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Message-Id: <20221206144730.163732-5-david@redhat.com>
Date: Tue, 6 Dec 2022 15:47:08 +0100
From: David Hildenbrand <david@...hat.com>
To: linux-kernel@...r.kernel.org
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Hugh Dickins <hughd@...gle.com>,
John Hubbard <jhubbard@...dia.com>,
Jason Gunthorpe <jgg@...dia.com>,
Mike Rapoport <rppt@...ux.ibm.com>,
Yang Shi <shy828301@...il.com>,
Vlastimil Babka <vbabka@...e.cz>,
Nadav Amit <namit@...are.com>,
Andrea Arcangeli <aarcange@...hat.com>,
Peter Xu <peterx@...hat.com>, linux-mm@...ck.org,
x86@...nel.org, linux-alpha@...r.kernel.org,
linux-snps-arc@...ts.infradead.org,
linux-arm-kernel@...ts.infradead.org, linux-csky@...r.kernel.org,
linux-hexagon@...r.kernel.org, linux-ia64@...r.kernel.org,
loongarch@...ts.linux.dev, linux-m68k@...ts.linux-m68k.org,
linux-mips@...r.kernel.org, openrisc@...ts.librecores.org,
linux-parisc@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
linux-riscv@...ts.infradead.org, linux-s390@...r.kernel.org,
linux-sh@...r.kernel.org, sparclinux@...r.kernel.org,
linux-um@...ts.infradead.org, linux-xtensa@...ux-xtensa.org,
David Hildenbrand <david@...hat.com>,
Russell King <linux@...linux.org.uk>
Subject: [PATCH mm-unstable RFC 04/26] arm/mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE
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().
Cc: Russell King <linux@...linux.org.uk>
Signed-off-by: David Hildenbrand <david@...hat.com>
---
arch/arm/include/asm/pgtable-2level.h | 3 +++
arch/arm/include/asm/pgtable-3level.h | 3 +++
arch/arm/include/asm/pgtable.h | 35 +++++++++++++++++++++------
3 files changed, 34 insertions(+), 7 deletions(-)
diff --git a/arch/arm/include/asm/pgtable-2level.h b/arch/arm/include/asm/pgtable-2level.h
index 92abd4cd8ca2..ce543cd9380c 100644
--- a/arch/arm/include/asm/pgtable-2level.h
+++ b/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
diff --git a/arch/arm/include/asm/pgtable-3level.h b/arch/arm/include/asm/pgtable-3level.h
index eabe72ff7381..106049791500 100644
--- a/arch/arm/include/asm/pgtable-3level.h
+++ b/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)
diff --git a/arch/arm/include/asm/pgtable.h b/arch/arm/include/asm/pgtable.h
index 00954ab1a039..5e0446a9c667 100644
--- a/arch/arm/include/asm/pgtable.h
+++ b/arch/arm/include/asm/pgtable.h
@@ -269,27 +269,48 @@ static inline pte_t pte_modify(pte_t pte, pgprot_t newprot)
}
/*
- * 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
--
2.38.1
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