Mountd, why not use the '-S' flag by default

[Mark Schouten]

Hi,

Rik Macklem wrote:
> Well, there are a couple of things:
> With "-S" all nfsd threads get suspended/resumed whenever exports
> changes. This can result in a "pause" in NFS server response and
> that might be considered a POLA violation.

IMHO, An incidental raised latency is better than input/output errors which breaks files.

> It only works for the new NFS server and not the old one and the
> old one is still used by some. If it was the default, then the
> old and new NFS servers would have had different behaviour.
> (Again, this could be considered a POLA violation.)

Backport? Or detect the old nfsd and ignore the -S flag if it is found?

> When "-S" was introduced by me, it was done as a "stop gap", since I
> had thought that mountd would eventually be replaced by nfse
> (and nfse did allow exports to be updated "atomically" so the problem
>  didn't occur). It now appears that no variant of nfse will end up
> in FreeBSD.

That's more of a reason to enable it by default, if you ask me.

> The last one is noted in the description. If, for some reason, mountd
> crashes during a reload, then all the nfsd threads could be stuck
> suspended. (I don't know if this occurs in practice.)

I've tested (not thoroughly) and I didn't get my client to break. Even with errors in the exports-file, stuff kept working. Doesn't most of NFS break without mountd anyways?

> Basically, I am a coward w.r.t. POLA and almost never change a
> default. (The one case I did change was making rsize, wsize
> default to MAX_BSIZE instead of 32K. By some strange twist of
> fate, this caused a lot of grief, since there was a bug related
> to TSO segments just under 64K for network interfaces that are
> limited to 32 transmit segments. I am still saying "disable TSO"
> to people running older FreeBSD systems because of this.;-)

Hehe. :) All I can say is that I would prefer rsize and wsize to be bigger. But that's a different story. :)

Regards,

--
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Mark Schouten  | Tuxis Internet Engineering
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