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>

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 1546655a2d78afe4dc1c954b5e0ccff77ba3437f..6ac89e9f82efe0936df17931acc60503a9405c3b 100644 (file)
--- 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);