memcg: cleanup preparation for page table walk

pagewalk.c can handle vma in itself, so we don't have to pass vma via
walk->private.  And both of mem_cgroup_count_precharge() and
mem_cgroup_move_charge() do for each vma loop themselves, but now it's
done in pagewalk.c, so let's clean up them.

Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/memcontrol.c

@@ -4839,7 +4839,7 @@ static int mem_cgroup_count_precharge_pte_range(pmd_t *pmd,
 					unsigned long addr, unsigned long end,
 					struct mm_walk *walk)
 {
-	struct vm_area_struct *vma = walk->private;
+	struct vm_area_struct *vma = walk->vma;
 	pte_t *pte;
 	spinlock_t *ptl;
 
@@ -4865,20 +4865,13 @@ static int mem_cgroup_count_precharge_pte_range(pmd_t *pmd,
 static unsigned long mem_cgroup_count_precharge(struct mm_struct *mm)
 {
 	unsigned long precharge;
-	struct vm_area_struct *vma;
 
+	struct mm_walk mem_cgroup_count_precharge_walk = {
+		.pmd_entry = mem_cgroup_count_precharge_pte_range,
+		.mm = mm,
+	};
 	down_read(&mm->mmap_sem);
-	for (vma = mm->mmap; vma; vma = vma->vm_next) {
-		struct mm_walk mem_cgroup_count_precharge_walk = {
-			.pmd_entry = mem_cgroup_count_precharge_pte_range,
-			.mm = mm,
-			.private = vma,
-		};
-		if (is_vm_hugetlb_page(vma))
-			continue;
-		walk_page_range(vma->vm_start, vma->vm_end,
-					&mem_cgroup_count_precharge_walk);
-	}
+	walk_page_range(0, ~0UL, &mem_cgroup_count_precharge_walk);
 	up_read(&mm->mmap_sem);
 
 	precharge = mc.precharge;
@@ -5011,7 +5004,7 @@ static int mem_cgroup_move_charge_pte_range(pmd_t *pmd,
 				struct mm_walk *walk)
 {
 	int ret = 0;
-	struct vm_area_struct *vma = walk->private;
+	struct vm_area_struct *vma = walk->vma;
 	pte_t *pte;
 	spinlock_t *ptl;
 	enum mc_target_type target_type;
@@ -5107,7 +5100,10 @@ static int mem_cgroup_move_charge_pte_range(pmd_t *pmd,
 
 static void mem_cgroup_move_charge(struct mm_struct *mm)
 {
-	struct vm_area_struct *vma;
+	struct mm_walk mem_cgroup_move_charge_walk = {
+		.pmd_entry = mem_cgroup_move_charge_pte_range,
+		.mm = mm,
+	};
 
 	lru_add_drain_all();
 	/*
@@ -5130,24 +5126,11 @@ static void mem_cgroup_move_charge(struct mm_struct *mm)
 		cond_resched();
 		goto retry;
 	}
-	for (vma = mm->mmap; vma; vma = vma->vm_next) {
-		int ret;
-		struct mm_walk mem_cgroup_move_charge_walk = {
-			.pmd_entry = mem_cgroup_move_charge_pte_range,
-			.mm = mm,
-			.private = vma,
-		};
-		if (is_vm_hugetlb_page(vma))
-			continue;
-		ret = walk_page_range(vma->vm_start, vma->vm_end,
-						&mem_cgroup_move_charge_walk);
-		if (ret)
-			/*
-			 * means we have consumed all precharges and failed in
-			 * doing additional charge. Just abandon here.
-			 */
-			break;
-	}
+	/*
+	 * When we have consumed all precharges and failed in doing
+	 * additional charge, the page walk just aborts.
+	 */
+	walk_page_range(0, ~0UL, &mem_cgroup_move_charge_walk);
 	up_read(&mm->mmap_sem);
 	atomic_dec(&mc.from->moving_account);
 }