[Ocfs2-devel] What's the need of OCFS2_INODE_MAYBE_ORPHANED?

[Goldwyn Rodrigues <rgoldwyn@suse.de>]

Hi Srini,

On 01/08/2014 07:29 PM, Srinivas Eeda wrote:
> Hi Goldwyn,
>
> On 01/08/2014 04:12 PM, Goldwyn Rodrigues wrote:
>> Hi,
>>
>> >From the comments in fs/ocfs2/inode.h:90 it seems, this was used in
>> legacy ocfs2 systems when a node received unlink votes. Since unlink
>> votes has been done away with and replaced with open locks, is this
>> flag still required? If yes, why?
> My understanding is that unlink voting protocol was heavy. So the
> following was done to address it.
>
> To do an unlink, dentry has to be removed. In order to do that the node
> has to get EX lock on the dentry which means all other nodes have to
> downconvert. In general EX lock on dentry is acquired only in unlink and
> I assume rename case. So all nodes which down convert the lock mark
> their inode OCFS2_INODE_MAYBE_ORPHANED. The only problem with this is
> that dentry on a node can get purged because of memory pressure which
> marks inode as OCFS2_INODE_MAYBE_ORPHANED even when no unlink was done
> on this inode.
>

I think you are getting confused between dentry_lock (dentry_lockres) 
and open lock (ip_open_lockres). AFAICS, dentry locks are used to 
control the remote dentries.

>
>> >From my ongoing investigation of unlink() times, it seems this flag is
>> causing the delay with releasing the open locks while downconverting
>> dentry locks. The flag is set  _everytime_ a dentry downconvert is
>> performed even if the file  is not scheduled to be deleted. If not, we
>> can be smartly evict the inodes which are *not* to be deleted
>> (i_nlink>0) by not offloading to ocfs2_wq. This way open lock will
>> release faster speeding up unlink on the deleting node.
>>
>>
> Are you referring to the delay caused by ocfs2_drop_dentry_lock queueing
> dentry locks to dentry_lock_list ?. If that's the case, have you tried
> removing following patches which introduced that behavior ? I think that
> quota's deadlock bug might have to be addressed differently ?
>
> ea455f8ab68338ba69f5d3362b342c115bea8e13

Yes, that should make some difference. Let me try that. However, I was 
suggesting we do not set the OCFS2_INODE_MAYBE_ORPHANED flag in 
ocfs2_dentry_convert_worker as well, but I am not sure of the 
consequences and that is the reason I asked why it is used.

> eb90e46458b08bc7c1c96420ca0eb4263dc1d6e5
> bb44bf820481e19381ec549118e4ee0b89d56191

I did not find these gits. Which tree are you referring to?

>
> The above patches were leaving orphan files around which was causing a
> big problem to some applications that removes lot of files which inturn
> caused intermittent hangs
>


-- 
Goldwyn