1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * linux/mm/mempool.c
4 *
5 * memory buffer pool support. Such pools are mostly used
6 * for guaranteed, deadlock-free memory allocations during
7 * extreme VM load.
8 *
9 * started by Ingo Molnar, Copyright (C) 2001
10 * debugging by David Rientjes, Copyright (C) 2015
11 */
12
13 #include <linux/mm.h>
14 #include <linux/slab.h>
15 #include <linux/highmem.h>
16 #include <linux/kasan.h>
17 #include <linux/kmemleak.h>
18 #include <linux/export.h>
19 #include <linux/mempool.h>
20 #include <linux/writeback.h>
21 #include "slab.h"
22
23 #ifdef 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 /* Skip checking: KASAN might save its metadata in the element. */
60 if (kasan_enabled())
61 return;
62
63 /* Mempools backed by slab allocator */
64 if (pool->free == mempool_kfree) {
65 __check_element(pool, element, (size_t)pool->pool_data);
66 } else if (pool->free == mempool_free_slab) {
67 __check_element(pool, element, kmem_cache_size(pool->pool_data));
68 } else if (pool->free == mempool_free_pages) {
69 /* Mempools backed by page allocator */
70 int order = (int)(long)pool->pool_data;
71 void *addr = kmap_local_page((struct page *)element);
72
73 __check_element(pool, addr, 1UL << (PAGE_SHIFT + order));
74 kunmap_local(addr);
75 }
76 }
77
78 static void __poison_element(void *element, size_t size)
79 {
80 u8 *obj = element;
81
82 memset(obj, POISON_FREE, size - 1);
83 obj[size - 1] = POISON_END;
84 }
85
86 static void poison_element(mempool_t *pool, void *element)
87 {
88 /* Skip poisoning: KASAN might save its metadata in the element. */
89 if (kasan_enabled())
90 return;
91
92 /* Mempools backed by slab allocator */
93 if (pool->alloc == mempool_kmalloc) {
94 __poison_element(element, (size_t)pool->pool_data);
95 } else if (pool->alloc == mempool_alloc_slab) {
96 __poison_element(element, kmem_cache_size(pool->pool_data));
97 } else if (pool->alloc == mempool_alloc_pages) {
98 /* Mempools backed by page allocator */
99 int order = (int)(long)pool->pool_data;
100 void *addr = kmap_local_page((struct page *)element);
101
102 __poison_element(addr, 1UL << (PAGE_SHIFT + order));
103 kunmap_local(addr);
104 }
105 }
106 #else /* CONFIG_SLUB_DEBUG_ON */
107 static inline void check_element(mempool_t *pool, void *element)
108 {
109 }
110 static inline void poison_element(mempool_t *pool, void *element)
111 {
112 }
113 #endif /* CONFIG_SLUB_DEBUG_ON */
114
115 static __always_inline bool kasan_poison_element(mempool_t *pool, void *element)
116 {
117 if (pool->alloc == mempool_alloc_slab || pool->alloc == mempool_kmalloc)
118 return kasan_mempool_poison_object(element);
119 else if (pool->alloc == mempool_alloc_pages)
120 return kasan_mempool_poison_pages(element,
121 (unsigned long)pool->pool_data);
122 return true;
123 }
124
125 static void kasan_unpoison_element(mempool_t *pool, void *element)
126 {
127 if (pool->alloc == mempool_kmalloc)
128 kasan_mempool_unpoison_object(element, (size_t)pool->pool_data);
129 else if (pool->alloc == mempool_alloc_slab)
130 kasan_mempool_unpoison_object(element,
131 kmem_cache_size(pool->pool_data));
132 else if (pool->alloc == mempool_alloc_pages)
133 kasan_mempool_unpoison_pages(element,
134 (unsigned long)pool->pool_data);
135 }
136
137 static __always_inline void add_element(mempool_t *pool, void *element)
138 {
139 BUG_ON(pool->curr_nr >= pool->min_nr);
140 poison_element(pool, element);
141 if (kasan_poison_element(pool, element))
142 pool->elements[pool->curr_nr++] = element;
143 }
144
145 static void *remove_element(mempool_t *pool)
146 {
147 void *element = pool->elements[--pool->curr_nr];
148
149 BUG_ON(pool->curr_nr < 0);
150 kasan_unpoison_element(pool, element);
151 check_element(pool, element);
152 return element;
153 }
154
155 /**
156 * mempool_exit - exit a mempool initialized with mempool_init()
157 * @pool: pointer to the memory pool which was initialized with
158 * mempool_init().
159 *
160 * Free all reserved elements in @pool and @pool itself. This function
161 * only sleeps if the free_fn() function sleeps.
162 *
163 * May be called on a zeroed but uninitialized mempool (i.e. allocated with
164 * kzalloc()).
165 */
166 void mempool_exit(mempool_t *pool)
167 {
168 while (pool->curr_nr) {
169 void *element = remove_element(pool);
170 pool->free(element, pool->pool_data);
171 }
172 kfree(pool->elements);
173 pool->elements = NULL;
174 }
175 EXPORT_SYMBOL(mempool_exit);
176
177 /**
178 * mempool_destroy - deallocate a memory pool
179 * @pool: pointer to the memory pool which was allocated via
180 * mempool_create().
181 *
182 * Free all reserved elements in @pool and @pool itself. This function
183 * only sleeps if the free_fn() function sleeps.
184 */
185 void mempool_destroy(mempool_t *pool)
186 {
187 if (unlikely(!pool))
188 return;
189
190 mempool_exit(pool);
191 kfree(pool);
192 }
193 EXPORT_SYMBOL(mempool_destroy);
194
195 int mempool_init_node(mempool_t *pool, int min_nr, mempool_alloc_t *alloc_fn,
196 mempool_free_t *free_fn, void *pool_data,
197 gfp_t gfp_mask, int node_id)
198 {
199 spin_lock_init(&pool->lock);
200 pool->min_nr = min_nr;
201 pool->pool_data = pool_data;
202 pool->alloc = alloc_fn;
203 pool->free = free_fn;
204 init_waitqueue_head(&pool->wait);
205
206 pool->elements = kmalloc_array_node(min_nr, sizeof(void *),
207 gfp_mask, node_id);
208 if (!pool->elements)
209 return -ENOMEM;
210
211 /*
212 * First pre-allocate the guaranteed number of buffers.
213 */
214 while (pool->curr_nr < pool->min_nr) {
215 void *element;
216
217 element = pool->alloc(gfp_mask, pool->pool_data);
218 if (unlikely(!element)) {
219 mempool_exit(pool);
220 return -ENOMEM;
221 }
222 add_element(pool, element);
223 }
224
225 return 0;
226 }
227 EXPORT_SYMBOL(mempool_init_node);
228
229 /**
230 * mempool_init - initialize a memory pool
231 * @pool: pointer to the memory pool that should be initialized
232 * @min_nr: the minimum number of elements guaranteed to be
233 * allocated for this pool.
234 * @alloc_fn: user-defined element-allocation function.
235 * @free_fn: user-defined element-freeing function.
236 * @pool_data: optional private data available to the user-defined functions.
237 *
238 * Like mempool_create(), but initializes the pool in (i.e. embedded in another
239 * structure).
240 *
241 * Return: %0 on success, negative error code otherwise.
242 */
243 int mempool_init_noprof(mempool_t *pool, int min_nr, mempool_alloc_t *alloc_fn,
244 mempool_free_t *free_fn, void *pool_data)
245 {
246 return mempool_init_node(pool, min_nr, alloc_fn, free_fn,
247 pool_data, GFP_KERNEL, NUMA_NO_NODE);
248
249 }
250 EXPORT_SYMBOL(mempool_init_noprof);
251
252 /**
253 * mempool_create_node - create a memory pool
254 * @min_nr: the minimum number of elements guaranteed to be
255 * allocated for this pool.
256 * @alloc_fn: user-defined element-allocation function.
257 * @free_fn: user-defined element-freeing function.
258 * @pool_data: optional private data available to the user-defined functions.
259 * @gfp_mask: memory allocation flags
260 * @node_id: numa node to allocate on
261 *
262 * this function creates and allocates a guaranteed size, preallocated
263 * memory pool. The pool can be used from the mempool_alloc() and mempool_free()
264 * functions. This function might sleep. Both the alloc_fn() and the free_fn()
265 * functions might sleep - as long as the mempool_alloc() function is not called
266 * from IRQ contexts.
267 *
268 * Return: pointer to the created memory pool object or %NULL on error.
269 */
270 mempool_t *mempool_create_node_noprof(int min_nr, mempool_alloc_t *alloc_fn,
271 mempool_free_t *free_fn, void *pool_data,
272 gfp_t gfp_mask, int node_id)
273 {
274 mempool_t *pool;
275
276 pool = kmalloc_node_noprof(sizeof(*pool), gfp_mask | __GFP_ZERO, node_id);
277 if (!pool)
278 return NULL;
279
280 if (mempool_init_node(pool, min_nr, alloc_fn, free_fn, pool_data,
281 gfp_mask, node_id)) {
282 kfree(pool);
283 return NULL;
284 }
285
286 return pool;
287 }
288 EXPORT_SYMBOL(mempool_create_node_noprof);
289
290 /**
291 * mempool_resize - resize an existing memory pool
292 * @pool: pointer to the memory pool which was allocated via
293 * mempool_create().
294 * @new_min_nr: the new minimum number of elements guaranteed to be
295 * allocated for this pool.
296 *
297 * This function shrinks/grows the pool. In the case of growing,
298 * it cannot be guaranteed that the pool will be grown to the new
299 * size immediately, but new mempool_free() calls will refill it.
300 * This function may sleep.
301 *
302 * Note, the caller must guarantee that no mempool_destroy is called
303 * while this function is running. mempool_alloc() & mempool_free()
304 * might be called (eg. from IRQ contexts) while this function executes.
305 *
306 * Return: %0 on success, negative error code otherwise.
307 */
308 int mempool_resize(mempool_t *pool, int new_min_nr)
309 {
310 void *element;
311 void **new_elements;
312 unsigned long flags;
313
314 BUG_ON(new_min_nr <= 0);
315 might_sleep();
316
317 spin_lock_irqsave(&pool->lock, flags);
318 if (new_min_nr <= pool->min_nr) {
319 while (new_min_nr < pool->curr_nr) {
320 element = remove_element(pool);
321 spin_unlock_irqrestore(&pool->lock, flags);
322 pool->free(element, pool->pool_data);
323 spin_lock_irqsave(&pool->lock, flags);
324 }
325 pool->min_nr = new_min_nr;
326 goto out_unlock;
327 }
328 spin_unlock_irqrestore(&pool->lock, flags);
329
330 /* Grow the pool */
331 new_elements = kmalloc_array(new_min_nr, sizeof(*new_elements),
332 GFP_KERNEL);
333 if (!new_elements)
334 return -ENOMEM;
335
336 spin_lock_irqsave(&pool->lock, flags);
337 if (unlikely(new_min_nr <= pool->min_nr)) {
338 /* Raced, other resize will do our work */
339 spin_unlock_irqrestore(&pool->lock, flags);
340 kfree(new_elements);
341 goto out;
342 }
343 memcpy(new_elements, pool->elements,
344 pool->curr_nr * sizeof(*new_elements));
345 kfree(pool->elements);
346 pool->elements = new_elements;
347 pool->min_nr = new_min_nr;
348
349 while (pool->curr_nr < pool->min_nr) {
350 spin_unlock_irqrestore(&pool->lock, flags);
351 element = pool->alloc(GFP_KERNEL, pool->pool_data);
352 if (!element)
353 goto out;
354 spin_lock_irqsave(&pool->lock, flags);
355 if (pool->curr_nr < pool->min_nr) {
356 add_element(pool, element);
357 } else {
358 spin_unlock_irqrestore(&pool->lock, flags);
359 pool->free(element, pool->pool_data); /* Raced */
360 goto out;
361 }
362 }
363 out_unlock:
364 spin_unlock_irqrestore(&pool->lock, flags);
365 out:
366 return 0;
367 }
368 EXPORT_SYMBOL(mempool_resize);
369
370 /**
371 * mempool_alloc - allocate an element from a specific memory pool
372 * @pool: pointer to the memory pool which was allocated via
373 * mempool_create().
374 * @gfp_mask: the usual allocation bitmask.
375 *
376 * this function only sleeps if the alloc_fn() function sleeps or
377 * returns NULL. Note that due to preallocation, this function
378 * *never* fails when called from process contexts. (it might
379 * fail if called from an IRQ context.)
380 * Note: using __GFP_ZERO is not supported.
381 *
382 * Return: pointer to the allocated element or %NULL on error.
383 */
384 void *mempool_alloc_noprof(mempool_t *pool, gfp_t gfp_mask)
385 {
386 void *element;
387 unsigned long flags;
388 wait_queue_entry_t wait;
389 gfp_t gfp_temp;
390
391 VM_WARN_ON_ONCE(gfp_mask & __GFP_ZERO);
392 might_alloc(gfp_mask);
393
394 gfp_mask |= __GFP_NOMEMALLOC; /* don't allocate emergency reserves */
395 gfp_mask |= __GFP_NORETRY; /* don't loop in __alloc_pages */
396 gfp_mask |= __GFP_NOWARN; /* failures are OK */
397
398 gfp_temp = gfp_mask & ~(__GFP_DIRECT_RECLAIM|__GFP_IO);
399
400 repeat_alloc:
401
402 element = pool->alloc(gfp_temp, pool->pool_data);
403 if (likely(element != NULL))
404 return element;
405
406 spin_lock_irqsave(&pool->lock, flags);
407 if (likely(pool->curr_nr)) {
408 element = remove_element(pool);
409 spin_unlock_irqrestore(&pool->lock, flags);
410 /* paired with rmb in mempool_free(), read comment there */
411 smp_wmb();
412 /*
413 * Update the allocation stack trace as this is more useful
414 * for debugging.
415 */
416 kmemleak_update_trace(element);
417 return element;
418 }
419
420 /*
421 * We use gfp mask w/o direct reclaim or IO for the first round. If
422 * alloc failed with that and @pool was empty, retry immediately.
423 */
424 if (gfp_temp != gfp_mask) {
425 spin_unlock_irqrestore(&pool->lock, flags);
426 gfp_temp = gfp_mask;
427 goto repeat_alloc;
428 }
429
430 /* We must not sleep if !__GFP_DIRECT_RECLAIM */
431 if (!(gfp_mask & __GFP_DIRECT_RECLAIM)) {
432 spin_unlock_irqrestore(&pool->lock, flags);
433 return NULL;
434 }
435
436 /* Let's wait for someone else to return an element to @pool */
437 init_wait(&wait);
438 prepare_to_wait(&pool->wait, &wait, TASK_UNINTERRUPTIBLE);
439
440 spin_unlock_irqrestore(&pool->lock, flags);
441
442 /*
443 * FIXME: this should be io_schedule(). The timeout is there as a
444 * workaround for some DM problems in 2.6.18.
445 */
446 io_schedule_timeout(5*HZ);
447
448 finish_wait(&pool->wait, &wait);
449 goto repeat_alloc;
450 }
451 EXPORT_SYMBOL(mempool_alloc_noprof);
452
453 /**
454 * mempool_alloc_preallocated - allocate an element from preallocated elements
455 * belonging to a specific memory pool
456 * @pool: pointer to the memory pool which was allocated via
457 * mempool_create().
458 *
459 * This function is similar to mempool_alloc, but it only attempts allocating
460 * an element from the preallocated elements. It does not sleep and immediately
461 * returns if no preallocated elements are available.
462 *
463 * Return: pointer to the allocated element or %NULL if no elements are
464 * available.
465 */
466 void *mempool_alloc_preallocated(mempool_t *pool)
467 {
468 void *element;
469 unsigned long flags;
470
471 spin_lock_irqsave(&pool->lock, flags);
472 if (likely(pool->curr_nr)) {
473 element = remove_element(pool);
474 spin_unlock_irqrestore(&pool->lock, flags);
475 /* paired with rmb in mempool_free(), read comment there */
476 smp_wmb();
477 /*
478 * Update the allocation stack trace as this is more useful
479 * for debugging.
480 */
481 kmemleak_update_trace(element);
482 return element;
483 }
484 spin_unlock_irqrestore(&pool->lock, flags);
485
486 return NULL;
487 }
488 EXPORT_SYMBOL(mempool_alloc_preallocated);
489
490 /**
491 * mempool_free - return an element to the pool.
492 * @element: pool element pointer.
493 * @pool: pointer to the memory pool which was allocated via
494 * mempool_create().
495 *
496 * this function only sleeps if the free_fn() function sleeps.
497 */
498 void mempool_free(void *element, mempool_t *pool)
499 {
500 unsigned long flags;
501
502 if (unlikely(element == NULL))
503 return;
504
505 /*
506 * Paired with the wmb in mempool_alloc(). The preceding read is
507 * for @element and the following @pool->curr_nr. This ensures
508 * that the visible value of @pool->curr_nr is from after the
509 * allocation of @element. This is necessary for fringe cases
510 * where @element was passed to this task without going through
511 * barriers.
512 *
513 * For example, assume @p is %NULL at the beginning and one task
514 * performs "p = mempool_alloc(...);" while another task is doing
515 * "while (!p) cpu_relax(); mempool_free(p, ...);". This function
516 * may end up using curr_nr value which is from before allocation
517 * of @p without the following rmb.
518 */
519 smp_rmb();
520
521 /*
522 * For correctness, we need a test which is guaranteed to trigger
523 * if curr_nr + #allocated == min_nr. Testing curr_nr < min_nr
524 * without locking achieves that and refilling as soon as possible
525 * is desirable.
526 *
527 * Because curr_nr visible here is always a value after the
528 * allocation of @element, any task which decremented curr_nr below
529 * min_nr is guaranteed to see curr_nr < min_nr unless curr_nr gets
530 * incremented to min_nr afterwards. If curr_nr gets incremented
531 * to min_nr after the allocation of @element, the elements
532 * allocated after that are subject to the same guarantee.
533 *
534 * Waiters happen iff curr_nr is 0 and the above guarantee also
535 * ensures that there will be frees which return elements to the
536 * pool waking up the waiters.
537 */
538 if (unlikely(READ_ONCE(pool->curr_nr) < pool->min_nr)) {
539 spin_lock_irqsave(&pool->lock, flags);
540 if (likely(pool->curr_nr < pool->min_nr)) {
541 add_element(pool, element);
542 spin_unlock_irqrestore(&pool->lock, flags);
543 wake_up(&pool->wait);
544 return;
545 }
546 spin_unlock_irqrestore(&pool->lock, flags);
547 }
548 pool->free(element, pool->pool_data);
549 }
550 EXPORT_SYMBOL(mempool_free);
551
552 /*
553 * A commonly used alloc and free fn.
554 */
555 void *mempool_alloc_slab(gfp_t gfp_mask, void *pool_data)
556 {
557 struct kmem_cache *mem = pool_data;
558 VM_BUG_ON(mem->ctor);
559 return kmem_cache_alloc_noprof(mem, gfp_mask);
560 }
561 EXPORT_SYMBOL(mempool_alloc_slab);
562
563 void mempool_free_slab(void *element, void *pool_data)
564 {
565 struct kmem_cache *mem = pool_data;
566 kmem_cache_free(mem, element);
567 }
568 EXPORT_SYMBOL(mempool_free_slab);
569
570 /*
571 * A commonly used alloc and free fn that kmalloc/kfrees the amount of memory
572 * specified by pool_data
573 */
574 void *mempool_kmalloc(gfp_t gfp_mask, void *pool_data)
575 {
576 size_t size = (size_t)pool_data;
577 return kmalloc_noprof(size, gfp_mask);
578 }
579 EXPORT_SYMBOL(mempool_kmalloc);
580
581 void mempool_kfree(void *element, void *pool_data)
582 {
583 kfree(element);
584 }
585 EXPORT_SYMBOL(mempool_kfree);
586
587 void *mempool_kvmalloc(gfp_t gfp_mask, void *pool_data)
588 {
589 size_t size = (size_t)pool_data;
590 return kvmalloc(size, gfp_mask);
591 }
592 EXPORT_SYMBOL(mempool_kvmalloc);
593
594 void mempool_kvfree(void *element, void *pool_data)
595 {
596 kvfree(element);
597 }
598 EXPORT_SYMBOL(mempool_kvfree);
599
600 /*
601 * A simple mempool-backed page allocator that allocates pages
602 * of the order specified by pool_data.
603 */
604 void *mempool_alloc_pages(gfp_t gfp_mask, void *pool_data)
605 {
606 int order = (int)(long)pool_data;
607 return alloc_pages_noprof(gfp_mask, order);
608 }
609 EXPORT_SYMBOL(mempool_alloc_pages);
610
611 void mempool_free_pages(void *element, void *pool_data)
612 {
613 int order = (int)(long)pool_data;
614 __free_pages(element, order);
615 }
616 EXPORT_SYMBOL(mempool_free_pages);
617
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