thp: fix zap_huge_pmd() for DAX

The original DAX code assumed that pgtable_t was a pointer, which isn't
true on all architectures.  Restructure the code to not rely on that
assumption.

[willy@linux.intel.com: further fixes integrated into this patch]
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Matthew Wilcox <willy@linux.intel.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 7510b6f..96dfd9d 100644 (file)
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1456,50 +1456,41 @@ out:
 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
                 pmd_t *pmd, unsigned long addr)
 {
+       pmd_t orig_pmd;
        spinlock_t *ptl;
-       int ret = 0;
 
-       if (__pmd_trans_huge_lock(pmd, vma, &ptl) == 1) {
-               pgtable_t pgtable;
-               pmd_t orig_pmd;
-               /*
-                * For architectures like ppc64 we look at deposited pgtable
-                * when calling pmdp_huge_get_and_clear. So do the
-                * pgtable_trans_huge_withdraw after finishing pmdp related
-                * operations.
-                */
-               orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd,
-                                                       tlb->fullmm);
-               tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
-               if (vma_is_dax(vma)) {
-                       if (is_huge_zero_pmd(orig_pmd)) {
-                               pgtable = NULL;
-                       } else {
-                               spin_unlock(ptl);
-                               return 1;
-                       }
-               } else {
-                       pgtable = pgtable_trans_huge_withdraw(tlb->mm, pmd);
-               }
-               if (is_huge_zero_pmd(orig_pmd)) {
-                       atomic_long_dec(&tlb->mm->nr_ptes);
-                       spin_unlock(ptl);
+       if (__pmd_trans_huge_lock(pmd, vma, &ptl) != 1)
+               return 0;
+       /*
+        * For architectures like ppc64 we look at deposited pgtable
+        * when calling pmdp_huge_get_and_clear. So do the
+        * pgtable_trans_huge_withdraw after finishing pmdp related
+        * operations.
+        */
+       orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd,
+                       tlb->fullmm);
+       tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
+       if (vma_is_dax(vma)) {
+               spin_unlock(ptl);
+               if (is_huge_zero_pmd(orig_pmd))
                        put_huge_zero_page();
-               } else {
-                       struct page *page = pmd_page(orig_pmd);
-                       page_remove_rmap(page);
-                       VM_BUG_ON_PAGE(page_mapcount(page) < 0, page);
-                       add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
-                       VM_BUG_ON_PAGE(!PageHead(page), page);
-                       atomic_long_dec(&tlb->mm->nr_ptes);
-                       spin_unlock(ptl);
-                       tlb_remove_page(tlb, page);
-               }
-               if (pgtable)
-                       pte_free(tlb->mm, pgtable);
-               ret = 1;
+       } else if (is_huge_zero_pmd(orig_pmd)) {
+               pte_free(tlb->mm, pgtable_trans_huge_withdraw(tlb->mm, pmd));
+               atomic_long_dec(&tlb->mm->nr_ptes);
+               spin_unlock(ptl);
+               put_huge_zero_page();
+       } else {
+               struct page *page = pmd_page(orig_pmd);
+               page_remove_rmap(page);
+               VM_BUG_ON_PAGE(page_mapcount(page) < 0, page);
+               add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
+               VM_BUG_ON_PAGE(!PageHead(page), page);
+               pte_free(tlb->mm, pgtable_trans_huge_withdraw(tlb->mm, pmd));
+               atomic_long_dec(&tlb->mm->nr_ptes);
+               spin_unlock(ptl);
+               tlb_remove_page(tlb, page);
        }
-       return ret;
+       return 1;
 }
 
 int move_huge_pmd(struct vm_area_struct *vma, struct vm_area_struct *new_vma,