Message-ID: <4970A78B.8050605@redhat.com>
Date: Fri, 16 Jan 2009 09:28:11 -0600
From: Eric Sandeen <sandeen@redhat.com>
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To: Valdis.Kletnieks@vt.edu
CC: Pavel Machek <pavel@suse.cz>,
       linux-fsdevel <linux-fsdevel@vger.kernel.org>,
       linux-kernel Mailing List <linux-kernel@vger.kernel.org>,
       Andrew Morton <akpm@linux-foundation.org>,
       Takashi Sato <t-sato@yk.jp.nec.com>
Subject: Re: [PATCH] Allow SysRq emergency sync to thaw frozen filesystems
References: <496EB639.6090800@redhat.com>            <20090116084828.GB4795@atrey.karlin.mff.cuni.cz> <16406.1232119029@turing-police.cc.vt.edu>
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Valdis.Kletnieks@vt.edu wrote:
> On Fri, 16 Jan 2009 09:48:28 +0100, Pavel Machek said:
> 
>> Emergency Sync should not do this. Invent another key.
>>
>> ...because otherwise, if you hit emergency sync but the system is
>> still alive and relies on filesystem freezing, bad stuff will happen.
> 
> Under what conditions would a system be alive and relying on freezing,
> *and* an emergency thaw would be worse than whatever reason you're doing
> an emergency sync?
> 
> Hmm.. guess you *could* get into trouble if you tried to do a Sysrq-[not-s]
> and hit the wrong key - but you have the same danger if you have *any*
> sysrq- invoking an emergency_thaw and hit it by accident...

I could certainly use up another key ('z' is available for unfreeZe) but
I have the same question; under what conditions do you expect to need an
emergency sync and also need to maintain frozen filesystems as frozen?

>From a maximum flexibility and control perspective, it'd be better to
have them separated I suppose.  Is it worth using up another available key?

-Eric

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