5 files changed, 75 insertions, 19 deletions

diff --git a/arch/x86/include/asm/pgtable-2level.h b/arch/x86/include/asm/pgtable-2level.h
index b17edfd23628..e0d199fe1d83 100644
--- a/arch/x86/include/asm/pgtable-2level.h
+++ b/arch/x86/include/asm/pgtable-2level.h
@@ -56,23 +56,55 @@ static inline pte_t native_ptep_get_and_clear(pte_t *xp)
 #define pte_none(x)             (!(x).pte_low)
 
 /*
- * Bits 0, 6 and 7 are taken, split up the 29 bits of offset
- * into this range:
+ * Bits _PAGE_BIT_PRESENT, _PAGE_BIT_FILE and _PAGE_BIT_PROTNONE are taken,
+ * split up the 29 bits of offset into this range:
  */
 #define PTE_FILE_MAX_BITS       29
+#define PTE_FILE_SHIFT1         (_PAGE_BIT_PRESENT + 1)
+#if _PAGE_BIT_FILE < _PAGE_BIT_PROTNONE
+#define PTE_FILE_SHIFT2         (_PAGE_BIT_FILE + 1)
+#define PTE_FILE_SHIFT3         (_PAGE_BIT_PROTNONE + 1)
+#else
+#define PTE_FILE_SHIFT2         (_PAGE_BIT_PROTNONE + 1)
+#define PTE_FILE_SHIFT3         (_PAGE_BIT_FILE + 1)
+#endif
+#define PTE_FILE_BITS1          (PTE_FILE_SHIFT2 - PTE_FILE_SHIFT1 - 1)
+#define PTE_FILE_BITS2          (PTE_FILE_SHIFT3 - PTE_FILE_SHIFT2 - 1)
 
 #define pte_to_pgoff(pte)                                               \
-        ((((pte).pte_low >> 1) & 0x1f) + (((pte).pte_low >> 8) << 5))
+        ((((pte).pte_low >> PTE_FILE_SHIFT1)                            \
+          & ((1U << PTE_FILE_BITS1) - 1))                               \
+         + ((((pte).pte_low >> PTE_FILE_SHIFT2)                         \
+             & ((1U << PTE_FILE_BITS2) - 1)) << PTE_FILE_BITS1)         \
+         + (((pte).pte_low >> PTE_FILE_SHIFT3)                          \
+            << (PTE_FILE_BITS1 + PTE_FILE_BITS2)))
 
 #define pgoff_to_pte(off)                                               \
-        ((pte_t) { .pte_low = (((off) & 0x1f) << 1) +                   \
-                        (((off) >> 5) << 8) + _PAGE_FILE })
+        ((pte_t) { .pte_low =                                           \
+         (((off) & ((1U << PTE_FILE_BITS1) - 1)) << PTE_FILE_SHIFT1)    \
+         + ((((off) >> PTE_FILE_BITS1) & ((1U << PTE_FILE_BITS2) - 1))  \
+            << PTE_FILE_SHIFT2)                                         \
+         + (((off) >> (PTE_FILE_BITS1 + PTE_FILE_BITS2))                \
+            << PTE_FILE_SHIFT3)                                         \
+         + _PAGE_FILE })
 
 /* Encode and de-code a swap entry */
-#define __swp_type(x)                   (((x).val >> 1) & 0x1f)
-#define __swp_offset(x)                 ((x).val >> 8)
-#define __swp_entry(type, offset)                               \
-        ((swp_entry_t) { ((type) << 1) | ((offset) << 8) })
+#if _PAGE_BIT_FILE < _PAGE_BIT_PROTNONE
+#define SWP_TYPE_BITS (_PAGE_BIT_FILE - _PAGE_BIT_PRESENT - 1)
+#define SWP_OFFSET_SHIFT (_PAGE_BIT_PROTNONE + 1)
+#else
+#define SWP_TYPE_BITS (_PAGE_BIT_PROTNONE - _PAGE_BIT_PRESENT - 1)
+#define SWP_OFFSET_SHIFT (_PAGE_BIT_FILE + 1)
+#endif
+
+#define MAX_SWAPFILES_CHECK() BUILD_BUG_ON(MAX_SWAPFILES_SHIFT > SWP_TYPE_BITS)
+
+#define __swp_type(x)                   (((x).val >> (_PAGE_BIT_PRESENT + 1)) \
+                                         & ((1U << SWP_TYPE_BITS) - 1))
+#define __swp_offset(x)                 ((x).val >> SWP_OFFSET_SHIFT)
+#define __swp_entry(type, offset)       ((swp_entry_t) { \
+                                         ((type) << (_PAGE_BIT_PRESENT + 1)) \
+                                         | ((offset) << SWP_OFFSET_SHIFT) })
 #define __pte_to_swp_entry(pte)         ((swp_entry_t) { (pte).pte_low })
 #define __swp_entry_to_pte(x)           ((pte_t) { .pte = (x).val })
 
diff --git a/arch/x86/include/asm/pgtable-3level.h b/arch/x86/include/asm/pgtable-3level.h
index 52597aeadfff..447da43cddb3 100644
--- a/arch/x86/include/asm/pgtable-3level.h
+++ b/arch/x86/include/asm/pgtable-3level.h
@@ -166,6 +166,7 @@ static inline int pte_none(pte_t pte)
 #define PTE_FILE_MAX_BITS       32
 
 /* Encode and de-code a swap entry */
+#define MAX_SWAPFILES_CHECK() BUILD_BUG_ON(MAX_SWAPFILES_SHIFT > 5)
 #define __swp_type(x)                   (((x).val) & 0x1f)
 #define __swp_offset(x)                 ((x).val >> 5)
 #define __swp_entry(type, offset)       ((swp_entry_t){(type) | (offset) << 5})
diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index c012f3b11671..b7c2ecdb7658 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -10,7 +10,6 @@
 #define _PAGE_BIT_PCD           4       /* page cache disabled */
 #define _PAGE_BIT_ACCESSED      5       /* was accessed (raised by CPU) */
 #define _PAGE_BIT_DIRTY         6       /* was written to (raised by CPU) */
-#define _PAGE_BIT_FILE          6
 #define _PAGE_BIT_PSE           7       /* 4 MB (or 2MB) page */
 #define _PAGE_BIT_PAT           7       /* on 4KB pages */
 #define _PAGE_BIT_GLOBAL        8       /* Global TLB entry PPro+ */
@@ -22,6 +21,12 @@
 #define _PAGE_BIT_CPA_TEST      _PAGE_BIT_UNUSED1
 #define _PAGE_BIT_NX           63       /* No execute: only valid after cpuid check */
 
+/* If _PAGE_BIT_PRESENT is clear, we use these: */
+/* - if the user mapped it with PROT_NONE; pte_present gives true */
+#define _PAGE_BIT_PROTNONE      _PAGE_BIT_GLOBAL
+/* - set: nonlinear file mapping, saved PTE; unset:swap */
+#define _PAGE_BIT_FILE          _PAGE_BIT_DIRTY
+
 #define _PAGE_PRESENT   (_AT(pteval_t, 1) << _PAGE_BIT_PRESENT)
 #define _PAGE_RW        (_AT(pteval_t, 1) << _PAGE_BIT_RW)
 #define _PAGE_USER      (_AT(pteval_t, 1) << _PAGE_BIT_USER)
@@ -46,11 +51,8 @@
 #define _PAGE_NX        (_AT(pteval_t, 0))
 #endif
 
-/* If _PAGE_PRESENT is clear, we use these: */
-#define _PAGE_FILE      _PAGE_DIRTY     /* nonlinear file mapping,
-                                         * saved PTE; unset:swap */
-#define _PAGE_PROTNONE  _PAGE_PSE       /* if the user mapped it with PROT_NONE;
-                                           pte_present gives true */
+#define _PAGE_FILE      (_AT(pteval_t, 1) << _PAGE_BIT_FILE)
+#define _PAGE_PROTNONE  (_AT(pteval_t, 1) << _PAGE_BIT_PROTNONE)
 
 #define _PAGE_TABLE     (_PAGE_PRESENT | _PAGE_RW | _PAGE_USER |        \
                          _PAGE_ACCESSED | _PAGE_DIRTY)
diff --git a/arch/x86/include/asm/pgtable_64.h b/arch/x86/include/asm/pgtable_64.h
index 545a0e042bb2..65b6be6677c7 100644
--- a/arch/x86/include/asm/pgtable_64.h
+++ b/arch/x86/include/asm/pgtable_64.h
@@ -250,10 +250,22 @@ static inline int pud_large(pud_t pte)
 extern int direct_gbpages;
 
 /* Encode and de-code a swap entry */
-#define __swp_type(x)                   (((x).val >> 1) & 0x3f)
-#define __swp_offset(x)                 ((x).val >> 8)
-#define __swp_entry(type, offset)       ((swp_entry_t) { ((type) << 1) | \
-                                                         ((offset) << 8) })
+#if _PAGE_BIT_FILE < _PAGE_BIT_PROTNONE
+#define SWP_TYPE_BITS (_PAGE_BIT_FILE - _PAGE_BIT_PRESENT - 1)
+#define SWP_OFFSET_SHIFT (_PAGE_BIT_PROTNONE + 1)
+#else
+#define SWP_TYPE_BITS (_PAGE_BIT_PROTNONE - _PAGE_BIT_PRESENT - 1)
+#define SWP_OFFSET_SHIFT (_PAGE_BIT_FILE + 1)
+#endif
+
+#define MAX_SWAPFILES_CHECK() BUILD_BUG_ON(MAX_SWAPFILES_SHIFT > SWP_TYPE_BITS)
+
+#define __swp_type(x)                   (((x).val >> (_PAGE_BIT_PRESENT + 1)) \
+                                         & ((1U << SWP_TYPE_BITS) - 1))
+#define __swp_offset(x)                 ((x).val >> SWP_OFFSET_SHIFT)
+#define __swp_entry(type, offset)       ((swp_entry_t) { \
+                                         ((type) << (_PAGE_BIT_PRESENT + 1)) \
+                                         | ((offset) << SWP_OFFSET_SHIFT) })
 #define __pte_to_swp_entry(pte)         ((swp_entry_t) { pte_val((pte)) })
 #define __swp_entry_to_pte(x)           ((pte_t) { .pte = (x).val })
 
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 90cb67a5417c..54a9f87e5162 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1462,6 +1462,15 @@ static int __init procswaps_init(void)
 __initcall(procswaps_init);
 #endif /* CONFIG_PROC_FS */
 
+#ifdef MAX_SWAPFILES_CHECK
+static int __init max_swapfiles_check(void)
+{
+        MAX_SWAPFILES_CHECK();
+        return 0;
+}
+late_initcall(max_swapfiles_check);
+#endif
+
 /*
  * Written 01/25/92 by Simmule Turner, heavily changed by Linus.
  *