Re: [RFC] sane access to per-fs metadata (was Re: [PATCH] Documentatio

[kaih@khms.westfalen.de (Kai Henningsen)]

chip@valinux.com (Chip Salzenberg)  wrote on 01.04.01 in <E14jdkF-0007Ps-00@tytlal>:

> Why not have a kernel thread and use standard RPC techniques like
> sockets?  Then you'd not have to invent anything unimportant like
> Yet Another IPC Technique.

You can, of course, transfer the exact same RPC messages over a file  
descriptor on your metadata fs. It doesn't *have* to be ASCII, especially  
not for purely internal-use interfaces.

And for ioctl() fans, you could transfer the exact same data via read()/ 
write() again. That's not significantly harder. Especially if you write a  
wrapper around the calls. If you want to be perverse, you can probably  
even transmit user space pointers.

But I suspect there are really only two generally useful interfaces:

1. A text based interface for generally-useful stuff you might want to  
manipulate from the shell, or random user programs. (From the shell _is_  
random user programs.)

2. A RPC based interface for tightly-coupled fs utilities. (I don't know  
off the top of my head what the kernel already has - ISTR networking has  
_something_.)

Don't forget a version marker of some kind. Sooner or later, you'll be  
glad you have it.

MfG Kai