On Thu, Oct 10, 2024 at 05:26:41PM +0200, Mickaël Salaün wrote:

When a filesystem manages its own inode numbers, like NFS's fileid shown
to user space with getattr(), other part of the kernel may still expose
the private inode->ino through kernel logs and audit.

Another issue is on 32-bit architectures, on which ino_t is 32 bits,
whereas the user space's view of an inode number can still be 64 bits.

Add a new inode_get_ino() helper calling the new struct
inode_operations' get_ino() when set, to get the user space's view of an
inode number.  inode_get_ino() is called by generic_fillattr().

I mean, you have to admit that this is a pretty blatant hack and that's
not worthy of a separate inode method, let alone the potential
performance implication that multiple people already brought up.