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Date:      Wed, 6 Jan 1999 14:44:47 -0800
From:      Don Lewis <Don.Lewis@tsc.tdk.com>
To:        dyson@iquest.net, tlambert@primenet.com (Terry Lambert)
Cc:        dillon@apollo.backplane.com, pfgiffun@bachue.usc.unal.edu.co, freebsd-hackers@FreeBSD.ORG
Subject:   Re: questions/problems with vm_fault() in Stable
Message-ID:  <199901062244.OAA01922@salsa.gv.tsc.tdk.com>
In-Reply-To: "John S. Dyson" <dyson@iquest.net> "Re: questions/problems with vm_fault() in Stable" (Jan  5,  9:55pm)

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On Jan 5,  9:55pm, "John S. Dyson" wrote:
} Subject: Re: questions/problems with vm_fault() in Stable

} Any of the problems with the existing VFS/VM scheme have been with the
} intricacies of dealing with VFS special cases, and dealing with the
} I/O abstraction of buffers as a cache.  Forget "files" and think
} "blobs of memory."  Once the notion of file is forgotten, then shadowing,
} invalidation and aliasing of memory become very obvious...

One complication that comes to mind is /dev/vn*.  There's a blob of
memory associated with the file that's attached to this device.  If
you create a filesystem on this device and mount it, then each of
the files in that filesystem will also have an associated blob of
memory and these memory blobs are subsets of the big blob.  Of course
you could do something really crazy and use something like ccd to
stripe a couple of /dev/vn* devices together and use the result as
a filesystem ...

Maybe the thing to do is to turn all the filesystems into stacking
layers, including ffs.

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