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

Christoph Hellwig
2023-11-08T08:12:41Z

On Wed, Nov 08, 2023 at 09:09:10AM +0100, Christian Brauner wrote:
> > a bind mount can of course change the dev_t - if it points to a
> > different super block at the moment.
>
> No, a bind mount just takes an existing directory tree of an existing
> filesystem and makes it visible on some location in the filesystem
> hierarchy. It doesn't change the device number it will inherit it from
> the superblock it belongs.

That's what I'm trying to say.

So if you have:

/mnt/1/ with dev 8
/mnt/2/ with dev 23

then a bind mount of

/mnt/1/foo to /mnt/2/bar will get your dev 8 for /mnt/2/bar

So the device number changes at the mount point here, bind mount or not.