[Ocfs2-tools-devel] [PATCH 2/2] defrag.ocfs2: Clear unused inode groups

[Tao Ma]

Joel Becker wrote:
> On Thu, Feb 25, 2010 at 04:03:11PM -0800, Sunil Mushran wrote:
>> I am trying to understand the goal here. How will freeing unused
>> inode_alloc groups defragment the volume? Is this a step 1 in a multi
>> step process? If so, can you elaborate on the rest.
> 
> 	This definitely does not defragment.  It merely reclaims unused
> suballocator space.
yeah, I guess what he means is that in his hypothesis that we allocate 
inodes from inode_alloc groups in a round-robin way(actually he is wrong 
here), the inodes will spread among multiple groups and somehow 
defragmented.
> 
>> At that time I felt online defrag is the only solution. But my thinking
>> has evolved. Right now I think any defrag tool that increases freespace
>> space contiguousness is good. Offline and/or online.
> 
> 	I'll take a simple offline defragmenter, sure.
As for file defragmentation, I think online defragmentation is possible 
now if we reuse the codes of CoW. In general, this is just another type 
of CoW with no refcount operation. But that would be the future plan I 
guess. So now offline defragment is ok.

Regards,
Tao