Re: Merging relayfs?

[Greg KH <greg@kroah.com>]

On Mon, Jul 11, 2005 at 10:55:33PM -0500, Tom Zanussi wrote:
> Greg KH writes:
>  > On Mon, Jul 11, 2005 at 11:03:59PM -0400, Karim Yaghmour wrote:
>  > > 
>  > > Greg KH wrote:
>  > > > What ever happened to exporting the relayfs file ops, and just using
>  > > > debugfs as your controlling fs instead?  As all of the possible users
>  > > > fall under the "debug" type of kernel feature, it makes more sense to
>  > > > confine users to that fs, right?
>  > > 
>  > > Actually, like we discussed the last time this surfaced, there are far
>  > > more users for relayfs than just debugging.
>  > 
>  > Based on the proposed users of this fs, I don't see any.  What ones are
>  > you saying are not "debug" type operations?  And yes, I consider LTT a
>  > "debug" type operation :)
>  > 
>  > The best part of this, is it gives distros and users a consistant place
>  > to mount the fs, and to know where this kind of thing shows up in the fs
>  > namespace.
> 
> Makes sense, and I don't see a problem with getting rid of the fs part
> of relayfs and letting debugfs take over that role, if debugfs were
> there for all potential users.  It doesn't sound like it would satisfy
> users like LTT and systemtap though, who expect to be available at all
> times even on production systems, which wouldn't be the case unless
> the distros always shipped with debugfs enabled.

They will, the overhead of adding debugfs support is _very_ tiny, only:
 $ size fs/debugfs/built-in.o 
   text    data     bss     dec     hex filename
   2257     788       8    3053     bed fs/debugfs/built-in.o

So I do not see why you should not just drop your fs part.

>  > > What we settled on was having relayfs export its file ops so that
>  > > indeed debugfs users could use it to log things in conjunction with
>  > > debugfs.
>  > 
>  > Last I looked, this was not possible.  Has this changed in the latest
>  > version?
> 
> The file operations are all exported, but I haven't actually tried to
> use relayfs files in debugfs.  Is there something more needed?

Shouldn't be.  Try it to make sure though :)

thanks,

greg k-h