The patch titled
Subject: arm/mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE
has been added to the -mm mm-unstable branch. Its filename is
arm-mm-support-__have_arch_pte_swp_exclusive.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/arm-mm-support-__have_arch_pte_swp_exclusive.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: David Hildenbrand <david@xxxxxxxxxx>
Subject: arm/mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE
Date: Fri, 13 Jan 2023 18:10:04 +0100
Let's support __HAVE_ARCH_PTE_SWP_EXCLUSIVE by stealing one bit from the
offset. This reduces the maximum swap space per file to 64 GiB (was 128
GiB).
While at it drop the PTE_TYPE_FAULT from __swp_entry_to_pte() which is
defined to be 0 and is rather confusing because we should be dealing with
"Linux PTEs" not "hardware PTEs". Also, properly mask the type in
__swp_entry().
Link: https://lkml.kernel.org/r/20230113171026.582290-5-david@xxxxxxxxxx
Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
Reviewed-by: Russell King (Oracle) <rmk+kernel@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
--- a/arch/arm/include/asm/pgtable-2level.h~arm-mm-support-__have_arch_pte_swp_exclusive
+++ a/arch/arm/include/asm/pgtable-2level.h
@@ -126,6 +126,9 @@
#define L_PTE_SHARED (_AT(pteval_t, 1) << 10) /* shared(v6), coherent(xsc3) */
#define L_PTE_NONE (_AT(pteval_t, 1) << 11)
+/* We borrow bit 7 to store the exclusive marker in swap PTEs. */
+#define L_PTE_SWP_EXCLUSIVE L_PTE_RDONLY
+
/*
* These are the memory types, defined to be compatible with
* pre-ARMv6 CPUs cacheable and bufferable bits: n/a,n/a,C,B
--- a/arch/arm/include/asm/pgtable-3level.h~arm-mm-support-__have_arch_pte_swp_exclusive
+++ a/arch/arm/include/asm/pgtable-3level.h
@@ -76,6 +76,9 @@
#define L_PTE_NONE (_AT(pteval_t, 1) << 57) /* PROT_NONE */
#define L_PTE_RDONLY (_AT(pteval_t, 1) << 58) /* READ ONLY */
+/* We borrow bit 7 to store the exclusive marker in swap PTEs. */
+#define L_PTE_SWP_EXCLUSIVE (_AT(pteval_t, 1) << 7)
+
#define L_PMD_SECT_VALID (_AT(pmdval_t, 1) << 0)
#define L_PMD_SECT_DIRTY (_AT(pmdval_t, 1) << 55)
#define L_PMD_SECT_NONE (_AT(pmdval_t, 1) << 57)
--- a/arch/arm/include/asm/pgtable.h~arm-mm-support-__have_arch_pte_swp_exclusive
+++ a/arch/arm/include/asm/pgtable.h
@@ -271,27 +271,48 @@ static inline pte_t pte_modify(pte_t pte
}
/*
- * Encode and decode a swap entry. Swap entries are stored in the Linux
- * page tables as follows:
+ * Encode/decode swap entries and swap PTEs. Swap PTEs are all PTEs that
+ * are !pte_none() && !pte_present().
+ *
+ * Format of swap PTEs:
*
* 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
+ * <------------------- offset ------------------> E < type -> 0 0
+ *
+ * E is the exclusive marker that is not stored in swap entries.
*
- * This gives us up to 31 swap files and 128GB 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 2
#define __SWP_TYPE_BITS 5
#define __SWP_TYPE_MASK ((1 << __SWP_TYPE_BITS) - 1)
-#define __SWP_OFFSET_SHIFT (__SWP_TYPE_BITS + __SWP_TYPE_SHIFT)
+#define __SWP_OFFSET_SHIFT (__SWP_TYPE_BITS + __SWP_TYPE_SHIFT + 1)
#define __swp_type(x) (((x).val >> __SWP_TYPE_SHIFT) & __SWP_TYPE_MASK)
#define __swp_offset(x) ((x).val >> __SWP_OFFSET_SHIFT)
-#define __swp_entry(type,offset) ((swp_entry_t) { ((type) << __SWP_TYPE_SHIFT) | ((offset) << __SWP_OFFSET_SHIFT) })
+#define __swp_entry(type, offset) ((swp_entry_t) { (((type) & __SWP_TYPE_BITS) << __SWP_TYPE_SHIFT) | \
+ ((offset) << __SWP_OFFSET_SHIFT) })
#define __pte_to_swp_entry(pte) ((swp_entry_t) { pte_val(pte) })
-#define __swp_entry_to_pte(swp) __pte((swp).val | PTE_TYPE_FAULT)
+#define __swp_entry_to_pte(swp) __pte((swp).val)
+
+#define __HAVE_ARCH_PTE_SWP_EXCLUSIVE
+static inline int pte_swp_exclusive(pte_t pte)
+{
+ return pte_isset(pte, L_PTE_SWP_EXCLUSIVE);
+}
+
+static inline pte_t pte_swp_mkexclusive(pte_t pte)
+{
+ return set_pte_bit(pte, __pgprot(L_PTE_SWP_EXCLUSIVE));
+}
+
+static inline pte_t pte_swp_clear_exclusive(pte_t pte)
+{
+ return clear_pte_bit(pte, __pgprot(L_PTE_SWP_EXCLUSIVE));
+}
/*
* It is an error for the kernel to have more swap files than we can
_
Patches currently in -mm which might be from david@xxxxxxxxxx are
mm-userfaultfd-rely-on-vma-vm_page_prot-in-uffd_wp_range.patch
mm-userfaultfd-rely-on-vma-vm_page_prot-in-uffd_wp_range-fix.patch
mm-mprotect-drop-pgprot_t-parameter-from-change_protection.patch
mm-mprotect-drop-pgprot_t-parameter-from-change_protection-fix.patch
selftests-vm-cow-add-cow-tests-for-collapsing-of-pte-mapped-anon-thp.patch
mm-nommu-factor-out-check-for-nommu-shared-mappings-into-is_nommu_shared_mapping.patch
mm-nommu-dont-use-vm_mayshare-for-map_private-mappings.patch
drivers-misc-open-dice-dont-touch-vm_mayshare.patch
selftests-mm-define-madv_pageout-to-fix-compilation-issues.patch
mm-debug_vm_pgtable-more-pte_swp_exclusive-sanity-checks.patch
alpha-mm-support-__have_arch_pte_swp_exclusive.patch
arc-mm-support-__have_arch_pte_swp_exclusive.patch
arm-mm-support-__have_arch_pte_swp_exclusive.patch
csky-mm-support-__have_arch_pte_swp_exclusive.patch
hexagon-mm-support-__have_arch_pte_swp_exclusive.patch
ia64-mm-support-__have_arch_pte_swp_exclusive.patch
loongarch-mm-support-__have_arch_pte_swp_exclusive.patch
m68k-mm-remove-dummy-__swp-definitions-for-nommu.patch
m68k-mm-support-__have_arch_pte_swp_exclusive.patch
microblaze-mm-support-__have_arch_pte_swp_exclusive.patch
mips-mm-support-__have_arch_pte_swp_exclusive.patch
nios2-mm-refactor-swap-pte-layout.patch
nios2-mm-support-__have_arch_pte_swp_exclusive.patch
openrisc-mm-support-__have_arch_pte_swp_exclusive.patch
parisc-mm-support-__have_arch_pte_swp_exclusive.patch
powerpc-mm-support-__have_arch_pte_swp_exclusive-on-32bit-book3s.patch
powerpc-nohash-mm-support-__have_arch_pte_swp_exclusive.patch
riscv-mm-support-__have_arch_pte_swp_exclusive.patch
sh-mm-support-__have_arch_pte_swp_exclusive.patch
sparc-mm-support-__have_arch_pte_swp_exclusive-on-32bit.patch
sparc-mm-support-__have_arch_pte_swp_exclusive-on-64bit.patch
um-mm-support-__have_arch_pte_swp_exclusive.patch
x86-mm-support-__have_arch_pte_swp_exclusive-also-on-32bit.patch
xtensa-mm-support-__have_arch_pte_swp_exclusive.patch
mm-remove-__have_arch_pte_swp_exclusive.patch
