Re: Prezeroing V3 [1/4]: Allow request for zeroed memory

[Linus Torvalds]

On Mon, 10 Jan 2005, Christoph Lameter wrote:
>
> Yes. Right my ia64 centric vision got me again. Thanks for all the other
> patches that were posted. I hope this is now all cleared up?

Hmm.. I fixed things up, but I didn't exactly do it like the posted 
patches. 

Currently the BK tree
 - doesn't use __GFP_ZERO with anonymous user-mapped pages (which is what 
   you wrote this whole thing for ;)

   Potential fix: declare a per-architecture "alloc_user_highpage(vaddr)"
   that does the proper magic on virtually indexed machines, and on others 
   it just does a "alloc_page(GFP_HIGHUSER | __GFP_ZERO)".

 - verifies that nobody ever asks for a HIGHMEM allocation together with 
   __GFP_ZERO (nobody does - a quick grep shows that 99% of all uses are
   statically clearly fine (there's a few HIGHMEM zero-page users, but 
   they are all GFP_KERNEL or similar), with just two special cases:

	- get_zeroed_page() - which can't use HIGHMEM anyway
	- shm.c does "mapping_gfp_mask(inode->i_mapping) | __GFP_ZERO"
	  and that's fine because while the mapping gfp masks may lack
	  GFP_FS and GFP_IO, they are always supposed to be ok with 
	  waiting.

 - moves "kernel_map_pages()" into "prep_new_page()" to fix the 
   DEBUG_PAGEALLOC issue (Chris Wright).

So that should take care of the known problems.

		Linus
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