tree b338a0c4e5673c4005898cf6f54270a6de9db399
parent 8cb0a5068f4108e8ca60d5e0bcfbe6901adcfaef
author Christoph Lameter <cl@linux.com> 1306949148 -0500
committer Pekka Enberg <penberg@kernel.org> 1309602413 +0300

mm: Rearrange struct page

We need to be able to use cmpxchg_double on the freelist and object count
field in struct page. Rearrange the fields in struct page according to
doubleword entities so that the freelist pointer comes before the counters.
Do the rearranging with a future in mind where we use more doubleword
atomics to avoid locking of updates to flags/mapping or lru pointers.

Create another union to allow access to counters in struct page as a
single unsigned long value.

The doublewords must be properly aligned for cmpxchg_double to work.
Sadly this increases the size of page struct by one word on some architectures.
But as a resultpage structs are now cacheline aligned on x86_64.

Signed-off-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>