[Info-vax] MOUNT and filesystems, was: Re: RMS record metadata, was: Re: Re; Spiralog, RMS Journaling (was

[Simon Clubley]

On 2016-06-26, David Froble <davef at tsoft-inc.com> wrote:
> Simon Clubley wrote:
>> 
>> IMHO, I agree with you on this one. Based on what general knowledge
>> I know of how it's implemented internally (I've never seen the VMS
>> source code), MOUNT internals are a disaster area if you ever wanted
>> to implement general mount support in VMS for a variety of filesystems
>> in the way that it's possible in Linux (for example).
>> 
>> You should be able to write (for example) a FAT32 filesystem driver
>> from public documentation and use a MOUNT command to mount it in the
>> same way as you can with an ODS-2 volume.
>
> Why do you think that MOUNT should be able to handle some format that it doesn't 
> know about?
>

The MOUNT command should know exactly nothing about the internals of
the filesystem on _any_ volume it is being asked to mount; it should
restrict itself to providing the general mount infrastructue.

In a modular system, filesystem specific knowledge should be held
within the filesystem driver only and MOUNT should restrict itself
to asking the driver for {X} filesystem (via a standard interface)
if the driver recognises the filesystem on volume {Y}.

{Y} does not have to be a physical disk/tape/whatever BTW; it could
be a purely software/virtual construct in a modular system.

> Perhaps if you wish to implement a FAT32 filesystem driver, then you should also 
> implement the method(s) for mounting the filesystem.

And that's exactly what happens in a modular system; MOUNT would
provide general mounting services only. If you didn't want MOUNT
to ask each registered filesystem in turn about the volume MOUNT
was being asked to mount, then the only additional MOUNT qualifier
you would need would be /FILESYSTEM={whatever} where {whatever}
would be the registered name of the filesystem driver.

Simon.

-- 
Simon Clubley, clubley at remove_me.eisner.decus.org-Earth.UFP
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