Quelle string_table.c Sprache: C

// 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);
}

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