drivers/md/dm-cache-policy-cleaner.c

   1 /*
   2  * Copyright (C) 2012 Red Hat. All rights reserved.
   3  *
   4  * writeback cache policy supporting flushing out dirty cache blocks.
   5  *
   6  * This file is released under the GPL.
   7  */
   8
   9 #include "dm-cache-policy.h"
  10 #include "dm.h"
  11
  12 #include <linux/hash.h>
  13 #include <linux/module.h>
  14 #include <linux/slab.h>
  15 #include <linux/vmalloc.h>
  16
  17 /*----------------------------------------------------------------*/
  18
  19 #define DM_MSG_PREFIX "cache cleaner"
  20 #define CLEANER_VERSION "1.0.0"
  21
  22 /* Cache entry struct. */
  23 struct wb_cache_entry {
  24         struct list_head list;
  25         struct hlist_node hlist;
  26
  27         dm_oblock_t oblock;
  28         dm_cblock_t cblock;
  29         bool dirty:1;
  30         bool pending:1;
  31 };
  32
  33 struct hash {
  34         struct hlist_head *table;
  35         dm_block_t hash_bits;
  36         unsigned nr_buckets;
  37 };
  38
  39 struct policy {
  40         struct dm_cache_policy policy;
  41         spinlock_t lock;
  42
  43         struct list_head free;
  44         struct list_head clean;
  45         struct list_head clean_pending;
  46         struct list_head dirty;
  47
  48         /*
  49          * We know exactly how many cblocks will be needed,
  50          * so we can allocate them up front.
  51          */
  52         dm_cblock_t cache_size, nr_cblocks_allocated;
  53         struct wb_cache_entry *cblocks;
  54         struct hash chash;
  55 };
  56
  57 /*----------------------------------------------------------------------------*/
  58
  59 /*
  60  * Low-level functions.
  61  */
  62 static unsigned next_power(unsigned n, unsigned min)
  63 {
  64         return roundup_pow_of_two(max(n, min));
  65 }
  66
  67 static struct policy *to_policy(struct dm_cache_policy *p)
  68 {
  69         return container_of(p, struct policy, policy);
  70 }
  71
  72 static struct list_head *list_pop(struct list_head *q)
  73 {
  74         struct list_head *r = q->next;
  75
  76         list_del(r);
  77
  78         return r;
  79 }
  80
  81 /*----------------------------------------------------------------------------*/
  82
  83 /* Allocate/free various resources. */
  84 static int alloc_hash(struct hash *hash, unsigned elts)
  85 {
  86         hash->nr_buckets = next_power(elts >> 4, 16);
  87         hash->hash_bits = ffs(hash->nr_buckets) - 1;
  88         hash->table = vzalloc(sizeof(*hash->table) * hash->nr_buckets);
  89
  90         return hash->table ? 0 : -ENOMEM;
  91 }
  92
  93 static void free_hash(struct hash *hash)
  94 {
  95         vfree(hash->table);
  96 }
  97
  98 static int alloc_cache_blocks_with_hash(struct policy *p, dm_cblock_t cache_size)
  99 {
 100         int r = -ENOMEM;
 101
 102         p->cblocks = vzalloc(sizeof(*p->cblocks) * from_cblock(cache_size));
 103         if (p->cblocks) {
 104                 unsigned u = from_cblock(cache_size);
 105
 106                 while (u--)
 107                         list_add(&p->cblocks[u].list, &p->free);
 108
 109                 p->nr_cblocks_allocated = 0;
 110
 111                 /* Cache entries hash. */
 112                 r = alloc_hash(&p->chash, from_cblock(cache_size));
 113                 if (r)
 114                         vfree(p->cblocks);
 115         }
 116
 117         return r;
 118 }
 119
 120 static void free_cache_blocks_and_hash(struct policy *p)
 121 {
 122         free_hash(&p->chash);
 123         vfree(p->cblocks);
 124 }
 125
 126 static struct wb_cache_entry *alloc_cache_entry(struct policy *p)
 127 {
 128         struct wb_cache_entry *e;
 129
 130         BUG_ON(from_cblock(p->nr_cblocks_allocated) >= from_cblock(p->cache_size));
 131
 132         e = list_entry(list_pop(&p->free), struct wb_cache_entry, list);
 133         p->nr_cblocks_allocated = to_cblock(from_cblock(p->nr_cblocks_allocated) + 1);
 134
 135         return e;
 136 }
 137
 138 /*----------------------------------------------------------------------------*/
 139
 140 /* Hash functions (lookup, insert, remove). */
 141 static struct wb_cache_entry *lookup_cache_entry(struct policy *p, dm_oblock_t oblock)
 142 {
 143         struct hash *hash = &p->chash;
 144         unsigned h = hash_64(from_oblock(oblock), hash->hash_bits);
 145         struct wb_cache_entry *cur;
 146         struct hlist_head *bucket = &hash->table[h];
 147
 148         hlist_for_each_entry(cur, bucket, hlist) {
 149                 if (cur->oblock == oblock) {
 150                         /* Move upfront bucket for faster access. */
 151                         hlist_del(&cur->hlist);
 152                         hlist_add_head(&cur->hlist, bucket);
 153                         return cur;
 154                 }
 155         }
 156
 157         return NULL;
 158 }
 159
 160 static void insert_cache_hash_entry(struct policy *p, struct wb_cache_entry *e)
 161 {
 162         unsigned h = hash_64(from_oblock(e->oblock), p->chash.hash_bits);
 163
 164         hlist_add_head(&e->hlist, &p->chash.table[h]);
 165 }
 166
 167 static void remove_cache_hash_entry(struct wb_cache_entry *e)
 168 {
 169         hlist_del(&e->hlist);
 170 }
 171
 172 /* Public interface (see dm-cache-policy.h */
 173 static int wb_map(struct dm_cache_policy *pe, dm_oblock_t oblock,
 174                   bool can_block, bool can_migrate, bool discarded_oblock,
 175                   struct bio *bio, struct policy_result *result)
 176 {
 177         struct policy *p = to_policy(pe);
 178         struct wb_cache_entry *e;
 179         unsigned long flags;
 180
 181         result->op = POLICY_MISS;
 182
 183         if (can_block)
 184                 spin_lock_irqsave(&p->lock, flags);
 185
 186         else if (!spin_trylock_irqsave(&p->lock, flags))
 187                 return -EWOULDBLOCK;
 188
 189         e = lookup_cache_entry(p, oblock);
 190         if (e) {
 191                 result->op = POLICY_HIT;
 192                 result->cblock = e->cblock;
 193
 194         }
 195
 196         spin_unlock_irqrestore(&p->lock, flags);
 197
 198         return 0;
 199 }
 200
 201 static int wb_lookup(struct dm_cache_policy *pe, dm_oblock_t oblock, dm_cblock_t *cblock)
 202 {
 203         int r;
 204         struct policy *p = to_policy(pe);
 205         struct wb_cache_entry *e;
 206         unsigned long flags;
 207
 208         if (!spin_trylock_irqsave(&p->lock, flags))
 209                 return -EWOULDBLOCK;
 210
 211         e = lookup_cache_entry(p, oblock);
 212         if (e) {
 213                 *cblock = e->cblock;
 214                 r = 0;
 215
 216         } else
 217                 r = -ENOENT;
 218
 219         spin_unlock_irqrestore(&p->lock, flags);
 220
 221         return r;
 222 }
 223
 224 static void __set_clear_dirty(struct dm_cache_policy *pe, dm_oblock_t oblock, bool set)
 225 {
 226         struct policy *p = to_policy(pe);
 227         struct wb_cache_entry *e;
 228
 229         e = lookup_cache_entry(p, oblock);
 230         BUG_ON(!e);
 231
 232         if (set) {
 233                 if (!e->dirty) {
 234                         e->dirty = true;
 235                         list_move(&e->list, &p->dirty);
 236                 }
 237
 238         } else {
 239                 if (e->dirty) {
 240                         e->pending = false;
 241                         e->dirty = false;
 242                         list_move(&e->list, &p->clean);
 243                 }
 244         }
 245 }
 246
 247 static void wb_set_dirty(struct dm_cache_policy *pe, dm_oblock_t oblock)
 248 {
 249         struct policy *p = to_policy(pe);
 250         unsigned long flags;
 251
 252         spin_lock_irqsave(&p->lock, flags);
 253         __set_clear_dirty(pe, oblock, true);
 254         spin_unlock_irqrestore(&p->lock, flags);
 255 }
 256
 257 static void wb_clear_dirty(struct dm_cache_policy *pe, dm_oblock_t oblock)
 258 {
 259         struct policy *p = to_policy(pe);
 260         unsigned long flags;
 261
 262         spin_lock_irqsave(&p->lock, flags);
 263         __set_clear_dirty(pe, oblock, false);
 264         spin_unlock_irqrestore(&p->lock, flags);
 265 }
 266
 267 static void add_cache_entry(struct policy *p, struct wb_cache_entry *e)
 268 {
 269         insert_cache_hash_entry(p, e);
 270         if (e->dirty)
 271                 list_add(&e->list, &p->dirty);
 272         else
 273                 list_add(&e->list, &p->clean);
 274 }
 275
 276 static int wb_load_mapping(struct dm_cache_policy *pe,
 277                            dm_oblock_t oblock, dm_cblock_t cblock,
 278                            uint32_t hint, bool hint_valid)
 279 {
 280         int r;
 281         struct policy *p = to_policy(pe);
 282         struct wb_cache_entry *e = alloc_cache_entry(p);
 283
 284         if (e) {
 285                 e->cblock = cblock;
 286                 e->oblock = oblock;
 287                 e->dirty = false; /* blocks default to clean */
 288                 add_cache_entry(p, e);
 289                 r = 0;
 290
 291         } else
 292                 r = -ENOMEM;
 293
 294         return r;
 295 }
 296
 297 static void wb_destroy(struct dm_cache_policy *pe)
 298 {
 299         struct policy *p = to_policy(pe);
 300
 301         free_cache_blocks_and_hash(p);
 302         kfree(p);
 303 }
 304
 305 static struct wb_cache_entry *__wb_force_remove_mapping(struct policy *p, dm_oblock_t oblock)
 306 {
 307         struct wb_cache_entry *r = lookup_cache_entry(p, oblock);
 308
 309         BUG_ON(!r);
 310
 311         remove_cache_hash_entry(r);
 312         list_del(&r->list);
 313
 314         return r;
 315 }
 316
 317 static void wb_remove_mapping(struct dm_cache_policy *pe, dm_oblock_t oblock)
 318 {
 319         struct policy *p = to_policy(pe);
 320         struct wb_cache_entry *e;
 321         unsigned long flags;
 322
 323         spin_lock_irqsave(&p->lock, flags);
 324         e = __wb_force_remove_mapping(p, oblock);
 325         list_add_tail(&e->list, &p->free);
 326         BUG_ON(!from_cblock(p->nr_cblocks_allocated));
 327         p->nr_cblocks_allocated = to_cblock(from_cblock(p->nr_cblocks_allocated) - 1);
 328         spin_unlock_irqrestore(&p->lock, flags);
 329 }
 330
 331 static void wb_force_mapping(struct dm_cache_policy *pe,
 332                                 dm_oblock_t current_oblock, dm_oblock_t oblock)
 333 {
 334         struct policy *p = to_policy(pe);
 335         struct wb_cache_entry *e;
 336         unsigned long flags;
 337
 338         spin_lock_irqsave(&p->lock, flags);
 339         e = __wb_force_remove_mapping(p, current_oblock);
 340         e->oblock = oblock;
 341         add_cache_entry(p, e);
 342         spin_unlock_irqrestore(&p->lock, flags);
 343 }
 344
 345 static struct wb_cache_entry *get_next_dirty_entry(struct policy *p)
 346 {
 347         struct list_head *l;
 348         struct wb_cache_entry *r;
 349
 350         if (list_empty(&p->dirty))
 351                 return NULL;
 352
 353         l = list_pop(&p->dirty);
 354         r = container_of(l, struct wb_cache_entry, list);
 355         list_add(l, &p->clean_pending);
 356
 357         return r;
 358 }
 359
 360 static int wb_writeback_work(struct dm_cache_policy *pe,
 361                              dm_oblock_t *oblock,
 362                              dm_cblock_t *cblock)
 363 {
 364         int r = -ENOENT;
 365         struct policy *p = to_policy(pe);
 366         struct wb_cache_entry *e;
 367         unsigned long flags;
 368
 369         spin_lock_irqsave(&p->lock, flags);
 370
 371         e = get_next_dirty_entry(p);
 372         if (e) {
 373                 *oblock = e->oblock;
 374                 *cblock = e->cblock;
 375                 r = 0;
 376         }
 377
 378         spin_unlock_irqrestore(&p->lock, flags);
 379
 380         return r;
 381 }
 382
 383 static dm_cblock_t wb_residency(struct dm_cache_policy *pe)
 384 {
 385         return to_policy(pe)->nr_cblocks_allocated;
 386 }
 387
 388 /* Init the policy plugin interface function pointers. */
 389 static void init_policy_functions(struct policy *p)
 390 {
 391         p->policy.destroy = wb_destroy;
 392         p->policy.map = wb_map;
 393         p->policy.lookup = wb_lookup;
 394         p->policy.set_dirty = wb_set_dirty;
 395         p->policy.clear_dirty = wb_clear_dirty;
 396         p->policy.load_mapping = wb_load_mapping;
 397         p->policy.walk_mappings = NULL;
 398         p->policy.remove_mapping = wb_remove_mapping;
 399         p->policy.writeback_work = wb_writeback_work;
 400         p->policy.force_mapping = wb_force_mapping;
 401         p->policy.residency = wb_residency;
 402         p->policy.tick = NULL;
 403 }
 404
 405 static struct dm_cache_policy *wb_create(dm_cblock_t cache_size,
 406                                          sector_t origin_size,
 407                                          sector_t cache_block_size)
 408 {
 409         int r;
 410         struct policy *p = kzalloc(sizeof(*p), GFP_KERNEL);
 411
 412         if (!p)
 413                 return NULL;
 414
 415         init_policy_functions(p);
 416         INIT_LIST_HEAD(&p->free);
 417         INIT_LIST_HEAD(&p->clean);
 418         INIT_LIST_HEAD(&p->clean_pending);
 419         INIT_LIST_HEAD(&p->dirty);
 420
 421         p->cache_size = cache_size;
 422         spin_lock_init(&p->lock);
 423
 424         /* Allocate cache entry structs and add them to free list. */
 425         r = alloc_cache_blocks_with_hash(p, cache_size);
 426         if (!r)
 427                 return &p->policy;
 428
 429         kfree(p);
 430
 431         return NULL;
 432 }
 433 /*----------------------------------------------------------------------------*/
 434
 435 static struct dm_cache_policy_type wb_policy_type = {
 436         .name = "cleaner",
 437         .hint_size = 0,
 438         .owner = THIS_MODULE,
 439         .create = wb_create
 440 };
 441
 442 static int __init wb_init(void)
 443 {
 444         int r = dm_cache_policy_register(&wb_policy_type);
 445
 446         if (r < 0)
 447                 DMERR("register failed %d", r);
 448         else
 449                 DMINFO("version " CLEANER_VERSION " loaded");
 450
 451         return r;
 452 }
 453
 454 static void __exit wb_exit(void)
 455 {
 456         dm_cache_policy_unregister(&wb_policy_type);
 457 }
 458
 459 module_init(wb_init);
 460 module_exit(wb_exit);
 461
 462 MODULE_AUTHOR("Heinz Mauelshagen <dm-devel@redhat.com>");
 463 MODULE_LICENSE("GPL");
 464 MODULE_DESCRIPTION("cleaner cache policy");