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SubjectRe: NFS locking bug -- limited mtime resolution means nfs_lock() does not provide coherency guarantee
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>>>>> " " == Albert D Cahalan <acahalan@cs.uml.edu> writes:

> It would not be reasonable to try extending ext2 to 64-bit
> times, but milliseconds might be doable. You'd need 4 bytes to
> support the 3 standard time stamps.

> Going to microseconds would require 8 free bytes, which I don't
> think we have. (but we do have more that one might think, due
> to the unimplemented junk)

Don't forget that 2^20 > 10^6, hence if you really want units of
microseconds, you actually only need to save 3 bytes worth of data per
timestamp.

For the purposes of NFS, however the 'microseconds' field doesn't
actually have to mean anything. It's just used as a cookie.
Furthermore, only the mtime field, and to a limited extent the ctime
field, are used for attribute consistency checking.

If NFS was the only concern therefore, you would get far on just
saving one extra 24-bit field.

Cheers,
Trond
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