Bug#589413: mdadm: Segmentation fault when converting to RAID6 from RAID5

[Neil Brown]

On Sat, 17 Jul 2010 15:49:22 +0200
Björn Påhlsson <belorn at fukt.bsnet.se> wrote:

.....
> # mdadm --verbose --grow /dev/md0 --level=raid6 --raid-devices=4
> 
> The output of that last command is:
> 
> mdadm level of /dev/md0 changed to raid6
> Segmentation fault
> 

When I try that (thanks for providing precise commands!) it works:

While the array is still performing recovery I get:

# mdadm --verbose --grow /dev/md0 --level=raid6 --raid-devices=4
mdadm: /dev/md0 is performing resync/recovery and cannot be reshaped

and once recovery completes I get:

# mdadm --verbose --grow /dev/md0 --level=raid6 --raid-devices=4
mdadm level of /dev/md0 changed to raid6
mdadm: /dev/md0: Cannot grow - need backup-file
mdadm: aborting level change

This is with 
Version: 3.1.2-2

on Debian, though I'm still running 2.6.32-5-amd64.  I doubt that would
make a difference, but it might.

Can you run the --grow command under 'strace' and post the output.
e.g.
   strace -o /tmp/trace mdadm --verbose --grow /dev/md0 --level=raid6  --raid-devices=4

 and post /tmp/trace.

NeilBrown