Re: [PATCH 0/3] fanotify support for btrfs sub-volumes

Christoph Hellwig
2023-11-09T14:41:29Z

On Thu, Nov 09, 2023 at 10:07:35AM +0100, Christian Brauner wrote:
> > How? If they want to only rely on Posix and not just he historical
> > unix/linux behavior they need to compare st_dev for the inode and it's
> > parent to see if it the Posix concept of a mount point (not to be
> > confused with the Linux concept of a mountpoint apparently) because
> > that allows the file system to use a new inode number namespace.
>
> That doesn't work anymore. Both overlayfs and btrfs make this
> impossible or at least inconsistent.

One you hit a different st_dev on btrfs you'll stay on that until
you hit a mount point or another (nested) subvolume. Can't comment
on overlayfs. But if it keeps mixing things forth and back what would
the semantics of the flag be anyway?