On Wed, Mar 24, 2021 at 08:53:25AM +0200, Amir Goldstein wrote: > > This also means that userspace can be entirely filesystem agnostic > > and it doesn't need to rely on parsing proc files to translate > > ephemeral mount IDs to paths, statvfs() and hoping that f_fsid is > > stable enough that it doesn't get the destination wrong. It also > > means that fanotify UAPI probably no longer needs to supply a > > f_fsid with the filehandle because it is built into the > > filehandle.... > > > > That is one option. Let's call it the "bullet proof" option. > > Another option, let's call it the "pragmatic" options, is that you accept > that my patch shouldn't break anything and agree to apply it. Your patch may very well break something. Most Linux file systems do store the dev_t in the fsid and userspace may for whatever silly reasons depend on it. Also trying to use the fsid for anything persistent is plain stupid, 64-bits are not enough entropy for such an identifier. You at least need a 128-bit UUID-like identifier for that. So I think this whole discussion is going in the wrong direction. Is exposing a stable file system identifier useful? Yes, for many reasons. Is repurposing the fsid for that a good idea? Hell no.
