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 } 300