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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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