求助：内存块设备分区提示无法读取。

c04n05

http://bbs.chinaunix.net/thread-2017377-2-1.html  看的这个帖子，试验了下代码。如下：

1. #include <linux/kernel.h>
   
2. #include <linux/init.h>
   
3. #include <linux/module.h>
   
4. #include <linux/fs.h>
   
5. #include <linux/blkdev.h>
   
6. #include <linux/genhd.h>
   
7. #include <linux/version.h>
   
8. 
   
9. #define SIMP_BLKDEV_DISKNAME           "simp_blkdev"
   
10. #define SIMP_BLKDEV_DEVICEMAJOR        COMPAQ_SMART2_MAJOR
    
11. #define SIMP_BLKDEV_BYTES              (16*1024*1024)//16MB
    
12. #define SIMP_BLKDEV_MAXPARTITIONS      (64)
    
13. 
    
14. MODULE_LICENSE("GPL");
    
15. 
    
16. static struct gendisk *simp_blkdev_disk;
    
17. static struct request_queue *simp_blkdev_queue;
    
18. 
    
19. unsigned char simp_blkdev_data[SIMP_BLKDEV_BYTES];
    
20. 
    
21. struct block_device_operations simp_blkdev_fops = {
    
22.     .owner = THIS_MODULE,
    
23. };
    
24. 
    
25. static int simp_blkdev_make_request(struct request_queue *q, struct bio *bio)
    
26. {
    
27.     struct bio_vec *bvec;
    
28.     int i;
    
29.     void *dsk_mem;
    
30. 
    
31.     if ((bio->bi_sector << 9) + bio->bi_size > SIMP_BLKDEV_BYTES)
    
32.     {
    
33.         printk(KERN_ERR SIMP_BLKDEV_DISKNAME ":bad request:block=%llu, count=%u\n", (unsigned long long)bio->bi_sector, bio->bi_size);
    
34.         
    
35. #if LINUX_VERSION_CODE < KERNEL_VERSION(2, 6, 24)
    
36.         bio_endio(bio, 0, -EIO);
    
37. #else
    
38.         bio_endio(bio, -EIO);
    
39. #endif
    
40.         return 0;
    
41.     }
    
42. 
    
43.     dsk_mem = simp_blkdev_data + (bio->bi_sector << 9);
    
44.    
    
45.     bio_for_each_segment(bvec, bio, i)
    
46.     {
    
47.         void *iovec_mem;
    
48.         
    
49.         switch (bio_rw(bio))
    
50.         {
    
51.         case READ:
    
52.         case READA:
    
53.             iovec_mem = kmap(bvec->bv_page) + bvec->bv_offset;
    
54.             memcpy(iovec_mem, dsk_mem, bvec->bv_len);
    
55.             kunmap(bvec->bv_page);
    
56.             break;
    
57.         
    
58.         case WRITE:
    
59.             iovec_mem = kmap(bvec->bv_page) + bvec->bv_offset;
    
60.             memcpy(dsk_mem, iovec_mem, bvec->bv_len);
    
61.             kunmap(bvec->bv_page);
    
62. 
    
63.         default:
    
64.             printk(KERN_ERR SIMP_BLKDEV_DISKNAME ":unknown value of bio_rw:%lu\n", bio_rw(bio));
    
65. #if LINUX_VERSION_CODE < KERNEL_VERSION(2, 6, 24)
    
66.             bio_endio(bio, 0, -EIO);
    
67. #else
    
68.             bio_endio(bio, -EIO);
    
69. #endif
    
70.             return 0;
    
71.         }
    
72.         dsk_mem += bvec->bv_len;
    
73.     }
    
74. #if LINUX_VERSION_CODE < KERNEL_VERSION(2, 6, 24)
    
75.     bio_endio(bio, 0, -EIO);
    
76. #else
    
77.     bio_endio(bio, -EIO);
    
78. #endif
    
79.     return 0;
    
80. }
    
81. 
    
82. static int __init simp_blkdev_init(void)
    
83. {
    
84.     int ret = 0;
    
85. 
    
86.     simp_blkdev_disk = alloc_disk(SIMP_BLKDEV_MAXPARTITIONS);
    
87.     if (!simp_blkdev_disk)
    
88.     {
    
89.         ret = -ENOMEM;
    
90.         goto err_alloc_disk;
    
91.     }
    
92. 
    
93.     simp_blkdev_queue = blk_alloc_queue(GFP_KERNEL);
    
94.     if (!simp_blkdev_queue)
    
95.     {
    
96.         ret = -ENOMEM;
    
97.         goto err_init_queue;
    
98.     }   
    
99. 
    
100.     blk_queue_make_request(simp_blkdev_queue, simp_blkdev_make_request);
     
101. 
     
102.     strcpy(simp_blkdev_disk->disk_name, SIMP_BLKDEV_DISKNAME);
     
103.     simp_blkdev_disk->major = SIMP_BLKDEV_DEVICEMAJOR;
     
104.     simp_blkdev_disk->first_minor = 0;
     
105.     simp_blkdev_disk->fops = &simp_blkdev_fops;
     
106.     simp_blkdev_disk->queue = simp_blkdev_queue;
     
107.     set_capacity(simp_blkdev_disk, SIMP_BLKDEV_BYTES>>9/*equals SIMP_BLKDEV_BYTES/512*/);
     
108. 
     
109.     add_disk(simp_blkdev_disk);
     
110.     return 0;
     
111. 
     
112. err_alloc_disk:
     
113.     return ret;
     
114. 
     
115. err_init_queue:
     
116.     put_disk(simp_blkdev_disk);
     
117.     return ret;
     
118.    
     
119. }
     
120. 
     
121. static void __exit simp_blkdev_exit(void)
     
122. {
     
123.     put_disk(simp_blkdev_disk);
     
124.     blk_cleanup_queue(simp_blkdev_queue);
     
125.     del_gendisk(simp_blkdev_disk);
     
126. 
     
127. }
     
128. 
     
129. module_init(simp_blkdev_init);
     
130. module_exit(simp_blkdev_exit);
     

复制代码

编译完成之后，insmod。发现有/dev/simp_blkdev了
接下来使用fdisk
[root@TM-0166 blockDeviceTest]# fdisk /dev/simp_blkdev

Unable to read /dev/simp_blkdev
[root@TM-0166 blockDeviceTest]# tail -n 30 /var/log/messages
Aug  3 09:20:26 TM-0166 gdm-simple-slave[2497]: DEBUG: Writing wtmp session record to /var/log/wtmp
Aug  3 09:20:26 TM-0166 gdm-simple-slave[2497]: DEBUG: Adding new utmp record
Aug  3 09:20:26 TM-0166 gdm-simple-slave[2497]: DEBUG: GdmSimpleSlave: session started 2649
Aug  3 09:20:29 TM-0166 pulseaudio[2703]: main.c: This program is not intended to be run as root (unless --system is specified).
Aug  3 09:20:29 TM-0166 pulseaudio[2703]: pid.c: Stale PID file, overwriting.
Aug  3 09:20:29 TM-0166 pulseaudio[2703]: alsa-util.c: Device front:0 doesn't support 44100 Hz, changed to 44099 Hz.
Aug  3 09:20:32 TM-0166 gconfd (root-2617): Resolved address "xml:readwrite:/root/.gconf" to a writable configuration source at position 0
Aug  3 09:20:33 TM-0166 pulseaudio[2703]: module-x11-xsmp.c: X11 session manager not running.
Aug  3 09:20:33 TM-0166 pulseaudio[2703]: module.c: Failed to load  module "module-x11-xsmp" (argument: "": initialization failed.
Aug  3 09:20:38 TM-0166 gnome-keyring-daemon[2648]: adding removable location: volume_label_VMware_Tools at /media/VMware Tools
Aug  3 09:20:38 TM-0166 hald: mounted /dev/sr0 on behalf of uid 0
Aug  3 09:21:44 TM-0166 kernel:  simp_blkdev:<3>Buffer I/O error on device simp_blkdev, logical block 0
Aug  3 09:21:44 TM-0166 kernel: Buffer I/O error on device simp_blkdev, logical block 0
Aug  3 09:21:44 TM-0166 kernel: Buffer I/O error on device simp_blkdev, logical block 0
Aug  3 09:21:44 TM-0166 kernel: Buffer I/O error on device simp_blkdev, logical block 0
Aug  3 09:21:44 TM-0166 kernel: Buffer I/O error on device simp_blkdev, logical block 0
Aug  3 09:21:44 TM-0166 kernel: Buffer I/O error on device simp_blkdev, logical block 0
Aug  3 09:21:44 TM-0166 kernel: Buffer I/O error on device simp_blkdev, logical block 0
Aug  3 09:21:44 TM-0166 kernel: Dev simp_blkdev: unable to read RDB block 0
Aug  3 09:21:44 TM-0166 kernel: Buffer I/O error on device simp_blkdev, logical block 0
Aug  3 09:21:44 TM-0166 kernel: Buffer I/O error on device simp_blkdev, logical block 0
Aug  3 09:21:44 TM-0166 kernel:  unable to read partition table
Aug  3 09:22:23 TM-0166 kernel: Buffer I/O error on device simp_blkdev, logical block 0
Aug  3 09:22:23 TM-0166 kernel: Buffer I/O error on device simp_blkdev, logical block 1
Aug  3 09:22:23 TM-0166 kernel: Buffer I/O error on device simp_blkdev, logical block 2
Aug  3 09:22:23 TM-0166 kernel: Buffer I/O error on device simp_blkdev, logical block 3
Aug  3 09:22:23 TM-0166 kernel: Buffer I/O error on device simp_blkdev, logical block 0
Aug  3 09:22:23 TM-0166 kernel: Buffer I/O error on device simp_blkdev, logical block 4095
Aug  3 09:22:23 TM-0166 kernel: Buffer I/O error on device simp_blkdev, logical block 4095
Aug  3 09:22:23 TM-0166 kernel: Buffer I/O error on device simp_blkdev, logical block 0

内核：[root@TM-0166 blockDeviceTest]# uname -r
2.6.25-14.fc9.i686
gcc version 4.3.0 20080428 (Red Hat 4.3.0- (GCC)

fei1700

bio_endio(bio, -EIO);
返回-EIO，读失败

c04n05

回复 2# fei1700
[root@TM-0166 blockDeviceTest]# cat /proc/buddyinfo
Node 0, zone      DMA     22      9     10      7     11      9      5      2      2      0      0
Node 0, zone   Normal     56     50     30     74     24     15      2     11     14     12      0
[root@TM-0166 blockDeviceTest]#

感谢您的指点。
根据后文来看。应该是我这机器没有高端内存所致？
如果是这样的话，类似这段代码的
            iovec_mem = kmap(bvec->bv_page) + bvec->bv_offset;
            memcpy(iovec_mem, dsk_mem, bvec->bv_len);
            kunmap(bvec->bv_page);
又应该变成什么样子呢？

fei1700

Aug  3 09:21:44 TM-0166 kernel: Buffer I/O error on device simp_blkdev, logical block 0
Aug  3 09:21:44 TM-0166 kernel:  unable to read partition table

如果你要是指这2个错误的话，那就不是高端内存的问题吧

Buffer I/O error是因为bio_endio(bio, -EIO); 传进去的是-EIO，原文后面都有改成bio_endio(bio, 0);这个返回0的，才不会返回Buffer I/O error
unable to read partition table是没读到分区表，如果内容不是有效的分区表都会这么现实，你只是memcpy一段废数据，肯定有这个错误，但如果块设备本身不带分区表，这个错误也应该可以忽略

c04n05

回复 4# fei1700
看来就是这个错误了。我把这个函数里面的-EIO改成0 之后就ok了。。。
不过为啥我的机器里面没有那个高端内存呢？


还有另外一个问题，一旦我卸载这个模块。就提示Segmentation fault 然后系统挂掉了。