Re: [9fans] Df command in Plan9?

[Alexander Viro <viro@math.psu.edu>]

On Fri, 20 Oct 100, Rick Hohensee wrote:

> >
> >
> >
> > On Fri, 20 Oct 2000, Russ Cox wrote:
> >
> > > Please don't tell me that du /dev/sda1 would
> > > do something other than report the disk size
> > > under Linux.
> >
>
> df, BTW, is one of those design flaws of unix that is so
> obvious nobody sees it. A directory has a size. It is the
> size of it's contents, not the size of the "file" containing
> the dirnames and so on. The size of a directory, it's "du-size",
> is something the filesystem should keep track of.

Sigh... Rick, we've been through that how many times?
	* Unices have link(2) and/or bind(2) (I mean Plan 9, not BSD
one). Deal. No, dropping both is not an option.
	* you are creating a major contention point, since effects of
_any_ block allocation have to propagate all way down through the
directory tree.
	* Forget about the metadata consistency - with your scheme damn
next to every operation requires multiple on-disk changes, and that's
putting it quite mildly.
	* Non-local operations are prone to races. Even cross-directory
rename(2) is a major PITA. The thing you are proposing is going to be
much worse.
	* Programs that might benefit from that "du-size" are either
going to scan the tree anyway or belong to very small class -
filemanagers. Punishing all normal processes for the feature they don't
need is Wrong. Moreover, programs that might benefit from that change are
notoriously badly written. I'm yet to see a filemanager that would not be
a bloated pile of crap. If you want to accelerate them - start with
removing the obvious junk, then you might expect at least some sympathy.

> I had a bag of code hung off the side of Linux for "Dyndufs",
> but then there was a severe ripple in the chrono-synclastic
> infindibulum, and I got a job.

You've also been told that these changes are _not_ going into the tree,
*period*. Quite a few times. Due to the reasons above and then some
(semantics on the mountpoints, etc.). IIRC, you just kept repeating that
filemanagers were the only programs that mattered anyway since they are
all that "normal users" (whatever it means) see. Sorry, not impressed.