Re: [RFC] sane access to per-fs metadata (was Re: [PATCH] Documentation/ioctl-number.txt)

Alexander Viro
2001-03-23T18:30:00Z

On Fri, 23 Mar 2001, Matthew Wilcox wrote:

> On Fri, Mar 23, 2001 at 09:56:47AM -0700, Bryan Henderson wrote:
> > There's a lot of cool simplicity in this, both in implementation and
> > application, but it leaves something to be desired in functionality. This
> > is partly because the price you pay for being able to use existing,
> > well-worn Unix interfaces is the ancient limitations of those interfaces
> > -- like the inability to return adequate error information.
>
> hmm... open("defrag-error") first, then read from it if it fails?

Or just do
(echo $cmd; read reply) <file >&0
and make write() queue a reply. Yup, on the struct file used for write().

You _will_ need serialization for operations themselves, but for getting
replies... Not really.

> > With ioctl, I can easily match a response of any kind to a request. I can
> > even return an English text message if I want to be friendly.

So you can with read(). You know, the function that is intended to be used for
reading stuff into user-supplied buffer...