From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marco Subject: Re: [PATCH 00/14] Pramfs: Persistent and protected ram filesystem Date: Mon, 15 Jun 2009 19:42:54 +0200 Message-ID: <4A36881E.8010009@gmail.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: Artem Bityutskiy , Daniel Walker , Jamie Lokier , Linux Embedded , Linux FS Devel , Linux Kernel To: Bryan Henderson Return-path: Received: from mail-bw0-f213.google.com ([209.85.218.213]:54822 "EHLO mail-bw0-f213.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752781AbZFORqv (ORCPT ); Mon, 15 Jun 2009 13:46:51 -0400 In-Reply-To: Sender: linux-fsdevel-owner@vger.kernel.org List-ID: Bryan Henderson wrote: >> Marco wrote: >>> To enable direct >>> I/O at all times for all regular files requires either that >>> applications be modified to include the O_DIRECT flag on all file >>> opens, or that a new filesystem be used that always performs direct >>> I/O by default." >> This could be done as well by just introducing a "direct_io_only" >> mount option to a file-system which would need this feature. > > But it's possible that there's just no advantage to having a block device > in the stack here. When unix block devices were invented, their main > purpose was that they could reorder reads and writes and do buffering and > caching -- all things essential for disk drives. We don't want to stretch > the concept too far. > Yes I agree, we can't in this case talk about read and write reordering, buffering and caching because we're talking about something completely different from a classic disk. The issues of this kind of fs are more similar to the tmpfs issues. Marco