The quilt patch titled
Subject: nios2/mm: refactor swap PTE layout
has been removed from the -mm tree. Its filename was
nios2-mm-refactor-swap-pte-layout.patch
This patch was dropped because it was merged into the mm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
------------------------------------------------------
From: David Hildenbrand <david@xxxxxxxxxx>
Subject: nios2/mm: refactor swap PTE layout
Date: Fri, 13 Jan 2023 18:10:13 +0100
nios2 disables swap for a good reason: it doesn't even provide sufficient
type bits as required by core MM. However, swap entries are nowadays also
used for other purposes (migration entries, PTE markers, HWPoison, ...),
and accidential use could be problematic.
Let's properly use 5 bits for the swap type and document the layout. Bits
26--31 should get ignored by hardware completely, so they can be used.
Link: https://lkml.kernel.org/r/20230113171026.582290-14-david@xxxxxxxxxx
Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
Cc: Dinh Nguyen <dinguyen@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
--- a/arch/nios2/include/asm/pgtable.h~nios2-mm-refactor-swap-pte-layout
+++ a/arch/nios2/include/asm/pgtable.h
@@ -232,19 +232,21 @@ static inline unsigned long pmd_page_vad
__FILE__, __LINE__, pgd_val(e))
/*
- * Encode and decode a swap entry (must be !pte_none(pte) && !pte_present(pte):
+ * Encode/decode swap entries and swap PTEs. Swap PTEs are all PTEs that
+ * are !pte_none() && !pte_present().
*
- * 31 30 29 28 27 26 25 24 23 22 21 20 19 18 ... 1 0
- * 0 0 0 0 type. 0 0 0 0 0 0 offset.........
+ * Format of swap PTEs:
*
- * This gives us up to 2**2 = 4 swap files and 2**20 * 4K = 4G per swap file.
+ * 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
+ * 0 < type -> 0 0 0 0 0 0 <-------------- offset --------------->
*
- * Note that the offset field is always non-zero, thus !pte_none(pte) is always
- * true.
+ * Note that the offset field is always non-zero if the swap type is 0, thus
+ * !pte_none() is always true.
*/
-#define __swp_type(swp) (((swp).val >> 26) & 0x3)
+#define __swp_type(swp) (((swp).val >> 26) & 0x1f)
#define __swp_offset(swp) ((swp).val & 0xfffff)
-#define __swp_entry(type, off) ((swp_entry_t) { (((type) & 0x3) << 26) \
+#define __swp_entry(type, off) ((swp_entry_t) { (((type) & 0x1f) << 26) \
| ((off) & 0xfffff) })
#define __swp_entry_to_pte(swp) ((pte_t) { (swp).val })
#define __pte_to_swp_entry(pte) ((swp_entry_t) { pte_val(pte) })
_
Patches currently in -mm which might be from david@xxxxxxxxxx are
