On Thu, 2 Sept 2021 at 09:18, Christoph Hellwig <hch@xxxxxxxxxxxxx> wrote: > > Your attitude seems to be that this is a btrfs problem and must be > > fixed in btrfs. > > Yes. st_ino space issues affect overlayfs as well. The two problems are not the same, but do share some characteristics. And this limitation will likely come up again in the future. I suspect the long term solution would involve introducing new userspace API (variable length inode numbers) and deprecating st_ino. E.g. make stat return an error if the inode number doesn't fit into st_ino and add a statx extension to return the full number. But this would be a long process... Thanks, Miklos