// SPDX-License-Identifier: GPL-2.0
#include <linux/slab.h>
#include <linux/gfp.h>
#include <linux/string.h>
#include <linux/spinlock.h>
#include <linux/ceph/string_table.h>

static DEFINE_SPINLOCK(string_tree_lock);
static struct rb_root string_tree = RB_ROOT;

struct ceph_string *ceph_find_or_create_string(const char* str, size_t len)
{
        struct ceph_string *cs, *exist;
        struct rb_node **p, *parent;
        int ret;

        exist = NULL;
        spin_lock(&string_tree_lock);
        p = &string_tree.rb_node;
        while (*p) {
                exist = rb_entry(*p, struct ceph_string, node);
                ret = ceph_compare_string(exist, str, len);
                if (ret > 0)
                        p = &(*p)->rb_left;
                else if (ret < 0)
                        p = &(*p)->rb_right;
                else
                        break;
                exist = NULL;
        }
        if (exist && !kref_get_unless_zero(&exist->kref)) {
                rb_erase(&exist->node, &string_tree);
                RB_CLEAR_NODE(&exist->node);
                exist = NULL;
        }
        spin_unlock(&string_tree_lock);
        if (exist)
                return exist;

        cs = kmalloc(sizeof(*cs) + len + 1, GFP_NOFS);
        if (!cs)
                return NULL;

        kref_init(&cs->kref);
        cs->len = len;
        memcpy(cs->str, str, len);
        cs->str[len] = 0;

retry:
        exist = NULL;
        parent = NULL;
        p = &string_tree.rb_node;
        spin_lock(&string_tree_lock);
        while (*p) {
                parent = *p;
                exist = rb_entry(*p, struct ceph_string, node);
                ret = ceph_compare_string(exist, str, len);
                if (ret > 0)
                        p = &(*p)->rb_left;
                else if (ret < 0)
                        p = &(*p)->rb_right;
                else
                        break;
                exist = NULL;
        }
        ret = 0;
        if (!exist) {
                rb_link_node(&cs->node, parent, p);
                rb_insert_color(&cs->node, &string_tree);
        } else if (!kref_get_unless_zero(&exist->kref)) {
                rb_erase(&exist->node, &string_tree);
                RB_CLEAR_NODE(&exist->node);
                ret = -EAGAIN;
        }
        spin_unlock(&string_tree_lock);
        if (ret == -EAGAIN)
                goto retry;

        if (exist) {
                kfree(cs);
                cs = exist;
        }

        return cs;
}
EXPORT_SYMBOL(ceph_find_or_create_string);

void ceph_release_string(struct kref *ref)
{
        struct ceph_string *cs = container_of(ref, struct ceph_string, kref);

        spin_lock(&string_tree_lock);
        if (!RB_EMPTY_NODE(&cs->node)) {
                rb_erase(&cs->node, &string_tree);
                RB_CLEAR_NODE(&cs->node);
        }
        spin_unlock(&string_tree_lock);

        kfree_rcu(cs, rcu);
}
EXPORT_SYMBOL(ceph_release_string);

bool ceph_strings_empty(void)
{
        return RB_EMPTY_ROOT(&string_tree);
}