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, 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)
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