Messages in this thread |  | | From | (Stephen R. van den Berg) | Date | Wed, 8 Jan 1997 00:09:49 +0100 | Subject | Re: NFS Problem in Kernel 2.0.27: inode status not updated |
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Matthias Urlichs <smurf@work.smurf.noris.de> wrote: > srb@cuci.nl (Stephen R. van den Berg) writes: >> Tim Wright <timw@sequent.com> 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 implementation.
>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. -- Sincerely, srb@cuci.nl 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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