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Date: Sat, 16 Oct 2004 00:47:31 -0400
From: David Schultz <das@FreeBSD.ORG>
To: Scott Long <scottl@FreeBSD.ORG>
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cc: Andrey Chernov <ache@nagual.pp.ru>
cc: pjd@FreeBSD.ORG
cc: current@FreeBSD.ORG
Subject: Re: Stable panic on shutdown: swapoff: failed to locate N swap
	blocks
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On Fri, Oct 15, 2004, Scott Long wrote:
> Andrey Chernov wrote:
> >On Fri, Oct 15, 2004 at 08:39:34PM -0600, Scott Long wrote:
> >
> >>FWIW, I think that doing a swapoff in the shutdown path is just asking
> >>for trouble.  Fixing whatever bug this is would of course be nice, but
> >>the need for swapoff here is a hack and only opens up up to problems.
> >
> >
> >I agree. It looks like sort of race happens. Application (cvsupd) can be 
> >killed, but its inodes activity delayed by softupdates a bit more (just 
> >raw guess). I see no useful purpose to call swapoff(8) at shutdown stage, 
> >correct me, if I am not right.
> >
> 
> The swapoff hack is needed so that the swapper will close the swap
> device and remove the reference on the gmirror instance, which in turn
> allows gmirror to know that it can close itself down.

Pawel has a patch that moves the swapoff() later in the shutdown
sequence, after all user processes have been killed.  It should
make swapoff() basically a no-op / sanity check, since nothing
should actually be paged out at that point.