Re: [patch] [RFC] make WANT_PAGE_VIRTUAL a config option

[Roman Zippel <zippel@linux-m68k.org>]

Hi,

On Fri, 17 Dec 2004, Dave Hansen wrote:

> > > No.  But, I do think that most of the very basic VM structures do, as it
> > > stands.  That's limited to struct page, zone, and pgdat as I see it
> > > now.  
> > 
> > Why do you want to put these into separate headers?
> 
> It enables you do do static inlines accessing struct page members
> anywhere you want, such as in asm/mmzone.h, like in my example. 

And by that you add more header dependencies.
We have basically this situation:

	foo.h (struct foo; inline foo();) <-> bar.h (struct bar; inline bar();)

Almost every time we had such recursive dependencies, we simply rip one 
element out and put it into a separate header:

	foo.h (inline foo();)
		-> bar.h (struct bar; inline bar();)
			-> foo_struct.h (struct foo;)

Repeat this often enough and we end up with millions of small header 
files. Instead we can reorder everything a little and can do this:

	foo.h (inline foo(); inline bar();)
		-> foo_types.h (struct foo; struct bar;)

In your case don't put the inline functions into asm/mmzone.h and we 
should merge the various definition into fewer header files.

> > > The dependencies aren't very twisted at all.  In fact, I don't think any
> > > of those are deeper than two.  More importantly, I never have to cope
> > > with 'struct page;' keeping me from doing arithmetic. 
> > 
> > You may be surprised. :)
> > Play around with "mkdir test; echo 'obj-y = test.o' > test/Makefile; echo 
> > '#include <linux/foo.h>' > test/test.c; make test/test.i 
> > CFLAGS_test.o=--trace-includes".
> 
> I'm not sure what you're getting at.
> 
> 	make: *** No rule to make target `test/test.i'.  Stop.

Sorry, I forgot to mention that you have to do this inside a kernel tree.

bye, Roman