Hi all

   There is the same problem. I can reproduce with the same steps. And
I can reproduce this in a different way too. I don't know whether it's 
the same problem, but the result is the same.

   The different steps are as follows:

mdadm -CR /dev/md0 -l5 -n7 /dev/sda1 /dev/sdb1 /dev/sdc1 /dev/sdd1 /dev/sde1 /dev/sdf1 /dev/sdh1 -x1 /dev/sdi1  --assume-clean --bitmap=internal
mdadm --grow -l0 /dev/md0  --backup-file=tmp0
cat /proc/mdstat 
Personalities : [raid6] [raid5] [raid4] [raid1] [raid0] 
md0 : active raid5 loop3[4] loop2[3] loop1[1] loop0[0]
      2045952 blocks super 1.2 level 5, 512k chunk, algorithm 2 [4/4] [UUUU]
      [>....................]  reshape =  0.0% (0/1022976) finish=5.8min speed=2818K/sec
      
unused devices: <none>

   There is speed 2818K/sec, but if you look by iostat, there is no speed about the disks.


   And there is a workaround:
   mdadm -CR /dev/md0 -l5 -n7 /dev/sda1 /dev/sdb1 /dev/sdc1 /dev/sdd1 /dev/sde1 /dev/sdf1 /dev/sdh1 -x1 /dev/sdi1  --assume-clean --bitmap=internal
   mdadm --grow -l0 /dev/md0

   If we don't specify the backup file. The reshape can finish correctly. 

Best Regards
Xiao

----- Original Message -----

From: "Chris Murphy" <redacted>
To: linux-raid@vger.kernel.org
Sent: Thursday, December 18, 2014 6:20:50 AM
Subject: indefinite hang when growing/reshaping

If this is user error I'd expect a discreet error message, but I don't
get one, just a hang during the reshape following successful --grow
command (going from 3x device raid5 to 4x device raid5).

# cat /proc/mdstat
Personalities : [raid6] [raid5] [raid4]
md127 : active raid5 loop3[4] loop2[3] loop1[1] loop0[0]
      2095104 blocks super 1.2 level 5, 512k chunk, algorithm 2 [4/4] [UUUU]
      [>....................]  reshape =  0.0% (0/1047552)
finish=7.0min speed=2402K/sec

Reproduces with:
kernel-3.17.6-300.fc21.x86_64
mdadm-3.3.2-1.fc21.x86_64
and
3.18.0-2.fc22.i686+debug
mdadm-3.3.2-1.fc21.i686

Details are here:
https://bugzilla.kernel.org/show_bug.cgi?id=89851

--
Chris Murphy
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