// 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/blkdev.h>#include <linux/writeback.h>#include "slab.h" #if defined(CONFIG_DEBUG_SLAB) || defined(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){	/* Mempools backed by slab allocator */	if (pool->free == mempool_free_slab || pool->free == mempool_kfree)		__check_element(pool, element, ksize(element)); 	/* Mempools backed by page allocator */	if (pool->free == mempool_free_pages) {		int order = (int)(long)pool->pool_data;		void *addr = kmap_atomic((struct page *)element); 		__check_element(pool, addr, 1UL << (PAGE_SHIFT + order));		kunmap_atomic(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){	/* Mempools backed by slab allocator */	if (pool->alloc == mempool_alloc_slab || pool->alloc == mempool_kmalloc)		__poison_element(element, ksize(element)); 	/* Mempools backed by page allocator */	if (pool->alloc == mempool_alloc_pages) {		int order = (int)(long)pool->pool_data;		void *addr = kmap_atomic((struct page *)element); 		__poison_element(addr, 1UL << (PAGE_SHIFT + order));		kunmap_atomic(addr);	}}#else /* CONFIG_DEBUG_SLAB || 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_DEBUG_SLAB || CONFIG_SLUB_DEBUG_ON */ static __always_inline void kasan_poison_element(mempool_t *pool, void *element){	if (pool->alloc == mempool_alloc_slab || pool->alloc == mempool_kmalloc)		kasan_poison_kfree(element, _RET_IP_);	if (pool->alloc == mempool_alloc_pages)		kasan_free_pages(element, (unsigned long)pool->pool_data);} static void kasan_unpoison_element(mempool_t *pool, void *element){	if (pool->alloc == mempool_alloc_slab || pool->alloc == mempool_kmalloc)		kasan_unpoison_slab(element);	if (pool->alloc == mempool_alloc_pages)		kasan_alloc_pages(element, (unsigned long)pool->pool_data);} static __always_inline void add_element(mempool_t *pool, void *element){	BUG_ON(pool->curr_nr >= pool->min_nr);	poison_element(pool, element);	kasan_poison_element(pool, element);	pool->elements[pool->curr_nr++] = element;} static void *remove_element(mempool_t *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(mempool_t *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(mempool_t *pool){	if (unlikely(!pool))		return; 	mempool_exit(pool);	kfree(pool);}EXPORT_SYMBOL(mempool_destroy); 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){	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); 	pool->elements = kmalloc_array_node(min_nr, sizeof(void *),					    gfp_mask, node_id);	if (!pool->elements)		return -ENOMEM; 	/*	 * First pre-allocate the guaranteed number of buffers.	 */	while (pool->curr_nr < 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(mempool_t *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); /** * mempool_create - 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. * * 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(int min_nr, mempool_alloc_t *alloc_fn,				mempool_free_t *free_fn, void *pool_data){	return mempool_create_node(min_nr,alloc_fn,free_fn, pool_data,				   GFP_KERNEL, NUMA_NO_NODE);}EXPORT_SYMBOL(mempool_create); mempool_t *mempool_create_node(int min_nr, mempool_alloc_t *alloc_fn,			       mempool_free_t *free_fn, void *pool_data,			       gfp_t gfp_mask, int node_id){	mempool_t *pool; 	pool = kzalloc_node(sizeof(*pool), gfp_mask, 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); /** * 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){	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_array(new_min_nr, sizeof(*new_elements),				     GFP_KERNEL);	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); /** * 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(mempool_t *pool, gfp_t gfp_mask){	void *element;	unsigned long flags;	wait_queue_entry_t wait;	gfp_t gfp_temp; 	VM_WARN_ON_ONCE(gfp_mask & __GFP_ZERO);	might_sleep_if(gfp_mask & __GFP_DIRECT_RECLAIM); 	gfp_mask |= __GFP_NOMEMALLOC;	/* don't allocate emergency reserves */	gfp_mask |= __GFP_NORETRY;	/* don't loop in __alloc_pages */	gfp_mask |= __GFP_NOWARN;	/* failures are OK */ 	gfp_temp = gfp_mask & ~(__GFP_DIRECT_RECLAIM|__GFP_IO); repeat_alloc: 	element = pool->alloc(gfp_temp, pool->pool_data);	if (likely(element != NULL))		return element; 	spin_lock_irqsave(&pool->lock, flags);	if (likely(pool->curr_nr)) {		element = 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.		 */		kmemleak_update_trace(element);		return element;	} 	/*	 * We use gfp mask w/o direct reclaim or IO for the first round.  If	 * alloc failed with that and @pool was empty, retry immediately.	 */	if (gfp_temp != gfp_mask) {		spin_unlock_irqrestore(&pool->lock, flags);		gfp_temp = gfp_mask;		goto repeat_alloc;	} 	/* We must not sleep if !__GFP_DIRECT_RECLAIM */	if (!(gfp_mask & __GFP_DIRECT_RECLAIM)) {		spin_unlock_irqrestore(&pool->lock, flags);		return NULL;	} 	/* Let's wait for someone else to return an element to @pool */	init_wait(&wait);	prepare_to_wait(&pool->wait, &wait, TASK_UNINTERRUPTIBLE); 	spin_unlock_irqrestore(&pool->lock, flags); 	/*	 * FIXME: this should be io_schedule().  The timeout is there as a	 * workaround for some DM problems in 2.6.18.	 */	io_schedule_timeout(5*HZ); 	finish_wait(&pool->wait, &wait);	goto repeat_alloc;}EXPORT_SYMBOL(mempool_alloc); /** * 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){	unsigned long flags; 	if (unlikely(element == NULL))		return; 	/*	 * 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.	 */	if (unlikely(READ_ONCE(pool->curr_nr) < pool->min_nr)) {		spin_lock_irqsave(&pool->lock, flags);		if (likely(pool->curr_nr < pool->min_nr)) {			add_element(pool, element);			spin_unlock_irqrestore(&pool->lock, flags);			wake_up(&pool->wait);			return;		}		spin_unlock_irqrestore(&pool->lock, flags);

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