[Ocfs2-devel] [PATCH 1/2] ocfs2: flush truncate log in case it contains too many clusters.

[Mark Fasheh]

Hi Tao,

On Sun, Sep 19, 2010 at 03:20:28PM +0800, Tao Ma wrote:
> When we test whether we need to flush truncate log in
> ocfs2_truncate_log_needs_flush, we only take care of
> whether the truncate log is full. But if the volume is
> small and  we have large block size(in this case truncate
> log can store too many records), we may be too late
> for flushing if the user create/write/delete files quickly.
> 
> So I add a new FLUSH_TRUNCATE_LOG_RATIO so that we will also
> check whether the number of truncated clusters has reached
> a watermark, if yes, flush the truncate log.
> It resolves the ossbug #1288 somehow.

The problem with the ratio of course is that it doesn't necessarily
correlate to when we actually run out of space. Also, I am concerned that a
10% disk-size limit on truncate log could hurt us in some cases (maybe
truncate of a huge file in the middle of some other rms?)


How about an alternate solution - at the time we see -ENOSPC (during write
for example), why not drop all the allocator locks (global bitmap, local
alloc) and then look at the truncate log for a sufficiently sized extent?
Removing it from the truncate log at that point shouldn't be too hard and
we'd always be able to fill it up completely.
	--Mark

--
Mark Fasheh