From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: Re: silent semantic changes with reiser4 Date: Thu, 26 Aug 2004 18:23:54 +0200 Message-ID: <20040826162354.GA4891@lst.de> References: <20040825152805.45a1ce64.akpm@osdl.org> <412D9FE6.9050307@namesys.com> <20040826014542.4bfe7cc3.akpm@osdl.org> <1093522729.9004.40.camel@leto.cs.pocnet.net> <20040826124929.GA542@lst.de> <1093525234.9004.55.camel@leto.cs.pocnet.net> <20040826130718.GB820@lst.de> <20040826144422.GD5733@mail.shareable.org> <20040826160306.GA4326@lst.de> <20040826161911.GK5733@mail.shareable.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Christoph Hellwig , Christophe Saout , Andrew Morton , Hans Reiser , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, flx@namesys.com, torvalds@osdl.org, reiserfs-list@namesys.com Return-path: list-help: list-unsubscribe: list-post: Errors-To: flx@namesys.com To: Jamie Lokier Content-Disposition: inline In-Reply-To: <20040826161911.GK5733@mail.shareable.org> List-Id: linux-fsdevel.vger.kernel.org On Thu, Aug 26, 2004 at 05:19:11PM +0100, Jamie Lokier wrote: > Remember that reiser4 allows you to operate on little pieces of data, > glueing and rearranging them inside files (something like that). > > No other filesystem has that capability, and it's a data model which > the fancy features (when they exist) will use. > > You can map those pieces to underlying directories and files and > renames and unlinks, so that the fancy stuff works on other > filesystems, but it would be a useless model because those other > filesystems wouldn't be recognisably "ordinary" files any more. > > For reiser4 to expose that model through a VFS interface, and the > fancy stuff to use it through the VFS interface, and for the fancy > stuff to work (even imperfectly) on other filesystems which don't > offer those operations, some kind of fall-back "store metadata and > fragment rearrangements in auxiliary files with special names" layer > would be requied. That's a big job. I seem to miss those files in the current implementation. But again the big question is how will the interface look? If the smaller objects interact with normal files (link/rename, contained in normal directories), they will have to obey the same locking protocols. If not a filesystem could experiment with it of course.