// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2011 STRATO AG
 * written by Arne Jansen <sensille@gmx.net>
 */

#include <linux/slab.h>
#include "messages.h"
#include "ulist.h"

/*
 * ulist is a generic data structure to hold a collection of unique u64
 * values. The only operations it supports is adding to the list and
 * enumerating it.
 * It is possible to store an auxiliary value along with the key.
 *
 * A sample usage for ulists is the enumeration of directed graphs without
 * visiting a node twice. The pseudo-code could look like this:
 *
 * ulist = ulist_alloc();
 * ulist_add(ulist, root);
 * ULIST_ITER_INIT(&uiter);
 *
 * while ((elem = ulist_next(ulist, &uiter)) {
 *      for (all child nodes n in elem)
 *              ulist_add(ulist, n);
 *      do something useful with the node;
 * }
 * ulist_free(ulist);
 *
 * This assumes the graph nodes are addressable by u64. This stems from the
 * usage for tree enumeration in btrfs, where the logical addresses are
 * 64 bit.
 *
 * It is also useful for tree enumeration which could be done elegantly
 * recursively, but is not possible due to kernel stack limitations. The
 * loop would be similar to the above.
 */

/*
 * Freshly initialize a ulist.
 *
 * @ulist:      the ulist to initialize
 *
 * Note: don't use this function to init an already used ulist, use
 * ulist_reinit instead.
 */
void ulist_init(struct ulist *ulist)
{
        INIT_LIST_HEAD(&ulist->nodes);
        ulist->root = RB_ROOT;
        ulist->nnodes = 0;
        ulist->prealloc = NULL;
}

/*
 * Free up additionally allocated memory for the ulist.
 *
 * @ulist:      the ulist from which to free the additional memory
 *
 * This is useful in cases where the base 'struct ulist' has been statically
 * allocated.
 */
void ulist_release(struct ulist *ulist)
{
        struct ulist_node *node;
        struct ulist_node *next;

        list_for_each_entry_safe(node, next, &ulist->nodes, list) {
                kfree(node);
        }
        kfree(ulist->prealloc);
        ulist->prealloc = NULL;
        ulist->root = RB_ROOT;
        INIT_LIST_HEAD(&ulist->nodes);
}

/*
 * Prepare a ulist for reuse.
 *
 * @ulist:      ulist to be reused
 *
 * Free up all additional memory allocated for the list elements and reinit
 * the ulist.
 */
void ulist_reinit(struct ulist *ulist)
{
        ulist_release(ulist);
        ulist_init(ulist);
}

/*
 * Dynamically allocate a ulist.
 *
 * @gfp_mask:   allocation flags to for base allocation
 *
 * The allocated ulist will be returned in an initialized state.
 */
struct ulist *ulist_alloc(gfp_t gfp_mask)
{
        struct ulist *ulist = kmalloc_obj(*ulist, gfp_mask);

        if (!ulist)
                return NULL;

        ulist_init(ulist);

        return ulist;
}

void ulist_prealloc(struct ulist *ulist, gfp_t gfp_mask)
{
        if (!ulist->prealloc)
                ulist->prealloc = kzalloc_obj(*ulist->prealloc, gfp_mask);
}

/*
 * Free dynamically allocated ulist.
 *
 * @ulist:      ulist to free
 *
 * It is not necessary to call ulist_release before.
 */
void ulist_free(struct ulist *ulist)
{
        if (!ulist)
                return;
        ulist_release(ulist);
        kfree(ulist);
}

static int ulist_node_val_key_cmp(const void *key, const struct rb_node *node)
{
        const u64 *val = key;
        const struct ulist_node *unode = rb_entry(node, struct ulist_node, rb_node);

        if (unode->val < *val)
                return 1;
        else if (unode->val > *val)
                return -1;

        return 0;
}

static struct ulist_node *ulist_rbtree_search(struct ulist *ulist, u64 val)
{
        struct rb_node *node;

        node = rb_find(&val, &ulist->root, ulist_node_val_key_cmp);
        return rb_entry_safe(node, struct ulist_node, rb_node);
}

static void ulist_rbtree_erase(struct ulist *ulist, struct ulist_node *node)
{
        rb_erase(&node->rb_node, &ulist->root);
        list_del(&node->list);
        kfree(node);
        BUG_ON(ulist->nnodes == 0);
        ulist->nnodes--;
}

static int ulist_node_val_cmp(struct rb_node *new, const struct rb_node *existing)
{
        const struct ulist_node *unode = rb_entry(new, struct ulist_node, rb_node);

        return ulist_node_val_key_cmp(&unode->val, existing);
}

static int ulist_rbtree_insert(struct ulist *ulist, struct ulist_node *ins)
{
        struct rb_node *node;

        node = rb_find_add(&ins->rb_node, &ulist->root, ulist_node_val_cmp);
        if (node)
                return -EEXIST;
        return 0;
}

/*
 * Add an element to the ulist.
 *
 * @ulist:      ulist to add the element to
 * @val:        value to add to ulist
 * @aux:        auxiliary value to store along with val
 * @gfp_mask:   flags to use for allocation
 *
 * Note: locking must be provided by the caller. In case of rwlocks write
 *       locking is needed
 *
 * Add an element to a ulist. The @val will only be added if it doesn't
 * already exist. If it is added, the auxiliary value @aux is stored along with
 * it. In case @val already exists in the ulist, @aux is ignored, even if
 * it differs from the already stored value.
 *
 * ulist_add returns 0 if @val already exists in ulist and 1 if @val has been
 * inserted.
 * In case of allocation failure -ENOMEM is returned and the ulist stays
 * unaltered.
 */
int ulist_add(struct ulist *ulist, u64 val, u64 aux, gfp_t gfp_mask)
{
        return ulist_add_merge(ulist, val, aux, NULL, gfp_mask);
}

int ulist_add_merge(struct ulist *ulist, u64 val, u64 aux,
                    u64 *old_aux, gfp_t gfp_mask)
{
        int ret;
        struct ulist_node *node;

        node = ulist_rbtree_search(ulist, val);
        if (node) {
                if (old_aux)
                        *old_aux = node->aux;
                return 0;
        }

        if (ulist->prealloc) {
                node = ulist->prealloc;
                ulist->prealloc = NULL;
        } else {
                node = kmalloc_obj(*node, gfp_mask);
                if (!node)
                        return -ENOMEM;
        }

        node->val = val;
        node->aux = aux;

        ret = ulist_rbtree_insert(ulist, node);
        ASSERT(!ret);
        list_add_tail(&node->list, &ulist->nodes);
        ulist->nnodes++;

        return 1;
}

/*
 * Delete one node from ulist.
 *
 * @ulist:      ulist to remove node from
 * @val:        value to delete
 * @aux:        aux to delete
 *
 * The deletion will only be done when *BOTH* val and aux matches.
 * Return 0 for successful delete.
 * Return > 0 for not found.
 */
int ulist_del(struct ulist *ulist, u64 val, u64 aux)
{
        struct ulist_node *node;

        node = ulist_rbtree_search(ulist, val);
        /* Not found */
        if (!node)
                return 1;

        if (node->aux != aux)
                return 1;

        /* Found and delete */
        ulist_rbtree_erase(ulist, node);
        return 0;
}

/*
 * Iterate ulist.
 *
 * @ulist:      ulist to iterate
 * @uiter:      iterator variable, initialized with ULIST_ITER_INIT(&iterator)
 *
 * Note: locking must be provided by the caller. In case of rwlocks only read
 *       locking is needed
 *
 * This function is used to iterate an ulist.
 * It returns the next element from the ulist or %NULL when the
 * end is reached. No guarantee is made with respect to the order in which
 * the elements are returned. They might neither be returned in order of
 * addition nor in ascending order.
 * It is allowed to call ulist_add during an enumeration. Newly added items
 * are guaranteed to show up in the running enumeration.
 */
struct ulist_node *ulist_next(const struct ulist *ulist, struct ulist_iterator *uiter)
{
        struct ulist_node *node;

        if (list_empty(&ulist->nodes))
                return NULL;
        if (uiter->cur_list && uiter->cur_list->next == &ulist->nodes)
                return NULL;
        if (uiter->cur_list) {
                uiter->cur_list = uiter->cur_list->next;
        } else {
                uiter->cur_list = ulist->nodes.next;
        }
        node = list_entry(uiter->cur_list, struct ulist_node, list);
        return node;
}