QSettings NFS synchronization issue

We're seeing strange results in our QSettings output files when we run nightly regressions. I've written a test application which I think replicates the problem. I'm running it on an amd64 machine.

If you run the attached app, click on "Run", and it will repeatedly read and write a settings file. After each pass, it writes the file size to its main window. Notice that the file size does not change.

Now run a second instance of the same app, and click "Run". The file size will begin to change occasionally, even though it should not since the same data is written by both instances of the application.

If you run more instances, you'll see that the file size becomes more unstable the more processes that access it.
We've had one case where one of our settings files in the nightly regression run went up to 1.5 gigabytes, causing
the regressions to essentially hang.

I found the problem to be much easier to reproduce when the size of the settings data was increased above the 30kbyte range. The test case writes a file of roughly 40kbytes.