Re: [PATCH 1/2] Make page->private usable in compound pages V1

[Christoph Lameter]

On Fri, 6 Apr 2007, Andrew Morton wrote:

> > Both SLAB and SLUB use compound pages.
> 
> Not really.  slab sets the page->lru.prev of each constituent page to point
> at the controlling slab.

Uhh.. More slab inconsistencies. page[1]->lru is used for compound 
pages in the !MMU case.

>From page_alloc.c:

/*
 * Higher-order pages are called "compound pages".  They are structured 
thusly:
 *
 * The first tail page's ->lru.next holds the address of the compound 
page's
 * put_page() function.  Its ->lru.prev holds the order of allocation.
 * This usage means that zero-order pages may not be compound.
 */

> Will slub handle NOMMU anonymous pages appropriately?

I am not sure how anonymous pages relate to the slab allocators.

SLUB consistently uses compound pages for all higher order allocations.
And those are usually fine for mmu and no mmu even without this 
series of patches unless someone pokes around page->private.
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