Merge branch 'kbuild' of git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild-2.6

[mirror_ubuntu-artful-kernel.git] / drivers / md / dm-table.c

/*
 * 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 <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)

/*
 * 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;

        unsigned discards_supported:1;
        unsigned integrity_supported: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 = 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, 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);
        t->discards_supported = 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;
}

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 */
        if (t->devices.next != &t->devices)
                free_devices(&t->devices);

        dm_free_md_mempools(t->mempools);

        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;

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

/*
 * 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 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];

        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.
 */
static int __table_get_device(struct dm_table *t, 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;

        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 */
                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;
}

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 (q->merge_bvec_fn && !ti->type->merge)
                blk_limits_max_hw_sectors(limits,
                                          (unsigned int) (PAGE_SIZE >> 9));
        return 0;
}
EXPORT_SYMBOL_GPL(dm_set_device_limits);

int dm_get_device(struct dm_target *ti, const char *path, fmode_t mode,
                  struct dm_dev **result)
{
        return __table_get_device(ti->table, ti, path, mode, result);
}


/*
 * Decrement a devices 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);
        }
}

/*
 * 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_default_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 ((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;

        if (!tgt->num_discard_requests)
                t->discards_supported = 0;

        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 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;
}

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);
}

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];
}

/*
 * 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_default_limits(limits);

        while (i < dm_table_get_num_targets(table)) {
                blk_set_default_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_is_initialized(dm_disk(t->md))) {
                DMWARN("%s: device no longer has a valid integrity profile",
                       dm_device_name(t->md));
                return;
        }
        blk_integrity_register(dm_disk(t->md),
                               blk_get_integrity(template_disk));
}

void dm_table_set_restrictions(struct dm_table *t, struct request_queue *q,
                               struct queue_limits *limits)
{
        /*
         * 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);

        dm_table_set_integrity(t);

        /*
         * 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;
}

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;
}

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;

        if (!t->discards_supported)
                return 0;

        /*
         * Ensure that at least one underlying device supports discards.
         * t->devices includes internal dm devices such as mirror logs
         * so we need to use iterate_devices here, which targets
         * supporting discard must provide.
         */
        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, device_discard_capable, NULL))
                        return 1;
        }

        return 0;
}

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);