Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757686Ab3CNM6D (ORCPT ); Thu, 14 Mar 2013 08:58:03 -0400 Received: from mail01-md.ns.itscom.net ([175.177.155.111]:44126 "EHLO mail01-md.ns.itscom.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755776Ab3CNM6C (ORCPT ); Thu, 14 Mar 2013 08:58:02 -0400 From: "J. R. Okajima" Subject: DT_WHT (Re: [PATCH 00/13] overlay filesystem: request for inclusion (v16)) To: Miklos Szeredi Cc: Al Viro , Linus Torvalds , linux-fsdevel , Linux Kernel Mailing List , Christoph Hellwig , Andrew Morton , Robo Bot , Felix Fietkau , Neil Brown , Jordi Pujol , ezk@fsl.cs.sunysb.edu, David Howells , Sedat Dilek In-Reply-To: References: <1363102908-28956-1-git-send-email-miklos@szeredi.hu> <20130312222350.GK21522@ZenIV.linux.org.uk> <20130313185249.GL21522@ZenIV.linux.org.uk> <20130313231918.GP21522@ZenIV.linux.org.uk> Date: Thu, 14 Mar 2013 21:57:46 +0900 Message-ID: <1402.1363265866@jrobl> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1269 Lines: 28 Miklos Szeredi: > On Thu, Mar 14, 2013 at 12:19 AM, Al Viro wrote: ::: > > As for whiteouts... I think we ought to pull these bits of unionmoun > > queue into the common stem and add the missing filesystems to them; > > ext* and ufs are trivial (keep in mind that FFS derivatives, including > > ext*, have d_type in directory entry and type 14 (DT_WHT) is there > > precisely for that purpose). btrfs also has "dir_type" thing - 8bit > > field... > > What about userspace interfaces? Are we allowed to extend d_type and > st_mode without breaking things? Introducing a new d_type value can be a headache for other filesystems or other OSs. Whiteout and opaque by xattr is an idea, but I prefer more primitive way (special hidden filename) since xattr may force users to change their configuration and it consumes disk space a little. Filesystems may have a limit for the consumed size by xattr. If xattr reaches the limit, then several operation in overlayfs will be unusable. J. R. Okajima -- 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/