Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752531AbaBMR2l (ORCPT ); Thu, 13 Feb 2014 12:28:41 -0500 Received: from mail-qc0-f181.google.com ([209.85.216.181]:40249 "EHLO mail-qc0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752482AbaBMR2h (ORCPT ); Thu, 13 Feb 2014 12:28:37 -0500 MIME-Version: 1.0 X-Originating-IP: [86.59.245.170] In-Reply-To: <20106.1392309770@warthog.procyon.org.uk> References: <1391791751-2533-1-git-send-email-miklos@szeredi.hu> <19258.1392306854@warthog.procyon.org.uk> <20140213162534.GB4026@tucsk.piliscsaba.szeredi.hu> <20106.1392309770@warthog.procyon.org.uk> Date: Thu, 13 Feb 2014 18:28:35 +0100 Message-ID: Subject: Re: [PATCH 00/13] cross rename v4 From: Miklos Szeredi To: David Howells Cc: Al Viro , Linus Torvalds , Linux-Fsdevel , Kernel Mailing List , Bruce Fields , Christoph Hellwig , Andrew Morton , Zach Brown , Jan Kara , Andy Lutomirski , "mszeredi@suse.cz" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Feb 13, 2014 at 5:42 PM, David Howells wrote: > Miklos Szeredi wrote: > >> Regarding whiteouts, I raised a couple of questions that nobody answered >> yet, so let me ask again. >> >> - If a filesystem containing whiteouts (fallthroughs, etc...) is mounted as >> not part of a union, how are these special entities represented to >> userspace? > > I would suggest that whiteouts appear as otherwise negative dentries and that > they don't appear in getdents(). I'd argue that this is an administration nightmare. E.g. what if the a backup needs to be made of the rw layer? Will rmdir work normally in a directory containing whiteouts? Will the VFS take care of that, just like if it was part of a union? Or will it fail with ENOTEMPTY despite *appearing* empty? And zillion other problems related to the fact that things happen to a filesystem even when they do not appear to happen ("mv foo bar; mv bar foo" has side effects). 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/