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/module.h>
  15 #include <linux/slab.h>
  16
  17 #define DM_MSG_PREFIX "snapshot exception stores"
  18
  19 static LIST_HEAD(_exception_store_types);
  20 static DEFINE_SPINLOCK(_lock);
  21
  22 static 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
  33 static 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  */
  72 static 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
 103 static 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
 110 int 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 }
 123 EXPORT_SYMBOL(dm_exception_store_type_register);
 124
 125 int 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 }
 140 EXPORT_SYMBOL(dm_exception_store_type_unregister);
 141
 142 static 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
 165 int 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
 196 int 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
 251 bad:
 252         put_type(type);
 253 bad_type:
 254         kfree(tmp_store);
 255         return r;
 256 }
 257 EXPORT_SYMBOL(dm_exception_store_create);
 258
 259 void dm_exception_store_destroy(struct dm_exception_store *store)
 260 {
 261         store->type->dtr(store);
 262         put_type(store->type);
 263         kfree(store);
 264 }
 265 EXPORT_SYMBOL(dm_exception_store_destroy);
 266
 267 int 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
 285 persistent_fail:
 286         dm_persistent_snapshot_exit();
 287 transient_fail:
 288         return r;
 289 }
 290
 291 void dm_exception_store_exit(void)
 292 {
 293         dm_persistent_snapshot_exit();
 294         dm_transient_snapshot_exit();
 295 }