Following is a problem description, some observations, a question, and
some sample output:
PROBLEM
=======
I discovered the following problem while trying to add DMRAID support
to GParted:
When creating partitions and updating the /dev/mapper directory
entries, the last number of the partition filename often does not
match the partition minor number.
This causes difficulty in GParted because libraries such as libparted
appear to use the minor number when referencing a partition.
With SCSI or IDE devices, the partition minor numbers appear to always
be in the same order as the last number of the partition filenames.
In fact, the integer remainder of dividing the partition minor number by
the device minor number equals the last number of the partition
filename.
E.g.,
last number of partition filename ==
partition minor number % device minor number
OBSERVATIONS
============
My observations on the problem are as follows:
* partition minor numbers appear to increase linearly in the order the
partitions were created.
whereas:
* Primary and extended partition filenames align to their respective
position in the partition table.
* Logical partition filenames are numbered in order according to the
chain of Extended Boot Records (EBRs).
QUESTION
========
1) Would this problem be considered a bug?
It would seem to me that the partition minor numbers should match
the last number of the partition filename. That is, at least when
using the following formula:
last number of partition filename ==
partition minor number % device minor number
SAMPLE OUTPUT
=============
Following are some details and the sample output:
* An MSDOS partition table was used.
* The partitions were created in the order noted by the device minor
numbers.
* The command "kpartx -a /dev/mapper/isw_idedecefg_Txt" was used
after each partition was created.
<---------- Begin Sample ---------->
gedakc@quad:/dev/mapper$ ll -l
total 0
drwxr-xr-x 2 root root 180 2009-03-13 14:01 ./
drwxr-xr-x 13 root root 14700 2009-03-13 14:01 ../
crw-rw---- 1 root root 10, 63 2009-03-12 15:11 control
brw-rw---- 1 root disk 254, 0 2009-03-13 14:01 isw_idedecefg_Tst
brw-rw---- 1 root disk 254, 1 2009-03-13 13:55 isw_idedecefg_Tst1
brw-rw---- 1 root disk 254, 2 2009-03-13 14:00 isw_idedecefg_Tst2
brw-rw---- 1 root disk 254, 4 2009-03-13 14:01 isw_idedecefg_Tst3
brw-rw---- 1 root disk 254, 3 2009-03-13 14:00 isw_idedecefg_Tst5
brw-rw---- 1 root disk 254, 5 2009-03-13 14:01 isw_idedecefg_Tst6
gedakc@quad:/dev/mapper$ sudo fdisk -l -u isw_idedecefg_Tst
Disk isw_idedecefg_Tst: 159.9 GB, 159996968960 bytes
255 heads, 63 sectors/track, 19451 cylinders, total 312494080 sectors
Units = sectors of 1 * 512 = 512 bytes
Disk identifier: 0x0009635e
Device Boot Start End Blocks Id System
isw_idedecefg_Tst1 63 1044224 522081 83 Linux
isw_idedecefg_Tst2 1044225 280093274 139524525 5 Extended
isw_idedecefg_Tst3 280093275 296479574 8193150 83 Linux
isw_idedecefg_Tst5 1044288 2088449 522081 83 Linux
isw_idedecefg_Tst6 2088513 6281414 2096451 83 Linux
gedakc@quad:/dev/mapper$
<---------- End Sample ---------->
Regards,
Curtis Gedak
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