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    SubjectRe: [RFC][PATCH -mm] Freezer: Handle uninterruptible tasks
    Pavel Machek <> writes:


    > I don't know how to do that mechanism... but if we knew where to trap
    > filesystem writes, we could simply freeze at that point, and at that
    > point only, no?

    Any operation at all that has an external effect must not occur after
    the snapshot is made; otherwise, there will be random hard-to-find
    corruptions and other problems occurring as a result. Thus, for
    example, any writes (either directly or indirectly through e.g. a
    filesystem) to non-volatile storage, any network traffic, any
    communication with hardware like a printer must be prevented after the
    snapshot. It seems, though, that in general the kernel will have no way
    to know which operations are safe, and which are not safe.

    (This is why the whole "proper filesystem snapshot support is the
    solution" argument is bogus.)

    Jeremy Maitin-Shepard
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      Last update: 2007-07-09 06:25    [W:0.021 / U:46.464 seconds]
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