Comment 56 for bug 506798

Confirmed...same behavior in rawhide too. I can also reproduce this with a non-netapp server simply by exporting a filesystem and then exporting another filesystem mounted onto a subdir of the first fs. Nothing netapp-specific here.

There's also a somewhat related problem...if a submount is done and then gets automatically unmounted, then the device numbers can change and even be reused for a completely different submount.

This is a bit tricky. On the one hand, the device number seems to change and that's probably bad for some apps. On the other hand, do we really want to trigger a mount just because someone did a stat() on the directory where we would eventually do a submount?

If I have a ton of exports that are subdirs of another exported filesystem I don't think I really want to do submounts of all of those filesystems just because someone did a "ls -l" in that directory.

Unfortunately, the device numbers for NFS are allocated on the fly during mount. So we can't easily "fake up" the device numbers and expect them to remain consistent without actually triggering a mount. The device number may be different once the submount gets done.

I suspect that the best we can probably do is to just make sure the device number is different from that of the parent filesystem, but we probably won't be able to make it consistent. That is, it'll change as soon as you walk into the dir...

I'll plan to do a writeup of this problem in the near future and post it to the upstream mailing list.