On Wed, 2020-08-12 at 14:06 +0100, David Howells wrote: > Miklos Szeredi <miklos@xxxxxxxxxx> wrote: > > > That presumably means the mount ID <-> mount path mapping already > > exists, which means it's just possible to use the open(mount_path, > > O_PATH) to obtain the base fd. > > No, you can't. A path more correspond to multiple mounts stacked on > top of > each other, e.g.: > > mount -t tmpfs none /mnt > mount -t tmpfs none /mnt > mount -t tmpfs none /mnt > > Now you have three co-located mounts and you can't use the path to > differentiate them. I think this might be an issue in autofs, but > Ian would > need to comment on that. It is a problem for autofs, direct mounts in particular, but also for mount ordering at times when umounting a tree of mounts where mounts are covered or at shutdown. Ian
