Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752278AbaKQKcK (ORCPT ); Mon, 17 Nov 2014 05:32:10 -0500 Received: from mail-qc0-f174.google.com ([209.85.216.174]:49605 "EHLO mail-qc0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751213AbaKQKcI convert rfc822-to-8bit (ORCPT ); Mon, 17 Nov 2014 05:32:08 -0500 MIME-Version: 1.0 X-Originating-IP: [46.139.80.5] In-Reply-To: <20141114095511.789a76ac@gmail.com> References: <20141107170242.GA333@tucsk> <20141108192723.444cecd2@gmail.com> <20141110090954.GB333@tucsk> <20141114095511.789a76ac@gmail.com> Date: Mon, 17 Nov 2014 11:32:07 +0100 Message-ID: Subject: Re: [RFC PATCH] overlayfs: support more than one read-only layer From: Miklos Szeredi To: Jordi Pujol Palomer Cc: linux-unionfs@vger.kernel.org, Linux-Fsdevel , Kernel Mailing List , David Howells , Al Viro , "A. Wan" , Patrick Frisch , Aaron Campbell 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 On Fri, Nov 14, 2014 at 9:55 AM, Jordi Pujol Palomer wrote: > EL Mon, 10 Nov 2014 10:09:54 +0100 > Miklos Szeredi escrigué: > >> Maybe it wasn't clear, but the number of lower layers isn't limited by >> FILESYSTEM_MAX_STACK_DEPTH, > sorry, you have been clear, it's me that have not explained the purpose > of that patch. This idea is also valid for the main overlayfs > development. > Consider that we have an encrypted partition and a live OS that > uses overlayfs and works over it, when the OS is started already > reaches the maximum stacking depth (2). Also, hardcoding parameters > into the code may be annoying because a change implies creating and > mantaining patches, otherwise when the parameter is configurable we can > change it in a config value. Before allowing a change to FILESYSTEM_MAX_STACK_DEPTH we'd need to analyze the kernel stack usage of anything taking part in the filesystem stack. Not something that can be expected of users before they set a kernel config variable. 'Course we can change overlayfs and/or ecryptfs to use a new context for operations done on underlying layers. Not sure how much work that would be... > Also, I include a patch to explain better my first statement, > would say lowerdirs has extended the functionality of lowerdir, > therefore we can discard the lowerdir case that only works with one > lower layer and rename lowerdirs to lowerdir. It's more simple and all > the functionality is preserved. Yeah. But we also need some escaping in 'lowerdir=' argument to allow filenames with comma and colon. Current patch doesn't yet have that, but will work on it. Thanks, 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/