// 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" #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)); } else if (pool->free == mempool_free_pages) { /* Mempools backed by page allocator */ 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)); } else if (pool->alloc == mempool_alloc_pages) { /* Mempools backed by page allocator */ 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_slab_free_mempool(element); else if (pool->alloc == mempool_alloc_pages) kasan_poison_pages(element, (unsigned long)pool->pool_data, false); } static void kasan_unpoison_element(mempool_t *pool, void *element) { if (pool->alloc == mempool_alloc_slab || pool->alloc == mempool_kmalloc) kasan_unpoison_range(element, __ksize(element)); else if (pool->alloc == mempool_alloc_pages) kasan_unpoison_pages(element, (unsigned long)pool->pool_data, false); } 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_alloc(gfp_mask); 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); } 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(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(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(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);