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    SubjectRe: [man-pages RFC PATCH v4] statx, inode: document the new STATX_INO_VERSION field
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    On Mon, 2022-09-12 at 09:51 -0400, J. Bruce Fields wrote:
    > On Mon, Sep 12, 2022 at 08:55:04AM -0400, Jeff Layton wrote:
    > > Because of the "seen" flag, we have a 63 bit counter to play with. Could
    > > we use a similar scheme to the one we use to handle when "jiffies"
    > > wraps? Assume that we'd never compare two values that were more than
    > > 2^62 apart? We could add i_version_before/i_version_after macros to make
    > > it simple to handle this.
    >
    > As far as I recall the protocol just assumes it can never wrap. I guess
    > you could add a new change_attr_type that works the way you describe.
    > But without some new protocol clients aren't going to know what to do
    > with a change attribute that wraps.
    >

    Right, I think that's the case now, and with contemporary hardware that
    shouldn't ever happen, but in 10 years when we're looking at femtosecond
    latencies, could this be different? I don't know.

    > I think this just needs to be designed so that wrapping is impossible in
    > any realistic scenario. I feel like that's doable?
    >
    > If we feel we have to catch that case, the only 100% correct behavior
    > would probably be to make the filesystem readonly.

    What would be the recourse at that point? Rebuild the fs from scratch, I
    guess?
    --
    Jeff Layton <jlayton@kernel.org>

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