mm/THP: deposit the transpare huge pgtable before set_pmd

Architectures like powerpc use the deposited pgtable to store hash index
values.  We need to make the deposted pgtable is visible to other cpus
before we are ready to take a hash fault.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: David Gibson <david@gibson.dropbear.id.au>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

mm/huge_memory.c

@@ -729,8 +729,8 @@ static int __do_huge_pmd_anonymous_page(struct mm_struct *mm,
 		pmd_t entry;
 		entry = mk_huge_pmd(page, vma);
 		page_add_new_anon_rmap(page, vma, haddr);
-		set_pmd_at(mm, haddr, pmd, entry);
 		pgtable_trans_huge_deposit(mm, pmd, pgtable);
+		set_pmd_at(mm, haddr, pmd, entry);
 		add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
 		mm->nr_ptes++;
 		spin_unlock(&mm->page_table_lock);
@@ -771,8 +771,8 @@ static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
 	entry = mk_pmd(zero_page, vma->vm_page_prot);
 	entry = pmd_wrprotect(entry);
 	entry = pmd_mkhuge(entry);
-	set_pmd_at(mm, haddr, pmd, entry);
 	pgtable_trans_huge_deposit(mm, pmd, pgtable);
+	set_pmd_at(mm, haddr, pmd, entry);
 	mm->nr_ptes++;
 	return true;
 }
@@ -916,8 +916,8 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
 
 	pmdp_set_wrprotect(src_mm, addr, src_pmd);
 	pmd = pmd_mkold(pmd_wrprotect(pmd));
-	set_pmd_at(dst_mm, addr, dst_pmd, pmd);
 	pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
+	set_pmd_at(dst_mm, addr, dst_pmd, pmd);
 	dst_mm->nr_ptes++;
 
 	ret = 0;
@@ -2367,9 +2367,9 @@ static void collapse_huge_page(struct mm_struct *mm,
 	spin_lock(&mm->page_table_lock);
 	BUG_ON(!pmd_none(*pmd));
 	page_add_new_anon_rmap(new_page, vma, address);
+	pgtable_trans_huge_deposit(mm, pmd, pgtable);
 	set_pmd_at(mm, address, pmd, _pmd);
 	update_mmu_cache_pmd(vma, address, pmd);
-	pgtable_trans_huge_deposit(mm, pmd, pgtable);
 	spin_unlock(&mm->page_table_lock);
 
 	*hpage = NULL;