Subject: RE: recent nfs change causes autofs regression
From: Trond Myklebust <trond.myklebust@fys.uio.no>
To: Hua Zhong <hzhong@gmail.com>
Cc: "'Linux Kernel Mailing List'" <linux-kernel@vger.kernel.org>,
       "'Linus Torvalds'" <torvalds@linux-foundation.org>,
       akpm@linux-foundation.org
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Date: Fri, 31 Aug 2007 00:31:22 -0400
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On Thu, 2007-08-30 at 16:44 -0700, Hua Zhong wrote:
> > How is the NFS client to know that these directories are disjoint, or
> > that no-one will ever create a hard link from one directory to another?
> > To my knowledge, the only way to ensure this is to put them on
> > different disk partitions.
> > 
> > I don't know if all Unix systems have this issue, but I have been told
> > that Solaris at least has it.
> 
> Does Solaris enforces this "mount with same options" as default?

No. Solaris defaults to breaking cache consistency.

> > > "working" as in "I can mount the directory and do my work". And there
> > > has never been any problems as far as I know.
> > 
> > That is too narrow a definition: the minimum should be "everyone can
> > mount their directories and do their work". Your particular setup may
> > be safe, but that is why we have overrides: the default should be for the
> > kernel to be conservative, and to _tell_ users what it thinks is wrong.
> 
> Every engineer in our organization mounts it too. No problem until now.

I believe I've already explained why that isn't a sufficient metric.
What is your point?

> It's not very conservative to suddenly change default behavior and break
> autofs mounts. There is not even one kernel message that "_tells_ user why
> it thinks it's wrong". It just silently fails.

No it doesn't. It reports an error code to the caller. If autofs is
failing silently, then that is a bug in autofs: mount will report the
error to the user.

Trond

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