Date: Thu, 20 May 1999 23:45:22 +0200 From: Ollivier Robert <roberto@keltia.freenix.fr> To: freebsd-hackers@freebsd.org Subject: Re: What does VOP_WHITEOUT() do? Message-ID: <19990520234522.A17041@keltia.freenix.fr> In-Reply-To: <Pine.GSO.3.96.990520131748.8958B-100000@sol.cs.binghamton.edu>; from Zhihui Zhang on Thu, May 20, 1999 at 01:19:58PM -0400 References: <Pine.GSO.3.96.990520131748.8958B-100000@sol.cs.binghamton.edu>
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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
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