1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Copyright (C) 2001-2002 Sistina Software (UK) Limited. 4 * Copyright (C) 2006-2008 Red Hat GmbH 5 * 6 * This file is released under the GPL. 7 */ 8 9 #include "dm-exception-store.h" 10 11 #include <linux/ctype.h> 12 #include <linux/mm.h> 13 #include <linux/pagemap.h> 14 #include <linux/vmalloc.h> 15 #include <linux/module.h> 16 #include <linux/slab.h> 17 18 #define DM_MSG_PREFIX "snapshot exception stores" 19 20 static LIST_HEAD(_exception_store_types); 21 static DEFINE_SPINLOCK(_lock); 22 23 static struct dm_exception_store_type *__find_exception_store_type(const char *name) 24 { 25 struct dm_exception_store_type *type; 26 27 list_for_each_entry(type, &_exception_store_types, list) 28 if (!strcmp(name, type->name)) 29 return type; 30 31 return NULL; 32 } 33 34 static struct dm_exception_store_type *_get_exception_store_type(const char *name) 35 { 36 struct dm_exception_store_type *type; 37 38 spin_lock(&_lock); 39 40 type = __find_exception_store_type(name); 41 42 if (type && !try_module_get(type->module)) 43 type = NULL; 44 45 spin_unlock(&_lock); 46 47 return type; 48 } 49 50 /* 51 * get_type 52 * @type_name 53 * 54 * Attempt to retrieve the dm_exception_store_type by name. If not already 55 * available, attempt to load the appropriate module. 56 * 57 * Exstore modules are named "dm-exstore-" followed by the 'type_name'. 58 * Modules may contain multiple types. 59 * This function will first try the module "dm-exstore-<type_name>", 60 * then truncate 'type_name' on the last '-' and try again. 61 * 62 * For example, if type_name was "clustered-shared", it would search 63 * 'dm-exstore-clustered-shared' then 'dm-exstore-clustered'. 64 * 65 * 'dm-exception-store-<type_name>' is too long of a name in my 66 * opinion, which is why I've chosen to have the files 67 * containing exception store implementations be 'dm-exstore-<type_name>'. 68 * If you want your module to be autoloaded, you will follow this 69 * naming convention. 70 * 71 * Returns: dm_exception_store_type* on success, NULL on failure 72 */ 73 static struct dm_exception_store_type *get_type(const char *type_name) 74 { 75 char *p, *type_name_dup; 76 struct dm_exception_store_type *type; 77 78 type = _get_exception_store_type(type_name); 79 if (type) 80 return type; 81 82 type_name_dup = kstrdup(type_name, GFP_KERNEL); 83 if (!type_name_dup) { 84 DMERR("No memory left to attempt load for \"%s\"", type_name); 85 return NULL; 86 } 87 88 while (request_module("dm-exstore-%s", type_name_dup) || 89 !(type = _get_exception_store_type(type_name))) { 90 p = strrchr(type_name_dup, '-'); 91 if (!p) 92 break; 93 p[0] = '\0'; 94 } 95 96 if (!type) 97 DMWARN("Module for exstore type \"%s\" not found.", type_name); 98 99 kfree(type_name_dup); 100 101 return type; 102 } 103 104 static void put_type(struct dm_exception_store_type *type) 105 { 106 spin_lock(&_lock); 107 module_put(type->module); 108 spin_unlock(&_lock); 109 } 110 111 int dm_exception_store_type_register(struct dm_exception_store_type *type) 112 { 113 int r = 0; 114 115 spin_lock(&_lock); 116 if (!__find_exception_store_type(type->name)) 117 list_add(&type->list, &_exception_store_types); 118 else 119 r = -EEXIST; 120 spin_unlock(&_lock); 121 122 return r; 123 } 124 EXPORT_SYMBOL(dm_exception_store_type_register); 125 126 int dm_exception_store_type_unregister(struct dm_exception_store_type *type) 127 { 128 spin_lock(&_lock); 129 130 if (!__find_exception_store_type(type->name)) { 131 spin_unlock(&_lock); 132 return -EINVAL; 133 } 134 135 list_del(&type->list); 136 137 spin_unlock(&_lock); 138 139 return 0; 140 } 141 EXPORT_SYMBOL(dm_exception_store_type_unregister); 142 143 static int set_chunk_size(struct dm_exception_store *store, 144 const char *chunk_size_arg, char **error) 145 { 146 unsigned int chunk_size; 147 148 if (kstrtouint(chunk_size_arg, 10, &chunk_size)) { 149 *error = "Invalid chunk size"; 150 return -EINVAL; 151 } 152 153 if (!chunk_size) { 154 store->chunk_size = store->chunk_mask = store->chunk_shift = 0; 155 return 0; 156 } 157 158 return dm_exception_store_set_chunk_size(store, chunk_size, error); 159 } 160 161 int dm_exception_store_set_chunk_size(struct dm_exception_store *store, 162 unsigned int chunk_size, 163 char **error) 164 { 165 /* Check chunk_size is a power of 2 */ 166 if (!is_power_of_2(chunk_size)) { 167 *error = "Chunk size is not a power of 2"; 168 return -EINVAL; 169 } 170 171 /* Validate the chunk size against the device block size */ 172 if (chunk_size % 173 (bdev_logical_block_size(dm_snap_cow(store->snap)->bdev) >> 9) || 174 chunk_size % 175 (bdev_logical_block_size(dm_snap_origin(store->snap)->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); 188 189 return 0; 190 } 191 192 int dm_exception_store_create(struct dm_target *ti, int argc, char **argv, 193 struct dm_snapshot *snap, 194 unsigned int *args_used, 195 struct dm_exception_store **store) 196 { 197 int r = 0; 198 struct dm_exception_store_type *type = NULL; 199 struct dm_exception_store *tmp_store; 200 char persistent; 201 202 if (argc < 2) { 203 ti->error = "Insufficient exception store arguments"; 204 return -EINVAL; 205 } 206 207 tmp_store = kzalloc(sizeof(*tmp_store), GFP_KERNEL); 208 if (!tmp_store) { 209 ti->error = "Exception store allocation failed"; 210 return -ENOMEM; 211 } 212 213 persistent = toupper(*argv[0]); 214 if (persistent == 'P') 215 type = get_type("P"); 216 else if (persistent == 'N') 217 type = get_type("N"); 218 else { 219 ti->error = "Exception store type is not P or N"; 220 r = -EINVAL; 221 goto bad_type; 222 } 223 224 if (!type) { 225 ti->error = "Exception store type not recognised"; 226 r = -EINVAL; 227 goto bad_type; 228 } 229 230 tmp_store->type = type; 231 tmp_store->snap = snap; 232 233 r = set_chunk_size(tmp_store, argv[1], &ti->error); 234 if (r) 235 goto bad; 236 237 r = type->ctr(tmp_store, (strlen(argv[0]) > 1 ? &argv[0][1] : NULL)); 238 if (r) { 239 ti->error = "Exception store type constructor failed"; 240 goto bad; 241 } 242 243 *args_used = 2; 244 *store = tmp_store; 245 return 0; 246 247 bad: 248 put_type(type); 249 bad_type: 250 kfree(tmp_store); 251 return r; 252 } 253 EXPORT_SYMBOL(dm_exception_store_create); 254 255 void dm_exception_store_destroy(struct dm_exception_store *store) 256 { 257 store->type->dtr(store); 258 put_type(store->type); 259 kfree(store); 260 } 261 EXPORT_SYMBOL(dm_exception_store_destroy); 262 263 int dm_exception_store_init(void) 264 { 265 int r; 266 267 r = dm_transient_snapshot_init(); 268 if (r) { 269 DMERR("Unable to register transient exception store type."); 270 goto transient_fail; 271 } 272 273 r = dm_persistent_snapshot_init(); 274 if (r) { 275 DMERR("Unable to register persistent exception store type"); 276 goto persistent_fail; 277 } 278 279 return 0; 280 281 persistent_fail: 282 dm_transient_snapshot_exit(); 283 transient_fail: 284 return r; 285 } 286 287 void dm_exception_store_exit(void) 288 { 289 dm_persistent_snapshot_exit(); 290 dm_transient_snapshot_exit(); 291 } 292