1 files changed, 759 insertions, 0 deletions
diff --git a/mm/mempool.c b/mm/mempool.c
new file mode 100644
index 000000000..473a029fa
--- /dev/null
+++ b/mm/mempool.c
@@ -0,0 +1,759 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *  memory buffer pool support. Such pools are mostly used
+ *  for guaranteed, deadlock-free memory allocations during
+ *  extreme VM load.
+ *
+ *  started by Ingo Molnar, Copyright (C) 2001
+ *  debugging by David Rientjes, Copyright (C) 2015
+ */
+#include <linux/fault-inject.h>
+#include <linux/mm.h>
+#include <linux/slab.h>
+#include <linux/highmem.h>
+#include <linux/kasan.h>
+#include <linux/kmemleak.h>
+#include <linux/export.h>
+#include <linux/mempool.h>
+#include <linux/writeback.h>
+#include "slab.h"
+
+static DECLARE_FAULT_ATTR(fail_mempool_alloc);
+static DECLARE_FAULT_ATTR(fail_mempool_alloc_bulk);
+
+static int __init mempool_faul_inject_init(void)
+{
+	int error;
+
+	error = PTR_ERR_OR_ZERO(fault_create_debugfs_attr("fail_mempool_alloc",
+			NULL, &fail_mempool_alloc));
+	if (error)
+		return error;
+
+	/* booting will fail on error return here, don't bother to cleanup */
+	return PTR_ERR_OR_ZERO(
+		fault_create_debugfs_attr("fail_mempool_alloc_bulk", NULL,
+		&fail_mempool_alloc_bulk));
+}
+late_initcall(mempool_faul_inject_init);
+
+#ifdef CONFIG_SLUB_DEBUG_ON
+static void poison_error(struct mempool *pool, void *element, size_t size,
+			 size_t byte)
+{
+	const int nr = pool->curr_nr;
+	const int start = max_t(int, byte - (BITS_PER_LONG / 8), 0);
+	const int end = min_t(int, byte + (BITS_PER_LONG / 8), size);
+	int i;
+
+	pr_err("BUG: mempool element poison mismatch\n");
+	pr_err("Mempool %p size %zu\n", pool, size);
+	pr_err(" nr=%d @ %p: %s0x", nr, element, start > 0 ? "... " : "");
+	for (i = start; i < end; i++)
+		pr_cont("%x ", *(u8 *)(element + i));
+	pr_cont("%s\n", end < size ? "..." : "");
+	dump_stack();
+}
+
+static void __check_element(struct mempool *pool, void *element, size_t size)
+{
+	u8 *obj = element;
+	size_t i;
+
+	for (i = 0; i < size; i++) {
+		u8 exp = (i < size - 1) ? POISON_FREE : POISON_END;
+
+		if (obj[i] != exp) {
+			poison_error(pool, element, size, i);
+			return;
+		}
+	}
+	memset(obj, POISON_INUSE, size);
+}
+
+static void check_element(struct mempool *pool, void *element)
+{
+	/* Skip checking: KASAN might save its metadata in the element. */
+	if (kasan_enabled())
+		return;
+
+	/* Mempools backed by slab allocator */
+	if (pool->free == mempool_kfree) {
+		__check_element(pool, element, (size_t)pool->pool_data);
+	} else if (pool->free == mempool_free_slab) {
+		__check_element(pool, element, kmem_cache_size(pool->pool_data));
+	} else if (pool->free == mempool_free_pages) {
+		/* Mempools backed by page allocator */
+		int order = (int)(long)pool->pool_data;
+
+#ifdef CONFIG_HIGHMEM
+		for (int i = 0; i < (1 << order); i++) {
+			struct page *page = (struct page *)element;
+			void *addr = kmap_local_page(page + i);
+
+			__check_element(pool, addr, PAGE_SIZE);
+			kunmap_local(addr);
+		}
+#else
+		void *addr = page_address((struct page *)element);
+
+		__check_element(pool, addr, PAGE_SIZE << order);
+#endif
+	}
+}
+
+static void __poison_element(void *element, size_t size)
+{
+	u8 *obj = element;
+
+	memset(obj, POISON_FREE, size - 1);
+	obj[size - 1] = POISON_END;
+}
+
+static void poison_element(struct mempool *pool, void *element)
+{
+	/* Skip poisoning: KASAN might save its metadata in the element. */
+	if (kasan_enabled())
+		return;
+
+	/* Mempools backed by slab allocator */
+	if (pool->alloc == mempool_kmalloc) {
+		__poison_element(element, (size_t)pool->pool_data);
+	} else if (pool->alloc == mempool_alloc_slab) {
+		__poison_element(element, kmem_cache_size(pool->pool_data));
+	} else if (pool->alloc == mempool_alloc_pages) {
+		/* Mempools backed by page allocator */
+		int order = (int)(long)pool->pool_data;
+
+#ifdef CONFIG_HIGHMEM
+		for (int i = 0; i < (1 << order); i++) {
+			struct page *page = (struct page *)element;
+			void *addr = kmap_local_page(page + i);
+
+			__poison_element(addr, PAGE_SIZE);
+			kunmap_local(addr);
+		}
+#else
+		void *addr = page_address((struct page *)element);
+
+		__poison_element(addr, PAGE_SIZE << order);
+#endif
+	}
+}
+#else /* CONFIG_SLUB_DEBUG_ON */
+static inline void check_element(struct mempool *pool, void *element)
+{
+}
+static inline void poison_element(struct mempool *pool, void *element)
+{
+}
+#endif /* CONFIG_SLUB_DEBUG_ON */
+
+static __always_inline bool kasan_poison_element(struct mempool *pool,
+		void *element)
+{
+	if (pool->alloc == mempool_alloc_slab || pool->alloc == mempool_kmalloc)
+		return kasan_mempool_poison_object(element);
+	else if (pool->alloc == mempool_alloc_pages)
+		return kasan_mempool_poison_pages(element,
+						(unsigned long)pool->pool_data);
+	return true;
+}
+
+static void kasan_unpoison_element(struct mempool *pool, void *element)
+{
+	if (pool->alloc == mempool_kmalloc)
+		kasan_mempool_unpoison_object(element, (size_t)pool->pool_data);
+	else if (pool->alloc == mempool_alloc_slab)
+		kasan_mempool_unpoison_object(element,
+					      kmem_cache_size(pool->pool_data));
+	else if (pool->alloc == mempool_alloc_pages)
+		kasan_mempool_unpoison_pages(element,
+					     (unsigned long)pool->pool_data);
+}
+
+static __always_inline void add_element(struct mempool *pool, void *element)
+{
+	BUG_ON(pool->min_nr != 0 && pool->curr_nr >= pool->min_nr);
+	poison_element(pool, element);
+	if (kasan_poison_element(pool, element))
+		pool->elements[pool->curr_nr++] = element;
+}
+
+static void *remove_element(struct mempool *pool)
+{
+	void *element = pool->elements[--pool->curr_nr];
+
+	BUG_ON(pool->curr_nr < 0);
+	kasan_unpoison_element(pool, element);
+	check_element(pool, element);
+	return element;
+}
+
+/**
+ * mempool_exit - exit a mempool initialized with mempool_init()
+ * @pool:      pointer to the memory pool which was initialized with
+ *             mempool_init().
+ *
+ * Free all reserved elements in @pool and @pool itself.  This function
+ * only sleeps if the free_fn() function sleeps.
+ *
+ * May be called on a zeroed but uninitialized mempool (i.e. allocated with
+ * kzalloc()).
+ */
+void mempool_exit(struct mempool *pool)
+{
+	while (pool->curr_nr) {
+		void *element = remove_element(pool);
+		pool->free(element, pool->pool_data);
+	}
+	kfree(pool->elements);
+	pool->elements = NULL;
+}
+EXPORT_SYMBOL(mempool_exit);
+
+/**
+ * mempool_destroy - deallocate a memory pool
+ * @pool:      pointer to the memory pool which was allocated via
+ *             mempool_create().
+ *
+ * Free all reserved elements in @pool and @pool itself.  This function
+ * only sleeps if the free_fn() function sleeps.
+ */
+void mempool_destroy(struct mempool *pool)
+{
+	if (unlikely(!pool))
+		return;
+
+	mempool_exit(pool);
+	kfree(pool);
+}
+EXPORT_SYMBOL(mempool_destroy);
+
+int mempool_init_node(struct mempool *pool, int min_nr,
+		mempool_alloc_t *alloc_fn, mempool_free_t *free_fn,
+		void *pool_data, gfp_t gfp_mask, int node_id)
+{
+	spin_lock_init(&pool->lock);
+	pool->min_nr	= min_nr;
+	pool->pool_data = pool_data;
+	pool->alloc	= alloc_fn;
+	pool->free	= free_fn;
+	init_waitqueue_head(&pool->wait);
+	/*
+	 * max() used here to ensure storage for at least 1 element to support
+	 * zero minimum pool
+	 */
+	pool->elements = kmalloc_array_node(max(1, min_nr), sizeof(void *),
+					    gfp_mask, node_id);
+	if (!pool->elements)
+		return -ENOMEM;
+
+	/*
+	 * First pre-allocate the guaranteed number of buffers,
+	 * also pre-allocate 1 element for zero minimum pool.
+	 */
+	while (pool->curr_nr < max(1, pool->min_nr)) {
+		void *element;
+
+		element = pool->alloc(gfp_mask, pool->pool_data);
+		if (unlikely(!element)) {
+			mempool_exit(pool);
+			return -ENOMEM;
+		}
+		add_element(pool, element);
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL(mempool_init_node);
+
+/**
+ * mempool_init - initialize a memory pool
+ * @pool:      pointer to the memory pool that should be initialized
+ * @min_nr:    the minimum number of elements guaranteed to be
+ *             allocated for this pool.
+ * @alloc_fn:  user-defined element-allocation function.
+ * @free_fn:   user-defined element-freeing function.
+ * @pool_data: optional private data available to the user-defined functions.
+ *
+ * Like mempool_create(), but initializes the pool in (i.e. embedded in another
+ * structure).
+ *
+ * Return: %0 on success, negative error code otherwise.
+ */
+int mempool_init_noprof(struct mempool *pool, int min_nr,
+		mempool_alloc_t *alloc_fn, mempool_free_t *free_fn,
+		void *pool_data)
+{
+	return mempool_init_node(pool, min_nr, alloc_fn, free_fn,
+				 pool_data, GFP_KERNEL, NUMA_NO_NODE);
+
+}
+EXPORT_SYMBOL(mempool_init_noprof);
+
+/**
+ * mempool_create_node - create a memory pool
+ * @min_nr:    the minimum number of elements guaranteed to be
+ *             allocated for this pool.
+ * @alloc_fn:  user-defined element-allocation function.
+ * @free_fn:   user-defined element-freeing function.
+ * @pool_data: optional private data available to the user-defined functions.
+ * @gfp_mask:  memory allocation flags
+ * @node_id:   numa node to allocate on
+ *
+ * this function creates and allocates a guaranteed size, preallocated
+ * memory pool. The pool can be used from the mempool_alloc() and mempool_free()
+ * functions. This function might sleep. Both the alloc_fn() and the free_fn()
+ * functions might sleep - as long as the mempool_alloc() function is not called
+ * from IRQ contexts.
+ *
+ * Return: pointer to the created memory pool object or %NULL on error.
+ */
+struct mempool *mempool_create_node_noprof(int min_nr,
+		mempool_alloc_t *alloc_fn, mempool_free_t *free_fn,
+		void *pool_data, gfp_t gfp_mask, int node_id)
+{
+	struct mempool *pool;
+
+	pool = kmalloc_node_noprof(sizeof(*pool), gfp_mask | __GFP_ZERO, node_id);
+	if (!pool)
+		return NULL;
+
+	if (mempool_init_node(pool, min_nr, alloc_fn, free_fn, pool_data,
+			      gfp_mask, node_id)) {
+		kfree(pool);
+		return NULL;
+	}
+
+	return pool;
+}
+EXPORT_SYMBOL(mempool_create_node_noprof);
+
+/**
+ * mempool_resize - resize an existing memory pool
+ * @pool:       pointer to the memory pool which was allocated via
+ *              mempool_create().
+ * @new_min_nr: the new minimum number of elements guaranteed to be
+ *              allocated for this pool.
+ *
+ * This function shrinks/grows the pool. In the case of growing,
+ * it cannot be guaranteed that the pool will be grown to the new
+ * size immediately, but new mempool_free() calls will refill it.
+ * This function may sleep.
+ *
+ * Note, the caller must guarantee that no mempool_destroy is called
+ * while this function is running. mempool_alloc() & mempool_free()
+ * might be called (eg. from IRQ contexts) while this function executes.
+ *
+ * Return: %0 on success, negative error code otherwise.
+ */
+int mempool_resize(struct mempool *pool, int new_min_nr)
+{
+	void *element;
+	void **new_elements;
+	unsigned long flags;
+
+	BUG_ON(new_min_nr <= 0);
+	might_sleep();
+
+	spin_lock_irqsave(&pool->lock, flags);
+	if (new_min_nr <= pool->min_nr) {
+		while (new_min_nr < pool->curr_nr) {
+			element = remove_element(pool);
+			spin_unlock_irqrestore(&pool->lock, flags);
+			pool->free(element, pool->pool_data);
+			spin_lock_irqsave(&pool->lock, flags);
+		}
+		pool->min_nr = new_min_nr;
+		goto out_unlock;
+	}
+	spin_unlock_irqrestore(&pool->lock, flags);
+
+	/* Grow the pool */
+	new_elements = kmalloc_objs(*new_elements, new_min_nr);
+	if (!new_elements)
+		return -ENOMEM;
+
+	spin_lock_irqsave(&pool->lock, flags);
+	if (unlikely(new_min_nr <= pool->min_nr)) {
+		/* Raced, other resize will do our work */
+		spin_unlock_irqrestore(&pool->lock, flags);
+		kfree(new_elements);
+		goto out;
+	}
+	memcpy(new_elements, pool->elements,
+			pool->curr_nr * sizeof(*new_elements));
+	kfree(pool->elements);
+	pool->elements = new_elements;
+	pool->min_nr = new_min_nr;
+
+	while (pool->curr_nr < pool->min_nr) {
+		spin_unlock_irqrestore(&pool->lock, flags);
+		element = pool->alloc(GFP_KERNEL, pool->pool_data);
+		if (!element)
+			goto out;
+		spin_lock_irqsave(&pool->lock, flags);
+		if (pool->curr_nr < pool->min_nr) {
+			add_element(pool, element);
+		} else {
+			spin_unlock_irqrestore(&pool->lock, flags);
+			pool->free(element, pool->pool_data);	/* Raced */
+			goto out;
+		}
+	}
+out_unlock:
+	spin_unlock_irqrestore(&pool->lock, flags);
+out:
+	return 0;
+}
+EXPORT_SYMBOL(mempool_resize);
+
+static unsigned int mempool_alloc_from_pool(struct mempool *pool, void **elems,
+		unsigned int count, unsigned int allocated,
+		gfp_t gfp_mask)
+{
+	unsigned long flags;
+	unsigned int i;
+
+	spin_lock_irqsave(&pool->lock, flags);
+	if (unlikely(pool->curr_nr < count - allocated))
+		goto fail;
+	while (allocated < count)
+		elems[allocated++] = remove_element(pool);
+	spin_unlock_irqrestore(&pool->lock, flags);
+
+	/* Paired with rmb in mempool_free(), read comment there. */
+	smp_wmb();
+
+	/*
+	 * Update the allocation stack trace as this is more useful for
+	 * debugging.
+	 */
+	for (i = 0; i < count; i++)
+		kmemleak_update_trace(elems[i]);
+	return allocated;
+
+fail:
+	if (gfp_mask & __GFP_DIRECT_RECLAIM) {
+		DEFINE_WAIT(wait);
+
+		prepare_to_wait(&pool->wait, &wait, TASK_UNINTERRUPTIBLE);
+		spin_unlock_irqrestore(&pool->lock, flags);
+
+		/*
+		 * Wait for someone else to return an element to @pool, but wake
+		 * up occasionally as memory pressure might have reduced even
+		 * and the normal allocation in alloc_fn could succeed even if
+		 * no element was returned.
+		 */
+		io_schedule_timeout(5 * HZ);
+		finish_wait(&pool->wait, &wait);
+	} else {
+		/* We must not sleep if __GFP_DIRECT_RECLAIM is not set. */
+		spin_unlock_irqrestore(&pool->lock, flags);
+	}
+
+	return allocated;
+}
+
+/*
+ * Adjust the gfp flags for mempool allocations, as we never want to dip into
+ * the global emergency reserves or retry in the page allocator.
+ *
+ * The first pass also doesn't want to go reclaim, but the next passes do, so
+ * return a separate subset for that first iteration.
+ */
+static inline gfp_t mempool_adjust_gfp(gfp_t *gfp_mask)
+{
+	*gfp_mask |= __GFP_NOMEMALLOC | __GFP_NORETRY | __GFP_NOWARN;
+	return *gfp_mask & ~(__GFP_DIRECT_RECLAIM | __GFP_IO);
+}
+
+/**
+ * mempool_alloc_bulk - allocate multiple elements from a memory pool
+ * @pool:	pointer to the memory pool
+ * @elems:	partially or fully populated elements array
+ * @count:	number of entries in @elem that need to be allocated
+ *
+ * Allocate @count elements into @elems.  This is done by first calling into the
+ * alloc_fn supplied at pool initialization time, and dipping into the reserved
+ * pool when alloc_fn fails to allocate an element.
+ *
+ * On return all @count elements in @elems will be populated.
+ *
+ * Return: Always 0.  If it wasn't for %$#^$ alloc tags, it would return void.
+ */
+int mempool_alloc_bulk_noprof(struct mempool *pool, void **elems,
+		unsigned int count)
+{
+	gfp_t gfp_mask = GFP_KERNEL;
+	gfp_t gfp_temp = mempool_adjust_gfp(&gfp_mask);
+	unsigned int allocated = 0;
+
+	VM_WARN_ON_ONCE(count > pool->min_nr);
+	might_alloc(gfp_mask);
+
+	/*
+	 * If an error is injected, fail all elements in a bulk allocation so
+	 * that we stress the multiple elements missing path.
+	 */
+	if (should_fail_ex(&fail_mempool_alloc_bulk, 1, FAULT_NOWARN)) {
+		pr_info("forcing mempool usage for %pS\n",
+				(void *)_RET_IP_);
+		goto use_pool;
+	}
+
+repeat_alloc:
+	/*
+	 * Try to allocate the elements using the allocation callback first as
+	 * that might succeed even when the caller's bulk allocation did not.
+	 */
+	while (allocated < count) {
+		elems[allocated] = pool->alloc(gfp_temp, pool->pool_data);
+		if (unlikely(!elems[allocated]))
+			goto use_pool;
+		allocated++;
+	}
+
+	return 0;
+
+use_pool:
+	allocated = mempool_alloc_from_pool(pool, elems, count, allocated,
+			gfp_temp);
+	gfp_temp = gfp_mask;
+	goto repeat_alloc;
+}
+EXPORT_SYMBOL_GPL(mempool_alloc_bulk_noprof);
+
+/**
+ * mempool_alloc - allocate an element from a memory pool
+ * @pool:	pointer to the memory pool
+ * @gfp_mask:	GFP_* flags.  %__GFP_ZERO is not supported.
+ *
+ * Allocate an element from @pool.  This is done by first calling into the
+ * alloc_fn supplied at pool initialization time, and dipping into the reserved
+ * pool when alloc_fn fails to allocate an element.
+ *
+ * This function only sleeps if the alloc_fn callback sleeps, or when waiting
+ * for elements to become available in the pool.
+ *
+ * Return: pointer to the allocated element or %NULL when failing to allocate
+ * an element.  Allocation failure can only happen when @gfp_mask does not
+ * include %__GFP_DIRECT_RECLAIM.
+ */
+void *mempool_alloc_noprof(struct mempool *pool, gfp_t gfp_mask)
+{
+	gfp_t gfp_temp = mempool_adjust_gfp(&gfp_mask);
+	void *element;
+
+	VM_WARN_ON_ONCE(gfp_mask & __GFP_ZERO);
+	might_alloc(gfp_mask);
+
+repeat_alloc:
+	if (should_fail_ex(&fail_mempool_alloc, 1, FAULT_NOWARN)) {
+		pr_info("forcing mempool usage for %pS\n",
+				(void *)_RET_IP_);
+		element = NULL;
+	} else {
+		element = pool->alloc(gfp_temp, pool->pool_data);
+	}
+
+	if (unlikely(!element)) {
+		/*
+		 * Try to allocate an element from the pool.
+		 *
+		 * The first pass won't have __GFP_DIRECT_RECLAIM and won't
+		 * sleep in mempool_alloc_from_pool.  Retry the allocation
+		 * with all flags set in that case.
+		 */
+		if (!mempool_alloc_from_pool(pool, &element, 1, 0, gfp_temp)) {
+			if (gfp_temp != gfp_mask) {
+				gfp_temp = gfp_mask;
+				goto repeat_alloc;
+			}
+			if (gfp_mask & __GFP_DIRECT_RECLAIM) {
+				goto repeat_alloc;
+			}
+		}
+	}
+
+	return element;
+}
+EXPORT_SYMBOL(mempool_alloc_noprof);
+
+/**
+ * mempool_alloc_preallocated - allocate an element from preallocated elements
+ *                              belonging to a memory pool
+ * @pool:	pointer to the memory pool
+ *
+ * This function is similar to mempool_alloc(), but it only attempts allocating
+ * an element from the preallocated elements. It only takes a single spinlock_t
+ * and immediately returns if no preallocated elements are available.
+ *
+ * Return: pointer to the allocated element or %NULL if no elements are
+ * available.
+ */
+void *mempool_alloc_preallocated(struct mempool *pool)
+{
+	void *element = NULL;
+
+	mempool_alloc_from_pool(pool, &element, 1, 0, GFP_NOWAIT);
+	return element;
+}
+EXPORT_SYMBOL(mempool_alloc_preallocated);
+
+/**
+ * mempool_free_bulk - return elements to a mempool
+ * @pool:	pointer to the memory pool
+ * @elems:	elements to return
+ * @count:	number of elements to return
+ *
+ * Returns a number of elements from the start of @elem to @pool if @pool needs
+ * replenishing and sets their slots in @elem to NULL.  Other elements are left
+ * in @elem.
+ *
+ * Return: number of elements transferred to @pool.  Elements are always
+ * transferred from the beginning of @elem, so the return value can be used as
+ * an offset into @elem for the freeing the remaining elements in the caller.
+ */
+unsigned int mempool_free_bulk(struct mempool *pool, void **elems,
+		unsigned int count)
+{
+	unsigned long flags;
+	unsigned int freed = 0;
+	bool added = false;
+
+	/*
+	 * Paired with the wmb in mempool_alloc().  The preceding read is
+	 * for @element and the following @pool->curr_nr.  This ensures
+	 * that the visible value of @pool->curr_nr is from after the
+	 * allocation of @element.  This is necessary for fringe cases
+	 * where @element was passed to this task without going through
+	 * barriers.
+	 *
+	 * For example, assume @p is %NULL at the beginning and one task
+	 * performs "p = mempool_alloc(...);" while another task is doing
+	 * "while (!p) cpu_relax(); mempool_free(p, ...);".  This function
+	 * may end up using curr_nr value which is from before allocation
+	 * of @p without the following rmb.
+	 */
+	smp_rmb();
+
+	/*
+	 * For correctness, we need a test which is guaranteed to trigger
+	 * if curr_nr + #allocated == min_nr.  Testing curr_nr < min_nr
+	 * without locking achieves that and refilling as soon as possible
+	 * is desirable.
+	 *
+	 * Because curr_nr visible here is always a value after the
+	 * allocation of @element, any task which decremented curr_nr below
+	 * min_nr is guaranteed to see curr_nr < min_nr unless curr_nr gets
+	 * incremented to min_nr afterwards.  If curr_nr gets incremented
+	 * to min_nr after the allocation of @element, the elements
+	 * allocated after that are subject to the same guarantee.
+	 *
+	 * Waiters happen iff curr_nr is 0 and the above guarantee also
+	 * ensures that there will be frees which return elements to the
+	 * pool waking up the waiters.
+	 *
+	 * For zero-minimum pools, curr_nr < min_nr (0 < 0) never succeeds,
+	 * so waiters sleeping on pool->wait would never be woken by the
+	 * wake-up path of previous test. This explicit check ensures the
+	 * allocation of element when both min_nr and curr_nr are 0, and
+	 * any active waiters are properly awakened.
+	 */
+	if (unlikely(READ_ONCE(pool->curr_nr) < pool->min_nr)) {
+		spin_lock_irqsave(&pool->lock, flags);
+		while (pool->curr_nr < pool->min_nr && freed < count) {
+			add_element(pool, elems[freed++]);
+			added = true;
+		}
+		spin_unlock_irqrestore(&pool->lock, flags);
+	} else if (unlikely(pool->min_nr == 0 &&
+		     READ_ONCE(pool->curr_nr) == 0)) {
+		/* Handle the min_nr = 0 edge case: */
+		spin_lock_irqsave(&pool->lock, flags);
+		if (likely(pool->curr_nr == 0)) {
+			add_element(pool, elems[freed++]);
+			added = true;
+		}
+		spin_unlock_irqrestore(&pool->lock, flags);
+	}
+
+	if (unlikely(added) && wq_has_sleeper(&pool->wait))
+		wake_up(&pool->wait);
+
+	return freed;
+}
+EXPORT_SYMBOL_GPL(mempool_free_bulk);
+
+/**
+ * mempool_free - return an element to the pool.
+ * @element:	element to return
+ * @pool:	pointer to the memory pool
+ *
+ * Returns @element to @pool if it needs replenishing, else frees it using
+ * the free_fn callback in @pool.
+ *
+ * This function only sleeps if the free_fn callback sleeps.
+ */
+void mempool_free(void *element, struct mempool *pool)
+{
+	if (likely(element) && !mempool_free_bulk(pool, &element, 1))
+		pool->free(element, pool->pool_data);
+}
+EXPORT_SYMBOL(mempool_free);
+
+/*
+ * A commonly used alloc and free fn.
+ */
+void *mempool_alloc_slab(gfp_t gfp_mask, void *pool_data)
+{
+	struct kmem_cache *mem = pool_data;
+	VM_BUG_ON(mem->ctor);
+	return kmem_cache_alloc_noprof(mem, gfp_mask);
+}
+EXPORT_SYMBOL(mempool_alloc_slab);
+
+void mempool_free_slab(void *element, void *pool_data)
+{
+	struct kmem_cache *mem = pool_data;
+	kmem_cache_free(mem, element);
+}
+EXPORT_SYMBOL(mempool_free_slab);
+
+/*
+ * A commonly used alloc and free fn that kmalloc/kfrees the amount of memory
+ * specified by pool_data
+ */
+void *mempool_kmalloc(gfp_t gfp_mask, void *pool_data)
+{
+	size_t size = (size_t)pool_data;
+	return kmalloc_noprof(size, gfp_mask);
+}
+EXPORT_SYMBOL(mempool_kmalloc);
+
+void mempool_kfree(void *element, void *pool_data)
+{
+	kfree(element);
+}
+EXPORT_SYMBOL(mempool_kfree);
+
+/*
+ * A simple mempool-backed page allocator that allocates pages
+ * of the order specified by pool_data.
+ */
+void *mempool_alloc_pages(gfp_t gfp_mask, void *pool_data)
+{
+	int order = (int)(long)pool_data;
+	return alloc_pages_noprof(gfp_mask, order);
+}
+EXPORT_SYMBOL(mempool_alloc_pages);
+
+void mempool_free_pages(void *element, void *pool_data)
+{
+	int order = (int)(long)pool_data;
+	__free_pages(element, order);
+}
+EXPORT_SYMBOL(mempool_free_pages);