Hi,
I'm setting up a raid 5 system and I ran across a bug when reshaping an
array with a mounted XFS filesystem on it. This is under linux 2.6.18.2
and mdadm 2.5.5
I have a test array with 3 10 GB disks and a fourth 10 GB spare disk,
and a mounted xfs filesystem on it:
root@localhost $ mdadm --detail /dev/md4
/dev/md4:
Version : 00.90.03
Creation Time : Sat Nov 4 18:58:59 2006
Raid Level : raid5
Array Size : 20964480 (19.99 GiB 21.47 GB)
Device Size : 10482240 (10.00 GiB 10.73 GB)
Raid Devices : 3
Total Devices : 4
Preferred Minor : 4
Persistence : Superblock is persistent
[snip]
------------------------------------
...I Grow it:
root@localhost $ mdadm -G /dev/md4 -n4
mdadm: Need to backup 384K of critical section..
mdadm: ... critical section passed.
root@localhost $ mdadm --detail /dev/md4
/dev/md4:
Version : 00.91.03
Creation Time : Sat Nov 4 18:58:59 2006
Raid Level : raid5
Array Size : 20964480 (19.99 GiB 21.47 GB)
Device Size : 10482240 (10.00 GiB 10.73 GB)
Raid Devices : 4
Total Devices : 4
Preferred Minor : 4
Persistence : Superblock is persistent
-----------------------------------
It goes along and reshapes fine (from /proc/mdstat):
md4 : active raid5 dm-67[3] dm-66[2] dm-65[1] dm-64[0]
20964480 blocks super 0.91 level 5, 64k chunk, algorithm 2 [4/4]
[UUUU]
[====>................] reshape = 22.0% (2314624/10482240)
finish=16.7min
speed=8128K/sec
------------------------------------
When the reshape completes, the full array size gets corrupted:
/proc/mdstat:
md4 : active raid5 dm-67[3] dm-66[2] dm-65[1] dm-64[0]
31446720 blocks level 5, 64k chunk, algorithm 2 [4/4] [UUUU]
- looks good, but-
root@localhost $ mdadm --detail /dev/md4
/dev/md4:
Version : 00.90.03
Creation Time : Sat Nov 4 18:58:59 2006
Raid Level : raid5
>>
>> Array Size : 2086592 (2038.03 MiB 2136.67 MB)
>>
Device Size : 10482240 (10.00 GiB 10.73 GB)
Raid Devices : 4
Total Devices : 4
Preferred Minor : 4
Persistence : Superblock is persistent
(2086592 != 31446720 -- Bad, much too small)
---------------------------------
xfs_growfs /dev/md4 barfs horribly - something about reading past the
end of the device.
If I unmount the XFS filesystem, things work ok:
root@localhost $ umount /dev/md4
root@localhost $ mdadm --detail /dev/md4
/dev/md4:
Version : 00.90.03
Creation Time : Sat Nov 4 18:58:59 2006
Raid Level : raid5
Array Size : 31446720 (29.99 GiB 32.20 GB)
Device Size : 10482240 (10.00 GiB 10.73 GB)
Raid Devices : 4
Total Devices : 4
Preferred Minor : 4
Persistence : Superblock is persistent
(31446720 == 31446720 -- Good)
If I remount the fs, I can use xfs_growfs with no ill effects.
It's a pretty easy work-around to not have the fs mounted during the
resize, but it doesn't seem right for the array size to get borked like
this. If there's anything I can provide to debug this let me know.
Thanks,
Bill
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