---
  fs/proc/task_mmu.c | 30 ++++++++++++++++++++++--------
  1 file changed, 22 insertions(+), 8 deletions(-)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index dbda449..76e623a 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c

@@ -723,9 +723,21 @@ static int smaps_hugetlb_range(pte_t *pte, unsigned long hmask,
  	.pte_hole		= smaps_pte_hole,
  };
  
+/*
+ * Gather mem stats from @vma with the indicated beginning
+ * address @start, and keep them in @mss.
+ *
+ * Use vm_start of @vma as the beginning address if @start is 0.
+ */
  static void smap_gather_stats(struct vm_area_struct *vma,
-			     struct mem_size_stats *mss)
+		struct mem_size_stats *mss, unsigned long start)
  {
+	const struct mm_walk_ops *ops = &smaps_walk_ops;
+
+	/* Invalid start */
+	if (start >= vma->vm_end)
+		return;
+
  #ifdef CONFIG_SHMEM
  	/* In case of smaps_rollup, reset the value from previous vma */
  	mss->check_shmem_swap = false;

@@ -742,18 +754,20 @@ static void smap_gather_stats(struct vm_area_struct *vma,
  		 */
  		unsigned long shmem_swapped = shmem_swap_usage(vma);
  
-		if (!shmem_swapped || (vma->vm_flags & VM_SHARED) ||
-					!(vma->vm_flags & VM_WRITE)) {
+		if (!start && (!shmem_swapped || (vma->vm_flags & VM_SHARED) ||
+					!(vma->vm_flags & VM_WRITE))) {
  			mss->swap += shmem_swapped;
  		} else {
  			mss->check_shmem_swap = true;
-			walk_page_vma(vma, &smaps_shmem_walk_ops, mss);
-			return;
+			ops = &smaps_shmem_walk_ops;
  		}
  	}
  #endif
  	/* mmap_lock is held in m_start */
-	walk_page_vma(vma, &smaps_walk_ops, mss);
+	if (!start)
+		walk_page_vma(vma, ops, mss);
+	else
+		walk_page_range(vma->vm_mm, start, vma->vm_end, ops, mss);
  }
  
  #define SEQ_PUT_DEC(str, val) \

@@ -805,7 +819,7 @@ static int show_smap(struct seq_file *m, void *v)
  
  	memset(&mss, 0, sizeof(mss));
  
-	smap_gather_stats(vma, &mss);
+	smap_gather_stats(vma, &mss, 0);
  
  	show_map_vma(m, vma);
  

@@ -854,7 +868,7 @@ static int show_smaps_rollup(struct seq_file *m, void *v)
  	hold_task_mempolicy(priv);
  
  	for (vma = priv->mm->mmap; vma; vma = vma->vm_next) {
-		smap_gather_stats(vma, &mss);
+		smap_gather_stats(vma, &mss, 0);
  		last_vma_end = vma->vm_end;
  	}