From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alex Zarochentsev Subject: Re: silent semantic changes with reiser4 Date: Mon, 30 Aug 2004 21:37:58 +0400 Message-ID: <20040830173757.GU5108@backtop.namesys.com> References: <20040826154446.GG5733@mail.shareable.org> <20040826165351.GM5733@mail.shareable.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Rik van Riel , 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: Jamie Lokier Content-Disposition: inline In-Reply-To: <20040826165351.GM5733@mail.shareable.org> List-Id: linux-fsdevel.vger.kernel.org On Thu, Aug 26, 2004 at 05:53:51PM +0100, Jamie Lokier wrote: > 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). :) would it be a tautology if I say that the streams implementation depends on (reiser4 now, may be vfs later) plugins? All proposals including user-level helpers, shadow caching/indexing may be implemented, why not? > 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 -- Alex.