Re: [PATCH RFC v2] fhandle: expose u64 mount id to name_to_handle_at(2)

On Tue, May 28, 2024 at 03:55:29AM -0700, Christoph Hellwig wrote:

On Tue, May 28, 2024 at 11:17:58AM +0200, Christian Brauner wrote:

quoted

As I've said earlier, independent of the new handle type returning the
new mount id is useful and needed because it allows the caller to
reliably generate a mount fd for use with open_by_handle_at() via
statmount(). That won't be solved by a new handle type and is racy with
the old mount id. So I intend to accept a version of this patch.

The whole point is that with the fsid in the handle we do not even need
a mount fd for open_by_handle_at.

Can you please explain how opening an fd based on a handle returned from
name_to_handle_at() and not using a mount file descriptor for
open_by_handle_at() would work?