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

On Fri, 2020-07-24 at 11:19 +0100, David Howells wrote:

David Howells [off-list ref] wrote:

quoted

quoted

What guarantees that mount_id is going to remain a 32bit entity?

You think it likely we'd have >4 billion concurrent mounts on a
system?  That
would require >1.2TiB of RAM just for the struct mount allocations.

But I can expand it to __u64.

That said, sys_name_to_handle_at() assumes it's a 32-bit signed
integer, so
we're currently limited to ~2 billion concurrent mounts:-/

I was wondering about id re-use.

Assuming that ids that are returned to the idr db are re-used
what would the chance that a recently used id would end up
being used?

Would that chance increase as ids are consumed and freed over
time?

Yeah, it's one of those questions ... ;)

Ian