From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mathieu Desnoyers Subject: Re: [PATCH v7 15/16] openvswitch: use new hashtable implementation Date: Mon, 29 Oct 2012 14:35:10 -0400 Message-ID: <20121029183510.GA21114@Krystal> References: <1351450948-15618-1-git-send-email-levinsasha928@gmail.com> <1351450948-15618-15-git-send-email-levinsasha928@gmail.com> <20121029132931.GC16391@Krystal> <20121029155957.GB18834@Krystal> <20121029181648.GB20796@Krystal> <20121029182209.GB4066@htj.dyndns.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <20121029182209.GB4066-Gd/HAXX7CRxy/B6EtB590w@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dev-bounces-yBygre7rU0TnMu66kgdUjQ@public.gmane.org Errors-To: dev-bounces-yBygre7rU0TnMu66kgdUjQ@public.gmane.org To: Tejun Heo Cc: snitzer-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, neilb-l3A5Bk7waGM@public.gmane.org, fweisbec-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, Trond.Myklebust-HgOvQuBEEgTQT0dZR+AlfA@public.gmane.org, bfields-uC3wQj2KruNg9hUCZPvPmw@public.gmane.org, paul.gortmaker-CWA4WttNNZF54TAoqtyWWQ@public.gmane.org, dm-devel-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, agk-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, aarcange-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, rds-devel-N0ozoZBvEnrZJqsBc5GL+g@public.gmane.org, eric.dumazet-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, venkat.x.venkatsubra-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org, ccaulfie-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, mingo-X9Un+BFzKDI@public.gmane.org, dev-yBygre7rU0TnMu66kgdUjQ@public.gmane.org, ericvh-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, josh-iaAMLnmF4UmaiuxdJuQwMA@public.gmane.org, rostedt-nx8X9YLhiw1AfugRpC6u6w@public.gmane.org, teigland-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, Sasha Levin , axboe-tSWWG44O7X1aa/9Udqfwiw@public.gmane.org, linux-nfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, edumazet-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, ejt-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org, lw-BthXqXjhjHXQFUHtdCDX3A@public.gmane.org, akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org, torvalds-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org, davem-fT/PcQaiUtIeIZ0/mPfg9Q@public.gmane.org List-Id: dm-devel.ids * Tejun Heo (tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org) wrote: > Hello, > > On Mon, Oct 29, 2012 at 02:16:48PM -0400, Mathieu Desnoyers wrote: > > This is just one example in an attempt to show why different hash table > > users may have different constraints: for a hash table entirely > > populated by keys generated internally by the kernel, a random seed > > might not be required, but for cases where values are fed by user-space > > and from the NIC, I would argue that flexibility to implement a > > randomizable hash function beats implementation simplicity any time. > > > > And you could keep the basic use-case simple by providing hints to the > > hash_32()/hash_64()/hash_ulong() helpers in comments. > > If all you need is throwing in a salt value to avoid attacks, can't > you just do that from caller side? Scrambling the key before feeding > it into hash_*() should work, no? Yes, I think salting the "key" parameter would work. Thanks, Mathieu > > Thanks. > > -- > tejun -- Mathieu Desnoyers Operating System Efficiency R&D Consultant EfficiOS Inc. http://www.efficios.com From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: linux-nfs-owner@vger.kernel.org Received: from mail.openrapids.net ([64.15.138.104]:58959 "EHLO blackscsi.openrapids.net" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754860Ab2J2SfN (ORCPT ); Mon, 29 Oct 2012 14:35:13 -0400 Date: Mon, 29 Oct 2012 14:35:10 -0400 From: Mathieu Desnoyers To: Tejun Heo Cc: Sasha Levin , torvalds@linux-foundation.org, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, paul.gortmaker@windriver.com, davem@davemloft.net, rostedt@goodmis.org, mingo@elte.hu, ebiederm@xmission.com, aarcange@redhat.com, ericvh@gmail.com, netdev@vger.kernel.org, josh@joshtriplett.org, eric.dumazet@gmail.com, axboe@kernel.dk, agk@redhat.com, dm-devel@redhat.com, neilb@suse.de, ccaulfie@redhat.com, teigland@redhat.com, Trond.Myklebust@netapp.com, bfields@fieldses.org, fweisbec@gmail.com, jesse@nicira.com, venkat.x.venkatsubra@oracle.com, ejt@redhat.com, snitzer@redhat.com, edumazet@google.com, linux-nfs@vger.kernel.org, dev@openvswitch.org, rds-devel@oss.oracle.com, lw@cn.fujitsu.com Subject: Re: [PATCH v7 15/16] openvswitch: use new hashtable implementation Message-ID: <20121029183510.GA21114@Krystal> References: <1351450948-15618-1-git-send-email-levinsasha928@gmail.com> <1351450948-15618-15-git-send-email-levinsasha928@gmail.com> <20121029132931.GC16391@Krystal> <20121029155957.GB18834@Krystal> <20121029181648.GB20796@Krystal> <20121029182209.GB4066@htj.dyndns.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20121029182209.GB4066@htj.dyndns.org> Sender: linux-nfs-owner@vger.kernel.org List-ID: * Tejun Heo (tj@kernel.org) wrote: > Hello, > > On Mon, Oct 29, 2012 at 02:16:48PM -0400, Mathieu Desnoyers wrote: > > This is just one example in an attempt to show why different hash table > > users may have different constraints: for a hash table entirely > > populated by keys generated internally by the kernel, a random seed > > might not be required, but for cases where values are fed by user-space > > and from the NIC, I would argue that flexibility to implement a > > randomizable hash function beats implementation simplicity any time. > > > > And you could keep the basic use-case simple by providing hints to the > > hash_32()/hash_64()/hash_ulong() helpers in comments. > > If all you need is throwing in a salt value to avoid attacks, can't > you just do that from caller side? Scrambling the key before feeding > it into hash_*() should work, no? Yes, I think salting the "key" parameter would work. Thanks, Mathieu > > Thanks. > > -- > tejun -- Mathieu Desnoyers Operating System Efficiency R&D Consultant EfficiOS Inc. http://www.efficios.com From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx102.postini.com [74.125.245.102]) by kanga.kvack.org (Postfix) with SMTP id EEB4C6B0069 for ; Mon, 29 Oct 2012 14:35:12 -0400 (EDT) Date: Mon, 29 Oct 2012 14:35:10 -0400 From: Mathieu Desnoyers Subject: Re: [PATCH v7 15/16] openvswitch: use new hashtable implementation Message-ID: <20121029183510.GA21114@Krystal> References: <1351450948-15618-1-git-send-email-levinsasha928@gmail.com> <1351450948-15618-15-git-send-email-levinsasha928@gmail.com> <20121029132931.GC16391@Krystal> <20121029155957.GB18834@Krystal> <20121029181648.GB20796@Krystal> <20121029182209.GB4066@htj.dyndns.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20121029182209.GB4066@htj.dyndns.org> Sender: owner-linux-mm@kvack.org List-ID: To: Tejun Heo Cc: Sasha Levin , torvalds@linux-foundation.org, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, paul.gortmaker@windriver.com, davem@davemloft.net, rostedt@goodmis.org, mingo@elte.hu, ebiederm@xmission.com, aarcange@redhat.com, ericvh@gmail.com, netdev@vger.kernel.org, josh@joshtriplett.org, eric.dumazet@gmail.com, axboe@kernel.dk, agk@redhat.com, dm-devel@redhat.com, neilb@suse.de, ccaulfie@redhat.com, teigland@redhat.com, Trond.Myklebust@netapp.com, bfields@fieldses.org, fweisbec@gmail.com, jesse@nicira.com, venkat.x.venkatsubra@oracle.com, ejt@redhat.com, snitzer@redhat.com, edumazet@google.com, linux-nfs@vger.kernel.org, dev@openvswitch.org, rds-devel@oss.oracle.com, lw@cn.fujitsu.com * Tejun Heo (tj@kernel.org) wrote: > Hello, > > On Mon, Oct 29, 2012 at 02:16:48PM -0400, Mathieu Desnoyers wrote: > > This is just one example in an attempt to show why different hash table > > users may have different constraints: for a hash table entirely > > populated by keys generated internally by the kernel, a random seed > > might not be required, but for cases where values are fed by user-space > > and from the NIC, I would argue that flexibility to implement a > > randomizable hash function beats implementation simplicity any time. > > > > And you could keep the basic use-case simple by providing hints to the > > hash_32()/hash_64()/hash_ulong() helpers in comments. > > If all you need is throwing in a salt value to avoid attacks, can't > you just do that from caller side? Scrambling the key before feeding > it into hash_*() should work, no? Yes, I think salting the "key" parameter would work. Thanks, Mathieu > > Thanks. > > -- > tejun -- Mathieu Desnoyers Operating System Efficiency R&D Consultant EfficiOS Inc. http://www.efficios.com -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org