// 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);}