dm: fix AB-BA deadlock in __dm_destroy()

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

/*
 * Copyright (C) 2001, 2002 Sistina Software (UK) Limited.
 * Copyright (C) 2004 - 2006 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/miscdevice.h>
#include <linux/init.h>
#include <linux/wait.h>
#include <linux/slab.h>
#include <linux/dm-ioctl.h>
#include <linux/hdreg.h>
#include <linux/compat.h>

#include <asm/uaccess.h>

#define DM_MSG_PREFIX "ioctl"
#define DM_DRIVER_EMAIL "dm-devel@redhat.com"

/*-----------------------------------------------------------------
 * The ioctl interface needs to be able to look up devices by
 * name or uuid.
 *---------------------------------------------------------------*/
struct hash_cell {
        struct list_head name_list;
        struct list_head uuid_list;

        char *name;
        char *uuid;
        struct mapped_device *md;
        struct dm_table *new_map;
};

/*
 * A dummy definition to make RCU happy.
 * struct dm_table should never be dereferenced in this file.
 */
struct dm_table {
        int undefined__;
};

struct vers_iter {
    size_t param_size;
    struct dm_target_versions *vers, *old_vers;
    char *end;
    uint32_t flags;
};


#define NUM_BUCKETS 64
#define MASK_BUCKETS (NUM_BUCKETS - 1)
static struct list_head _name_buckets[NUM_BUCKETS];
static struct list_head _uuid_buckets[NUM_BUCKETS];

static void dm_hash_remove_all(bool keep_open_devices, bool mark_deferred, bool only_deferred);

/*
 * Guards access to both hash tables.
 */
static DECLARE_RWSEM(_hash_lock);

/*
 * Protects use of mdptr to obtain hash cell name and uuid from mapped device.
 */
static DEFINE_MUTEX(dm_hash_cells_mutex);

static void init_buckets(struct list_head *buckets)
{
        unsigned int i;

        for (i = 0; i < NUM_BUCKETS; i++)
                INIT_LIST_HEAD(buckets + i);
}

static int dm_hash_init(void)
{
        init_buckets(_name_buckets);
        init_buckets(_uuid_buckets);
        return 0;
}

static void dm_hash_exit(void)
{
        dm_hash_remove_all(false, false, false);
}

/*-----------------------------------------------------------------
 * Hash function:
 * We're not really concerned with the str hash function being
 * fast since it's only used by the ioctl interface.
 *---------------------------------------------------------------*/
static unsigned int hash_str(const char *str)
{
        const unsigned int hash_mult = 2654435387U;
        unsigned int h = 0;

        while (*str)
                h = (h + (unsigned int) *str++) * hash_mult;

        return h & MASK_BUCKETS;
}

/*-----------------------------------------------------------------
 * Code for looking up a device by name
 *---------------------------------------------------------------*/
static struct hash_cell *__get_name_cell(const char *str)
{
        struct hash_cell *hc;
        unsigned int h = hash_str(str);

        list_for_each_entry (hc, _name_buckets + h, name_list)
                if (!strcmp(hc->name, str)) {
                        dm_get(hc->md);
                        return hc;
                }

        return NULL;
}

static struct hash_cell *__get_uuid_cell(const char *str)
{
        struct hash_cell *hc;
        unsigned int h = hash_str(str);

        list_for_each_entry (hc, _uuid_buckets + h, uuid_list)
                if (!strcmp(hc->uuid, str)) {
                        dm_get(hc->md);
                        return hc;
                }

        return NULL;
}

static struct hash_cell *__get_dev_cell(uint64_t dev)
{
        struct mapped_device *md;
        struct hash_cell *hc;

        md = dm_get_md(huge_decode_dev(dev));
        if (!md)
                return NULL;

        hc = dm_get_mdptr(md);
        if (!hc) {
                dm_put(md);
                return NULL;
        }

        return hc;
}

/*-----------------------------------------------------------------
 * Inserting, removing and renaming a device.
 *---------------------------------------------------------------*/
static struct hash_cell *alloc_cell(const char *name, const char *uuid,
                                    struct mapped_device *md)
{
        struct hash_cell *hc;

        hc = kmalloc(sizeof(*hc), GFP_KERNEL);
        if (!hc)
                return NULL;

        hc->name = kstrdup(name, GFP_KERNEL);
        if (!hc->name) {
                kfree(hc);
                return NULL;
        }

        if (!uuid)
                hc->uuid = NULL;

        else {
                hc->uuid = kstrdup(uuid, GFP_KERNEL);
                if (!hc->uuid) {
                        kfree(hc->name);
                        kfree(hc);
                        return NULL;
                }
        }

        INIT_LIST_HEAD(&hc->name_list);
        INIT_LIST_HEAD(&hc->uuid_list);
        hc->md = md;
        hc->new_map = NULL;
        return hc;
}

static void free_cell(struct hash_cell *hc)
{
        if (hc) {
                kfree(hc->name);
                kfree(hc->uuid);
                kfree(hc);
        }
}

/*
 * The kdev_t and uuid of a device can never change once it is
 * initially inserted.
 */
static int dm_hash_insert(const char *name, const char *uuid, struct mapped_device *md)
{
        struct hash_cell *cell, *hc;

        /*
         * Allocate the new cells.
         */
        cell = alloc_cell(name, uuid, md);
        if (!cell)
                return -ENOMEM;

        /*
         * Insert the cell into both hash tables.
         */
        down_write(&_hash_lock);
        hc = __get_name_cell(name);
        if (hc) {
                dm_put(hc->md);
                goto bad;
        }

        list_add(&cell->name_list, _name_buckets + hash_str(name));

        if (uuid) {
                hc = __get_uuid_cell(uuid);
                if (hc) {
                        list_del(&cell->name_list);
                        dm_put(hc->md);
                        goto bad;
                }
                list_add(&cell->uuid_list, _uuid_buckets + hash_str(uuid));
        }
        dm_get(md);
        mutex_lock(&dm_hash_cells_mutex);
        dm_set_mdptr(md, cell);
        mutex_unlock(&dm_hash_cells_mutex);
        up_write(&_hash_lock);

        return 0;

 bad:
        up_write(&_hash_lock);
        free_cell(cell);
        return -EBUSY;
}

static struct dm_table *__hash_remove(struct hash_cell *hc)
{
        struct dm_table *table;
        int srcu_idx;

        /* remove from the dev hash */
        list_del(&hc->uuid_list);
        list_del(&hc->name_list);
        mutex_lock(&dm_hash_cells_mutex);
        dm_set_mdptr(hc->md, NULL);
        mutex_unlock(&dm_hash_cells_mutex);

        table = dm_get_live_table(hc->md, &srcu_idx);
        if (table)
                dm_table_event(table);
        dm_put_live_table(hc->md, srcu_idx);

        table = NULL;
        if (hc->new_map)
                table = hc->new_map;
        dm_put(hc->md);
        free_cell(hc);

        return table;
}

static void dm_hash_remove_all(bool keep_open_devices, bool mark_deferred, bool only_deferred)
{
        int i, dev_skipped;
        struct hash_cell *hc;
        struct mapped_device *md;
        struct dm_table *t;

retry:
        dev_skipped = 0;

        down_write(&_hash_lock);

        for (i = 0; i < NUM_BUCKETS; i++) {
                list_for_each_entry(hc, _name_buckets + i, name_list) {
                        md = hc->md;
                        dm_get(md);

                        if (keep_open_devices &&
                            dm_lock_for_deletion(md, mark_deferred, only_deferred)) {
                                dm_put(md);
                                dev_skipped++;
                                continue;
                        }

                        t = __hash_remove(hc);

                        up_write(&_hash_lock);

                        if (t) {
                                dm_sync_table(md);
                                dm_table_destroy(t);
                        }
                        dm_put(md);
                        if (likely(keep_open_devices))
                                dm_destroy(md);
                        else
                                dm_destroy_immediate(md);

                        /*
                         * Some mapped devices may be using other mapped
                         * devices, so repeat until we make no further
                         * progress.  If a new mapped device is created
                         * here it will also get removed.
                         */
                        goto retry;
                }
        }

        up_write(&_hash_lock);

        if (dev_skipped)
                DMWARN("remove_all left %d open device(s)", dev_skipped);
}

/*
 * Set the uuid of a hash_cell that isn't already set.
 */
static void __set_cell_uuid(struct hash_cell *hc, char *new_uuid)
{
        mutex_lock(&dm_hash_cells_mutex);
        hc->uuid = new_uuid;
        mutex_unlock(&dm_hash_cells_mutex);

        list_add(&hc->uuid_list, _uuid_buckets + hash_str(new_uuid));
}

/*
 * Changes the name of a hash_cell and returns the old name for
 * the caller to free.
 */
static char *__change_cell_name(struct hash_cell *hc, char *new_name)
{
        char *old_name;

        /*
         * Rename and move the name cell.
         */
        list_del(&hc->name_list);
        old_name = hc->name;

        mutex_lock(&dm_hash_cells_mutex);
        hc->name = new_name;
        mutex_unlock(&dm_hash_cells_mutex);

        list_add(&hc->name_list, _name_buckets + hash_str(new_name));

        return old_name;
}

static struct mapped_device *dm_hash_rename(struct dm_ioctl *param,
                                            const char *new)
{
        char *new_data, *old_name = NULL;
        struct hash_cell *hc;
        struct dm_table *table;
        struct mapped_device *md;
        unsigned change_uuid = (param->flags & DM_UUID_FLAG) ? 1 : 0;
        int srcu_idx;

        /*
         * duplicate new.
         */
        new_data = kstrdup(new, GFP_KERNEL);
        if (!new_data)
                return ERR_PTR(-ENOMEM);

        down_write(&_hash_lock);

        /*
         * Is new free ?
         */
        if (change_uuid)
                hc = __get_uuid_cell(new);
        else
                hc = __get_name_cell(new);

        if (hc) {
                DMWARN("Unable to change %s on mapped device %s to one that "
                       "already exists: %s",
                       change_uuid ? "uuid" : "name",
                       param->name, new);
                dm_put(hc->md);
                up_write(&_hash_lock);
                kfree(new_data);
                return ERR_PTR(-EBUSY);
        }

        /*
         * Is there such a device as 'old' ?
         */
        hc = __get_name_cell(param->name);
        if (!hc) {
                DMWARN("Unable to rename non-existent device, %s to %s%s",
                       param->name, change_uuid ? "uuid " : "", new);
                up_write(&_hash_lock);
                kfree(new_data);
                return ERR_PTR(-ENXIO);
        }

        /*
         * Does this device already have a uuid?
         */
        if (change_uuid && hc->uuid) {
                DMWARN("Unable to change uuid of mapped device %s to %s "
                       "because uuid is already set to %s",
                       param->name, new, hc->uuid);
                dm_put(hc->md);
                up_write(&_hash_lock);
                kfree(new_data);
                return ERR_PTR(-EINVAL);
        }

        if (change_uuid)
                __set_cell_uuid(hc, new_data);
        else
                old_name = __change_cell_name(hc, new_data);

        /*
         * Wake up any dm event waiters.
         */
        table = dm_get_live_table(hc->md, &srcu_idx);
        if (table)
                dm_table_event(table);
        dm_put_live_table(hc->md, srcu_idx);

        if (!dm_kobject_uevent(hc->md, KOBJ_CHANGE, param->event_nr))
                param->flags |= DM_UEVENT_GENERATED_FLAG;

        md = hc->md;
        up_write(&_hash_lock);
        kfree(old_name);

        return md;
}

void dm_deferred_remove(void)
{
        dm_hash_remove_all(true, false, true);
}

/*-----------------------------------------------------------------
 * Implementation of the ioctl commands
 *---------------------------------------------------------------*/
/*
 * All the ioctl commands get dispatched to functions with this
 * prototype.
 */
typedef int (*ioctl_fn)(struct dm_ioctl *param, size_t param_size);

static int remove_all(struct dm_ioctl *param, size_t param_size)
{
        dm_hash_remove_all(true, !!(param->flags & DM_DEFERRED_REMOVE), false);
        param->data_size = 0;
        return 0;
}

/*
 * Round up the ptr to an 8-byte boundary.
 */
#define ALIGN_MASK 7
static inline void *align_ptr(void *ptr)
{
        return (void *) (((size_t) (ptr + ALIGN_MASK)) & ~ALIGN_MASK);
}

/*
 * Retrieves the data payload buffer from an already allocated
 * struct dm_ioctl.
 */
static void *get_result_buffer(struct dm_ioctl *param, size_t param_size,
                               size_t *len)
{
        param->data_start = align_ptr(param + 1) - (void *) param;

        if (param->data_start < param_size)
                *len = param_size - param->data_start;
        else
                *len = 0;

        return ((void *) param) + param->data_start;
}

static int list_devices(struct dm_ioctl *param, size_t param_size)
{
        unsigned int i;
        struct hash_cell *hc;
        size_t len, needed = 0;
        struct gendisk *disk;
        struct dm_name_list *nl, *old_nl = NULL;

        down_write(&_hash_lock);

        /*
         * Loop through all the devices working out how much
         * space we need.
         */
        for (i = 0; i < NUM_BUCKETS; i++) {
                list_for_each_entry (hc, _name_buckets + i, name_list) {
                        needed += sizeof(struct dm_name_list);
                        needed += strlen(hc->name) + 1;
                        needed += ALIGN_MASK;
                }
        }

        /*
         * Grab our output buffer.
         */
        nl = get_result_buffer(param, param_size, &len);
        if (len < needed) {
                param->flags |= DM_BUFFER_FULL_FLAG;
                goto out;
        }
        param->data_size = param->data_start + needed;

        nl->dev = 0;    /* Flags no data */

        /*
         * Now loop through filling out the names.
         */
        for (i = 0; i < NUM_BUCKETS; i++) {
                list_for_each_entry (hc, _name_buckets + i, name_list) {
                        if (old_nl)
                                old_nl->next = (uint32_t) ((void *) nl -
                                                           (void *) old_nl);
                        disk = dm_disk(hc->md);
                        nl->dev = huge_encode_dev(disk_devt(disk));
                        nl->next = 0;
                        strcpy(nl->name, hc->name);

                        old_nl = nl;
                        nl = align_ptr(((void *) ++nl) + strlen(hc->name) + 1);
                }
        }

 out:
        up_write(&_hash_lock);
        return 0;
}

static void list_version_get_needed(struct target_type *tt, void *needed_param)
{
    size_t *needed = needed_param;

    *needed += sizeof(struct dm_target_versions);
    *needed += strlen(tt->name);
    *needed += ALIGN_MASK;
}

static void list_version_get_info(struct target_type *tt, void *param)
{
    struct vers_iter *info = param;

    /* Check space - it might have changed since the first iteration */
    if ((char *)info->vers + sizeof(tt->version) + strlen(tt->name) + 1 >
        info->end) {

        info->flags = DM_BUFFER_FULL_FLAG;
        return;
    }

    if (info->old_vers)
        info->old_vers->next = (uint32_t) ((void *)info->vers -
                                           (void *)info->old_vers);
    info->vers->version[0] = tt->version[0];
    info->vers->version[1] = tt->version[1];
    info->vers->version[2] = tt->version[2];
    info->vers->next = 0;
    strcpy(info->vers->name, tt->name);

    info->old_vers = info->vers;
    info->vers = align_ptr(((void *) ++info->vers) + strlen(tt->name) + 1);
}

static int list_versions(struct dm_ioctl *param, size_t param_size)
{
        size_t len, needed = 0;
        struct dm_target_versions *vers;
        struct vers_iter iter_info;

        /*
         * Loop through all the devices working out how much
         * space we need.
         */
        dm_target_iterate(list_version_get_needed, &needed);

        /*
         * Grab our output buffer.
         */
        vers = get_result_buffer(param, param_size, &len);
        if (len < needed) {
                param->flags |= DM_BUFFER_FULL_FLAG;
                goto out;
        }
        param->data_size = param->data_start + needed;

        iter_info.param_size = param_size;
        iter_info.old_vers = NULL;
        iter_info.vers = vers;
        iter_info.flags = 0;
        iter_info.end = (char *)vers+len;

        /*
         * Now loop through filling out the names & versions.
         */
        dm_target_iterate(list_version_get_info, &iter_info);
        param->flags |= iter_info.flags;

 out:
        return 0;
}

static int check_name(const char *name)
{
        if (strchr(name, '/')) {
                DMWARN("invalid device name");
                return -EINVAL;
        }

        return 0;
}

/*
 * On successful return, the caller must not attempt to acquire
 * _hash_lock without first calling dm_put_live_table, because dm_table_destroy
 * waits for this dm_put_live_table and could be called under this lock.
 */
static struct dm_table *dm_get_inactive_table(struct mapped_device *md, int *srcu_idx)
{
        struct hash_cell *hc;
        struct dm_table *table = NULL;

        /* increment rcu count, we don't care about the table pointer */
        dm_get_live_table(md, srcu_idx);

        down_read(&_hash_lock);
        hc = dm_get_mdptr(md);
        if (!hc || hc->md != md) {
                DMWARN("device has been removed from the dev hash table.");
                goto out;
        }

        table = hc->new_map;

out:
        up_read(&_hash_lock);

        return table;
}

static struct dm_table *dm_get_live_or_inactive_table(struct mapped_device *md,
                                                      struct dm_ioctl *param,
                                                      int *srcu_idx)
{
        return (param->flags & DM_QUERY_INACTIVE_TABLE_FLAG) ?
                dm_get_inactive_table(md, srcu_idx) : dm_get_live_table(md, srcu_idx);
}

/*
 * Fills in a dm_ioctl structure, ready for sending back to
 * userland.
 */
static void __dev_status(struct mapped_device *md, struct dm_ioctl *param)
{
        struct gendisk *disk = dm_disk(md);
        struct dm_table *table;
        int srcu_idx;

        param->flags &= ~(DM_SUSPEND_FLAG | DM_READONLY_FLAG |
                          DM_ACTIVE_PRESENT_FLAG | DM_INTERNAL_SUSPEND_FLAG);

        if (dm_suspended_md(md))
                param->flags |= DM_SUSPEND_FLAG;

        if (dm_suspended_internally_md(md))
                param->flags |= DM_INTERNAL_SUSPEND_FLAG;

        if (dm_test_deferred_remove_flag(md))
                param->flags |= DM_DEFERRED_REMOVE;

        param->dev = huge_encode_dev(disk_devt(disk));

        /*
         * Yes, this will be out of date by the time it gets back
         * to userland, but it is still very useful for
         * debugging.
         */
        param->open_count = dm_open_count(md);

        param->event_nr = dm_get_event_nr(md);
        param->target_count = 0;

        table = dm_get_live_table(md, &srcu_idx);
        if (table) {
                if (!(param->flags & DM_QUERY_INACTIVE_TABLE_FLAG)) {
                        if (get_disk_ro(disk))
                                param->flags |= DM_READONLY_FLAG;
                        param->target_count = dm_table_get_num_targets(table);
                }

                param->flags |= DM_ACTIVE_PRESENT_FLAG;
        }
        dm_put_live_table(md, srcu_idx);

        if (param->flags & DM_QUERY_INACTIVE_TABLE_FLAG) {
                int srcu_idx;
                table = dm_get_inactive_table(md, &srcu_idx);
                if (table) {
                        if (!(dm_table_get_mode(table) & FMODE_WRITE))
                                param->flags |= DM_READONLY_FLAG;
                        param->target_count = dm_table_get_num_targets(table);
                }
                dm_put_live_table(md, srcu_idx);
        }
}

static int dev_create(struct dm_ioctl *param, size_t param_size)
{
        int r, m = DM_ANY_MINOR;
        struct mapped_device *md;

        r = check_name(param->name);
        if (r)
                return r;

        if (param->flags & DM_PERSISTENT_DEV_FLAG)
                m = MINOR(huge_decode_dev(param->dev));

        r = dm_create(m, &md);
        if (r)
                return r;

        r = dm_hash_insert(param->name, *param->uuid ? param->uuid : NULL, md);
        if (r) {
                dm_put(md);
                dm_destroy(md);
                return r;
        }

        param->flags &= ~DM_INACTIVE_PRESENT_FLAG;

        __dev_status(md, param);

        dm_put(md);

        return 0;
}

/*
 * Always use UUID for lookups if it's present, otherwise use name or dev.
 */
static struct hash_cell *__find_device_hash_cell(struct dm_ioctl *param)
{
        struct hash_cell *hc = NULL;

        if (*param->uuid) {
                if (*param->name || param->dev)
                        return NULL;

                hc = __get_uuid_cell(param->uuid);
                if (!hc)
                        return NULL;
        } else if (*param->name) {
                if (param->dev)
                        return NULL;

                hc = __get_name_cell(param->name);
                if (!hc)
                        return NULL;
        } else if (param->dev) {
                hc = __get_dev_cell(param->dev);
                if (!hc)
                        return NULL;
        } else
                return NULL;

        /*
         * Sneakily write in both the name and the uuid
         * while we have the cell.
         */
        strlcpy(param->name, hc->name, sizeof(param->name));
        if (hc->uuid)
                strlcpy(param->uuid, hc->uuid, sizeof(param->uuid));
        else
                param->uuid[0] = '\0';

        if (hc->new_map)
                param->flags |= DM_INACTIVE_PRESENT_FLAG;
        else
                param->flags &= ~DM_INACTIVE_PRESENT_FLAG;

        return hc;
}

static struct mapped_device *find_device(struct dm_ioctl *param)
{
        struct hash_cell *hc;
        struct mapped_device *md = NULL;

        down_read(&_hash_lock);
        hc = __find_device_hash_cell(param);
        if (hc)
                md = hc->md;
        up_read(&_hash_lock);

        return md;
}

static int dev_remove(struct dm_ioctl *param, size_t param_size)
{
        struct hash_cell *hc;
        struct mapped_device *md;
        int r;
        struct dm_table *t;

        down_write(&_hash_lock);
        hc = __find_device_hash_cell(param);

        if (!hc) {
                DMDEBUG_LIMIT("device doesn't appear to be in the dev hash table.");
                up_write(&_hash_lock);
                return -ENXIO;
        }

        md = hc->md;

        /*
         * Ensure the device is not open and nothing further can open it.
         */
        r = dm_lock_for_deletion(md, !!(param->flags & DM_DEFERRED_REMOVE), false);
        if (r) {
                if (r == -EBUSY && param->flags & DM_DEFERRED_REMOVE) {
                        up_write(&_hash_lock);
                        dm_put(md);
                        return 0;
                }
                DMDEBUG_LIMIT("unable to remove open device %s", hc->name);
                up_write(&_hash_lock);
                dm_put(md);
                return r;
        }

        t = __hash_remove(hc);
        up_write(&_hash_lock);

        if (t) {
                dm_sync_table(md);
                dm_table_destroy(t);
        }

        param->flags &= ~DM_DEFERRED_REMOVE;

        if (!dm_kobject_uevent(md, KOBJ_REMOVE, param->event_nr))
                param->flags |= DM_UEVENT_GENERATED_FLAG;

        dm_put(md);
        dm_destroy(md);
        return 0;
}

/*
 * Check a string doesn't overrun the chunk of
 * memory we copied from userland.
 */
static int invalid_str(char *str, void *end)
{
        while ((void *) str < end)
                if (!*str++)
                        return 0;

        return -EINVAL;
}

static int dev_rename(struct dm_ioctl *param, size_t param_size)
{
        int r;
        char *new_data = (char *) param + param->data_start;
        struct mapped_device *md;
        unsigned change_uuid = (param->flags & DM_UUID_FLAG) ? 1 : 0;

        if (new_data < param->data ||
            invalid_str(new_data, (void *) param + param_size) || !*new_data ||
            strlen(new_data) > (change_uuid ? DM_UUID_LEN - 1 : DM_NAME_LEN - 1)) {
                DMWARN("Invalid new mapped device name or uuid string supplied.");
                return -EINVAL;
        }

        if (!change_uuid) {
                r = check_name(new_data);
                if (r)
                        return r;
        }

        md = dm_hash_rename(param, new_data);
        if (IS_ERR(md))
                return PTR_ERR(md);

        __dev_status(md, param);
        dm_put(md);

        return 0;
}

static int dev_set_geometry(struct dm_ioctl *param, size_t param_size)
{
        int r = -EINVAL, x;
        struct mapped_device *md;
        struct hd_geometry geometry;
        unsigned long indata[4];
        char *geostr = (char *) param + param->data_start;
        char dummy;

        md = find_device(param);
        if (!md)
                return -ENXIO;

        if (geostr < param->data ||
            invalid_str(geostr, (void *) param + param_size)) {
                DMWARN("Invalid geometry supplied.");
                goto out;
        }

        x = sscanf(geostr, "%lu %lu %lu %lu%c", indata,
                   indata + 1, indata + 2, indata + 3, &dummy);

        if (x != 4) {
                DMWARN("Unable to interpret geometry settings.");
                goto out;
        }

        if (indata[0] > 65535 || indata[1] > 255 ||
            indata[2] > 255 || indata[3] > ULONG_MAX) {
                DMWARN("Geometry exceeds range limits.");
                goto out;
        }

        geometry.cylinders = indata[0];
        geometry.heads = indata[1];
        geometry.sectors = indata[2];
        geometry.start = indata[3];

        r = dm_set_geometry(md, &geometry);

        param->data_size = 0;

out:
        dm_put(md);
        return r;
}

static int do_suspend(struct dm_ioctl *param)
{
        int r = 0;
        unsigned suspend_flags = DM_SUSPEND_LOCKFS_FLAG;
        struct mapped_device *md;

        md = find_device(param);
        if (!md)
                return -ENXIO;

        if (param->flags & DM_SKIP_LOCKFS_FLAG)
                suspend_flags &= ~DM_SUSPEND_LOCKFS_FLAG;
        if (param->flags & DM_NOFLUSH_FLAG)
                suspend_flags |= DM_SUSPEND_NOFLUSH_FLAG;

        if (!dm_suspended_md(md)) {
                r = dm_suspend(md, suspend_flags);
                if (r)
                        goto out;
        }

        __dev_status(md, param);

out:
        dm_put(md);

        return r;
}

static int do_resume(struct dm_ioctl *param)
{
        int r = 0;
        unsigned suspend_flags = DM_SUSPEND_LOCKFS_FLAG;
        struct hash_cell *hc;
        struct mapped_device *md;
        struct dm_table *new_map, *old_map = NULL;

        down_write(&_hash_lock);

        hc = __find_device_hash_cell(param);
        if (!hc) {
                DMDEBUG_LIMIT("device doesn't appear to be in the dev hash table.");
                up_write(&_hash_lock);
                return -ENXIO;
        }

        md = hc->md;

        new_map = hc->new_map;
        hc->new_map = NULL;
        param->flags &= ~DM_INACTIVE_PRESENT_FLAG;

        up_write(&_hash_lock);

        /* Do we need to load a new map ? */
        if (new_map) {
                /* Suspend if it isn't already suspended */
                if (param->flags & DM_SKIP_LOCKFS_FLAG)
                        suspend_flags &= ~DM_SUSPEND_LOCKFS_FLAG;
                if (param->flags & DM_NOFLUSH_FLAG)
                        suspend_flags |= DM_SUSPEND_NOFLUSH_FLAG;
                if (!dm_suspended_md(md))
                        dm_suspend(md, suspend_flags);

                old_map = dm_swap_table(md, new_map);
                if (IS_ERR(old_map)) {
                        dm_sync_table(md);
                        dm_table_destroy(new_map);
                        dm_put(md);
                        return PTR_ERR(old_map);
                }

                if (dm_table_get_mode(new_map) & FMODE_WRITE)
                        set_disk_ro(dm_disk(md), 0);
                else
                        set_disk_ro(dm_disk(md), 1);
        }

        if (dm_suspended_md(md)) {
                r = dm_resume(md);
                if (!r && !dm_kobject_uevent(md, KOBJ_CHANGE, param->event_nr))
                        param->flags |= DM_UEVENT_GENERATED_FLAG;
        }

        /*
         * Since dm_swap_table synchronizes RCU, nobody should be in
         * read-side critical section already.
         */
        if (old_map)
                dm_table_destroy(old_map);

        if (!r)
                __dev_status(md, param);

        dm_put(md);
        return r;
}

/*
 * Set or unset the suspension state of a device.
 * If the device already is in the requested state we just return its status.
 */
static int dev_suspend(struct dm_ioctl *param, size_t param_size)
{
        if (param->flags & DM_SUSPEND_FLAG)
                return do_suspend(param);

        return do_resume(param);
}

/*
 * Copies device info back to user space, used by
 * the create and info ioctls.
 */
static int dev_status(struct dm_ioctl *param, size_t param_size)
{
        struct mapped_device *md;

        md = find_device(param);
        if (!md)
                return -ENXIO;

        __dev_status(md, param);
        dm_put(md);

        return 0;
}

/*
 * Build up the status struct for each target
 */
static void retrieve_status(struct dm_table *table,
                            struct dm_ioctl *param, size_t param_size)
{
        unsigned int i, num_targets;
        struct dm_target_spec *spec;
        char *outbuf, *outptr;
        status_type_t type;
        size_t remaining, len, used = 0;
        unsigned status_flags = 0;

        outptr = outbuf = get_result_buffer(param, param_size, &len);

        if (param->flags & DM_STATUS_TABLE_FLAG)
                type = STATUSTYPE_TABLE;
        else
                type = STATUSTYPE_INFO;

        /* Get all the target info */
        num_targets = dm_table_get_num_targets(table);
        for (i = 0; i < num_targets; i++) {
                struct dm_target *ti = dm_table_get_target(table, i);
                size_t l;

                remaining = len - (outptr - outbuf);
                if (remaining <= sizeof(struct dm_target_spec)) {
                        param->flags |= DM_BUFFER_FULL_FLAG;
                        break;
                }

                spec = (struct dm_target_spec *) outptr;

                spec->status = 0;
                spec->sector_start = ti->begin;
                spec->length = ti->len;
                strncpy(spec->target_type, ti->type->name,
                        sizeof(spec->target_type));

                outptr += sizeof(struct dm_target_spec);
                remaining = len - (outptr - outbuf);
                if (remaining <= 0) {
                        param->flags |= DM_BUFFER_FULL_FLAG;
                        break;
                }

                /* Get the status/table string from the target driver */
                if (ti->type->status) {
                        if (param->flags & DM_NOFLUSH_FLAG)
                                status_flags |= DM_STATUS_NOFLUSH_FLAG;
                        ti->type->status(ti, type, status_flags, outptr, remaining);
                } else
                        outptr[0] = '\0';

                l = strlen(outptr) + 1;
                if (l == remaining) {
                        param->flags |= DM_BUFFER_FULL_FLAG;
                        break;
                }

                outptr += l;
                used = param->data_start + (outptr - outbuf);

                outptr = align_ptr(outptr);
                spec->next = outptr - outbuf;
        }

        if (used)
                param->data_size = used;

        param->target_count = num_targets;
}

/*
 * Wait for a device to report an event
 */
static int dev_wait(struct dm_ioctl *param, size_t param_size)
{
        int r = 0;
        struct mapped_device *md;
        struct dm_table *table;
        int srcu_idx;

        md = find_device(param);
        if (!md)
                return -ENXIO;

        /*
         * Wait for a notification event
         */
        if (dm_wait_event(md, param->event_nr)) {
                r = -ERESTARTSYS;
                goto out;
        }

        /*
         * The userland program is going to want to know what
         * changed to trigger the event, so we may as well tell
         * him and save an ioctl.
         */
        __dev_status(md, param);

        table = dm_get_live_or_inactive_table(md, param, &srcu_idx);
        if (table)
                retrieve_status(table, param, param_size);
        dm_put_live_table(md, srcu_idx);

out:
        dm_put(md);

        return r;
}

static inline fmode_t get_mode(struct dm_ioctl *param)
{
        fmode_t mode = FMODE_READ | FMODE_WRITE;

        if (param->flags & DM_READONLY_FLAG)
                mode = FMODE_READ;

        return mode;
}

static int next_target(struct dm_target_spec *last, uint32_t next, void *end,
                       struct dm_target_spec **spec, char **target_params)
{
        *spec = (struct dm_target_spec *) ((unsigned char *) last + next);
        *target_params = (char *) (*spec + 1);

        if (*spec < (last + 1))
                return -EINVAL;

        return invalid_str(*target_params, end);
}

static int populate_table(struct dm_table *table,
                          struct dm_ioctl *param, size_t param_size)
{
        int r;
        unsigned int i = 0;
        struct dm_target_spec *spec = (struct dm_target_spec *) param;
        uint32_t next = param->data_start;
        void *end = (void *) param + param_size;
        char *target_params;

        if (!param->target_count) {
                DMWARN("populate_table: no targets specified");
                return -EINVAL;
        }

        for (i = 0; i < param->target_count; i++) {

                r = next_target(spec, next, end, &spec, &target_params);
                if (r) {
                        DMWARN("unable to find target");
                        return r;
                }

                r = dm_table_add_target(table, spec->target_type,
                                        (sector_t) spec->sector_start,
                                        (sector_t) spec->length,
                                        target_params);
                if (r) {
                        DMWARN("error adding target to table");
                        return r;
                }

                next = spec->next;
        }

        return dm_table_complete(table);
}

static int table_load(struct dm_ioctl *param, size_t param_size)
{
        int r;
        struct hash_cell *hc;
        struct dm_table *t, *old_map = NULL;
        struct mapped_device *md;
        struct target_type *immutable_target_type;

        md = find_device(param);
        if (!md)
                return -ENXIO;

        r = dm_table_create(&t, get_mode(param), param->target_count, md);
        if (r)
                goto err;

        /* Protect md->type and md->queue against concurrent table loads. */
        dm_lock_md_type(md);
        r = populate_table(t, param, param_size);
        if (r)
                goto err_unlock_md_type;

        immutable_target_type = dm_get_immutable_target_type(md);
        if (immutable_target_type &&
            (immutable_target_type != dm_table_get_immutable_target_type(t))) {
                DMWARN("can't replace immutable target type %s",
                       immutable_target_type->name);
                r = -EINVAL;
                goto err_unlock_md_type;
        }

        if (dm_get_md_type(md) == DM_TYPE_NONE) {
                /* Initial table load: acquire type of table. */
                dm_set_md_type(md, dm_table_get_type(t));

                /* setup md->queue to reflect md's type (may block) */
                r = dm_setup_md_queue(md);
                if (r) {
                        DMWARN("unable to set up device queue for new table.");
                        goto err_unlock_md_type;
                }
        } else if (dm_get_md_type(md) != dm_table_get_type(t)) {
                DMWARN("can't change device type after initial table load.");
                r = -EINVAL;
                goto err_unlock_md_type;
        }

        dm_unlock_md_type(md);

        /* stage inactive table */
        down_write(&_hash_lock);
        hc = dm_get_mdptr(md);
        if (!hc || hc->md != md) {
                DMWARN("device has been removed from the dev hash table.");
                up_write(&_hash_lock);
                r = -ENXIO;
                goto err_destroy_table;
        }

        if (hc->new_map)
                old_map = hc->new_map;
        hc->new_map = t;
        up_write(&_hash_lock);

        param->flags |= DM_INACTIVE_PRESENT_FLAG;
        __dev_status(md, param);

        if (old_map) {
                dm_sync_table(md);
                dm_table_destroy(old_map);
        }

        dm_put(md);

        return 0;

err_unlock_md_type:
        dm_unlock_md_type(md);
err_destroy_table:
        dm_table_destroy(t);
err:
        dm_put(md);

        return r;
}

static int table_clear(struct dm_ioctl *param, size_t param_size)
{
        struct hash_cell *hc;
        struct mapped_device *md;
        struct dm_table *old_map = NULL;

        down_write(&_hash_lock);

        hc = __find_device_hash_cell(param);
        if (!hc) {
                DMDEBUG_LIMIT("device doesn't appear to be in the dev hash table.");
                up_write(&_hash_lock);
                return -ENXIO;
        }

        if (hc->new_map) {
                old_map = hc->new_map;
                hc->new_map = NULL;
        }

        param->flags &= ~DM_INACTIVE_PRESENT_FLAG;

        __dev_status(hc->md, param);
        md = hc->md;
        up_write(&_hash_lock);
        if (old_map) {
                dm_sync_table(md);
                dm_table_destroy(old_map);
        }
        dm_put(md);

        return 0;
}

/*
 * Retrieves a list of devices used by a particular dm device.
 */
static void retrieve_deps(struct dm_table *table,
                          struct dm_ioctl *param, size_t param_size)
{
        unsigned int count = 0;
        struct list_head *tmp;
        size_t len, needed;
        struct dm_dev_internal *dd;
        struct dm_target_deps *deps;

        deps = get_result_buffer(param, param_size, &len);

        /*
         * Count the devices.
         */
        list_for_each (tmp, dm_table_get_devices(table))
                count++;

        /*
         * Check we have enough space.
         */
        needed = sizeof(*deps) + (sizeof(*deps->dev) * count);
        if (len < needed) {
                param->flags |= DM_BUFFER_FULL_FLAG;
                return;
        }

        /*
         * Fill in the devices.
         */
        deps->count = count;
        count = 0;
        list_for_each_entry (dd, dm_table_get_devices(table), list)
                deps->dev[count++] = huge_encode_dev(dd->dm_dev->bdev->bd_dev);

        param->data_size = param->data_start + needed;
}

static int table_deps(struct dm_ioctl *param, size_t param_size)
{
        struct mapped_device *md;
        struct dm_table *table;
        int srcu_idx;

        md = find_device(param);
        if (!md)
                return -ENXIO;

        __dev_status(md, param);

        table = dm_get_live_or_inactive_table(md, param, &srcu_idx);
        if (table)
                retrieve_deps(table, param, param_size);
        dm_put_live_table(md, srcu_idx);

        dm_put(md);

        return 0;
}

/*
 * Return the status of a device as a text string for each
 * target.
 */
static int table_status(struct dm_ioctl *param, size_t param_size)
{
        struct mapped_device *md;
        struct dm_table *table;
        int srcu_idx;

        md = find_device(param);
        if (!md)
                return -ENXIO;

        __dev_status(md, param);

        table = dm_get_live_or_inactive_table(md, param, &srcu_idx);
        if (table)
                retrieve_status(table, param, param_size);
        dm_put_live_table(md, srcu_idx);

        dm_put(md);

        return 0;
}

/*
 * Process device-mapper dependent messages.  Messages prefixed with '@'
 * are processed by the DM core.  All others are delivered to the target.
 * Returns a number <= 1 if message was processed by device mapper.
 * Returns 2 if message should be delivered to the target.
 */
static int message_for_md(struct mapped_device *md, unsigned argc, char **argv,
                          char *result, unsigned maxlen)
{
        int r;

        if (**argv != '@')
                return 2; /* no '@' prefix, deliver to target */

        if (!strcasecmp(argv[0], "@cancel_deferred_remove")) {
                if (argc != 1) {
                        DMERR("Invalid arguments for @cancel_deferred_remove");
                        return -EINVAL;
                }
                return dm_cancel_deferred_remove(md);
        }

        r = dm_stats_message(md, argc, argv, result, maxlen);
        if (r < 2)
                return r;

        DMERR("Unsupported message sent to DM core: %s", argv[0]);
        return -EINVAL;
}

/*
 * Pass a message to the target that's at the supplied device offset.
 */
static int target_message(struct dm_ioctl *param, size_t param_size)
{
        int r, argc;
        char **argv;
        struct mapped_device *md;
        struct dm_table *table;
        struct dm_target *ti;
        struct dm_target_msg *tmsg = (void *) param + param->data_start;
        size_t maxlen;
        char *result = get_result_buffer(param, param_size, &maxlen);
        int srcu_idx;

        md = find_device(param);
        if (!md)
                return -ENXIO;

        if (tmsg < (struct dm_target_msg *) param->data ||
            invalid_str(tmsg->message, (void *) param + param_size)) {
                DMWARN("Invalid target message parameters.");
                r = -EINVAL;
                goto out;
        }

        r = dm_split_args(&argc, &argv, tmsg->message);
        if (r) {
                DMWARN("Failed to split target message parameters");
                goto out;
        }

        if (!argc) {
                DMWARN("Empty message received.");
                goto out_argv;
        }

        r = message_for_md(md, argc, argv, result, maxlen);
        if (r <= 1)
                goto out_argv;

        table = dm_get_live_table(md, &srcu_idx);
        if (!table)
                goto out_table;

        if (dm_deleting_md(md)) {
                r = -ENXIO;
                goto out_table;
        }

        ti = dm_table_find_target(table, tmsg->sector);
        if (!dm_target_is_valid(ti)) {
                DMWARN("Target message sector outside device.");
                r = -EINVAL;
        } else if (ti->type->message)
                r = ti->type->message(ti, argc, argv);
        else {
                DMWARN("Target type does not support messages");
                r = -EINVAL;
        }

 out_table:
        dm_put_live_table(md, srcu_idx);
 out_argv:
        kfree(argv);
 out:
        if (r >= 0)
                __dev_status(md, param);

        if (r == 1) {
                param->flags |= DM_DATA_OUT_FLAG;
                if (dm_message_test_buffer_overflow(result, maxlen))
                        param->flags |= DM_BUFFER_FULL_FLAG;
                else
                        param->data_size = param->data_start + strlen(result) + 1;
                r = 0;
        }

        dm_put(md);
        return r;
}

/*
 * The ioctl parameter block consists of two parts, a dm_ioctl struct
 * followed by a data buffer.  This flag is set if the second part,
 * which has a variable size, is not used by the function processing
 * the ioctl.
 */
#define IOCTL_FLAGS_NO_PARAMS   1

/*-----------------------------------------------------------------
 * Implementation of open/close/ioctl on the special char
 * device.
 *---------------------------------------------------------------*/
static ioctl_fn lookup_ioctl(unsigned int cmd, int *ioctl_flags)
{
        static struct {
                int cmd;
                int flags;
                ioctl_fn fn;
        } _ioctls[] = {
                {DM_VERSION_CMD, 0, NULL}, /* version is dealt with elsewhere */
                {DM_REMOVE_ALL_CMD, IOCTL_FLAGS_NO_PARAMS, remove_all},
                {DM_LIST_DEVICES_CMD, 0, list_devices},

                {DM_DEV_CREATE_CMD, IOCTL_FLAGS_NO_PARAMS, dev_create},
                {DM_DEV_REMOVE_CMD, IOCTL_FLAGS_NO_PARAMS, dev_remove},
                {DM_DEV_RENAME_CMD, 0, dev_rename},
                {DM_DEV_SUSPEND_CMD, IOCTL_FLAGS_NO_PARAMS, dev_suspend},
                {DM_DEV_STATUS_CMD, IOCTL_FLAGS_NO_PARAMS, dev_status},
                {DM_DEV_WAIT_CMD, 0, dev_wait},

                {DM_TABLE_LOAD_CMD, 0, table_load},
                {DM_TABLE_CLEAR_CMD, IOCTL_FLAGS_NO_PARAMS, table_clear},
                {DM_TABLE_DEPS_CMD, 0, table_deps},
                {DM_TABLE_STATUS_CMD, 0, table_status},

                {DM_LIST_VERSIONS_CMD, 0, list_versions},

                {DM_TARGET_MSG_CMD, 0, target_message},
                {DM_DEV_SET_GEOMETRY_CMD, 0, dev_set_geometry}
        };

        if (unlikely(cmd >= ARRAY_SIZE(_ioctls)))
                return NULL;

        *ioctl_flags = _ioctls[cmd].flags;
        return _ioctls[cmd].fn;
}

/*
 * As well as checking the version compatibility this always
 * copies the kernel interface version out.
 */
static int check_version(unsigned int cmd, struct dm_ioctl __user *user)
{
        uint32_t version[3];
        int r = 0;

        if (copy_from_user(version, user->version, sizeof(version)))
                return -EFAULT;

        if ((DM_VERSION_MAJOR != version[0]) ||
            (DM_VERSION_MINOR < version[1])) {
                DMWARN("ioctl interface mismatch: "
                       "kernel(%u.%u.%u), user(%u.%u.%u), cmd(%d)",
                       DM_VERSION_MAJOR, DM_VERSION_MINOR,
                       DM_VERSION_PATCHLEVEL,
                       version[0], version[1], version[2], cmd);
                r = -EINVAL;
        }

        /*
         * Fill in the kernel version.
         */
        version[0] = DM_VERSION_MAJOR;
        version[1] = DM_VERSION_MINOR;
        version[2] = DM_VERSION_PATCHLEVEL;
        if (copy_to_user(user->version, version, sizeof(version)))
                return -EFAULT;

        return r;
}

#define DM_PARAMS_KMALLOC       0x0001  /* Params alloced with kmalloc */
#define DM_PARAMS_VMALLOC       0x0002  /* Params alloced with vmalloc */
#define DM_WIPE_BUFFER          0x0010  /* Wipe input buffer before returning from ioctl */

static void free_params(struct dm_ioctl *param, size_t param_size, int param_flags)
{
        if (param_flags & DM_WIPE_BUFFER)
                memset(param, 0, param_size);

        if (param_flags & DM_PARAMS_KMALLOC)
                kfree(param);
        if (param_flags & DM_PARAMS_VMALLOC)
                vfree(param);
}

static int copy_params(struct dm_ioctl __user *user, struct dm_ioctl *param_kernel,
                       int ioctl_flags,
                       struct dm_ioctl **param, int *param_flags)
{
        struct dm_ioctl *dmi;
        int secure_data;
        const size_t minimum_data_size = sizeof(*param_kernel) - sizeof(param_kernel->data);

        if (copy_from_user(param_kernel, user, minimum_data_size))
                return -EFAULT;

        if (param_kernel->data_size < minimum_data_size)
                return -EINVAL;

        secure_data = param_kernel->flags & DM_SECURE_DATA_FLAG;

        *param_flags = secure_data ? DM_WIPE_BUFFER : 0;

        if (ioctl_flags & IOCTL_FLAGS_NO_PARAMS) {
                dmi = param_kernel;
                dmi->data_size = minimum_data_size;
                goto data_copied;
        }

        /*
         * Try to avoid low memory issues when a device is suspended.
         * Use kmalloc() rather than vmalloc() when we can.
         */
        dmi = NULL;
        if (param_kernel->data_size <= KMALLOC_MAX_SIZE) {
                dmi = kmalloc(param_kernel->data_size, GFP_NOIO | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);
                if (dmi)
                        *param_flags |= DM_PARAMS_KMALLOC;
        }

        if (!dmi) {
                unsigned noio_flag;
                noio_flag = memalloc_noio_save();
                dmi = __vmalloc(param_kernel->data_size, GFP_NOIO | __GFP_REPEAT | __GFP_HIGH | __GFP_HIGHMEM, PAGE_KERNEL);
                memalloc_noio_restore(noio_flag);
                if (dmi)
                        *param_flags |= DM_PARAMS_VMALLOC;
        }

        if (!dmi) {
                if (secure_data && clear_user(user, param_kernel->data_size))
                        return -EFAULT;
                return -ENOMEM;
        }

        if (copy_from_user(dmi, user, param_kernel->data_size))
                goto bad;

data_copied:
        /*
         * Abort if something changed the ioctl data while it was being copied.
         */
        if (dmi->data_size != param_kernel->data_size) {
                DMERR("rejecting ioctl: data size modified while processing parameters");
                goto bad;
        }

        /* Wipe the user buffer so we do not return it to userspace */
        if (secure_data && clear_user(user, param_kernel->data_size))
                goto bad;

        *param = dmi;
        return 0;

bad:
        free_params(dmi, param_kernel->data_size, *param_flags);

        return -EFAULT;
}

static int validate_params(uint cmd, struct dm_ioctl *param)
{
        /* Always clear this flag */
        param->flags &= ~DM_BUFFER_FULL_FLAG;
        param->flags &= ~DM_UEVENT_GENERATED_FLAG;
        param->flags &= ~DM_SECURE_DATA_FLAG;
        param->flags &= ~DM_DATA_OUT_FLAG;

        /* Ignores parameters */
        if (cmd == DM_REMOVE_ALL_CMD ||
            cmd == DM_LIST_DEVICES_CMD ||
            cmd == DM_LIST_VERSIONS_CMD)
                return 0;

        if ((cmd == DM_DEV_CREATE_CMD)) {
                if (!*param->name) {
                        DMWARN("name not supplied when creating device");
                        return -EINVAL;
                }
        } else if ((*param->uuid && *param->name)) {
                DMWARN("only supply one of name or uuid, cmd(%u)", cmd);
                return -EINVAL;
        }

        /* Ensure strings are terminated */
        param->name[DM_NAME_LEN - 1] = '\0';
        param->uuid[DM_UUID_LEN - 1] = '\0';

        return 0;
}

static int ctl_ioctl(uint command, struct dm_ioctl __user *user)
{
        int r = 0;
        int ioctl_flags;
        int param_flags;
        unsigned int cmd;
        struct dm_ioctl *uninitialized_var(param);
        ioctl_fn fn = NULL;
        size_t input_param_size;
        struct dm_ioctl param_kernel;

        /* only root can play with this */
        if (!capable(CAP_SYS_ADMIN))
                return -EACCES;

        if (_IOC_TYPE(command) != DM_IOCTL)
                return -ENOTTY;

        cmd = _IOC_NR(command);

        /*
         * Check the interface version passed in.  This also
         * writes out the kernel's interface version.
         */
        r = check_version(cmd, user);
        if (r)
                return r;

        /*
         * Nothing more to do for the version command.
         */
        if (cmd == DM_VERSION_CMD)
                return 0;

        fn = lookup_ioctl(cmd, &ioctl_flags);
        if (!fn) {
                DMWARN("dm_ctl_ioctl: unknown command 0x%x", command);
                return -ENOTTY;
        }

        /*
         * Copy the parameters into kernel space.
         */
        r = copy_params(user, &param_kernel, ioctl_flags, &param, &param_flags);

        if (r)
                return r;

        input_param_size = param->data_size;
        r = validate_params(cmd, param);
        if (r)
                goto out;

        param->data_size = sizeof(*param);
        r = fn(param, input_param_size);

        if (unlikely(param->flags & DM_BUFFER_FULL_FLAG) &&
            unlikely(ioctl_flags & IOCTL_FLAGS_NO_PARAMS))
                DMERR("ioctl %d tried to output some data but has IOCTL_FLAGS_NO_PARAMS set", cmd);

        /*
         * Copy the results back to userland.
         */
        if (!r && copy_to_user(user, param, param->data_size))
                r = -EFAULT;

out:
        free_params(param, input_param_size, param_flags);
        return r;
}

static long dm_ctl_ioctl(struct file *file, uint command, ulong u)
{
        return (long)ctl_ioctl(command, (struct dm_ioctl __user *)u);
}

#ifdef CONFIG_COMPAT
static long dm_compat_ctl_ioctl(struct file *file, uint command, ulong u)
{
        return (long)dm_ctl_ioctl(file, command, (ulong) compat_ptr(u));
}
#else
#define dm_compat_ctl_ioctl NULL
#endif

static const struct file_operations _ctl_fops = {
        .open = nonseekable_open,
        .unlocked_ioctl  = dm_ctl_ioctl,
        .compat_ioctl = dm_compat_ctl_ioctl,
        .owner   = THIS_MODULE,
        .llseek  = noop_llseek,
};

static struct miscdevice _dm_misc = {
        .minor          = MAPPER_CTRL_MINOR,
        .name           = DM_NAME,
        .nodename       = DM_DIR "/" DM_CONTROL_NODE,
        .fops           = &_ctl_fops
};

MODULE_ALIAS_MISCDEV(MAPPER_CTRL_MINOR);
MODULE_ALIAS("devname:" DM_DIR "/" DM_CONTROL_NODE);

/*
 * Create misc character device and link to DM_DIR/control.
 */
int __init dm_interface_init(void)
{
        int r;

        r = dm_hash_init();
        if (r)
                return r;

        r = misc_register(&_dm_misc);
        if (r) {
                DMERR("misc_register failed for control device");
                dm_hash_exit();
                return r;
        }

        DMINFO("%d.%d.%d%s initialised: %s", DM_VERSION_MAJOR,
               DM_VERSION_MINOR, DM_VERSION_PATCHLEVEL, DM_VERSION_EXTRA,
               DM_DRIVER_EMAIL);
        return 0;
}

void dm_interface_exit(void)
{
        misc_deregister(&_dm_misc);
        dm_hash_exit();
}

/**
 * dm_copy_name_and_uuid - Copy mapped device name & uuid into supplied buffers
 * @md: Pointer to mapped_device
 * @name: Buffer (size DM_NAME_LEN) for name
 * @uuid: Buffer (size DM_UUID_LEN) for uuid or empty string if uuid not defined
 */
int dm_copy_name_and_uuid(struct mapped_device *md, char *name, char *uuid)
{
        int r = 0;
        struct hash_cell *hc;

        if (!md)
                return -ENXIO;

        mutex_lock(&dm_hash_cells_mutex);
        hc = dm_get_mdptr(md);
        if (!hc || hc->md != md) {
                r = -ENXIO;
                goto out;
        }

        if (name)
                strcpy(name, hc->name);
        if (uuid)
                strcpy(uuid, hc->uuid ? : "");

out:
        mutex_unlock(&dm_hash_cells_mutex);

        return r;
}