lib: introduce initial implementation of object aggregation manager

This lib tracks objects which could be of two types:
1) root object
2) nested object - with a "delta" which differentiates it from
                   the associated root object
The objects are tracked by a hashtable and reference-counted. User is
responsible of implementing callbacks to create/destroy root entity
related to each root object and callback to create/destroy nested object
delta.

Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

8 files changed, 1633 insertions, 0 deletions

diff --git a/MAINTAINERS b/MAINTAINERS
index e110e327bf38..3bd775ba51ce 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -10679,6 +10679,14 @@ L:	linux-nfc@lists.01.org (moderated for non-subscribers)
 S:	Supported
 F:	drivers/nfc/nxp-nci
 
+OBJAGG
+M:	Jiri Pirko <jiri@mellanox.com>
+L:	netdev@vger.kernel.org
+S:	Supported
+F:	lib/objagg.c
+F:	lib/test_objagg.c
+F:	include/linux/objagg.h
+
 OBJTOOL
 M:	Josh Poimboeuf <jpoimboe@redhat.com>
 M:	Peter Zijlstra <peterz@infradead.org>
diff --git a/include/linux/objagg.h b/include/linux/objagg.h
new file mode 100644
index 000000000000..34f38c186ea0
--- /dev/null
+++ b/include/linux/objagg.h
@@ -0,0 +1,46 @@
+/* SPDX-License-Identifier: BSD-3-Clause OR GPL-2.0 */
+/* Copyright (c) 2018 Mellanox Technologies. All rights reserved */
+
+#ifndef _OBJAGG_H
+#define _OBJAGG_H
+
+struct objagg_ops {
+	size_t obj_size;
+	void * (*delta_create)(void *priv, void *parent_obj, void *obj);
+	void (*delta_destroy)(void *priv, void *delta_priv);
+	void * (*root_create)(void *priv, void *obj);
+	void (*root_destroy)(void *priv, void *root_priv);
+};
+
+struct objagg;
+struct objagg_obj;
+
+const void *objagg_obj_root_priv(const struct objagg_obj *objagg_obj);
+const void *objagg_obj_delta_priv(const struct objagg_obj *objagg_obj);
+const void *objagg_obj_raw(const struct objagg_obj *objagg_obj);
+
+struct objagg_obj *objagg_obj_get(struct objagg *objagg, void *obj);
+void objagg_obj_put(struct objagg *objagg, struct objagg_obj *objagg_obj);
+struct objagg *objagg_create(const struct objagg_ops *ops, void *priv);
+void objagg_destroy(struct objagg *objagg);
+
+struct objagg_obj_stats {
+	unsigned int user_count;
+	unsigned int delta_user_count; /* includes delta object users */
+};
+
+struct objagg_obj_stats_info {
+	struct objagg_obj_stats stats;
+	struct objagg_obj *objagg_obj; /* associated object */
+	bool is_root;
+};
+
+struct objagg_stats {
+	unsigned int stats_info_count;
+	struct objagg_obj_stats_info stats_info[];
+};
+
+const struct objagg_stats *objagg_stats_get(struct objagg *objagg);
+void objagg_stats_put(const struct objagg_stats *objagg_stats);
+
+#endif
diff --git a/include/trace/events/objagg.h b/include/trace/events/objagg.h
new file mode 100644
index 000000000000..fcec0fc9eb0c
--- /dev/null
+++ b/include/trace/events/objagg.h
@@ -0,0 +1,228 @@
+/* SPDX-License-Identifier: BSD-3-Clause OR GPL-2.0 */
+/* Copyright (c) 2018 Mellanox Technologies. All rights reserved */
+
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM objagg
+
+#if !defined(__TRACE_OBJAGG_H) || defined(TRACE_HEADER_MULTI_READ)
+#define __TRACE_OBJAGG_H
+
+#include <linux/tracepoint.h>
+
+struct objagg;
+struct objagg_obj;
+
+TRACE_EVENT(objagg_create,
+	TP_PROTO(const struct objagg *objagg),
+
+	TP_ARGS(objagg),
+
+	TP_STRUCT__entry(
+		__field(const void *, objagg)
+	),
+
+	TP_fast_assign(
+		__entry->objagg = objagg;
+	),
+
+	TP_printk("objagg %p", __entry->objagg)
+);
+
+TRACE_EVENT(objagg_destroy,
+	TP_PROTO(const struct objagg *objagg),
+
+	TP_ARGS(objagg),
+
+	TP_STRUCT__entry(
+		__field(const void *, objagg)
+	),
+
+	TP_fast_assign(
+		__entry->objagg = objagg;
+	),
+
+	TP_printk("objagg %p", __entry->objagg)
+);
+
+TRACE_EVENT(objagg_obj_create,
+	TP_PROTO(const struct objagg *objagg,
+		 const struct objagg_obj *obj),
+
+	TP_ARGS(objagg, obj),
+
+	TP_STRUCT__entry(
+		__field(const void *, objagg)
+		__field(const void *, obj)
+	),
+
+	TP_fast_assign(
+		__entry->objagg = objagg;
+		__entry->obj = obj;
+	),
+
+	TP_printk("objagg %p, obj %p", __entry->objagg, __entry->obj)
+);
+
+TRACE_EVENT(objagg_obj_destroy,
+	TP_PROTO(const struct objagg *objagg,
+		 const struct objagg_obj *obj),
+
+	TP_ARGS(objagg, obj),
+
+	TP_STRUCT__entry(
+		__field(const void *, objagg)
+		__field(const void *, obj)
+	),
+
+	TP_fast_assign(
+		__entry->objagg = objagg;
+		__entry->obj = obj;
+	),
+
+	TP_printk("objagg %p, obj %p", __entry->objagg, __entry->obj)
+);
+
+TRACE_EVENT(objagg_obj_get,
+	TP_PROTO(const struct objagg *objagg,
+		 const struct objagg_obj *obj,
+		 unsigned int refcount),
+
+	TP_ARGS(objagg, obj, refcount),
+
+	TP_STRUCT__entry(
+		__field(const void *, objagg)
+		__field(const void *, obj)
+		__field(unsigned int, refcount)
+	),
+
+	TP_fast_assign(
+		__entry->objagg = objagg;
+		__entry->obj = obj;
+		__entry->refcount = refcount;
+	),
+
+	TP_printk("objagg %p, obj %p, refcount %u",
+		  __entry->objagg, __entry->obj, __entry->refcount)
+);
+
+TRACE_EVENT(objagg_obj_put,
+	TP_PROTO(const struct objagg *objagg,
+		 const struct objagg_obj *obj,
+		 unsigned int refcount),
+
+	TP_ARGS(objagg, obj, refcount),
+
+	TP_STRUCT__entry(
+		__field(const void *, objagg)
+		__field(const void *, obj)
+		__field(unsigned int, refcount)
+	),
+
+	TP_fast_assign(
+		__entry->objagg = objagg;
+		__entry->obj = obj;
+		__entry->refcount = refcount;
+	),
+
+	TP_printk("objagg %p, obj %p, refcount %u",
+		  __entry->objagg, __entry->obj, __entry->refcount)
+);
+
+TRACE_EVENT(objagg_obj_parent_assign,
+	TP_PROTO(const struct objagg *objagg,
+		 const struct objagg_obj *obj,
+		 const struct objagg_obj *parent,
+		 unsigned int parent_refcount),
+
+	TP_ARGS(objagg, obj, parent, parent_refcount),
+
+	TP_STRUCT__entry(
+		__field(const void *, objagg)
+		__field(const void *, obj)
+		__field(const void *, parent)
+		__field(unsigned int, parent_refcount)
+	),
+
+	TP_fast_assign(
+		__entry->objagg = objagg;
+		__entry->obj = obj;
+		__entry->parent = parent;
+		__entry->parent_refcount = parent_refcount;
+	),
+
+	TP_printk("objagg %p, obj %p, parent %p, parent_refcount %u",
+		  __entry->objagg, __entry->obj,
+		  __entry->parent, __entry->parent_refcount)
+);
+
+TRACE_EVENT(objagg_obj_parent_unassign,
+	TP_PROTO(const struct objagg *objagg,
+		 const struct objagg_obj *obj,
+		 const struct objagg_obj *parent,
+		 unsigned int parent_refcount),
+
+	TP_ARGS(objagg, obj, parent, parent_refcount),
+
+	TP_STRUCT__entry(
+		__field(const void *, objagg)
+		__field(const void *, obj)
+		__field(const void *, parent)
+		__field(unsigned int, parent_refcount)
+	),
+
+	TP_fast_assign(
+		__entry->objagg = objagg;
+		__entry->obj = obj;
+		__entry->parent = parent;
+		__entry->parent_refcount = parent_refcount;
+	),
+
+	TP_printk("objagg %p, obj %p, parent %p, parent_refcount %u",
+		  __entry->objagg, __entry->obj,
+		  __entry->parent, __entry->parent_refcount)
+);
+
+TRACE_EVENT(objagg_obj_root_create,
+	TP_PROTO(const struct objagg *objagg,
+		 const struct objagg_obj *obj),
+
+	TP_ARGS(objagg, obj),
+
+	TP_STRUCT__entry(
+		__field(const void *, objagg)
+		__field(const void *, obj)
+	),
+
+	TP_fast_assign(
+		__entry->objagg = objagg;
+		__entry->obj = obj;
+	),
+
+	TP_printk("objagg %p, obj %p",
+		  __entry->objagg, __entry->obj)
+);
+
+TRACE_EVENT(objagg_obj_root_destroy,
+	TP_PROTO(const struct objagg *objagg,
+		 const struct objagg_obj *obj),
+
+	TP_ARGS(objagg, obj),
+
+	TP_STRUCT__entry(
+		__field(const void *, objagg)
+		__field(const void *, obj)
+	),
+
+	TP_fast_assign(
+		__entry->objagg = objagg;
+		__entry->obj = obj;
+	),
+
+	TP_printk("objagg %p, obj %p",
+		  __entry->objagg, __entry->obj)
+);
+
+#endif /* __TRACE_OBJAGG_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>
diff --git a/lib/Kconfig b/lib/Kconfig
index a9965f4af4dd..7dbbcfe9cd90 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -624,3 +624,6 @@ config GENERIC_LIB_CMPDI2
 
 config GENERIC_LIB_UCMPDI2
 	bool
+
+config OBJAGG
+	tristate "objagg" if COMPILE_TEST
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 1af29b8224fd..b3c91b9e32f8 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1976,6 +1976,16 @@ config TEST_MEMCAT_P
 
 	  If unsure, say N.
 
+config TEST_OBJAGG
+	tristate "Perform selftest on object aggreration manager"
+	default n
+	depends on OBJAGG
+	help
+	  Enable this option to test object aggregation manager on boot
+	  (or module load).
+
+	  If unsure, say N.
+
 endif # RUNTIME_TESTING_MENU
 
 config MEMTEST
diff --git a/lib/Makefile b/lib/Makefile
index db06d1237898..f5262d30bfe6 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -75,6 +75,7 @@ obj-$(CONFIG_TEST_PARMAN) += test_parman.o
 obj-$(CONFIG_TEST_KMOD) += test_kmod.o
 obj-$(CONFIG_TEST_DEBUG_VIRTUAL) += test_debug_virtual.o
 obj-$(CONFIG_TEST_MEMCAT_P) += test_memcat_p.o
+obj-$(CONFIG_TEST_OBJAGG) += test_objagg.o
 
 ifeq ($(CONFIG_DEBUG_KOBJECT),y)
 CFLAGS_kobject.o += -DDEBUG
@@ -274,3 +275,4 @@ obj-$(CONFIG_GENERIC_LIB_LSHRDI3) += lshrdi3.o
 obj-$(CONFIG_GENERIC_LIB_MULDI3) += muldi3.o
 obj-$(CONFIG_GENERIC_LIB_CMPDI2) += cmpdi2.o
 obj-$(CONFIG_GENERIC_LIB_UCMPDI2) += ucmpdi2.o
+obj-$(CONFIG_OBJAGG) += objagg.o
diff --git a/lib/objagg.c b/lib/objagg.c
new file mode 100644
index 000000000000..c9b457a91153
--- /dev/null
+++ b/lib/objagg.c
@@ -0,0 +1,501 @@
+// 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/list.h>
+#include <linux/sort.h>
+#include <linux/objagg.h>
+
+#define CREATE_TRACE_POINTS
+#include <trace/events/objagg.h>
+
+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 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 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)
+{
+	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;
+	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);
+		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_create(struct objagg *objagg,
+				  struct objagg_obj *objagg_obj)
+{
+	objagg_obj->root_priv = objagg->ops->root_create(objagg->priv,
+							 objagg_obj->obj);
+	if (IS_ERR(objagg_obj->root_priv))
+		return PTR_ERR(objagg_obj->root_priv);
+
+	trace_objagg_obj_root_create(objagg, objagg_obj);
+	return 0;
+}
+
+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);
+}
+
+static int objagg_obj_init(struct objagg *objagg,
+			   struct objagg_obj *objagg_obj)
+{
+	int err;
+
+	/* 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);
+}
+
+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
+ * @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, void *priv)
+{
+	struct objagg *objagg;
+	int err;
+
+	if (WARN_ON(!ops || !ops->root_create || !ops->root_destroy ||
+		    !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;
+	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;
+
+	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);
+	WARN_ON(!list_empty(&objagg->obj_list));
+	rhashtable_destroy(&objagg->obj_ht);
+	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;
+	size_t alloc_size;
+	int i;
+
+	alloc_size = sizeof(*objagg_stats) +
+		     sizeof(objagg_stats->stats_info[0]) * objagg->obj_count;
+	objagg_stats = kzalloc(alloc_size, 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);
+		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_puts - 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);
+
+MODULE_LICENSE("Dual BSD/GPL");
+MODULE_AUTHOR("Jiri Pirko <jiri@mellanox.com>");
+MODULE_DESCRIPTION("Object aggregation manager");
diff --git a/lib/test_objagg.c b/lib/test_objagg.c
new file mode 100644
index 000000000000..aac5d8e8800c
--- /dev/null
+++ b/lib/test_objagg.c
@@ -0,0 +1,835 @@
+// SPDX-License-Identifier: BSD-3-Clause OR GPL-2.0
+/* Copyright (c) 2018 Mellanox Technologies. All rights reserved */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/random.h>
+#include <linux/objagg.h>
+
+struct tokey {
+	unsigned int id;
+};
+
+#define NUM_KEYS 32
+
+static int key_id_index(unsigned int key_id)
+{
+	if (key_id >= NUM_KEYS) {
+		WARN_ON(1);
+		return 0;
+	}
+	return key_id;
+}
+
+#define BUF_LEN 128
+
+struct world {
+	unsigned int root_count;
+	unsigned int delta_count;
+	char next_root_buf[BUF_LEN];
+	struct objagg_obj *objagg_objs[NUM_KEYS];
+	unsigned int key_refs[NUM_KEYS];
+};
+
+struct root {
+	struct tokey key;
+	char buf[BUF_LEN];
+};
+
+struct delta {
+	unsigned int key_id_diff;
+};
+
+static struct objagg_obj *world_obj_get(struct world *world,
+					struct objagg *objagg,
+					unsigned int key_id)
+{
+	struct objagg_obj *objagg_obj;
+	struct tokey key;
+	int err;
+
+	key.id = key_id;
+	objagg_obj = objagg_obj_get(objagg, &key);
+	if (IS_ERR(objagg_obj)) {
+		pr_err("Key %u: Failed to get object.\n", key_id);
+		return objagg_obj;
+	}
+	if (!world->key_refs[key_id_index(key_id)]) {
+		world->objagg_objs[key_id_index(key_id)] = objagg_obj;
+	} else if (world->objagg_objs[key_id_index(key_id)] != objagg_obj) {
+		pr_err("Key %u: God another object for the same key.\n",
+		       key_id);
+		err = -EINVAL;
+		goto err_key_id_check;
+	}
+	world->key_refs[key_id_index(key_id)]++;
+	return objagg_obj;
+
+err_key_id_check:
+	objagg_obj_put(objagg, objagg_obj);
+	return ERR_PTR(err);
+}
+
+static void world_obj_put(struct world *world, struct objagg *objagg,
+			  unsigned int key_id)
+{
+	struct objagg_obj *objagg_obj;
+
+	if (!world->key_refs[key_id_index(key_id)])
+		return;
+	objagg_obj = world->objagg_objs[key_id_index(key_id)];
+	objagg_obj_put(objagg, objagg_obj);
+	world->key_refs[key_id_index(key_id)]--;
+}
+
+#define MAX_KEY_ID_DIFF 5
+
+static void *delta_create(void *priv, void *parent_obj, void *obj)
+{
+	struct tokey *parent_key = parent_obj;
+	struct world *world = priv;
+	struct tokey *key = obj;
+	int diff = key->id - parent_key->id;
+	struct delta *delta;
+
+	if (diff < 0 || diff > MAX_KEY_ID_DIFF)
+		return ERR_PTR(-EINVAL);
+
+	delta = kzalloc(sizeof(*delta), GFP_KERNEL);
+	if (!delta)
+		return ERR_PTR(-ENOMEM);
+	delta->key_id_diff = diff;
+	world->delta_count++;
+	return delta;
+}
+
+static void delta_destroy(void *priv, void *delta_priv)
+{
+	struct delta *delta = delta_priv;
+	struct world *world = priv;
+
+	world->delta_count--;
+	kfree(delta);
+}
+
+static void *root_create(void *priv, void *obj)
+{
+	struct world *world = priv;
+	struct tokey *key = obj;
+	struct root *root;
+
+	root = kzalloc(sizeof(*root), GFP_KERNEL);
+	if (!root)
+		return ERR_PTR(-ENOMEM);
+	memcpy(&root->key, key, sizeof(root->key));
+	memcpy(root->buf, world->next_root_buf, sizeof(root->buf));
+	world->root_count++;
+	return root;
+}
+
+static void root_destroy(void *priv, void *root_priv)
+{
+	struct root *root = root_priv;
+	struct world *world = priv;
+
+	world->root_count--;
+	kfree(root);
+}
+
+static int test_nodelta_obj_get(struct world *world, struct objagg *objagg,
+				unsigned int key_id, bool should_create_root)
+{
+	unsigned int orig_root_count = world->root_count;
+	struct objagg_obj *objagg_obj;
+	const struct root *root;
+	int err;
+
+	if (should_create_root)
+		prandom_bytes(world->next_root_buf,
+			      sizeof(world->next_root_buf));
+
+	objagg_obj = world_obj_get(world, objagg, key_id);
+	if (IS_ERR(objagg_obj)) {
+		pr_err("Key %u: Failed to get object.\n", key_id);
+		return PTR_ERR(objagg_obj);
+	}
+	if (should_create_root) {
+		if (world->root_count != orig_root_count + 1) {
+			pr_err("Key %u: Root was not created\n", key_id);
+			err = -EINVAL;
+			goto err_check_root_count;
+		}
+	} else {
+		if (world->root_count != orig_root_count) {
+			pr_err("Key %u: Root was incorrectly created\n",
+			       key_id);
+			err = -EINVAL;
+			goto err_check_root_count;
+		}
+	}
+	root = objagg_obj_root_priv(objagg_obj);
+	if (root->key.id != key_id) {
+		pr_err("Key %u: Root has unexpected key id\n", key_id);
+		err = -EINVAL;
+		goto err_check_key_id;
+	}
+	if (should_create_root &&
+	    memcmp(world->next_root_buf, root->buf, sizeof(root->buf))) {
+		pr_err("Key %u: Buffer does not match the expected content\n",
+		       key_id);
+		err = -EINVAL;
+		goto err_check_buf;
+	}
+	return 0;
+
+err_check_buf:
+err_check_key_id:
+err_check_root_count:
+	objagg_obj_put(objagg, objagg_obj);
+	return err;
+}
+
+static int test_nodelta_obj_put(struct world *world, struct objagg *objagg,
+				unsigned int key_id, bool should_destroy_root)
+{
+	unsigned int orig_root_count = world->root_count;
+
+	world_obj_put(world, objagg, key_id);
+
+	if (should_destroy_root) {
+		if (world->root_count != orig_root_count - 1) {
+			pr_err("Key %u: Root was not destroyed\n", key_id);
+			return -EINVAL;
+		}
+	} else {
+		if (world->root_count != orig_root_count) {
+			pr_err("Key %u: Root was incorrectly destroyed\n",
+			       key_id);
+			return -EINVAL;
+		}
+	}
+	return 0;
+}
+
+static int check_stats_zero(struct objagg *objagg)
+{
+	const struct objagg_stats *stats;
+	int err = 0;
+
+	stats = objagg_stats_get(objagg);
+	if (IS_ERR(stats))
+		return PTR_ERR(stats);
+
+	if (stats->stats_info_count != 0) {
+		pr_err("Stats: Object count is not zero while it should be\n");
+		err = -EINVAL;
+	}
+
+	objagg_stats_put(stats);
+	return err;
+}
+
+static int check_stats_nodelta(struct objagg *objagg)
+{
+	const struct objagg_stats *stats;
+	int i;
+	int err;
+
+	stats = objagg_stats_get(objagg);
+	if (IS_ERR(stats))
+		return PTR_ERR(stats);
+
+	if (stats->stats_info_count != NUM_KEYS) {
+		pr_err("Stats: Unexpected object count (%u expected, %u returned)\n",
+		       NUM_KEYS, stats->stats_info_count);
+		err = -EINVAL;
+		goto stats_put;
+	}
+
+	for (i = 0; i < stats->stats_info_count; i++) {
+		if (stats->stats_info[i].stats.user_count != 2) {
+			pr_err("Stats: incorrect user count\n");
+			err = -EINVAL;
+			goto stats_put;
+		}
+		if (stats->stats_info[i].stats.delta_user_count != 2) {
+			pr_err("Stats: incorrect delta user count\n");
+			err = -EINVAL;
+			goto stats_put;
+		}
+	}
+	err = 0;
+
+stats_put:
+	objagg_stats_put(stats);
+	return err;
+}
+
+static void *delta_create_dummy(void *priv, void *parent_obj, void *obj)
+{
+	return ERR_PTR(-EOPNOTSUPP);
+}
+
+static void delta_destroy_dummy(void *priv, void *delta_priv)
+{
+}
+
+static const struct objagg_ops nodelta_ops = {
+	.obj_size = sizeof(struct tokey),
+	.delta_create = delta_create_dummy,
+	.delta_destroy = delta_destroy_dummy,
+	.root_create = root_create,
+	.root_destroy = root_destroy,
+};
+
+static int test_nodelta(void)
+{
+	struct world world = {};
+	struct objagg *objagg;
+	int i;
+	int err;
+
+	objagg = objagg_create(&nodelta_ops, &world);
+	if (IS_ERR(objagg))
+		return PTR_ERR(objagg);
+
+	err = check_stats_zero(objagg);
+	if (err)
+		goto err_stats_first_zero;
+
+	/* First round of gets, the root objects should be created */
+	for (i = 0; i < NUM_KEYS; i++) {
+		err = test_nodelta_obj_get(&world, objagg, i, true);
+		if (err)
+			goto err_obj_first_get;
+	}
+
+	/* Do the second round of gets, all roots are already created,
+	 * make sure that no new root is created
+	 */
+	for (i = 0; i < NUM_KEYS; i++) {
+		err = test_nodelta_obj_get(&world, objagg, i, false);
+		if (err)
+			goto err_obj_second_get;
+	}
+
+	err = check_stats_nodelta(objagg);
+	if (err)
+		goto err_stats_nodelta;
+
+	for (i = NUM_KEYS - 1; i >= 0; i--) {
+		err = test_nodelta_obj_put(&world, objagg, i, false);
+		if (err)
+			goto err_obj_first_put;
+	}
+	for (i = NUM_KEYS - 1; i >= 0; i--) {
+		err = test_nodelta_obj_put(&world, objagg, i, true);
+		if (err)
+			goto err_obj_second_put;
+	}
+
+	err = check_stats_zero(objagg);
+	if (err)
+		goto err_stats_second_zero;
+
+	objagg_destroy(objagg);
+	return 0;
+
+err_stats_nodelta:
+err_obj_first_put:
+err_obj_second_get:
+	for (i--; i >= 0; i--)
+		world_obj_put(&world, objagg, i);
+
+	i = NUM_KEYS;
+err_obj_first_get:
+err_obj_second_put:
+	for (i--; i >= 0; i--)
+		world_obj_put(&world, objagg, i);
+err_stats_first_zero:
+err_stats_second_zero:
+	objagg_destroy(objagg);
+	return err;
+}
+
+static const struct objagg_ops delta_ops = {
+	.obj_size = sizeof(struct tokey),
+	.delta_create = delta_create,
+	.delta_destroy = delta_destroy,
+	.root_create = root_create,
+	.root_destroy = root_destroy,
+};
+
+enum action {
+	ACTION_GET,
+	ACTION_PUT,
+};
+
+enum expect_delta {
+	EXPECT_DELTA_SAME,
+	EXPECT_DELTA_INC,
+	EXPECT_DELTA_DEC,
+};
+
+enum expect_root {
+	EXPECT_ROOT_SAME,
+	EXPECT_ROOT_INC,
+	EXPECT_ROOT_DEC,
+};
+
+struct expect_stats_info {
+	struct objagg_obj_stats stats;
+	bool is_root;
+	unsigned int key_id;
+};
+
+struct expect_stats {
+	unsigned int info_count;
+	struct expect_stats_info info[NUM_KEYS];
+};
+
+struct action_item {
+	unsigned int key_id;
+	enum action action;
+	enum expect_delta expect_delta;
+	enum expect_root expect_root;
+	struct expect_stats expect_stats;
+};
+
+#define EXPECT_STATS(count, ...)		\
+{						\
+	.info_count = count,			\
+	.info = { __VA_ARGS__ }			\
+}
+
+#define ROOT(key_id, user_count, delta_user_count)	\
+	{{user_count, delta_user_count}, true, key_id}
+
+#define DELTA(key_id, user_count)			\
+	{{user_count, user_count}, false, key_id}
+
+static const struct action_item action_items[] = {
+	{
+		1, ACTION_GET, EXPECT_DELTA_SAME, EXPECT_ROOT_INC,
+		EXPECT_STATS(1, ROOT(1, 1, 1)),
+	},	/* r: 1			d: */
+	{
+		7, ACTION_GET, EXPECT_DELTA_SAME, EXPECT_ROOT_INC,
+		EXPECT_STATS(2, ROOT(1, 1, 1), ROOT(7, 1, 1)),
+	},	/* r: 1, 7		d: */
+	{
+		3, ACTION_GET, EXPECT_DELTA_INC, EXPECT_ROOT_SAME,
+		EXPECT_STATS(3, ROOT(1, 1, 2), ROOT(7, 1, 1),
+				DELTA(3, 1)),
+	},	/* r: 1, 7		d: 3^1 */
+	{
+		5, ACTION_GET, EXPECT_DELTA_INC, EXPECT_ROOT_SAME,
+		EXPECT_STATS(4, ROOT(1, 1, 3), ROOT(7, 1, 1),
+				DELTA(3, 1), DELTA(5, 1)),
+	},	/* r: 1, 7		d: 3^1, 5^1 */
+	{
+		3, ACTION_GET, EXPECT_DELTA_SAME, EXPECT_ROOT_SAME,
+		EXPECT_STATS(4, ROOT(1, 1, 4), ROOT(7, 1, 1),
+				DELTA(3, 2), DELTA(5, 1)),
+	},	/* r: 1, 7		d: 3^1, 3^1, 5^1 */
+	{
+		1, ACTION_GET, EXPECT_DELTA_SAME, EXPECT_ROOT_SAME,
+		EXPECT_STATS(4, ROOT(1, 2, 5), ROOT(7, 1, 1),
+				DELTA(3, 2), DELTA(5, 1)),
+	},	/* r: 1, 1, 7		d: 3^1, 3^1, 5^1 */
+	{
+		30, ACTION_GET, EXPECT_DELTA_SAME, EXPECT_ROOT_INC,
+		EXPECT_STATS(5, ROOT(1, 2, 5), ROOT(7, 1, 1), ROOT(30, 1, 1),
+				DELTA(3, 2), DELTA(5, 1)),
+	},	/* r: 1, 1, 7, 30	d: 3^1, 3^1, 5^1 */
+	{
+		8, ACTION_GET, EXPECT_DELTA_INC, EXPECT_ROOT_SAME,
+		EXPECT_STATS(6, ROOT(1, 2, 5), ROOT(7, 1, 2), ROOT(30, 1, 1),
+				DELTA(3, 2), DELTA(5, 1), DELTA(8, 1)),
+	},	/* r: 1, 1, 7, 30	d: 3^1, 3^1, 5^1, 8^7 */
+	{
+		8, ACTION_GET, EXPECT_DELTA_SAME, EXPECT_ROOT_SAME,
+		EXPECT_STATS(6, ROOT(1, 2, 5), ROOT(7, 1, 3), ROOT(30, 1, 1),
+				DELTA(3, 2), DELTA(8, 2), DELTA(5, 1)),
+	},	/* r: 1, 1, 7, 30	d: 3^1, 3^1, 5^1, 8^7, 8^7 */
+	{
+		3, ACTION_PUT, EXPECT_DELTA_SAME, EXPECT_ROOT_SAME,
+		EXPECT_STATS(6, ROOT(1, 2, 4), ROOT(7, 1, 3), ROOT(30, 1, 1),
+				DELTA(8, 2), DELTA(3, 1), DELTA(5, 1)),
+	},	/* r: 1, 1, 7, 30	d: 3^1, 5^1, 8^7, 8^7 */
+	{
+		3, ACTION_PUT, EXPECT_DELTA_DEC, EXPECT_ROOT_SAME,
+		EXPECT_STATS(5, ROOT(1, 2, 3), ROOT(7, 1, 3), ROOT(30, 1, 1),
+				DELTA(8, 2), DELTA(5, 1)),
+	},	/* r: 1, 1, 7, 30	d: 5^1, 8^7, 8^7 */
+	{
+		1, ACTION_PUT, EXPECT_DELTA_SAME, EXPECT_ROOT_SAME,
+		EXPECT_STATS(5, ROOT(7, 1, 3), ROOT(1, 1, 2), ROOT(30, 1, 1),
+				DELTA(8, 2), DELTA(5, 1)),
+	},	/* r: 1, 7, 30		d: 5^1, 8^7, 8^7 */
+	{
+		1, ACTION_PUT, EXPECT_DELTA_SAME, EXPECT_ROOT_SAME,
+		EXPECT_STATS(5, ROOT(7, 1, 3), ROOT(30, 1, 1), ROOT(1, 0, 1),
+				DELTA(8, 2), DELTA(5, 1)),
+	},	/* r: 7, 30		d: 5^1, 8^7, 8^7 */
+	{
+		5, ACTION_PUT, EXPECT_DELTA_DEC, EXPECT_ROOT_DEC,
+		EXPECT_STATS(3, ROOT(7, 1, 3), ROOT(30, 1, 1),
+				DELTA(8, 2)),
+	},	/* r: 7, 30		d: 8^7, 8^7 */
+	{
+		5, ACTION_GET, EXPECT_DELTA_SAME, EXPECT_ROOT_INC,
+		EXPECT_STATS(4, ROOT(7, 1, 3), ROOT(30, 1, 1), ROOT(5, 1, 1),
+				DELTA(8, 2)),
+	},	/* r: 7, 30, 5		d: 8^7, 8^7 */
+	{
+		6, ACTION_GET, EXPECT_DELTA_INC, EXPECT_ROOT_SAME,
+		EXPECT_STATS(5, ROOT(7, 1, 3), ROOT(5, 1, 2), ROOT(30, 1, 1),
+				DELTA(8, 2), DELTA(6, 1)),
+	},	/* r: 7, 30, 5		d: 8^7, 8^7, 6^5 */
+	{
+		8, ACTION_GET, EXPECT_DELTA_SAME, EXPECT_ROOT_SAME,
+		EXPECT_STATS(5, ROOT(7, 1, 4), ROOT(5, 1, 2), ROOT(30, 1, 1),
+				DELTA(8, 3), DELTA(6, 1)),
+	},	/* r: 7, 30, 5		d: 8^7, 8^7, 8^7, 6^5 */
+	{
+		8, ACTION_PUT, EXPECT_DELTA_SAME, EXPECT_ROOT_SAME,
+		EXPECT_STATS(5, ROOT(7, 1, 3), ROOT(5, 1, 2), ROOT(30, 1, 1),
+				DELTA(8, 2), DELTA(6, 1)),
+	},	/* r: 7, 30, 5		d: 8^7, 8^7, 6^5 */
+	{
+		8, ACTION_PUT, EXPECT_DELTA_SAME, EXPECT_ROOT_SAME,
+		EXPECT_STATS(5, ROOT(7, 1, 2), ROOT(5, 1, 2), ROOT(30, 1, 1),
+				DELTA(8, 1), DELTA(6, 1)),
+	},	/* r: 7, 30, 5		d: 8^7, 6^5 */
+	{
+		8, ACTION_PUT, EXPECT_DELTA_DEC, EXPECT_ROOT_SAME,
+		EXPECT_STATS(4, ROOT(5, 1, 2), ROOT(7, 1, 1), ROOT(30, 1, 1),
+				DELTA(6, 1)),
+	},	/* r: 7, 30, 5		d: 6^5 */
+	{
+		8, ACTION_GET, EXPECT_DELTA_INC, EXPECT_ROOT_SAME,
+		EXPECT_STATS(5, ROOT(5, 1, 3), ROOT(7, 1, 1), ROOT(30, 1, 1),
+				DELTA(6, 1), DELTA(8, 1)),
+	},	/* r: 7, 30, 5		d: 6^5, 8^5 */
+	{
+		7, ACTION_PUT, EXPECT_DELTA_SAME, EXPECT_ROOT_DEC,
+		EXPECT_STATS(4, ROOT(5, 1, 3), ROOT(30, 1, 1),
+				DELTA(6, 1), DELTA(8, 1)),
+	},	/* r: 30, 5		d: 6^5, 8^5 */
+	{
+		30, ACTION_PUT, EXPECT_DELTA_SAME, EXPECT_ROOT_DEC,
+		EXPECT_STATS(3, ROOT(5, 1, 3),
+				DELTA(6, 1), DELTA(8, 1)),
+	},	/* r: 5			d: 6^5, 8^5 */
+	{
+		5, ACTION_PUT, EXPECT_DELTA_SAME, EXPECT_ROOT_SAME,
+		EXPECT_STATS(3, ROOT(5, 0, 2),
+				DELTA(6, 1), DELTA(8, 1)),
+	},	/* r:			d: 6^5, 8^5 */
+	{
+		6, ACTION_PUT, EXPECT_DELTA_DEC, EXPECT_ROOT_SAME,
+		EXPECT_STATS(2, ROOT(5, 0, 1),
+				DELTA(8, 1)),
+	},	/* r:			d: 6^5 */
+	{
+		8, ACTION_PUT, EXPECT_DELTA_DEC, EXPECT_ROOT_DEC,
+		EXPECT_STATS(0, ),
+	},	/* r:			d: */
+};
+
+static int check_expect(struct world *world,
+			const struct action_item *action_item,
+			unsigned int orig_delta_count,
+			unsigned int orig_root_count)
+{
+	unsigned int key_id = action_item->key_id;
+
+	switch (action_item->expect_delta) {
+	case EXPECT_DELTA_SAME:
+		if (orig_delta_count != world->delta_count) {
+			pr_err("Key %u: Delta count changed while expected to remain the same.\n",
+			       key_id);
+			return -EINVAL;
+		}
+		break;
+	case EXPECT_DELTA_INC:
+		if (WARN_ON(action_item->action == ACTION_PUT))
+			return -EINVAL;
+		if (orig_delta_count + 1 != world->delta_count) {
+			pr_err("Key %u: Delta count was not incremented.\n",
+			       key_id);
+			return -EINVAL;
+		}
+		break;
+	case EXPECT_DELTA_DEC:
+		if (WARN_ON(action_item->action == ACTION_GET))
+			return -EINVAL;
+		if (orig_delta_count - 1 != world->delta_count) {
+			pr_err("Key %u: Delta count was not decremented.\n",
+			       key_id);
+			return -EINVAL;
+		}
+		break;
+	}
+
+	switch (action_item->expect_root) {
+	case EXPECT_ROOT_SAME:
+		if (orig_root_count != world->root_count) {
+			pr_err("Key %u: Root count changed while expected to remain the same.\n",
+			       key_id);
+			return -EINVAL;
+		}
+		break;
+	case EXPECT_ROOT_INC:
+		if (WARN_ON(action_item->action == ACTION_PUT))
+			return -EINVAL;
+		if (orig_root_count + 1 != world->root_count) {
+			pr_err("Key %u: Root count was not incremented.\n",
+			       key_id);
+			return -EINVAL;
+		}
+		break;
+	case EXPECT_ROOT_DEC:
+		if (WARN_ON(action_item->action == ACTION_GET))
+			return -EINVAL;
+		if (orig_root_count - 1 != world->root_count) {
+			pr_err("Key %u: Root count was not decremented.\n",
+			       key_id);
+			return -EINVAL;
+		}
+	}
+
+	return 0;
+}
+
+static unsigned int obj_to_key_id(struct objagg_obj *objagg_obj)
+{
+	const struct tokey *root_key;
+	const struct delta *delta;
+	unsigned int key_id;
+
+	root_key = objagg_obj_root_priv(objagg_obj);
+	key_id = root_key->id;
+	delta = objagg_obj_delta_priv(objagg_obj);
+	if (delta)
+		key_id += delta->key_id_diff;
+	return key_id;
+}
+
+static int
+check_expect_stats_nums(const struct objagg_obj_stats_info *stats_info,
+			const struct expect_stats_info *expect_stats_info,
+			const char **errmsg)
+{
+	if (stats_info->is_root != expect_stats_info->is_root) {
+		if (errmsg)
+			*errmsg = "Incorrect root/delta indication";
+		return -EINVAL;
+	}
+	if (stats_info->stats.user_count !=
+	    expect_stats_info->stats.user_count) {
+		if (errmsg)
+			*errmsg = "Incorrect user count";
+		return -EINVAL;
+	}
+	if (stats_info->stats.delta_user_count !=
+	    expect_stats_info->stats.delta_user_count) {
+		if (errmsg)
+			*errmsg = "Incorrect delta user count";
+		return -EINVAL;
+	}
+	return 0;
+}
+
+static int
+check_expect_stats_key_id(const struct objagg_obj_stats_info *stats_info,
+			  const struct expect_stats_info *expect_stats_info,
+			  const char **errmsg)
+{
+	if (obj_to_key_id(stats_info->objagg_obj) !=
+	    expect_stats_info->key_id) {
+		if (errmsg)
+			*errmsg = "incorrect key id";
+		return -EINVAL;
+	}
+	return 0;
+}
+
+static int check_expect_stats_neigh(const struct objagg_stats *stats,
+				    const struct expect_stats *expect_stats,
+				    int pos)
+{
+	int i;
+	int err;
+
+	for (i = pos - 1; i >= 0; i--) {
+		err = check_expect_stats_nums(&stats->stats_info[i],
+					      &expect_stats->info[pos], NULL);
+		if (err)
+			break;
+		err = check_expect_stats_key_id(&stats->stats_info[i],
+						&expect_stats->info[pos], NULL);
+		if (!err)
+			return 0;
+	}
+	for (i = pos + 1; i < stats->stats_info_count; i++) {
+		err = check_expect_stats_nums(&stats->stats_info[i],
+					      &expect_stats->info[pos], NULL);
+		if (err)
+			break;
+		err = check_expect_stats_key_id(&stats->stats_info[i],
+						&expect_stats->info[pos], NULL);
+		if (!err)
+			return 0;
+	}
+	return -EINVAL;
+}
+
+static int __check_expect_stats(const struct objagg_stats *stats,
+				const struct expect_stats *expect_stats,
+				const char **errmsg)
+{
+	int i;
+	int err;
+
+	if (stats->stats_info_count != expect_stats->info_count) {
+		*errmsg = "Unexpected object count";
+		return -EINVAL;
+	}
+
+	for (i = 0; i < stats->stats_info_count; i++) {
+		err = check_expect_stats_nums(&stats->stats_info[i],
+					      &expect_stats->info[i], errmsg);
+		if (err)
+			return err;
+		err = check_expect_stats_key_id(&stats->stats_info[i],
+						&expect_stats->info[i], errmsg);
+		if (err) {
+			/* It is possible that one of the neighbor stats with
+			 * same numbers have the correct key id, so check it
+			 */
+			err = check_expect_stats_neigh(stats, expect_stats, i);
+			if (err)
+				return err;
+		}
+	}
+	return 0;
+}
+
+static int check_expect_stats(struct objagg *objagg,
+			      const struct expect_stats *expect_stats,
+			      const char **errmsg)
+{
+	const struct objagg_stats *stats;
+	int err;
+
+	stats = objagg_stats_get(objagg);
+	if (IS_ERR(stats))
+		return PTR_ERR(stats);
+	err = __check_expect_stats(stats, expect_stats, errmsg);
+	objagg_stats_put(stats);
+	return err;
+}
+
+static int test_delta_action_item(struct world *world,
+				  struct objagg *objagg,
+				  const struct action_item *action_item,
+				  bool inverse)
+{
+	unsigned int orig_delta_count = world->delta_count;
+	unsigned int orig_root_count = world->root_count;
+	unsigned int key_id = action_item->key_id;
+	enum action action = action_item->action;
+	struct objagg_obj *objagg_obj;
+	const char *errmsg;
+	int err;
+
+	if (inverse)
+		action = action == ACTION_GET ? ACTION_PUT : ACTION_GET;
+
+	switch (action) {
+	case ACTION_GET:
+		objagg_obj = world_obj_get(world, objagg, key_id);
+		if (IS_ERR(objagg_obj))
+			return PTR_ERR(objagg_obj);
+		break;
+	case ACTION_PUT:
+		world_obj_put(world, objagg, key_id);
+		break;
+	}
+
+	if (inverse)
+		return 0;
+	err = check_expect(world, action_item,
+			   orig_delta_count, orig_root_count);
+	if (err)
+		goto errout;
+
+	err = check_expect_stats(objagg, &action_item->expect_stats, &errmsg);
+	if (err) {
+		pr_err("Key %u: Stats: %s\n", action_item->key_id, errmsg);
+		goto errout;
+	}
+
+	return 0;
+
+errout:
+	/* This can only happen when action is not inversed.
+	 * So in case of an error, cleanup by doing inverse action.
+	 */
+	test_delta_action_item(world, objagg, action_item, true);
+	return err;
+}
+
+static int test_delta(void)
+{
+	struct world world = {};
+	struct objagg *objagg;
+	int i;
+	int err;
+
+	objagg = objagg_create(&delta_ops, &world);
+	if (IS_ERR(objagg))
+		return PTR_ERR(objagg);
+
+	for (i = 0; i < ARRAY_SIZE(action_items); i++) {
+		err = test_delta_action_item(&world, objagg,
+					     &action_items[i], false);
+		if (err)
+			goto err_do_action_item;
+	}
+
+	objagg_destroy(objagg);
+	return 0;
+
+err_do_action_item:
+	for (i--; i >= 0; i--)
+		test_delta_action_item(&world, objagg, &action_items[i], true);
+
+	objagg_destroy(objagg);
+	return err;
+}
+
+static int __init test_objagg_init(void)
+{
+	int err;
+
+	err = test_nodelta();
+	if (err)
+		return err;
+	return test_delta();
+}
+
+static void __exit test_objagg_exit(void)
+{
+}
+
+module_init(test_objagg_init);
+module_exit(test_objagg_exit);
+MODULE_LICENSE("Dual BSD/GPL");
+MODULE_AUTHOR("Jiri Pirko <jiri@mellanox.com>");
+MODULE_DESCRIPTION("Test module for objagg");