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    SubjectRe: [RFC][PATCH 1/4] checkpoint-restart: general infrastructure
    Hi!

    > > > > I have to wonder if this is just a symptom of us trying to do this the
    > > > > wrong way. We're trying to talk the kernel into writing internal gunk
    > > > > into a FD. You're right, it is like a splice where one end of the pipe
    > > > > is in the kernel.
    > > > >
    > > > > Any thoughts on a better way to do this?
    > > >
    > > > Maybe you can invert the logic and let the new syscalls create a file
    > > > descriptor, and then have user space read or splice the checkpoint
    > > > data from it, and restore it by writing to the file descriptor.
    > > > It's probably easy to do using anon_inode_getfd() and would solve this
    > > > problem, but at the same time make checkpointing the current thread
    > > > hard if not impossible.
    > >
    > > Yeah, it does seem kinda backwards. But, instead of even having to
    > > worry about the anon_inode stuff, why don't we just put it in a fs like
    > > everything else? checkpointfs!
    >
    > One reason is that I suspect that stops us from being able to send that
    > data straight to a pipe to compress and/or send on the network, without
    > hitting local disk. Though if the checkpointfs was ram-based maybe not?
    >
    > As Oren has pointed out before, passing in an fd means we can pass a
    > socket into the syscall.

    If you do pass a socket, will it handle blocking correctly? Getting
    deadlocked task would be bad. What happens if I try to snapshot into
    /proc/self/fd/0 ? Or maybe restore from /proc/cmdline?

    --
    (english) http://www.livejournal.com/~pavelmachek
    (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html


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