Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756453AbYCNDJ0 (ORCPT ); Thu, 13 Mar 2008 23:09:26 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751700AbYCNDJT (ORCPT ); Thu, 13 Mar 2008 23:09:19 -0400 Received: from rv-out-0910.google.com ([209.85.198.189]:14545 "EHLO rv-out-0910.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751143AbYCNDJS (ORCPT ); Thu, 13 Mar 2008 23:09:18 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; b=f4BqWbokEcnb6A0nt5j08Kd+nDqrTcxdIbkXxdcgQt1u7+nsx7GbyO/CBzvEtAjX9DUyjqVnqGylHOXDeSn6yukTca7VpHSabOCE2CUgUzG+7hx2+6Af/Ow6KvmTX1ieFAHfihf7P9wgLLb4I3rJew+CyXT8jOgYvIGz+rgTn4c= Message-ID: <86802c440803132009q40291587i7a9f41c686f0f10b@mail.gmail.com> Date: Thu, 13 Mar 2008 20:09:16 -0700 From: "Yinghai Lu" To: "Johannes Weiner" Subject: Re: [PATCH] mm: make reserve_bootmem can crossed the nodes Cc: "Andrew Morton" , "Ingo Molnar" , "Andi Kleen" , "Christoph Lameter" , linux-kernel@vger.kernel.org, "Yasunori Goto" , "KAMEZAWA Hiroyuki" In-Reply-To: <874pba3tny.fsf@saeurebad.de> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <86802c440803131645q1eb31cb7jb0774d9cf67c767@mail.gmail.com> <87iqzq40yd.fsf@saeurebad.de> <86802c440803131804w1173b9b5n9d9f2d85c98b8901@mail.gmail.com> <874pba3tny.fsf@saeurebad.de> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2751 Lines: 71 On Thu, Mar 13, 2008 at 7:50 PM, Johannes Weiner wrote: > > Hi, > > "Yinghai Lu" writes: > > > On Thu, Mar 13, 2008 at 5:13 PM, Johannes Weiner wrote: > >> Hi, > >> > >> "Yinghai Lu" writes: > >> > > > >> > static void __init free_bootmem_core(bootmem_data_t *bdata, unsigned long addr, > >> > @@ -407,6 +432,11 @@ unsigned long __init init_bootmem_node(p > >> > void __init reserve_bootmem_node(pg_data_t *pgdat, unsigned long physaddr, > >> > unsigned long size, int flags) > >> > { > >> > + int ret; > >> > + > >> > + ret = can_reserve_bootmem_core(pgdat->bdata, physaddr, size, flags); > >> > + if (ret < 0) > >> > + return; > >> > reserve_bootmem_core(pgdat->bdata, physaddr, size, flags); > >> > >> I don't get it. Sorry. What is the purpose of > >> can_reserve_bootmem_core()? It does exactly what reserve_bootmem_core > >> does besides actually setting the bits. All the pre-checking you wanted > >> to have out of the way is repeated again in reserve_bootmem_core() > >> (well, almost all). > > > > can_reserve_bootmem_core is check if there is some pages is reserved > > already with > >> > + if (flags & BOOTMEM_EXCLUSIVE) > >> > + return -EBUSY; > > > > so it will avoid the restoring later. > > Yes, I understood that. But you skipped the lower part of my email: > > Your current state now is _not_ that you have one function that > prechecks the range and another function that reserves it! You have > _two_ functions checking the range and the second reserving it. Yes > > Why double-check most of the things? If you want to have a pre-check > function, _move_ all the pre-checks into another function, not > copy-paste them. for cross the nodes > > And is the condition of trying to reserve a range twice, the second time > exclusively, so common that it is worth iterating twice over the nodes > (once for checking, once for reserving) instead of just unwinding the > reservation if it fails in between? > > On something else: is there a bug when a memory range is reserved with > BOOTMEM_EXCLUSIVE and then again without this flag? The second call > does not return an error then. Yes. only provide one direction protection. so always make sure crash_kernel reserve_bootmem as the last. that is doable. YH -- 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/