Resizing dmraid partition removes device path entry

[Curtis Gedak]

I booted my computer using the ubuntu-14.04-desktop-i386.iso image, and then tried to grow a 20 GiB ext4 partition to 40 GiB. Unfortunately this failed because at some point the underlying /dev/mapper partition entry disappeared.

Following are some details from before and after the grow operation:

*** Boot ubuntu 14.04 i386 from Live CD (before running GParted)

ubuntu@ubuntu:~$ ls -l /dev/mapper
total 0
crw------- 1 root root 10, 236 Jun 12 16:43 control
brw-rw---- 1 root disk 252, 1 Jun 12 16:43 isw_efjbbijhh_Vol0
brw------- 1 root root 252, 0 Jun 12 16:43 isw_efjbbijhh_Vol0p1
ubuntu@ubuntu:~$ ls -l /dev/dm*
brw-rw---- 1 root disk 252, 0 Jun 12 16:43 /dev/dm-0
brw-rw---- 1 root disk 252, 1 Jun 12 16:43 /dev/dm-1
ubuntu@ubuntu:~$ ls -l /dev/md*
ls: cannot access /dev/md*: No such file or directory
ubuntu@ubuntu:~$

*** Start GParted, but do not perform any operations

ubuntu@ubuntu:~$ ls -l /dev/mapper
total 0
crw------- 1 root root 10, 236 Jun 12 16:43 control
brw-rw---- 1 root disk 252, 1 Jun 12 16:43 isw_efjbbijhh_Vol0
brw------- 1 root root 252, 0 Jun 12 16:43 isw_efjbbijhh_Vol0p1
ubuntu@ubuntu:~$ ls -l /dev/dm*
brw-rw---- 1 root disk 252, 0 Jun 12 16:43 /dev/dm-0
brw-rw---- 1 root disk 252, 1 Jun 12 16:43 /dev/dm-1
ubuntu@ubuntu:~$ ls -l /dev/md*
ls: cannot access /dev/md*: No such file or directory
ubuntu@ubuntu:~$

*** Queue and Apply operation to grow ext4 partition from 20 GiB to 40 GiB
*** --> FAILS - see attached gparted_details-ubuntu1404-dm-grow.htm log file

ubuntu@ubuntu:~$ ls -l /dev/mapper
total 0
crw------- 1 root root 10, 236 Jun 12 16:43 control
brw-rw---- 1 root disk 252, 1 Jun 12 16:50 isw_efjbbijhh_Vol0
ubuntu@ubuntu:~$ ls -l /dev/dm*
brw-rw---- 1 root disk 252, 0 Jun 12 16:50 /dev/dm-0
brw-rw---- 1 root disk 252, 1 Jun 12 16:43 /dev/dm-1
ubuntu@ubuntu:~$ ls -l /dev/md*
ls: cannot access /dev/md*: No such file or directory
ubuntu@ubuntu:~$

*** The missing entry can be re-added using kpartx

ubuntu@ubuntu:~$ sudo kpartx -l /dev/mapper/isw_efjbbijhh_Vol0
isw_efjbbijhh_Vol0p1 : 0 83886080 /dev/mapper/isw_efjbbijhh_Vol0 2048
ubuntu@ubuntu:~$ sudo kpartx -a /dev/mapper/isw_efjbbijhh_Vol0
ubuntu@ubuntu:~$ ls -l /dev/mapper
total 0
crw------- 1 root root 10, 236 Jun 12 16:43 control
brw-rw---- 1 root disk 252, 1 Jun 12 16:50 isw_efjbbijhh_Vol0
brw-rw---- 1 root disk 252, 0 Jun 12 16:57 isw_efjbbijhh_Vol0p1
ubuntu@ubuntu:~$

*** I tried several other operations. The one thing in common is that the partition entry in /dev/mapper disappears whenever a change it made to it by GParted through the libparted library.

[Curtis Gedak (gedakc)]

gparted_details.htm log file that failed when attempting to grow an ext4 20 GiB dmraid partition to 40 GiB.

[Phillip Susi (psusi)]

Hi Curtis, are you still able to reproduce this? Do you have a dedicated machine for testing this on? If so, would you mind giving me remote access to debug it?

[Curtis Gedak (gedakc)]

Hi Phillip,

Good news! This problem does not exist with Ubuntu 15.10.

I booted my computer using the ubuntu-15.10-desktop-i386.iso image,
and then successfully grew a 20 GiB ext4 partition to 40 GiB on my
Intel Software RAID (Fake RAID).

Following are the details of the successful test.

*** Boot ubuntu 15.10 i386 from Live CD (before running GParted)

ubuntu@ubuntu:~$ ls -l /dev/mapper
total 0
crw------- 1 root root 10, 236 Nov 11 21:40 control
brw-rw---- 1 root disk 252, 1 Nov 11 21:39 isw_efjbbijhh_Vol0
lrwxrwxrwx 1 root root 7 Nov 11 21:40 isw_efjbbijhh_Vol0p1 -> ../dm-0
ubuntu@ubuntu:~$ ls -l /dev/dm*
brw-rw---- 1 root disk 252, 0 Nov 11 21:40 /dev/dm-0
brw-rw---- 1 root disk 252, 1 Nov 11 21:40 /dev/dm-1
ubuntu@ubuntu:~$

*** Use GParted to queue and apply operation to grow ext4 partition
    from 20 GiB to 40 GiB

ubuntu@ubuntu:~$ sudo gparted
======================
libparted : 3.2
======================
ubuntu@ubuntu:~$

*** SUCCESS!

*** Device entries after successful resize.

ubuntu@ubuntu:~$ ls -l /dev/mapper
total 0
crw------- 1 root root 10, 236 Nov 11 21:40 control
brw-rw---- 1 root disk 252, 1 Nov 11 21:46 isw_efjbbijhh_Vol0
lrwxrwxrwx 1 root root 7 Nov 11 21:47 isw_efjbbijhh_Vol0p1 -> ../dm-0
ubuntu@ubuntu:~$ ls -l /dev/dm*
brw-rw---- 1 root disk 252, 0 Nov 11 21:47 /dev/dm-0
brw-rw---- 1 root disk 252, 1 Nov 11 21:40 /dev/dm-1
ubuntu@ubuntu:~$

Based on this test I suggest this problem be closed as resolved with
ubuntu 15.10. :-)

Curtis

[Phillip Susi (psusi)]

That is good, but does it still exist on 14.04?

[Curtis Gedak (gedakc)]

I don't have 14.04 installed on this computer. I tested using the ubuntu-14.04-desktop-i386.iso live image.

Did you change anything in libparted for ubuntu 14.04 since it was first released?

If you like I can test using the ubuntu-14.04.3-desktop-i386.iso live image.

[Phillip Susi (psusi)]

That would be great. If it still is a problem in 14.04.3 it would be good to get it fixed there since it is an LTS and will still be supported for a few more years.

[Curtis Gedak (gedakc)]

Hi Phillip,

I tested growing an ext4 file system from 20 GiB to 40 GiB on Intel Software RAID (Fake RAID) using the ubuntu-14.04.3-desktop-i386.iso image and all worked as it should. :-)

Hence in my opinion this bug can be closed.

Curtis

[Phillip Susi (psusi)]

Thanks Curtis.