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         while (pool->curr_nr) {
 154                 void *element = remove_element(pool);
 155                 pool->free(element, pool->pool_data);
 156         }
 157         kfree(pool->elements);
 158         kfree(pool);
 159 }
 160 EXPORT_SYMBOL(mempool_destroy);
 161
 162 /**
 163  * mempool_create - create a memory pool
 164  * @min_nr:    the minimum number of elements guaranteed to be
 165  *             allocated for this pool.
 166  * @alloc_fn:  user-defined element-allocation function.
 167  * @free_fn:   user-defined element-freeing function.
 168  * @pool_data: optional private data available to the user-defined functions.
 169  *
 170  * this function creates and allocates a guaranteed size, preallocated
 171  * memory pool. The pool can be used from the mempool_alloc() and mempool_free()
 172  * functions. This function might sleep. Both the alloc_fn() and the free_fn()
 173  * functions might sleep - as long as the mempool_alloc() function is not called
 174  * from IRQ contexts.
 175  */
 176 mempool_t *mempool_create(int min_nr, mempool_alloc_t *alloc_fn,
 177                                 mempool_free_t *free_fn, void *pool_data)
 178 {
 179         return mempool_create_node(min_nr,alloc_fn,free_fn, pool_data,
 180                                    GFP_KERNEL, NUMA_NO_NODE);
 181 }
 182 EXPORT_SYMBOL(mempool_create);
 183
 184 mempool_t *mempool_create_node(int min_nr, mempool_alloc_t *alloc_fn,
 185                                mempool_free_t *free_fn, void *pool_data,
 186                                gfp_t gfp_mask, int node_id)
 187 {
 188         mempool_t *pool;
 189         pool = kzalloc_node(sizeof(*pool), gfp_mask, node_id);
 190         if (!pool)
 191                 return NULL;
 192         pool->elements = kmalloc_node(min_nr * sizeof(void *),
 193                                       gfp_mask, node_id);
 194         if (!pool->elements) {
 195                 kfree(pool);
 196                 return NULL;
 197         }
 198         spin_lock_init(&pool->lock);
 199         pool->min_nr = min_nr;
 200         pool->pool_data = pool_data;
 201         init_waitqueue_head(&pool->wait);
 202         pool->alloc = alloc_fn;
 203         pool->free = free_fn;
 204
 205         /*
 206          * First pre-allocate the guaranteed number of buffers.
 207          */
 208         while (pool->curr_nr < pool->min_nr) {
 209                 void *element;
 210
 211                 element = pool->alloc(gfp_mask, pool->pool_data);
 212                 if (unlikely(!element)) {
 213                         mempool_destroy(pool);
 214                         return NULL;
 215                 }
 216                 add_element(pool, element);
 217         }
 218         return pool;
 219 }
 220 EXPORT_SYMBOL(mempool_create_node);
 221
 222 /**
 223  * mempool_resize - resize an existing memory pool
 224  * @pool:       pointer to the memory pool which was allocated via
 225  *              mempool_create().
 226  * @new_min_nr: the new minimum number of elements guaranteed to be
 227  *              allocated for this pool.
 228  *
 229  * This function shrinks/grows the pool. In the case of growing,
 230  * it cannot be guaranteed that the pool will be grown to the new
 231  * size immediately, but new mempool_free() calls will refill it.
 232  * This function may sleep.
 233  *
 234  * Note, the caller must guarantee that no mempool_destroy is called
 235  * while this function is running. mempool_alloc() & mempool_free()
 236  * might be called (eg. from IRQ contexts) while this function executes.
 237  */
 238 int mempool_resize(mempool_t *pool, int new_min_nr)
 239 {
 240         void *element;
 241         void **new_elements;
 242         unsigned long flags;
 243
 244         BUG_ON(new_min_nr <= 0);
 245         might_sleep();
 246
 247         spin_lock_irqsave(&pool->lock, flags);
 248         if (new_min_nr <= pool->min_nr) {
 249                 while (new_min_nr < pool->curr_nr) {
 250                         element = remove_element(pool);
 251                         spin_unlock_irqrestore(&pool->lock, flags);
 252                         pool->free(element, pool->pool_data);
 253                         spin_lock_irqsave(&pool->lock, flags);
 254                 }
 255                 pool->min_nr = new_min_nr;
 256                 goto out_unlock;
 257         }
 258         spin_unlock_irqrestore(&pool->lock, flags);
 259
 260         /* Grow the pool */
 261         new_elements = kmalloc_array(new_min_nr, sizeof(*new_elements),
 262                                      GFP_KERNEL);
 263         if (!new_elements)
 264                 return -ENOMEM;
 265
 266         spin_lock_irqsave(&pool->lock, flags);
 267         if (unlikely(new_min_nr <= pool->min_nr)) {
 268                 /* Raced, other resize will do our work */
 269                 spin_unlock_irqrestore(&pool->lock, flags);
 270                 kfree(new_elements);
 271                 goto out;
 272         }
 273         memcpy(new_elements, pool->elements,
 274                         pool->curr_nr * sizeof(*new_elements));
 275         kfree(pool->elements);
 276         pool->elements = new_elements;
 277         pool->min_nr = new_min_nr;
 278
 279         while (pool->curr_nr < pool->min_nr) {
 280                 spin_unlock_irqrestore(&pool->lock, flags);
 281                 element = pool->alloc(GFP_KERNEL, pool->pool_data);
 282                 if (!element)
 283                         goto out;
 284                 spin_lock_irqsave(&pool->lock, flags);
 285                 if (pool->curr_nr < pool->min_nr) {
 286                         add_element(pool, element);
 287                 } else {
 288                         spin_unlock_irqrestore(&pool->lock, flags);
 289                         pool->free(element, pool->pool_data);   /* Raced */
 290                         goto out;
 291                 }
 292         }
 293 out_unlock:
 294         spin_unlock_irqrestore(&pool->lock, flags);
 295 out:
 296         return 0;
 297 }
 298 EXPORT_SYMBOL(mempool_resize);
 299
 300 /**
 301  * mempool_alloc - allocate an element from a specific memory pool
 302  * @pool:      pointer to the memory pool which was allocated via
 303  *             mempool_create().
 304  * @gfp_mask:  the usual allocation bitmask.
 305  *
 306  * this function only sleeps if the alloc_fn() function sleeps or
 307  * returns NULL. Note that due to preallocation, this function
 308  * *never* fails when called from process contexts. (it might
 309  * fail if called from an IRQ context.)
 310  * Note: using __GFP_ZERO is not supported.
 311  */
 312 void * mempool_alloc(mempool_t *pool, gfp_t gfp_mask)
 313 {
 314         void *element;
 315         unsigned long flags;
 316         wait_queue_t wait;
 317         gfp_t gfp_temp;
 318
 319         VM_WARN_ON_ONCE(gfp_mask & __GFP_ZERO);
 320         might_sleep_if(gfp_mask & __GFP_WAIT);
 321
 322         gfp_mask |= __GFP_NOMEMALLOC;   /* don't allocate emergency reserves */
 323         gfp_mask |= __GFP_NORETRY;      /* don't loop in __alloc_pages */
 324         gfp_mask |= __GFP_NOWARN;       /* failures are OK */
 325
 326         gfp_temp = gfp_mask & ~(__GFP_WAIT|__GFP_IO);
 327
 328 repeat_alloc:
 329
 330         element = pool->alloc(gfp_temp, pool->pool_data);
 331         if (likely(element != NULL))
 332                 return element;
 333
 334         spin_lock_irqsave(&pool->lock, flags);
 335         if (likely(pool->curr_nr)) {
 336                 element = remove_element(pool);
 337                 spin_unlock_irqrestore(&pool->lock, flags);
 338                 /* paired with rmb in mempool_free(), read comment there */
 339                 smp_wmb();
 340                 /*
 341                  * Update the allocation stack trace as this is more useful
 342                  * for debugging.
 343                  */
 344                 kmemleak_update_trace(element);
 345                 return element;
 346         }
 347
 348         /*
 349          * We use gfp mask w/o __GFP_WAIT or IO for the first round.  If
 350          * alloc failed with that and @pool was empty, retry immediately.
 351          */
 352         if (gfp_temp != gfp_mask) {
 353                 spin_unlock_irqrestore(&pool->lock, flags);
 354                 gfp_temp = gfp_mask;
 355                 goto repeat_alloc;
 356         }
 357
 358         /* We must not sleep if !__GFP_WAIT */
 359         if (!(gfp_mask & __GFP_WAIT)) {
 360                 spin_unlock_irqrestore(&pool->lock, flags);
 361                 return NULL;
 362         }
 363
 364         /* Let's wait for someone else to return an element to @pool */
 365         init_wait(&wait);
 366         prepare_to_wait(&pool->wait, &wait, TASK_UNINTERRUPTIBLE);
 367
 368         spin_unlock_irqrestore(&pool->lock, flags);
 369
 370         /*
 371          * FIXME: this should be io_schedule().  The timeout is there as a
 372          * workaround for some DM problems in 2.6.18.
 373          */
 374         io_schedule_timeout(5*HZ);
 375
 376         finish_wait(&pool->wait, &wait);
 377         goto repeat_alloc;
 378 }
 379 EXPORT_SYMBOL(mempool_alloc);
 380
 381 /**
 382  * mempool_free - return an element to the pool.
 383  * @element:   pool element pointer.
 384  * @pool:      pointer to the memory pool which was allocated via
 385  *             mempool_create().
 386  *
 387  * this function only sleeps if the free_fn() function sleeps.
 388  */
 389 void mempool_free(void *element, mempool_t *pool)
 390 {
 391         unsigned long flags;
 392
 393         if (unlikely(element == NULL))
 394                 return;
 395
 396         /*
 397          * Paired with the wmb in mempool_alloc().  The preceding read is
 398          * for @element and the following @pool->curr_nr.  This ensures
 399          * that the visible value of @pool->curr_nr is from after the
 400          * allocation of @element.  This is necessary for fringe cases
 401          * where @element was passed to this task without going through
 402          * barriers.
 403          *
 404          * For example, assume @p is %NULL at the beginning and one task
 405          * performs "p = mempool_alloc(...);" while another task is doing
 406          * "while (!p) cpu_relax(); mempool_free(p, ...);".  This function
 407          * may end up using curr_nr value which is from before allocation
 408          * of @p without the following rmb.
 409          */
 410         smp_rmb();
 411
 412         /*
 413          * For correctness, we need a test which is guaranteed to trigger
 414          * if curr_nr + #allocated == min_nr.  Testing curr_nr < min_nr
 415          * without locking achieves that and refilling as soon as possible
 416          * is desirable.
 417          *
 418          * Because curr_nr visible here is always a value after the
 419          * allocation of @element, any task which decremented curr_nr below
 420          * min_nr is guaranteed to see curr_nr < min_nr unless curr_nr gets
 421          * incremented to min_nr afterwards.  If curr_nr gets incremented
 422          * to min_nr after the allocation of @element, the elements
 423          * allocated after that are subject to the same guarantee.
 424          *
 425          * Waiters happen iff curr_nr is 0 and the above guarantee also
 426          * ensures that there will be frees which return elements to the
 427          * pool waking up the waiters.
 428          */
 429         if (unlikely(pool->curr_nr < pool->min_nr)) {
 430                 spin_lock_irqsave(&pool->lock, flags);
 431                 if (likely(pool->curr_nr < pool->min_nr)) {
 432                         add_element(pool, element);
 433                         spin_unlock_irqrestore(&pool->lock, flags);
 434                         wake_up(&pool->wait);
 435                         return;
 436                 }
 437                 spin_unlock_irqrestore(&pool->lock, flags);
 438         }
 439         pool->free(element, pool->pool_data);
 440 }
 441 EXPORT_SYMBOL(mempool_free);
 442
 443 /*
 444  * A commonly used alloc and free fn.
 445  */
 446 void *mempool_alloc_slab(gfp_t gfp_mask, void *pool_data)
 447 {
 448         struct kmem_cache *mem = pool_data;
 449         VM_BUG_ON(mem->ctor);
 450         return kmem_cache_alloc(mem, gfp_mask);
 451 }
 452 EXPORT_SYMBOL(mempool_alloc_slab);
 453
 454 void mempool_free_slab(void *element, void *pool_data)
 455 {
 456         struct kmem_cache *mem = pool_data;
 457         kmem_cache_free(mem, element);
 458 }
 459 EXPORT_SYMBOL(mempool_free_slab);
 460
 461 /*
 462  * A commonly used alloc and free fn that kmalloc/kfrees the amount of memory
 463  * specified by pool_data
 464  */
 465 void *mempool_kmalloc(gfp_t gfp_mask, void *pool_data)
 466 {
 467         size_t size = (size_t)pool_data;
 468         return kmalloc(size, gfp_mask);
 469 }
 470 EXPORT_SYMBOL(mempool_kmalloc);
 471
 472 void mempool_kfree(void *element, void *pool_data)
 473 {
 474         kfree(element);
 475 }
 476 EXPORT_SYMBOL(mempool_kfree);
 477
 478 /*
 479  * A simple mempool-backed page allocator that allocates pages
 480  * of the order specified by pool_data.
 481  */
 482 void *mempool_alloc_pages(gfp_t gfp_mask, void *pool_data)
 483 {
 484         int order = (int)(long)pool_data;
 485         return alloc_pages(gfp_mask, order);
 486 }
 487 EXPORT_SYMBOL(mempool_alloc_pages);
 488
 489 void mempool_free_pages(void *element, void *pool_data)
 490 {
 491         int order = (int)(long)pool_data;
 492         __free_pages(element, order);
 493 }
 494 EXPORT_SYMBOL(mempool_free_pages);