From: Will Deacon <will.deacon@arm.com>
Date: Fri, 10 Aug 2012 16:51:19 +0000 (+0100)
Subject: ARM: 7488/1: mm: use 5 bits for swapfile type encoding
X-Git-Tag: v3.2.29~75
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=775152296f2a750ebefc58d35fe0479a679f6797;p=pandora-kernel.git

ARM: 7488/1: mm: use 5 bits for swapfile type encoding

commit f5f2025ef3e2cdb593707cbf87378761f17befbe upstream.

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.

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---

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