linux-kernel - Re: Loud "pop" coming from hard drive on reboot

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Date:	Wed, 18 Apr 2007 14:03:46 +0100
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	Tejun Heo <htejun@...il.com>
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

> 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.

If you see a synchronize cache succeed and you then see the drive
shutdown succeed then you know that a sync cache can be faked as ok
safely. Any other command in between or after and it doesn't get faked

This seems pretty easy to deal with at command issue.

> 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?

Probably not, but it will take a year or so and throughout this time
period everyone with the wrong combination of shutdown and kernel (which
will be a lot of people who compile their own kernels) are going to have
problems caused by what is a very obscure piece of libata internal
behaviour they'll never even know about.

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