Revision 9559cc239d6cf50bf64de0bd7662103238e84274 authored by Jeff Garzik on 18 January 2008, 19:40:47 UTC, committed by Jeff Garzik on 18 January 2008, 19:40:47 UTC
dm-table.c
/*
* Copyright (C) 2001 Sistina Software (UK) Limited.
* Copyright (C) 2004 Red Hat, Inc. All rights reserved.
*
* This file is released under the GPL.
*/
#include "dm.h"
#include <linux/module.h>
#include <linux/vmalloc.h>
#include <linux/blkdev.h>
#include <linux/namei.h>
#include <linux/ctype.h>
#include <linux/slab.h>
#include <linux/interrupt.h>
#include <linux/mutex.h>
#include <asm/atomic.h>
#define DM_MSG_PREFIX "table"
#define MAX_DEPTH 16
#define NODE_SIZE L1_CACHE_BYTES
#define KEYS_PER_NODE (NODE_SIZE / sizeof(sector_t))
#define CHILDREN_PER_NODE (KEYS_PER_NODE + 1)
struct dm_table {
struct mapped_device *md;
atomic_t holders;
/* btree table */
unsigned int depth;
unsigned int counts[MAX_DEPTH]; /* in nodes */
sector_t *index[MAX_DEPTH];
unsigned int num_targets;
unsigned int num_allocated;
sector_t *highs;
struct dm_target *targets;
/*
* Indicates the rw permissions for the new logical
* device. This should be a combination of FMODE_READ
* and FMODE_WRITE.
*/
int mode;
/* a list of devices used by this table */
struct list_head devices;
/*
* These are optimistic limits taken from all the
* targets, some targets will need smaller limits.
*/
struct io_restrictions limits;
/* events get handed up using this callback */
void (*event_fn)(void *);
void *event_context;
};
/*
* Similar to ceiling(log_size(n))
*/
static unsigned int int_log(unsigned int n, unsigned int base)
{
int result = 0;
while (n > 1) {
n = dm_div_up(n, base);
result++;
}
return result;
}
/*
* Returns the minimum that is _not_ zero, unless both are zero.
*/
#define min_not_zero(l, r) (l == 0) ? r : ((r == 0) ? l : min(l, r))
/*
* Combine two io_restrictions, always taking the lower value.
*/
static void combine_restrictions_low(struct io_restrictions *lhs,
struct io_restrictions *rhs)
{
lhs->max_sectors =
min_not_zero(lhs->max_sectors, rhs->max_sectors);
lhs->max_phys_segments =
min_not_zero(lhs->max_phys_segments, rhs->max_phys_segments);
lhs->max_hw_segments =
min_not_zero(lhs->max_hw_segments, rhs->max_hw_segments);
lhs->hardsect_size = max(lhs->hardsect_size, rhs->hardsect_size);
lhs->max_segment_size =
min_not_zero(lhs->max_segment_size, rhs->max_segment_size);
lhs->max_hw_sectors =
min_not_zero(lhs->max_hw_sectors, rhs->max_hw_sectors);
lhs->seg_boundary_mask =
min_not_zero(lhs->seg_boundary_mask, rhs->seg_boundary_mask);
lhs->bounce_pfn = min_not_zero(lhs->bounce_pfn, rhs->bounce_pfn);
lhs->no_cluster |= rhs->no_cluster;
}
/*
* Calculate the index of the child node of the n'th node k'th key.
*/
static inline unsigned int get_child(unsigned int n, unsigned int k)
{
return (n * CHILDREN_PER_NODE) + k;
}
/*
* Return the n'th node of level l from table t.
*/
static inline sector_t *get_node(struct dm_table *t,
unsigned int l, unsigned int n)
{
return t->index[l] + (n * KEYS_PER_NODE);
}
/*
* Return the highest key that you could lookup from the n'th
* node on level l of the btree.
*/
static sector_t high(struct dm_table *t, unsigned int l, unsigned int n)
{
for (; l < t->depth - 1; l++)
n = get_child(n, CHILDREN_PER_NODE - 1);
if (n >= t->counts[l])
return (sector_t) - 1;
return get_node(t, l, n)[KEYS_PER_NODE - 1];
}
/*
* Fills in a level of the btree based on the highs of the level
* below it.
*/
static int setup_btree_index(unsigned int l, struct dm_table *t)
{
unsigned int n, k;
sector_t *node;
for (n = 0U; n < t->counts[l]; n++) {
node = get_node(t, l, n);
for (k = 0U; k < KEYS_PER_NODE; k++)
node[k] = high(t, l + 1, get_child(n, k));
}
return 0;
}
void *dm_vcalloc(unsigned long nmemb, unsigned long elem_size)
{
unsigned long size;
void *addr;
/*
* Check that we're not going to overflow.
*/
if (nmemb > (ULONG_MAX / elem_size))
return NULL;
size = nmemb * elem_size;
addr = vmalloc(size);
if (addr)
memset(addr, 0, size);
return addr;
}
/*
* highs, and targets are managed as dynamic arrays during a
* table load.
*/
static int alloc_targets(struct dm_table *t, unsigned int num)
{
sector_t *n_highs;
struct dm_target *n_targets;
int n = t->num_targets;
/*
* Allocate both the target array and offset array at once.
* Append an empty entry to catch sectors beyond the end of
* the device.
*/
n_highs = (sector_t *) dm_vcalloc(num + 1, sizeof(struct dm_target) +
sizeof(sector_t));
if (!n_highs)
return -ENOMEM;
n_targets = (struct dm_target *) (n_highs + num);
if (n) {
memcpy(n_highs, t->highs, sizeof(*n_highs) * n);
memcpy(n_targets, t->targets, sizeof(*n_targets) * n);
}
memset(n_highs + n, -1, sizeof(*n_highs) * (num - n));
vfree(t->highs);
t->num_allocated = num;
t->highs = n_highs;
t->targets = n_targets;
return 0;
}
int dm_table_create(struct dm_table **result, int mode,
unsigned num_targets, struct mapped_device *md)
{
struct dm_table *t = kzalloc(sizeof(*t), GFP_KERNEL);
if (!t)
return -ENOMEM;
INIT_LIST_HEAD(&t->devices);
atomic_set(&t->holders, 1);
if (!num_targets)
num_targets = KEYS_PER_NODE;
num_targets = dm_round_up(num_targets, KEYS_PER_NODE);
if (alloc_targets(t, num_targets)) {
kfree(t);
t = NULL;
return -ENOMEM;
}
t->mode = mode;
t->md = md;
*result = t;
return 0;
}
int dm_create_error_table(struct dm_table **result, struct mapped_device *md)
{
struct dm_table *t;
sector_t dev_size = 1;
int r;
/*
* Find current size of device.
* Default to 1 sector if inactive.
*/
t = dm_get_table(md);
if (t) {
dev_size = dm_table_get_size(t);
dm_table_put(t);
}
r = dm_table_create(&t, FMODE_READ, 1, md);
if (r)
return r;
r = dm_table_add_target(t, "error", 0, dev_size, NULL);
if (r)
goto out;
r = dm_table_complete(t);
if (r)
goto out;
*result = t;
out:
if (r)
dm_table_put(t);
return r;
}
EXPORT_SYMBOL_GPL(dm_create_error_table);
static void free_devices(struct list_head *devices)
{
struct list_head *tmp, *next;
for (tmp = devices->next; tmp != devices; tmp = next) {
struct dm_dev *dd = list_entry(tmp, struct dm_dev, list);
next = tmp->next;
kfree(dd);
}
}
static void table_destroy(struct dm_table *t)
{
unsigned int i;
/* free the indexes (see dm_table_complete) */
if (t->depth >= 2)
vfree(t->index[t->depth - 2]);
/* free the targets */
for (i = 0; i < t->num_targets; i++) {
struct dm_target *tgt = t->targets + i;
if (tgt->type->dtr)
tgt->type->dtr(tgt);
dm_put_target_type(tgt->type);
}
vfree(t->highs);
/* free the device list */
if (t->devices.next != &t->devices) {
DMWARN("devices still present during destroy: "
"dm_table_remove_device calls missing");
free_devices(&t->devices);
}
kfree(t);
}
void dm_table_get(struct dm_table *t)
{
atomic_inc(&t->holders);
}
void dm_table_put(struct dm_table *t)
{
if (!t)
return;
if (atomic_dec_and_test(&t->holders))
table_destroy(t);
}
/*
* Checks to see if we need to extend highs or targets.
*/
static inline int check_space(struct dm_table *t)
{
if (t->num_targets >= t->num_allocated)
return alloc_targets(t, t->num_allocated * 2);
return 0;
}
/*
* Convert a device path to a dev_t.
*/
static int lookup_device(const char *path, dev_t *dev)
{
int r;
struct nameidata nd;
struct inode *inode;
if ((r = path_lookup(path, LOOKUP_FOLLOW, &nd)))
return r;
inode = nd.dentry->d_inode;
if (!inode) {
r = -ENOENT;
goto out;
}
if (!S_ISBLK(inode->i_mode)) {
r = -ENOTBLK;
goto out;
}
*dev = inode->i_rdev;
out:
path_release(&nd);
return r;
}
/*
* See if we've already got a device in the list.
*/
static struct dm_dev *find_device(struct list_head *l, dev_t dev)
{
struct dm_dev *dd;
list_for_each_entry (dd, l, list)
if (dd->bdev->bd_dev == dev)
return dd;
return NULL;
}
/*
* Open a device so we can use it as a map destination.
*/
static int open_dev(struct dm_dev *d, dev_t dev, struct mapped_device *md)
{
static char *_claim_ptr = "I belong to device-mapper";
struct block_device *bdev;
int r;
BUG_ON(d->bdev);
bdev = open_by_devnum(dev, d->mode);
if (IS_ERR(bdev))
return PTR_ERR(bdev);
r = bd_claim_by_disk(bdev, _claim_ptr, dm_disk(md));
if (r)
blkdev_put(bdev);
else
d->bdev = bdev;
return r;
}
/*
* Close a device that we've been using.
*/
static void close_dev(struct dm_dev *d, struct mapped_device *md)
{
if (!d->bdev)
return;
bd_release_from_disk(d->bdev, dm_disk(md));
blkdev_put(d->bdev);
d->bdev = NULL;
}
/*
* If possible, this checks an area of a destination device is valid.
*/
static int check_device_area(struct dm_dev *dd, sector_t start, sector_t len)
{
sector_t dev_size = dd->bdev->bd_inode->i_size >> SECTOR_SHIFT;
if (!dev_size)
return 1;
return ((start < dev_size) && (len <= (dev_size - start)));
}
/*
* This upgrades the mode on an already open dm_dev. Being
* careful to leave things as they were if we fail to reopen the
* device.
*/
static int upgrade_mode(struct dm_dev *dd, int new_mode, struct mapped_device *md)
{
int r;
struct dm_dev dd_copy;
dev_t dev = dd->bdev->bd_dev;
dd_copy = *dd;
dd->mode |= new_mode;
dd->bdev = NULL;
r = open_dev(dd, dev, md);
if (!r)
close_dev(&dd_copy, md);
else
*dd = dd_copy;
return r;
}
/*
* Add a device to the list, or just increment the usage count if
* it's already present.
*/
static int __table_get_device(struct dm_table *t, struct dm_target *ti,
const char *path, sector_t start, sector_t len,
int mode, struct dm_dev **result)
{
int r;
dev_t dev;
struct dm_dev *dd;
unsigned int major, minor;
BUG_ON(!t);
if (sscanf(path, "%u:%u", &major, &minor) == 2) {
/* Extract the major/minor numbers */
dev = MKDEV(major, minor);
if (MAJOR(dev) != major || MINOR(dev) != minor)
return -EOVERFLOW;
} else {
/* convert the path to a device */
if ((r = lookup_device(path, &dev)))
return r;
}
dd = find_device(&t->devices, dev);
if (!dd) {
dd = kmalloc(sizeof(*dd), GFP_KERNEL);
if (!dd)
return -ENOMEM;
dd->mode = mode;
dd->bdev = NULL;
if ((r = open_dev(dd, dev, t->md))) {
kfree(dd);
return r;
}
format_dev_t(dd->name, dev);
atomic_set(&dd->count, 0);
list_add(&dd->list, &t->devices);
} else if (dd->mode != (mode | dd->mode)) {
r = upgrade_mode(dd, mode, t->md);
if (r)
return r;
}
atomic_inc(&dd->count);
if (!check_device_area(dd, start, len)) {
DMWARN("device %s too small for target", path);
dm_put_device(ti, dd);
return -EINVAL;
}
*result = dd;
return 0;
}
void dm_set_device_limits(struct dm_target *ti, struct block_device *bdev)
{
struct request_queue *q = bdev_get_queue(bdev);
struct io_restrictions *rs = &ti->limits;
/*
* Combine the device limits low.
*
* FIXME: if we move an io_restriction struct
* into q this would just be a call to
* combine_restrictions_low()
*/
rs->max_sectors =
min_not_zero(rs->max_sectors, q->max_sectors);
/* FIXME: Device-Mapper on top of RAID-0 breaks because DM
* currently doesn't honor MD's merge_bvec_fn routine.
* In this case, we'll force DM to use PAGE_SIZE or
* smaller I/O, just to be safe. A better fix is in the
* works, but add this for the time being so it will at
* least operate correctly.
*/
if (q->merge_bvec_fn)
rs->max_sectors =
min_not_zero(rs->max_sectors,
(unsigned int) (PAGE_SIZE >> 9));
rs->max_phys_segments =
min_not_zero(rs->max_phys_segments,
q->max_phys_segments);
rs->max_hw_segments =
min_not_zero(rs->max_hw_segments, q->max_hw_segments);
rs->hardsect_size = max(rs->hardsect_size, q->hardsect_size);
rs->max_segment_size =
min_not_zero(rs->max_segment_size, q->max_segment_size);
rs->max_hw_sectors =
min_not_zero(rs->max_hw_sectors, q->max_hw_sectors);
rs->seg_boundary_mask =
min_not_zero(rs->seg_boundary_mask,
q->seg_boundary_mask);
rs->bounce_pfn = min_not_zero(rs->bounce_pfn, q->bounce_pfn);
rs->no_cluster |= !test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags);
}
EXPORT_SYMBOL_GPL(dm_set_device_limits);
int dm_get_device(struct dm_target *ti, const char *path, sector_t start,
sector_t len, int mode, struct dm_dev **result)
{
int r = __table_get_device(ti->table, ti, path,
start, len, mode, result);
if (!r)
dm_set_device_limits(ti, (*result)->bdev);
return r;
}
/*
* Decrement a devices use count and remove it if necessary.
*/
void dm_put_device(struct dm_target *ti, struct dm_dev *dd)
{
if (atomic_dec_and_test(&dd->count)) {
close_dev(dd, ti->table->md);
list_del(&dd->list);
kfree(dd);
}
}
/*
* Checks to see if the target joins onto the end of the table.
*/
static int adjoin(struct dm_table *table, struct dm_target *ti)
{
struct dm_target *prev;
if (!table->num_targets)
return !ti->begin;
prev = &table->targets[table->num_targets - 1];
return (ti->begin == (prev->begin + prev->len));
}
/*
* Used to dynamically allocate the arg array.
*/
static char **realloc_argv(unsigned *array_size, char **old_argv)
{
char **argv;
unsigned new_size;
new_size = *array_size ? *array_size * 2 : 64;
argv = kmalloc(new_size * sizeof(*argv), GFP_KERNEL);
if (argv) {
memcpy(argv, old_argv, *array_size * sizeof(*argv));
*array_size = new_size;
}
kfree(old_argv);
return argv;
}
/*
* Destructively splits up the argument list to pass to ctr.
*/
int dm_split_args(int *argc, char ***argvp, char *input)
{
char *start, *end = input, *out, **argv = NULL;
unsigned array_size = 0;
*argc = 0;
if (!input) {
*argvp = NULL;
return 0;
}
argv = realloc_argv(&array_size, argv);
if (!argv)
return -ENOMEM;
while (1) {
start = end;
/* Skip whitespace */
while (*start && isspace(*start))
start++;
if (!*start)
break; /* success, we hit the end */
/* 'out' is used to remove any back-quotes */
end = out = start;
while (*end) {
/* Everything apart from '\0' can be quoted */
if (*end == '\\' && *(end + 1)) {
*out++ = *(end + 1);
end += 2;
continue;
}
if (isspace(*end))
break; /* end of token */
*out++ = *end++;
}
/* have we already filled the array ? */
if ((*argc + 1) > array_size) {
argv = realloc_argv(&array_size, argv);
if (!argv)
return -ENOMEM;
}
/* we know this is whitespace */
if (*end)
end++;
/* terminate the string and put it in the array */
*out = '\0';
argv[*argc] = start;
(*argc)++;
}
*argvp = argv;
return 0;
}
static void check_for_valid_limits(struct io_restrictions *rs)
{
if (!rs->max_sectors)
rs->max_sectors = SAFE_MAX_SECTORS;
if (!rs->max_hw_sectors)
rs->max_hw_sectors = SAFE_MAX_SECTORS;
if (!rs->max_phys_segments)
rs->max_phys_segments = MAX_PHYS_SEGMENTS;
if (!rs->max_hw_segments)
rs->max_hw_segments = MAX_HW_SEGMENTS;
if (!rs->hardsect_size)
rs->hardsect_size = 1 << SECTOR_SHIFT;
if (!rs->max_segment_size)
rs->max_segment_size = MAX_SEGMENT_SIZE;
if (!rs->seg_boundary_mask)
rs->seg_boundary_mask = -1;
if (!rs->bounce_pfn)
rs->bounce_pfn = -1;
}
int dm_table_add_target(struct dm_table *t, const char *type,
sector_t start, sector_t len, char *params)
{
int r = -EINVAL, argc;
char **argv;
struct dm_target *tgt;
if ((r = check_space(t)))
return r;
tgt = t->targets + t->num_targets;
memset(tgt, 0, sizeof(*tgt));
if (!len) {
DMERR("%s: zero-length target", dm_device_name(t->md));
return -EINVAL;
}
tgt->type = dm_get_target_type(type);
if (!tgt->type) {
DMERR("%s: %s: unknown target type", dm_device_name(t->md),
type);
return -EINVAL;
}
tgt->table = t;
tgt->begin = start;
tgt->len = len;
tgt->error = "Unknown error";
/*
* Does this target adjoin the previous one ?
*/
if (!adjoin(t, tgt)) {
tgt->error = "Gap in table";
r = -EINVAL;
goto bad;
}
r = dm_split_args(&argc, &argv, params);
if (r) {
tgt->error = "couldn't split parameters (insufficient memory)";
goto bad;
}
r = tgt->type->ctr(tgt, argc, argv);
kfree(argv);
if (r)
goto bad;
t->highs[t->num_targets++] = tgt->begin + tgt->len - 1;
/* FIXME: the plan is to combine high here and then have
* the merge fn apply the target level restrictions. */
combine_restrictions_low(&t->limits, &tgt->limits);
return 0;
bad:
DMERR("%s: %s: %s", dm_device_name(t->md), type, tgt->error);
dm_put_target_type(tgt->type);
return r;
}
static int setup_indexes(struct dm_table *t)
{
int i;
unsigned int total = 0;
sector_t *indexes;
/* allocate the space for *all* the indexes */
for (i = t->depth - 2; i >= 0; i--) {
t->counts[i] = dm_div_up(t->counts[i + 1], CHILDREN_PER_NODE);
total += t->counts[i];
}
indexes = (sector_t *) dm_vcalloc(total, (unsigned long) NODE_SIZE);
if (!indexes)
return -ENOMEM;
/* set up internal nodes, bottom-up */
for (i = t->depth - 2, total = 0; i >= 0; i--) {
t->index[i] = indexes;
indexes += (KEYS_PER_NODE * t->counts[i]);
setup_btree_index(i, t);
}
return 0;
}
/*
* Builds the btree to index the map.
*/
int dm_table_complete(struct dm_table *t)
{
int r = 0;
unsigned int leaf_nodes;
check_for_valid_limits(&t->limits);
/* how many indexes will the btree have ? */
leaf_nodes = dm_div_up(t->num_targets, KEYS_PER_NODE);
t->depth = 1 + int_log(leaf_nodes, CHILDREN_PER_NODE);
/* leaf layer has already been set up */
t->counts[t->depth - 1] = leaf_nodes;
t->index[t->depth - 1] = t->highs;
if (t->depth >= 2)
r = setup_indexes(t);
return r;
}
static DEFINE_MUTEX(_event_lock);
void dm_table_event_callback(struct dm_table *t,
void (*fn)(void *), void *context)
{
mutex_lock(&_event_lock);
t->event_fn = fn;
t->event_context = context;
mutex_unlock(&_event_lock);
}
void dm_table_event(struct dm_table *t)
{
/*
* You can no longer call dm_table_event() from interrupt
* context, use a bottom half instead.
*/
BUG_ON(in_interrupt());
mutex_lock(&_event_lock);
if (t->event_fn)
t->event_fn(t->event_context);
mutex_unlock(&_event_lock);
}
sector_t dm_table_get_size(struct dm_table *t)
{
return t->num_targets ? (t->highs[t->num_targets - 1] + 1) : 0;
}
struct dm_target *dm_table_get_target(struct dm_table *t, unsigned int index)
{
if (index >= t->num_targets)
return NULL;
return t->targets + index;
}
/*
* Search the btree for the correct target.
*
* Caller should check returned pointer with dm_target_is_valid()
* to trap I/O beyond end of device.
*/
struct dm_target *dm_table_find_target(struct dm_table *t, sector_t sector)
{
unsigned int l, n = 0, k = 0;
sector_t *node;
for (l = 0; l < t->depth; l++) {
n = get_child(n, k);
node = get_node(t, l, n);
for (k = 0; k < KEYS_PER_NODE; k++)
if (node[k] >= sector)
break;
}
return &t->targets[(KEYS_PER_NODE * n) + k];
}
void dm_table_set_restrictions(struct dm_table *t, struct request_queue *q)
{
/*
* Make sure we obey the optimistic sub devices
* restrictions.
*/
blk_queue_max_sectors(q, t->limits.max_sectors);
q->max_phys_segments = t->limits.max_phys_segments;
q->max_hw_segments = t->limits.max_hw_segments;
q->hardsect_size = t->limits.hardsect_size;
q->max_segment_size = t->limits.max_segment_size;
q->max_hw_sectors = t->limits.max_hw_sectors;
q->seg_boundary_mask = t->limits.seg_boundary_mask;
q->bounce_pfn = t->limits.bounce_pfn;
if (t->limits.no_cluster)
q->queue_flags &= ~(1 << QUEUE_FLAG_CLUSTER);
else
q->queue_flags |= (1 << QUEUE_FLAG_CLUSTER);
}
unsigned int dm_table_get_num_targets(struct dm_table *t)
{
return t->num_targets;
}
struct list_head *dm_table_get_devices(struct dm_table *t)
{
return &t->devices;
}
int dm_table_get_mode(struct dm_table *t)
{
return t->mode;
}
static void suspend_targets(struct dm_table *t, unsigned postsuspend)
{
int i = t->num_targets;
struct dm_target *ti = t->targets;
while (i--) {
if (postsuspend) {
if (ti->type->postsuspend)
ti->type->postsuspend(ti);
} else if (ti->type->presuspend)
ti->type->presuspend(ti);
ti++;
}
}
void dm_table_presuspend_targets(struct dm_table *t)
{
if (!t)
return;
return suspend_targets(t, 0);
}
void dm_table_postsuspend_targets(struct dm_table *t)
{
if (!t)
return;
return suspend_targets(t, 1);
}
int dm_table_resume_targets(struct dm_table *t)
{
int i, r = 0;
for (i = 0; i < t->num_targets; i++) {
struct dm_target *ti = t->targets + i;
if (!ti->type->preresume)
continue;
r = ti->type->preresume(ti);
if (r)
return r;
}
for (i = 0; i < t->num_targets; i++) {
struct dm_target *ti = t->targets + i;
if (ti->type->resume)
ti->type->resume(ti);
}
return 0;
}
int dm_table_any_congested(struct dm_table *t, int bdi_bits)
{
struct list_head *d, *devices;
int r = 0;
devices = dm_table_get_devices(t);
for (d = devices->next; d != devices; d = d->next) {
struct dm_dev *dd = list_entry(d, struct dm_dev, list);
struct request_queue *q = bdev_get_queue(dd->bdev);
r |= bdi_congested(&q->backing_dev_info, bdi_bits);
}
return r;
}
void dm_table_unplug_all(struct dm_table *t)
{
struct list_head *d, *devices = dm_table_get_devices(t);
for (d = devices->next; d != devices; d = d->next) {
struct dm_dev *dd = list_entry(d, struct dm_dev, list);
struct request_queue *q = bdev_get_queue(dd->bdev);
blk_unplug(q);
}
}
struct mapped_device *dm_table_get_md(struct dm_table *t)
{
dm_get(t->md);
return t->md;
}
EXPORT_SYMBOL(dm_vcalloc);
EXPORT_SYMBOL(dm_get_device);
EXPORT_SYMBOL(dm_put_device);
EXPORT_SYMBOL(dm_table_event);
EXPORT_SYMBOL(dm_table_get_size);
EXPORT_SYMBOL(dm_table_get_mode);
EXPORT_SYMBOL(dm_table_get_md);
EXPORT_SYMBOL(dm_table_put);
EXPORT_SYMBOL(dm_table_get);
EXPORT_SYMBOL(dm_table_unplug_all);
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