1 files changed, 50 insertions, 10 deletions

diff --git a/mm/memory.c b/mm/memory.c
index 0a72f821ccdc..32e9b7aec366 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2935,6 +2935,19 @@ static inline bool transhuge_vma_suitable(struct vm_area_struct *vma,
         return true;
 }
 
+static void deposit_prealloc_pte(struct fault_env *fe)
+{
+        struct vm_area_struct *vma = fe->vma;
+
+        pgtable_trans_huge_deposit(vma->vm_mm, fe->pmd, fe->prealloc_pte);
+        /*
+         * We are going to consume the prealloc table,
+         * count that as nr_ptes.
+         */
+        atomic_long_inc(&vma->vm_mm->nr_ptes);
+        fe->prealloc_pte = 0;
+}
+
 static int do_set_pmd(struct fault_env *fe, struct page *page)
 {
         struct vm_area_struct *vma = fe->vma;
@@ -2949,6 +2962,17 @@ static int do_set_pmd(struct fault_env *fe, struct page *page)
         ret = VM_FAULT_FALLBACK;
         page = compound_head(page);
 
+        /*
+         * Archs like ppc64 need additonal space to store information
+         * related to pte entry. Use the preallocated table for that.
+         */
+        if (arch_needs_pgtable_deposit() && !fe->prealloc_pte) {
+                fe->prealloc_pte = pte_alloc_one(vma->vm_mm, fe->address);
+                if (!fe->prealloc_pte)
+                        return VM_FAULT_OOM;
+                smp_wmb(); /* See comment in __pte_alloc() */
+        }
+
         fe->ptl = pmd_lock(vma->vm_mm, fe->pmd);
         if (unlikely(!pmd_none(*fe->pmd)))
                 goto out;
@@ -2962,6 +2986,11 @@ static int do_set_pmd(struct fault_env *fe, struct page *page)
 
         add_mm_counter(vma->vm_mm, MM_FILEPAGES, HPAGE_PMD_NR);
         page_add_file_rmap(page, true);
+        /*
+         * deposit and withdraw with pmd lock held
+         */
+        if (arch_needs_pgtable_deposit())
+                deposit_prealloc_pte(fe);
 
         set_pmd_at(vma->vm_mm, haddr, fe->pmd, entry);
 
@@ -2971,6 +3000,13 @@ static int do_set_pmd(struct fault_env *fe, struct page *page)
         ret = 0;
         count_vm_event(THP_FILE_MAPPED);
 out:
+        /*
+         * If we are going to fallback to pte mapping, do a
+         * withdraw with pmd lock held.
+         */
+        if (arch_needs_pgtable_deposit() && ret == VM_FAULT_FALLBACK)
+                fe->prealloc_pte = pgtable_trans_huge_withdraw(vma->vm_mm,
+                                                               fe->pmd);
         spin_unlock(fe->ptl);
         return ret;
 }
@@ -3010,18 +3046,20 @@ int alloc_set_pte(struct fault_env *fe, struct mem_cgroup *memcg,
 
                 ret = do_set_pmd(fe, page);
                 if (ret != VM_FAULT_FALLBACK)
-                        return ret;
+                        goto fault_handled;
         }
 
         if (!fe->pte) {
                 ret = pte_alloc_one_map(fe);
                 if (ret)
-                        return ret;
+                        goto fault_handled;
         }
 
         /* Re-check under ptl */
-        if (unlikely(!pte_none(*fe->pte)))
-                return VM_FAULT_NOPAGE;
+        if (unlikely(!pte_none(*fe->pte))) {
+                ret = VM_FAULT_NOPAGE;
+                goto fault_handled;
+        }
 
         flush_icache_page(vma, page);
         entry = mk_pte(page, vma->vm_page_prot);
@@ -3041,8 +3079,15 @@ int alloc_set_pte(struct fault_env *fe, struct mem_cgroup *memcg,
 
         /* no need to invalidate: a not-present page won't be cached */
         update_mmu_cache(vma, fe->address, fe->pte);
+        ret = 0;
 
-        return 0;
+fault_handled:
+        /* preallocated pagetable is unused: free it */
+        if (fe->prealloc_pte) {
+                pte_free(fe->vma->vm_mm, fe->prealloc_pte);
+                fe->prealloc_pte = 0;
+        }
+        return ret;
 }
 
 static unsigned long fault_around_bytes __read_mostly =
@@ -3141,11 +3186,6 @@ static int do_fault_around(struct fault_env *fe, pgoff_t start_pgoff)
 
         fe->vma->vm_ops->map_pages(fe, start_pgoff, end_pgoff);
 
-        /* preallocated pagetable is unused: free it */
-        if (fe->prealloc_pte) {
-                pte_free(fe->vma->vm_mm, fe->prealloc_pte);
-                fe->prealloc_pte = 0;
-        }
         /* Huge page is mapped? Page fault is solved */
         if (pmd_trans_huge(*fe->pmd)) {
                 ret = VM_FAULT_NOPAGE;