[PATCH mm-unstable v1 07/26] ia64/mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE

David Hildenbrand
2023-01-13T17:14:38Z

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 is effectively unused.

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

Signed-off-by: David Hildenbrand <david@redhat.com>
---
arch/ia64/include/asm/pgtable.h | 32 +++++++++++++++++++++++++++++---
1 file changed, 29 insertions(+), 3 deletions(-)

diff --git a/arch/ia64/include/asm/pgtable.h b/arch/ia64/include/asm/pgtable.h
index 01517a5e6778..e4b8ab931399 100644
--- a/arch/ia64/include/asm/pgtable.h
+++ b/arch/ia64/include/asm/pgtable.h
@@ -58,6 +58,9 @@
#define _PAGE_ED (__IA64_UL(1) << 52) /* exception deferral */
#define _PAGE_PROTNONE (__IA64_UL(1) << 63)

+/* We borrow bit 7 to store the exclusive marker in swap PTEs. */
+#define _PAGE_SWP_EXCLUSIVE (1 << 7)
+
#define _PFN_MASK _PAGE_PPN_MASK
/* Mask of bits which may be changed by pte_modify(); the odd bits are there for _PAGE_PROTNONE */
#define _PAGE_CHG_MASK (_PAGE_P | _PAGE_PROTNONE | _PAGE_PL_MASK | _PAGE_AR_MASK | _PAGE_ED)
@@ -399,6 +402,9 @@ extern pgd_t swapper_pg_dir[PTRS_PER_PGD];
extern void paging_init (void);

/*
+ * Encode/decode swap entries and swap PTEs. Swap PTEs are all PTEs that
+ * are !pte_none() && !pte_present().
+ *
* Note: The macros below rely on the fact that MAX_SWAPFILES_SHIFT <= number of
* bits in the swap-type field of the swap pte. It would be nice to
* enforce that, but we can't easily include <linux/swap.h> here.
@@ -406,16 +412,36 @@ extern void paging_init (void);
*
* Format of swap pte:
* bit 0 : present bit (must be zero)
- * bits 1- 7: swap-type
+ * bits 1- 6: swap type
+ * bit 7 : exclusive marker
* bits 8-62: swap offset
* bit 63 : _PAGE_PROTNONE bit
*/
-#define __swp_type(entry) (((entry).val >> 1) & 0x7f)
+#define __swp_type(entry) (((entry).val >> 1) & 0x3f)
#define __swp_offset(entry) (((entry).val << 1) >> 9)
-#define __swp_entry(type,offset) ((swp_entry_t) { ((type) << 1) | ((long) (offset) << 8) })
+#define __swp_entry(type, offset) ((swp_entry_t) { ((type & 0x3f) << 1) | \
+ ((long) (offset) << 8) })
#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)
+{
+ pte_val(pte) |= _PAGE_SWP_EXCLUSIVE;
+ return pte;
+}
+
+static inline pte_t pte_swp_clear_exclusive(pte_t pte)
+{
+ pte_val(pte) &= ~_PAGE_SWP_EXCLUSIVE;
+ return pte;
+}
+
/*
* ZERO_PAGE is a global shared page that is always zero: used
* for zero-mapped memory areas etc..
--
2.39.0