Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752464AbZI1QOF (ORCPT ); Mon, 28 Sep 2009 12:14:05 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751811AbZI1QOE (ORCPT ); Mon, 28 Sep 2009 12:14:04 -0400 Received: from fgwmail7.fujitsu.co.jp ([192.51.44.37]:58865 "EHLO fgwmail7.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751711AbZI1QOD (ORCPT ); Mon, 28 Sep 2009 12:14:03 -0400 Message-ID: In-Reply-To: References: <4AB9A0D6.1090004@crca.org.au> <20090924100518.78df6b93.kamezawa.hiroyu@jp.fujitsu.com> <4ABC80B0.5010100@crca.org.au> <20090925174009.79778649.kamezawa.hiroyu@jp.fujitsu.com> <4AC0234F.2080808@crca.org.au> <20090928120450.c2d8a4e2.kamezawa.hiroyu@jp.fujitsu.com> <20090928033624.GA11191@localhost> <20090928125705.6656e8c5.kamezawa.hiroyu@jp.fujitsu.com> Date: Tue, 29 Sep 2009 01:14:03 +0900 (JST) Subject: Re: No more bits in vm_area_struct's vm_flags. From: "KAMEZAWA Hiroyuki" To: "Hugh Dickins" Cc: "KAMEZAWA Hiroyuki" , "Wu Fengguang" , "Nigel Cunningham" , "LKML" , "linux-mm@kvack.org" User-Agent: SquirrelMail/1.4.16 MIME-Version: 1.0 Content-Type: text/plain;charset=iso-2022-jp Content-Transfer-Encoding: 8bit X-Priority: 3 (Normal) Importance: Normal Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1052 Lines: 36 Hugh Dickins wrote: > On Mon, 28 Sep 2009, KAMEZAWA Hiroyuki wrote: >> >> What I dislike is making vm_flags to be long long ;) > > Why? I'm sorry if my "dislike" sounds too strong. Every time I see long long in the kernel, my concern is "do I need spinlock to access this for 32bit arch ? is it safe ?". (And it makes binary=>disassemble=>C (by eyes) a bit difficult) Then, I don't like long long personally. Another reason is some other calls like test_bit() cannot be used against long long. (even if it's not used _now_) Maybe vm->vm_flags will not require extra locks because it can be protected by bigger lock as mmap_sem. Then, please make it to be long long if its's recommended. keeping vm_flags to be 32bit may makes vma_merge() ugly. If so, long long is a choice. Thanks, -Kame > Hugh > -- 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/