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>

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");