x86: mm: Remove x86 version of huge_pmd_share.

The huge_pmd_share code has been copied over to mm/hugetlb.c to
make it accessible to other architectures.

Remove the x86 copy of the huge_pmd_share code and enable the
ARCH_WANT_HUGE_PMD_SHARE config flag. That way we reference the
general one.

Signed-off-by: Steve Capper <steve.capper@linaro.org>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Andrew Morton <akpm@linux-foundation.org>

2 files changed, 3 insertions, 120 deletions

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 685692c94f05..476f786c11e9 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -207,6 +207,9 @@ config ARCH_HIBERNATION_POSSIBLE
 config ARCH_SUSPEND_POSSIBLE
         def_bool y
 
+config ARCH_WANT_HUGE_PMD_SHARE
+        def_bool y
+
 config ZONE_DMA32
         bool
         default X86_64
diff --git a/arch/x86/mm/hugetlbpage.c b/arch/x86/mm/hugetlbpage.c
index ae1aa71d0115..7e522a359972 100644
--- a/arch/x86/mm/hugetlbpage.c
+++ b/arch/x86/mm/hugetlbpage.c
@@ -16,126 +16,6 @@
 #include <asm/tlbflush.h>
 #include <asm/pgalloc.h>
 
-static unsigned long page_table_shareable(struct vm_area_struct *svma,
-                                struct vm_area_struct *vma,
-                                unsigned long addr, pgoff_t idx)
-{
-        unsigned long saddr = ((idx - svma->vm_pgoff) << PAGE_SHIFT) +
-                                svma->vm_start;
-        unsigned long sbase = saddr & PUD_MASK;
-        unsigned long s_end = sbase + PUD_SIZE;
-
-        /* Allow segments to share if only one is marked locked */
-        unsigned long vm_flags = vma->vm_flags & ~VM_LOCKED;
-        unsigned long svm_flags = svma->vm_flags & ~VM_LOCKED;
-
-        /*
-         * match the virtual addresses, permission and the alignment of the
-         * page table page.
-         */
-        if (pmd_index(addr) != pmd_index(saddr) ||
-            vm_flags != svm_flags ||
-            sbase < svma->vm_start || svma->vm_end < s_end)
-                return 0;
-
-        return saddr;
-}
-
-static int vma_shareable(struct vm_area_struct *vma, unsigned long addr)
-{
-        unsigned long base = addr & PUD_MASK;
-        unsigned long end = base + PUD_SIZE;
-
-        /*
-         * check on proper vm_flags and page table alignment
-         */
-        if (vma->vm_flags & VM_MAYSHARE &&
-            vma->vm_start <= base && end <= vma->vm_end)
-                return 1;
-        return 0;
-}
-
-/*
- * Search for a shareable pmd page for hugetlb. In any case calls pmd_alloc()
- * and returns the corresponding pte. While this is not necessary for the
- * !shared pmd case because we can allocate the pmd later as well, it makes the
- * code much cleaner. pmd allocation is essential for the shared case because
- * pud has to be populated inside the same i_mmap_mutex section - otherwise
- * racing tasks could either miss the sharing (see huge_pte_offset) or select a
- * bad pmd for sharing.
- */
-static pte_t *
-huge_pmd_share(struct mm_struct *mm, unsigned long addr, pud_t *pud)
-{
-        struct vm_area_struct *vma = find_vma(mm, addr);
-        struct address_space *mapping = vma->vm_file->f_mapping;
-        pgoff_t idx = ((addr - vma->vm_start) >> PAGE_SHIFT) +
-                        vma->vm_pgoff;
-        struct vm_area_struct *svma;
-        unsigned long saddr;
-        pte_t *spte = NULL;
-        pte_t *pte;
-
-        if (!vma_shareable(vma, addr))
-                return (pte_t *)pmd_alloc(mm, pud, addr);
-
-        mutex_lock(&mapping->i_mmap_mutex);
-        vma_interval_tree_foreach(svma, &mapping->i_mmap, idx, idx) {
-                if (svma == vma)
-                        continue;
-
-                saddr = page_table_shareable(svma, vma, addr, idx);
-                if (saddr) {
-                        spte = huge_pte_offset(svma->vm_mm, saddr);
-                        if (spte) {
-                                get_page(virt_to_page(spte));
-                                break;
-                        }
-                }
-        }
-
-        if (!spte)
-                goto out;
-
-        spin_lock(&mm->page_table_lock);
-        if (pud_none(*pud))
-                pud_populate(mm, pud, (pmd_t *)((unsigned long)spte & PAGE_MASK));
-        else
-                put_page(virt_to_page(spte));
-        spin_unlock(&mm->page_table_lock);
-out:
-        pte = (pte_t *)pmd_alloc(mm, pud, addr);
-        mutex_unlock(&mapping->i_mmap_mutex);
-        return pte;
-}
-
-/*
- * unmap huge page backed by shared pte.
- *
- * Hugetlb pte page is ref counted at the time of mapping.  If pte is shared
- * indicated by page_count > 1, unmap is achieved by clearing pud and
- * decrementing the ref count. If count == 1, the pte page is not shared.
- *
- * called with vma->vm_mm->page_table_lock held.
- *
- * returns: 1 successfully unmapped a shared pte page
- *          0 the underlying pte page is not shared, or it is the last user
- */
-int huge_pmd_unshare(struct mm_struct *mm, unsigned long *addr, pte_t *ptep)
-{
-        pgd_t *pgd = pgd_offset(mm, *addr);
-        pud_t *pud = pud_offset(pgd, *addr);
-
-        BUG_ON(page_count(virt_to_page(ptep)) == 0);
-        if (page_count(virt_to_page(ptep)) == 1)
-                return 0;
-
-        pud_clear(pud);
-        put_page(virt_to_page(ptep));
-        *addr = ALIGN(*addr, HPAGE_SIZE * PTRS_PER_PTE) - HPAGE_SIZE;
-        return 1;
-}
-
 pte_t *huge_pte_alloc(struct mm_struct *mm,
                         unsigned long addr, unsigned long sz)
 {