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authorWill Deacon <will.deacon@arm.com>2012-08-10 17:51:19 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2012-09-14 10:00:36 -0700
commitcb8a66cbdd326f905b95c9af77cb2f32b26dbd27 (patch)
tree3bec27352cf4d83fde952758ee63093539c3126d /arch/arm
parent9a0417a2d4b082bede8c0495d14d8bb20afaa700 (diff)
downloadlwn-cb8a66cbdd326f905b95c9af77cb2f32b26dbd27.tar.gz
lwn-cb8a66cbdd326f905b95c9af77cb2f32b26dbd27.zip
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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch/arm')
-rw-r--r--arch/arm/include/asm/pgtable.h6
1 files changed, 3 insertions, 3 deletions
diff --git a/arch/arm/include/asm/pgtable.h b/arch/arm/include/asm/pgtable.h
index 4c477044c47a..6afd081be23f 100644
--- a/arch/arm/include/asm/pgtable.h
+++ b/arch/arm/include/asm/pgtable.h
@@ -418,13 +418,13 @@ static inline pte_t pte_modify(pte_t pte, pgprot_t newprot)
*
* 3 3 2 2 2 2 2 2 2 2 2 2 1 1 1 1 1 1 1 1 1 1
* 1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0
- * <--------------- offset --------------------> <- type --> 0 0 0
+ * <--------------- offset ----------------------> < type -> 0 0 0
*
- * This gives us up to 63 swap files and 32GB per swap file. Note that
+ * This gives us up to 31 swap files and 64GB per swap file. Note that
* the offset field is always non-zero.
*/
#define __SWP_TYPE_SHIFT 3
-#define __SWP_TYPE_BITS 6
+#define __SWP_TYPE_BITS 5
#define __SWP_TYPE_MASK ((1 << __SWP_TYPE_BITS) - 1)
#define __SWP_OFFSET_SHIFT (__SWP_TYPE_BITS + __SWP_TYPE_SHIFT)