mm, thp: drop do_huge_pmd_wp_zero_page_fallback()

I've realized that there's no need for do_huge_pmd_wp_zero_page_fallback().
We can just split zero page with split_huge_page_pmd() and return
VM_FAULT_FALLBACK.  handle_pte_fault() will handle write-protection
fault for us.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 77 deletions

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 1546655a2d78..6ac89e9f82ef 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -941,81 +941,6 @@ unlock:
         spin_unlock(ptl);
 }
 
-static int do_huge_pmd_wp_zero_page_fallback(struct mm_struct *mm,
-                struct vm_area_struct *vma, unsigned long address,
-                pmd_t *pmd, pmd_t orig_pmd, unsigned long haddr)
-{
-        spinlock_t *ptl;
-        pgtable_t pgtable;
-        pmd_t _pmd;
-        struct page *page;
-        int i, ret = 0;
-        unsigned long mmun_start;       /* For mmu_notifiers */
-        unsigned long mmun_end;         /* For mmu_notifiers */
-
-        page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, address);
-        if (!page) {
-                ret |= VM_FAULT_OOM;
-                goto out;
-        }
-
-        if (mem_cgroup_newpage_charge(page, mm, GFP_KERNEL)) {
-                put_page(page);
-                ret |= VM_FAULT_OOM;
-                goto out;
-        }
-
-        clear_user_highpage(page, address);
-        __SetPageUptodate(page);
-
-        mmun_start = haddr;
-        mmun_end   = haddr + HPAGE_PMD_SIZE;
-        mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
-
-        ptl = pmd_lock(mm, pmd);
-        if (unlikely(!pmd_same(*pmd, orig_pmd)))
-                goto out_free_page;
-
-        pmdp_clear_flush(vma, haddr, pmd);
-        /* leave pmd empty until pte is filled */
-
-        pgtable = pgtable_trans_huge_withdraw(mm, pmd);
-        pmd_populate(mm, &_pmd, pgtable);
-
-        for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
-                pte_t *pte, entry;
-                if (haddr == (address & PAGE_MASK)) {
-                        entry = mk_pte(page, vma->vm_page_prot);
-                        entry = maybe_mkwrite(pte_mkdirty(entry), vma);
-                        page_add_new_anon_rmap(page, vma, haddr);
-                } else {
-                        entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
-                        entry = pte_mkspecial(entry);
-                }
-                pte = pte_offset_map(&_pmd, haddr);
-                VM_BUG_ON(!pte_none(*pte));
-                set_pte_at(mm, haddr, pte, entry);
-                pte_unmap(pte);
-        }
-        smp_wmb(); /* make pte visible before pmd */
-        pmd_populate(mm, pmd, pgtable);
-        spin_unlock(ptl);
-        put_huge_zero_page();
-        inc_mm_counter(mm, MM_ANONPAGES);
-
-        mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
-
-        ret |= VM_FAULT_WRITE;
-out:
-        return ret;
-out_free_page:
-        spin_unlock(ptl);
-        mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
-        mem_cgroup_uncharge_page(page);
-        put_page(page);
-        goto out;
-}
-
 static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm,
                                         struct vm_area_struct *vma,
                                         unsigned long address,
@@ -1161,8 +1086,8 @@ alloc:
 
         if (unlikely(!new_page)) {
                 if (!page) {
-                        ret = do_huge_pmd_wp_zero_page_fallback(mm, vma,
-                                        address, pmd, orig_pmd, haddr);
+                        split_huge_page_pmd(vma, address, pmd);
+                        ret |= VM_FAULT_FALLBACK;
                 } else {
                         ret = do_huge_pmd_wp_page_fallback(mm, vma, address,
                                         pmd, orig_pmd, page, haddr);