Hi Neil
I encounter the problem when I reshape a 4-disks raid5 to raid5. It just can
appear with loop devices.
The steps are:
[root@dhcp-12-158 mdadm-3.3.2]# mdadm -CR /dev/md0 -l5 -n5 /dev/loop[0-4] --assume-clean
mdadm: /dev/loop0 appears to be part of a raid array:
level=raid5 devices=6 ctime=Fri May 15 13:47:17 2015
mdadm: /dev/loop1 appears to be part of a raid array:
level=raid5 devices=6 ctime=Fri May 15 13:47:17 2015
mdadm: /dev/loop2 appears to be part of a raid array:
level=raid5 devices=6 ctime=Fri May 15 13:47:17 2015
mdadm: /dev/loop3 appears to be part of a raid array:
level=raid5 devices=6 ctime=Fri May 15 13:47:17 2015
mdadm: /dev/loop4 appears to be part of a raid array:
level=raid5 devices=6 ctime=Fri May 15 13:47:17 2015
mdadm: Defaulting to version 1.2 metadata
mdadm: array /dev/md0 started.
[root@dhcp-12-158 mdadm-3.3.2]# mdadm /dev/md0 -a /dev/loop5
mdadm: added /dev/loop5
[root@dhcp-12-158 mdadm-3.3.2]# mdadm --grow /dev/md0 --raid-devices 6
mdadm: Need to backup 10240K of critical section..
[root@dhcp-12-158 mdadm-3.3.2]# cat /proc/mdstat
Personalities : [raid6] [raid5] [raid4]
md0 : active raid5 loop5[5] loop4[4] loop3[3] loop2[2] loop1[1] loop0[0]
8187904 blocks super 1.2 level 5, 512k chunk, algorithm 2 [6/6] [UUUUUU]
[>....................] reshape = 0.0% (0/2046976) finish=6396.8min speed=0K/sec
unused devices: <none>
It because the sync_max is set to 0 when run the command --grow
[root@dhcp-12-158 mdadm-3.3.2]# cd /sys/block/md0/md/
[root@dhcp-12-158 md]# cat sync_max
0
I tried reproduce with normal sata devices. The progress of reshape is no problem. Then
I checked the Grow.c. If I use sata devices, in function reshape_array, the return value
of set_new_data_offset is 0. But if I used loop devices, it return 1. Then it call the function
start_reshape.
In the function start_reshape it set the sync_max to reshape_progress. But in sysfs_read it
doesn't read reshape_progress. So it's 0 and the sync_max is set to 0. Why it need to set the
sync_max at this? I'm not sure about this.
I tried to fix this but I'm not sure whether it's the right way. I'll send the patches in
other mails.
Best Regards
Xiao
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