Re: [RFC][PATCH] nbd driver for 2.5+: fix locking issues with ioctl UI

[Christoph Hellwig]

On Wed, Jun 25, 2003 at 11:38:43AM -0600, Lou Langholtz wrote:
> Yes. To be fair though, the binary (and the driver too) was broken on 
> linux 2.5 kernels long before I even proposed any changes to the nbd 
> driver. I'm trying to fix that.

Hey, I didn't say changing the interface is wrong.  But if possible
do it in a way that the new userspace can still support the old kernel
driver.

> NBD_SET_SOCK. That'd tell nbd-tool that the nbd driver thinks something 
> about the ioctl was invalid but not what. I wanted to return EDEPRECATED 
> instead but I haven't found that errno yet. I could overload an errno 
> but that seems ugly too. Or the driver could have a NBD_GET_VERSION 
> ioctl. Is there precedence for that? I haven't come accross it yet.

That's one choice.  At least md and device mapper do that.