linux-kernel - Re: no way to swapoff a deleted swap file?

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Message-Id: <1224145684.28131.25.camel@twins>
Date:	Thu, 16 Oct 2008 10:28:04 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Peter Cordes <peter@...des.ca>
Cc:	linux-kernel@...r.kernel.org,
	Christoph Hellwig <hch@...radead.org>, hugh <hugh@...itas.com>,
	linux-mm <linux-mm@...ck.org>
Subject: Re: no way to swapoff a deleted swap file?

On Wed, 2008-10-15 at 17:21 -0300, Peter Cordes wrote:
> I unlinked a swapfile without realizing I was still swapping on it.
> Now my /proc/swaps looks like this:
> Filename                                Type            Size    Used	Priority
> /var/tmp/EXP/cache/swap/1\040(deleted)  file            1288644 1448	-1
> /var/tmp/EXP/cache/swap/2\040(deleted)  file            1433368 0	-2
> 
>  AFAICT, there's nothing I can pass to swapoff(2) that will make the
> kernel let go of them.  If that's the case, please consider this a
> feature request for a way to do this.  Now I'm going to have to reboot
> before I can mkfs that partition.
> 
>  If kswapd0 had a fd open on the swap files, swapoff /proc/$PID/fd/3
> could possibly work.  But it looks like the files are open but with no
> user-space accessable file descriptors to them.  Which makes sense,
> except for this case.

Right, except that kswapd is per node, so we'd either have to add it to
all kswapd instances or a random one. Also, kthreads don't seem to have
a files table afaict.

But yes, I see your problem and it makes sense to look for a nice
solution.

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