1// SPDX-License-Identifier: GPL-2.0
2/*
3 * memory buffer pool support. Such pools are mostly used
4 * for guaranteed, deadlock-free memory allocations during
5 * extreme VM load.
6 *
7 * started by Ingo Molnar, Copyright (C) 2001
8 * debugging by David Rientjes, Copyright (C) 2015
9 */
10#include <linux/fault-inject.h>
11#include <linux/mm.h>
12#include <linux/slab.h>
13#include <linux/highmem.h>
14#include <linux/kasan.h>
15#include <linux/kmemleak.h>
16#include <linux/export.h>
17#include <linux/mempool.h>
18#include <linux/writeback.h>
19#include "slab.h"
20
21static DECLARE_FAULT_ATTR(fail_mempool_alloc);
22static DECLARE_FAULT_ATTR(fail_mempool_alloc_bulk);
23
24static int __init mempool_faul_inject_init(void)
25{
26 int error;
27
28 error = PTR_ERR_OR_ZERO(ptr: fault_create_debugfs_attr(name: "fail_mempool_alloc",
29 NULL, attr: &fail_mempool_alloc));
30 if (error)
31 return error;
32
33 /* booting will fail on error return here, don't bother to cleanup */
34 return PTR_ERR_OR_ZERO(
35 ptr: fault_create_debugfs_attr(name: "fail_mempool_alloc_bulk", NULL,
36 attr: &fail_mempool_alloc_bulk));
37}
38late_initcall(mempool_faul_inject_init);
39
40#ifdef CONFIG_SLUB_DEBUG_ON
41static void poison_error(struct mempool *pool, void *element, size_t size,
42 size_t byte)
43{
44 const int nr = pool->curr_nr;
45 const int start = max_t(int, byte - (BITS_PER_LONG / 8), 0);
46 const int end = min_t(int, byte + (BITS_PER_LONG / 8), size);
47 int i;
48
49 pr_err("BUG: mempool element poison mismatch\n");
50 pr_err("Mempool %p size %zu\n", pool, size);
51 pr_err(" nr=%d @ %p: %s0x", nr, element, start > 0 ? "... " : "");
52 for (i = start; i < end; i++)
53 pr_cont("%x ", *(u8 *)(element + i));
54 pr_cont("%s\n", end < size ? "..." : "");
55 dump_stack();
56}
57
58static void __check_element(struct mempool *pool, void *element, size_t size)
59{
60 u8 *obj = element;
61 size_t i;
62
63 for (i = 0; i < size; i++) {
64 u8 exp = (i < size - 1) ? POISON_FREE : POISON_END;
65
66 if (obj[i] != exp) {
67 poison_error(pool, element, size, byte: i);
68 return;
69 }
70 }
71 memset(obj, POISON_INUSE, size);
72}
73
74static void check_element(struct mempool *pool, void *element)
75{
76 /* Skip checking: KASAN might save its metadata in the element. */
77 if (kasan_enabled())
78 return;
79
80 /* Mempools backed by slab allocator */
81 if (pool->free == mempool_kfree) {
82 __check_element(pool, element, size: (size_t)pool->pool_data);
83 } else if (pool->free == mempool_free_slab) {
84 __check_element(pool, element, size: kmem_cache_size(s: pool->pool_data));
85 } else if (pool->free == mempool_free_pages) {
86 /* Mempools backed by page allocator */
87 int order = (int)(long)pool->pool_data;
88
89#ifdef CONFIG_HIGHMEM
90 for (int i = 0; i < (1 << order); i++) {
91 struct page *page = (struct page *)element;
92 void *addr = kmap_local_page(page + i);
93
94 __check_element(pool, addr, PAGE_SIZE);
95 kunmap_local(addr);
96 }
97#else
98 void *addr = page_address((struct page *)element);
99
100 __check_element(pool, element: addr, PAGE_SIZE << order);
101#endif
102 }
103}
104
105static void __poison_element(void *element, size_t size)
106{
107 u8 *obj = element;
108
109 memset(obj, POISON_FREE, size - 1);
110 obj[size - 1] = POISON_END;
111}
112
113static void poison_element(struct mempool *pool, void *element)
114{
115 /* Skip poisoning: KASAN might save its metadata in the element. */
116 if (kasan_enabled())
117 return;
118
119 /* Mempools backed by slab allocator */
120 if (pool->alloc == mempool_kmalloc) {
121 __poison_element(element, size: (size_t)pool->pool_data);
122 } else if (pool->alloc == mempool_alloc_slab) {
123 __poison_element(element, size: kmem_cache_size(s: pool->pool_data));
124 } else if (pool->alloc == mempool_alloc_pages) {
125 /* Mempools backed by page allocator */
126 int order = (int)(long)pool->pool_data;
127
128#ifdef CONFIG_HIGHMEM
129 for (int i = 0; i < (1 << order); i++) {
130 struct page *page = (struct page *)element;
131 void *addr = kmap_local_page(page + i);
132
133 __poison_element(addr, PAGE_SIZE);
134 kunmap_local(addr);
135 }
136#else
137 void *addr = page_address((struct page *)element);
138
139 __poison_element(element: addr, PAGE_SIZE << order);
140#endif
141 }
142}
143#else /* CONFIG_SLUB_DEBUG_ON */
144static inline void check_element(struct mempool *pool, void *element)
145{
146}
147static inline void poison_element(struct mempool *pool, void *element)
148{
149}
150#endif /* CONFIG_SLUB_DEBUG_ON */
151
152static __always_inline bool kasan_poison_element(struct mempool *pool,
153 void *element)
154{
155 if (pool->alloc == mempool_alloc_slab || pool->alloc == mempool_kmalloc)
156 return kasan_mempool_poison_object(ptr: element);
157 else if (pool->alloc == mempool_alloc_pages)
158 return kasan_mempool_poison_pages(page: element,
159 order: (unsigned long)pool->pool_data);
160 return true;
161}
162
163static void kasan_unpoison_element(struct mempool *pool, void *element)
164{
165 if (pool->alloc == mempool_kmalloc)
166 kasan_mempool_unpoison_object(ptr: element, size: (size_t)pool->pool_data);
167 else if (pool->alloc == mempool_alloc_slab)
168 kasan_mempool_unpoison_object(ptr: element,
169 size: kmem_cache_size(s: pool->pool_data));
170 else if (pool->alloc == mempool_alloc_pages)
171 kasan_mempool_unpoison_pages(page: element,
172 order: (unsigned long)pool->pool_data);
173}
174
175static __always_inline void add_element(struct mempool *pool, void *element)
176{
177 BUG_ON(pool->min_nr != 0 && pool->curr_nr >= pool->min_nr);
178 poison_element(pool, element);
179 if (kasan_poison_element(pool, element))
180 pool->elements[pool->curr_nr++] = element;
181}
182
183static void *remove_element(struct mempool *pool)
184{
185 void *element = pool->elements[--pool->curr_nr];
186
187 BUG_ON(pool->curr_nr < 0);
188 kasan_unpoison_element(pool, element);
189 check_element(pool, element);
190 return element;
191}
192
193/**
194 * mempool_exit - exit a mempool initialized with mempool_init()
195 * @pool: pointer to the memory pool which was initialized with
196 * mempool_init().
197 *
198 * Free all reserved elements in @pool and @pool itself. This function
199 * only sleeps if the free_fn() function sleeps.
200 *
201 * May be called on a zeroed but uninitialized mempool (i.e. allocated with
202 * kzalloc()).
203 */
204void mempool_exit(struct mempool *pool)
205{
206 while (pool->curr_nr) {
207 void *element = remove_element(pool);
208 pool->free(element, pool->pool_data);
209 }
210 kfree(objp: pool->elements);
211 pool->elements = NULL;
212}
213EXPORT_SYMBOL(mempool_exit);
214
215/**
216 * mempool_destroy - deallocate a memory pool
217 * @pool: pointer to the memory pool which was allocated via
218 * mempool_create().
219 *
220 * Free all reserved elements in @pool and @pool itself. This function
221 * only sleeps if the free_fn() function sleeps.
222 */
223void mempool_destroy(struct mempool *pool)
224{
225 if (unlikely(!pool))
226 return;
227
228 mempool_exit(pool);
229 kfree(objp: pool);
230}
231EXPORT_SYMBOL(mempool_destroy);
232
233int mempool_init_node(struct mempool *pool, int min_nr,
234 mempool_alloc_t *alloc_fn, mempool_free_t *free_fn,
235 void *pool_data, gfp_t gfp_mask, int node_id)
236{
237 spin_lock_init(&pool->lock);
238 pool->min_nr = min_nr;
239 pool->pool_data = pool_data;
240 pool->alloc = alloc_fn;
241 pool->free = free_fn;
242 init_waitqueue_head(&pool->wait);
243 /*
244 * max() used here to ensure storage for at least 1 element to support
245 * zero minimum pool
246 */
247 pool->elements = kmalloc_array_node(max(1, min_nr), sizeof(void *),
248 gfp_mask, node_id);
249 if (!pool->elements)
250 return -ENOMEM;
251
252 /*
253 * First pre-allocate the guaranteed number of buffers,
254 * also pre-allocate 1 element for zero minimum pool.
255 */
256 while (pool->curr_nr < max(1, pool->min_nr)) {
257 void *element;
258
259 element = pool->alloc(gfp_mask, pool->pool_data);
260 if (unlikely(!element)) {
261 mempool_exit(pool);
262 return -ENOMEM;
263 }
264 add_element(pool, element);
265 }
266
267 return 0;
268}
269EXPORT_SYMBOL(mempool_init_node);
270
271/**
272 * mempool_init - initialize a memory pool
273 * @pool: pointer to the memory pool that should be initialized
274 * @min_nr: the minimum number of elements guaranteed to be
275 * allocated for this pool.
276 * @alloc_fn: user-defined element-allocation function.
277 * @free_fn: user-defined element-freeing function.
278 * @pool_data: optional private data available to the user-defined functions.
279 *
280 * Like mempool_create(), but initializes the pool in (i.e. embedded in another
281 * structure).
282 *
283 * Return: %0 on success, negative error code otherwise.
284 */
285int mempool_init_noprof(struct mempool *pool, int min_nr,
286 mempool_alloc_t *alloc_fn, mempool_free_t *free_fn,
287 void *pool_data)
288{
289 return mempool_init_node(pool, min_nr, alloc_fn, free_fn,
290 pool_data, GFP_KERNEL, NUMA_NO_NODE);
291
292}
293EXPORT_SYMBOL(mempool_init_noprof);
294
295/**
296 * mempool_create_node - create a memory pool
297 * @min_nr: the minimum number of elements guaranteed to be
298 * allocated for this pool.
299 * @alloc_fn: user-defined element-allocation function.
300 * @free_fn: user-defined element-freeing function.
301 * @pool_data: optional private data available to the user-defined functions.
302 * @gfp_mask: memory allocation flags
303 * @node_id: numa node to allocate on
304 *
305 * this function creates and allocates a guaranteed size, preallocated
306 * memory pool. The pool can be used from the mempool_alloc() and mempool_free()
307 * functions. This function might sleep. Both the alloc_fn() and the free_fn()
308 * functions might sleep - as long as the mempool_alloc() function is not called
309 * from IRQ contexts.
310 *
311 * Return: pointer to the created memory pool object or %NULL on error.
312 */
313struct mempool *mempool_create_node_noprof(int min_nr,
314 mempool_alloc_t *alloc_fn, mempool_free_t *free_fn,
315 void *pool_data, gfp_t gfp_mask, int node_id)
316{
317 struct mempool *pool;
318
319 pool = kmalloc_node_noprof(size: sizeof(*pool), flags: gfp_mask | __GFP_ZERO, node: node_id);
320 if (!pool)
321 return NULL;
322
323 if (mempool_init_node(pool, min_nr, alloc_fn, free_fn, pool_data,
324 gfp_mask, node_id)) {
325 kfree(objp: pool);
326 return NULL;
327 }
328
329 return pool;
330}
331EXPORT_SYMBOL(mempool_create_node_noprof);
332
333/**
334 * mempool_resize - resize an existing memory pool
335 * @pool: pointer to the memory pool which was allocated via
336 * mempool_create().
337 * @new_min_nr: the new minimum number of elements guaranteed to be
338 * allocated for this pool.
339 *
340 * This function shrinks/grows the pool. In the case of growing,
341 * it cannot be guaranteed that the pool will be grown to the new
342 * size immediately, but new mempool_free() calls will refill it.
343 * This function may sleep.
344 *
345 * Note, the caller must guarantee that no mempool_destroy is called
346 * while this function is running. mempool_alloc() & mempool_free()
347 * might be called (eg. from IRQ contexts) while this function executes.
348 *
349 * Return: %0 on success, negative error code otherwise.
350 */
351int mempool_resize(struct mempool *pool, int new_min_nr)
352{
353 void *element;
354 void **new_elements;
355 unsigned long flags;
356
357 BUG_ON(new_min_nr <= 0);
358 might_sleep();
359
360 spin_lock_irqsave(&pool->lock, flags);
361 if (new_min_nr <= pool->min_nr) {
362 while (new_min_nr < pool->curr_nr) {
363 element = remove_element(pool);
364 spin_unlock_irqrestore(lock: &pool->lock, flags);
365 pool->free(element, pool->pool_data);
366 spin_lock_irqsave(&pool->lock, flags);
367 }
368 pool->min_nr = new_min_nr;
369 goto out_unlock;
370 }
371 spin_unlock_irqrestore(lock: &pool->lock, flags);
372
373 /* Grow the pool */
374 new_elements = kmalloc_array(new_min_nr, sizeof(*new_elements),
375 GFP_KERNEL);
376 if (!new_elements)
377 return -ENOMEM;
378
379 spin_lock_irqsave(&pool->lock, flags);
380 if (unlikely(new_min_nr <= pool->min_nr)) {
381 /* Raced, other resize will do our work */
382 spin_unlock_irqrestore(lock: &pool->lock, flags);
383 kfree(objp: new_elements);
384 goto out;
385 }
386 memcpy(new_elements, pool->elements,
387 pool->curr_nr * sizeof(*new_elements));
388 kfree(objp: pool->elements);
389 pool->elements = new_elements;
390 pool->min_nr = new_min_nr;
391
392 while (pool->curr_nr < pool->min_nr) {
393 spin_unlock_irqrestore(lock: &pool->lock, flags);
394 element = pool->alloc(GFP_KERNEL, pool->pool_data);
395 if (!element)
396 goto out;
397 spin_lock_irqsave(&pool->lock, flags);
398 if (pool->curr_nr < pool->min_nr) {
399 add_element(pool, element);
400 } else {
401 spin_unlock_irqrestore(lock: &pool->lock, flags);
402 pool->free(element, pool->pool_data); /* Raced */
403 goto out;
404 }
405 }
406out_unlock:
407 spin_unlock_irqrestore(lock: &pool->lock, flags);
408out:
409 return 0;
410}
411EXPORT_SYMBOL(mempool_resize);
412
413static unsigned int mempool_alloc_from_pool(struct mempool *pool, void **elems,
414 unsigned int count, unsigned int allocated,
415 gfp_t gfp_mask)
416{
417 unsigned long flags;
418 unsigned int i;
419
420 spin_lock_irqsave(&pool->lock, flags);
421 if (unlikely(pool->curr_nr < count - allocated))
422 goto fail;
423 for (i = 0; i < count; i++) {
424 if (!elems[i]) {
425 elems[i] = remove_element(pool);
426 allocated++;
427 }
428 }
429 spin_unlock_irqrestore(lock: &pool->lock, flags);
430
431 /* Paired with rmb in mempool_free(), read comment there. */
432 smp_wmb();
433
434 /*
435 * Update the allocation stack trace as this is more useful for
436 * debugging.
437 */
438 for (i = 0; i < count; i++)
439 kmemleak_update_trace(ptr: elems[i]);
440 return allocated;
441
442fail:
443 if (gfp_mask & __GFP_DIRECT_RECLAIM) {
444 DEFINE_WAIT(wait);
445
446 prepare_to_wait(wq_head: &pool->wait, wq_entry: &wait, TASK_UNINTERRUPTIBLE);
447 spin_unlock_irqrestore(lock: &pool->lock, flags);
448
449 /*
450 * Wait for someone else to return an element to @pool, but wake
451 * up occasionally as memory pressure might have reduced even
452 * and the normal allocation in alloc_fn could succeed even if
453 * no element was returned.
454 */
455 io_schedule_timeout(timeout: 5 * HZ);
456 finish_wait(wq_head: &pool->wait, wq_entry: &wait);
457 } else {
458 /* We must not sleep if __GFP_DIRECT_RECLAIM is not set. */
459 spin_unlock_irqrestore(lock: &pool->lock, flags);
460 }
461
462 return allocated;
463}
464
465/*
466 * Adjust the gfp flags for mempool allocations, as we never want to dip into
467 * the global emergency reserves or retry in the page allocator.
468 *
469 * The first pass also doesn't want to go reclaim, but the next passes do, so
470 * return a separate subset for that first iteration.
471 */
472static inline gfp_t mempool_adjust_gfp(gfp_t *gfp_mask)
473{
474 *gfp_mask |= __GFP_NOMEMALLOC | __GFP_NORETRY | __GFP_NOWARN;
475 return *gfp_mask & ~(__GFP_DIRECT_RECLAIM | __GFP_IO);
476}
477
478/**
479 * mempool_alloc_bulk - allocate multiple elements from a memory pool
480 * @pool: pointer to the memory pool
481 * @elems: partially or fully populated elements array
482 * @count: number of entries in @elem that need to be allocated
483 * @allocated: number of entries in @elem already allocated
484 *
485 * Allocate elements for each slot in @elem that is non-%NULL. This is done by
486 * first calling into the alloc_fn supplied at pool initialization time, and
487 * dipping into the reserved pool when alloc_fn fails to allocate an element.
488 *
489 * On return all @count elements in @elems will be populated.
490 *
491 * Return: Always 0. If it wasn't for %$#^$ alloc tags, it would return void.
492 */
493int mempool_alloc_bulk_noprof(struct mempool *pool, void **elems,
494 unsigned int count, unsigned int allocated)
495{
496 gfp_t gfp_mask = GFP_KERNEL;
497 gfp_t gfp_temp = mempool_adjust_gfp(gfp_mask: &gfp_mask);
498 unsigned int i = 0;
499
500 VM_WARN_ON_ONCE(count > pool->min_nr);
501 might_alloc(gfp_mask);
502
503 /*
504 * If an error is injected, fail all elements in a bulk allocation so
505 * that we stress the multiple elements missing path.
506 */
507 if (should_fail_ex(attr: &fail_mempool_alloc_bulk, size: 1, flags: FAULT_NOWARN)) {
508 pr_info("forcing mempool usage for %pS\n",
509 (void *)_RET_IP_);
510 goto use_pool;
511 }
512
513repeat_alloc:
514 /*
515 * Try to allocate the elements using the allocation callback first as
516 * that might succeed even when the caller's bulk allocation did not.
517 */
518 for (i = 0; i < count; i++) {
519 if (elems[i])
520 continue;
521 elems[i] = pool->alloc(gfp_temp, pool->pool_data);
522 if (unlikely(!elems[i]))
523 goto use_pool;
524 allocated++;
525 }
526
527 return 0;
528
529use_pool:
530 allocated = mempool_alloc_from_pool(pool, elems, count, allocated,
531 gfp_mask: gfp_temp);
532 gfp_temp = gfp_mask;
533 goto repeat_alloc;
534}
535EXPORT_SYMBOL_GPL(mempool_alloc_bulk_noprof);
536
537/**
538 * mempool_alloc - allocate an element from a memory pool
539 * @pool: pointer to the memory pool
540 * @gfp_mask: GFP_* flags. %__GFP_ZERO is not supported.
541 *
542 * Allocate an element from @pool. This is done by first calling into the
543 * alloc_fn supplied at pool initialization time, and dipping into the reserved
544 * pool when alloc_fn fails to allocate an element.
545 *
546 * This function only sleeps if the alloc_fn callback sleeps, or when waiting
547 * for elements to become available in the pool.
548 *
549 * Return: pointer to the allocated element or %NULL when failing to allocate
550 * an element. Allocation failure can only happen when @gfp_mask does not
551 * include %__GFP_DIRECT_RECLAIM.
552 */
553void *mempool_alloc_noprof(struct mempool *pool, gfp_t gfp_mask)
554{
555 gfp_t gfp_temp = mempool_adjust_gfp(gfp_mask: &gfp_mask);
556 void *element;
557
558 VM_WARN_ON_ONCE(gfp_mask & __GFP_ZERO);
559 might_alloc(gfp_mask);
560
561repeat_alloc:
562 if (should_fail_ex(attr: &fail_mempool_alloc, size: 1, flags: FAULT_NOWARN)) {
563 pr_info("forcing mempool usage for %pS\n",
564 (void *)_RET_IP_);
565 element = NULL;
566 } else {
567 element = pool->alloc(gfp_temp, pool->pool_data);
568 }
569
570 if (unlikely(!element)) {
571 /*
572 * Try to allocate an element from the pool.
573 *
574 * The first pass won't have __GFP_DIRECT_RECLAIM and won't
575 * sleep in mempool_alloc_from_pool. Retry the allocation
576 * with all flags set in that case.
577 */
578 if (!mempool_alloc_from_pool(pool, elems: &element, count: 1, allocated: 0, gfp_mask: gfp_temp)) {
579 if (gfp_temp != gfp_mask) {
580 gfp_temp = gfp_mask;
581 goto repeat_alloc;
582 }
583 if (gfp_mask & __GFP_DIRECT_RECLAIM) {
584 goto repeat_alloc;
585 }
586 }
587 }
588
589 return element;
590}
591EXPORT_SYMBOL(mempool_alloc_noprof);
592
593/**
594 * mempool_alloc_preallocated - allocate an element from preallocated elements
595 * belonging to a memory pool
596 * @pool: pointer to the memory pool
597 *
598 * This function is similar to mempool_alloc(), but it only attempts allocating
599 * an element from the preallocated elements. It only takes a single spinlock_t
600 * and immediately returns if no preallocated elements are available.
601 *
602 * Return: pointer to the allocated element or %NULL if no elements are
603 * available.
604 */
605void *mempool_alloc_preallocated(struct mempool *pool)
606{
607 void *element = NULL;
608
609 mempool_alloc_from_pool(pool, elems: &element, count: 1, allocated: 0, GFP_NOWAIT);
610 return element;
611}
612EXPORT_SYMBOL(mempool_alloc_preallocated);
613
614/**
615 * mempool_free_bulk - return elements to a mempool
616 * @pool: pointer to the memory pool
617 * @elems: elements to return
618 * @count: number of elements to return
619 *
620 * Returns a number of elements from the start of @elem to @pool if @pool needs
621 * replenishing and sets their slots in @elem to NULL. Other elements are left
622 * in @elem.
623 *
624 * Return: number of elements transferred to @pool. Elements are always
625 * transferred from the beginning of @elem, so the return value can be used as
626 * an offset into @elem for the freeing the remaining elements in the caller.
627 */
628unsigned int mempool_free_bulk(struct mempool *pool, void **elems,
629 unsigned int count)
630{
631 unsigned long flags;
632 unsigned int freed = 0;
633 bool added = false;
634
635 /*
636 * Paired with the wmb in mempool_alloc(). The preceding read is
637 * for @element and the following @pool->curr_nr. This ensures
638 * that the visible value of @pool->curr_nr is from after the
639 * allocation of @element. This is necessary for fringe cases
640 * where @element was passed to this task without going through
641 * barriers.
642 *
643 * For example, assume @p is %NULL at the beginning and one task
644 * performs "p = mempool_alloc(...);" while another task is doing
645 * "while (!p) cpu_relax(); mempool_free(p, ...);". This function
646 * may end up using curr_nr value which is from before allocation
647 * of @p without the following rmb.
648 */
649 smp_rmb();
650
651 /*
652 * For correctness, we need a test which is guaranteed to trigger
653 * if curr_nr + #allocated == min_nr. Testing curr_nr < min_nr
654 * without locking achieves that and refilling as soon as possible
655 * is desirable.
656 *
657 * Because curr_nr visible here is always a value after the
658 * allocation of @element, any task which decremented curr_nr below
659 * min_nr is guaranteed to see curr_nr < min_nr unless curr_nr gets
660 * incremented to min_nr afterwards. If curr_nr gets incremented
661 * to min_nr after the allocation of @element, the elements
662 * allocated after that are subject to the same guarantee.
663 *
664 * Waiters happen iff curr_nr is 0 and the above guarantee also
665 * ensures that there will be frees which return elements to the
666 * pool waking up the waiters.
667 *
668 * For zero-minimum pools, curr_nr < min_nr (0 < 0) never succeeds,
669 * so waiters sleeping on pool->wait would never be woken by the
670 * wake-up path of previous test. This explicit check ensures the
671 * allocation of element when both min_nr and curr_nr are 0, and
672 * any active waiters are properly awakened.
673 */
674 if (unlikely(READ_ONCE(pool->curr_nr) < pool->min_nr)) {
675 spin_lock_irqsave(&pool->lock, flags);
676 while (pool->curr_nr < pool->min_nr && freed < count) {
677 add_element(pool, element: elems[freed++]);
678 added = true;
679 }
680 spin_unlock_irqrestore(lock: &pool->lock, flags);
681 } else if (unlikely(pool->min_nr == 0 &&
682 READ_ONCE(pool->curr_nr) == 0)) {
683 /* Handle the min_nr = 0 edge case: */
684 spin_lock_irqsave(&pool->lock, flags);
685 if (likely(pool->curr_nr == 0)) {
686 add_element(pool, element: elems[freed++]);
687 added = true;
688 }
689 spin_unlock_irqrestore(lock: &pool->lock, flags);
690 }
691
692 if (unlikely(added) && wq_has_sleeper(wq_head: &pool->wait))
693 wake_up(&pool->wait);
694
695 return freed;
696}
697EXPORT_SYMBOL_GPL(mempool_free_bulk);
698
699/**
700 * mempool_free - return an element to the pool.
701 * @element: element to return
702 * @pool: pointer to the memory pool
703 *
704 * Returns @element to @pool if it needs replenishing, else frees it using
705 * the free_fn callback in @pool.
706 *
707 * This function only sleeps if the free_fn callback sleeps.
708 */
709void mempool_free(void *element, struct mempool *pool)
710{
711 if (likely(element) && !mempool_free_bulk(pool, &element, 1))
712 pool->free(element, pool->pool_data);
713}
714EXPORT_SYMBOL(mempool_free);
715
716/*
717 * A commonly used alloc and free fn.
718 */
719void *mempool_alloc_slab(gfp_t gfp_mask, void *pool_data)
720{
721 struct kmem_cache *mem = pool_data;
722 VM_BUG_ON(mem->ctor);
723 return kmem_cache_alloc_noprof(cachep: mem, flags: gfp_mask);
724}
725EXPORT_SYMBOL(mempool_alloc_slab);
726
727void mempool_free_slab(void *element, void *pool_data)
728{
729 struct kmem_cache *mem = pool_data;
730 kmem_cache_free(s: mem, objp: element);
731}
732EXPORT_SYMBOL(mempool_free_slab);
733
734/*
735 * A commonly used alloc and free fn that kmalloc/kfrees the amount of memory
736 * specified by pool_data
737 */
738void *mempool_kmalloc(gfp_t gfp_mask, void *pool_data)
739{
740 size_t size = (size_t)pool_data;
741 return kmalloc_noprof(size, flags: gfp_mask);
742}
743EXPORT_SYMBOL(mempool_kmalloc);
744
745void mempool_kfree(void *element, void *pool_data)
746{
747 kfree(objp: element);
748}
749EXPORT_SYMBOL(mempool_kfree);
750
751/*
752 * A simple mempool-backed page allocator that allocates pages
753 * of the order specified by pool_data.
754 */
755void *mempool_alloc_pages(gfp_t gfp_mask, void *pool_data)
756{
757 int order = (int)(long)pool_data;
758 return alloc_pages_noprof(gfp: gfp_mask, order);
759}
760EXPORT_SYMBOL(mempool_alloc_pages);
761
762void mempool_free_pages(void *element, void *pool_data)
763{
764 int order = (int)(long)pool_data;
765 __free_pages(page: element, order);
766}
767EXPORT_SYMBOL(mempool_free_pages);
768

source code of linux/mm/mempool.c