From: Andreas Dilger Subject: Re: [PATCH 3/5] ext4: Implement project ID support for ext4 filesystem Date: Thu, 18 Mar 2010 15:25:00 -0600 Message-ID: <41219796-D9F2-4292-9284-E8D266EB3532@sun.com> References: <1268920970-9061-1-git-send-email-dmonakhov@openvz.org> <1268920970-9061-2-git-send-email-dmonakhov@openvz.org> <1268920970-9061-3-git-send-email-dmonakhov@openvz.org> <1268920970-9061-4-git-send-email-dmonakhov@openvz.org> Mime-Version: 1.0 Content-Type: text/plain; CHARSET=US-ASCII; delsp=yes; format=flowed Content-Transfer-Encoding: 7BIT Cc: linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org, tytso@mit.edu, hch@infradead.org, jack@suse.cz, david@fromorbit.com, viro@ZenIV.linux.org.uk, xemul@openvz.org To: Dmitry Monakhov Return-path: In-reply-to: <1268920970-9061-4-git-send-email-dmonakhov@openvz.org> Sender: linux-fsdevel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org On 2010-03-18, at 08:02, Dmitry Monakhov wrote: > * Disk layout > Project id is stored on disk inside xattr usually inside ibody. > Xattr is used only as a data storage, It has not user visible xattr > interface. > > * User interface > Project id is accessible via generic xattr interface > "system.project_id" > > +#define EXT4_XATTR_INDEX_PROJECT_ID 7 If you are making this attribute available to userspace via system.project_id, doesn't it make sense to store it on disk as system.project_id also (i.e. in the "system" namespace)? Alternately, the "trusted" namespace is already intended for use as "accessible only by root/kernel" semantics if this is what you are trying to achieve. I'm also with the statement "It has not user visible xattr interface" yet you also write "Project id is accessible via generic xattr interface". Why bother having this complexity when you are free to make the two identical? Cheers, Andreas -- Andreas Dilger Sr. Staff Engineer, Lustre Group Sun Microsystems of Canada, Inc.