Re: [PATCH v2 5/5] staging: lustre: headers: use proper byteorder functions in lustre_idl.h

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Tue, Dec 13, 2016 at 12:55:01AM +0000, Dilger, Andreas wrote:
> On Dec 12, 2016, at 13:00, James Simmons <jsimmons@infradead.org> wrote:
> > 
> > 
> >> On Sat, Dec 10, 2016 at 01:06:01PM -0500, James Simmons wrote:
> >>> In order for lustre_idl.h to be usable for both user
> >>> land and kernel space it has to use the proper
> >>> byteorder functions.
> >> 
> >> Why would userspace need/want all of these inline functions?  A uapi
> >> header file should just have a the structures that are passed
> >> user/kernel and any needed ioctls.  Why would they ever care about
> >> strange byte flip functions and a ton of inline functions?
> >> 
> >> I don't think this is needed, of if it is, I really don't want to see
> >> your crazy userspace code...
> > 
> > Sigh. More cleanups were done based on the idea this was okay. The
> > reason this was does was when you look at the headers in
> > include/uapi/linux you see a huge number of headers containing a bunch
> > of inline function. To an outside project looking to merge their work
> > into the kernel they would think this is okay. Hopefully all those
> > broken headers will be cleaned up in the near future.
> > Alright I will look to fixing up our tools to handle this requirement. 
> 
> These accessor functions are used by both the kernel and userspace
> tools, and keeping them in the lustre_idl.h header avoids duplication
> of code.  Similar usage exists in other filesystem related uapi headers
> (e.g. auto_fs4.h, bcache.h, btrfs_tree.h, nilfs2_ondisk.h, swab.h, etc.).
> 
> That said, if there is an objection to keeping these macros/inline funcs
> in the uapi headers, they still need to exist in the kernel and should
> be kept in the lustre/include/lustre directory and we'll keep a separate
> copy of the macros for userspace.

"simple" accessors/setters are fine, but these start to get complex, you
are using unlikely, and debug macros and lots of other fun stuff.  Do
all other filesystems also do complex stuff like ostid_to_fid()?

thanks,

greg k-h