From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Thu, 16 Oct 2008 23:38:09 +0100 (BST) From: Hugh Dickins Subject: Re: no way to swapoff a deleted swap file? In-Reply-To: <1224145684.28131.25.camel@twins> Message-ID: References: <20081015202141.GX26067@cordes.ca> <1224145684.28131.25.camel@twins> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org Return-Path: To: Peter Zijlstra Cc: Peter Cordes , linux-kernel@vger.kernel.org, Christoph Hellwig , linux-mm List-ID: On Thu, 16 Oct 2008, Peter Zijlstra wrote: > 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. No immediate answer springs to my mind. It's not something I'd want to add a new system call for. I guess we could put a magic file for each swap area somewhere down in /sys, and allow swapoff to act upon that. If there were other good reasons to add such files, that could make sense. But although I'll willingly admit it's a lacuna, I don't think it's one worth bloating the kernel for. (I would suggest that Peter keep a second link to his swapfiles somewhere safer; but that's then open to the converse complaint, that when he unlinks intentionally but forgets the safe link, the disk space remains mysteriously in use.) Sorry for being unhelpful! Hugh -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org