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

hch
2024-05-27T16:29:49Z

On Mon, May 27, 2024 at 03:38:40PM +0000, Trond Myklebust wrote:
> > It
> > does not matter what mount you use to access it.
>
> Sure. However if you are providing a path argument, then presumably you
> need to know which file system (aka super_block) it eventually resolves
> to.

Except that you can't, at least not without running into potential
races. The only way to fix a race vs unmount/remount is to include
the fsid part in the kernel generated file handle.

>
> If your use case isn't NFS servers, then what use case are you
> targeting, and how do you expect those applications to use this API?

The main user of the open by handle syscalls seems to be fanotify
magic.