dm-table.c

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/*
 * Copyright (C) 2001 Sistina Software (UK) Limited.
 * Copyright (C) 2004-2008 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/string.h>
#include <linux/slab.h>
#include <linux/interrupt.h>
#include <linux/mutex.h>
#include <linux/delay.h>
#include <linux/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)

/*
 * The table has always exactly one reference from either mapped_device->map
 * or hash_cell->new_map. This reference is not counted in table->holders.
 * A pair of dm_create_table/dm_destroy_table functions is used for table
 * creation/destruction.
 *
 * Temporary references from the other code increase table->holders. A pair
 * of dm_table_get/dm_table_put functions is used to manipulate it.
 *
 * When the table is about to be destroyed, we wait for table->holders to
 * drop to zero.
 */

struct dm_table {
    struct mapped_device *md;
    atomic_t holders;
    unsigned type;

    /* 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;

    struct target_type *immutable_target_type;
    unsigned integrity_supported:1;
    unsigned singleton:1;

    /*
     * Indicates the rw permissions for the new logical
     * device.  This should be a combination of FMODE_READ
     * and FMODE_WRITE.
     */
    fmode_t mode;

    /* a list of devices used by this table */
    struct list_head devices;

    /* events get handed up using this callback */
    void (*event_fn)(void *);
    void *event_context;

    struct dm_md_mempools *mempools;

    struct list_head target_callbacks;
};

/*
 * 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;
}

/*
 * 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 = vzalloc(size);

    return addr;
}
EXPORT_SYMBOL(dm_vcalloc);

/*
 * 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, fmode_t 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);
    INIT_LIST_HEAD(&t->target_callbacks);
    atomic_set(&t->holders, 0);

    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;
}

static void free_devices(struct list_head *devices)
{
    struct list_head *tmp, *next;

    list_for_each_safe(tmp, next, devices) {
        struct dm_dev_internal *dd =
            list_entry(tmp, struct dm_dev_internal, list);
        DMWARN("dm_table_destroy: dm_put_device call missing for %s",
               dd->dm_dev.name);
        kfree(dd);
    }
}

void dm_table_destroy(struct dm_table *t)
{
    unsigned int i;

    if (!t)
        return;

    while (atomic_read(&t->holders))
        msleep(1);
    smp_mb();

    /* free the indexes */
    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 */
    free_devices(&t->devices);

    dm_free_md_mempools(t->mempools);

    kfree(t);
}

void dm_table_get(struct dm_table *t)
{
    atomic_inc(&t->holders);
}
EXPORT_SYMBOL(dm_table_get);

void dm_table_put(struct dm_table *t)
{
    if (!t)
        return;

    smp_mb__before_atomic_dec();
    atomic_dec(&t->holders);
}
EXPORT_SYMBOL(dm_table_put);

/*
 * 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;
}

/*
 * See if we've already got a device in the list.
 */
static struct dm_dev_internal *find_device(struct list_head *l, dev_t dev)
{
    struct dm_dev_internal *dd;

    list_for_each_entry (dd, l, list)
        if (dd->dm_dev.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_internal *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->dm_dev.bdev);

    bdev = blkdev_get_by_dev(dev, d->dm_dev.mode | FMODE_EXCL, _claim_ptr);
    if (IS_ERR(bdev))
        return PTR_ERR(bdev);

    r = bd_link_disk_holder(bdev, dm_disk(md));
    if (r) {
        blkdev_put(bdev, d->dm_dev.mode | FMODE_EXCL);
        return r;
    }

    d->dm_dev.bdev = bdev;
    return 0;
}

/*
 * Close a device that we've been using.
 */
static void close_dev(struct dm_dev_internal *d, struct mapped_device *md)
{
    if (!d->dm_dev.bdev)
        return;

    bd_unlink_disk_holder(d->dm_dev.bdev, dm_disk(md));
    blkdev_put(d->dm_dev.bdev, d->dm_dev.mode | FMODE_EXCL);
    d->dm_dev.bdev = NULL;
}

/*
 * If possible, this checks an area of a destination device is invalid.
 */
static int device_area_is_invalid(struct dm_target *ti, struct dm_dev *dev,
                  sector_t start, sector_t len, void *data)
{
    struct request_queue *q;
    struct queue_limits *limits = data;
    struct block_device *bdev = dev->bdev;
    sector_t dev_size =
        i_size_read(bdev->bd_inode) >> SECTOR_SHIFT;
    unsigned short logical_block_size_sectors =
        limits->logical_block_size >> SECTOR_SHIFT;
    char b[BDEVNAME_SIZE];

    /*
     * Some devices exist without request functions,
     * such as loop devices not yet bound to backing files.
     * Forbid the use of such devices.
     */
    q = bdev_get_queue(bdev);
    if (!q || !q->make_request_fn) {
        DMWARN("%s: %s is not yet initialised: "
               "start=%llu, len=%llu, dev_size=%llu",
               dm_device_name(ti->table->md), bdevname(bdev, b),
               (unsigned long long)start,
               (unsigned long long)len,
               (unsigned long long)dev_size);
        return 1;
    }

    if (!dev_size)
        return 0;

    if ((start >= dev_size) || (start + len > dev_size)) {
        DMWARN("%s: %s too small for target: "
               "start=%llu, len=%llu, dev_size=%llu",
               dm_device_name(ti->table->md), bdevname(bdev, b),
               (unsigned long long)start,
               (unsigned long long)len,
               (unsigned long long)dev_size);
        return 1;
    }

    if (logical_block_size_sectors <= 1)
        return 0;

    if (start & (logical_block_size_sectors - 1)) {
        DMWARN("%s: start=%llu not aligned to h/w "
               "logical block size %u of %s",
               dm_device_name(ti->table->md),
               (unsigned long long)start,
               limits->logical_block_size, bdevname(bdev, b));
        return 1;
    }

    if (len & (logical_block_size_sectors - 1)) {
        DMWARN("%s: len=%llu not aligned to h/w "
               "logical block size %u of %s",
               dm_device_name(ti->table->md),
               (unsigned long long)len,
               limits->logical_block_size, bdevname(bdev, b));
        return 1;
    }

    return 0;
}

/*
 * 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 and not to touch the existing bdev field in case
 * it is accessed concurrently inside dm_table_any_congested().
 */
static int upgrade_mode(struct dm_dev_internal *dd, fmode_t new_mode,
            struct mapped_device *md)
{
    int r;
    struct dm_dev_internal dd_new, dd_old;

    dd_new = dd_old = *dd;

    dd_new.dm_dev.mode |= new_mode;
    dd_new.dm_dev.bdev = NULL;

    r = open_dev(&dd_new, dd->dm_dev.bdev->bd_dev, md);
    if (r)
        return r;

    dd->dm_dev.mode |= new_mode;
    close_dev(&dd_old, md);

    return 0;
}

/*
 * Add a device to the list, or just increment the usage count if
 * it's already present.
 */
int dm_get_device(struct dm_target *ti, const char *path, fmode_t mode,
          struct dm_dev **result)
{
    int r;
    dev_t uninitialized_var(dev);
    struct dm_dev_internal *dd;
    unsigned int major, minor;
    struct dm_table *t = ti->table;
    char dummy;

    BUG_ON(!t);

    if (sscanf(path, "%u:%u%c", &major, &minor, &dummy) == 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 */
        struct block_device *bdev = lookup_bdev(path);

        if (IS_ERR(bdev))
            return PTR_ERR(bdev);
        dev = bdev->bd_dev;
        bdput(bdev);
    }

    dd = find_device(&t->devices, dev);
    if (!dd) {
        dd = kmalloc(sizeof(*dd), GFP_KERNEL);
        if (!dd)
            return -ENOMEM;

        dd->dm_dev.mode = mode;
        dd->dm_dev.bdev = NULL;

        if ((r = open_dev(dd, dev, t->md))) {
            kfree(dd);
            return r;
        }

        format_dev_t(dd->dm_dev.name, dev);

        atomic_set(&dd->count, 0);
        list_add(&dd->list, &t->devices);

    } else if (dd->dm_dev.mode != (mode | dd->dm_dev.mode)) {
        r = upgrade_mode(dd, mode, t->md);
        if (r)
            return r;
    }
    atomic_inc(&dd->count);

    *result = &dd->dm_dev;
    return 0;
}
EXPORT_SYMBOL(dm_get_device);

int dm_set_device_limits(struct dm_target *ti, struct dm_dev *dev,
             sector_t start, sector_t len, void *data)
{
    struct queue_limits *limits = data;
    struct block_device *bdev = dev->bdev;
    struct request_queue *q = bdev_get_queue(bdev);
    char b[BDEVNAME_SIZE];

    if (unlikely(!q)) {
        DMWARN("%s: Cannot set limits for nonexistent device %s",
               dm_device_name(ti->table->md), bdevname(bdev, b));
        return 0;
    }

    if (bdev_stack_limits(limits, bdev, start) < 0)
        DMWARN("%s: adding target device %s caused an alignment inconsistency: "
               "physical_block_size=%u, logical_block_size=%u, "
               "alignment_offset=%u, start=%llu",
               dm_device_name(ti->table->md), bdevname(bdev, b),
               q->limits.physical_block_size,
               q->limits.logical_block_size,
               q->limits.alignment_offset,
               (unsigned long long) start << SECTOR_SHIFT);

    /*
     * Check if merge fn is supported.
     * If not we'll force DM to use PAGE_SIZE or
     * smaller I/O, just to be safe.
     */
    if (dm_queue_merge_is_compulsory(q) && !ti->type->merge)
        blk_limits_max_hw_sectors(limits,
                      (unsigned int) (PAGE_SIZE >> 9));
    return 0;
}
EXPORT_SYMBOL_GPL(dm_set_device_limits);

/*
 * Decrement a device's use count and remove it if necessary.
 */
void dm_put_device(struct dm_target *ti, struct dm_dev *d)
{
    struct dm_dev_internal *dd = container_of(d, struct dm_dev_internal,
                          dm_dev);

    if (atomic_dec_and_test(&dd->count)) {
        close_dev(dd, ti->table->md);
        list_del(&dd->list);
        kfree(dd);
    }
}
EXPORT_SYMBOL(dm_put_device);

/*
 * 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) {
        /* Skip whitespace */
        start = skip_spaces(end);

        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;
}

/*
 * Impose necessary and sufficient conditions on a devices's table such
 * that any incoming bio which respects its logical_block_size can be
 * processed successfully.  If it falls across the boundary between
 * two or more targets, the size of each piece it gets split into must
 * be compatible with the logical_block_size of the target processing it.
 */
static int validate_hardware_logical_block_alignment(struct dm_table *table,
                         struct queue_limits *limits)
{
    /*
     * This function uses arithmetic modulo the logical_block_size
     * (in units of 512-byte sectors).
     */
    unsigned short device_logical_block_size_sects =
        limits->logical_block_size >> SECTOR_SHIFT;

    /*
     * Offset of the start of the next table entry, mod logical_block_size.
     */
    unsigned short next_target_start = 0;

    /*
     * Given an aligned bio that extends beyond the end of a
     * target, how many sectors must the next target handle?
     */
    unsigned short remaining = 0;

    struct dm_target *uninitialized_var(ti);
    struct queue_limits ti_limits;
    unsigned i = 0;

    /*
     * Check each entry in the table in turn.
     */
    while (i < dm_table_get_num_targets(table)) {
        ti = dm_table_get_target(table, i++);

        blk_set_stacking_limits(&ti_limits);

        /* combine all target devices' limits */
        if (ti->type->iterate_devices)
            ti->type->iterate_devices(ti, dm_set_device_limits,
                          &ti_limits);

        /*
         * If the remaining sectors fall entirely within this
         * table entry are they compatible with its logical_block_size?
         */
        if (remaining < ti->len &&
            remaining & ((ti_limits.logical_block_size >>
                  SECTOR_SHIFT) - 1))
            break;  /* Error */

        next_target_start =
            (unsigned short) ((next_target_start + ti->len) &
                      (device_logical_block_size_sects - 1));
        remaining = next_target_start ?
            device_logical_block_size_sects - next_target_start : 0;
    }

    if (remaining) {
        DMWARN("%s: table line %u (start sect %llu len %llu) "
               "not aligned to h/w logical block size %u",
               dm_device_name(table->md), i,
               (unsigned long long) ti->begin,
               (unsigned long long) ti->len,
               limits->logical_block_size);
        return -EINVAL;
    }

    return 0;
}

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 (t->singleton) {
        DMERR("%s: target type %s must appear alone in table",
              dm_device_name(t->md), t->targets->type->name);
        return -EINVAL;
    }

    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;
    }

    if (dm_target_needs_singleton(tgt->type)) {
        if (t->num_targets) {
            DMERR("%s: target type %s must appear alone in table",
                  dm_device_name(t->md), type);
            return -EINVAL;
        }
        t->singleton = 1;
    }

    if (dm_target_always_writeable(tgt->type) && !(t->mode & FMODE_WRITE)) {
        DMERR("%s: target type %s may not be included in read-only tables",
              dm_device_name(t->md), type);
        return -EINVAL;
    }

    if (t->immutable_target_type) {
        if (t->immutable_target_type != tgt->type) {
            DMERR("%s: immutable target type %s cannot be mixed with other target types",
                  dm_device_name(t->md), t->immutable_target_type->name);
            return -EINVAL;
        }
    } else if (dm_target_is_immutable(tgt->type)) {
        if (t->num_targets) {
            DMERR("%s: immutable target type %s cannot be mixed with other target types",
                  dm_device_name(t->md), tgt->type->name);
            return -EINVAL;
        }
        t->immutable_target_type = tgt->type;
    }

    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;

    if (!tgt->num_discard_requests && tgt->discards_supported)
        DMWARN("%s: %s: ignoring discards_supported because num_discard_requests is zero.",
               dm_device_name(t->md), type);

    return 0;

 bad:
    DMERR("%s: %s: %s", dm_device_name(t->md), type, tgt->error);
    dm_put_target_type(tgt->type);
    return r;
}

/*
 * Target argument parsing helpers.
 */
static int validate_next_arg(struct dm_arg *arg, struct dm_arg_set *arg_set,
                 unsigned *value, char **error, unsigned grouped)
{
    const char *arg_str = dm_shift_arg(arg_set);
    char dummy;

    if (!arg_str ||
        (sscanf(arg_str, "%u%c", value, &dummy) != 1) ||
        (*value < arg->min) ||
        (*value > arg->max) ||
        (grouped && arg_set->argc < *value)) {
        *error = arg->error;
        return -EINVAL;
    }

    return 0;
}

int dm_read_arg(struct dm_arg *arg, struct dm_arg_set *arg_set,
        unsigned *value, char **error)
{
    return validate_next_arg(arg, arg_set, value, error, 0);
}
EXPORT_SYMBOL(dm_read_arg);

int dm_read_arg_group(struct dm_arg *arg, struct dm_arg_set *arg_set,
              unsigned *value, char **error)
{
    return validate_next_arg(arg, arg_set, value, error, 1);
}
EXPORT_SYMBOL(dm_read_arg_group);

const char *dm_shift_arg(struct dm_arg_set *as)
{
    char *r;

    if (as->argc) {
        as->argc--;
        r = *as->argv;
        as->argv++;
        return r;
    }

    return NULL;
}
EXPORT_SYMBOL(dm_shift_arg);

void dm_consume_args(struct dm_arg_set *as, unsigned num_args)
{
    BUG_ON(as->argc < num_args);
    as->argc -= num_args;
    as->argv += num_args;
}
EXPORT_SYMBOL(dm_consume_args);

static int dm_table_set_type(struct dm_table *t)
{
    unsigned i;
    unsigned bio_based = 0, request_based = 0;
    struct dm_target *tgt;
    struct dm_dev_internal *dd;
    struct list_head *devices;

    for (i = 0; i < t->num_targets; i++) {
        tgt = t->targets + i;
        if (dm_target_request_based(tgt))
            request_based = 1;
        else
            bio_based = 1;

        if (bio_based && request_based) {
            DMWARN("Inconsistent table: different target types"
                   " can't be mixed up");
            return -EINVAL;
        }
    }

    if (bio_based) {
        /* We must use this table as bio-based */
        t->type = DM_TYPE_BIO_BASED;
        return 0;
    }

    BUG_ON(!request_based); /* No targets in this table */

    /* Non-request-stackable devices can't be used for request-based dm */
    devices = dm_table_get_devices(t);
    list_for_each_entry(dd, devices, list) {
        if (!blk_queue_stackable(bdev_get_queue(dd->dm_dev.bdev))) {
            DMWARN("table load rejected: including"
                   " non-request-stackable devices");
            return -EINVAL;
        }
    }

    /*
     * Request-based dm supports only tables that have a single target now.
     * To support multiple targets, request splitting support is needed,
     * and that needs lots of changes in the block-layer.
     * (e.g. request completion process for partial completion.)
     */
    if (t->num_targets > 1) {
        DMWARN("Request-based dm doesn't support multiple targets yet");
        return -EINVAL;
    }

    t->type = DM_TYPE_REQUEST_BASED;

    return 0;
}

unsigned dm_table_get_type(struct dm_table *t)
{
    return t->type;
}

struct target_type *dm_table_get_immutable_target_type(struct dm_table *t)
{
    return t->immutable_target_type;
}

bool dm_table_request_based(struct dm_table *t)
{
    return dm_table_get_type(t) == DM_TYPE_REQUEST_BASED;
}

int dm_table_alloc_md_mempools(struct dm_table *t)
{
    unsigned type = dm_table_get_type(t);

    if (unlikely(type == DM_TYPE_NONE)) {
        DMWARN("no table type is set, can't allocate mempools");
        return -EINVAL;
    }

    t->mempools = dm_alloc_md_mempools(type, t->integrity_supported);
    if (!t->mempools)
        return -ENOMEM;

    return 0;
}

void dm_table_free_md_mempools(struct dm_table *t)
{
    dm_free_md_mempools(t->mempools);
    t->mempools = NULL;
}

struct dm_md_mempools *dm_table_get_md_mempools(struct dm_table *t)
{
    return t->mempools;
}

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; 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.
 */
static int dm_table_build_index(struct dm_table *t)
{
    int r = 0;
    unsigned int leaf_nodes;

    /* 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;
}

/*
 * Get a disk whose integrity profile reflects the table's profile.
 * If %match_all is true, all devices' profiles must match.
 * If %match_all is false, all devices must at least have an
 * allocated integrity profile; but uninitialized is ok.
 * Returns NULL if integrity support was inconsistent or unavailable.
 */
static struct gendisk * dm_table_get_integrity_disk(struct dm_table *t,
                            bool match_all)
{
    struct list_head *devices = dm_table_get_devices(t);
    struct dm_dev_internal *dd = NULL;
    struct gendisk *prev_disk = NULL, *template_disk = NULL;

    list_for_each_entry(dd, devices, list) {
        template_disk = dd->dm_dev.bdev->bd_disk;
        if (!blk_get_integrity(template_disk))
            goto no_integrity;
        if (!match_all && !blk_integrity_is_initialized(template_disk))
            continue; /* skip uninitialized profiles */
        else if (prev_disk &&
             blk_integrity_compare(prev_disk, template_disk) < 0)
            goto no_integrity;
        prev_disk = template_disk;
    }

    return template_disk;

no_integrity:
    if (prev_disk)
        DMWARN("%s: integrity not set: %s and %s profile mismatch",
               dm_device_name(t->md),
               prev_disk->disk_name,
               template_disk->disk_name);
    return NULL;
}

/*
 * Register the mapped device for blk_integrity support if
 * the underlying devices have an integrity profile.  But all devices
 * may not have matching profiles (checking all devices isn't reliable
 * during table load because this table may use other DM device(s) which
 * must be resumed before they will have an initialized integity profile).
 * Stacked DM devices force a 2 stage integrity profile validation:
 * 1 - during load, validate all initialized integrity profiles match
 * 2 - during resume, validate all integrity profiles match
 */
static int dm_table_prealloc_integrity(struct dm_table *t, struct mapped_device *md)
{
    struct gendisk *template_disk = NULL;

    template_disk = dm_table_get_integrity_disk(t, false);
    if (!template_disk)
        return 0;

    if (!blk_integrity_is_initialized(dm_disk(md))) {
        t->integrity_supported = 1;
        return blk_integrity_register(dm_disk(md), NULL);
    }

    /*
     * If DM device already has an initalized integrity
     * profile the new profile should not conflict.
     */
    if (blk_integrity_is_initialized(template_disk) &&
        blk_integrity_compare(dm_disk(md), template_disk) < 0) {
        DMWARN("%s: conflict with existing integrity profile: "
               "%s profile mismatch",
               dm_device_name(t->md),
               template_disk->disk_name);
        return 1;
    }

    /* Preserve existing initialized integrity profile */
    t->integrity_supported = 1;
    return 0;
}

/*
 * Prepares the table for use by building the indices,
 * setting the type, and allocating mempools.
 */
int dm_table_complete(struct dm_table *t)
{
    int r;

    r = dm_table_set_type(t);
    if (r) {
        DMERR("unable to set table type");
        return r;
    }

    r = dm_table_build_index(t);
    if (r) {
        DMERR("unable to build btrees");
        return r;
    }

    r = dm_table_prealloc_integrity(t, t->md);
    if (r) {
        DMERR("could not register integrity profile.");
        return r;
    }

    r = dm_table_alloc_md_mempools(t);
    if (r)
        DMERR("unable to allocate mempools");

    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);
}
EXPORT_SYMBOL(dm_table_event);

sector_t dm_table_get_size(struct dm_table *t)
{
    return t->num_targets ? (t->highs[t->num_targets - 1] + 1) : 0;
}
EXPORT_SYMBOL(dm_table_get_size);

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];
}

static int count_device(struct dm_target *ti, struct dm_dev *dev,
            sector_t start, sector_t len, void *data)
{
    unsigned *num_devices = data;

    (*num_devices)++;

    return 0;
}

/*
 * Check whether a table has no data devices attached using each
 * target's iterate_devices method.
 * Returns false if the result is unknown because a target doesn't
 * support iterate_devices.
 */
bool dm_table_has_no_data_devices(struct dm_table *table)
{
    struct dm_target *uninitialized_var(ti);
    unsigned i = 0, num_devices = 0;

    while (i < dm_table_get_num_targets(table)) {
        ti = dm_table_get_target(table, i++);

        if (!ti->type->iterate_devices)
            return false;

        ti->type->iterate_devices(ti, count_device, &num_devices);
        if (num_devices)
            return false;
    }

    return true;
}

/*
 * Establish the new table's queue_limits and validate them.
 */
int dm_calculate_queue_limits(struct dm_table *table,
                  struct queue_limits *limits)
{
    struct dm_target *uninitialized_var(ti);
    struct queue_limits ti_limits;
    unsigned i = 0;

    blk_set_stacking_limits(limits);

    while (i < dm_table_get_num_targets(table)) {
        blk_set_stacking_limits(&ti_limits);

        ti = dm_table_get_target(table, i++);

        if (!ti->type->iterate_devices)
            goto combine_limits;

        /*
         * Combine queue limits of all the devices this target uses.
         */
        ti->type->iterate_devices(ti, dm_set_device_limits,
                      &ti_limits);

        /* Set I/O hints portion of queue limits */
        if (ti->type->io_hints)
            ti->type->io_hints(ti, &ti_limits);

        /*
         * Check each device area is consistent with the target's
         * overall queue limits.
         */
        if (ti->type->iterate_devices(ti, device_area_is_invalid,
                          &ti_limits))
            return -EINVAL;

combine_limits:
        /*
         * Merge this target's queue limits into the overall limits
         * for the table.
         */
        if (blk_stack_limits(limits, &ti_limits, 0) < 0)
            DMWARN("%s: adding target device "
                   "(start sect %llu len %llu) "
                   "caused an alignment inconsistency",
                   dm_device_name(table->md),
                   (unsigned long long) ti->begin,
                   (unsigned long long) ti->len);
    }

    return validate_hardware_logical_block_alignment(table, limits);
}

/*
 * Set the integrity profile for this device if all devices used have
 * matching profiles.  We're quite deep in the resume path but still
 * don't know if all devices (particularly DM devices this device
 * may be stacked on) have matching profiles.  Even if the profiles
 * don't match we have no way to fail (to resume) at this point.
 */
static void dm_table_set_integrity(struct dm_table *t)
{
    struct gendisk *template_disk = NULL;

    if (!blk_get_integrity(dm_disk(t->md)))
        return;

    template_disk = dm_table_get_integrity_disk(t, true);
    if (template_disk)
        blk_integrity_register(dm_disk(t->md),
                       blk_get_integrity(template_disk));
    else if (blk_integrity_is_initialized(dm_disk(t->md)))
        DMWARN("%s: device no longer has a valid integrity profile",
               dm_device_name(t->md));
    else
        DMWARN("%s: unable to establish an integrity profile",
               dm_device_name(t->md));
}

static int device_flush_capable(struct dm_target *ti, struct dm_dev *dev,
                sector_t start, sector_t len, void *data)
{
    unsigned flush = (*(unsigned *)data);
    struct request_queue *q = bdev_get_queue(dev->bdev);

    return q && (q->flush_flags & flush);
}

static bool dm_table_supports_flush(struct dm_table *t, unsigned flush)
{
    struct dm_target *ti;
    unsigned i = 0;

    /*
     * Require at least one underlying device to support flushes.
     * t->devices includes internal dm devices such as mirror logs
     * so we need to use iterate_devices here, which targets
     * supporting flushes must provide.
     */
    while (i < dm_table_get_num_targets(t)) {
        ti = dm_table_get_target(t, i++);

        if (!ti->num_flush_requests)
            continue;

        if (ti->flush_supported)
            return 1;

        if (ti->type->iterate_devices &&
            ti->type->iterate_devices(ti, device_flush_capable, &flush))
            return 1;
    }

    return 0;
}

static bool dm_table_discard_zeroes_data(struct dm_table *t)
{
    struct dm_target *ti;
    unsigned i = 0;

    /* Ensure that all targets supports discard_zeroes_data. */
    while (i < dm_table_get_num_targets(t)) {
        ti = dm_table_get_target(t, i++);

        if (ti->discard_zeroes_data_unsupported)
            return 0;
    }

    return 1;
}

static int device_is_nonrot(struct dm_target *ti, struct dm_dev *dev,
                sector_t start, sector_t len, void *data)
{
    struct request_queue *q = bdev_get_queue(dev->bdev);

    return q && blk_queue_nonrot(q);
}

static int device_is_not_random(struct dm_target *ti, struct dm_dev *dev,
                 sector_t start, sector_t len, void *data)
{
    struct request_queue *q = bdev_get_queue(dev->bdev);

    return q && !blk_queue_add_random(q);
}

static bool dm_table_all_devices_attribute(struct dm_table *t,
                       iterate_devices_callout_fn func)
{
    struct dm_target *ti;
    unsigned i = 0;

    while (i < dm_table_get_num_targets(t)) {
        ti = dm_table_get_target(t, i++);

        if (!ti->type->iterate_devices ||
            !ti->type->iterate_devices(ti, func, NULL))
            return 0;
    }

    return 1;
}

void dm_table_set_restrictions(struct dm_table *t, struct request_queue *q,
                   struct queue_limits *limits)
{
    unsigned flush = 0;

    /*
     * Copy table's limits to the DM device's request_queue
     */
    q->limits = *limits;

    if (!dm_table_supports_discards(t))
        queue_flag_clear_unlocked(QUEUE_FLAG_DISCARD, q);
    else
        queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, q);

    if (dm_table_supports_flush(t, REQ_FLUSH)) {
        flush |= REQ_FLUSH;
        if (dm_table_supports_flush(t, REQ_FUA))
            flush |= REQ_FUA;
    }
    blk_queue_flush(q, flush);

    if (!dm_table_discard_zeroes_data(t))
        q->limits.discard_zeroes_data = 0;

    /* Ensure that all underlying devices are non-rotational. */
    if (dm_table_all_devices_attribute(t, device_is_nonrot))
        queue_flag_set_unlocked(QUEUE_FLAG_NONROT, q);
    else
        queue_flag_clear_unlocked(QUEUE_FLAG_NONROT, q);

    dm_table_set_integrity(t);

    /*
     * Determine whether or not this queue's I/O timings contribute
     * to the entropy pool, Only request-based targets use this.
     * Clear QUEUE_FLAG_ADD_RANDOM if any underlying device does not
     * have it set.
     */
    if (blk_queue_add_random(q) && dm_table_all_devices_attribute(t, device_is_not_random))
        queue_flag_clear_unlocked(QUEUE_FLAG_ADD_RANDOM, q);

    /*
     * QUEUE_FLAG_STACKABLE must be set after all queue settings are
     * visible to other CPUs because, once the flag is set, incoming bios
     * are processed by request-based dm, which refers to the queue
     * settings.
     * Until the flag set, bios are passed to bio-based dm and queued to
     * md->deferred where queue settings are not needed yet.
     * Those bios are passed to request-based dm at the resume time.
     */
    smp_mb();
    if (dm_table_request_based(t))
        queue_flag_set_unlocked(QUEUE_FLAG_STACKABLE, q);
}

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;
}

fmode_t dm_table_get_mode(struct dm_table *t)
{
    return t->mode;
}
EXPORT_SYMBOL(dm_table_get_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;

    suspend_targets(t, 0);
}

void dm_table_postsuspend_targets(struct dm_table *t)
{
    if (!t)
        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;
}

void dm_table_add_target_callbacks(struct dm_table *t, struct dm_target_callbacks *cb)
{
    list_add(&cb->list, &t->target_callbacks);
}
EXPORT_SYMBOL_GPL(dm_table_add_target_callbacks);

int dm_table_any_congested(struct dm_table *t, int bdi_bits)
{
    struct dm_dev_internal *dd;
    struct list_head *devices = dm_table_get_devices(t);
    struct dm_target_callbacks *cb;
    int r = 0;

    list_for_each_entry(dd, devices, list) {
        struct request_queue *q = bdev_get_queue(dd->dm_dev.bdev);
        char b[BDEVNAME_SIZE];

        if (likely(q))
            r |= bdi_congested(&q->backing_dev_info, bdi_bits);
        else
            DMWARN_LIMIT("%s: any_congested: nonexistent device %s",
                     dm_device_name(t->md),
                     bdevname(dd->dm_dev.bdev, b));
    }

    list_for_each_entry(cb, &t->target_callbacks, list)
        if (cb->congested_fn)
            r |= cb->congested_fn(cb, bdi_bits);

    return r;
}

int dm_table_any_busy_target(struct dm_table *t)
{
    unsigned i;
    struct dm_target *ti;

    for (i = 0; i < t->num_targets; i++) {
        ti = t->targets + i;
        if (ti->type->busy && ti->type->busy(ti))
            return 1;
    }

    return 0;
}

struct mapped_device *dm_table_get_md(struct dm_table *t)
{
    return t->md;
}
EXPORT_SYMBOL(dm_table_get_md);

static int device_discard_capable(struct dm_target *ti, struct dm_dev *dev,
                  sector_t start, sector_t len, void *data)
{
    struct request_queue *q = bdev_get_queue(dev->bdev);

    return q && blk_queue_discard(q);
}

bool dm_table_supports_discards(struct dm_table *t)
{
    struct dm_target *ti;
    unsigned i = 0;

    /*
     * Unless any target used by the table set discards_supported,
     * require at least one underlying device to support discards.
     * t->devices includes internal dm devices such as mirror logs
     * so we need to use iterate_devices here, which targets
     * supporting discard selectively must provide.
     */
    while (i < dm_table_get_num_targets(t)) {
        ti = dm_table_get_target(t, i++);

        if (!ti->num_discard_requests)
            continue;

        if (ti->discards_supported)
            return 1;

        if (ti->type->iterate_devices &&
            ti->type->iterate_devices(ti, device_discard_capable, NULL))
            return 1;
    }

    return 0;
}