From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jamie Lokier Subject: Re: silent semantic changes with reiser4 Date: Thu, 26 Aug 2004 17:53:51 +0100 Message-ID: <20040826165351.GM5733@mail.shareable.org> References: <20040826154446.GG5733@mail.shareable.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Christophe Saout , Denis Vlasenko , Christer Weinigel , Spam , Andrew Morton , wichert@wiggy.net, jra@samba.org, torvalds@osdl.org, reiser@namesys.com, hch@lst.de, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, flx@namesys.com, reiserfs-list@namesys.com Return-path: list-help: list-unsubscribe: list-post: Errors-To: flx@namesys.com To: Rik van Riel Content-Disposition: inline In-Reply-To: List-Id: linux-fsdevel.vger.kernel.org Rik van Riel wrote: > And if an unaware application reads the compound file > and then writes it out again, does the filesystem > interpret the contents and create the other streams ? Yes, exactly that. The streams are created on demand of course, and by userspace helpers when that's appropriate which I suspect it almost always is. > Unless I overlook something (please tell me what), the > scheme just proposed requires filesystems to look at > the content of files that is being written out, in > order to make the streams work. Yes. Hence the idea of coherent views between two files: writing to one affects the content of the other, although the calcalation is only done on demand (or when the fs wants to migrate the representation -- for example, creating the flat container prior to deleting the regeneratable pieces in order to save space). I haven't seen anything from Namesys that says they'll do that. I have the impression the streams are just generated in memory on the fly, not stored on disk with a cacheing policy, but that's just an impression. (We've all seen the Namesys white papers, they're not _that_ revealing). :) I'm just pointing out how to do it _right_. I think it will turn out like this eventually, either next year or some time over the next decade after some iterations. Inevitable. Mark my words, etc. :) -- Jamie