Re: [fuse-devel] [PATCH] fuse: make fuse daemon frozen along withkernel threads
From: Pavel Machek
Date: Sat Feb 09 2013 - 12:49:21 EST
> > 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.)
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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