From: "Rafael J. Wysocki" <rjw@rjwysocki.net>
To: Alan Stern <stern@rowland.harvard.edu>
Cc: Pavel Machek <pavel@ucw.cz>, Oliver Neukum <oneukum@suse.de>,
        Dave Chinner <david@fromorbit.com>,
        Henrique de Moraes Holschuh <hmh@hmh.eng.br>,
        Len Brown <len.brown@intel.com>, Len Brown <lenb@kernel.org>,
        One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Linux PM list <linux-pm@vger.kernel.org>
Subject: Re: [PATCH 1/1] suspend: delete sys_sync()
Date: Thu, 09 Jul 2015 00:04:43 +0200
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On Wednesday, July 08, 2015 10:40:00 AM Alan Stern wrote:
> On Wed, 8 Jul 2015, Pavel Machek wrote:
> 
> > > well, that depends on what the purpose of the sync is supposed to be.
> > > 
> > > If it is there to prevent users from corrupting their filesystems as a result
> > > of a mistake, it is insufficient.  If it's there for other reasons, I'm wondering
> > > what those reasons are (on systems that suspend and resume reliably, because the
> > > original reason to put it in there was to reduce the damage from suspend/resume
> > > crashes).
> > 
> > I put it there, and there were more reasons than "crashes" to put it
> > there.
> > 
> > 1) crashes.
> > 
> > 2) battery is quite likely to run out in suspended machine.
> > 
> > 3) if someone pulls the stick and puts it in other machine, I wanted
> > consistent filesystem at least after journal replay.
> 
> I was going to make the same points.
> 
> From my point of view, whether to issue a sync is a tradeoff.  I can't
> remember any time in the last several years where lack of a sync would
> have caused a problem for my computers, but the possibility still
> exists.
> 
> So on one hand, issuing the sync can help prevent a low-probability 
> problem.  On the other hand, issuing the sync takes a small amount of 
> time (negligible for my purposes but not negligible for Len and 
> others).
> 
> I prefer to pay a very small cost to prevent a low-probability problem.  
> Others may not want to pay, because to them the cost is larger or the 
> probability is lower.
> 
> _That_ is the justification for not eliminating the sync completely but 
> making it optional.

Agreed.

Thanks,
Rafael

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