[PATCH 2/2] ARM: mm: use 5 bits for swapfile type encoding

On Thu, Jul 26, 2012 at 05:01:08PM +0100, Will Deacon wrote:

Page migration encodes the pfn in the offset field of a swp_entry_t.
For LPAE, we support physical addresses of up to 36 bits (due to
sparsemem limitations with the size of page flags), requiring 24 bits
to represent a pfn. A further 3 bits are used to encode a swp_entry into
a pte, leaving 5 bits for the type field. Furthermore, the core code
defines MAX_SWAPFILES_SHIFT as 5, so the additional type bit does not
get used.

This patch reduces the width of the type field to 5 bits, allowing us
to create up to 31 swapfiles of 64GB each.

Signed-off-by: Will Deacon <redacted>

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>