Merge tag 'tty-5.9-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty

[mirror_ubuntu-hirsute-kernel.git] / lib / objagg.c

// 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;
        size_t alloc_size;
        int i, j;

        graph = kzalloc(sizeof(*graph), GFP_KERNEL);
        if (!graph)
                return NULL;

        graph->nodes = kcalloc(nodes_count, sizeof(*graph->nodes), GFP_KERNEL);
        if (!graph->nodes)
                goto err_nodes_alloc;
        graph->nodes_count = nodes_count;

        alloc_size = BITS_TO_LONGS(nodes_count * nodes_count) *
                     sizeof(unsigned long);
        graph->edges = kzalloc(alloc_size, GFP_KERNEL);
        if (!graph->edges)
                goto err_edges_alloc;

        i = 0;
        list_for_each_entry(objagg_obj, &objagg->obj_list, list) {
                node = &graph->nodes[i++];
                node->objagg_obj = objagg_obj;
        }

        /* Assemble a temporary graph. Insert edge X->Y in case Y can be
         * in delta of X.
         */
        for (i = 0; i < nodes_count; i++) {
                for (j = 0; j < nodes_count; j++) {
                        if (i == j)
                                continue;
                        pnode = &graph->nodes[i];
                        node = &graph->nodes[j];
                        if (objagg->ops->delta_check(objagg->priv,
                                                     pnode->objagg_obj->obj,
                                                     node->objagg_obj->obj)) {
                                objagg_tmp_graph_edge_set(graph, i, j);

                        }
                }
        }
        return graph;

err_edges_alloc:
        kfree(graph->nodes);
err_nodes_alloc:
        kfree(graph);
        return NULL;
}

static void objagg_tmp_graph_destroy(struct objagg_tmp_graph *graph)
{
        kfree(graph->edges);
        kfree(graph->nodes);
        kfree(graph);
}

static int
objagg_opt_simple_greedy_fillup_hints(struct objagg_hints *objagg_hints,
                                      struct objagg *objagg)
{
        struct objagg_hints_node *hnode, *parent_hnode;
        struct objagg_tmp_graph *graph;
        struct objagg_tmp_node *node;
        int index;
        int j;
        int err;

        graph = objagg_tmp_graph_create(objagg);
        if (!graph)
                return -ENOMEM;

        /* Find the nodes from the ones that can accommodate most users
         * and cross them out of the graph. Save them to the hint list.
         */
        while ((index = objagg_tmp_graph_node_max_weight(graph)) != -1) {
                node = &graph->nodes[index];
                node->crossed_out = true;
                hnode = objagg_hints_node_create(objagg_hints,
                                                 node->objagg_obj,
                                                 objagg->ops->obj_size,
                                                 NULL);
                if (IS_ERR(hnode)) {
                        err = PTR_ERR(hnode);
                        goto out;
                }
                parent_hnode = hnode;
                for (j = 0; j < graph->nodes_count; j++) {
                        if (!objagg_tmp_graph_is_edge(graph, index, j))
                                continue;
                        node = &graph->nodes[j];
                        if (node->crossed_out)
                                continue;
                        node->crossed_out = true;
                        hnode = objagg_hints_node_create(objagg_hints,
                                                         node->objagg_obj,
                                                         objagg->ops->obj_size,
                                                         parent_hnode);
                        if (IS_ERR(hnode)) {
                                err = PTR_ERR(hnode);
                                goto out;
                        }
                }
        }

        err = 0;
out:
        objagg_tmp_graph_destroy(graph);
        return err;
}

struct objagg_opt_algo {
        int (*fillup_hints)(struct objagg_hints *objagg_hints,
                            struct objagg *objagg);
};

static const struct objagg_opt_algo objagg_opt_simple_greedy = {
        .fillup_hints = objagg_opt_simple_greedy_fillup_hints,
};


static const struct objagg_opt_algo *objagg_opt_algos[] = {
        [OBJAGG_OPT_ALGO_SIMPLE_GREEDY] = &objagg_opt_simple_greedy,
};

static int objagg_hints_obj_cmp(struct rhashtable_compare_arg *arg,
                                const void *obj)
{
        struct rhashtable *ht = arg->ht;
        struct objagg_hints *objagg_hints =
                        container_of(ht, struct objagg_hints, node_ht);
        const struct objagg_ops *ops = objagg_hints->ops;
        const char *ptr = obj;

        ptr += ht->p.key_offset;
        return ops->hints_obj_cmp ? ops->hints_obj_cmp(ptr, arg->key) :
                                    memcmp(ptr, arg->key, ht->p.key_len);
}

/**
 * objagg_hints_get - obtains hints instance
 * @objagg:             objagg instance
 * @opt_algo_type:      type of hints finding algorithm
 *
 * Note: all locking must be provided by the caller.
 *
 * According to the algo type, the existing objects of objagg instance
 * are going to be went-through to assemble an optimal tree. We call this
 * tree hints. These hints can be later on used for creation of
 * a new objagg instance. There, the future object creations are going
 * to be consulted with these hints in order to find out, where exactly
 * the new object should be put as a root or delta.
 *
 * Returns a pointer to hints instance in case of success,
 * otherwise it returns pointer error using ERR_PTR macro.
 */
struct objagg_hints *objagg_hints_get(struct objagg *objagg,
                                      enum objagg_opt_algo_type opt_algo_type)
{
        const struct objagg_opt_algo *algo = objagg_opt_algos[opt_algo_type];
        struct objagg_hints *objagg_hints;
        int err;

        objagg_hints = kzalloc(sizeof(*objagg_hints), GFP_KERNEL);
        if (!objagg_hints)
                return ERR_PTR(-ENOMEM);

        objagg_hints->ops = objagg->ops;
        objagg_hints->refcount = 1;

        INIT_LIST_HEAD(&objagg_hints->node_list);

        objagg_hints->ht_params.key_len = objagg->ops->obj_size;
        objagg_hints->ht_params.key_offset =
                                offsetof(struct objagg_hints_node, obj);
        objagg_hints->ht_params.head_offset =
                                offsetof(struct objagg_hints_node, ht_node);
        objagg_hints->ht_params.obj_cmpfn = objagg_hints_obj_cmp;

        err = rhashtable_init(&objagg_hints->node_ht, &objagg_hints->ht_params);
        if (err)
                goto err_rhashtable_init;

        err = algo->fillup_hints(objagg_hints, objagg);
        if (err)
                goto err_fillup_hints;

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

        return objagg_hints;

err_node_count_check:
err_fillup_hints:
        objagg_hints_flush(objagg_hints);
        rhashtable_destroy(&objagg_hints->node_ht);
err_rhashtable_init:
        kfree(objagg_hints);
        return ERR_PTR(err);
}
EXPORT_SYMBOL(objagg_hints_get);

/**
 * objagg_hints_put - puts hints instance
 * @objagg_hints:       objagg hints instance
 *
 * Note: all locking must be provided by the caller.
 */
void objagg_hints_put(struct objagg_hints *objagg_hints)
{
        if (--objagg_hints->refcount)
                return;
        objagg_hints_flush(objagg_hints);
        rhashtable_destroy(&objagg_hints->node_ht);
        kfree(objagg_hints);
}
EXPORT_SYMBOL(objagg_hints_put);

/**
 * objagg_hints_stats_get - obtains stats of the hints instance
 * @objagg_hints:       hints instance
 *
 * Note: all locking must be provided by the caller.
 *
 * The returned structure contains statistics of all objects
 * currently in use, ordered by following rules:
 * 1) Root objects are always on lower indexes than the rest.
 * 2) Objects with higher delta user count are always on lower
 *    indexes.
 * 3) In case multiple objects have the same delta user count,
 *    the objects are ordered by user count.
 *
 * Returns a pointer to stats instance in case of success,
 * otherwise it returns pointer error using ERR_PTR macro.
 */
const struct objagg_stats *
objagg_hints_stats_get(struct objagg_hints *objagg_hints)
{
        struct objagg_stats *objagg_stats;
        struct objagg_hints_node *hnode;
        int i;

        objagg_stats = kzalloc(struct_size(objagg_stats, stats_info,
                                           objagg_hints->node_count),
                               GFP_KERNEL);
        if (!objagg_stats)
                return ERR_PTR(-ENOMEM);

        i = 0;
        list_for_each_entry(hnode, &objagg_hints->node_list, list) {
                memcpy(&objagg_stats->stats_info[i], &hnode->stats_info,
                       sizeof(objagg_stats->stats_info[0]));
                if (objagg_stats->stats_info[i].is_root)
                        objagg_stats->root_count++;
                i++;
        }
        objagg_stats->stats_info_count = i;

        sort(objagg_stats->stats_info, objagg_stats->stats_info_count,
             sizeof(struct objagg_obj_stats_info),
             objagg_stats_info_sort_cmp_func, NULL);

        return objagg_stats;
}
EXPORT_SYMBOL(objagg_hints_stats_get);

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