dust_set_biosector(struct bio *bio, sector_t sector)
+{
+	bio->bi_iter.bi_sector = sector;
+}
+
+static inline sector_t dust_get_biosector(struct bio *bio)
+{
+	return bio->bi_iter.bi_sector;
+}
+
+static int __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 0;
+	}
+
+	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 1;
+}
+
+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) == 0)
+		DMINFO("clearbadblocks: no badblocks found");
+	else
+		DMINFO("clearbadblocks: badblocks cleared");
+	return 0;
+}
+
+/*
+ * Target parameters:
+ *
+ * <device_path> <blksz>
+ *
+ * device_path: path to the block device
+ * 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;
+	const char *device_path = argv[0];
+	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 != 2) {
+		ti->error = "requires exactly 2 arguments";
+		return -EINVAL;
+	}
+
+	if (kstrtouint(argv[1], 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);
+
+	dd = kzalloc(sizeof(struct dust_device), GFP_KERNEL);
+
+	if (dd == NULL) {
+		ti->error = "Cannot allocate context";
+		return -ENOMEM;
+	}
+
+	if (dm_get_device(ti, device_path, 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;
+
+	// Whether to fail a read on a "bad" block.
+	// Defaults to false; enabled later by message.
+	dd->fail_read_on_bb = false;
+
+	// Bad block list rbtree.
+	// Just initialize for now.
+	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_map(struct dm_target *ti, struct bio *bio)
+{
+	struct dust_device *dd;
+	sector_t thisblock;
+	int ret;
+
+	dd = ti->private;
+	bio_set_dev(bio, dd->dev->bdev);
+	dust_set_biosector(bio, dm_target_offset(ti, dust_get_biosector(bio)));
+	thisblock = dust_get_biosector(bio);
+
+	if (bio_data_dir(bio) == READ)
+		ret = dust_map_read(dd, thisblock, dd->fail_read_on_bb);
+	if (bio_data_dir(bio) == WRITE)
+		ret = dust_map_write(dd, thisblock, dd->fail_read_on_bb);
+
+	return ret;
+}
+
+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;
+
+		if (block > size / dd->sect_per_block || block < 0) {
+			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 dmsetup 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; // used by the DMEMIT macro
+
+	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 %u", dd->dev->name, 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 (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, 0, 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,
+};
+
+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;
+}
+
+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 testing device");
+MODULE_AUTHOR("Red Hat, Inc.");
+MODULE_LICENSE("GPL");
