Re: [PATCH] nilfs-utils: Work around uncleanable full filesystem

[Vyacheslav Dubeyko <slava-yeENwD64cLxBDgjK7y7TUQ@public.gmane.org>]

Hi Ryusuke,

On Tue, 2013-01-15 at 19:43 +0900, Ryusuke Konishi wrote:

[snip]
> >
> >As I understand the code of nilfs_cleanerd, this code is correct without
> >your changing. The ss_nongc_ctime is the creation time of the last
> >segment not for GC. When thr is set then it compared with sui_lastmod.
> >The sui_lastmod is the timestamp of last modification. So, the
> >nilfs_cleanerd works right.
> >
> >I think that this is a bug on the kernel side. My current vision is that
> >in some environment the ns_nongc_ctime can be not updated correctly. So,
> >you have such threshold that prevent from segments clearing.
> 
> I guess the problem is caused because ss_nongc_ctime is not updated by
> the kernel module if dirty blocks created by file operations are written
> out through nilfs_clean_segments function.   Actually,
> nilfs_clean_segments() can roll together normal dirty blocks.
> 
> So, if GC is working without interruption, ss_nongc_ctime may not be
> updated long time.
> 
> If this is the cause of the problem, nilfs2 log writer should be changed
> so that nilfs->ns_nongc_ctime is updated with sci->sc_seg_ctime if
> there is a file system change (file/directory change or an ifile change).
> 
> NILFS_SC_HAVE_DELTA flag may be available for this purpose.
> 
> The ss_nongc_ctime check is needed to make GC stoppable.
> Without this check, GC can continue endlessly even if the file system
> doesn't have any change.
> 

Thank you for your detailed explanation. It is very helpful for me.

But, currently, I can't reproduce the issue. All works fine on my side.

With the best regards,
Vyacheslav Dubeyko.

> With regards,
> Ryusuke Konishi
> 



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