Return-Path: linux-nfs-owner@vger.kernel.org Received: from mail-pa0-f46.google.com ([209.85.220.46]:53870 "EHLO mail-pa0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756842Ab2J2SWP (ORCPT ); Mon, 29 Oct 2012 14:22:15 -0400 Date: Mon, 29 Oct 2012 11:22:09 -0700 From: Tejun Heo To: Mathieu Desnoyers 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: <20121029182209.GB4066@htj.dyndns.org> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20121029181648.GB20796@Krystal> Sender: linux-nfs-owner@vger.kernel.org List-ID: 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? Thanks. -- tejun