On Tuesday, 22 September 2009 23:06:16 Eric Paris wrote:

this is true, if there is only one namespace subtree notification works
the same as global notification.

[...]

I don't see how subtree notification can possibly solve the global
notification problem.

I'm thinking of is something like this: A listener registers interest in "/", 
recursively. The kernel sets a FSNOTIFY_WATCH_RECURSIVE flag on "/" and each 
mount point below. Afterwards when something is mounted anywhere, same 
namespace or not, the kernel sets the new mount's FSNOTIFY_WATCH_RECURSIVE 
flag if the parent mount has this flag set.

(Of course we need per fsnotify_group flags and not global ones, but this 
doesn't change the principle.)

Andreas