drivers/md/dm-bio-prison-v2.c

   1 /*
   2  * Copyright (C) 2012-2017 Red Hat, Inc.
   3  *
   4  * This file is released under the GPL.
   5  */
   6
   7 #include "dm.h"
   8 #include "dm-bio-prison-v2.h"
   9
  10 #include <linux/spinlock.h>
  11 #include <linux/mempool.h>
  12 #include <linux/module.h>
  13 #include <linux/slab.h>
  14 #include <linux/rwsem.h>
  15
  16 /*----------------------------------------------------------------*/
  17
  18 #define MIN_CELLS 1024
  19
  20 struct dm_bio_prison_v2 {
  21         struct workqueue_struct *wq;
  22
  23         spinlock_t lock;
  24         struct rb_root cells;
  25         mempool_t cell_pool;
  26 };
  27
  28 static struct kmem_cache *_cell_cache;
  29
  30 /*----------------------------------------------------------------*/
  31
  32 /*
  33  * @nr_cells should be the number of cells you want in use _concurrently_.
  34  * Don't confuse it with the number of distinct keys.
  35  */
  36 struct dm_bio_prison_v2 *dm_bio_prison_create_v2(struct workqueue_struct *wq)
  37 {
  38         struct dm_bio_prison_v2 *prison = kzalloc(sizeof(*prison), GFP_KERNEL);
  39         int ret;
  40
  41         if (!prison)
  42                 return NULL;
  43
  44         prison->wq = wq;
  45         spin_lock_init(&prison->lock);
  46
  47         ret = mempool_init_slab_pool(&prison->cell_pool, MIN_CELLS, _cell_cache);
  48         if (ret) {
  49                 kfree(prison);
  50                 return NULL;
  51         }
  52
  53         prison->cells = RB_ROOT;
  54
  55         return prison;
  56 }
  57 EXPORT_SYMBOL_GPL(dm_bio_prison_create_v2);
  58
  59 void dm_bio_prison_destroy_v2(struct dm_bio_prison_v2 *prison)
  60 {
  61         mempool_exit(&prison->cell_pool);
  62         kfree(prison);
  63 }
  64 EXPORT_SYMBOL_GPL(dm_bio_prison_destroy_v2);
  65
  66 struct dm_bio_prison_cell_v2 *dm_bio_prison_alloc_cell_v2(struct dm_bio_prison_v2 *prison, gfp_t gfp)
  67 {
  68         return mempool_alloc(&prison->cell_pool, gfp);
  69 }
  70 EXPORT_SYMBOL_GPL(dm_bio_prison_alloc_cell_v2);
  71
  72 void dm_bio_prison_free_cell_v2(struct dm_bio_prison_v2 *prison,
  73                                 struct dm_bio_prison_cell_v2 *cell)
  74 {
  75         mempool_free(cell, &prison->cell_pool);
  76 }
  77 EXPORT_SYMBOL_GPL(dm_bio_prison_free_cell_v2);
  78
  79 static void __setup_new_cell(struct dm_cell_key_v2 *key,
  80                              struct dm_bio_prison_cell_v2 *cell)
  81 {
  82         memset(cell, 0, sizeof(*cell));
  83         memcpy(&cell->key, key, sizeof(cell->key));
  84         bio_list_init(&cell->bios);
  85 }
  86
  87 static int cmp_keys(struct dm_cell_key_v2 *lhs,
  88                     struct dm_cell_key_v2 *rhs)
  89 {
  90         if (lhs->virtual < rhs->virtual)
  91                 return -1;
  92
  93         if (lhs->virtual > rhs->virtual)
  94                 return 1;
  95
  96         if (lhs->dev < rhs->dev)
  97                 return -1;
  98
  99         if (lhs->dev > rhs->dev)
 100                 return 1;
 101
 102         if (lhs->block_end <= rhs->block_begin)
 103                 return -1;
 104
 105         if (lhs->block_begin >= rhs->block_end)
 106                 return 1;
 107
 108         return 0;
 109 }
 110
 111 /*
 112  * Returns true if node found, otherwise it inserts a new one.
 113  */
 114 static bool __find_or_insert(struct dm_bio_prison_v2 *prison,
 115                              struct dm_cell_key_v2 *key,
 116                              struct dm_bio_prison_cell_v2 *cell_prealloc,
 117                              struct dm_bio_prison_cell_v2 **result)
 118 {
 119         int r;
 120         struct rb_node **new = &prison->cells.rb_node, *parent = NULL;
 121
 122         while (*new) {
 123                 struct dm_bio_prison_cell_v2 *cell =
 124                         rb_entry(*new, struct dm_bio_prison_cell_v2, node);
 125
 126                 r = cmp_keys(key, &cell->key);
 127
 128                 parent = *new;
 129                 if (r < 0)
 130                         new = &((*new)->rb_left);
 131
 132                 else if (r > 0)
 133                         new = &((*new)->rb_right);
 134
 135                 else {
 136                         *result = cell;
 137                         return true;
 138                 }
 139         }
 140
 141         __setup_new_cell(key, cell_prealloc);
 142         *result = cell_prealloc;
 143         rb_link_node(&cell_prealloc->node, parent, new);
 144         rb_insert_color(&cell_prealloc->node, &prison->cells);
 145
 146         return false;
 147 }
 148
 149 static bool __get(struct dm_bio_prison_v2 *prison,
 150                   struct dm_cell_key_v2 *key,
 151                   unsigned lock_level,
 152                   struct bio *inmate,
 153                   struct dm_bio_prison_cell_v2 *cell_prealloc,
 154                   struct dm_bio_prison_cell_v2 **cell)
 155 {
 156         if (__find_or_insert(prison, key, cell_prealloc, cell)) {
 157                 if ((*cell)->exclusive_lock) {
 158                         if (lock_level <= (*cell)->exclusive_level) {
 159                                 bio_list_add(&(*cell)->bios, inmate);
 160                                 return false;
 161                         }
 162                 }
 163
 164                 (*cell)->shared_count++;
 165
 166         } else
 167                 (*cell)->shared_count = 1;
 168
 169         return true;
 170 }
 171
 172 bool dm_cell_get_v2(struct dm_bio_prison_v2 *prison,
 173                     struct dm_cell_key_v2 *key,
 174                     unsigned lock_level,
 175                     struct bio *inmate,
 176                     struct dm_bio_prison_cell_v2 *cell_prealloc,
 177                     struct dm_bio_prison_cell_v2 **cell_result)
 178 {
 179         int r;
 180
 181         spin_lock_irq(&prison->lock);
 182         r = __get(prison, key, lock_level, inmate, cell_prealloc, cell_result);
 183         spin_unlock_irq(&prison->lock);
 184
 185         return r;
 186 }
 187 EXPORT_SYMBOL_GPL(dm_cell_get_v2);
 188
 189 static bool __put(struct dm_bio_prison_v2 *prison,
 190                   struct dm_bio_prison_cell_v2 *cell)
 191 {
 192         BUG_ON(!cell->shared_count);
 193         cell->shared_count--;
 194
 195         // FIXME: shared locks granted above the lock level could starve this
 196         if (!cell->shared_count) {
 197                 if (cell->exclusive_lock){
 198                         if (cell->quiesce_continuation) {
 199                                 queue_work(prison->wq, cell->quiesce_continuation);
 200                                 cell->quiesce_continuation = NULL;
 201                         }
 202                 } else {
 203                         rb_erase(&cell->node, &prison->cells);
 204                         return true;
 205                 }
 206         }
 207
 208         return false;
 209 }
 210
 211 bool dm_cell_put_v2(struct dm_bio_prison_v2 *prison,
 212                     struct dm_bio_prison_cell_v2 *cell)
 213 {
 214         bool r;
 215         unsigned long flags;
 216
 217         spin_lock_irqsave(&prison->lock, flags);
 218         r = __put(prison, cell);
 219         spin_unlock_irqrestore(&prison->lock, flags);
 220
 221         return r;
 222 }
 223 EXPORT_SYMBOL_GPL(dm_cell_put_v2);
 224
 225 static int __lock(struct dm_bio_prison_v2 *prison,
 226                   struct dm_cell_key_v2 *key,
 227                   unsigned lock_level,
 228                   struct dm_bio_prison_cell_v2 *cell_prealloc,
 229                   struct dm_bio_prison_cell_v2 **cell_result)
 230 {
 231         struct dm_bio_prison_cell_v2 *cell;
 232
 233         if (__find_or_insert(prison, key, cell_prealloc, &cell)) {
 234                 if (cell->exclusive_lock)
 235                         return -EBUSY;
 236
 237                 cell->exclusive_lock = true;
 238                 cell->exclusive_level = lock_level;
 239                 *cell_result = cell;
 240
 241                 // FIXME: we don't yet know what level these shared locks
 242                 // were taken at, so have to quiesce them all.
 243                 return cell->shared_count > 0;
 244
 245         } else {
 246                 cell = cell_prealloc;
 247                 cell->shared_count = 0;
 248                 cell->exclusive_lock = true;
 249                 cell->exclusive_level = lock_level;
 250                 *cell_result = cell;
 251         }
 252
 253         return 0;
 254 }
 255
 256 int dm_cell_lock_v2(struct dm_bio_prison_v2 *prison,
 257                     struct dm_cell_key_v2 *key,
 258                     unsigned lock_level,
 259                     struct dm_bio_prison_cell_v2 *cell_prealloc,
 260                     struct dm_bio_prison_cell_v2 **cell_result)
 261 {
 262         int r;
 263
 264         spin_lock_irq(&prison->lock);
 265         r = __lock(prison, key, lock_level, cell_prealloc, cell_result);
 266         spin_unlock_irq(&prison->lock);
 267
 268         return r;
 269 }
 270 EXPORT_SYMBOL_GPL(dm_cell_lock_v2);
 271
 272 static void __quiesce(struct dm_bio_prison_v2 *prison,
 273                       struct dm_bio_prison_cell_v2 *cell,
 274                       struct work_struct *continuation)
 275 {
 276         if (!cell->shared_count)
 277                 queue_work(prison->wq, continuation);
 278         else
 279                 cell->quiesce_continuation = continuation;
 280 }
 281
 282 void dm_cell_quiesce_v2(struct dm_bio_prison_v2 *prison,
 283                         struct dm_bio_prison_cell_v2 *cell,
 284                         struct work_struct *continuation)
 285 {
 286         spin_lock_irq(&prison->lock);
 287         __quiesce(prison, cell, continuation);
 288         spin_unlock_irq(&prison->lock);
 289 }
 290 EXPORT_SYMBOL_GPL(dm_cell_quiesce_v2);
 291
 292 static int __promote(struct dm_bio_prison_v2 *prison,
 293                      struct dm_bio_prison_cell_v2 *cell,
 294                      unsigned new_lock_level)
 295 {
 296         if (!cell->exclusive_lock)
 297                 return -EINVAL;
 298
 299         cell->exclusive_level = new_lock_level;
 300         return cell->shared_count > 0;
 301 }
 302
 303 int dm_cell_lock_promote_v2(struct dm_bio_prison_v2 *prison,
 304                             struct dm_bio_prison_cell_v2 *cell,
 305                             unsigned new_lock_level)
 306 {
 307         int r;
 308
 309         spin_lock_irq(&prison->lock);
 310         r = __promote(prison, cell, new_lock_level);
 311         spin_unlock_irq(&prison->lock);
 312
 313         return r;
 314 }
 315 EXPORT_SYMBOL_GPL(dm_cell_lock_promote_v2);
 316
 317 static bool __unlock(struct dm_bio_prison_v2 *prison,
 318                      struct dm_bio_prison_cell_v2 *cell,
 319                      struct bio_list *bios)
 320 {
 321         BUG_ON(!cell->exclusive_lock);
 322
 323         bio_list_merge(bios, &cell->bios);
 324         bio_list_init(&cell->bios);
 325
 326         if (cell->shared_count) {
 327                 cell->exclusive_lock = false;
 328                 return false;
 329         }
 330
 331         rb_erase(&cell->node, &prison->cells);
 332         return true;
 333 }
 334
 335 bool dm_cell_unlock_v2(struct dm_bio_prison_v2 *prison,
 336                        struct dm_bio_prison_cell_v2 *cell,
 337                        struct bio_list *bios)
 338 {
 339         bool r;
 340
 341         spin_lock_irq(&prison->lock);
 342         r = __unlock(prison, cell, bios);
 343         spin_unlock_irq(&prison->lock);
 344
 345         return r;
 346 }
 347 EXPORT_SYMBOL_GPL(dm_cell_unlock_v2);
 348
 349 /*----------------------------------------------------------------*/
 350
 351 int __init dm_bio_prison_init_v2(void)
 352 {
 353         _cell_cache = KMEM_CACHE(dm_bio_prison_cell_v2, 0);
 354         if (!_cell_cache)
 355                 return -ENOMEM;
 356
 357         return 0;
 358 }
 359
 360 void dm_bio_prison_exit_v2(void)
 361 {
 362         kmem_cache_destroy(_cell_cache);
 363         _cell_cache = NULL;
 364 }