Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751486AbWAaVDF (ORCPT ); Tue, 31 Jan 2006 16:03:05 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751487AbWAaVDF (ORCPT ); Tue, 31 Jan 2006 16:03:05 -0500 Received: from smtp.osdl.org ([65.172.181.4]:59279 "EHLO smtp.osdl.org") by vger.kernel.org with ESMTP id S1751486AbWAaVDD (ORCPT ); Tue, 31 Jan 2006 16:03:03 -0500 Date: Tue, 31 Jan 2006 13:02:42 -0800 (PST) From: Linus Torvalds To: Hubertus Franke cc: "Eric W. Biederman" , Dave Hansen , Greg KH , Alan Cox , "Serge E. Hallyn" , Arjan van de Ven , Linux Kernel Mailing List , Cedric Le Goater Subject: Re: RFC [patch 13/34] PID Virtualization Define new task_pid api In-Reply-To: <43D14578.6060801@watson.ibm.com> Message-ID: References: <20060117143258.150807000@sergelap> <20060117143326.283450000@sergelap> <1137511972.3005.33.camel@laptopd505.fenrus.org> <20060117155600.GF20632@sergelap.austin.ibm.com> <1137513818.14135.23.camel@localhost.localdomain> <1137518714.5526.8.camel@localhost.localdomain> <20060118045518.GB7292@kroah.com> <1137601395.7850.9.camel@localhost.localdomain> <43D14578.6060801@watson.ibm.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2408 Lines: 49 (I'm coming in late, it's not been a high priority for me) On Fri, 20 Jan 2006, Hubertus Franke wrote: > > 2nd: > ==== Issue: we don't need pid virtualization, instead simply use > pair. > > This requires a bit more thought. Essentially that's what I was doing, > but I mangled them into the same pid and using masking to add/remove the > container for internal use. As pointed out by Alan(?), we can indeed > reused the same pid internally many times as long as we can distinguish > during the pid-to-task_struct lookup. This is easily done because, the > caller provides the context hence the container for the lookup. This is my preferred approach BY FAR. Doing a approach is very natural, and avoids almost all issues. At most, you might want to have a new system call (most naturally just the one that is limited to the "init container" - it the one that we boot up with) that can specify both container and pid explicitly, and see all processes and access all processes. But all "normal" system calls would only ever operate within their container. The fact is, we want "containers" anyway for any virtualization thing, ie vserver already adds them. And if we have containers, then it's very easy ("easyish") to split up the current static "pid_hash[]", "pidmap_array[]" and "pidmap_lock", and make them per-container, and have a pointer to the container for each "struct task_struct". After that, there wouldn't even be a lot else to do. The normal system calls would just use their own container, and the (few) places that save away pid's for later (ie things that use "kill_proc_info_as_uid()" and "struct fown_struct" friends) would have to also squirrell away the container, but then you should be pretty much done. Of course, you'll have to do the system calls to _create_ the containers in the first place, but that's at a higher level and involves much more than just the pid-space (ie a container would normally have more than just the uid mappings, it would have any network knowledge too etc - hostname, perhaps list of network devices associated with that context etc etc) Linus - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/