drivers/md/dm-exception-store.c

   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 /*
 142  * Round a number up to the nearest 'size' boundary.  size must
 143  * be a power of 2.
 144  */
 145 static ulong round_up(ulong n, ulong size)
 146 {
 147         size--;
 148         return (n + size) & ~size;
 149 }
 150
 151 static int set_chunk_size(struct dm_exception_store *store,
 152                           const char *chunk_size_arg, char **error)
 153 {
 154         unsigned long chunk_size_ulong;
 155         char *value;
 156
 157         chunk_size_ulong = simple_strtoul(chunk_size_arg, &value, 10);
 158         if (*chunk_size_arg == '\0' || *value != '\0') {
 159                 *error = "Invalid chunk size";
 160                 return -EINVAL;
 161         }
 162
 163         if (!chunk_size_ulong) {
 164                 store->chunk_size = store->chunk_mask = store->chunk_shift = 0;
 165                 return 0;
 166         }
 167
 168         /*
 169          * Chunk size must be multiple of page size.  Silently
 170          * round up if it's not.
 171          */
 172         chunk_size_ulong = round_up(chunk_size_ulong, PAGE_SIZE >> 9);
 173
 174         /* Check chunk_size is a power of 2 */
 175         if (!is_power_of_2(chunk_size_ulong)) {
 176                 *error = "Chunk size is not a power of 2";
 177                 return -EINVAL;
 178         }
 179
 180         /* Validate the chunk size against the device block size */
 181         if (chunk_size_ulong % (bdev_logical_block_size(store->cow->bdev) >> 9)) {
 182                 *error = "Chunk size is not a multiple of device blocksize";
 183                 return -EINVAL;
 184         }
 185
 186         store->chunk_size = chunk_size_ulong;
 187         store->chunk_mask = chunk_size_ulong - 1;
 188         store->chunk_shift = ffs(chunk_size_ulong) - 1;
 189
 190         return 0;
 191 }
 192
 193 int dm_exception_store_create(struct dm_target *ti, int argc, char **argv,
 194                               unsigned *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 < 3) {
 203                 ti->error = "Insufficient exception store arguments";
 204                 return -EINVAL;
 205         }
 206
 207         tmp_store = kmalloc(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[1]);
 214         if (persistent == 'P')
 215                 type = get_type("P");
 216         else if (persistent == 'N')
 217                 type = get_type("N");
 218         else {
 219                 ti->error = "Persistent flag is not P or N";
 220                 return -EINVAL;
 221         }
 222
 223         if (!type) {
 224                 ti->error = "Exception store type not recognised";
 225                 r = -EINVAL;
 226                 goto bad_type;
 227         }
 228
 229         tmp_store->type = type;
 230         tmp_store->ti = ti;
 231
 232         r = dm_get_device(ti, argv[0], 0, 0,
 233                           FMODE_READ | FMODE_WRITE, &tmp_store->cow);
 234         if (r) {
 235                 ti->error = "Cannot get COW device";
 236                 goto bad_cow;
 237         }
 238
 239         r = set_chunk_size(tmp_store, argv[2], &ti->error);
 240         if (r)
 241                 goto bad_cow;
 242
 243         r = type->ctr(tmp_store, 0, NULL);
 244         if (r) {
 245                 ti->error = "Exception store type constructor failed";
 246                 goto bad_ctr;
 247         }
 248
 249         *args_used = 3;
 250         *store = tmp_store;
 251         return 0;
 252
 253 bad_ctr:
 254         dm_put_device(ti, tmp_store->cow);
 255 bad_cow:
 256         put_type(type);
 257 bad_type:
 258         kfree(tmp_store);
 259         return r;
 260 }
 261 EXPORT_SYMBOL(dm_exception_store_create);
 262
 263 void dm_exception_store_destroy(struct dm_exception_store *store)
 264 {
 265         store->type->dtr(store);
 266         dm_put_device(store->ti, store->cow);
 267         put_type(store->type);
 268         kfree(store);
 269 }
 270 EXPORT_SYMBOL(dm_exception_store_destroy);
 271
 272 int dm_exception_store_init(void)
 273 {
 274         int r;
 275
 276         r = dm_transient_snapshot_init();
 277         if (r) {
 278                 DMERR("Unable to register transient exception store type.");
 279                 goto transient_fail;
 280         }
 281
 282         r = dm_persistent_snapshot_init();
 283         if (r) {
 284                 DMERR("Unable to register persistent exception store type");
 285                 goto persistent_fail;
 286         }
 287
 288         return 0;
 289
 290 persistent_fail:
 291         dm_persistent_snapshot_exit();
 292 transient_fail:
 293         return r;
 294 }
 295
 296 void dm_exception_store_exit(void)
 297 {
 298         dm_persistent_snapshot_exit();
 299         dm_transient_snapshot_exit();
 300 }