Re: file as a directory

[David Masover <ninja@slaphack.com>]

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Peter Foldiak wrote:
| On Wed, 2004-12-15 at 04:47, David Masover wrote:
|
|>Peter Foldiak wrote:
|>| Also, a pseudofile (e.g. dirname/..../structure ?) could be used to
|>| specify how the files should be glued together. A simple question is,
|>| for instance, what separators to use between the components, and what
|>| ordering to use when putting the component objects together. (This
|>| pseudofile could also determine more complicated ways of composing
|>| objects.)
|>
|>If the filesystem does caching, I'd rather have a type of executable
|>which, read normally, appears as a stream of its own standard output.
|>You'd get the actual file as something like bar/.../source.
|
|
| This sounds better and more general than my proposed ..../structure
| file. So could you explain this in a bit more detail?
| Would for instance the simplest (and default?) glueing code in your
| bar/..../source file be
|
| cat *
|
| which just concatenates all the subcomponents in no particular order?

Sounds right.  Well, actually, you need a shebang, as this would be
called from kernel space.

Speaking of which, how much speed is lost by starting up a process?

The idea of caching is that running

cat *; cat *; cat *; cat *; cat *

is probably slower than

cat * > baz; cat baz; cat baz; cat baz; cat baz; cat baz

The kernel is the right place to do such caching.  It is not the right
place to implement almost any kind of "cool new kind of file" that Hans
wants us to develop.

|>This could be done with pipes and daemons, but it's not as easy to
|>manage and seems impossible to do as efficiently (with built-in caching,
|>etc.)
|
|
| How would you do it?

With two kernel reiser4 plugins -- one for files and one for
directories.  Others could come later, but I don't see this being so
important for things like symlinks.

Then, I'd let reiser4 cache things (in RAM and in free space on the
filesystem) which are generated through these plugins.

Directory plugins allow inheritence, too -- just have the plugin install
itself on all of its children.

Compression, encryption, etc. could all be done through the same mechanism.

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