From: Andreas Gruenbacher <agruen@suse.de>
Organization: SUSE Labs / Novell
To: Eric Paris <eparis@redhat.com>
Subject: Re: fanotify as syscalls
Date: Tue, 22 Sep 2009 23:38:32 +0200
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Cc: Jamie Lokier <jamie@shareable.org>,
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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
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