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for (i = 0; i < nr; i++) {
struct buffer_head *bh = bhs[i];
submit_bh(rw, bh);
struct bio *bio; // 使用bh来构造bio (block input/output)
submit_bio(rw, bio);
// 通用的构造请求: 使用bio来构造请求(request)
generic_make_request(bio);
__generic_make_request(bio);
request_queue_t *q = bdev_get_queue(bio->bi_bdev); // 找到队列
?
// 调用队列的"构造请求函数"
ret = q->make_request_fn(q, bio);
// 默认的函数是__make_request
__make_request
// 先尝试合并
elv_merge(q, &req, bio);
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// 如果合并不成，使用bio构造请求
init_request_from_bio(req, bio);
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// 把请求放入队列
add_request(q, req);
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// 执行队列
__generic_unplug_device(q);
// 调用队列的"处理函数"
q->request_fn(q);
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驱动程序
1 /*
2 * 块设备驱动程序：内存用作磁盘
3 * 参考：
4 * .\linux-2.6.22.6\drivers\block\xd.c
5 * .\linux-2.6.22.6\drivers\block\z2ram.c
6 */
7
8 #include <linux/module.h>
9 #include <linux/errno.h>
10 #include <linux/interrupt.h>
11 #include <linux/mm.h>
12 #include <linux/fs.h>
13 #include <linux/kernel.h>
14 #include <linux/timer.h>
15 #include <linux/genhd.h>
16 #include <linux/hdreg.h>
17 #include <linux/ioport.h>
18 #include <linux/init.h>
19 #include <linux/wait.h>
20 #include <linux/blkdev.h>
21 #include <linux/blkpg.h>
22 #include <linux/delay.h>
23 #include <linux/io.h>
24
25 #include <asm/system.h>
26 #include <asm/uaccess.h>
27 #include <asm/dma.h>
28
29 /* 1M */
30 #define RAMBlock_SIZE (1024*1024)
31
32 static unsigned char *ramBlock_buf;
33
34 static struct gendisk *ramBlock_disk;
35 static request_queue_t *ramBlock_queue;
36
37 static int major;
38
39 /* 自旋锁 */
40 static DEFINE_SPINLOCK(ramBlock_lock);
41
42 //为了使用fdisk分区工具，假装自己是磁盘，
43 //有2个面，32个环，RAMBlock_SIZE/heads/cylinders/512个扇区
44 //容量：RAMBlock_SIZE = heads*cylinders*sectors*512
45 //1 disk ????????????????= 2 heads
46 //1 heads ???????? ????????= 32 cylinders
47 //1 cylinders????????= RAMBlock_SIZE/heads/cylinders/512 sectors = 32 sectors
48 static int ramBlock_getgeo(struct block_device *bdev, struct hd_geometry *geo)
49 {
50 ????????geo->heads ????????????????= 2;
51 ????????geo->cylinders ????????= 32;
52 ????????geo->sectors ????????= 32;
53 ????????return 0;
54 }
55
56
57 static struct block_device_operations ramBlock_fops = {
58 ????????.owner = THIS_MODULE,
59 ????????.getgeo = ramBlock_getgeo,
60 };
61
62 static void do_ramBlock_request(request_queue_t *q)
63 {
64 ????????static int r_cnt = 0;
65 ????????static int w_cnt = 0;
66 ????????struct request *req;
67
68 ????????//以电梯调度算法，取出下一个请求
69 ????????while ((req = elv_next_request(q)) != NULL) {
70 ????????????????/* 6 读写 */
71 ????????????????//数据传输三要素：源、目的、长度
72 ????????????????//源/目的????????(要操作第几个扇区)
73 ????????????????unsigned long offset = req->sector << 9;????????//<< 9 相当于 * 512
74
75 ????????????????//目的/源????????(读、写缓冲区)
76 ????????????????//req->buffer
77
78 ????????????????//长度????????(缓冲区长度(sector的倍数))
79 ????????????????unsigned long len = req->current_nr_sectors << 9;
80
81 ????????????????//读数据
82 ????????????????if (rq_data_dir(req) == READ)
83 ????????????????{
84 ????????????????????????printk("do_ramblock_request read %d\n", ++r_cnt);
85 ????????????????????????memcpy(req->buffer, ramBlock_buf+offset, len);
86 ????????????????}
87 ????????????????else {????????//写数据
88 ????????????????????????printk("do_ramblock_request read %d\n", ++r_cnt);
89 ????????????????????????memcpy(ramBlock_buf+offset, req->buffer, len);
90 ????????????????}
91
92 ????????????????/******** 6 end ********/
93 ????????????????end_request(req, 1);
94 ????????}
95 ????????return;
96 }
97
98
99 /* 1 出入口函数 */
100 static int ramBlock_init(void)
101 {
102 ????????/* 2 分配一个gendisk结构体 */
103 ????????ramBlock_disk = alloc_disk(16); //次设备号个数：分区个数+1
104 ????????/******** 2 end ********/
105
106 ????????/* 3 设置 */
107 ????????//3.1 分配/设置队列（提供读写功能）
108 ????????ramBlock_queue = blk_init_queue(do_ramBlock_request, &ramBlock_lock);????????
109 ????????
110 ????????//3.2 设置其他属性：如容量
111 ????????ramBlock_disk->queue????????????????= ramBlock_queue;
112
113 ????????major = register_blkdev(0, "ramBlock_disk");????????????????//cat /proc/devices
114 ????????ramBlock_disk->major????????????????= major;
115
116 ????????ramBlock_disk->first_minor????????= 0;
117 ????????sprintf(ramBlock_disk->disk_name, "ramBlock_disk");
118 ????????ramBlock_disk->fops????????????????????????= &ramBlock_fops;
119 ????????set_capacity(ramBlock_disk, RAMBlock_SIZE/512);????????????????//第二个参数表示扇区个数，相对于内核而言，一个扇区为512字节
120 ????????/******** 3 end ********/
121
122 ????????/*
123 ???????? * 除了第4、第6、及以后的操作外，实际已经完成了块设备驱动框架的编写；????????
124 ???????? */
125
126 ????????/* 4 硬件相关的操作 */
127 ????????ramBlock_buf = kzalloc(RAMBlock_SIZE, GFP_KERNEL);
128 ????????/******** 4 end ********/
129
130 ????????/* 5 注册 */
131 ????????add_disk(ramBlock_disk);
132 ????????/******** 5 end ********/
133 ????????return 0;
134 }
135
136
137 static void ramBlock_exit(void)
138 {
139 ????????unregister_blkdev(major, "ramBlock_disk");
140 ????????del_gendisk(ramBlock_disk);
141 ????????put_disk(ramBlock_disk);
142 ????????blk_cleanup_queue(ramBlock_queue);
143 ????????kfree(ramBlock_buf);
144 ????????return;
145 }
146
147 module_init(ramBlock_init);
148 module_exit(ramBlock_exit);
149 MODULE_LICENSE("GPL");
150 /******** 1 end ********/
? ?
? ?
调试
1. insmod ramBlock.ko
? ?
2. 格式化:
mkdosfs /dev/ramBlock_disk
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3. 挂接:
mount /dev/ramBlock_disk /tmp
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4. 读写文件:
cd /tmp
vi 1.txt
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（分区：fdisk /dev/ramBlock_disk）
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5. 卸载
cd /
umount /tmp/
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6. 把/dev/ramBlock_disk目录下的文件，以镜像的形式保存到/mnt下
cat /dev/ramBlock_disk > /mnt/ramBlock_disk.bin
? ?
7. 在PC上查看ramBlock_disk.bin（把ramBlock_disk.bin作为回环设备挂接到/mnt）
sudo mount -o loop ramBlock_disk.bin /mn
??
原文：https://www.cnblogs.com/lilto/p/11878255.html