From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail172.messagelabs.com (mail172.messagelabs.com [216.82.254.3]) by kanga.kvack.org (Postfix) with SMTP id DB8B96B009E for ; Mon, 28 Sep 2009 12:12:56 -0400 (EDT) Received: from m1.gw.fujitsu.co.jp ([10.0.50.71]) by fgwmail7.fujitsu.co.jp (Fujitsu Gateway) with ESMTP id n8SGE5AX031504 for (envelope-from kamezawa.hiroyu@jp.fujitsu.com); Tue, 29 Sep 2009 01:14:05 +0900 Received: from smail (m1 [127.0.0.1]) by outgoing.m1.gw.fujitsu.co.jp (Postfix) with ESMTP id E5AF945DE50 for ; Tue, 29 Sep 2009 01:14:04 +0900 (JST) Received: from s1.gw.fujitsu.co.jp (s1.gw.fujitsu.co.jp [10.0.50.91]) by m1.gw.fujitsu.co.jp (Postfix) with ESMTP id C2C9545DE4F for ; Tue, 29 Sep 2009 01:14:04 +0900 (JST) Received: from s1.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s1.gw.fujitsu.co.jp (Postfix) with ESMTP id A8C1E1DB803F for ; Tue, 29 Sep 2009 01:14:04 +0900 (JST) Received: from ml13.s.css.fujitsu.com (ml13.s.css.fujitsu.com [10.249.87.103]) by s1.gw.fujitsu.co.jp (Postfix) with ESMTP id 40C021DB8041 for ; Tue, 29 Sep 2009 01:14:04 +0900 (JST) 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" MIME-Version: 1.0 Content-Type: text/plain;charset=iso-2022-jp Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org To: Hugh Dickins Cc: KAMEZAWA Hiroyuki , Wu Fengguang , Nigel Cunningham , LKML , "linux-mm@kvack.org" List-ID: 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, 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