From owner-freebsd-arch  Sat Jun  9 10:39:24 2001
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Date: Sat, 09 Jun 2001 10:39:24 -0700
From: Terry Lambert <tlambert2@mindspring.com>
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To: Boris Popov <bp@butya.kz>
Cc: Alfred Perlstein <bright@rush.net>, Peter Wemm <peter@wemm.org>,
	"Patrick W. Penzias Dirks" <pwd@apple.com>, FreeBSD-FS@FreeBSD.ORG,
	FreeBSD-Arch@FreeBSD.ORG
Subject: Re: Support for pivot_root-like system call?
References: <Pine.BSF.4.21.0106090922230.72173-100000@lion.butya.kz>
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Boris Popov wrote:
> 
> On Fri, 8 Jun 2001, Alfred Perlstein wrote:
> 
> > The cache coherency bugs are not fixed for all cases, being able to
> > ask the underlying filesystem for the vm_object does not solve the
> > problem.
> >
> > What if i have a stacking layer where each page alternates
> > between two files that i'm stacked on top of?
> 
>         This is a case of "fan-out" stacking and such filesystems are much
> more complex than fan-in ones. VOP_*VOBJECT() were specifically designed
> for fan-in type of stacking.

Wrong.  Read the FICUS papers.  Support for a "translucent"
FS was one of the intial goals, as was HSM.

-- Terry

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