Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757273AbYFQL5x (ORCPT ); Tue, 17 Jun 2008 07:57:53 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755494AbYFQL5m (ORCPT ); Tue, 17 Jun 2008 07:57:42 -0400 Received: from mtagate2.uk.ibm.com ([195.212.29.135]:50491 "EHLO mtagate2.uk.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754903AbYFQL5k convert rfc822-to-8bit (ORCPT ); Tue, 17 Jun 2008 07:57:40 -0400 Date: Tue, 17 Jun 2008 13:57:22 +0200 From: Maxim Shchetynin To: linux-fsdevel@vger.kernel.org Cc: Jan Engelhardt , Matthew Wilcox , linux-kernel@vger.kernel.org Subject: Re: AZFS file system proposal Message-ID: <20080617135722.374673b9@mercedes-benz.boeblingen.de.ibm.com> In-Reply-To: References: <20080609104650.4f220492@mercedes-benz.boeblingen.de.ibm.com> <20080609125530.GF30405@parisc-linux.org> <20080610104919.504b9826@mercedes-benz.boeblingen.de.ibm.com> <20080617110655.59c915da@mercedes-benz.boeblingen.de.ibm.com> Organization: IBM Deutschland Entwicklung GmbH X-Mailer: Claws Mail 2.10.0 (GTK+ 2.12.0; i486-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2183 Lines: 53 > >> (a) What is axonram? > >> (b) why is axonram direct_access, and my other devices (including > >> standard PC RAM) not? > > > >[Axonram is a module specific for IBM CellBlade and allows access to > >a DDR2 memory attached onto Axon controller.] You don't need > >direct_access and not azfs for main memory because there is already > >a pretty nice tmpfs for it. > > So the reason azfs could be useful is...? The "?" at the end of your sentence might mean a question. I would be really happy to give an answer on it if I could understand it. > >> >+ Mounting such device with azfs gives memory mapped > >> >access to the + underlying memory to user space. > >> > >> Can't I just mmap(/dev/theblockdevice), why would I need to go through > >> azfs? > > > >Yes, you can mmap it. But what does it have to do with a file system. > > Exactly, that's what I was asking myself. I am glad I could make you feel comfortable with that answer. > >I would say you can either mmap it or place a file system on it. > > The help text implies that I *need* azfs to mmap it - and that sounds > like a Rube Goldberg machine. Does it? If it is really so, then only because my english is not perfect. I didn't want to compel someone to do mmap or to disturb user's rights in any other way. By the way, you can also mmap some files on AZFS like on any other file system. But mmap wouldn't work if you mount AZFS with a block size less than the system page size. -- Mit freundlichen Grüßen / met vriendelijke groeten / avec regards Maxim V. Shchetynin Linux Kernel Entwicklung IBM Deutschland Entwicklung GmbH Linux für Cell, Abteilung 3250 Schönaicher Straße 220 71032 Böblingen Vorsitzender des Aufsichtsrats: Johann Weihen Geschäftsführung: Herbert Kircher Sitz der Gesellschaft: Böblingen Registriergericht: Amtsgericht Stuttgart, HRB 243294 Fahr nur so schnell wie dein Schutzengel fliegen kann! -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/