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From: Bernd Schubert <bernd.schubert@fastmail.fm>
To: nbd@other.debian.org,
	Linux FS Devel <linux-fsdevel@vger.kernel.org>,
	miklos <mszeredi@redhat.com>, Wouter Verhelst <w@uter.be>
Subject: Re: Why do NBD requests prevent hibernation, and FUSE requests do not?
Date: Wed, 31 Aug 2022 01:02:16 +0200	[thread overview]
Message-ID: <f7110017-8606-8e50-7d86-fc53324a571d@fastmail.fm> (raw)
In-Reply-To: <87k06qb5to.fsf@vostro.rath.org>



On 8/30/22 08:31, Nikolaus Rath wrote:
> Hello,
> 
> I am comparing the behavior of FUSE and NBD when attempting to hibernate
> the system.
> 
> FUSE seems to be mostly compatible, I am able to suspend the system even
> when there is ongoing I/O on the fuse filesystem.
> 

....

> 
> As far as I can tell, the problem is that while an NBD request is
> pending, the atsk that waits for the result (in this case *rsync*) is
> refusing to freeze. This happens even when setting a 5 minute timeout
> for freezing (which is more than enough time for the NBD request to
> complete), so I suspect that the NBD server task (in this case nbdkit)
> has already been frozen and is thus unable to make progress.
> 
> However, I do not understand why the same is not happening for FUSE
> (with FUSE requests being stuck because the FUSE daemon is already
> frozen). Was I just very lucky in my tests? Or are tasks waiting for
> FUSE request in a different kind of state? Or is NBD a red-herring here,
> and the real trouble is with ZFS?
> 
> It would be great if someone  could shed some light on what's going on.

I guess it is a generic issue also affecting fuse, see this patch

https://lore.kernel.org/lkml/20220511013057.245827-1-dlunev@chromium.org/

A bit down the thread you can find a reference to this ancient patch

https://linux-kernel.vger.kernel.narkive.com/UeBWfN1V/patch-fuse-make-fuse-daemon-frozen-along-with-kernel-threads

I had also asked about NFS when the server side is down, (and so a 
request reply will not come) but didn't get an answer.


- Bernd

  reply	other threads:[~2022-08-30 23:02 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-08-30  6:31 Why do NBD requests prevent hibernation, and FUSE requests do not? Nikolaus Rath
2022-08-30 23:02 ` Bernd Schubert [this message]
2022-09-07 15:50   ` Nikolaus Rath
2022-09-02 12:49 ` Wouter Verhelst
2022-09-07 10:18   ` Nikolaus Rath
2022-09-16  8:05   ` Nikolaus Rath

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