From: Neil Brown <neilb@cse.unsw.edu.au>,

From: Miquel van Smoorenburg <miquels@cistron.nl>

While I was stress-testing NFS/XFS on 2.6.1/2.6.2-rc, I found that
sometimes my "dd" would exit with:

	#  dd if=/dev/zero bs=4096 > /mnt/file
	dd: writing `standard output': Invalid argument
	1100753+0 records in
	1100752+0 records out

After adding some debug printk's to the server and client code and some
tcpdump-ing, I found that the NFSERR_INVAL was returned by nfsd_commit on
the server.

Turns out that the "offset" argument is off_t instead of loff_t.  It isn't
used at all (unfortunately), but it _is_ checked for sanity, so that's
where the error came from.