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Message-ID: <4626141B.7090703@gmail.com>
Date: Wed, 18 Apr 2007 21:50:35 +0900
From: Tejun Heo <htejun@...il.com>
To: Alan Cox <alan@...rguk.ukuu.org.uk>
CC: 7eggert@....de, Chuck Ebbert <cebbert@...hat.com>,
emisca <emisca.ml@...il.com>,
Jan Engelhardt <jengelh@...ux01.gwdg.de>,
Bartlomiej Zolnierkiewicz <bzolnier@...il.com>,
linux-kernel <linux-kernel@...r.kernel.org>,
linux-ide@...r.kernel.org, Adrian Bunk <bunk@...sta.de>,
Andrew Morton <akpm@...l.org>
Subject: Re: Loud "pop" coming from hard drive on reboot
Tejun Heo wrote:
> Alan Cox wrote:
>>> Not that simple. Most disks don't spin up on SYNCHRONIZE_CACHE if
>>> its cache is clean. Sadly some disks actually spin up when it
>>> receives spin down command while spun down to immediately spin down
>>> again, so we would be fixing problem for some number of disks while
>>> breaking others. :-(
>>
>> Snoop the last command sent to the drive, that tells you if you can skip
>> the cache flush ?
>
> Thought about that and querying power state before doing shutdown
> sequence but things get somewhat ugly because shutdown sequence is
> driven from sd->shutdown(). We'll have to snoop both sync and shutdown
> commands and check whether the system is shutting down. Also, I felt
> very uneasy about faking successful completion to SYNCHRONIZE_CACHE.
>
> I dunno. It's already too late for 2.6.21. I was hoping we could get
> distros to update shutdown utilities in not-too-distant future but I
> have no experience with that. Is that just a wishful thinking?
>
FWIW, the the following message describes the proposed solution.
http://thread.gmane.org/gmane.linux.scsi/30487/focus=17392
--
tejun
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