Re: [PATCH 13/17] watch_queue: Implement mount topology and attribute change notifications [ver #5]

[Ian Kent]

On Mon, 2020-08-03 at 12:49 +0100, David Howells wrote:
> Miklos Szeredi <miklos@xxxxxxxxxx> wrote:
> 
> > OTOH mount notification is way smaller and IMO a more mature
> > interface.  So just picking the unique ID patch into this set might
> > make sense.
> 
> But userspace can't retrieve the unique ID without fsinfo() as things
> stand.
> 
> I'm changing it so that the fields are 64-bit, but initialised with
> the
> existing mount ID in the notifications set.  The fsinfo set changes
> that to a
> unique ID.  I'm tempted to make the unique IDs start at UINT_MAX+1 to
> disambiguate them.

Mmm ... so what would I use as a mount id that's not used, like NULL
for strings?

I'm using -1 now but changing this will mean I need something
different.

Could we set aside a mount id that will never be used so it can be
used for this case?

Maybe mount ids should start at 1 instead of zero ...

Ian