Comment 72 for bug 506798

I'd have to look at the example more closely, but it's likely that the kernel code is picking up the inode number of the root inode of the underlying filesystem.

I think what's happening is that the server sends the inode number of /tmp/mnt/home and a new fsid, but the client doesn't actually spawn a new submount there. So the device ID ends up the same. In fact, all of my ext3/4 filesystems seem to give the root inode st_ino == 2, so that's probably what's happening.

The trivial workaround here is to probably use stat() instead of lstat() here (-L option to the stat program), but I imagine that won't be suitable?

How to fix this? I don't think there is a way to do so without triggering a submount even when we don't want to follow symlinks.

That's going to be very costly for performance in many cases (if it's even reasonably doable). Imagine cd'ing into a directory that has a 1000 exported filesystems under it. Simply doing a readdir() in there is going to make the client spawn 1000 new mounts.