From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Zijlstra Subject: Re: fanotify - overall design before I start sending patches Date: Thu, 06 Aug 2009 12:29:08 +0200 Message-ID: <1249554548.32113.137.camel@twins> References: <1248466429.3567.82.camel@localhost> <20090805020534.GB1354@ucw.cz> <200908051746.17903.tvrtko.ursulin@sophos.com> <20090806101059.GD31370@elf.ucw.cz> <4A7AAE89.20205@sophos.com> Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Cc: Pavel Machek , Tvrtko Ursulin , Eric Paris , "linux-kernel@vger.kernel.org" , "linux-fsdevel@vger.kernel.org" , "malware-list@dmesg.printk.net" , "Valdis.Kletnieks@vt.edu" , "greg@kroah.com" , "jcm@redhat.com" , "tytso@mit.edu" , "arjan@infradead.org" , "david@lang.hm" , "jengelh@medozas.de" , "aviro@redhat.com" , "mrkafk@gmail.com" , "alexl@redhat.com" , "hch@infradead.org" , "alan@lxorguk.ukuu.org.uk" , "mmorley@hcl.in" To: Douglas Leeder Return-path: In-Reply-To: <4A7AAE89.20205@sophos.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On Thu, 2009-08-06 at 11:20 +0100, Douglas Leeder wrote: > Pavel Machek wrote: > > On Wed 2009-08-05 17:46:16, Tvrtko Ursulin wrote: > >> On Wednesday 05 August 2009 03:05:34 Pavel Machek wrote: > > >> Just to make sure you haven't missed this - it is not that they have to > >> complete the whole operation before the timeout period (since you mention > >> realtime/mlock I suspect this is what you think?), but _during_ the operation > >> they have to show that they are active by sending something like keep alive > >> messages. > >> > >> Or you are worried about failing to meet even that on a loaded system? There > >> has to be something like this otherwise hung userspace client would kill the > >> whole system. > > > > Of course, I'm worried about failing to meet this on loaded > > system. And the fact that I _have_ to worry about that means that > > interface is ugly/broken. > > You mean that in 5 seconds, you won't have any point when you can tell > the kernel, "I'm still working"? I have to agree with Pavel here, either you demand the monitor process is RT/mlock and can respond in time, in which case the interface doesn't need a 5 second timeout, or you cannot and you have a hole somewhere. Now having the kernel depend on any user task to guarantee process is of course utterly insane too. Sounds like a bad place to be, and I'd rather not have it. If you really need the intermediate you might as well use a FUSE filesystem, but I suspect there's plenty of problems there as well. It all reeks of ugly though.. /me craws back from whence he came.