From: Christoph Hellwig Subject: Re: [PATCH 4/5] ext4: add isolated project support Date: Thu, 11 Mar 2010 07:07:47 -0500 Message-ID: <20100311120747.GD4706@infradead.org> References: <1267727677-11956-1-git-send-email-dmonakhov@openvz.org> <1267727677-11956-2-git-send-email-dmonakhov@openvz.org> <1267727677-11956-3-git-send-email-dmonakhov@openvz.org> <1267727677-11956-4-git-send-email-dmonakhov@openvz.org> <1267727677-11956-5-git-send-email-dmonakhov@openvz.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org To: Dmitry Monakhov Return-path: Received: from bombadil.infradead.org ([18.85.46.34]:43542 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757707Ab0CKMHs (ORCPT ); Thu, 11 Mar 2010 07:07:48 -0500 Content-Disposition: inline In-Reply-To: <1267727677-11956-5-git-send-email-dmonakhov@openvz.org> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Thu, Mar 04, 2010 at 09:34:36PM +0300, Dmitry Monakhov wrote: > PROJECT_ISOLATION > This feature allows to create an isolated project subtrees. > Isolation means what: > 1) directory subtree has no common inodes (no hadlinks across subtrees) > 2) All descendants belongs to the same subtree. > > Project subtree's isolation assumptions: > 1)Inode can not belongs to different subtree trees > Otherwise changes in one subtree result in changes in other subtree > which contradict to isolation criteria. > > *Usage* > We already has bind mounts which prevent link/remount across mounts. > But if user has isolated project which consists of several subtrees > and he want link/renames to work between subtrees(but in one project) > > Since this feature is non obvious it controlled by mount option. Making this a mount option is even more non-obvious. Unless you have very good reason to support both and not just stick to the existing "isolated" semantics make it a chattr option so we can easily check out what kind of subtree we deal with.