Adding upstream version 6.1.76.upstream/6.1.76

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1051 insertions, 0 deletions

diff --git a/lib/objagg.c b/lib/objagg.c
new file mode 100644
index 000000000..1e248629e
--- /dev/null
+++ b/lib/objagg.c
@@ -0,0 +1,1051 @@
+// 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[];
+};
+
+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[];
+};
+
+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;
+	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;
+
+	graph->edges = bitmap_zalloc(nodes_count * nodes_count, 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)
+{
+	bitmap_free(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");