[PATCH mm-unstable RFC 22/26] sparc/mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE on 64bit

David Hildenbrand
2022-12-06T15:11:54Z

Let's support __HAVE_ARCH_PTE_SWP_EXCLUSIVE by stealing one bit
from the type. Generic MM currently only uses 5 bits for the type
(MAX_SWAPFILES_SHIFT), so the stolen bit was effectively unused.

While at it, mask the type in __swp_entry().

Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
arch/sparc/include/asm/pgtable_64.h | 38 ++++++++++++++++++++++++++---
1 file changed, 35 insertions(+), 3 deletions(-)

diff --git a/arch/sparc/include/asm/pgtable_64.h b/arch/sparc/include/asm/pgtable_64.h
index 3bc9736bddb1..614fdedbb145 100644
--- a/arch/sparc/include/asm/pgtable_64.h
+++ b/arch/sparc/include/asm/pgtable_64.h
@@ -187,6 +187,9 @@ bool kern_addr_valid(unsigned long addr);
#define _PAGE_SZHUGE_4U _PAGE_SZ4MB_4U
#define _PAGE_SZHUGE_4V _PAGE_SZ4MB_4V

+/* We borrow bit 20 to store the exclusive marker in swap PTEs. */
+#define _PAGE_SWP_EXCLUSIVE _AC(0x0000000000100000,UL)
+
#ifndef __ASSEMBLY__

pte_t mk_pte_io(unsigned long, pgprot_t, int, unsigned long);
@@ -961,18 +964,47 @@ void pgtable_trans_huge_deposit(struct mm_struct *mm, pmd_t *pmdp,
pgtable_t pgtable_trans_huge_withdraw(struct mm_struct *mm, pmd_t *pmdp);
#endif

-/* Encode and de-code a swap entry */
-#define __swp_type(entry) (((entry).val >> PAGE_SHIFT) & 0xffUL)
+/*
+ * Encode/decode swap entries and swap PTEs. Swap PTEs are all PTEs that
+ * are !pte_none() && !pte_present().
+ *
+ * Format of swap PTEs:
+ *
+ * 6 6 6 6 5 5 5 5 5 5 5 5 5 5 4 4 4 4 4 4 4 4 4 4 3 3 3 3 3 3 3 3
+ * 3 2 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
+ * <--------------------------- offset ---------------------------
+ *
+ * 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
+ * --------------------> E <-- type ---> <------- zeroes -------->
+ */
+#define __swp_type(entry) (((entry).val >> PAGE_SHIFT) & 0x7fUL)
#define __swp_offset(entry) ((entry).val >> (PAGE_SHIFT + 8UL))
#define __swp_entry(type, offset) \
( (swp_entry_t) \
{ \
- (((long)(type) << PAGE_SHIFT) | \
+ ((((long)(type) & 0x7fUL) << PAGE_SHIFT) | \
((long)(offset) << (PAGE_SHIFT + 8UL))) \
} )
#define __pte_to_swp_entry(pte) ((swp_entry_t) { pte_val(pte) })
#define __swp_entry_to_pte(x) ((pte_t) { (x).val })

+#define __HAVE_ARCH_PTE_SWP_EXCLUSIVE
+static inline int pte_swp_exclusive(pte_t pte)
+{
+ return pte_val(pte) & _PAGE_SWP_EXCLUSIVE;
+}
+
+static inline pte_t pte_swp_mkexclusive(pte_t pte)
+{
+ return __pte(pte_val(pte) | _PAGE_SWP_EXCLUSIVE);
+}
+
+static inline pte_t pte_swp_clear_exclusive(pte_t pte)
+{
+ return __pte(pte_val(pte) & ~_PAGE_SWP_EXCLUSIVE);
+}
+
int page_in_phys_avail(unsigned long paddr);