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 /* 142 * Round a number up to the nearest 'size' boundary. size must 143 * be a power of 2. 144 */ 145 static ulong round_up(ulong n, ulong size) 146 { 147 size--; 148 return (n + size) & ~size; 149 } 150 151 static int set_chunk_size(struct dm_exception_store *store, 152 const char *chunk_size_arg, char **error) 153 { 154 unsigned long chunk_size_ulong; 155 char *value; 156 157 chunk_size_ulong = simple_strtoul(chunk_size_arg, &value, 10); 158 if (*chunk_size_arg == '\0' || *value != '\0') { 159 *error = "Invalid chunk size"; 160 return -EINVAL; 161 } 162 163 if (!chunk_size_ulong) { 164 store->chunk_size = store->chunk_mask = store->chunk_shift = 0; 165 return 0; 166 } 167 168 /* 169 * Chunk size must be multiple of page size. Silently 170 * round up if it's not. 171 */ 172 chunk_size_ulong = round_up(chunk_size_ulong, PAGE_SIZE >> 9); 173 174 return dm_exception_store_set_chunk_size(store, chunk_size_ulong, 175 error); 176 } 177 178 int dm_exception_store_set_chunk_size(struct dm_exception_store *store, 179 unsigned long chunk_size_ulong, 180 char **error) 181 { 182 /* Check chunk_size is a power of 2 */ 183 if (!is_power_of_2(chunk_size_ulong)) { 184 *error = "Chunk size is not a power of 2"; 185 return -EINVAL; 186 } 187 188 /* Validate the chunk size against the device block size */ 189 if (chunk_size_ulong % (bdev_logical_block_size(store->cow->bdev) >> 9)) { 190 *error = "Chunk size is not a multiple of device blocksize"; 191 return -EINVAL; 192 } 193 194 if (chunk_size_ulong > INT_MAX >> SECTOR_SHIFT) { 195 *error = "Chunk size is too high"; 196 return -EINVAL; 197 } 198 199 store->chunk_size = chunk_size_ulong; 200 store->chunk_mask = chunk_size_ulong - 1; 201 store->chunk_shift = ffs(chunk_size_ulong) - 1; 202 203 return 0; 204 } 205 206 int dm_exception_store_create(struct dm_target *ti, int argc, char **argv, 207 unsigned *args_used, 208 struct dm_exception_store **store) 209 { 210 int r = 0; 211 struct dm_exception_store_type *type = NULL; 212 struct dm_exception_store *tmp_store; 213 char persistent; 214 215 if (argc < 3) { 216 ti->error = "Insufficient exception store arguments"; 217 return -EINVAL; 218 } 219 220 tmp_store = kmalloc(sizeof(*tmp_store), GFP_KERNEL); 221 if (!tmp_store) { 222 ti->error = "Exception store allocation failed"; 223 return -ENOMEM; 224 } 225 226 persistent = toupper(*argv[1]); 227 if (persistent == 'P') 228 type = get_type("P"); 229 else if (persistent == 'N') 230 type = get_type("N"); 231 else { 232 ti->error = "Persistent flag is not P or N"; 233 return -EINVAL; 234 } 235 236 if (!type) { 237 ti->error = "Exception store type not recognised"; 238 r = -EINVAL; 239 goto bad_type; 240 } 241 242 tmp_store->type = type; 243 tmp_store->ti = ti; 244 245 r = dm_get_device(ti, argv[0], 0, 0, 246 FMODE_READ | FMODE_WRITE, &tmp_store->cow); 247 if (r) { 248 ti->error = "Cannot get COW device"; 249 goto bad_cow; 250 } 251 252 r = set_chunk_size(tmp_store, argv[2], &ti->error); 253 if (r) 254 goto bad_cow; 255 256 r = type->ctr(tmp_store, 0, NULL); 257 if (r) { 258 ti->error = "Exception store type constructor failed"; 259 goto bad_ctr; 260 } 261 262 *args_used = 3; 263 *store = tmp_store; 264 return 0; 265 266 bad_ctr: 267 dm_put_device(ti, tmp_store->cow); 268 bad_cow: 269 put_type(type); 270 bad_type: 271 kfree(tmp_store); 272 return r; 273 } 274 EXPORT_SYMBOL(dm_exception_store_create); 275 276 void dm_exception_store_destroy(struct dm_exception_store *store) 277 { 278 store->type->dtr(store); 279 dm_put_device(store->ti, store->cow); 280 put_type(store->type); 281 kfree(store); 282 } 283 EXPORT_SYMBOL(dm_exception_store_destroy); 284 285 int dm_exception_store_init(void) 286 { 287 int r; 288 289 r = dm_transient_snapshot_init(); 290 if (r) { 291 DMERR("Unable to register transient exception store type."); 292 goto transient_fail; 293 } 294 295 r = dm_persistent_snapshot_init(); 296 if (r) { 297 DMERR("Unable to register persistent exception store type"); 298 goto persistent_fail; 299 } 300 301 return 0; 302 303 persistent_fail: 304 dm_persistent_snapshot_exit(); 305 transient_fail: 306 return r; 307 } 308 309 void dm_exception_store_exit(void) 310 { 311 dm_persistent_snapshot_exit(); 312 dm_transient_snapshot_exit(); 313 } 314