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