Subject: Re: Improving the Unix API
To: Francois-Rene Rideau <>
From: der Mouse <mouse@Rodents.Montreal.QC.CA>
List: tech-kern
Date: 06/27/1999 19:33:32
>> (clri didn't work?)
> Never heard about clri (was under Linux).

May not have existed, then, which *would* explain it. :-)

>>> Another problem was the ability to change the mount status of a
>>> partition from read-write to read-only or to unmounted,
>> See NetBSD (and presumably other BSD) "mount -o update,rdonly"
>> and/or "umount -f".
> If you re-read the original message, the problem is what to do about
> processes with open file descriptors on the partition: stop them at
> once? stop them at first file access? block them instead? kill them?

Yes, that's the most difficult part.

The NetBSD manpage doesn't say what happens if you "mount -o
update,force,rdonly" when there are writeable descriptors open onto the
filesystem, and then try to use those fds.  I would assume further
attempts to write would produce errors (EROFS?), unless of course the
filesystem has been re-remounted read/write.

The manpage for umount says

     -f      The filesystem is forcibly unmounted.  Active special devices
             continue to work, but all other files return errors if further
             accesses are attempted.

I haven't looked at the relevant kernel code to see what *really*

> How will you allow for such large table-walking to be compatible with
> real-time kernel response?

*What* large table-walking?  All this means you have to do is have
every write check the relevant mount point to see if it's mounted
read-only, for downgrading remounts, and mark the filesystem as gone,
for forced unmounts.  (I suspect this is what deadfs is for.)

>>> I intend to put free unices in competition [...]
>> Reasonable as this sounds, I think the last thing we need is yet
>> another ground on which one free-unix can be doing the "nana nana
>> boo boo" taunt at another.
> Competition is _not_ about taunting each other for pride;

I know this.  I even think most of the people involved know it.

But there seem to be a few - not many, but very poisonous - who seem to
take any competition - indeed, almost any *difference* - as an
opportunity for "we're better than you" egoboo.

					der Mouse

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