thp: add x86 32bit support

Add support for transparent hugepages to x86 32bit.

Share the same VM_ bitflag for VM_MAPPED_COPY. mm/nommu.c will never
support transparent hugepages.

Signed-off-by: Johannes Weiner <[e-mail]>
Signed-off-by: Andrea Arcangeli <[e-mail]>
Reviewed-by: Rik van Riel <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

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

···
 #define native_ptep_get_and_clear(xp) native_local_ptep_get_and_clear(xp)
 #endif
 
+#ifdef CONFIG_SMP
+static inline pmd_t native_pmdp_get_and_clear(pmd_t *xp)
+{
+	return __pmd(xchg((pmdval_t *)xp, 0));
+}
+#else
+#define native_pmdp_get_and_clear(xp) native_local_pmdp_get_and_clear(xp)
+#endif
+
 /*
  * Bits _PAGE_BIT_PRESENT, _PAGE_BIT_FILE and _PAGE_BIT_PROTNONE are taken,
  * split up the 29 bits of offset into this range:

arch/x86/include/asm/pgtable-3level.h

···
 #define native_ptep_get_and_clear(xp) native_local_ptep_get_and_clear(xp)
 #endif
 
+#ifdef CONFIG_SMP
+union split_pmd {
+	struct {
+		u32 pmd_low;
+		u32 pmd_high;
+	};
+	pmd_t pmd;
+};
+static inline pmd_t native_pmdp_get_and_clear(pmd_t *pmdp)
+{
+	union split_pmd res, *orig = (union split_pmd *)pmdp;
+
+	/* xchg acts as a barrier before setting of the high bits */
+	res.pmd_low = xchg(&orig->pmd_low, 0);
+	res.pmd_high = orig->pmd_high;
+	orig->pmd_high = 0;
+
+	return res.pmd;
+}
+#else
+#define native_pmdp_get_and_clear(xp) native_local_pmdp_get_and_clear(xp)
+#endif
+
 /*
  * Bits 0, 6 and 7 are taken in the low part of the pte,
  * put the 32 bits of offset into the high part.

arch/x86/include/asm/pgtable.h

···
 	return pte_flags(pte) & _PAGE_ACCESSED;
 }
 
+static inline int pmd_young(pmd_t pmd)
+{
+	return pmd_flags(pmd) & _PAGE_ACCESSED;
+}
+
 static inline int pte_write(pte_t pte)
 {
 	return pte_flags(pte) & _PAGE_RW;
···
 	return (pmd_flags(pte) & (_PAGE_PSE | _PAGE_PRESENT)) ==
 		(_PAGE_PSE | _PAGE_PRESENT);
 }
+
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+static inline int pmd_trans_splitting(pmd_t pmd)
+{
+	return pmd_val(pmd) & _PAGE_SPLITTING;
+}
+
+static inline int pmd_trans_huge(pmd_t pmd)
+{
+	return pmd_val(pmd) & _PAGE_PSE;
+}
+#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 
 static inline pte_t pte_set_flags(pte_t pte, pteval_t set)
 {
···
 static inline pte_t pte_mkspecial(pte_t pte)
 {
 	return pte_set_flags(pte, _PAGE_SPECIAL);
+}
+
+static inline pmd_t pmd_set_flags(pmd_t pmd, pmdval_t set)
+{
+	pmdval_t v = native_pmd_val(pmd);
+
+	return __pmd(v | set);
+}
+
+static inline pmd_t pmd_clear_flags(pmd_t pmd, pmdval_t clear)
+{
+	pmdval_t v = native_pmd_val(pmd);
+
+	return __pmd(v & ~clear);
+}
+
+static inline pmd_t pmd_mkold(pmd_t pmd)
+{
+	return pmd_clear_flags(pmd, _PAGE_ACCESSED);
+}
+
+static inline pmd_t pmd_wrprotect(pmd_t pmd)
+{
+	return pmd_clear_flags(pmd, _PAGE_RW);
+}
+
+static inline pmd_t pmd_mkdirty(pmd_t pmd)
+{
+	return pmd_set_flags(pmd, _PAGE_DIRTY);
+}
+
+static inline pmd_t pmd_mkhuge(pmd_t pmd)
+{
+	return pmd_set_flags(pmd, _PAGE_PSE);
+}
+
+static inline pmd_t pmd_mkyoung(pmd_t pmd)
+{
+	return pmd_set_flags(pmd, _PAGE_ACCESSED);
+}
+
+static inline pmd_t pmd_mkwrite(pmd_t pmd)
+{
+	return pmd_set_flags(pmd, _PAGE_RW);
+}
+
+static inline pmd_t pmd_mknotpresent(pmd_t pmd)
+{
+	return pmd_clear_flags(pmd, _PAGE_PRESENT);
 }
 
 /*
···
 	return res;
 }
 
+static inline pmd_t native_local_pmdp_get_and_clear(pmd_t *pmdp)
+{
+	pmd_t res = *pmdp;
+
+	native_pmd_clear(pmdp);
+	return res;
+}
+
 static inline void native_set_pte_at(struct mm_struct *mm, unsigned long addr,
 				     pte_t *ptep , pte_t pte)
 {
···
 }
 
 #define flush_tlb_fix_spurious_fault(vma, address)
+
+#define mk_pmd(page, pgprot)   pfn_pmd(page_to_pfn(page), (pgprot))
+
+#define  __HAVE_ARCH_PMDP_SET_ACCESS_FLAGS
+extern int pmdp_set_access_flags(struct vm_area_struct *vma,
+				 unsigned long address, pmd_t *pmdp,
+				 pmd_t entry, int dirty);
+
+#define __HAVE_ARCH_PMDP_TEST_AND_CLEAR_YOUNG
+extern int pmdp_test_and_clear_young(struct vm_area_struct *vma,
+				     unsigned long addr, pmd_t *pmdp);
+
+#define __HAVE_ARCH_PMDP_CLEAR_YOUNG_FLUSH
+extern int pmdp_clear_flush_young(struct vm_area_struct *vma,
+				  unsigned long address, pmd_t *pmdp);
+
+
+#define __HAVE_ARCH_PMDP_SPLITTING_FLUSH
+extern void pmdp_splitting_flush(struct vm_area_struct *vma,
+				 unsigned long addr, pmd_t *pmdp);
+
+#define __HAVE_ARCH_PMD_WRITE
+static inline int pmd_write(pmd_t pmd)
+{
+	return pmd_flags(pmd) & _PAGE_RW;
+}
+
+#define __HAVE_ARCH_PMDP_GET_AND_CLEAR
+static inline pmd_t pmdp_get_and_clear(struct mm_struct *mm, unsigned long addr,
+				       pmd_t *pmdp)
+{
+	pmd_t pmd = native_pmdp_get_and_clear(pmdp);
+	pmd_update(mm, addr, pmdp);
+	return pmd;
+}
+
+#define __HAVE_ARCH_PMDP_SET_WRPROTECT
+static inline void pmdp_set_wrprotect(struct mm_struct *mm,
+				      unsigned long addr, pmd_t *pmdp)
+{
+	clear_bit(_PAGE_BIT_RW, (unsigned long *)pmdp);
+	pmd_update(mm, addr, pmdp);
+}
 
 /*
  * clone_pgd_range(pgd_t *dst, pgd_t *src, int count);

arch/x86/include/asm/pgtable_64.h

···
 
 #define __HAVE_ARCH_PTE_SAME
 
-#ifdef CONFIG_TRANSPARENT_HUGEPAGE
-static inline int pmd_trans_splitting(pmd_t pmd)
-{
-	return pmd_val(pmd) & _PAGE_SPLITTING;
-}
-
-static inline int pmd_trans_huge(pmd_t pmd)
-{
-	return pmd_val(pmd) & _PAGE_PSE;
-}
-#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
-
-#define mk_pmd(page, pgprot)   pfn_pmd(page_to_pfn(page), (pgprot))
-
-#define  __HAVE_ARCH_PMDP_SET_ACCESS_FLAGS
-extern int pmdp_set_access_flags(struct vm_area_struct *vma,
-				 unsigned long address, pmd_t *pmdp,
-				 pmd_t entry, int dirty);
-
-#define __HAVE_ARCH_PMDP_TEST_AND_CLEAR_YOUNG
-extern int pmdp_test_and_clear_young(struct vm_area_struct *vma,
-				     unsigned long addr, pmd_t *pmdp);
-
-#define __HAVE_ARCH_PMDP_CLEAR_YOUNG_FLUSH
-extern int pmdp_clear_flush_young(struct vm_area_struct *vma,
-				  unsigned long address, pmd_t *pmdp);
-
-
-#define __HAVE_ARCH_PMDP_SPLITTING_FLUSH
-extern void pmdp_splitting_flush(struct vm_area_struct *vma,
-				 unsigned long addr, pmd_t *pmdp);
-
-#define __HAVE_ARCH_PMD_WRITE
-static inline int pmd_write(pmd_t pmd)
-{
-	return pmd_flags(pmd) & _PAGE_RW;
-}
-
-#define __HAVE_ARCH_PMDP_GET_AND_CLEAR
-static inline pmd_t pmdp_get_and_clear(struct mm_struct *mm, unsigned long addr,
-				       pmd_t *pmdp)
-{
-	pmd_t pmd = native_pmdp_get_and_clear(pmdp);
-	pmd_update(mm, addr, pmdp);
-	return pmd;
-}
-
-#define __HAVE_ARCH_PMDP_SET_WRPROTECT
-static inline void pmdp_set_wrprotect(struct mm_struct *mm,
-				      unsigned long addr, pmd_t *pmdp)
-{
-	clear_bit(_PAGE_BIT_RW, (unsigned long *)&pmdp->pmd);
-	pmd_update(mm, addr, pmdp);
-}
-
-static inline int pmd_young(pmd_t pmd)
-{
-	return pmd_flags(pmd) & _PAGE_ACCESSED;
-}
-
-static inline pmd_t pmd_set_flags(pmd_t pmd, pmdval_t set)
-{
-	pmdval_t v = native_pmd_val(pmd);
-
-	return native_make_pmd(v | set);
-}
-
-static inline pmd_t pmd_clear_flags(pmd_t pmd, pmdval_t clear)
-{
-	pmdval_t v = native_pmd_val(pmd);
-
-	return native_make_pmd(v & ~clear);
-}
-
-static inline pmd_t pmd_mkold(pmd_t pmd)
-{
-	return pmd_clear_flags(pmd, _PAGE_ACCESSED);
-}
-
-static inline pmd_t pmd_wrprotect(pmd_t pmd)
-{
-	return pmd_clear_flags(pmd, _PAGE_RW);
-}
-
-static inline pmd_t pmd_mkdirty(pmd_t pmd)
-{
-	return pmd_set_flags(pmd, _PAGE_DIRTY);
-}
-
-static inline pmd_t pmd_mkhuge(pmd_t pmd)
-{
-	return pmd_set_flags(pmd, _PAGE_PSE);
-}
-
-static inline pmd_t pmd_mkyoung(pmd_t pmd)
-{
-	return pmd_set_flags(pmd, _PAGE_ACCESSED);
-}
-
-static inline pmd_t pmd_mkwrite(pmd_t pmd)
-{
-	return pmd_set_flags(pmd, _PAGE_RW);
-}
-
-static inline pmd_t pmd_mknotpresent(pmd_t pmd)
-{
-	return pmd_clear_flags(pmd, _PAGE_PRESENT);
-}
-
 #endif /* !__ASSEMBLY__ */
 
 #endif /* _ASM_X86_PGTABLE_64_H */

arch/x86/mm/pgtable.c

···
 
 	if (pmd_young(*pmdp))
 		ret = test_and_clear_bit(_PAGE_BIT_ACCESSED,
-					 (unsigned long *) &pmdp->pmd);
+					 (unsigned long *)pmdp);
 
 	if (ret)
 		pmd_update(vma->vm_mm, addr, pmdp);
···
 	int set;
 	VM_BUG_ON(address & ~HPAGE_PMD_MASK);
 	set = !test_and_set_bit(_PAGE_BIT_SPLITTING,
-				(unsigned long *)&pmdp->pmd);
+				(unsigned long *)pmdp);
 	if (set) {
 		pmd_update(vma->vm_mm, address, pmdp);
 		/* need tlb flush only to serialize against gup-fast */

include/linux/mm.h

···
 #define VM_NORESERVE	0x00200000	/* should the VM suppress accounting */
 #define VM_HUGETLB	0x00400000	/* Huge TLB Page VM */
 #define VM_NONLINEAR	0x00800000	/* Is non-linear (remap_file_pages) */
+#ifndef CONFIG_TRANSPARENT_HUGEPAGE
 #define VM_MAPPED_COPY	0x01000000	/* T if mapped copy of data (nommu mmap) */
+#else
+#define VM_HUGEPAGE	0x01000000	/* MADV_HUGEPAGE marked this vma */
+#endif
 #define VM_INSERTPAGE	0x02000000	/* The vma has had "vm_insert_page()" done on it */
 #define VM_ALWAYSDUMP	0x04000000	/* Always include in core dumps */
 
···
 #define VM_SAO		0x20000000	/* Strong Access Ordering (powerpc) */
 #define VM_PFN_AT_MMAP	0x40000000	/* PFNMAP vma that is fully mapped at mmap time */
 #define VM_MERGEABLE	0x80000000	/* KSM may merge identical pages */
-#if BITS_PER_LONG > 32
-#define VM_HUGEPAGE	0x100000000UL	/* MADV_HUGEPAGE marked this vma */
-#endif
 
 /* Bits set in the VMA until the stack is in its final location */
 #define VM_STACK_INCOMPLETE_SETUP	(VM_RAND_READ | VM_SEQ_READ)

mm/Kconfig

···
 
 config TRANSPARENT_HUGEPAGE
 	bool "Transparent Hugepage Support" if EMBEDDED
-	depends on X86_64 && MMU
+	depends on X86 && MMU
 	default y
 	help
 	  Transparent Hugepages allows the kernel to use huge pages and