From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alex Riesen Subject: Re: [PATCH 17/38] union-mount: Union mounts documentation Date: Wed, 23 Jun 2010 10:43:10 +0200 Message-ID: References: <1276627208-17242-1-git-send-email-vaurora@redhat.com> <1276627208-17242-18-git-send-email-vaurora@redhat.com> <20100617183912.GA14389@shell> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Valerie Aurora , viro@zeniv.linux.org.uk, jblunck@suse.de, hch@infradead.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org To: Miklos Szeredi Return-path: Received: from mail-yw0-f198.google.com ([209.85.211.198]:40340 "EHLO mail-yw0-f198.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751766Ab0FWInL convert rfc822-to-8bit (ORCPT ); Wed, 23 Jun 2010 04:43:11 -0400 In-Reply-To: Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Mon, Jun 21, 2010 at 15:14, Miklos Szeredi wrote= : > On Thu, 17 Jun 2010, Valerie Aurora wrote: >> On Thu, Jun 17, 2010 at 10:01:30AM +0200, Alex Riesen wrote: >> > On Tue, Jun 15, 2010 at 20:39, Valerie Aurora = wrote: >> > > +git://git.kernel.org/pub/scm/fs/ext2/val/e2fsprogs.git >> > > + >> > > +Currently, whiteout directory entries are not returned to userl= and. >> > > +While the directory type for whiteouts, DT_WHT, has been define= d for >> > > +many years, very little userland code handles them. ??Userland = will >> > > +never see fallthru directory entries. >> > >> > This may be a dumb question (I must admit I did only very little r= esearch), >> > but how does one cleanup the topmost layer of whiteouts and fallth= roughs, >> > so that the entries of lower layer(s) can be made visible again? >> >> I'm not sure how best to do this. =C2=A0We don't want to add more sy= stem >> calls. =C2=A0One thought of mine has been to do this offline, when t= he file >> system is unmounted. =C2=A0For example, e2fsck could add a feature t= o >> delete whiteouts and fallthrus. =C2=A0Another option is to add a fla= g to an >> existing system call. > > One more advantage of doing whiteouts, etc. with hard links and > extended attributes instead of as special filesystem objects. =C2=A0T= hat > way they are visible (unless part of a union) and can be treated as > normal filesystem objects. But then you have to break union to cleanup the topmost filesystem. That'll surely take the mount filesystem (in its working configuration,= at least) offline. Not much better than using fsck. -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel= " in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html