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authorWill Deacon <will.deacon@arm.com>2012-08-10 17:51:19 +0100
committerRussell King <rmk+kernel@arm.linux.org.uk>2012-08-11 09:15:59 +0100
commitf5f2025ef3e2cdb593707cbf87378761f17befbe (patch)
tree92e3e13ae25f950781294c112a4a03176e39fd10
parent47f1204329237a0f8655f5a9f14a38ac81946ca1 (diff)
ARM: 7488/1: mm: use 5 bits for swapfile type encoding
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. Cc: <stable@vger.kernel.org> 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>
-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 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)