From: Will Deacon 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: v3.5.4~103 X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=0b80803ce3abad2533fc03133d1ca1759c8335fd;p=karo-tx-linux.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 Signed-off-by: Will Deacon Signed-off-by: Russell King Signed-off-by: Greg Kroah-Hartman --- diff --git a/arch/arm/include/asm/pgtable.h b/arch/arm/include/asm/pgtable.h index d88f9f049e95..41dc31f834c3 100644 --- a/arch/arm/include/asm/pgtable.h +++ b/arch/arm/include/asm/pgtable.h @@ -253,13 +253,13 @@ 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)