From owner-freebsd-fs  Thu May 25 23:50:52 2000
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Date: Fri, 26 May 2000 02:58:30 -0400
From: Chuck McCrobie <mccrobi@aplcenMP.apl.jhu.edu>
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To: freebsd-fs@FreeBSD.ORG
Subject: Opinion on File System Implementation
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I am working on readability of the OpenVMS Files-11 On-Disk Structure 2
file
system under FreeBSD.  As many of you may know, Files-11 ODS-2 has a
"wealth"
of record attributes and file organizations to choose from.  The actual
file
data for some of these record types contains record level meta-data. 
Simply
reading the file "blindly" will result in both the "intended" data and
the
meta-data being returned.

I'm wondering if I should just return the "raw" data, including embedded
record
attributes back during the "read" routine.  If so, I would like to
provide some
mechanism so that user mode programs can get the record attributes and
"do the
right thing".  Is there such a thing as an "ioctl" interface to a file
system?
If I approach the embedded meta-data in this manner, what would be the
best
mechanism for returning the record attributes?  Perhaps a special file,
which
when opened and read, will return a fixed structure describing the
file/record
attributes?  It doesn't seem too hard to handle special files inside the
operating system.

I suspect that the majority of customers (I plan on commericalizing my
work)
would like to have the file system interpret the record attributes and
file
organizations.  Thus, the user mode programs would see the "intended"
data, not
the embedded meta-data.

Thanks for your time,

Chuck McCrobie (** MAD VAX **)
mccrobi@apl.jhu.edu


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