mm: x86 pgtable: require X86_64 for soft-dirty tracker

Tracking dirty status on 2 level pages requires very ugly macros and
taking into account how old the machines who can operate without PAE
mode only are, lets drop soft dirty tracker from them for code
simplicity (note I can't drop all the macros from 2 level pages by now
since _PAGE_BIT_PROTNONE and _PAGE_BIT_FILE are still used even without
tracker).

Linus proposed to completely rip off softdirty support on x86-32 (even
with PAE) and since for CRIU we're not planning to support native x86-32
mode, lets do that.

(Softdirty tracker is relatively new feature which is mostly used by
CRIU so I don't expect if such API change would cause problems for
userspace).
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Steven Noonan <steven@uplinklabs.net>
Cc: Rik van Riel <riel@redhat.com>
Cc: David Vrabel <david.vrabel@citrix.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Pavel Emelyanov <xemul@parallels.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/x86/Kconfig

@@ -105,7 +105,7 @@ config X86
 	select HAVE_ARCH_SECCOMP_FILTER
 	select BUILDTIME_EXTABLE_SORT
 	select GENERIC_CMOS_UPDATE
-	select HAVE_ARCH_SOFT_DIRTY
+	select HAVE_ARCH_SOFT_DIRTY if X86_64
 	select CLOCKSOURCE_WATCHDOG
 	select GENERIC_CLOCKEVENTS
 	select ARCH_CLOCKSOURCE_DATA

arch/x86/include/asm/pgtable-2level.h

@@ -62,53 +62,6 @@ static inline unsigned long pte_bitop(unsigned long value, unsigned int rightshi
 	return ((value >> rightshift) & mask) << leftshift;
 }
 
-#ifdef CONFIG_MEM_SOFT_DIRTY
-
-/*
- * Bits _PAGE_BIT_PRESENT, _PAGE_BIT_FILE, _PAGE_BIT_SOFT_DIRTY and
- * _PAGE_BIT_PROTNONE are taken, split up the 28 bits of offset
- * into this range.
- */
-#define PTE_FILE_MAX_BITS	28
-#define PTE_FILE_SHIFT1		(_PAGE_BIT_PRESENT + 1)
-#define PTE_FILE_SHIFT2		(_PAGE_BIT_FILE + 1)
-#define PTE_FILE_SHIFT3		(_PAGE_BIT_PROTNONE + 1)
-#define PTE_FILE_SHIFT4		(_PAGE_BIT_SOFT_DIRTY + 1)
-#define PTE_FILE_BITS1		(PTE_FILE_SHIFT2 - PTE_FILE_SHIFT1 - 1)
-#define PTE_FILE_BITS2		(PTE_FILE_SHIFT3 - PTE_FILE_SHIFT2 - 1)
-#define PTE_FILE_BITS3		(PTE_FILE_SHIFT4 - PTE_FILE_SHIFT3 - 1)
-
-#define PTE_FILE_MASK1		((1U << PTE_FILE_BITS1) - 1)
-#define PTE_FILE_MASK2		((1U << PTE_FILE_BITS2) - 1)
-#define PTE_FILE_MASK3		((1U << PTE_FILE_BITS3) - 1)
-
-#define PTE_FILE_LSHIFT2	(PTE_FILE_BITS1)
-#define PTE_FILE_LSHIFT3	(PTE_FILE_BITS1 + PTE_FILE_BITS2)
-#define PTE_FILE_LSHIFT4	(PTE_FILE_BITS1 + PTE_FILE_BITS2 + PTE_FILE_BITS3)
-
-static __always_inline pgoff_t pte_to_pgoff(pte_t pte)
-{
-	return (pgoff_t)
-		(pte_bitop(pte.pte_low, PTE_FILE_SHIFT1, PTE_FILE_MASK1,  0)		    +
-		 pte_bitop(pte.pte_low, PTE_FILE_SHIFT2, PTE_FILE_MASK2,  PTE_FILE_LSHIFT2) +
-		 pte_bitop(pte.pte_low, PTE_FILE_SHIFT3, PTE_FILE_MASK3,  PTE_FILE_LSHIFT3) +
-		 pte_bitop(pte.pte_low, PTE_FILE_SHIFT4,           -1UL,  PTE_FILE_LSHIFT4));
-}
-
-static __always_inline pte_t pgoff_to_pte(pgoff_t off)
-{
-	return (pte_t){
-		.pte_low =
-			pte_bitop(off,                0, PTE_FILE_MASK1,  PTE_FILE_SHIFT1) +
-			pte_bitop(off, PTE_FILE_LSHIFT2, PTE_FILE_MASK2,  PTE_FILE_SHIFT2) +
-			pte_bitop(off, PTE_FILE_LSHIFT3, PTE_FILE_MASK3,  PTE_FILE_SHIFT3) +
-			pte_bitop(off, PTE_FILE_LSHIFT4,           -1UL,  PTE_FILE_SHIFT4) +
-			_PAGE_FILE,
-	};
-}
-
-#else /* CONFIG_MEM_SOFT_DIRTY */
-
 /*
  * Bits _PAGE_BIT_PRESENT, _PAGE_BIT_FILE and _PAGE_BIT_PROTNONE are taken,
  * split up the 29 bits of offset into this range.
@@ -145,8 +98,6 @@ static __always_inline pte_t pgoff_to_pte(pgoff_t off)
 	};
 }
 
-#endif /* CONFIG_MEM_SOFT_DIRTY */
-
 /* Encode and de-code a swap entry */
 #define SWP_TYPE_BITS (_PAGE_BIT_FILE - _PAGE_BIT_PRESENT - 1)
 #define SWP_OFFSET_SHIFT (_PAGE_BIT_PROTNONE + 1)

arch/x86/include/asm/pgtable.h

@@ -297,6 +297,7 @@ static inline pmd_t pmd_mknotpresent(pmd_t pmd)
 	return pmd_clear_flags(pmd, _PAGE_PRESENT);
 }
 
+#ifdef CONFIG_HAVE_ARCH_SOFT_DIRTY
 static inline int pte_soft_dirty(pte_t pte)
 {
 	return pte_flags(pte) & _PAGE_SOFT_DIRTY;
@@ -332,6 +333,8 @@ static inline int pte_file_soft_dirty(pte_t pte)
 	return pte_flags(pte) & _PAGE_SOFT_DIRTY;
 }
 
+#endif /* CONFIG_HAVE_ARCH_SOFT_DIRTY */
+
 /*
  * Mask out unsupported bits in a present pgprot.  Non-present pgprots
  * can use those bits for other purposes, so leave them be.
@@ -865,6 +868,7 @@ static inline void update_mmu_cache_pmd(struct vm_area_struct *vma,
 {
 }
 
+#ifdef CONFIG_HAVE_ARCH_SOFT_DIRTY
 static inline pte_t pte_swp_mksoft_dirty(pte_t pte)
 {
 	VM_BUG_ON(pte_present_nonuma(pte));
@@ -882,6 +886,7 @@ static inline pte_t pte_swp_clear_soft_dirty(pte_t pte)
 	VM_BUG_ON(pte_present_nonuma(pte));
 	return pte_clear_flags(pte, _PAGE_SWP_SOFT_DIRTY);
 }
+#endif
 
 #include <asm-generic/pgtable.h>
 #endif	/* __ASSEMBLY__ */