From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751620AbbFNFmt (ORCPT ); Sun, 14 Jun 2015 01:42:49 -0400 Received: from mail-oi0-f43.google.com ([209.85.218.43]:34356 "EHLO mail-oi0-f43.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750968AbbFNFmj (ORCPT ); Sun, 14 Jun 2015 01:42:39 -0400 Date: Sun, 14 Jun 2015 00:42:36 -0500 From: Tejun Heo To: Christoph Hellwig Cc: axboe@kernel.dk, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, lizefan@huawei.com, cgroups@vger.kernel.org, Alexander Viro , Jan Kara , linux-ext4@vger.kernel.org Subject: Re: [PATCH 2/3] vfs, writeback: replace FS_CGROUP_WRITEBACK with MS_CGROUPWB Message-ID: <20150614054236.GA9662@mtj.duckdns.org> References: <1434146254-26220-1-git-send-email-tj@kernel.org> <1434146254-26220-3-git-send-email-tj@kernel.org> <20150613161608.GA29414@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150613161608.GA29414@infradead.org> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, Christoph. On Sat, Jun 13, 2015 at 09:16:08AM -0700, Christoph Hellwig wrote: > On Fri, Jun 12, 2015 at 04:57:33PM -0500, Tejun Heo wrote: > > FS_CGROUP_WRITEBACK indicates whether a file_system_type supports > > cgroup writeback; however, different super_blocks of the same > > file_system_type may or may not support cgroup writeback depending on > > filesystem options. This patch replaces FS_CGROUP_WRITEBACK with a > > kernel-internal super_block->s_flags MS_CGROUPWB. The concatenated > > and abbreviated name is for consistency with other MS_* flags. > > Nak. As the uapi part makes it obvious the MS_ namespace is part > of the userspace ABI. Please add a new in-kernel flags field instead. Are MS_ACTIVE and MS_BORN part of userpace ABI? They seem pretty internal. I don't mind introducing a new internal flag field but it's weird to put this single flag there with other internal flags in ->s_flags. Assuming we add a new field, how do sb->s_iflags and SB_I_XXX sound? Any better suggestions? Thanks. -- tejun