drivers/md/dm-exception-store.c

   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 }