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SubjectRe: NFS Problem in Kernel 2.0.27: inode status not updated
Matthias Urlichs <> wrote:
> (Stephen R. van den Berg) writes:
>> Tim Wright <> wrote:
>> >You cannot rely on ANY Unix filesystems semantics using NFSv2.

>> I agree that it's fairly bad. But, if you make sure that you're the
>> only client operating on a certain file which has never existed before,
>> the results aren't so bad (if the NFS-client and server are a good quality
>> implementation).

>Why should you want that?

In order to implement a locking scheme, or a maildir type mail delivery
system, that works across NFS.

>IMHO, relying on any such thing is evil. People will surely use your code
>in environments where that assumption doesn't hold; after all, it works (almost)
>flawlessly regardless, right?

>The "almost" is the problem.

It's not really a problem. The assumption is *not* a requirement to make
the code work correctly. If the assumption does not hold, two things
can happen:
- The code will work regardlessly, because it anticipates some kind of
deviation from the standard.
- The code will report a problem, and will refuse to continue.

>Read maildir(5), a manual page from the qmail system. It describes a reliable
>mail delivery system which works over NFS, even if multiple mail servers
>write to the same mail spool.

It makes use of the same assumptions I made to implement the
NFS-resistent-locking scheme. It wouldn't surprise me if Bernstein
took a good look at the locking scheme before creating the maildir

>much yet, unfortunately. However, IMHO it's a much better idea to create a
>patch for elm which supports maildir than to invent yet another limited-use
>locking scheme.

This locking scheme predates the maildir implementation by more than six
years. So we're not inventing "yet another" locking scheme.
Stephen R. van den Berg (AKA BuGless).
"I don't like this word bomb. It is not a bomb, it is a device,
which explodes." French Ambassador about the atomic tests.

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