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    Subjectpossible solution for problem 2 (was Re: [RFC][PATCH -mm] PM: Do not sync filesystems from within the freezer)

    > > > > To get more serious and practical though, I think the solution is to
    > > > > fuzz the userspace/kernelspace distinction. What we really want to
    > > > > do is freeze things that submit I/O, then sync, then freeze anything
    > > > > that processes I/O and needs to be frozen. In effect, redefine fuse
    > > > > processes as freezeable kernel threads.
    > > >
    > > > Another myth, that has been debunked already. The problem is: how do
    > > > you define fuse processes? There's no theoretical or even practial
    > > > way to do that.
    > >
    > > No theoretical or practical way?! I'll freely admit to being quite ignorant
    > > about fuse, but surely there's some way by which they can be distinguished.
    > How? OK, there are some tasks, that read and/or write /dev/fuse. And
    > there are some that just communicate in some way with the above.

    (Not that I'm advocating this, but:)

    You could ask fused to identify tasks involved in fuse handling. "Hey,
    fused, please give me list of PIDs".

    Yes, that would be beyond ugly.

    (I guess I'm advocating this:)

    We probably can do variation on this. Notify fuse early that suspend
    is comming, so we can wait for all the fused requests to be flushed
    (/fusectl/*/waiting going to 0), and then just trap tasks trying to
    communicate with fuse in a sane place (i.e. not a place where VFS
    locks are held).

    ...I'm not saying this is a nice solution, but it should
    work... right...? And should work for hibernation, too...?

    (at this point, we still have problem 1: something in s2ram path
    causes fuse to communicate with its frozen fused. It is not sync, so
    what is it?)
    (cesky, pictures)
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