1 files changed, 31 insertions, 16 deletions

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index a353b4c6e86e..b74e7dec37dd 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -466,9 +466,10 @@ struct mem_size_stats {
 };
 
 static void smaps_account(struct mem_size_stats *mss, struct page *page,
-                unsigned long size, bool young, bool dirty)
+                bool compound, bool young, bool dirty)
 {
-        int mapcount;
+        int i, nr = compound ? HPAGE_PMD_NR : 1;
+        unsigned long size = nr * PAGE_SIZE;
 
         if (PageAnon(page))
                 mss->anonymous += size;
@@ -477,23 +478,37 @@ static void smaps_account(struct mem_size_stats *mss, struct page *page,
         /* Accumulate the size in pages that have been accessed. */
         if (young || page_is_young(page) || PageReferenced(page))
                 mss->referenced += size;
-        mapcount = page_mapcount(page);
-        if (mapcount >= 2) {
-                u64 pss_delta;
 
-                if (dirty || PageDirty(page))
-                        mss->shared_dirty += size;
-                else
-                        mss->shared_clean += size;
-                pss_delta = (u64)size << PSS_SHIFT;
-                do_div(pss_delta, mapcount);
-                mss->pss += pss_delta;
-        } else {
+        /*
+         * page_count(page) == 1 guarantees the page is mapped exactly once.
+         * If any subpage of the compound page mapped with PTE it would elevate
+         * page_count().
+         */
+        if (page_count(page) == 1) {
                 if (dirty || PageDirty(page))
                         mss->private_dirty += size;
                 else
                         mss->private_clean += size;
                 mss->pss += (u64)size << PSS_SHIFT;
+                return;
+        }
+
+        for (i = 0; i < nr; i++, page++) {
+                int mapcount = page_mapcount(page);
+
+                if (mapcount >= 2) {
+                        if (dirty || PageDirty(page))
+                                mss->shared_dirty += PAGE_SIZE;
+                        else
+                                mss->shared_clean += PAGE_SIZE;
+                        mss->pss += (PAGE_SIZE << PSS_SHIFT) / mapcount;
+                } else {
+                        if (dirty || PageDirty(page))
+                                mss->private_dirty += PAGE_SIZE;
+                        else
+                                mss->private_clean += PAGE_SIZE;
+                        mss->pss += PAGE_SIZE << PSS_SHIFT;
+                }
         }
 }
 
@@ -554,7 +569,8 @@ static void smaps_pte_entry(pte_t *pte, unsigned long addr,
 
         if (!page)
                 return;
-        smaps_account(mss, page, PAGE_SIZE, pte_young(*pte), pte_dirty(*pte));
+
+        smaps_account(mss, page, false, pte_young(*pte), pte_dirty(*pte));
 }
 
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
@@ -570,8 +586,7 @@ static void smaps_pmd_entry(pmd_t *pmd, unsigned long addr,
         if (IS_ERR_OR_NULL(page))
                 return;
         mss->anonymous_thp += HPAGE_PMD_SIZE;
-        smaps_account(mss, page, HPAGE_PMD_SIZE,
-                        pmd_young(*pmd), pmd_dirty(*pmd));
+        smaps_account(mss, page, true, pmd_young(*pmd), pmd_dirty(*pmd));
 }
 #else
 static void smaps_pmd_entry(pmd_t *pmd, unsigned long addr,