Re: NFS locking bug -- limited mtime resolution means nfs_lock() does not provide coherency guarantee

[Albert D. Cahalan]

Trond Myklebust writes:

> Relying on the sub-second timing fields is a much more
> implementation-specific. It depends on the capabilities of both the
> filesystem and the server OS.
> Linux and the knfsd server code could easily be modified to provide
> such a service, but the problem (as I've stated before) is that you
> need to save the time somewhere on disk. I believe currently ext2
> provides only 32 bits of storage for mtime (though perhaps somebody
> else could comment on that).

Yes, ext2 has this limit.

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)

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