linux/drivers/md/dm-exception-store.c
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   1/*
   2 * Copyright (C) 2001-2002 Sistina Software (UK) Limited.
   3 * Copyright (C) 2006-2008 Red Hat GmbH
   4 *
   5 * This file is released under the GPL.
   6 */
   7
   8#include "dm-exception-store.h"
   9
  10#include <linux/ctype.h>
  11#include <linux/mm.h>
  12#include <linux/pagemap.h>
  13#include <linux/vmalloc.h>
  14#include <linux/module.h>
  15#include <linux/slab.h>
  16
  17#define DM_MSG_PREFIX "snapshot exception stores"
  18
  19static LIST_HEAD(_exception_store_types);
  20static DEFINE_SPINLOCK(_lock);
  21
  22static struct dm_exception_store_type *__find_exception_store_type(const char *name)
  23{
  24        struct dm_exception_store_type *type;
  25
  26        list_for_each_entry(type, &_exception_store_types, list)
  27                if (!strcmp(name, type->name))
  28                        return type;
  29
  30        return NULL;
  31}
  32
  33static struct dm_exception_store_type *_get_exception_store_type(const char *name)
  34{
  35        struct dm_exception_store_type *type;
  36
  37        spin_lock(&_lock);
  38
  39        type = __find_exception_store_type(name);
  40
  41        if (type && !try_module_get(type->module))
  42                type = NULL;
  43
  44        spin_unlock(&_lock);
  45
  46        return type;
  47}
  48
  49/*
  50 * get_type
  51 * @type_name
  52 *
  53 * Attempt to retrieve the dm_exception_store_type by name.  If not already
  54 * available, attempt to load the appropriate module.
  55 *
  56 * Exstore modules are named "dm-exstore-" followed by the 'type_name'.
  57 * Modules may contain multiple types.
  58 * This function will first try the module "dm-exstore-<type_name>",
  59 * then truncate 'type_name' on the last '-' and try again.
  60 *
  61 * For example, if type_name was "clustered-shared", it would search
  62 * 'dm-exstore-clustered-shared' then 'dm-exstore-clustered'.
  63 *
  64 * 'dm-exception-store-<type_name>' is too long of a name in my
  65 * opinion, which is why I've chosen to have the files
  66 * containing exception store implementations be 'dm-exstore-<type_name>'.
  67 * If you want your module to be autoloaded, you will follow this
  68 * naming convention.
  69 *
  70 * Returns: dm_exception_store_type* on success, NULL on failure
  71 */
  72static struct dm_exception_store_type *get_type(const char *type_name)
  73{
  74        char *p, *type_name_dup;
  75        struct dm_exception_store_type *type;
  76
  77        type = _get_exception_store_type(type_name);
  78        if (type)
  79                return type;
  80
  81        type_name_dup = kstrdup(type_name, GFP_KERNEL);
  82        if (!type_name_dup) {
  83                DMERR("No memory left to attempt load for \"%s\"", type_name);
  84                return NULL;
  85        }
  86
  87        while (request_module("dm-exstore-%s", type_name_dup) ||
  88               !(type = _get_exception_store_type(type_name))) {
  89                p = strrchr(type_name_dup, '-');
  90                if (!p)
  91                        break;
  92                p[0] = '\0';
  93        }
  94
  95        if (!type)
  96                DMWARN("Module for exstore type \"%s\" not found.", type_name);
  97
  98        kfree(type_name_dup);
  99
 100        return type;
 101}
 102
 103static void put_type(struct dm_exception_store_type *type)
 104{
 105        spin_lock(&_lock);
 106        module_put(type->module);
 107        spin_unlock(&_lock);
 108}
 109
 110int dm_exception_store_type_register(struct dm_exception_store_type *type)
 111{
 112        int r = 0;
 113
 114        spin_lock(&_lock);
 115        if (!__find_exception_store_type(type->name))
 116                list_add(&type->list, &_exception_store_types);
 117        else
 118                r = -EEXIST;
 119        spin_unlock(&_lock);
 120
 121        return r;
 122}
 123EXPORT_SYMBOL(dm_exception_store_type_register);
 124
 125int dm_exception_store_type_unregister(struct dm_exception_store_type *type)
 126{
 127        spin_lock(&_lock);
 128
 129        if (!__find_exception_store_type(type->name)) {
 130                spin_unlock(&_lock);
 131                return -EINVAL;
 132        }
 133
 134        list_del(&type->list);
 135
 136        spin_unlock(&_lock);
 137
 138        return 0;
 139}
 140EXPORT_SYMBOL(dm_exception_store_type_unregister);
 141
 142static int set_chunk_size(struct dm_exception_store *store,
 143                          const char *chunk_size_arg, char **error)
 144{
 145        unsigned chunk_size;
 146
 147        if (kstrtouint(chunk_size_arg, 10, &chunk_size)) {
 148                *error = "Invalid chunk size";
 149                return -EINVAL;
 150        }
 151
 152        if (!chunk_size) {
 153                store->chunk_size = store->chunk_mask = store->chunk_shift = 0;
 154                return 0;
 155        }
 156
 157        return dm_exception_store_set_chunk_size(store, chunk_size, error);
 158}
 159
 160int dm_exception_store_set_chunk_size(struct dm_exception_store *store,
 161                                      unsigned chunk_size,
 162                                      char **error)
 163{
 164        /* Check chunk_size is a power of 2 */
 165        if (!is_power_of_2(chunk_size)) {
 166                *error = "Chunk size is not a power of 2";
 167                return -EINVAL;
 168        }
 169
 170        /* Validate the chunk size against the device block size */
 171        if (chunk_size %
 172            (bdev_logical_block_size(dm_snap_cow(store->snap)->bdev) >> 9) ||
 173            chunk_size %
 174            (bdev_logical_block_size(dm_snap_origin(store->snap)->bdev) >> 9)) {
 175                *error = "Chunk size is not a multiple of device blocksize";
 176                return -EINVAL;
 177        }
 178
 179        if (chunk_size > INT_MAX >> SECTOR_SHIFT) {
 180                *error = "Chunk size is too high";
 181                return -EINVAL;
 182        }
 183
 184        store->chunk_size = chunk_size;
 185        store->chunk_mask = chunk_size - 1;
 186        store->chunk_shift = ffs(chunk_size) - 1;
 187
 188        return 0;
 189}
 190
 191int dm_exception_store_create(struct dm_target *ti, int argc, char **argv,
 192                              struct dm_snapshot *snap,
 193                              unsigned *args_used,
 194                              struct dm_exception_store **store)
 195{
 196        int r = 0;
 197        struct dm_exception_store_type *type = NULL;
 198        struct dm_exception_store *tmp_store;
 199        char persistent;
 200
 201        if (argc < 2) {
 202                ti->error = "Insufficient exception store arguments";
 203                return -EINVAL;
 204        }
 205
 206        tmp_store = kmalloc(sizeof(*tmp_store), GFP_KERNEL);
 207        if (!tmp_store) {
 208                ti->error = "Exception store allocation failed";
 209                return -ENOMEM;
 210        }
 211
 212        persistent = toupper(*argv[0]);
 213        if (persistent == 'P')
 214                type = get_type("P");
 215        else if (persistent == 'N')
 216                type = get_type("N");
 217        else {
 218                ti->error = "Persistent flag is not P or N";
 219                r = -EINVAL;
 220                goto bad_type;
 221        }
 222
 223        if (!type) {
 224                ti->error = "Exception store type not recognised";
 225                r = -EINVAL;
 226                goto bad_type;
 227        }
 228
 229        tmp_store->type = type;
 230        tmp_store->snap = snap;
 231
 232        r = set_chunk_size(tmp_store, argv[1], &ti->error);
 233        if (r)
 234                goto bad;
 235
 236        r = type->ctr(tmp_store, 0, NULL);
 237        if (r) {
 238                ti->error = "Exception store type constructor failed";
 239                goto bad;
 240        }
 241
 242        *args_used = 2;
 243        *store = tmp_store;
 244        return 0;
 245
 246bad:
 247        put_type(type);
 248bad_type:
 249        kfree(tmp_store);
 250        return r;
 251}
 252EXPORT_SYMBOL(dm_exception_store_create);
 253
 254void dm_exception_store_destroy(struct dm_exception_store *store)
 255{
 256        store->type->dtr(store);
 257        put_type(store->type);
 258        kfree(store);
 259}
 260EXPORT_SYMBOL(dm_exception_store_destroy);
 261
 262int dm_exception_store_init(void)
 263{
 264        int r;
 265
 266        r = dm_transient_snapshot_init();
 267        if (r) {
 268                DMERR("Unable to register transient exception store type.");
 269                goto transient_fail;
 270        }
 271
 272        r = dm_persistent_snapshot_init();
 273        if (r) {
 274                DMERR("Unable to register persistent exception store type");
 275                goto persistent_fail;
 276        }
 277
 278        return 0;
 279
 280persistent_fail:
 281        dm_transient_snapshot_exit();
 282transient_fail:
 283        return r;
 284}
 285
 286void dm_exception_store_exit(void)
 287{
 288        dm_persistent_snapshot_exit();
 289        dm_transient_snapshot_exit();
 290}
 291
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