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