drivers/md/dm-exception-store.c

   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/slab.h>
  15
  16 #define DM_MSG_PREFIX "snapshot exception stores"
  17
  18 static LIST_HEAD(_exception_store_types);
  19 static DEFINE_SPINLOCK(_lock);
  20
  21 static struct dm_exception_store_type *__find_exception_store_type(const char *name)
  22 {
  23         struct dm_exception_store_type *type;
  24
  25         list_for_each_entry(type, &_exception_store_types, list)
  26                 if (!strcmp(name, type->name))
  27                         return type;
  28
  29         return NULL;
  30 }
  31
  32 static struct dm_exception_store_type *_get_exception_store_type(const char *name)
  33 {
  34         struct dm_exception_store_type *type;
  35
  36         spin_lock(&_lock);
  37
  38         type = __find_exception_store_type(name);
  39
  40         if (type && !try_module_get(type->module))
  41                 type = NULL;
  42
  43         spin_unlock(&_lock);
  44
  45         return type;
  46 }
  47
  48 /*
  49  * get_type
  50  * @type_name
  51  *
  52  * Attempt to retrieve the dm_exception_store_type by name.  If not already
  53  * available, attempt to load the appropriate module.
  54  *
  55  * Exstore modules are named "dm-exstore-" followed by the 'type_name'.
  56  * Modules may contain multiple types.
  57  * This function will first try the module "dm-exstore-<type_name>",
  58  * then truncate 'type_name' on the last '-' and try again.
  59  *
  60  * For example, if type_name was "clustered-shared", it would search
  61  * 'dm-exstore-clustered-shared' then 'dm-exstore-clustered'.
  62  *
  63  * 'dm-exception-store-<type_name>' is too long of a name in my
  64  * opinion, which is why I've chosen to have the files
  65  * containing exception store implementations be 'dm-exstore-<type_name>'.
  66  * If you want your module to be autoloaded, you will follow this
  67  * naming convention.
  68  *
  69  * Returns: dm_exception_store_type* on success, NULL on failure
  70  */
  71 static struct dm_exception_store_type *get_type(const char *type_name)
  72 {
  73         char *p, *type_name_dup;
  74         struct dm_exception_store_type *type;
  75
  76         type = _get_exception_store_type(type_name);
  77         if (type)
  78                 return type;
  79
  80         type_name_dup = kstrdup(type_name, GFP_KERNEL);
  81         if (!type_name_dup) {
  82                 DMERR("No memory left to attempt load for \"%s\"", type_name);
  83                 return NULL;
  84         }
  85
  86         while (request_module("dm-exstore-%s", type_name_dup) ||
  87                !(type = _get_exception_store_type(type_name))) {
  88                 p = strrchr(type_name_dup, '-');
  89                 if (!p)
  90                         break;
  91                 p[0] = '\0';
  92         }
  93
  94         if (!type)
  95                 DMWARN("Module for exstore type \"%s\" not found.", type_name);
  96
  97         kfree(type_name_dup);
  98
  99         return type;
 100 }
 101
 102 static void put_type(struct dm_exception_store_type *type)
 103 {
 104         spin_lock(&_lock);
 105         module_put(type->module);
 106         spin_unlock(&_lock);
 107 }
 108
 109 int dm_exception_store_type_register(struct dm_exception_store_type *type)
 110 {
 111         int r = 0;
 112
 113         spin_lock(&_lock);
 114         if (!__find_exception_store_type(type->name))
 115                 list_add(&type->list, &_exception_store_types);
 116         else
 117                 r = -EEXIST;
 118         spin_unlock(&_lock);
 119
 120         return r;
 121 }
 122 EXPORT_SYMBOL(dm_exception_store_type_register);
 123
 124 int dm_exception_store_type_unregister(struct dm_exception_store_type *type)
 125 {
 126         spin_lock(&_lock);
 127
 128         if (!__find_exception_store_type(type->name)) {
 129                 spin_unlock(&_lock);
 130                 return -EINVAL;
 131         }
 132
 133         list_del(&type->list);
 134
 135         spin_unlock(&_lock);
 136
 137         return 0;
 138 }
 139 EXPORT_SYMBOL(dm_exception_store_type_unregister);
 140
 141 static int set_chunk_size(struct dm_exception_store *store,
 142                           const char *chunk_size_arg, char **error)
 143 {
 144         unsigned long chunk_size_ulong;
 145         char *value;
 146
 147         chunk_size_ulong = simple_strtoul(chunk_size_arg, &value, 10);
 148         if (*chunk_size_arg == '\0' || *value != '\0' ||
 149             chunk_size_ulong > UINT_MAX) {
 150                 *error = "Invalid chunk size";
 151                 return -EINVAL;
 152         }
 153
 154         if (!chunk_size_ulong) {
 155                 store->chunk_size = store->chunk_mask = store->chunk_shift = 0;
 156                 return 0;
 157         }
 158
 159         return dm_exception_store_set_chunk_size(store,
 160                                                  (unsigned) chunk_size_ulong,
 161                                                  error);
 162 }
 163
 164 int dm_exception_store_set_chunk_size(struct dm_exception_store *store,
 165                                       unsigned chunk_size,
 166                                       char **error)
 167 {
 168         /* Check chunk_size is a power of 2 */
 169         if (!is_power_of_2(chunk_size)) {
 170                 *error = "Chunk size is not a power of 2";
 171                 return -EINVAL;
 172         }
 173
 174         /* Validate the chunk size against the device block size */
 175         if (chunk_size % (bdev_logical_block_size(store->cow->bdev) >> 9)) {
 176                 *error = "Chunk size is not a multiple of device blocksize";
 177                 return -EINVAL;
 178         }
 179
 180         if (chunk_size > INT_MAX >> SECTOR_SHIFT) {
 181                 *error = "Chunk size is too high";
 182                 return -EINVAL;
 183         }
 184
 185         store->chunk_size = chunk_size;
 186         store->chunk_mask = chunk_size - 1;
 187         store->chunk_shift = ffs(chunk_size) - 1;
 188
 189         return 0;
 190 }
 191
 192 int dm_exception_store_create(struct dm_target *ti, int argc, char **argv,
 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 < 3) {
 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[1]);
 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                 return -EINVAL;
 220         }
 221
 222         if (!type) {
 223                 ti->error = "Exception store type not recognised";
 224                 r = -EINVAL;
 225                 goto bad_type;
 226         }
 227
 228         tmp_store->type = type;
 229         tmp_store->ti = ti;
 230
 231         r = dm_get_device(ti, argv[0], 0, 0,
 232                           FMODE_READ | FMODE_WRITE, &tmp_store->cow);
 233         if (r) {
 234                 ti->error = "Cannot get COW device";
 235                 goto bad_cow;
 236         }
 237
 238         r = set_chunk_size(tmp_store, argv[2], &ti->error);
 239         if (r)
 240                 goto bad_ctr;
 241
 242         r = type->ctr(tmp_store, 0, NULL);
 243         if (r) {
 244                 ti->error = "Exception store type constructor failed";
 245                 goto bad_ctr;
 246         }
 247
 248         *args_used = 3;
 249         *store = tmp_store;
 250         return 0;
 251
 252 bad_ctr:
 253         dm_put_device(ti, tmp_store->cow);
 254 bad_cow:
 255         put_type(type);
 256 bad_type:
 257         kfree(tmp_store);
 258         return r;
 259 }
 260 EXPORT_SYMBOL(dm_exception_store_create);
 261
 262 void dm_exception_store_destroy(struct dm_exception_store *store)
 263 {
 264         store->type->dtr(store);
 265         dm_put_device(store->ti, store->cow);
 266         put_type(store->type);
 267         kfree(store);
 268 }
 269 EXPORT_SYMBOL(dm_exception_store_destroy);
 270
 271 int dm_exception_store_init(void)
 272 {
 273         int r;
 274
 275         r = dm_transient_snapshot_init();
 276         if (r) {
 277                 DMERR("Unable to register transient exception store type.");
 278                 goto transient_fail;
 279         }
 280
 281         r = dm_persistent_snapshot_init();
 282         if (r) {
 283                 DMERR("Unable to register persistent exception store type");
 284                 goto persistent_fail;
 285         }
 286
 287         return 0;
 288
 289 persistent_fail:
 290         dm_persistent_snapshot_exit();
 291 transient_fail:
 292         return r;
 293 }
 294
 295 void dm_exception_store_exit(void)
 296 {
 297         dm_persistent_snapshot_exit();
 298         dm_transient_snapshot_exit();
 299 }