我现正在linux kernel 4.4.1中新增一个类sysfs文件系统，取名jefffs,
大名鼎鼎的kobject，自然也被我山寨成了jobject :)
内核中的小知识点、数据结构什么的当然也非常多，需要在开发项目的时候不断总结运用才能融会贯通，现记录一个昨天用到的红黑树。如果要知道原理上这个网站，直接动态观看： http://47.52.149.59/jeff_struction/visualization/RedBlack.html
现直接贴上红黑树测试代码:

  1/*jefffs.h*/
  2
  3#ifndef __JEFFFS_INTERNAL_H
  4#define __JEFFFS_INTERNAL_H
  5
  6#include <linux/jefffs.h>
  7extern int test_rb(void);
  8
  9struct jeff_node{
 10    atomic_t count;
 11    const char *name;
 12    struct rb_node rb;
 13    unsigned int ino;
 14};
 15#endif
 16
 17
 18/*************************************/
 19/* rb.c*/
 20#include <linux/rbtree.h>
 21#include <linux/slab.h>
 22#include "jefffs.h"
 23
 24#define rb_to_jn(X) rb_entry((X),struct jeff_node,rb)
 25
 26int jeff_rb_insert(struct rb_root *root,struct jeff_node *data)
 27{
 28    struct rb_node **node = &(root->rb_node);
 29    struct rb_node *parent = NULL;
 30
 31    while(*node){
 32        struct jeff_node *pos = rb_to_jn(*node);
 33
 34        parent = *node;
 35        if(data->ino < pos->ino)
 36            node = &(*node)->rb_left;
 37        else if(data->ino > pos->ino)
 38            node = &(*node)->rb_right;
 39        else 
 40            return -1;
 41    }
 42    rb_link_node(&data->rb,parent,node);
 43    rb_insert_color(&data->rb,root);
 44    return 0;
 45}
 46
 47void jeff_print_rbtree(struct rb_root *tree)
 48{
 49    struct rb_node *node;
 50
 51    for(node = rb_first(tree);node;node = rb_next(node))
 52        printk("%d ",(rb_to_jn(node))->ino);
 53
 54    printk("%s (%d)\n",__func__,__LINE__);
 55}
 56
 57
 58struct jeff_node *jeff_rb_search(struct rb_root *root,int ino)
 59{
 60    struct rb_node *node = root->rb_node;
 61
 62    while(node){
 63        struct jeff_node *pos = rb_to_jn(node);
 64
 65        if(ino < pos->ino)
 66            node = node->rb_left;
 67        else if(ino > pos->ino)
 68            node = node->rb_right;
 69        else
 70            return pos;
 71    }
 72    return NULL;
 73}
 74
 75int  jeff_rb_delete(struct rb_root *root,int ino)
 76{
 77    struct jeff_node *pos = jeff_rb_search(root,ino);
 78
 79    if(!pos){
 80        printk("not found jeff_node,can not delete\n");
 81        return -1;
 82    }
 83    rb_erase(&pos->rb,root);
 84
 85    return 0;
 86}
 87
 88
 89
 90int test_rb(void)
 91{
 92
 93    struct rb_root root = RB_ROOT;
 94    struct jeff_node *search = NULL;
 95    int i;
 96    int retval;
 97    char *error;
 98
 99#define MAX_TEST_NODE (10)
100    struct jeff_node *node[MAX_TEST_NODE];
101
102    for(i = 0;i < MAX_TEST_NODE;i++){
103        node[i] = kmalloc(sizeof(struct jeff_node),GFP_KERNEL); 
104        if(!node[i]){
105            error = "no enough memory\n";
106            goto error;
107        }
108        node[i]->ino = i;
109        if(i == 3)
110            node[i]->name = "9527";
111        retval = jeff_rb_insert(&root,node[i]);
112        if(retval)
113            goto err_val;
114    }
115
116    jeff_rb_delete(&root,5);
117    jeff_print_rbtree(&root);
118    search = jeff_rb_search(&root,3);
119    if(!search){
120        printk("jeff search fail %s(%d)\n",__func__,__LINE__);
121        return -1;
122    }
123    printk("searched name is %s\n",search->name);
124
125    return 0;
126err_val:
127    return -1;
128error:
129    printk("jeff_node %s %s(%d)\n",error,__func__,__LINE__);
130    return -ENOMEM;
131}

以上代码主函数是test_rb,由其他函数直接调用执行，运行结果如下：