linux/mm/mempool.c

// SPDX-License-Identifier: GPL-2.0
/*
 *  linux/mm/mempool.c
 *
 *  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/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"

#ifdef CONFIG_SLUB_DEBUG_ON
static void poison_error(mempool_t *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(mempool_t *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(mempool_t *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;
		void *addr = kmap_local_page((struct page *)element);

		__check_element(pool, addr, 1UL << (PAGE_SHIFT + order));
		kunmap_local(addr);
	}
}

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(mempool_t *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;
		void *addr = kmap_local_page((struct page *)element);

		__poison_element(addr, 1UL << (PAGE_SHIFT + order));
		kunmap_local(addr);
	}
}
#else /* CONFIG_SLUB_DEBUG_ON */
static inline void check_element(mempool_t *pool, void *element)
{ … }
static inline void poison_element(mempool_t *pool, void *element)
{ … }
#endif /* CONFIG_SLUB_DEBUG_ON */

static __always_inline bool kasan_poison_element(mempool_t *pool, void *element)
{ … }

static void kasan_unpoison_element(mempool_t *pool, void *element)
{ … }

static __always_inline void add_element(mempool_t *pool, void *element)
{ … }

static void *remove_element(mempool_t *pool)
{ … }

/**
 * 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(mempool_t *pool)
{ … }
EXPORT_SYMBOL(…);

/**
 * 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(mempool_t *pool)
{ … }
EXPORT_SYMBOL(…);

int mempool_init_node(mempool_t *pool, int min_nr, mempool_alloc_t *alloc_fn,
		      mempool_free_t *free_fn, void *pool_data,
		      gfp_t gfp_mask, int node_id)
{ … }
EXPORT_SYMBOL(…);

/**
 * 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(mempool_t *pool, int min_nr, mempool_alloc_t *alloc_fn,
			mempool_free_t *free_fn, void *pool_data)
{ … }
EXPORT_SYMBOL(…);

/**
 * 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.
 */
mempool_t *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)
{ … }
EXPORT_SYMBOL(…);

/**
 * 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(mempool_t *pool, int new_min_nr)
{ … }
EXPORT_SYMBOL(…);

/**
 * mempool_alloc - allocate an element from a specific memory pool
 * @pool:      pointer to the memory pool which was allocated via
 *             mempool_create().
 * @gfp_mask:  the usual allocation bitmask.
 *
 * this function only sleeps if the alloc_fn() function sleeps or
 * returns NULL. Note that due to preallocation, this function
 * *never* fails when called from process contexts. (it might
 * fail if called from an IRQ context.)
 * Note: using __GFP_ZERO is not supported.
 *
 * Return: pointer to the allocated element or %NULL on error.
 */
void *mempool_alloc_noprof(mempool_t *pool, gfp_t gfp_mask)
{ … }
EXPORT_SYMBOL(…);

/**
 * mempool_alloc_preallocated - allocate an element from preallocated elements
 *                              belonging to a specific memory pool
 * @pool:      pointer to the memory pool which was allocated via
 *             mempool_create().
 *
 * This function is similar to mempool_alloc, but it only attempts allocating
 * an element from the preallocated elements. It does not sleep 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(mempool_t *pool)
{ … }
EXPORT_SYMBOL(…);

/**
 * mempool_free - return an element to the pool.
 * @element:   pool element pointer.
 * @pool:      pointer to the memory pool which was allocated via
 *             mempool_create().
 *
 * this function only sleeps if the free_fn() function sleeps.
 */
void mempool_free(void *element, mempool_t *pool)
{ … }
EXPORT_SYMBOL(…);

/*
 * A commonly used alloc and free fn.
 */
void *mempool_alloc_slab(gfp_t gfp_mask, void *pool_data)
{ … }
EXPORT_SYMBOL(…);

void mempool_free_slab(void *element, void *pool_data)
{ … }
EXPORT_SYMBOL(…);

/*
 * 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)
{ … }
EXPORT_SYMBOL(…);

void mempool_kfree(void *element, void *pool_data)
{ … }
EXPORT_SYMBOL(…);

void *mempool_kvmalloc(gfp_t gfp_mask, void *pool_data)
{ … }
EXPORT_SYMBOL(…);

void mempool_kvfree(void *element, void *pool_data)
{ … }
EXPORT_SYMBOL(…);

/*
 * 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)
{ … }
EXPORT_SYMBOL(…);

void mempool_free_pages(void *element, void *pool_data)
{ … }
EXPORT_SYMBOL(…);