From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S265053AbUGGLMi (ORCPT ); Wed, 7 Jul 2004 07:12:38 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S265054AbUGGLMi (ORCPT ); Wed, 7 Jul 2004 07:12:38 -0400 Received: from fw.osdl.org ([65.172.181.6]:51437 "EHLO mail.osdl.org") by vger.kernel.org with ESMTP id S265053AbUGGLMf (ORCPT ); Wed, 7 Jul 2004 07:12:35 -0400 Date: Wed, 7 Jul 2004 04:10:59 -0700 From: Andrew Morton To: jim.houston@comcast.net Cc: kevcorry@us.ibm.com, linux-kernel@vger.kernel.org, dm-devel@redhat.com, torvalds@osdl.org, agk@redhat.com Subject: Re: [PATCH] 1/1: Device-Mapper: Remove 1024 devices limitation Message-Id: <20040707041059.17287591.akpm@osdl.org> In-Reply-To: <1089197914.986.17.camel@new.localdomain> References: <200407011035.13283.kevcorry@us.ibm.com> <200407021233.09610.kevcorry@us.ibm.com> <20040702124218.0ad27a85.akpm@osdl.org> <200407061323.27066.kevcorry@us.ibm.com> <20040706142335.14efcfa4.akpm@osdl.org> <1089151650.985.129.camel@new.localdomain> <20040706152817.38ce1151.akpm@osdl.org> <1089154845.985.164.camel@new.localdomain> <20040706161641.01c1bbce.akpm@osdl.org> <1089197914.986.17.camel@new.localdomain> X-Mailer: Sylpheed version 0.9.7 (GTK+ 1.2.10; i386-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Jim Houston wrote: > > On Tue, 2004-07-06 at 19:16, Andrew Morton wrote: > Jim Houston wrote: > > > > > > With out the test above an id beyond the allocated space will alias > > > to one that exists. Perhaps the highest id currently allocated is > > > 100, there will be two layers in the radix tree and the while loop > > > above will only look at the 10 least significant bits. If you call > > > idr_find with 1025 it will return the pointer associated with id 1. > > > > OK. > > > > > The patch I sent was against linux-2.6.7, so I missed the change to > > > MAX_ID_SHIFT. > > > > How about this? > > > > n = idp->layers * IDR_BITS; > > + if (id >= (1 << n)) > > + return NULL; > > + > > p = idp->top; > > + > > /* Mask off upper bits we don't use for the search. */ > > id &= MAX_ID_MASK; > > > > Hi Andrew, > > It's not quite right. If you want to keep a count in the upper bits > you have to mask off that count before checking if the id is beyond the > end of the allocated space. OK, I'll fix that up. But I don't want to keep a count in the upper bits! I want rid of that stuff altogether, completely, all of it. It just keeps on hanging around :( We should remove MAX_ID_* from the kernel altogether.