Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S263010AbUKYHaw (ORCPT ); Thu, 25 Nov 2004 02:30:52 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S263008AbUKYHav (ORCPT ); Thu, 25 Nov 2004 02:30:51 -0500 Received: from rev.193.226.233.139.euroweb.hu ([193.226.233.139]:64981 "EHLO dorka.pomaz.szeredi.hu") by vger.kernel.org with ESMTP id S263007AbUKYHaW (ORCPT ); Thu, 25 Nov 2004 02:30:22 -0500 To: bulb@ucw.cz CC: avi@argo.co.il, alan@lxorguk.ukuu.org.uk, torvalds@osdl.org, hbryan@us.ibm.com, akpm@osdl.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, pavel@ucw.cz In-reply-to: <20041125062649.GB29278@vagabond> (message from Jan Hudec on Thu, 25 Nov 2004 07:26:49 +0100) Subject: Re: [PATCH] [Request for inclusion] Filesystem in Userspace References: <1100798975.6018.26.camel@localhost.localdomain> <41A47B67.6070108@argo.co.il> <20041125062649.GB29278@vagabond> Message-Id: From: Miklos Szeredi Date: Thu, 25 Nov 2004 08:29:58 +0100 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1249 Lines: 29 > > There are already "strange" filesystems in the kernel which cannot > > really get rid of dirty data. I'm thinking of tmpfs and ramfs. > > Neither of them are prone to deadlock, though both of them are "worse > > off" than a userspace filesystem, in the sense that they have not even > > the remotest chance of getting rid of the dirty data. > > > > Of course, implementing this is probably not trivial. But I don't see > > it as a theoretical problem as Linus does. > > > > Is there something which I'm missing here? > > But they KNOW that they won't be able to get rid of the dirty data. But > fuse does not. Why not? I can set bdi->memory_backed to 1 just like ramfs, implement my own writeback thread, and voila, no deadlock. Of course I believe, that it's probably easier to tweak the page cache to teach it that fuse pages _can_ be written back, but not reliably like a disk filesystem. And there's the small problem of limiting the number of writable pages allocated to FUSE. Miklos - 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/