// SPDX-License-Identifier: BSD-3-Clause OR GPL-2.0
  /* Copyright (c) 2018 Mellanox Technologies. All rights reserved */
  
  #include <linux/module.h>
  #include <linux/slab.h>
  #include <linux/rhashtable.h>

  #include <linux/idr.h>

  #include <linux/list.h>
  #include <linux/sort.h>
  #include <linux/objagg.h>
  
  #define CREATE_TRACE_POINTS
  #include <trace/events/objagg.h>

  struct objagg_hints {
  	struct rhashtable node_ht;
  	struct rhashtable_params ht_params;
  	struct list_head node_list;
  	unsigned int node_count;
  	unsigned int root_count;
  	unsigned int refcount;
  	const struct objagg_ops *ops;
  };
  
  struct objagg_hints_node {
  	struct rhash_head ht_node; /* member of objagg_hints->node_ht */
  	struct list_head list; /* member of objagg_hints->node_list */
  	struct objagg_hints_node *parent;
  	unsigned int root_id;
  	struct objagg_obj_stats_info stats_info;
  	unsigned long obj[0];
  };
  
  static struct objagg_hints_node *
  objagg_hints_lookup(struct objagg_hints *objagg_hints, void *obj)
  {
  	if (!objagg_hints)
  		return NULL;
  	return rhashtable_lookup_fast(&objagg_hints->node_ht, obj,
  				      objagg_hints->ht_params);
  }

  struct objagg {
  	const struct objagg_ops *ops;
  	void *priv;
  	struct rhashtable obj_ht;
  	struct rhashtable_params ht_params;
  	struct list_head obj_list;
  	unsigned int obj_count;

  	struct ida root_ida;
  	struct objagg_hints *hints;

  };
  
  struct objagg_obj {
  	struct rhash_head ht_node; /* member of objagg->obj_ht */
  	struct list_head list; /* member of objagg->obj_list */
  	struct objagg_obj *parent; /* if the object is nested, this
  				    * holds pointer to parent, otherwise NULL
  				    */
  	union {
  		void *delta_priv; /* user delta private */
  		void *root_priv; /* user root private */
  	};

  	unsigned int root_id;

  	unsigned int refcount; /* counts number of users of this object
  				* including nested objects
  				*/
  	struct objagg_obj_stats stats;
  	unsigned long obj[0];
  };
  
  static unsigned int objagg_obj_ref_inc(struct objagg_obj *objagg_obj)
  {
  	return ++objagg_obj->refcount;
  }
  
  static unsigned int objagg_obj_ref_dec(struct objagg_obj *objagg_obj)
  {
  	return --objagg_obj->refcount;
  }
  
  static void objagg_obj_stats_inc(struct objagg_obj *objagg_obj)
  {
  	objagg_obj->stats.user_count++;
  	objagg_obj->stats.delta_user_count++;
  	if (objagg_obj->parent)
  		objagg_obj->parent->stats.delta_user_count++;
  }
  
  static void objagg_obj_stats_dec(struct objagg_obj *objagg_obj)
  {
  	objagg_obj->stats.user_count--;
  	objagg_obj->stats.delta_user_count--;
  	if (objagg_obj->parent)
  		objagg_obj->parent->stats.delta_user_count--;
  }
  
  static bool objagg_obj_is_root(const struct objagg_obj *objagg_obj)
  {
  	/* Nesting is not supported, so we can use ->parent
  	 * to figure out if the object is root.
  	 */
  	return !objagg_obj->parent;
  }
  
  /**
   * objagg_obj_root_priv - obtains root private for an object
   * @objagg_obj:	objagg object instance
   *
   * Note: all locking must be provided by the caller.
   *
   * Either the object is root itself when the private is returned
   * directly, or the parent is root and its private is returned
   * instead.
   *
   * Returns a user private root pointer.
   */
  const void *objagg_obj_root_priv(const struct objagg_obj *objagg_obj)
  {
  	if (objagg_obj_is_root(objagg_obj))
  		return objagg_obj->root_priv;
  	WARN_ON(!objagg_obj_is_root(objagg_obj->parent));
  	return objagg_obj->parent->root_priv;
  }
  EXPORT_SYMBOL(objagg_obj_root_priv);
  
  /**
   * objagg_obj_delta_priv - obtains delta private for an object
   * @objagg_obj:	objagg object instance
   *
   * Note: all locking must be provided by the caller.
   *
   * Returns user private delta pointer or NULL in case the passed
   * object is root.
   */
  const void *objagg_obj_delta_priv(const struct objagg_obj *objagg_obj)
  {
  	if (objagg_obj_is_root(objagg_obj))
  		return NULL;
  	return objagg_obj->delta_priv;
  }
  EXPORT_SYMBOL(objagg_obj_delta_priv);
  
  /**
   * objagg_obj_raw - obtains object user private pointer
   * @objagg_obj:	objagg object instance
   *
   * Note: all locking must be provided by the caller.
   *
   * Returns user private pointer as was passed to objagg_obj_get() by "obj" arg.
   */
  const void *objagg_obj_raw(const struct objagg_obj *objagg_obj)
  {
  	return objagg_obj->obj;
  }
  EXPORT_SYMBOL(objagg_obj_raw);
  
  static struct objagg_obj *objagg_obj_lookup(struct objagg *objagg, void *obj)
  {
  	return rhashtable_lookup_fast(&objagg->obj_ht, obj, objagg->ht_params);
  }
  
  static int objagg_obj_parent_assign(struct objagg *objagg,
  				    struct objagg_obj *objagg_obj,

  				    struct objagg_obj *parent,
  				    bool take_parent_ref)

  {
  	void *delta_priv;
  
  	delta_priv = objagg->ops->delta_create(objagg->priv, parent->obj,
  					       objagg_obj->obj);
  	if (IS_ERR(delta_priv))
  		return PTR_ERR(delta_priv);
  
  	/* User returned a delta private, that means that
  	 * our object can be aggregated into the parent.
  	 */
  	objagg_obj->parent = parent;
  	objagg_obj->delta_priv = delta_priv;

  	if (take_parent_ref)
  		objagg_obj_ref_inc(objagg_obj->parent);

  	trace_objagg_obj_parent_assign(objagg, objagg_obj,
  				       parent,
  				       parent->refcount);
  	return 0;
  }
  
  static int objagg_obj_parent_lookup_assign(struct objagg *objagg,
  					   struct objagg_obj *objagg_obj)
  {
  	struct objagg_obj *objagg_obj_cur;
  	int err;
  
  	list_for_each_entry(objagg_obj_cur, &objagg->obj_list, list) {
  		/* Nesting is not supported. In case the object
  		 * is not root, it cannot be assigned as parent.
  		 */
  		if (!objagg_obj_is_root(objagg_obj_cur))
  			continue;
  		err = objagg_obj_parent_assign(objagg, objagg_obj,

  					       objagg_obj_cur, true);

  		if (!err)
  			return 0;
  	}
  	return -ENOENT;
  }
  
  static void __objagg_obj_put(struct objagg *objagg,
  			     struct objagg_obj *objagg_obj);
  
  static void objagg_obj_parent_unassign(struct objagg *objagg,
  				       struct objagg_obj *objagg_obj)
  {
  	trace_objagg_obj_parent_unassign(objagg, objagg_obj,
  					 objagg_obj->parent,
  					 objagg_obj->parent->refcount);
  	objagg->ops->delta_destroy(objagg->priv, objagg_obj->delta_priv);
  	__objagg_obj_put(objagg, objagg_obj->parent);
  }

  static int objagg_obj_root_id_alloc(struct objagg *objagg,
  				    struct objagg_obj *objagg_obj,
  				    struct objagg_hints_node *hnode)
  {
  	unsigned int min, max;
  	int root_id;
  
  	/* In case there are no hints available, the root id is invalid. */
  	if (!objagg->hints) {
  		objagg_obj->root_id = OBJAGG_OBJ_ROOT_ID_INVALID;
  		return 0;
  	}
  
  	if (hnode) {
  		min = hnode->root_id;
  		max = hnode->root_id;
  	} else {
  		/* For objects with no hint, start after the last
  		 * hinted root_id.
  		 */
  		min = objagg->hints->root_count;
  		max = ~0;
  	}
  
  	root_id = ida_alloc_range(&objagg->root_ida, min, max, GFP_KERNEL);
  
  	if (root_id < 0)
  		return root_id;
  	objagg_obj->root_id = root_id;
  	return 0;
  }
  
  static void objagg_obj_root_id_free(struct objagg *objagg,
  				    struct objagg_obj *objagg_obj)
  {
  	if (!objagg->hints)
  		return;
  	ida_free(&objagg->root_ida, objagg_obj->root_id);
  }

  static int objagg_obj_root_create(struct objagg *objagg,

  				  struct objagg_obj *objagg_obj,
  				  struct objagg_hints_node *hnode)

  {

  	int err;

  	err = objagg_obj_root_id_alloc(objagg, objagg_obj, hnode);
  	if (err)
  		return err;
  	objagg_obj->root_priv = objagg->ops->root_create(objagg->priv,
  							 objagg_obj->obj,
  							 objagg_obj->root_id);
  	if (IS_ERR(objagg_obj->root_priv)) {
  		err = PTR_ERR(objagg_obj->root_priv);
  		goto err_root_create;
  	}

  	trace_objagg_obj_root_create(objagg, objagg_obj);
  	return 0;

  
  err_root_create:
  	objagg_obj_root_id_free(objagg, objagg_obj);
  	return err;

  }
  
  static void objagg_obj_root_destroy(struct objagg *objagg,
  				    struct objagg_obj *objagg_obj)
  {
  	trace_objagg_obj_root_destroy(objagg, objagg_obj);
  	objagg->ops->root_destroy(objagg->priv, objagg_obj->root_priv);

  	objagg_obj_root_id_free(objagg, objagg_obj);
  }
  
  static struct objagg_obj *__objagg_obj_get(struct objagg *objagg, void *obj);
  
  static int objagg_obj_init_with_hints(struct objagg *objagg,
  				      struct objagg_obj *objagg_obj,
  				      bool *hint_found)
  {
  	struct objagg_hints_node *hnode;
  	struct objagg_obj *parent;
  	int err;
  
  	hnode = objagg_hints_lookup(objagg->hints, objagg_obj->obj);
  	if (!hnode) {
  		*hint_found = false;
  		return 0;
  	}
  	*hint_found = true;
  
  	if (!hnode->parent)
  		return objagg_obj_root_create(objagg, objagg_obj, hnode);
  
  	parent = __objagg_obj_get(objagg, hnode->parent->obj);
  	if (IS_ERR(parent))
  		return PTR_ERR(parent);
  
  	err = objagg_obj_parent_assign(objagg, objagg_obj, parent, false);
  	if (err) {
  		*hint_found = false;
  		err = 0;
  		goto err_parent_assign;
  	}
  
  	return 0;
  
  err_parent_assign:
  	objagg_obj_put(objagg, parent);
  	return err;

  }
  
  static int objagg_obj_init(struct objagg *objagg,
  			   struct objagg_obj *objagg_obj)
  {

  	bool hint_found;

  	int err;

  	/* First, try to use hints if they are available and
  	 * if they provide result.
  	 */
  	err = objagg_obj_init_with_hints(objagg, objagg_obj, &hint_found);
  	if (err)
  		return err;
  
  	if (hint_found)
  		return 0;

  	/* Try to find if the object can be aggregated under an existing one. */
  	err = objagg_obj_parent_lookup_assign(objagg, objagg_obj);
  	if (!err)
  		return 0;
  	/* If aggregation is not possible, make the object a root. */

  	return objagg_obj_root_create(objagg, objagg_obj, NULL);

  }
  
  static void objagg_obj_fini(struct objagg *objagg,
  			    struct objagg_obj *objagg_obj)
  {
  	if (!objagg_obj_is_root(objagg_obj))
  		objagg_obj_parent_unassign(objagg, objagg_obj);
  	else
  		objagg_obj_root_destroy(objagg, objagg_obj);
  }
  
  static struct objagg_obj *objagg_obj_create(struct objagg *objagg, void *obj)
  {
  	struct objagg_obj *objagg_obj;
  	int err;
  
  	objagg_obj = kzalloc(sizeof(*objagg_obj) + objagg->ops->obj_size,
  			     GFP_KERNEL);
  	if (!objagg_obj)
  		return ERR_PTR(-ENOMEM);
  	objagg_obj_ref_inc(objagg_obj);
  	memcpy(objagg_obj->obj, obj, objagg->ops->obj_size);
  
  	err = objagg_obj_init(objagg, objagg_obj);
  	if (err)
  		goto err_obj_init;
  
  	err = rhashtable_insert_fast(&objagg->obj_ht, &objagg_obj->ht_node,
  				     objagg->ht_params);
  	if (err)
  		goto err_ht_insert;
  	list_add(&objagg_obj->list, &objagg->obj_list);
  	objagg->obj_count++;
  	trace_objagg_obj_create(objagg, objagg_obj);
  
  	return objagg_obj;
  
  err_ht_insert:
  	objagg_obj_fini(objagg, objagg_obj);
  err_obj_init:
  	kfree(objagg_obj);
  	return ERR_PTR(err);
  }
  
  static struct objagg_obj *__objagg_obj_get(struct objagg *objagg, void *obj)
  {
  	struct objagg_obj *objagg_obj;
  
  	/* First, try to find the object exactly as user passed it,
  	 * perhaps it is already in use.
  	 */
  	objagg_obj = objagg_obj_lookup(objagg, obj);
  	if (objagg_obj) {
  		objagg_obj_ref_inc(objagg_obj);
  		return objagg_obj;
  	}
  
  	return objagg_obj_create(objagg, obj);
  }
  
  /**
   * objagg_obj_get - gets an object within objagg instance
   * @objagg:	objagg instance
   * @obj:	user-specific private object pointer
   *
   * Note: all locking must be provided by the caller.
   *
   * Size of the "obj" memory is specified in "objagg->ops".
   *
   * There are 3 main options this function wraps:
   * 1) The object according to "obj" already exist. In that case
   *    the reference counter is incrementes and the object is returned.
   * 2) The object does not exist, but it can be aggregated within
   *    another object. In that case, user ops->delta_create() is called
   *    to obtain delta data and a new object is created with returned
   *    user-delta private pointer.
   * 3) The object does not exist and cannot be aggregated into
   *    any of the existing objects. In that case, user ops->root_create()
   *    is called to create the root and a new object is created with
   *    returned user-root private pointer.
   *
   * Returns a pointer to objagg object instance in case of success,
   * otherwise it returns pointer error using ERR_PTR macro.
   */
  struct objagg_obj *objagg_obj_get(struct objagg *objagg, void *obj)
  {
  	struct objagg_obj *objagg_obj;
  
  	objagg_obj = __objagg_obj_get(objagg, obj);
  	if (IS_ERR(objagg_obj))
  		return objagg_obj;
  	objagg_obj_stats_inc(objagg_obj);
  	trace_objagg_obj_get(objagg, objagg_obj, objagg_obj->refcount);
  	return objagg_obj;
  }
  EXPORT_SYMBOL(objagg_obj_get);
  
  static void objagg_obj_destroy(struct objagg *objagg,
  			       struct objagg_obj *objagg_obj)
  {
  	trace_objagg_obj_destroy(objagg, objagg_obj);
  	--objagg->obj_count;
  	list_del(&objagg_obj->list);
  	rhashtable_remove_fast(&objagg->obj_ht, &objagg_obj->ht_node,
  			       objagg->ht_params);
  	objagg_obj_fini(objagg, objagg_obj);
  	kfree(objagg_obj);
  }
  
  static void __objagg_obj_put(struct objagg *objagg,
  			     struct objagg_obj *objagg_obj)
  {
  	if (!objagg_obj_ref_dec(objagg_obj))
  		objagg_obj_destroy(objagg, objagg_obj);
  }
  
  /**
   * objagg_obj_put - puts an object within objagg instance
   * @objagg:	objagg instance
   * @objagg_obj:	objagg object instance
   *
   * Note: all locking must be provided by the caller.
   *
   * Symmetric to objagg_obj_get().
   */
  void objagg_obj_put(struct objagg *objagg, struct objagg_obj *objagg_obj)
  {
  	trace_objagg_obj_put(objagg, objagg_obj, objagg_obj->refcount);
  	objagg_obj_stats_dec(objagg_obj);
  	__objagg_obj_put(objagg, objagg_obj);
  }
  EXPORT_SYMBOL(objagg_obj_put);
  
  /**
   * objagg_create - creates a new objagg instance

   * @ops:		user-specific callbacks
   * @objagg_hints:	hints, can be NULL
   * @priv:		pointer to a private data passed to the ops

   *
   * Note: all locking must be provided by the caller.
   *
   * The purpose of the library is to provide an infrastructure to
   * aggregate user-specified objects. Library does not care about the type
   * of the object. User fills-up ops which take care of the specific
   * user object manipulation.
   *
   * As a very stupid example, consider integer numbers. For example
   * number 8 as a root object. That can aggregate number 9 with delta 1,
   * number 10 with delta 2, etc. This example is implemented as
   * a part of a testing module in test_objagg.c file.
   *
   * Each objagg instance contains multiple trees. Each tree node is
   * represented by "an object". In the current implementation there can be
   * only roots and leafs nodes. Leaf nodes are called deltas.
   * But in general, this can be easily extended for intermediate nodes.
   * In that extension, a delta would be associated with all non-root
   * nodes.
   *
   * Returns a pointer to newly created objagg instance in case of success,
   * otherwise it returns pointer error using ERR_PTR macro.
   */

  struct objagg *objagg_create(const struct objagg_ops *ops,
  			     struct objagg_hints *objagg_hints, void *priv)

  {
  	struct objagg *objagg;
  	int err;
  
  	if (WARN_ON(!ops || !ops->root_create || !ops->root_destroy ||

  		    !ops->delta_check || !ops->delta_create ||
  		    !ops->delta_destroy))

  		return ERR_PTR(-EINVAL);

  	objagg = kzalloc(sizeof(*objagg), GFP_KERNEL);
  	if (!objagg)
  		return ERR_PTR(-ENOMEM);
  	objagg->ops = ops;

  	if (objagg_hints) {
  		objagg->hints = objagg_hints;
  		objagg_hints->refcount++;
  	}

  	objagg->priv = priv;
  	INIT_LIST_HEAD(&objagg->obj_list);
  
  	objagg->ht_params.key_len = ops->obj_size;
  	objagg->ht_params.key_offset = offsetof(struct objagg_obj, obj);
  	objagg->ht_params.head_offset = offsetof(struct objagg_obj, ht_node);
  
  	err = rhashtable_init(&objagg->obj_ht, &objagg->ht_params);
  	if (err)
  		goto err_rhashtable_init;

  	ida_init(&objagg->root_ida);

  	trace_objagg_create(objagg);
  	return objagg;
  
  err_rhashtable_init:
  	kfree(objagg);
  	return ERR_PTR(err);
  }
  EXPORT_SYMBOL(objagg_create);
  
  /**
   * objagg_destroy - destroys a new objagg instance
   * @objagg:	objagg instance
   *
   * Note: all locking must be provided by the caller.
   */
  void objagg_destroy(struct objagg *objagg)
  {
  	trace_objagg_destroy(objagg);

  	ida_destroy(&objagg->root_ida);

  	WARN_ON(!list_empty(&objagg->obj_list));
  	rhashtable_destroy(&objagg->obj_ht);

  	if (objagg->hints)
  		objagg_hints_put(objagg->hints);

  	kfree(objagg);
  }
  EXPORT_SYMBOL(objagg_destroy);
  
  static int objagg_stats_info_sort_cmp_func(const void *a, const void *b)
  {
  	const struct objagg_obj_stats_info *stats_info1 = a;
  	const struct objagg_obj_stats_info *stats_info2 = b;
  
  	if (stats_info1->is_root != stats_info2->is_root)
  		return stats_info2->is_root - stats_info1->is_root;
  	if (stats_info1->stats.delta_user_count !=
  	    stats_info2->stats.delta_user_count)
  		return stats_info2->stats.delta_user_count -
  		       stats_info1->stats.delta_user_count;
  	return stats_info2->stats.user_count - stats_info1->stats.user_count;
  }
  
  /**
   * objagg_stats_get - obtains stats of the objagg instance
   * @objagg:	objagg instance
   *
   * Note: all locking must be provided by the caller.
   *
   * The returned structure contains statistics of all object
   * currently in use, ordered by following rules:
   * 1) Root objects are always on lower indexes than the rest.
   * 2) Objects with higher delta user count are always on lower
   *    indexes.
   * 3) In case more objects have the same delta user count,
   *    the objects are ordered by user count.
   *
   * Returns a pointer to stats instance in case of success,
   * otherwise it returns pointer error using ERR_PTR macro.
   */
  const struct objagg_stats *objagg_stats_get(struct objagg *objagg)
  {
  	struct objagg_stats *objagg_stats;
  	struct objagg_obj *objagg_obj;

  	int i;

  	objagg_stats = kzalloc(struct_size(objagg_stats, stats_info,
  					   objagg->obj_count), GFP_KERNEL);

  	if (!objagg_stats)
  		return ERR_PTR(-ENOMEM);
  
  	i = 0;
  	list_for_each_entry(objagg_obj, &objagg->obj_list, list) {
  		memcpy(&objagg_stats->stats_info[i].stats, &objagg_obj->stats,
  		       sizeof(objagg_stats->stats_info[0].stats));
  		objagg_stats->stats_info[i].objagg_obj = objagg_obj;
  		objagg_stats->stats_info[i].is_root =
  					objagg_obj_is_root(objagg_obj);

  		if (objagg_stats->stats_info[i].is_root)
  			objagg_stats->root_count++;

  		i++;
  	}
  	objagg_stats->stats_info_count = i;
  
  	sort(objagg_stats->stats_info, objagg_stats->stats_info_count,
  	     sizeof(struct objagg_obj_stats_info),
  	     objagg_stats_info_sort_cmp_func, NULL);
  
  	return objagg_stats;
  }
  EXPORT_SYMBOL(objagg_stats_get);
  
  /**

   * objagg_stats_put - puts stats of the objagg instance

   * @objagg_stats:	objagg instance stats
   *
   * Note: all locking must be provided by the caller.
   */
  void objagg_stats_put(const struct objagg_stats *objagg_stats)
  {
  	kfree(objagg_stats);
  }
  EXPORT_SYMBOL(objagg_stats_put);

  static struct objagg_hints_node *
  objagg_hints_node_create(struct objagg_hints *objagg_hints,
  			 struct objagg_obj *objagg_obj, size_t obj_size,
  			 struct objagg_hints_node *parent_hnode)
  {
  	unsigned int user_count = objagg_obj->stats.user_count;
  	struct objagg_hints_node *hnode;
  	int err;
  
  	hnode = kzalloc(sizeof(*hnode) + obj_size, GFP_KERNEL);
  	if (!hnode)
  		return ERR_PTR(-ENOMEM);
  	memcpy(hnode->obj, &objagg_obj->obj, obj_size);
  	hnode->stats_info.stats.user_count = user_count;
  	hnode->stats_info.stats.delta_user_count = user_count;
  	if (parent_hnode) {
  		parent_hnode->stats_info.stats.delta_user_count += user_count;
  	} else {
  		hnode->root_id = objagg_hints->root_count++;
  		hnode->stats_info.is_root = true;
  	}
  	hnode->stats_info.objagg_obj = objagg_obj;
  
  	err = rhashtable_insert_fast(&objagg_hints->node_ht, &hnode->ht_node,
  				     objagg_hints->ht_params);
  	if (err)
  		goto err_ht_insert;
  
  	list_add(&hnode->list, &objagg_hints->node_list);
  	hnode->parent = parent_hnode;
  	objagg_hints->node_count++;
  
  	return hnode;
  
  err_ht_insert:
  	kfree(hnode);
  	return ERR_PTR(err);
  }
  
  static void objagg_hints_flush(struct objagg_hints *objagg_hints)
  {
  	struct objagg_hints_node *hnode, *tmp;
  
  	list_for_each_entry_safe(hnode, tmp, &objagg_hints->node_list, list) {
  		list_del(&hnode->list);
  		rhashtable_remove_fast(&objagg_hints->node_ht, &hnode->ht_node,
  				       objagg_hints->ht_params);
  		kfree(hnode);
  	}
  }
  
  struct objagg_tmp_node {
  	struct objagg_obj *objagg_obj;
  	bool crossed_out;
  };
  
  struct objagg_tmp_graph {
  	struct objagg_tmp_node *nodes;
  	unsigned long nodes_count;
  	unsigned long *edges;
  };
  
  static int objagg_tmp_graph_edge_index(struct objagg_tmp_graph *graph,
  				       int parent_index, int index)
  {
  	return index * graph->nodes_count + parent_index;
  }
  
  static void objagg_tmp_graph_edge_set(struct objagg_tmp_graph *graph,
  				      int parent_index, int index)
  {
  	int edge_index = objagg_tmp_graph_edge_index(graph, index,
  						     parent_index);
  
  	__set_bit(edge_index, graph->edges);
  }
  
  static bool objagg_tmp_graph_is_edge(struct objagg_tmp_graph *graph,
  				     int parent_index, int index)
  {
  	int edge_index = objagg_tmp_graph_edge_index(graph, index,
  						     parent_index);
  
  	return test_bit(edge_index, graph->edges);
  }
  
  static unsigned int objagg_tmp_graph_node_weight(struct objagg_tmp_graph *graph,
  						 unsigned int index)
  {
  	struct objagg_tmp_node *node = &graph->nodes[index];
  	unsigned int weight = node->objagg_obj->stats.user_count;
  	int j;
  
  	/* Node weight is sum of node users and all other nodes users
  	 * that this node can represent with delta.
  	 */

  	for (j = 0; j < graph->nodes_count; j++) {
  		if (!objagg_tmp_graph_is_edge(graph, index, j))
  			continue;
  		node = &graph->nodes[j];
  		if (node->crossed_out)
  			continue;
  		weight += node->objagg_obj->stats.user_count;
  	}
  	return weight;
  }
  
  static int objagg_tmp_graph_node_max_weight(struct objagg_tmp_graph *graph)
  {

  	struct objagg_tmp_node *node;

  	unsigned int max_weight = 0;
  	unsigned int weight;
  	int max_index = -1;
  	int i;
  
  	for (i = 0; i < graph->nodes_count; i++) {

  		node = &graph->nodes[i];
  		if (node->crossed_out)
  			continue;

  		weight = objagg_tmp_graph_node_weight(graph, i);

  		if (weight >= max_weight) {

  			max_weight = weight;
  			max_index = i;
  		}
  	}
  	return max_index;
  }
  
  static struct objagg_tmp_graph *objagg_tmp_graph_create(struct objagg *objagg)
  {
  	unsigned int nodes_count = objagg->obj_count;
  	struct objagg_tmp_graph *graph;
  	struct objagg_tmp_node *node;
  	struct objagg_tmp_node *pnode;
  	struct objagg_obj *objagg_obj;
  	size_t alloc_size;
  	int i, j;
  
  	graph = kzalloc(sizeof(*graph), GFP_KERNEL);
  	if (!graph)
  		return NULL;
  
  	graph->nodes = kcalloc(nodes_count, sizeof(*graph->nodes), GFP_KERNEL);
  	if (!graph->nodes)
  		goto err_nodes_alloc;
  	graph->nodes_count = nodes_count;
  
  	alloc_size = BITS_TO_LONGS(nodes_count * nodes_count) *
  		     sizeof(unsigned long);
  	graph->edges = kzalloc(alloc_size, GFP_KERNEL);
  	if (!graph->edges)
  		goto err_edges_alloc;
  
  	i = 0;
  	list_for_each_entry(objagg_obj, &objagg->obj_list, list) {
  		node = &graph->nodes[i++];
  		node->objagg_obj = objagg_obj;
  	}
  
  	/* Assemble a temporary graph. Insert edge X->Y in case Y can be
  	 * in delta of X.
  	 */
  	for (i = 0; i < nodes_count; i++) {
  		for (j = 0; j < nodes_count; j++) {
  			if (i == j)
  				continue;
  			pnode = &graph->nodes[i];
  			node = &graph->nodes[j];
  			if (objagg->ops->delta_check(objagg->priv,
  						     pnode->objagg_obj->obj,
  						     node->objagg_obj->obj)) {
  				objagg_tmp_graph_edge_set(graph, i, j);
  
  			}
  		}
  	}
  	return graph;
  
  err_edges_alloc:
  	kfree(graph->nodes);
  err_nodes_alloc:
  	kfree(graph);
  	return NULL;
  }
  
  static void objagg_tmp_graph_destroy(struct objagg_tmp_graph *graph)
  {
  	kfree(graph->edges);
  	kfree(graph->nodes);
  	kfree(graph);
  }
  
  static int
  objagg_opt_simple_greedy_fillup_hints(struct objagg_hints *objagg_hints,
  				      struct objagg *objagg)
  {
  	struct objagg_hints_node *hnode, *parent_hnode;
  	struct objagg_tmp_graph *graph;
  	struct objagg_tmp_node *node;
  	int index;
  	int j;
  	int err;
  
  	graph = objagg_tmp_graph_create(objagg);
  	if (!graph)
  		return -ENOMEM;
  
  	/* Find the nodes from the ones that can accommodate most users
  	 * and cross them out of the graph. Save them to the hint list.
  	 */
  	while ((index = objagg_tmp_graph_node_max_weight(graph)) != -1) {
  		node = &graph->nodes[index];
  		node->crossed_out = true;
  		hnode = objagg_hints_node_create(objagg_hints,
  						 node->objagg_obj,
  						 objagg->ops->obj_size,
  						 NULL);
  		if (IS_ERR(hnode)) {
  			err = PTR_ERR(hnode);
  			goto out;
  		}
  		parent_hnode = hnode;
  		for (j = 0; j < graph->nodes_count; j++) {
  			if (!objagg_tmp_graph_is_edge(graph, index, j))
  				continue;
  			node = &graph->nodes[j];
  			if (node->crossed_out)
  				continue;
  			node->crossed_out = true;
  			hnode = objagg_hints_node_create(objagg_hints,
  							 node->objagg_obj,
  							 objagg->ops->obj_size,
  							 parent_hnode);
  			if (IS_ERR(hnode)) {
  				err = PTR_ERR(hnode);
  				goto out;
  			}
  		}
  	}
  
  	err = 0;
  out:
  	objagg_tmp_graph_destroy(graph);
  	return err;
  }
  
  struct objagg_opt_algo {
  	int (*fillup_hints)(struct objagg_hints *objagg_hints,
  			    struct objagg *objagg);
  };
  
  static const struct objagg_opt_algo objagg_opt_simple_greedy = {
  	.fillup_hints = objagg_opt_simple_greedy_fillup_hints,
  };
  
  
  static const struct objagg_opt_algo *objagg_opt_algos[] = {
  	[OBJAGG_OPT_ALGO_SIMPLE_GREEDY] = &objagg_opt_simple_greedy,
  };
  
  static int objagg_hints_obj_cmp(struct rhashtable_compare_arg *arg,
  				const void *obj)
  {
  	struct rhashtable *ht = arg->ht;
  	struct objagg_hints *objagg_hints =
  			container_of(ht, struct objagg_hints, node_ht);
  	const struct objagg_ops *ops = objagg_hints->ops;
  	const char *ptr = obj;
  
  	ptr += ht->p.key_offset;
  	return ops->hints_obj_cmp ? ops->hints_obj_cmp(ptr, arg->key) :
  				    memcmp(ptr, arg->key, ht->p.key_len);
  }
  
  /**
   * objagg_hints_get - obtains hints instance
   * @objagg:		objagg instance
   * @opt_algo_type:	type of hints finding algorithm
   *
   * Note: all locking must be provided by the caller.
   *
   * According to the algo type, the existing objects of objagg instance
   * are going to be went-through to assemble an optimal tree. We call this
   * tree hints. These hints can be later on used for creation of
   * a new objagg instance. There, the future object creations are going
   * to be consulted with these hints in order to find out, where exactly
   * the new object should be put as a root or delta.
   *
   * Returns a pointer to hints instance in case of success,
   * otherwise it returns pointer error using ERR_PTR macro.
   */
  struct objagg_hints *objagg_hints_get(struct objagg *objagg,
  				      enum objagg_opt_algo_type opt_algo_type)
  {
  	const struct objagg_opt_algo *algo = objagg_opt_algos[opt_algo_type];
  	struct objagg_hints *objagg_hints;
  	int err;
  
  	objagg_hints = kzalloc(sizeof(*objagg_hints), GFP_KERNEL);
  	if (!objagg_hints)
  		return ERR_PTR(-ENOMEM);
  
  	objagg_hints->ops = objagg->ops;
  	objagg_hints->refcount = 1;
  
  	INIT_LIST_HEAD(&objagg_hints->node_list);
  
  	objagg_hints->ht_params.key_len = objagg->ops->obj_size;
  	objagg_hints->ht_params.key_offset =
  				offsetof(struct objagg_hints_node, obj);
  	objagg_hints->ht_params.head_offset =
  				offsetof(struct objagg_hints_node, ht_node);
  	objagg_hints->ht_params.obj_cmpfn = objagg_hints_obj_cmp;
  
  	err = rhashtable_init(&objagg_hints->node_ht, &objagg_hints->ht_params);
  	if (err)
  		goto err_rhashtable_init;
  
  	err = algo->fillup_hints(objagg_hints, objagg);
  	if (err)
  		goto err_fillup_hints;

  	if (WARN_ON(objagg_hints->node_count != objagg->obj_count)) {
  		err = -EINVAL;

  		goto err_node_count_check;

  	}

  
  	return objagg_hints;
  
  err_node_count_check:
  err_fillup_hints:
  	objagg_hints_flush(objagg_hints);
  	rhashtable_destroy(&objagg_hints->node_ht);
  err_rhashtable_init:
  	kfree(objagg_hints);
  	return ERR_PTR(err);
  }
  EXPORT_SYMBOL(objagg_hints_get);
  
  /**
   * objagg_hints_put - puts hints instance
   * @objagg_hints:	objagg hints instance
   *
   * Note: all locking must be provided by the caller.
   */
  void objagg_hints_put(struct objagg_hints *objagg_hints)
  {
  	if (--objagg_hints->refcount)
  		return;
  	objagg_hints_flush(objagg_hints);
  	rhashtable_destroy(&objagg_hints->node_ht);
  	kfree(objagg_hints);
  }
  EXPORT_SYMBOL(objagg_hints_put);
  
  /**
   * objagg_hints_stats_get - obtains stats of the hints instance
   * @objagg_hints:	hints instance
   *
   * Note: all locking must be provided by the caller.
   *
   * The returned structure contains statistics of all objects
   * currently in use, ordered by following rules:
   * 1) Root objects are always on lower indexes than the rest.
   * 2) Objects with higher delta user count are always on lower
   *    indexes.
   * 3) In case multiple objects have the same delta user count,
   *    the objects are ordered by user count.
   *
   * Returns a pointer to stats instance in case of success,
   * otherwise it returns pointer error using ERR_PTR macro.
   */
  const struct objagg_stats *
  objagg_hints_stats_get(struct objagg_hints *objagg_hints)
  {
  	struct objagg_stats *objagg_stats;
  	struct objagg_hints_node *hnode;
  	int i;
  
  	objagg_stats = kzalloc(struct_size(objagg_stats, stats_info,
  					   objagg_hints->node_count),
  			       GFP_KERNEL);
  	if (!objagg_stats)
  		return ERR_PTR(-ENOMEM);
  
  	i = 0;
  	list_for_each_entry(hnode, &objagg_hints->node_list, list) {
  		memcpy(&objagg_stats->stats_info[i], &hnode->stats_info,
  		       sizeof(objagg_stats->stats_info[0]));

  		if (objagg_stats->stats_info[i].is_root)
  			objagg_stats->root_count++;

  		i++;
  	}
  	objagg_stats->stats_info_count = i;
  
  	sort(objagg_stats->stats_info, objagg_stats->stats_info_count,
  	     sizeof(struct objagg_obj_stats_info),
  	     objagg_stats_info_sort_cmp_func, NULL);
  
  	return objagg_stats;
  }
  EXPORT_SYMBOL(objagg_hints_stats_get);

  MODULE_LICENSE("Dual BSD/GPL");
  MODULE_AUTHOR("Jiri Pirko <jiri@mellanox.com>");
  MODULE_DESCRIPTION("Object aggregation manager");