/*
   *  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
  ");
  	pr_err("Mempool %p size %zu
  ", 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
  ", 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 void kasan_poison_element(mempool_t *pool, void *element)
  {
  	if (pool->alloc == mempool_alloc_slab)
  		kasan_slab_free(pool->pool_data, element);
  	if (pool->alloc == mempool_kmalloc)
  		kasan_kfree(element);
  	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, gfp_t flags)

  {
  	if (pool->alloc == mempool_alloc_slab)

  		kasan_slab_alloc(pool->pool_data, element, flags);

  	if (pool->alloc == mempool_kmalloc)

  		kasan_krealloc(element, (size_t)pool->pool_data, flags);

  	if (pool->alloc == mempool_alloc_pages)
  		kasan_alloc_pages(element, (unsigned long)pool->pool_data);
  }

  static 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, gfp_t flags)

  {

  	void *element = pool->elements[--pool->curr_nr];
  
  	BUG_ON(pool->curr_nr < 0);

  	kasan_unpoison_element(pool, element, flags);

  	check_element(pool, element);

  	return element;

  }

  /**
   * 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;

  	while (pool->curr_nr) {

  		void *element = remove_element(pool, GFP_KERNEL);

  		pool->free(element, pool->pool_data);
  	}
  	kfree(pool->elements);
  	kfree(pool);
  }

  EXPORT_SYMBOL(mempool_destroy);

  
  /**
   * 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.
   */

  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;

  	pool->elements = kmalloc_node(min_nr * sizeof(void *),

  				      gfp_mask, node_id);

  	if (!pool->elements) {
  		kfree(pool);
  		return NULL;
  	}
  	spin_lock_init(&pool->lock);
  	pool->min_nr = min_nr;
  	pool->pool_data = pool_data;
  	init_waitqueue_head(&pool->wait);
  	pool->alloc = alloc_fn;
  	pool->free = free_fn;
  
  	/*
  	 * 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_destroy(pool);

  			return NULL;
  		}
  		add_element(pool, element);
  	}
  	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.
   */

  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, GFP_KERNEL);

  			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: neither __GFP_NOMEMALLOC nor __GFP_ZERO are supported.

   */

  void *mempool_alloc(mempool_t *pool, gfp_t gfp_mask)

  {
  	void *element;
  	unsigned long flags;

  	wait_queue_t wait;

  	gfp_t gfp_temp;

  	/* If oom killed, memory reserves are essential to prevent livelock */
  	VM_WARN_ON_ONCE(gfp_mask & __GFP_NOMEMALLOC);
  	/* No element size to zero on allocation */

  	VM_WARN_ON_ONCE(gfp_mask & __GFP_ZERO);

  	might_sleep_if(gfp_mask & __GFP_DIRECT_RECLAIM);

  	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:

  	if (likely(pool->curr_nr)) {
  		/*
  		 * Don't allocate from emergency reserves if there are
  		 * elements available.  This check is racy, but it will
  		 * be rechecked each loop.
  		 */
  		gfp_temp |= __GFP_NOMEMALLOC;
  	}

  
  	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, gfp_temp);

  		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_NOMEMALLOC) != gfp_mask) {

  		spin_unlock_irqrestore(&pool->lock, flags);
  		gfp_temp = gfp_mask;
  		goto repeat_alloc;
  	}

  	gfp_temp = gfp_mask;

  	/* 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(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);