mempool.c

  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(fault_create_debugfs_attr("fail_mempool_alloc",
 29			NULL, &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		fault_create_debugfs_attr("fail_mempool_alloc_bulk", NULL,
 36		&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, 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_t)pool->pool_data);
 83	} else if (pool->free == mempool_free_slab) {
 84		__check_element(pool, element, kmem_cache_size(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, 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_t)pool->pool_data);
122	} else if (pool->alloc == mempool_alloc_slab) {
123		__poison_element(element, kmem_cache_size(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(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(element);
157	else if (pool->alloc == mempool_alloc_pages)
158		return kasan_mempool_poison_pages(element,
159						(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(element, (size_t)pool->pool_data);
167	else if (pool->alloc == mempool_alloc_slab)
168		kasan_mempool_unpoison_object(element,
169					      kmem_cache_size(pool->pool_data));
170	else if (pool->alloc == mempool_alloc_pages)
171		kasan_mempool_unpoison_pages(element,
172					     (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(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(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(sizeof(*pool), gfp_mask | __GFP_ZERO, 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(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(&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(&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(&pool->lock, flags);
383		kfree(new_elements);
384		goto out;
385	}
386	memcpy(new_elements, pool->elements,
387			pool->curr_nr * sizeof(*new_elements));
388	kfree(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(&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(&pool->lock, flags);
402			pool->free(element, pool->pool_data);	/* Raced */
403			goto out;
404		}
405	}
406out_unlock:
407	spin_unlock_irqrestore(&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(&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(elems[i]);
440	return allocated;
441
442fail:
443	if (gfp_mask & __GFP_DIRECT_RECLAIM) {
444		DEFINE_WAIT(wait);
445
446		prepare_to_wait(&pool->wait, &wait, TASK_UNINTERRUPTIBLE);
447		spin_unlock_irqrestore(&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(5 * HZ);
456		finish_wait(&pool->wait, &wait);
457	} else {
458		/* We must not sleep if __GFP_DIRECT_RECLAIM is not set. */
459		spin_unlock_irqrestore(&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);
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(&fail_mempool_alloc_bulk, 1, 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_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);
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(&fail_mempool_alloc, 1, 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, &element, 1, 0, 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, &element, 1, 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, elems[freed++]);
678			added = true;
679		}
680		spin_unlock_irqrestore(&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, elems[freed++]);
687			added = true;
688		}
689		spin_unlock_irqrestore(&pool->lock, flags);
690	}
691
692	if (unlikely(added) && wq_has_sleeper(&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(mem, 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(mem, 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, gfp_mask);
742}
743EXPORT_SYMBOL(mempool_kmalloc);
744
745void mempool_kfree(void *element, void *pool_data)
746{
747	kfree(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_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(element, order);
766}
767EXPORT_SYMBOL(mempool_free_pages);