Theodore Y. Ts'o [off-list ref] wrote:

Even *with* file system support, there's no way today for the VFS to
keep track of whether a pathname resolution came through one
mountpoint or another, so I can't do something like this:

Ummm...  Isn't that encoded in the vfsmount pointer in struct path?

However, the case folding stuff - is that a superblockism of a mountpointism?

So if the file system has been mounted with one set of mount options,
and you want to try to mount it with a conflicting set of mount
options and you don't want it to silently ignore the mount options,
the *only* thing we can today is to refuse the mount and return an
error.  

With fsopen() there is the option to have the filesystem and the LSM attempt
to compare the non-key[*] mount options and reject the attempt to share if
they differ in any way.

David


[*] sget lookup keys, that is.