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1// SPDX-License-Identifier: GPL-2.0-only2/*3 * Copyright (C) 2001-2002 Sistina Software (UK) Limited.4 * Copyright (C) 2006-2008 Red Hat GmbH5 *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 20static LIST_HEAD(_exception_store_types);21static DEFINE_SPINLOCK(_lock);22 23static 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 34static 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_type52 * @type_name53 *54 * Attempt to retrieve the dm_exception_store_type by name. If not already55 * 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 search63 * 'dm-exstore-clustered-shared' then 'dm-exstore-clustered'.64 *65 * 'dm-exception-store-<type_name>' is too long of a name in my66 * opinion, which is why I've chosen to have the files67 * containing exception store implementations be 'dm-exstore-<type_name>'.68 * If you want your module to be autoloaded, you will follow this69 * naming convention.70 *71 * Returns: dm_exception_store_type* on success, NULL on failure72 */73static 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 104static 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 111int 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 else119 r = -EEXIST;120 spin_unlock(&_lock);121 122 return r;123}124EXPORT_SYMBOL(dm_exception_store_type_register);125 126int 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}141EXPORT_SYMBOL(dm_exception_store_type_unregister);142 143static 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 161int 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 192int 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 247bad:248 put_type(type);249bad_type:250 kfree(tmp_store);251 return r;252}253EXPORT_SYMBOL(dm_exception_store_create);254 255void dm_exception_store_destroy(struct dm_exception_store *store)256{257 store->type->dtr(store);258 put_type(store->type);259 kfree(store);260}261EXPORT_SYMBOL(dm_exception_store_destroy);262 263int 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 281persistent_fail:282 dm_transient_snapshot_exit();283transient_fail:284 return r;285}286 287void dm_exception_store_exit(void)288{289 dm_persistent_snapshot_exit();290 dm_transient_snapshot_exit();291}292