dm: add dust target

Add the dm-dust target, which simulates the behavior of bad sectors
at arbitrary locations, and the ability to enable the emulation of
the read 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.  When the failure behavior is enabled,
reads of blocks configured "bad" will fail with EIO.

Writes of blocks configured "bad" will result in the following:

1. Remove the block from the "bad block list".
2. Successfully complete the write.

After this point, the block will successfully contain the written
data, and will service reads and writes normally.  This emulates the
behavior of a "remapped sector" on a hard disk drive.

dm-dust provides logging of which blocks have been added or removed
to the "bad block list", as well as logging when a block has been
removed from the bad block list.  These messages can be used
alongside the messages from the driver using a dm-dust device to
analyze the driver's behavior when a read fails at a given time.

(This logging can be reduced via a "quiet" mode, if desired.)

NOTE: If the block size is larger than 512 bytes, only the first sector
of each "dust block" is detected.  Placing a limiting layer above a dust
target, to limit the minimum I/O size to the dust block size, will
ensure proper emulation of the given large block size.

Signed-off-by: Bryan Gurney <bgurney@redhat.com>
Co-developed-by: Joe Shimkus <jshimkus@redhat.com>
Co-developed-by: John Dorminy <jdorminy@redhat.com>
Co-developed-by: John Pittman <jpittman@redhat.com>
Co-developed-by: Thomas Jaskiewicz <tjaskiew@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This commit is contained in:
Bryan Gurney 2019-03-07 15:42:39 -05:00 committed by Mike Snitzer
parent f8011d3344
commit e4f3fabd67
4 changed files with 797 additions and 0 deletions

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@ -0,0 +1,272 @@
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> <offset> <blksz>
Mandatory parameters:
<device_path>: path to the block device.
<offset>: offset to data area from start of device_path
<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 0 512'
(For a device with a block size of 4096 bytes)
$ sudo dmsetup create dust1 --table '0 33552384 dust /dev/vdb1 0 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).

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@ -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

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@ -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

515
drivers/md/dm-dust.c Normal file
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@ -0,0 +1,515 @@
// 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;
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 * dd->sect_per_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 * dd->sect_per_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 * dd->sect_per_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) {
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) {
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;
/*
* 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 || 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 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,
};
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 test target");
MODULE_AUTHOR("Bryan Gurney <dm-devel@redhat.com>");
MODULE_LICENSE("GPL");