net/ceph/string_table.c

   1 #include <linux/slab.h>
   2 #include <linux/gfp.h>
   3 #include <linux/string.h>
   4 #include <linux/spinlock.h>
   5 #include <linux/ceph/string_table.h>
   6
   7 static DEFINE_SPINLOCK(string_tree_lock);
   8 static struct rb_root string_tree = RB_ROOT;
   9
  10 struct ceph_string *ceph_find_or_create_string(const char* str, size_t len)
  11 {
  12         struct ceph_string *cs, *exist;
  13         struct rb_node **p, *parent;
  14         int ret;
  15
  16         exist = NULL;
  17         spin_lock(&string_tree_lock);
  18         p = &string_tree.rb_node;
  19         while (*p) {
  20                 exist = rb_entry(*p, struct ceph_string, node);
  21                 ret = ceph_compare_string(exist, str, len);
  22                 if (ret > 0)
  23                         p = &(*p)->rb_left;
  24                 else if (ret < 0)
  25                         p = &(*p)->rb_right;
  26                 else
  27                         break;
  28                 exist = NULL;
  29         }
  30         if (exist && !kref_get_unless_zero(&exist->kref)) {
  31                 rb_erase(&exist->node, &string_tree);
  32                 RB_CLEAR_NODE(&exist->node);
  33                 exist = NULL;
  34         }
  35         spin_unlock(&string_tree_lock);
  36         if (exist)
  37                 return exist;
  38
  39         cs = kmalloc(sizeof(*cs) + len + 1, GFP_NOFS);
  40         if (!cs)
  41                 return NULL;
  42
  43         kref_init(&cs->kref);
  44         cs->len = len;
  45         memcpy(cs->str, str, len);
  46         cs->str[len] = 0;
  47
  48 retry:
  49         exist = NULL;
  50         parent = NULL;
  51         p = &string_tree.rb_node;
  52         spin_lock(&string_tree_lock);
  53         while (*p) {
  54                 parent = *p;
  55                 exist = rb_entry(*p, struct ceph_string, node);
  56                 ret = ceph_compare_string(exist, str, len);
  57                 if (ret > 0)
  58                         p = &(*p)->rb_left;
  59                 else if (ret < 0)
  60                         p = &(*p)->rb_right;
  61                 else
  62                         break;
  63                 exist = NULL;
  64         }
  65         ret = 0;
  66         if (!exist) {
  67                 rb_link_node(&cs->node, parent, p);
  68                 rb_insert_color(&cs->node, &string_tree);
  69         } else if (!kref_get_unless_zero(&exist->kref)) {
  70                 rb_erase(&exist->node, &string_tree);
  71                 RB_CLEAR_NODE(&exist->node);
  72                 ret = -EAGAIN;
  73         }
  74         spin_unlock(&string_tree_lock);
  75         if (ret == -EAGAIN)
  76                 goto retry;
  77
  78         if (exist) {
  79                 kfree(cs);
  80                 cs = exist;
  81         }
  82
  83         return cs;
  84 }
  85 EXPORT_SYMBOL(ceph_find_or_create_string);
  86
  87 void ceph_release_string(struct kref *ref)
  88 {
  89         struct ceph_string *cs = container_of(ref, struct ceph_string, kref);
  90
  91         spin_lock(&string_tree_lock);
  92         if (!RB_EMPTY_NODE(&cs->node)) {
  93                 rb_erase(&cs->node, &string_tree);
  94                 RB_CLEAR_NODE(&cs->node);
  95         }
  96         spin_unlock(&string_tree_lock);
  97
  98         kfree_rcu(cs, rcu);
  99 }
 100 EXPORT_SYMBOL(ceph_release_string);
 101
 102 bool ceph_strings_empty(void)
 103 {
 104         return RB_EMPTY_ROOT(&string_tree);
 105 }