Size of a partition

[Sascha Effert <fermat@xxxxxxxxxxxxxxxx>]

Hello,

I need to know the size of a partition by a dev_t in a module. Could 
please anyone tell me how I can get it?


What I tried (perhaps uninteresting for you):

To get it I tried to access the hd_struct via bdget(dev)->bd_part. But 
the nr_sects entry results in 0. So I read the data of the wohle disk, 
and I do not understand the output. Can anyone explain me what the 
entrys of the hd_struct mean? And how can I get the size of a Partition?

I tried the following in my module:

gd = bdget(dev)->bd_disk;
if (gd) {
  part = bdget(dev)->bd_part;
  printk(KERN_ALERT "rad: bdev->part: start %lu, size %lu, part-no 
%d\n", part->start_sect, part->nr_sects, part->partno);
  printk(KERN_ALERT "rad: While importing disk (%d,%d) we had first 
minor %d and %d partitions.\n", disk.major, disk.minor, gd->first_minor, 
gd->minors);
  printk(KERN_ALERT "rad: gd: major %d, name %s, cap %lu, dev-name 
%s\n", gd->major, gd->disk_name, gd->capacity, gd->devfs_name);
  for (i=0; i < gd->minors; i++) {
    part = gd->part[i];
    if (part != NULL) {
      printk(KERN_ALERT "rad: part index %d: start %lu, size %lu, 
part-no %d\n", i, part->start_sect, part->nr_sects, part->partno);
    }
  }
}

I get the following output:

Mar  3 18:40:07 aubinc kernel: rad: bdev->part: start 1317330, size 0,
  part-no 1028160
Mar  3 18:40:07 aubinc kernel: rad: While importing disk (8,2) we had
  first minor 0 and 16 partitions.
Mar  3 18:40:07 aubinc kernel: rad: gd: major 8, name sda, cap 12582912,
  dev-name <NULL>
Mar  3 18:40:07 aubinc kernel: rad: part index 0: start 63, size 0,
  part-no 1317267
Mar  3 18:40:07 aubinc kernel: rad: part index 1: start 1317330, size 0,
  part-no 1028160
Mar  3 18:40:07 aubinc kernel: rad: part index 2: start 2345490, size 0,
  part-no 2
Mar  3 18:40:07 aubinc kernel: rad: part index 4: start 2345553, size 0,
  part-no 10233342

This is what fdisk says:

Command (m for help): p

Disk /dev/sda: 6442 MB, 6442450944 bytes
255 heads, 63 sectors/track, 783 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1               1          82      658633+  82  Linux swap/
                                                        Solaris
/dev/sda2              83         146      514080   fc  Unknown
/dev/sda3             147         783     5116702+   f  W95 Ext'd (LBA)
/dev/sda5             147         783     5116671   83  Linux

Command (m for help):

And /dev/sda2 is (8,2):
brw-rw----  1 root disk 8, 2 Oct  2 10:38 /dev/sda2

I don't know whats going wrong.

thanks


Sascha Effert
fermat@xxxxxxxxxxxxxxxx

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