mm: remove misleading ARCH_USES_NUMA_PROT_NONE

ARCH_USES_NUMA_PROT_NONE was defined for architectures that implemented
_PAGE_NUMA using _PROT_NONE.  This saved using an additional PTE bit and
relied on the fact that PROT_NONE vmas were skipped by the NUMA hinting
fault scanner.  This was found to be conceptually confusing with a lot of
implicit assumptions and it was asked that an alternative be found.

Commit c46a7c81 "x86: define _PAGE_NUMA by reusing software bits on the
PMD and PTE levels" redefined _PAGE_NUMA on x86 to be one of the swap PTE
bits and shrunk the maximum possible swap size but it did not go far
enough.  There are no architectures that reuse _PROT_NONE as _PROT_NUMA
but the relics still exist.

This patch removes ARCH_USES_NUMA_PROT_NONE and removes some unnecessary
duplication in powerpc vs the generic implementation by defining the types
the core NUMA helpers expected to exist from x86 with their ppc64
equivalent.  This necessitated that a PTE bit mask be created that
identified the bits that distinguish present from NUMA pte entries but it
is expected this will only differ between arches based on _PAGE_PROTNONE.
The naming for the generic helpers was taken from x86 originally but ppc64
has types that are equivalent for the purposes of the helper so they are
mapped instead of duplicating code.

Signed-off-by: Mel Gorman <mgorman@suse.de>
Cc: Hugh Dickins <hughd@google.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Cyrill Gorcunov <gorcunov@gmail.com>
Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 9 insertions, 18 deletions

diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
index 53b2acc..281870f 100644
--- a/include/asm-generic/pgtable.h
+++ b/include/asm-generic/pgtable.h
@@ -660,11 +660,12 @@ static inline int pmd_trans_unstable(pmd_t *pmd)
 }
 
 #ifdef CONFIG_NUMA_BALANCING
-#ifdef CONFIG_ARCH_USES_NUMA_PROT_NONE
 /*
- * _PAGE_NUMA works identical to _PAGE_PROTNONE (it's actually the
- * same bit too). It's set only when _PAGE_PRESET is not set and it's
- * never set if _PAGE_PRESENT is set.
+ * _PAGE_NUMA distinguishes between an unmapped page table entry, an entry that
+ * is protected for PROT_NONE and a NUMA hinting fault entry. If the
+ * architecture defines __PAGE_PROTNONE then it should take that into account
+ * but those that do not can rely on the fact that the NUMA hinting scanner
+ * skips inaccessible VMAs.
  *
  * pte/pmd_present() returns true if pte/pmd_numa returns true. Page
  * fault triggers on those regions if pte/pmd_numa returns true
@@ -673,16 +674,14 @@ static inline int pmd_trans_unstable(pmd_t *pmd)
 #ifndef pte_numa
 static inline int pte_numa(pte_t pte)
 {
-	return (pte_flags(pte) &
-		(_PAGE_NUMA|_PAGE_PROTNONE|_PAGE_PRESENT)) == _PAGE_NUMA;
+	return ptenuma_flags(pte) == _PAGE_NUMA;
 }
 #endif
 
 #ifndef pmd_numa
 static inline int pmd_numa(pmd_t pmd)
 {
-	return (pmd_flags(pmd) &
-		(_PAGE_NUMA|_PAGE_PROTNONE|_PAGE_PRESENT)) == _PAGE_NUMA;
+	return pmdnuma_flags(pmd) == _PAGE_NUMA;
 }
 #endif
 
@@ -722,6 +721,8 @@ static inline pte_t pte_mknuma(pte_t pte)
 {
 	pteval_t val = pte_val(pte);
 
+	VM_BUG_ON(!(val & _PAGE_PRESENT));
+
 	val &= ~_PAGE_PRESENT;
 	val |= _PAGE_NUMA;
 
@@ -765,16 +766,6 @@ static inline void pmdp_set_numa(struct mm_struct *mm, unsigned long addr,
 }
 #endif
 #else
-extern int pte_numa(pte_t pte);
-extern int pmd_numa(pmd_t pmd);
-extern pte_t pte_mknonnuma(pte_t pte);
-extern pmd_t pmd_mknonnuma(pmd_t pmd);
-extern pte_t pte_mknuma(pte_t pte);
-extern pmd_t pmd_mknuma(pmd_t pmd);
-extern void ptep_set_numa(struct mm_struct *mm, unsigned long addr, pte_t *ptep);
-extern void pmdp_set_numa(struct mm_struct *mm, unsigned long addr, pmd_t *pmdp);
-#endif /* CONFIG_ARCH_USES_NUMA_PROT_NONE */
-#else
 static inline int pmd_numa(pmd_t pmd)
 {
 	return 0;