[Lustre-discuss] e2fsck

[Robin Humble]

On Sat, Feb 21, 2009 at 04:13:49PM -0700, Andreas Dilger wrote:
>On Feb 21, 2009  01:09 -0500, Robin Humble wrote:
>> On Fri, Feb 20, 2009 at 02:10:50PM -0700, Andreas Dilger wrote:
>> >On Feb 19, 2009  20:42 -0500, Robin Humble wrote:
>> >> in 5 out of 6 e2fsck's I do after an OSS crash, I get one free blocks
>> >> count wrong and often a bitmap in a group that wants to be corrected.
>> >> 
>> >> is this normal?
>> >> or is it an ldiskfs or an e2fsck bug?
>> >
>> >Do you have the "MMP" feature enabled?
>> 
>> no, MMP is off.
>> 
>> there is a small chance that this is the first time the partitions have
>> been fsck'd since MMP was turned off though - I can't be sure about that.
>
>That would probably be the cause - the MMP function uses a single block,
>and it needs to be freed by e2fsck when the feature is disabled.  We
>should probably fix tune2fs to do this at the time MMP is turned off.

awesome diagnosis!

  # e2fsck -f /dev/md0
 e2fsck 1.40.11.sun1 (17-June-2008)
 Pass 1: Checking inodes, blocks, and sizes
 Pass 2: Checking directory structure
 Pass 3: Checking directory connectivity
 Pass 4: Checking reference counts
 Pass 5: Checking group summary information
 short-OST0000: 13/366190592 files (7.7% non-contiguous), 22998875/1464758400 blocks

  # tune2fs -O ^mmp /dev/md0
 tune2fs 1.40.11.sun1 (17-June-2008)

  # e2fsck -f /dev/md0
 e2fsck 1.40.11.sun1 (17-June-2008)
 Pass 1: Checking inodes, blocks, and sizes
 Pass 2: Checking directory structure
 Pass 3: Checking directory connectivity
 Pass 4: Checking reference counts
 Pass 5: Checking group summary information
 Free blocks count wrong for group #0 (31222, counted=31223).
 Fix<y>? yes
 
 Free blocks count wrong (1441759525, counted=1441759526).
 Fix<y>? yes
 
 short-OST0000: ***** FILE SYSTEM WAS MODIFIED *****
 short-OST0000: 13/366190592 files (7.7% non-contiguous), 22998874/1464758400 blocks

cheers,
robin