drivers/md/persistent-data/dm-transaction-manager.c

   1 /*
   2  * Copyright (C) 2011 Red Hat, Inc.
   3  *
   4  * This file is released under the GPL.
   5  */
   6 #include "dm-transaction-manager.h"
   7 #include "dm-space-map.h"
   8 #include "dm-space-map-disk.h"
   9 #include "dm-space-map-metadata.h"
  10 #include "dm-persistent-data-internal.h"
  11
  12 #include <linux/export.h>
  13 #include <linux/mutex.h>
  14 #include <linux/hash.h>
  15 #include <linux/slab.h>
  16 #include <linux/device-mapper.h>
  17
  18 #define DM_MSG_PREFIX "transaction manager"
  19
  20 /*----------------------------------------------------------------*/
  21
  22 #define PREFETCH_SIZE 128
  23 #define PREFETCH_BITS 7
  24 #define PREFETCH_SENTINEL ((dm_block_t) -1ULL)
  25
  26 struct prefetch_set {
  27         struct mutex lock;
  28         dm_block_t blocks[PREFETCH_SIZE];
  29 };
  30
  31 static unsigned prefetch_hash(dm_block_t b)
  32 {
  33         return hash_64(b, PREFETCH_BITS);
  34 }
  35
  36 static void prefetch_wipe(struct prefetch_set *p)
  37 {
  38         unsigned i;
  39         for (i = 0; i < PREFETCH_SIZE; i++)
  40                 p->blocks[i] = PREFETCH_SENTINEL;
  41 }
  42
  43 static void prefetch_init(struct prefetch_set *p)
  44 {
  45         mutex_init(&p->lock);
  46         prefetch_wipe(p);
  47 }
  48
  49 static void prefetch_add(struct prefetch_set *p, dm_block_t b)
  50 {
  51         unsigned h = prefetch_hash(b);
  52
  53         mutex_lock(&p->lock);
  54         if (p->blocks[h] == PREFETCH_SENTINEL)
  55                 p->blocks[h] = b;
  56
  57         mutex_unlock(&p->lock);
  58 }
  59
  60 static void prefetch_issue(struct prefetch_set *p, struct dm_block_manager *bm)
  61 {
  62         unsigned i;
  63
  64         mutex_lock(&p->lock);
  65
  66         for (i = 0; i < PREFETCH_SIZE; i++)
  67                 if (p->blocks[i] != PREFETCH_SENTINEL) {
  68                         dm_bm_prefetch(bm, p->blocks[i]);
  69                         p->blocks[i] = PREFETCH_SENTINEL;
  70                 }
  71
  72         mutex_unlock(&p->lock);
  73 }
  74
  75 /*----------------------------------------------------------------*/
  76
  77 struct shadow_info {
  78         struct hlist_node hlist;
  79         dm_block_t where;
  80 };
  81
  82 /*
  83  * It would be nice if we scaled with the size of transaction.
  84  */
  85 #define DM_HASH_SIZE 256
  86 #define DM_HASH_MASK (DM_HASH_SIZE - 1)
  87
  88 struct dm_transaction_manager {
  89         int is_clone;
  90         struct dm_transaction_manager *real;
  91
  92         struct dm_block_manager *bm;
  93         struct dm_space_map *sm;
  94
  95         spinlock_t lock;
  96         struct hlist_head buckets[DM_HASH_SIZE];
  97
  98         struct prefetch_set prefetches;
  99 };
 100
 101 /*----------------------------------------------------------------*/
 102
 103 static int is_shadow(struct dm_transaction_manager *tm, dm_block_t b)
 104 {
 105         int r = 0;
 106         unsigned bucket = dm_hash_block(b, DM_HASH_MASK);
 107         struct shadow_info *si;
 108
 109         spin_lock(&tm->lock);
 110         hlist_for_each_entry(si, tm->buckets + bucket, hlist)
 111                 if (si->where == b) {
 112                         r = 1;
 113                         break;
 114                 }
 115         spin_unlock(&tm->lock);
 116
 117         return r;
 118 }
 119
 120 /*
 121  * This can silently fail if there's no memory.  We're ok with this since
 122  * creating redundant shadows causes no harm.
 123  */
 124 static void insert_shadow(struct dm_transaction_manager *tm, dm_block_t b)
 125 {
 126         unsigned bucket;
 127         struct shadow_info *si;
 128
 129         si = kmalloc(sizeof(*si), GFP_NOIO);
 130         if (si) {
 131                 si->where = b;
 132                 bucket = dm_hash_block(b, DM_HASH_MASK);
 133                 spin_lock(&tm->lock);
 134                 hlist_add_head(&si->hlist, tm->buckets + bucket);
 135                 spin_unlock(&tm->lock);
 136         }
 137 }
 138
 139 static void wipe_shadow_table(struct dm_transaction_manager *tm)
 140 {
 141         struct shadow_info *si;
 142         struct hlist_node *tmp;
 143         struct hlist_head *bucket;
 144         int i;
 145
 146         spin_lock(&tm->lock);
 147         for (i = 0; i < DM_HASH_SIZE; i++) {
 148                 bucket = tm->buckets + i;
 149                 hlist_for_each_entry_safe(si, tmp, bucket, hlist)
 150                         kfree(si);
 151
 152                 INIT_HLIST_HEAD(bucket);
 153         }
 154
 155         spin_unlock(&tm->lock);
 156 }
 157
 158 /*----------------------------------------------------------------*/
 159
 160 static struct dm_transaction_manager *dm_tm_create(struct dm_block_manager *bm,
 161                                                    struct dm_space_map *sm)
 162 {
 163         int i;
 164         struct dm_transaction_manager *tm;
 165
 166         tm = kmalloc(sizeof(*tm), GFP_KERNEL);
 167         if (!tm)
 168                 return ERR_PTR(-ENOMEM);
 169
 170         tm->is_clone = 0;
 171         tm->real = NULL;
 172         tm->bm = bm;
 173         tm->sm = sm;
 174
 175         spin_lock_init(&tm->lock);
 176         for (i = 0; i < DM_HASH_SIZE; i++)
 177                 INIT_HLIST_HEAD(tm->buckets + i);
 178
 179         prefetch_init(&tm->prefetches);
 180
 181         return tm;
 182 }
 183
 184 struct dm_transaction_manager *dm_tm_create_non_blocking_clone(struct dm_transaction_manager *real)
 185 {
 186         struct dm_transaction_manager *tm;
 187
 188         tm = kmalloc(sizeof(*tm), GFP_KERNEL);
 189         if (tm) {
 190                 tm->is_clone = 1;
 191                 tm->real = real;
 192         }
 193
 194         return tm;
 195 }
 196 EXPORT_SYMBOL_GPL(dm_tm_create_non_blocking_clone);
 197
 198 void dm_tm_destroy(struct dm_transaction_manager *tm)
 199 {
 200         if (!tm->is_clone)
 201                 wipe_shadow_table(tm);
 202
 203         kfree(tm);
 204 }
 205 EXPORT_SYMBOL_GPL(dm_tm_destroy);
 206
 207 int dm_tm_pre_commit(struct dm_transaction_manager *tm)
 208 {
 209         int r;
 210
 211         if (tm->is_clone)
 212                 return -EWOULDBLOCK;
 213
 214         r = dm_sm_commit(tm->sm);
 215         if (r < 0)
 216                 return r;
 217
 218         return dm_bm_flush(tm->bm);
 219 }
 220 EXPORT_SYMBOL_GPL(dm_tm_pre_commit);
 221
 222 int dm_tm_commit(struct dm_transaction_manager *tm, struct dm_block *root)
 223 {
 224         if (tm->is_clone)
 225                 return -EWOULDBLOCK;
 226
 227         wipe_shadow_table(tm);
 228         dm_bm_unlock(root);
 229
 230         return dm_bm_flush(tm->bm);
 231 }
 232 EXPORT_SYMBOL_GPL(dm_tm_commit);
 233
 234 int dm_tm_new_block(struct dm_transaction_manager *tm,
 235                     struct dm_block_validator *v,
 236                     struct dm_block **result)
 237 {
 238         int r;
 239         dm_block_t new_block;
 240
 241         if (tm->is_clone)
 242                 return -EWOULDBLOCK;
 243
 244         r = dm_sm_new_block(tm->sm, &new_block);
 245         if (r < 0)
 246                 return r;
 247
 248         r = dm_bm_write_lock_zero(tm->bm, new_block, v, result);
 249         if (r < 0) {
 250                 dm_sm_dec_block(tm->sm, new_block);
 251                 return r;
 252         }
 253
 254         /*
 255          * New blocks count as shadows in that they don't need to be
 256          * shadowed again.
 257          */
 258         insert_shadow(tm, new_block);
 259
 260         return 0;
 261 }
 262
 263 static int __shadow_block(struct dm_transaction_manager *tm, dm_block_t orig,
 264                           struct dm_block_validator *v,
 265                           struct dm_block **result)
 266 {
 267         int r;
 268         dm_block_t new;
 269         struct dm_block *orig_block;
 270
 271         r = dm_sm_new_block(tm->sm, &new);
 272         if (r < 0)
 273                 return r;
 274
 275         r = dm_sm_dec_block(tm->sm, orig);
 276         if (r < 0)
 277                 return r;
 278
 279         r = dm_bm_read_lock(tm->bm, orig, v, &orig_block);
 280         if (r < 0)
 281                 return r;
 282
 283         /*
 284          * It would be tempting to use dm_bm_unlock_move here, but some
 285          * code, such as the space maps, keeps using the old data structures
 286          * secure in the knowledge they won't be changed until the next
 287          * transaction.  Using unlock_move would force a synchronous read
 288          * since the old block would no longer be in the cache.
 289          */
 290         r = dm_bm_write_lock_zero(tm->bm, new, v, result);
 291         if (r) {
 292                 dm_bm_unlock(orig_block);
 293                 return r;
 294         }
 295
 296         memcpy(dm_block_data(*result), dm_block_data(orig_block),
 297                dm_bm_block_size(tm->bm));
 298
 299         dm_bm_unlock(orig_block);
 300         return r;
 301 }
 302
 303 int dm_tm_shadow_block(struct dm_transaction_manager *tm, dm_block_t orig,
 304                        struct dm_block_validator *v, struct dm_block **result,
 305                        int *inc_children)
 306 {
 307         int r;
 308
 309         if (tm->is_clone)
 310                 return -EWOULDBLOCK;
 311
 312         r = dm_sm_count_is_more_than_one(tm->sm, orig, inc_children);
 313         if (r < 0)
 314                 return r;
 315
 316         if (is_shadow(tm, orig) && !*inc_children)
 317                 return dm_bm_write_lock(tm->bm, orig, v, result);
 318
 319         r = __shadow_block(tm, orig, v, result);
 320         if (r < 0)
 321                 return r;
 322         insert_shadow(tm, dm_block_location(*result));
 323
 324         return r;
 325 }
 326 EXPORT_SYMBOL_GPL(dm_tm_shadow_block);
 327
 328 int dm_tm_read_lock(struct dm_transaction_manager *tm, dm_block_t b,
 329                     struct dm_block_validator *v,
 330                     struct dm_block **blk)
 331 {
 332         if (tm->is_clone) {
 333                 int r = dm_bm_read_try_lock(tm->real->bm, b, v, blk);
 334
 335                 if (r == -EWOULDBLOCK)
 336                         prefetch_add(&tm->real->prefetches, b);
 337
 338                 return r;
 339         }
 340
 341         return dm_bm_read_lock(tm->bm, b, v, blk);
 342 }
 343 EXPORT_SYMBOL_GPL(dm_tm_read_lock);
 344
 345 int dm_tm_unlock(struct dm_transaction_manager *tm, struct dm_block *b)
 346 {
 347         return dm_bm_unlock(b);
 348 }
 349 EXPORT_SYMBOL_GPL(dm_tm_unlock);
 350
 351 void dm_tm_inc(struct dm_transaction_manager *tm, dm_block_t b)
 352 {
 353         /*
 354          * The non-blocking clone doesn't support this.
 355          */
 356         BUG_ON(tm->is_clone);
 357
 358         dm_sm_inc_block(tm->sm, b);
 359 }
 360 EXPORT_SYMBOL_GPL(dm_tm_inc);
 361
 362 void dm_tm_dec(struct dm_transaction_manager *tm, dm_block_t b)
 363 {
 364         /*
 365          * The non-blocking clone doesn't support this.
 366          */
 367         BUG_ON(tm->is_clone);
 368
 369         dm_sm_dec_block(tm->sm, b);
 370 }
 371 EXPORT_SYMBOL_GPL(dm_tm_dec);
 372
 373 int dm_tm_ref(struct dm_transaction_manager *tm, dm_block_t b,
 374               uint32_t *result)
 375 {
 376         if (tm->is_clone)
 377                 return -EWOULDBLOCK;
 378
 379         return dm_sm_get_count(tm->sm, b, result);
 380 }
 381
 382 struct dm_block_manager *dm_tm_get_bm(struct dm_transaction_manager *tm)
 383 {
 384         return tm->bm;
 385 }
 386
 387 void dm_tm_issue_prefetches(struct dm_transaction_manager *tm)
 388 {
 389         prefetch_issue(&tm->prefetches, tm->bm);
 390 }
 391 EXPORT_SYMBOL_GPL(dm_tm_issue_prefetches);
 392
 393 /*----------------------------------------------------------------*/
 394
 395 static int dm_tm_create_internal(struct dm_block_manager *bm,
 396                                  dm_block_t sb_location,
 397                                  struct dm_transaction_manager **tm,
 398                                  struct dm_space_map **sm,
 399                                  int create,
 400                                  void *sm_root, size_t sm_len)
 401 {
 402         int r;
 403
 404         *sm = dm_sm_metadata_init();
 405         if (IS_ERR(*sm))
 406                 return PTR_ERR(*sm);
 407
 408         *tm = dm_tm_create(bm, *sm);
 409         if (IS_ERR(*tm)) {
 410                 dm_sm_destroy(*sm);
 411                 return PTR_ERR(*tm);
 412         }
 413
 414         if (create) {
 415                 r = dm_sm_metadata_create(*sm, *tm, dm_bm_nr_blocks(bm),
 416                                           sb_location);
 417                 if (r) {
 418                         DMERR("couldn't create metadata space map");
 419                         goto bad;
 420                 }
 421
 422         } else {
 423                 r = dm_sm_metadata_open(*sm, *tm, sm_root, sm_len);
 424                 if (r) {
 425                         DMERR("couldn't open metadata space map");
 426                         goto bad;
 427                 }
 428         }
 429
 430         return 0;
 431
 432 bad:
 433         dm_tm_destroy(*tm);
 434         dm_sm_destroy(*sm);
 435         return r;
 436 }
 437
 438 int dm_tm_create_with_sm(struct dm_block_manager *bm, dm_block_t sb_location,
 439                          struct dm_transaction_manager **tm,
 440                          struct dm_space_map **sm)
 441 {
 442         return dm_tm_create_internal(bm, sb_location, tm, sm, 1, NULL, 0);
 443 }
 444 EXPORT_SYMBOL_GPL(dm_tm_create_with_sm);
 445
 446 int dm_tm_open_with_sm(struct dm_block_manager *bm, dm_block_t sb_location,
 447                        void *sm_root, size_t root_len,
 448                        struct dm_transaction_manager **tm,
 449                        struct dm_space_map **sm)
 450 {
 451         return dm_tm_create_internal(bm, sb_location, tm, sm, 0, sm_root, root_len);
 452 }
 453 EXPORT_SYMBOL_GPL(dm_tm_open_with_sm);
 454
 455 /*----------------------------------------------------------------*/