[Ocfs2-devel] [patch 02/10] ocfs2: free inode when i_count becomes zero

[Xue jiufei <xuejiufei@huawei.com>]

On 2014/8/14 2:03, Mark Fasheh wrote:
> On Wed, Aug 06, 2014 at 01:32:02PM -0700, Andrew Morton wrote:
>> From: Xue jiufei <xuejiufei@huawei.com>
>> Subject: ocfs2: free inode when i_count becomes zero
>>
>> Disk inode deletion may be heavily delayed when one node unlink a file
>> after the same dentry is freed on another node(say N1) because of memory
>> shrink but inode is left in memory.  This inode can only be freed while N1
>> doing the orphan scan work.
>>
>> However, N1 may skip orphan scan for several times because other nodes may
>> do the work earlier.  In our tests, it may take 1 hour on 4 nodes cluster
>> and this will cause bad user experience.  So we think the inode should be
>> freed when i_count becomes zero to avoid such circumstances.
> 
> Firstly, thanks for the patch Xue.
> 
> I understand your problem and I definitely agree that it hurts the user
> experience. If the inode is free to be deleted we shouldn't be taking so
> long to get rid of it.
> 
> What I'm worried about is that we're always going to tell the kernel to
> evict the inode now, which will always cause some sort of cluster locking.
> 
> I need to look at this more and think about it a bit. Maybe there's a better
> way?
> 	--Mark
> 
> --
In most cases, the refcount of inode would not be zero because there
is one or more dentrys associated with it. So only in this situation
that a dentry is force to be freed because of memory pressure but the
inode is left, we increase the probability of inode eviction. I think it
is acceptable.

Thanks,
Xuejiufei

> Mark Fasheh
> .
>