mm/mempool.c

   1 /*
   2  *  linux/mm/mempool.c
   3  *
   4  *  memory buffer pool support. Such pools are mostly used
   5  *  for guaranteed, deadlock-free memory allocations during
   6  *  extreme VM load.
   7  *
   8  *  started by Ingo Molnar, Copyright (C) 2001
   9  *  debugging by David Rientjes, Copyright (C) 2015
  10  */
  11
  12 #include <linux/mm.h>
  13 #include <linux/slab.h>
  14 #include <linux/highmem.h>
  15 #include <linux/kasan.h>
  16 #include <linux/kmemleak.h>
  17 #include <linux/export.h>
  18 #include <linux/mempool.h>
  19 #include <linux/blkdev.h>
  20 #include <linux/writeback.h>
  21 #include "slab.h"
  22
  23 #if defined(CONFIG_DEBUG_SLAB) || defined(CONFIG_SLUB_DEBUG_ON)
  24 static void poison_error(mempool_t *pool, void *element, size_t size,
  25                          size_t byte)
  26 {
  27         const int nr = pool->curr_nr;
  28         const int start = max_t(int, byte - (BITS_PER_LONG / 8), 0);
  29         const int end = min_t(int, byte + (BITS_PER_LONG / 8), size);
  30         int i;
  31
  32         pr_err("BUG: mempool element poison mismatch\n");
  33         pr_err("Mempool %p size %zu\n", pool, size);
  34         pr_err(" nr=%d @ %p: %s0x", nr, element, start > 0 ? "... " : "");
  35         for (i = start; i < end; i++)
  36                 pr_cont("%x ", *(u8 *)(element + i));
  37         pr_cont("%s\n", end < size ? "..." : "");
  38         dump_stack();
  39 }
  40
  41 static void __check_element(mempool_t *pool, void *element, size_t size)
  42 {
  43         u8 *obj = element;
  44         size_t i;
  45
  46         for (i = 0; i < size; i++) {
  47                 u8 exp = (i < size - 1) ? POISON_FREE : POISON_END;
  48
  49                 if (obj[i] != exp) {
  50                         poison_error(pool, element, size, i);
  51                         return;
  52                 }
  53         }
  54         memset(obj, POISON_INUSE, size);
  55 }
  56
  57 static void check_element(mempool_t *pool, void *element)
  58 {
  59         /* Mempools backed by slab allocator */
  60         if (pool->free == mempool_free_slab || pool->free == mempool_kfree)
  61                 __check_element(pool, element, ksize(element));
  62
  63         /* Mempools backed by page allocator */
  64         if (pool->free == mempool_free_pages) {
  65                 int order = (int)(long)pool->pool_data;
  66                 void *addr = kmap_atomic((struct page *)element);
  67
  68                 __check_element(pool, addr, 1UL << (PAGE_SHIFT + order));
  69                 kunmap_atomic(addr);
  70         }
  71 }
  72
  73 static void __poison_element(void *element, size_t size)
  74 {
  75         u8 *obj = element;
  76
  77         memset(obj, POISON_FREE, size - 1);
  78         obj[size - 1] = POISON_END;
  79 }
  80
  81 static void poison_element(mempool_t *pool, void *element)
  82 {
  83         /* Mempools backed by slab allocator */
  84         if (pool->alloc == mempool_alloc_slab || pool->alloc == mempool_kmalloc)
  85                 __poison_element(element, ksize(element));
  86
  87         /* Mempools backed by page allocator */
  88         if (pool->alloc == mempool_alloc_pages) {
  89                 int order = (int)(long)pool->pool_data;
  90                 void *addr = kmap_atomic((struct page *)element);
  91
  92                 __poison_element(addr, 1UL << (PAGE_SHIFT + order));
  93                 kunmap_atomic(addr);
  94         }
  95 }
  96 #else /* CONFIG_DEBUG_SLAB || CONFIG_SLUB_DEBUG_ON */
  97 static inline void check_element(mempool_t *pool, void *element)
  98 {
  99 }
 100 static inline void poison_element(mempool_t *pool, void *element)
 101 {
 102 }
 103 #endif /* CONFIG_DEBUG_SLAB || CONFIG_SLUB_DEBUG_ON */
 104
 105 static void kasan_poison_element(mempool_t *pool, void *element)
 106 {
 107         if (pool->alloc == mempool_alloc_slab)
 108                 kasan_slab_free(pool->pool_data, element);
 109         if (pool->alloc == mempool_kmalloc)
 110                 kasan_kfree(element);
 111         if (pool->alloc == mempool_alloc_pages)
 112                 kasan_free_pages(element, (unsigned long)pool->pool_data);
 113 }
 114
 115 static void kasan_unpoison_element(mempool_t *pool, void *element)
 116 {
 117         if (pool->alloc == mempool_alloc_slab)
 118                 kasan_slab_alloc(pool->pool_data, element);
 119         if (pool->alloc == mempool_kmalloc)
 120                 kasan_krealloc(element, (size_t)pool->pool_data);
 121         if (pool->alloc == mempool_alloc_pages)
 122                 kasan_alloc_pages(element, (unsigned long)pool->pool_data);
 123 }
 124
 125 static void add_element(mempool_t *pool, void *element)
 126 {
 127         BUG_ON(pool->curr_nr >= pool->min_nr);
 128         poison_element(pool, element);
 129         kasan_poison_element(pool, element);
 130         pool->elements[pool->curr_nr++] = element;
 131 }
 132
 133 static void *remove_element(mempool_t *pool)
 134 {
 135         void *element = pool->elements[--pool->curr_nr];
 136
 137         BUG_ON(pool->curr_nr < 0);
 138         check_element(pool, element);
 139         kasan_unpoison_element(pool, element);
 140         return element;
 141 }
 142
 143 /**
 144  * mempool_destroy - deallocate a memory pool
 145  * @pool:      pointer to the memory pool which was allocated via
 146  *             mempool_create().
 147  *
 148  * Free all reserved elements in @pool and @pool itself.  This function
 149  * only sleeps if the free_fn() function sleeps.
 150  */
 151 void mempool_destroy(mempool_t *pool)
 152 {
 153         if (unlikely(!pool))
 154                 return;
 155
 156         while (pool->curr_nr) {
 157                 void *element = remove_element(pool);
 158                 pool->free(element, pool->pool_data);
 159         }
 160         kfree(pool->elements);
 161         kfree(pool);
 162 }
 163 EXPORT_SYMBOL(mempool_destroy);
 164
 165 /**
 166  * mempool_create - create a memory pool
 167  * @min_nr:    the minimum number of elements guaranteed to be
 168  *             allocated for this pool.
 169  * @alloc_fn:  user-defined element-allocation function.
 170  * @free_fn:   user-defined element-freeing function.
 171  * @pool_data: optional private data available to the user-defined functions.
 172  *
 173  * this function creates and allocates a guaranteed size, preallocated
 174  * memory pool. The pool can be used from the mempool_alloc() and mempool_free()
 175  * functions. This function might sleep. Both the alloc_fn() and the free_fn()
 176  * functions might sleep - as long as the mempool_alloc() function is not called
 177  * from IRQ contexts.
 178  */
 179 mempool_t *mempool_create(int min_nr, mempool_alloc_t *alloc_fn,
 180                                 mempool_free_t *free_fn, void *pool_data)
 181 {
 182         return mempool_create_node(min_nr,alloc_fn,free_fn, pool_data,
 183                                    GFP_KERNEL, NUMA_NO_NODE);
 184 }
 185 EXPORT_SYMBOL(mempool_create);
 186
 187 mempool_t *mempool_create_node(int min_nr, mempool_alloc_t *alloc_fn,
 188                                mempool_free_t *free_fn, void *pool_data,
 189                                gfp_t gfp_mask, int node_id)
 190 {
 191         mempool_t *pool;
 192         pool = kzalloc_node(sizeof(*pool), gfp_mask, node_id);
 193         if (!pool)
 194                 return NULL;
 195         pool->elements = kmalloc_node(min_nr * sizeof(void *),
 196                                       gfp_mask, node_id);
 197         if (!pool->elements) {
 198                 kfree(pool);
 199                 return NULL;
 200         }
 201         spin_lock_init(&pool->lock);
 202         pool->min_nr = min_nr;
 203         pool->pool_data = pool_data;
 204         init_waitqueue_head(&pool->wait);
 205         pool->alloc = alloc_fn;
 206         pool->free = free_fn;
 207
 208         /*
 209          * First pre-allocate the guaranteed number of buffers.
 210          */
 211         while (pool->curr_nr < pool->min_nr) {
 212                 void *element;
 213
 214                 element = pool->alloc(gfp_mask, pool->pool_data);
 215                 if (unlikely(!element)) {
 216                         mempool_destroy(pool);
 217                         return NULL;
 218                 }
 219                 add_element(pool, element);
 220         }
 221         return pool;
 222 }
 223 EXPORT_SYMBOL(mempool_create_node);
 224
 225 /**
 226  * mempool_resize - resize an existing memory pool
 227  * @pool:       pointer to the memory pool which was allocated via
 228  *              mempool_create().
 229  * @new_min_nr: the new minimum number of elements guaranteed to be
 230  *              allocated for this pool.
 231  *
 232  * This function shrinks/grows the pool. In the case of growing,
 233  * it cannot be guaranteed that the pool will be grown to the new
 234  * size immediately, but new mempool_free() calls will refill it.
 235  * This function may sleep.
 236  *
 237  * Note, the caller must guarantee that no mempool_destroy is called
 238  * while this function is running. mempool_alloc() & mempool_free()
 239  * might be called (eg. from IRQ contexts) while this function executes.
 240  */
 241 int mempool_resize(mempool_t *pool, int new_min_nr)
 242 {
 243         void *element;
 244         void **new_elements;
 245         unsigned long flags;
 246
 247         BUG_ON(new_min_nr <= 0);
 248         might_sleep();
 249
 250         spin_lock_irqsave(&pool->lock, flags);
 251         if (new_min_nr <= pool->min_nr) {
 252                 while (new_min_nr < pool->curr_nr) {
 253                         element = remove_element(pool);
 254                         spin_unlock_irqrestore(&pool->lock, flags);
 255                         pool->free(element, pool->pool_data);
 256                         spin_lock_irqsave(&pool->lock, flags);
 257                 }
 258                 pool->min_nr = new_min_nr;
 259                 goto out_unlock;
 260         }
 261         spin_unlock_irqrestore(&pool->lock, flags);
 262
 263         /* Grow the pool */
 264         new_elements = kmalloc_array(new_min_nr, sizeof(*new_elements),
 265                                      GFP_KERNEL);
 266         if (!new_elements)
 267                 return -ENOMEM;
 268
 269         spin_lock_irqsave(&pool->lock, flags);
 270         if (unlikely(new_min_nr <= pool->min_nr)) {
 271                 /* Raced, other resize will do our work */
 272                 spin_unlock_irqrestore(&pool->lock, flags);
 273                 kfree(new_elements);
 274                 goto out;
 275         }
 276         memcpy(new_elements, pool->elements,
 277                         pool->curr_nr * sizeof(*new_elements));
 278         kfree(pool->elements);
 279         pool->elements = new_elements;
 280         pool->min_nr = new_min_nr;
 281
 282         while (pool->curr_nr < pool->min_nr) {
 283                 spin_unlock_irqrestore(&pool->lock, flags);
 284                 element = pool->alloc(GFP_KERNEL, pool->pool_data);
 285                 if (!element)
 286                         goto out;
 287                 spin_lock_irqsave(&pool->lock, flags);
 288                 if (pool->curr_nr < pool->min_nr) {
 289                         add_element(pool, element);
 290                 } else {
 291                         spin_unlock_irqrestore(&pool->lock, flags);
 292                         pool->free(element, pool->pool_data);   /* Raced */
 293                         goto out;
 294                 }
 295         }
 296 out_unlock:
 297         spin_unlock_irqrestore(&pool->lock, flags);
 298 out:
 299         return 0;
 300 }
 301 EXPORT_SYMBOL(mempool_resize);
 302
 303 /**
 304  * mempool_alloc - allocate an element from a specific memory pool
 305  * @pool:      pointer to the memory pool which was allocated via
 306  *             mempool_create().
 307  * @gfp_mask:  the usual allocation bitmask.
 308  *
 309  * this function only sleeps if the alloc_fn() function sleeps or
 310  * returns NULL. Note that due to preallocation, this function
 311  * *never* fails when called from process contexts. (it might
 312  * fail if called from an IRQ context.)
 313  * Note: using __GFP_ZERO is not supported.
 314  */
 315 void * mempool_alloc(mempool_t *pool, gfp_t gfp_mask)
 316 {
 317         void *element;
 318         unsigned long flags;
 319         wait_queue_t wait;
 320         gfp_t gfp_temp;
 321
 322         VM_WARN_ON_ONCE(gfp_mask & __GFP_ZERO);
 323         might_sleep_if(gfp_mask & __GFP_WAIT);
 324
 325         gfp_mask |= __GFP_NOMEMALLOC;   /* don't allocate emergency reserves */
 326         gfp_mask |= __GFP_NORETRY;      /* don't loop in __alloc_pages */
 327         gfp_mask |= __GFP_NOWARN;       /* failures are OK */
 328
 329         gfp_temp = gfp_mask & ~(__GFP_WAIT|__GFP_IO);
 330
 331 repeat_alloc:
 332
 333         element = pool->alloc(gfp_temp, pool->pool_data);
 334         if (likely(element != NULL))
 335                 return element;
 336
 337         spin_lock_irqsave(&pool->lock, flags);
 338         if (likely(pool->curr_nr)) {
 339                 element = remove_element(pool);
 340                 spin_unlock_irqrestore(&pool->lock, flags);
 341                 /* paired with rmb in mempool_free(), read comment there */
 342                 smp_wmb();
 343                 /*
 344                  * Update the allocation stack trace as this is more useful
 345                  * for debugging.
 346                  */
 347                 kmemleak_update_trace(element);
 348                 return element;
 349         }
 350
 351         /*
 352          * We use gfp mask w/o __GFP_WAIT or IO for the first round.  If
 353          * alloc failed with that and @pool was empty, retry immediately.
 354          */
 355         if (gfp_temp != gfp_mask) {
 356                 spin_unlock_irqrestore(&pool->lock, flags);
 357                 gfp_temp = gfp_mask;
 358                 goto repeat_alloc;
 359         }
 360
 361         /* We must not sleep if !__GFP_WAIT */
 362         if (!(gfp_mask & __GFP_WAIT)) {
 363                 spin_unlock_irqrestore(&pool->lock, flags);
 364                 return NULL;
 365         }
 366
 367         /* Let's wait for someone else to return an element to @pool */
 368         init_wait(&wait);
 369         prepare_to_wait(&pool->wait, &wait, TASK_UNINTERRUPTIBLE);
 370
 371         spin_unlock_irqrestore(&pool->lock, flags);
 372
 373         /*
 374          * FIXME: this should be io_schedule().  The timeout is there as a
 375          * workaround for some DM problems in 2.6.18.
 376          */
 377         io_schedule_timeout(5*HZ);
 378
 379         finish_wait(&pool->wait, &wait);
 380         goto repeat_alloc;
 381 }
 382 EXPORT_SYMBOL(mempool_alloc);
 383
 384 /**
 385  * mempool_free - return an element to the pool.
 386  * @element:   pool element pointer.
 387  * @pool:      pointer to the memory pool which was allocated via
 388  *             mempool_create().
 389  *
 390  * this function only sleeps if the free_fn() function sleeps.
 391  */
 392 void mempool_free(void *element, mempool_t *pool)
 393 {
 394         unsigned long flags;
 395
 396         if (unlikely(element == NULL))
 397                 return;
 398
 399         /*
 400          * Paired with the wmb in mempool_alloc().  The preceding read is
 401          * for @element and the following @pool->curr_nr.  This ensures
 402          * that the visible value of @pool->curr_nr is from after the
 403          * allocation of @element.  This is necessary for fringe cases
 404          * where @element was passed to this task without going through
 405          * barriers.
 406          *
 407          * For example, assume @p is %NULL at the beginning and one task
 408          * performs "p = mempool_alloc(...);" while another task is doing
 409          * "while (!p) cpu_relax(); mempool_free(p, ...);".  This function
 410          * may end up using curr_nr value which is from before allocation
 411          * of @p without the following rmb.
 412          */
 413         smp_rmb();
 414
 415         /*
 416          * For correctness, we need a test which is guaranteed to trigger
 417          * if curr_nr + #allocated == min_nr.  Testing curr_nr < min_nr
 418          * without locking achieves that and refilling as soon as possible
 419          * is desirable.
 420          *
 421          * Because curr_nr visible here is always a value after the
 422          * allocation of @element, any task which decremented curr_nr below
 423          * min_nr is guaranteed to see curr_nr < min_nr unless curr_nr gets
 424          * incremented to min_nr afterwards.  If curr_nr gets incremented
 425          * to min_nr after the allocation of @element, the elements
 426          * allocated after that are subject to the same guarantee.
 427          *
 428          * Waiters happen iff curr_nr is 0 and the above guarantee also
 429          * ensures that there will be frees which return elements to the
 430          * pool waking up the waiters.
 431          */
 432         if (unlikely(pool->curr_nr < pool->min_nr)) {
 433                 spin_lock_irqsave(&pool->lock, flags);
 434                 if (likely(pool->curr_nr < pool->min_nr)) {
 435                         add_element(pool, element);
 436                         spin_unlock_irqrestore(&pool->lock, flags);
 437                         wake_up(&pool->wait);
 438                         return;
 439                 }
 440                 spin_unlock_irqrestore(&pool->lock, flags);
 441         }
 442         pool->free(element, pool->pool_data);
 443 }
 444 EXPORT_SYMBOL(mempool_free);
 445
 446 /*
 447  * A commonly used alloc and free fn.
 448  */
 449 void *mempool_alloc_slab(gfp_t gfp_mask, void *pool_data)
 450 {
 451         struct kmem_cache *mem = pool_data;
 452         VM_BUG_ON(mem->ctor);
 453         return kmem_cache_alloc(mem, gfp_mask);
 454 }
 455 EXPORT_SYMBOL(mempool_alloc_slab);
 456
 457 void mempool_free_slab(void *element, void *pool_data)
 458 {
 459         struct kmem_cache *mem = pool_data;
 460         kmem_cache_free(mem, element);
 461 }
 462 EXPORT_SYMBOL(mempool_free_slab);
 463
 464 /*
 465  * A commonly used alloc and free fn that kmalloc/kfrees the amount of memory
 466  * specified by pool_data
 467  */
 468 void *mempool_kmalloc(gfp_t gfp_mask, void *pool_data)
 469 {
 470         size_t size = (size_t)pool_data;
 471         return kmalloc(size, gfp_mask);
 472 }
 473 EXPORT_SYMBOL(mempool_kmalloc);
 474
 475 void mempool_kfree(void *element, void *pool_data)
 476 {
 477         kfree(element);
 478 }
 479 EXPORT_SYMBOL(mempool_kfree);
 480
 481 /*
 482  * A simple mempool-backed page allocator that allocates pages
 483  * of the order specified by pool_data.
 484  */
 485 void *mempool_alloc_pages(gfp_t gfp_mask, void *pool_data)
 486 {
 487         int order = (int)(long)pool_data;
 488         return alloc_pages(gfp_mask, order);
 489 }
 490 EXPORT_SYMBOL(mempool_alloc_pages);
 491
 492 void mempool_free_pages(void *element, void *pool_data)
 493 {
 494         int order = (int)(long)pool_data;
 495         __free_pages(element, order);
 496 }
 497 EXPORT_SYMBOL(mempool_free_pages);