From owner-freebsd-hackers Thu May 20 15:26:26 1999 Delivered-To: freebsd-hackers@freebsd.org Received: from frmug.org (frmug-gw.frmug.org [193.56.58.252]) by hub.freebsd.org (Postfix) with ESMTP id BAC5F153AB for ; Thu, 20 May 1999 15:26:19 -0700 (PDT) (envelope-from roberto@keltia.freenix.fr) Received: (from uucp@localhost) by frmug.org (8.9.1/frmug-2.3/nospam) with UUCP id AAA26277 for freebsd-hackers@freebsd.org; Fri, 21 May 1999 00:26:18 +0200 (CEST) (envelope-from roberto@keltia.freenix.fr) Received: by keltia.freenix.fr (Postfix, from userid 101) id E37EE87AE; Thu, 20 May 1999 23:45:22 +0200 (CEST) (envelope-from roberto) Date: Thu, 20 May 1999 23:45:22 +0200 From: Ollivier Robert To: freebsd-hackers@freebsd.org Subject: Re: What does VOP_WHITEOUT() do? Message-ID: <19990520234522.A17041@keltia.freenix.fr> Mail-Followup-To: freebsd-hackers@freebsd.org References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii User-Agent: Mutt/0.95.5i In-Reply-To: ; from Zhihui Zhang on Thu, May 20, 1999 at 01:19:58PM -0400 X-Operating-System: FreeBSD 4.0-CURRENT/ELF ctm#5322 AMD-K6 MMX @ 200 MHz Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG According to Zhihui Zhang: > Can anyone tell me what does VOP_WHITEOUT() do? I can not find it in the > hypertext manual pages. You can find a small documentation in the 4.4BSD daemon book. It is used when stacking filesystems (especially unionfs). Imagine you have 2 FS mounted on above the other with unionfs. This gives you FS1. Note that when stacking FS, the underlying ones are R/O (FS2 in this case). FS "file A" it appears here. 1 --------------------- FS ---> file A the real file 2 File A is seen as part of the whole unified FS1. Now, imagine you "rm" file A from FS1. The file won't be actually removed from FS2 but a "whiteout" entry will appear inside FS1 to "mask" the file from it. More (and better) explanations on page 236 of the new daemon book. -- Ollivier ROBERT -=- FreeBSD: The Power to Serve! -=- roberto@keltia.freenix.fr FreeBSD keltia.freenix.fr 4.0-CURRENT #71: Sun May 9 20:16:32 CEST 1999 To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message