On Wed, 19 Sep 2012, Glauber Costa wrote:

On 09/18/2012 07:06 PM, Christoph Lameter wrote:

quoted

On Tue, 18 Sep 2012, Glauber Costa wrote:

quoted

+++ b/include/linux/gfp.h

@@ -35,6 +35,11 @@ struct vm_area_struct;
 #else
 #define ___GFP_NOTRACK		0
 #endif
+#ifdef CONFIG_MEMCG_KMEM
+#define ___GFP_KMEMCG		0x400000u
+#else
+#define ___GFP_KMEMCG		0
+#endif

Could you leave __GFP_MEMCG a simple definition and then define GFP_MEMCG
to be zer0 if !MEMCG_KMEM? I think that would be cleaner and the
__GFP_KMEMCHECK another case that would be good to fix up.

I can, but what does this buy us?

All the numeric values should be defined with __ unconditionally so that
they can be used in future context. Note the comment above the __GFP_XX
which says "Do not use this directly".

Also, in any case, this can be done incrementally, and for the other
flag as well, as you describe.

There is only one other flag that does not follow the scheme. I'd
appreciate it if you could submit a patch to fix up the __GFP_NOTRACK
conditional there.

There is no need to do this incrementally. Do it the right way
immediately.