[Ocfs2-devel] [PATCH 3/3] Add inode stealing for ocfs2_reserve_new_inode.V2

[Mark Fasheh]

On Fri, Feb 29, 2008 at 09:10:12AM +0800, tao.ma wrote:
>>> @@ -542,6 +577,17 @@ int ocfs2_reserve_new_inode(struct ocfs2_super *osb,
>>>  	status = ocfs2_reserve_suballoc_bits(osb, *ac,
>>>  					     INODE_ALLOC_SYSTEM_INODE,
>>>  					     osb->slot_num, ALLOC_NEW_GROUP);
>>> +	if (status >= 0) {
>>> +		status = 0;
>>> +		goto bail;
>>> +	} else if (status < 0 && status != -ENOSPC) {
>>> +		mlog_errno(status);
>>> +		goto bail;
>>> +	}
>>> +
>>> +	ocfs2_free_ac_resource(*ac);
>>> +
>>> +	status = ocfs2_steal_inode_from_other_nodes(osb, *ac);
>> Does this mean we always search our own first, even if we know it's not
>> likely to have anything in it? Wouldn't it be better to ignore once it's
>> full until we get to one of the spots where you've inserted a call to
>> ocfs2_init_inode_steal_slot)?
> I am worried about the situation that the global bitmap is flushed by other 
> nodes and how the current node notice this and use its own local allocator 
> again. Or should it notice this?
> Another thing is that what if the inode which is owned by this slot deleted 
> by other slots? We should have the ability to allocate the inode from our 
> own slot now.

Both your points come down to "how do we know when another node has changed
the allocators such that we can now allocate inodes from our local
inode_alloc file."

Unfortunately, we have no way of knowing what another node does. I'm mostly 
worried about the inefficency of continuously searching ours when there
isn't likely any room left in it.

One thing we could do is only go back to our local allocator after some time
has passed (or some number of allocs). That way we don't check it every
single time, but we never completely leave it out of the picture either.
	--Mark

--
Mark Fasheh
Principal Software Developer, Oracle
mark.fasheh at oracle.com