On Wed, Mar 24, 2021 at 11:18:36AM +0200, Amir Goldstein wrote: > On Wed, Mar 24, 2021 at 9:43 AM Christoph Hellwig <hch@xxxxxxxxxxxxx> wrote: > > > > 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. > > > > I acknowledge that. > I do not claim that my change carries zero risk of breakage. > However, if such userspace dependency exists, it would break on ext4, > btrfs, ocsf2, ceph and many more fs, so it would have to be a > dependency that is tightly coupled with a specific fs. > The probability of that is rather low IMO. > > I propose an opt-in mount option "-o fixed_fsid" for this behavior to make > everyone sleep better. Layering hacks on top of hacks to avoid fixing the fanotify UAPI limitations isn't a very palatable option. Especially those that require adding mount options we'll have to support forever more... Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx
