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

On Mon, 2020-08-03 at 12:49 +0100, David Howells wrote:

Miklos Szeredi [off-list ref] wrote:

quoted

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