[Ocfs2-devel] [patch 0/2] Add inode steal in ocfs2-1.2

[Sunil Mushran]

Thanks.

Can you work with Marcos to check this in ocfs2-test repo.

Tao Ma wrote:
> One more thing, it has been tested with my script which has been sent to 
> ocfs2-tools-devel for review. Please see
> http://oss.oracle.com/pipermail/ocfs2-tools-devel/2008-March/000621.html
>
> Regards,
> Tao
>
> tao.ma at oracle.com wrote:
>   
>> Hi all,
>> This patch series add inode steal mechanism for inode allocation and
>> it is backported from 2.6.26.
>>
>> In OCFS2, we allocate the inodes from slot specific inode_alloc to avoid
>> inode creation congestion. The local alloc file grows in a large contiguous
>> chunk. As for a 4K bs, it grows 4M every time. So 1024 inodes will be
>> allocated at a time.
>>
>> Over time, if the fs gets fragmented enough(e.g, the user has created
>> many small files and also delete some of them), we can end up in a situation,
>> whereby we cannot extend the inode_alloc as we don't have a large chunk
>> free in the global_bitmap even if df shows few gigs free. More annoying
>> is that this situation will invariably mean that while one cannot create
>> inodes on one node but can from another node. Still more annoying is that an
>> unused slot may have space for plenty of inodes but is unusable as the user may
>> not be mounting as many nodes anymore.
>>
>> This patch series implement a solution which is to steal inodes from
>> another slot. Now the whole inode allocation process looks like this:
>> 1. Allocate from its own inode_alloc:000X
>>    1) If we can reserve, OK.
>>    2) If fails, try to allocate a large chunk and reserve once again.
>> 2. If 1 fails, try to allocate from the ocfs2_super->inode_steal_slot.
>>    This time, Just try to reserve, we don't go for global_bitmap if
>>    this inode also can't allocate the inode.
>> 3. If 2 fails, try the node next until we reach that steal slot again.
>>
>> ocfs2_super->inode_steal_slot is initalized as the node next to our own
>> slot. And once the inode stealing successes, we will refresh it with
>> the slot we steal inode from. It will also be reinitalized when the
>> local truncate log or local alloc recovery is flushed in which case the global
>> bitmap may be refreshed.
>>
>>     
>
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