linux-kernel - Re: [fuse-devel] [PATCH] fuse: make fuse daemon frozen along with kernel threads

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Sat, 9 Feb 2013 18:49:10 +0100
From:	Pavel Machek <pavel@....cz>
To:	Goswin von Brederlow <goswin-v-b@....de>
Cc:	Miklos Szeredi <miklos@...redi.hu>, Li Fei <fei.li@...el.com>,
	rjw@...k.pl, len.brown@...el.com, mingo@...hat.com,
	peterz@...radead.org, biao.wang@...el.com,
	linux-pm@...r.kernel.org, fuse-devel@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org, chuansheng.liu@...el.com
Subject: Re: [fuse-devel] [PATCH] fuse: make fuse daemon frozen along with
 kernel threads

Hi!

> > The only way to *reliably* freeze fuse filesystems is to let it freeze
> > even if there are outstanding requests.  But that's the hardest to
> > implement, because then it needs to allow freezing of tasks waiting on
> > i_mutex, for example, which is currently not possible.  But this is
> > the only way I see that would not have unsolvable corner cases that
> > prop up at the worst moment.
> > 
> > And yes, it would be prudent to  wait some time for pending requests
> > to finish before freezing.  But it's not a requirement, things
> > *should* work without that: suspending a machine is just like a very
> > long pause by the CPU, as long as no hardware is involved.  And with
> > fuse filesystems there is no hardware involved directly by definition.
> > 
> > But I'm open to ideas and at this stage I think even patches that
> > improve the situation for the majority of the cases would be
> > acceptable, since this is turning out to be a major problem for a lot
> > of people.
> 
> For shutdown in userspace there is the sendsigs.omit.d/ to avoid the
> problem of halting/killing processes of the fuse filesystems (or other
> services) prematurely. I guess something similar needs to be done for
> freeze. The fuse filesystem has to tell the kernel what is up.

Would it be feasible to create some kind of fuse-stop-script.sh, and
run it before suspend (from userspace)? It should be pretty similar to
sendsigs.omit.d/ mechanism AFAICT.

I'm sorry, freezer is not too suitable for fuse.

(BTW: for suspend, we may be able to improve it so that it is possible
to remove freezer from it. For hibernation, it would be very hard.)
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/