Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758673AbaDVVPt (ORCPT ); Tue, 22 Apr 2014 17:15:49 -0400 Received: from mail-pb0-f49.google.com ([209.85.160.49]:45288 "EHLO mail-pb0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757680AbaDVVPp (ORCPT ); Tue, 22 Apr 2014 17:15:45 -0400 Message-ID: <5356DC0D.7090305@kernel.dk> Date: Tue, 22 Apr 2014 15:15:57 -0600 From: Jens Axboe User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.4.0 MIME-Version: 1.0 To: Jianyu Zhan CC: LKML Subject: Re: [PATCH] blk-cgroup: explicitly init the early_init field References: <1398144370-9236-1-git-send-email-nasa4836@gmail.com> <535679A4.4050507@kernel.dk> In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/22/2014 08:18 AM, Jianyu Zhan wrote: > On Tue, Apr 22, 2014 at 10:16 PM, Jens Axboe wrote: >> The rest of the members will be zero-filled by default, so your patch should >> not change anything. > > Hi, Jens > > I'm sorry I should have made this more clear. > > Sure, for this global variable struct, if not initailized, its all > fields will be initialized > to 0 or null(depending on its type). The point here is no to deprive > the rights of compiler/linker of doing this initialization, it is mainly for > documentation reason. Actually this field's value would affect how ->css_alloc > should implemented. > > Concretely, if early_init is nonzero, then ->css_alloc *must not* call kzalloc, > because in cgroup implementation, ->css_alloc will be called earlier before > mm_init(). > > I don't think that the value of one field(early_init) has a so subtle > restrition on the another field(css_alloc) is a good thing, but since > it is there, docment it should be needed. Then just add the comment instead. The fact the members following the last " = something," are zeroed is a common theme in the kernel, if you just add a patch that blindly (and unnecessarily) zeroes one other member, somebody else will likely find that odd and remove it again. To be honest, I don't see much of a need to do anything here, really. -- Jens Axboe -- 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/