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Date: Sun, 22 Jan 2012 19:53:26 -0500 (EST)
From: Rick Macklem <rmacklem@uoguelph.ca>
To: freebsd-fs@freebsd.org
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Subject: should mount -u fail or silently ignore options?
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X-List-Received-Date: Mon, 23 Jan 2012 00:53:27 -0000

Hi,

There is a bug in the NFS clients, where a
"mount -u -o udp /mnt" will cause any threads
that have an RPC in progress to hang, if the
mount previously was using too large an rsize/wsize.

This case can easily be detected in nfs_mount().

However, my question is...
- Should the "mount -u" fail and return an error
OR
  Silently ignore the "udp" option and return ok.

I ask because the NFS clients currently silently
clear flags like NFSMNT_NFSV3 and NFSMNT_NOLOCKD
because they can't be changed and then nfs_mount()
returns 0, assuming any other options work.

I am also not sure if having a "mount -u" fail for a
diskless root fs will result in serious problems.
(I don't currently have a diskless root setup to try
 this on.)

Any comments w.r.t. which is the preferred way to
handle this?

rick