In summary, I was very upset to find that five years later:
quotas were still 32-bit.
I am happy to report that this is no longer the case. Kirk McKusick has provided patches for both the kernel and the userland tools:
His instructions are as follows:
If you extract the tar file in your /usr directory, everything will be dropped into its appropriate location.
Once the files are in their appropriate locations, you need to rebuild your kernel (ensuring that you have the QUOTA option defined in your kernel configuration file). You will have to build, install, and boot your updated kernel. You then need to build and install the six quota related utilities: sbin/quotacheck, usr.sbin/edquota, usr.sbin/repquota, usr.sbin/quotaon, usr.bin/quota, and libexec/rpc.rquotad.
The first step to using the new quota code is to convert any existing quota files to the new quota file format. Conversion is done by running quotacheck which will automatically convert any old format files that it encounters. BE SURE TO SAVE OLD COPIES OF YOUR QUOTA FILES, as there is no provision for reversing the conversion process. So, if for whatever reason you need/want to revert to the old quota system, you will need to put back your saved copies of the quota files.
After running `quotacheck -a -v' you should then be able to operate quotas in the same way that you are used to doing.
I have tested these patches on both 6.x and 7.x using filesystems and quotas larger than three terabytes. This code is now in production use at rsync.net.
Kirk had this to say about the near-term progress of this code into actual FreeBSD releases:
I will proceed to check it into 8-CURRENT.
I will then apply to get permission to MFC it to 7-STABLE which should
be proforma with about a 1-month waiting period. I can also apply for
MFC to 6-STABLE, though I expect that request to be turned down as the
criterion for MFCs to 6-STABLE is bug fixes only and not enhancements.
And this change would be hard to classify as a bug fix.
In addition to the $1000 bounty that I will be paying to Kirk, he will receive a lifetime of free rsync.net service. Please join me in thanking him for all of the work that he has done, and continues to do for the FreeBSD community.