drivers/md/dm-bio-prison.c

   1 /*
   2  * Copyright (C) 2012 Red Hat, Inc.
   3  *
   4  * This file is released under the GPL.
   5  */
   6
   7 #include "dm.h"
   8 #include "dm-bio-prison.h"
   9
  10 #include <linux/spinlock.h>
  11 #include <linux/mempool.h>
  12 #include <linux/module.h>
  13 #include <linux/slab.h>
  14
  15 /*----------------------------------------------------------------*/
  16
  17 #define MIN_CELLS 1024
  18
  19 struct dm_bio_prison {
  20         spinlock_t lock;
  21         mempool_t *cell_pool;
  22         struct rb_root cells;
  23 };
  24
  25 static struct kmem_cache *_cell_cache;
  26
  27 /*----------------------------------------------------------------*/
  28
  29 /*
  30  * @nr_cells should be the number of cells you want in use _concurrently_.
  31  * Don't confuse it with the number of distinct keys.
  32  */
  33 struct dm_bio_prison *dm_bio_prison_create(void)
  34 {
  35         struct dm_bio_prison *prison = kmalloc(sizeof(*prison), GFP_KERNEL);
  36
  37         if (!prison)
  38                 return NULL;
  39
  40         spin_lock_init(&prison->lock);
  41
  42         prison->cell_pool = mempool_create_slab_pool(MIN_CELLS, _cell_cache);
  43         if (!prison->cell_pool) {
  44                 kfree(prison);
  45                 return NULL;
  46         }
  47
  48         prison->cells = RB_ROOT;
  49
  50         return prison;
  51 }
  52 EXPORT_SYMBOL_GPL(dm_bio_prison_create);
  53
  54 void dm_bio_prison_destroy(struct dm_bio_prison *prison)
  55 {
  56         mempool_destroy(prison->cell_pool);
  57         kfree(prison);
  58 }
  59 EXPORT_SYMBOL_GPL(dm_bio_prison_destroy);
  60
  61 struct dm_bio_prison_cell *dm_bio_prison_alloc_cell(struct dm_bio_prison *prison, gfp_t gfp)
  62 {
  63         return mempool_alloc(prison->cell_pool, gfp);
  64 }
  65 EXPORT_SYMBOL_GPL(dm_bio_prison_alloc_cell);
  66
  67 void dm_bio_prison_free_cell(struct dm_bio_prison *prison,
  68                              struct dm_bio_prison_cell *cell)
  69 {
  70         mempool_free(cell, prison->cell_pool);
  71 }
  72 EXPORT_SYMBOL_GPL(dm_bio_prison_free_cell);
  73
  74 static void __setup_new_cell(struct dm_cell_key *key,
  75                              struct bio *holder,
  76                              struct dm_bio_prison_cell *cell)
  77 {
  78        memcpy(&cell->key, key, sizeof(cell->key));
  79        cell->holder = holder;
  80        bio_list_init(&cell->bios);
  81 }
  82
  83 static int cmp_keys(struct dm_cell_key *lhs,
  84                     struct dm_cell_key *rhs)
  85 {
  86         if (lhs->virtual < rhs->virtual)
  87                 return -1;
  88
  89         if (lhs->virtual > rhs->virtual)
  90                 return 1;
  91
  92         if (lhs->dev < rhs->dev)
  93                 return -1;
  94
  95         if (lhs->dev > rhs->dev)
  96                 return 1;
  97
  98         if (lhs->block < rhs->block)
  99                 return -1;
 100
 101         if (lhs->block > rhs->block)
 102                 return 1;
 103
 104         return 0;
 105 }
 106
 107 static int __bio_detain(struct dm_bio_prison *prison,
 108                         struct dm_cell_key *key,
 109                         struct bio *inmate,
 110                         struct dm_bio_prison_cell *cell_prealloc,
 111                         struct dm_bio_prison_cell **cell_result)
 112 {
 113         int r;
 114         struct rb_node **new = &prison->cells.rb_node, *parent = NULL;
 115
 116         while (*new) {
 117                 struct dm_bio_prison_cell *cell =
 118                         container_of(*new, struct dm_bio_prison_cell, node);
 119
 120                 r = cmp_keys(key, &cell->key);
 121
 122                 parent = *new;
 123                 if (r < 0)
 124                         new = &((*new)->rb_left);
 125                 else if (r > 0)
 126                         new = &((*new)->rb_right);
 127                 else {
 128                         if (inmate)
 129                                 bio_list_add(&cell->bios, inmate);
 130                         *cell_result = cell;
 131                         return 1;
 132                 }
 133         }
 134
 135         __setup_new_cell(key, inmate, cell_prealloc);
 136         *cell_result = cell_prealloc;
 137
 138         rb_link_node(&cell_prealloc->node, parent, new);
 139         rb_insert_color(&cell_prealloc->node, &prison->cells);
 140
 141         return 0;
 142 }
 143
 144 static int bio_detain(struct dm_bio_prison *prison,
 145                       struct dm_cell_key *key,
 146                       struct bio *inmate,
 147                       struct dm_bio_prison_cell *cell_prealloc,
 148                       struct dm_bio_prison_cell **cell_result)
 149 {
 150         int r;
 151         unsigned long flags;
 152
 153         spin_lock_irqsave(&prison->lock, flags);
 154         r = __bio_detain(prison, key, inmate, cell_prealloc, cell_result);
 155         spin_unlock_irqrestore(&prison->lock, flags);
 156
 157         return r;
 158 }
 159
 160 int dm_bio_detain(struct dm_bio_prison *prison,
 161                   struct dm_cell_key *key,
 162                   struct bio *inmate,
 163                   struct dm_bio_prison_cell *cell_prealloc,
 164                   struct dm_bio_prison_cell **cell_result)
 165 {
 166         return bio_detain(prison, key, inmate, cell_prealloc, cell_result);
 167 }
 168 EXPORT_SYMBOL_GPL(dm_bio_detain);
 169
 170 int dm_get_cell(struct dm_bio_prison *prison,
 171                 struct dm_cell_key *key,
 172                 struct dm_bio_prison_cell *cell_prealloc,
 173                 struct dm_bio_prison_cell **cell_result)
 174 {
 175         return bio_detain(prison, key, NULL, cell_prealloc, cell_result);
 176 }
 177 EXPORT_SYMBOL_GPL(dm_get_cell);
 178
 179 /*
 180  * @inmates must have been initialised prior to this call
 181  */
 182 static void __cell_release(struct dm_bio_prison *prison,
 183                            struct dm_bio_prison_cell *cell,
 184                            struct bio_list *inmates)
 185 {
 186         rb_erase(&cell->node, &prison->cells);
 187
 188         if (inmates) {
 189                 if (cell->holder)
 190                         bio_list_add(inmates, cell->holder);
 191                 bio_list_merge(inmates, &cell->bios);
 192         }
 193 }
 194
 195 void dm_cell_release(struct dm_bio_prison *prison,
 196                      struct dm_bio_prison_cell *cell,
 197                      struct bio_list *bios)
 198 {
 199         unsigned long flags;
 200
 201         spin_lock_irqsave(&prison->lock, flags);
 202         __cell_release(prison, cell, bios);
 203         spin_unlock_irqrestore(&prison->lock, flags);
 204 }
 205 EXPORT_SYMBOL_GPL(dm_cell_release);
 206
 207 /*
 208  * Sometimes we don't want the holder, just the additional bios.
 209  */
 210 static void __cell_release_no_holder(struct dm_bio_prison *prison,
 211                                      struct dm_bio_prison_cell *cell,
 212                                      struct bio_list *inmates)
 213 {
 214         rb_erase(&cell->node, &prison->cells);
 215         bio_list_merge(inmates, &cell->bios);
 216 }
 217
 218 void dm_cell_release_no_holder(struct dm_bio_prison *prison,
 219                                struct dm_bio_prison_cell *cell,
 220                                struct bio_list *inmates)
 221 {
 222         unsigned long flags;
 223
 224         spin_lock_irqsave(&prison->lock, flags);
 225         __cell_release_no_holder(prison, cell, inmates);
 226         spin_unlock_irqrestore(&prison->lock, flags);
 227 }
 228 EXPORT_SYMBOL_GPL(dm_cell_release_no_holder);
 229
 230 void dm_cell_error(struct dm_bio_prison *prison,
 231                    struct dm_bio_prison_cell *cell, int error)
 232 {
 233         struct bio_list bios;
 234         struct bio *bio;
 235
 236         bio_list_init(&bios);
 237         dm_cell_release(prison, cell, &bios);
 238
 239         while ((bio = bio_list_pop(&bios)))
 240                 bio_endio(bio, error);
 241 }
 242 EXPORT_SYMBOL_GPL(dm_cell_error);
 243
 244 /*----------------------------------------------------------------*/
 245
 246 #define DEFERRED_SET_SIZE 64
 247
 248 struct dm_deferred_entry {
 249         struct dm_deferred_set *ds;
 250         unsigned count;
 251         struct list_head work_items;
 252 };
 253
 254 struct dm_deferred_set {
 255         spinlock_t lock;
 256         unsigned current_entry;
 257         unsigned sweeper;
 258         struct dm_deferred_entry entries[DEFERRED_SET_SIZE];
 259 };
 260
 261 struct dm_deferred_set *dm_deferred_set_create(void)
 262 {
 263         int i;
 264         struct dm_deferred_set *ds;
 265
 266         ds = kmalloc(sizeof(*ds), GFP_KERNEL);
 267         if (!ds)
 268                 return NULL;
 269
 270         spin_lock_init(&ds->lock);
 271         ds->current_entry = 0;
 272         ds->sweeper = 0;
 273         for (i = 0; i < DEFERRED_SET_SIZE; i++) {
 274                 ds->entries[i].ds = ds;
 275                 ds->entries[i].count = 0;
 276                 INIT_LIST_HEAD(&ds->entries[i].work_items);
 277         }
 278
 279         return ds;
 280 }
 281 EXPORT_SYMBOL_GPL(dm_deferred_set_create);
 282
 283 void dm_deferred_set_destroy(struct dm_deferred_set *ds)
 284 {
 285         kfree(ds);
 286 }
 287 EXPORT_SYMBOL_GPL(dm_deferred_set_destroy);
 288
 289 struct dm_deferred_entry *dm_deferred_entry_inc(struct dm_deferred_set *ds)
 290 {
 291         unsigned long flags;
 292         struct dm_deferred_entry *entry;
 293
 294         spin_lock_irqsave(&ds->lock, flags);
 295         entry = ds->entries + ds->current_entry;
 296         entry->count++;
 297         spin_unlock_irqrestore(&ds->lock, flags);
 298
 299         return entry;
 300 }
 301 EXPORT_SYMBOL_GPL(dm_deferred_entry_inc);
 302
 303 static unsigned ds_next(unsigned index)
 304 {
 305         return (index + 1) % DEFERRED_SET_SIZE;
 306 }
 307
 308 static void __sweep(struct dm_deferred_set *ds, struct list_head *head)
 309 {
 310         while ((ds->sweeper != ds->current_entry) &&
 311                !ds->entries[ds->sweeper].count) {
 312                 list_splice_init(&ds->entries[ds->sweeper].work_items, head);
 313                 ds->sweeper = ds_next(ds->sweeper);
 314         }
 315
 316         if ((ds->sweeper == ds->current_entry) && !ds->entries[ds->sweeper].count)
 317                 list_splice_init(&ds->entries[ds->sweeper].work_items, head);
 318 }
 319
 320 void dm_deferred_entry_dec(struct dm_deferred_entry *entry, struct list_head *head)
 321 {
 322         unsigned long flags;
 323
 324         spin_lock_irqsave(&entry->ds->lock, flags);
 325         BUG_ON(!entry->count);
 326         --entry->count;
 327         __sweep(entry->ds, head);
 328         spin_unlock_irqrestore(&entry->ds->lock, flags);
 329 }
 330 EXPORT_SYMBOL_GPL(dm_deferred_entry_dec);
 331
 332 /*
 333  * Returns 1 if deferred or 0 if no pending items to delay job.
 334  */
 335 int dm_deferred_set_add_work(struct dm_deferred_set *ds, struct list_head *work)
 336 {
 337         int r = 1;
 338         unsigned long flags;
 339         unsigned next_entry;
 340
 341         spin_lock_irqsave(&ds->lock, flags);
 342         if ((ds->sweeper == ds->current_entry) &&
 343             !ds->entries[ds->current_entry].count)
 344                 r = 0;
 345         else {
 346                 list_add(work, &ds->entries[ds->current_entry].work_items);
 347                 next_entry = ds_next(ds->current_entry);
 348                 if (!ds->entries[next_entry].count)
 349                         ds->current_entry = next_entry;
 350         }
 351         spin_unlock_irqrestore(&ds->lock, flags);
 352
 353         return r;
 354 }
 355 EXPORT_SYMBOL_GPL(dm_deferred_set_add_work);
 356
 357 /*----------------------------------------------------------------*/
 358
 359 static int __init dm_bio_prison_init(void)
 360 {
 361         _cell_cache = KMEM_CACHE(dm_bio_prison_cell, 0);
 362         if (!_cell_cache)
 363                 return -ENOMEM;
 364
 365         return 0;
 366 }
 367
 368 static void __exit dm_bio_prison_exit(void)
 369 {
 370         kmem_cache_destroy(_cell_cache);
 371         _cell_cache = NULL;
 372 }
 373
 374 /*
 375  * module hooks
 376  */
 377 module_init(dm_bio_prison_init);
 378 module_exit(dm_bio_prison_exit);
 379
 380 MODULE_DESCRIPTION(DM_NAME " bio prison");
 381 MODULE_AUTHOR("Joe Thornber <dm-devel@redhat.com>");
 382 MODULE_LICENSE("GPL");