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 long chunk_size_ulong;
 146        char *value;
 147
 148        chunk_size_ulong = simple_strtoul(chunk_size_arg, &value, 10);
 149        if (*chunk_size_arg == '\0' || *value != '\0' ||
 150            chunk_size_ulong > UINT_MAX) {
 151                *error = "Invalid chunk size";
 152                return -EINVAL;
 153        }
 154
 155        if (!chunk_size_ulong) {
 156                store->chunk_size = store->chunk_mask = store->chunk_shift = 0;
 157                return 0;
 158        }
 159
 160        return dm_exception_store_set_chunk_size(store,
 161                                                 (unsigned) chunk_size_ulong,
 162                                                 error);
 163}
 164
 165int dm_exception_store_set_chunk_size(struct dm_exception_store *store,
 166                                      unsigned chunk_size,
 167                                      char **error)
 168{
 169        /* Check chunk_size is a power of 2 */
 170        if (!is_power_of_2(chunk_size)) {
 171                *error = "Chunk size is not a power of 2";
 172                return -EINVAL;
 173        }
 174
 175        /* Validate the chunk size against the device block size */
 176        if (chunk_size %
 177            (bdev_logical_block_size(dm_snap_cow(store->snap)->bdev) >> 9) ||
 178            chunk_size %
 179            (bdev_logical_block_size(dm_snap_origin(store->snap)->bdev) >> 9)) {
 180                *error = "Chunk size is not a multiple of device blocksize";
 181                return -EINVAL;
 182        }
 183
 184        if (chunk_size > INT_MAX >> SECTOR_SHIFT) {
 185                *error = "Chunk size is too high";
 186                return -EINVAL;
 187        }
 188
 189        store->chunk_size = chunk_size;
 190        store->chunk_mask = chunk_size - 1;
 191        store->chunk_shift = ffs(chunk_size) - 1;
 192
 193        return 0;
 194}
 195
 196int dm_exception_store_create(struct dm_target *ti, int argc, char **argv,
 197                              struct dm_snapshot *snap,
 198                              unsigned *args_used,
 199                              struct dm_exception_store **store)
 200{
 201        int r = 0;
 202        struct dm_exception_store_type *type = NULL;
 203        struct dm_exception_store *tmp_store;
 204        char persistent;
 205
 206        if (argc < 2) {
 207                ti->error = "Insufficient exception store arguments";
 208                return -EINVAL;
 209        }
 210
 211        tmp_store = kmalloc(sizeof(*tmp_store), GFP_KERNEL);
 212        if (!tmp_store) {
 213                ti->error = "Exception store allocation failed";
 214                return -ENOMEM;
 215        }
 216
 217        persistent = toupper(*argv[0]);
 218        if (persistent == 'P')
 219                type = get_type("P");
 220        else if (persistent == 'N')
 221                type = get_type("N");
 222        else {
 223                ti->error = "Persistent flag is not P or N";
 224                r = -EINVAL;
 225                goto bad_type;
 226        }
 227
 228        if (!type) {
 229                ti->error = "Exception store type not recognised";
 230                r = -EINVAL;
 231                goto bad_type;
 232        }
 233
 234        tmp_store->type = type;
 235        tmp_store->snap = snap;
 236
 237        r = set_chunk_size(tmp_store, argv[1], &ti->error);
 238        if (r)
 239                goto bad;
 240
 241        r = type->ctr(tmp_store, 0, NULL);
 242        if (r) {
 243                ti->error = "Exception store type constructor failed";
 244                goto bad;
 245        }
 246
 247        *args_used = 2;
 248        *store = tmp_store;
 249        return 0;
 250
 251bad:
 252        put_type(type);
 253bad_type:
 254        kfree(tmp_store);
 255        return r;
 256}
 257EXPORT_SYMBOL(dm_exception_store_create);
 258
 259void dm_exception_store_destroy(struct dm_exception_store *store)
 260{
 261        store->type->dtr(store);
 262        put_type(store->type);
 263        kfree(store);
 264}
 265EXPORT_SYMBOL(dm_exception_store_destroy);
 266
 267int dm_exception_store_init(void)
 268{
 269        int r;
 270
 271        r = dm_transient_snapshot_init();
 272        if (r) {
 273                DMERR("Unable to register transient exception store type.");
 274                goto transient_fail;
 275        }
 276
 277        r = dm_persistent_snapshot_init();
 278        if (r) {
 279                DMERR("Unable to register persistent exception store type");
 280                goto persistent_fail;
 281        }
 282
 283        return 0;
 284
 285persistent_fail:
 286        dm_transient_snapshot_exit();
 287transient_fail:
 288        return r;
 289}
 290
 291void dm_exception_store_exit(void)
 292{
 293        dm_persistent_snapshot_exit();
 294        dm_transient_snapshot_exit();
 295}
 296