[parted-devel] Could someone please look into this?

[ben]

I originally reported this a couple years ago and "bumped" the thread six 
months ago.  I asked again last week. I never got any response.


libparted version 2.3 Debian Sid

This is an example of the problem with ped_disk_get_max_partition_geometry().
With three partitions I ask libparted for a maximum geometry on the last two.
In both cases it is smaller than it could be by a wide margin. This only seems 
to be a problem ith ms-dos partitions.


**** FDISK OUTPUT ****
Start: 1951415550 
End  : 1953520064

Disk /dev/sdc: 1000.2 GB, 1000204886016 bytes
255 heads, 63 sectors/track, 121601 cylinders, total 1953525168 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x0000f013

   Device Boot      Start         End      Blocks   Id  System
/dev/sdc1            2048     2097215     1047584   83  Linux
/dev/sdc2      1951422464  1953520063     1048800   83  Linux
/dev/sdc3      1949317120  1951415548     1049214+  83  Linux


**** libparted partion layout ****

Type: 8 
Start: 0 
End:   62 

Type: 4 
Start: 63 
End:   2047 

Type: 0     <-- first partition
Start: 2048 
End:   2097215 

Type: 4 
Start: 2097216 
End:   1949317119 

Type: 0     <-- second partiton
Start: 1949317120 
End:   1951415548 

Type: 4 
Start: 1951415549 
End:   1951422463 

Type: 0     <-- third partition
Start: 1951422464 
End:   1953520063 

Type: 4 
Start: 1953520064 
End:   1953520064 

Type: 8 
Start: 1953520065 
End:   1953525167 


**** results for max geometry -- constraint any ****

Maximum geometry for 2nd partition
Start: 2104515 
End  : 1951415549 

The first partition ends at 2097215 but libparted
puts the start of a maximized partition at 2104515
which is 7300 sectors or 3.7 megs later.



Maximum geometry for 3rd partition
Start: 1951415550 
End  : 1953520064

Here the beginning is right but the end at 1953520064 is
short of 1953525167 by 5103 sectors or 2.6 meg. 


**** A different setup ****


**** FDISK ****

Disk /dev/sdc: 1000.2 GB, 1000204886016 bytes
255 heads, 63 sectors/track, 121601 cylinders, total 1953525168 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x000e6efb

   Device Boot      Start         End      Blocks   Id  System
/dev/sdc1       976760832  1953520064   488379616+   5  Extended
/dev/sdc2            2048   390704370   195351161+  83  Linux
/dev/sdc3       390717440   402438236     5860398+  83  Linux


**** liblvm ****

Start: 0 
End:   62 

Type: 4 
Start: 63 
End:   2047 

Type: 0 
Start: 2048 
End:   390704370 

Type: 4 
Start: 390704371 
End:   390717439 

Type: 0           <--- partition to maximize
Start: 390717440 
End:   402438236 

Type: 4 
Start: 402438237 
End:   976760831 

Type: 2        
Start: 976760832 
End:   1953520064 

Type: 9 
Start: 976760832 
End:   976760894 

Type: 5 
Start: 976760895 
End:   1953520064 

Type: 8 
Start: 1953520065 
End:   1953525167 

**** results for max geometry -- constraint any ****

Maximum geometry for partition number 2
Start: 390716865 
End  : 976751999 


The partition has 13069 sectors or 6.7 megabytes of room 
before the start and yet only gets 575 sectors from libparted.
After the end it can go to 976760832 but libparted puts
the end at only 976751999 which is 8833 sectors short or
4.5 megs off.

The results here are with a 1.0 TB drive but small drives can do the
same. I have actually seen significantly worse rsults but I haven't
been able to replicate them yet. Thank you for looking into this
issue.