Re: [PATCH 2/25] NTFS: Allow highmem kmalloc() in ntfs_malloc_nofs() and add _nofail() version.

[Horst von Brand <vonbrand@inf.utfsm.cl>]

Anton Altaparmakov <aia21@cam.ac.uk> wrote:
> On Fri, 2005-09-09 at 15:02 +0300, Pekka J Enberg wrote:
> > On Fri, 9 Sep 2005, Anton Altaparmakov wrote:

> > > > I completely disagree with you given that this is not "inventing
> > > > [...] own memory allocators", it is just a convenient short hand.
> > > > I am sure a lot of people would agree with you though.  It is just
> > > > a matter of personal preference.

> > > I should add that this is not ntfs only, the idea is from another file
> > > system which uses it, too.  Can't remember which one it was, though (xfs
> > > maybe?).

> > Indeed. It is not just a matter of personal preference but also a matter 
> > of subsystems introducing duplicate code like this. Quick grepping shows 
> > UDF doing same thing  and XFS doing slightly differently but I am pretty 
> > sure I've seen it elsewhere too.

> Yes, that is usually a good indication that a generic function should be
> provided.  However having a generic function with complicated and long
> arguments is no use as everyone will want their own shorter one anyway.
> And given the function is static inline it actually makes no difference
> to the generated code size.  Also calling it __vmalloc_fast makes no
> sense as it doesn't always use vmalloc...  Given we have kmalloc and
> vmalloc maybe it should be just malloc?

That it makes no difference to the generated code isn't enough. If somebody
if going over the kernel with a fine comb trying to fix memory allocations
(example as here), she will have to remember half a dozen slightly
different ways of doing the same thing, for no good reason. And probably
miss a bundle in the process. This is bad in itself.

> Obviously if there were a suitable generic function I would use it but I
> and I imagine all the other users would still wrap it with the old name.

I'd hope not.

[Yes, I can understand that each subsystem has its own "culture", and
 trying to force them all into the same mold is friction too.]
-- 
Dr. Horst H. von Brand                   User #22616 counter.li.org
Departamento de Informatica                     Fono: +56 32 654431
Universidad Tecnica Federico Santa Maria              +56 32 654239
Casilla 110-V, Valparaiso, Chile                Fax:  +56 32 797513