Re: Getting IOCTL's into VFS File System Drivers

Alexander Viro (viro@math.psu.edu)
Sat, 13 Nov 1999 23:37:17 -0500 (EST)


On 13 Nov 1999, david parsons wrote:

> In article <linux.kernel.Pine.LNX.4.10.9911111758560.2217-100000@asdf.capslock.lan>,
> Mike A. Harris <mharris@meteng.on.ca> wrote:
>
> >Actually, from what I was just reading about Windows 2000,
> >Microsoft is adding a new innovative feature that they single
> >handedly came up with that allows you to "splice" a filesystem
> >onto a directory point.
>
> JOIN. It's at least 11 years old, and it's existed since MS-DOS
> 4.something.
3.something. And it required the mounpoint to be immediate
subdirectory of root. Due to the way they've stored the namespace state
the whole thing fscked up magnificiently if you tried to work with the
root of mounted fs via the old drive name. SUBST was less b0rken, though.
And more useful, BTW - it gave weak equivalent of tilde-expansion. Mixing
them was Bad Idea(tm). I've looked at 3.30 kernel - scary and fascinating.
Obviously modeled after v7, but _what_ a mess had they slapped onto
the upper half for CP/M emulation... Scary. It almost looked like a small
subset of UNIX placed on a box with rather shitty IO and buried under the
heaploads of CP/M compatibility crap. They might start with CP/M clone,
but 3.x internals looked rather like a castrated and mutilated Xenix.

> It's almost exactly mount, though MS-DOS didn't have
> a procfs to nicely export the mount table.

/me notices the provocation.
/me recalls the US laws regarding the death threats.
/me says nothing and walks away.

> david parsons \bi/ Of course MS could have dropped it, then re-added it
> \/ recently as a New! Thing!

ISTR some claims that NT 3.5 had unified tree and foo:bar names didn't
even reach the kernel - translation happened in one of the shared libs.
If it's really so their stuff should actually remount filesystems.

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