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From: Daniel Phillips <phillips@bonn-fries.net>
To: Bill Davidsen <davidsen@tmr.com>
Subject: Re: [patch] sys_sync livelock fix
Date: Thu, 14 Feb 2002 01:33:19 +0100
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On February 13, 2002 11:53 pm, Bill Davidsen wrote:
> On Wed, 13 Feb 2002, Daniel Phillips wrote:
> > >   Because people count on something broken we should keep the bug? You do
> > > realize that the sync may NEVER finish?
> > 
> > You do realize that if you lose your data you may NEVER get it back? ;-)
> 
> The sync doesn't protect my data, after my data has been written why
> should I care to wait while all the data in every active program in the
> system gets written. This makes checkpoints stop points on a busy system.

Sync should not wait for data written after the sync.  If it does, it's
broken and needs to be fixed.

> > > Your example is a good example of bad practive, since even with
> > > ext3 a program creating files quickly would lose data, even though the
> > > directory structure is returned to a known state, without stopping the
> > > writing processes the results are unknown.
> > 
> > Huh?  You know about journal commit, right?
> 
> Read or reread my other notes on that, journal prevents directory
> corruption, it doesn't prevent data loss like a database transaction.
> Returning to a known good state does not include "without losing any data
> written to unclosed files."

It's true, we get into great areas with ordered-data journalling, but it's
black and white with full data journalling.

> I leave it to Mr Reiser to clarify that or correct me if data is protected
> without using unbuffered writes.

-- 
Daniel
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