linux-kernel - Re: [PATCH 0/6] vfs: provide automatic kernel freeze / resume

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Message-ID: <CAPnZJGB8XKtv8W7KYtyZ7AFWWB-LTG_nP3wLAzus6jHFp_mWfg@mail.gmail.com>
Date:   Wed, 7 Jun 2023 14:13:20 +0300
From:   Askar Safin <safinaskar@...il.com>
To:     Miklos Szeredi <miklos@...redi.hu>
Cc:     Luis Chamberlain <mcgrof@...nel.org>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        Bernd Schubert <bernd.schubert@...tmail.fm>,
        linux-pm@...r.kernel.org,
        fuse-devel <fuse-devel@...ts.sourceforge.net>
Subject: Re: [PATCH 0/6] vfs: provide automatic kernel freeze / resume

I found a workaround for sshfs+suspend problem!

On Tue, Jun 6, 2023 at 5:38 PM Miklos Szeredi <miklos@...redi.hu> wrote:
> Issues remaining:
>
>  - if requests are stuck (e.g. network is down) then the requester
> process can't be frozen and suspend will still fail.

> Solution to both these are probably non-kernel: impacted servers need
> to receive notification from systemd when suspend is starting and act
> accordingly.

Okay, so you said that the only way to solve the problem "network is
down" is to fix the problem at the sshfs side. Unfortunately, sshfs
project was closed ( https://github.com/libfuse/sshfs ). So the only
remaining option is to use some hack. And I found such a hack!

I simply added "-o ServerAliveInterval=10" to sshfs command. This will
cause ssh process exit if remote side is unreachable. Thus the bug is
prevented. I tested the fix and it works.

But this will mean that ssh process will exit in such situation, and
thus sshfs process will exit, too. If this is not what you want, then
also add "-o reconnect" option, this will restart connection if ssh
dies. So the final command will look like this:

sshfs -o reconnect,ServerAliveInterval=10 ...

This finally solved the problem for me.

But one issue still remains: if the network goes down and then you
immediately try to access sshfs filesystem and then you will try to
suspend (and ssh doesn't yet noticed that the network gone down), then
suspend will still fail. (I tested this situation, the suspend
actually fails.) But I don't think I even will reach such situation.
The lesser ServerAliveInterval you will set, the lower is probability
that you will reach such situation

-- 
Askar Safin