3 files changed, 27 insertions, 11 deletions

diff --git a/include/linux/swap.h b/include/linux/swap.h
index dca9b9999aeb..c88b36665f79 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -319,10 +319,11 @@ static inline void disable_swap_token(void)
 }
 
 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
-extern void mem_cgroup_uncharge_swapcache(struct page *page, swp_entry_t ent);
+extern void
+mem_cgroup_uncharge_swapcache(struct page *page, swp_entry_t ent, bool swapout);
 #else
 static inline void
-mem_cgroup_uncharge_swapcache(struct page *page, swp_entry_t ent)
+mem_cgroup_uncharge_swapcache(struct page *page, swp_entry_t ent, bool swapout)
 {
 }
 #endif
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 3468c38adde6..a83e0395444b 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -189,6 +189,7 @@ enum charge_type {
         MEM_CGROUP_CHARGE_TYPE_SHMEM,   /* used by page migration of shmem */
         MEM_CGROUP_CHARGE_TYPE_FORCE,   /* used by force_empty */
         MEM_CGROUP_CHARGE_TYPE_SWAPOUT, /* for accounting swapcache */
+        MEM_CGROUP_CHARGE_TYPE_DROP,    /* a page was unused swap cache */
         NR_CHARGE_TYPE,
 };
 
@@ -1493,6 +1494,7 @@ __mem_cgroup_uncharge_common(struct page *page, enum charge_type ctype)
 
         switch (ctype) {
         case MEM_CGROUP_CHARGE_TYPE_MAPPED:
+        case MEM_CGROUP_CHARGE_TYPE_DROP:
                 if (page_mapped(page))
                         goto unlock_out;
                 break;
@@ -1556,18 +1558,23 @@ void mem_cgroup_uncharge_cache_page(struct page *page)
  * called after __delete_from_swap_cache() and drop "page" account.
  * memcg information is recorded to swap_cgroup of "ent"
  */
-void mem_cgroup_uncharge_swapcache(struct page *page, swp_entry_t ent)
+void
+mem_cgroup_uncharge_swapcache(struct page *page, swp_entry_t ent, bool swapout)
 {
         struct mem_cgroup *memcg;
+        int ctype = MEM_CGROUP_CHARGE_TYPE_SWAPOUT;
+
+        if (!swapout) /* this was a swap cache but the swap is unused ! */
+                ctype = MEM_CGROUP_CHARGE_TYPE_DROP;
+
+        memcg = __mem_cgroup_uncharge_common(page, ctype);
 
-        memcg = __mem_cgroup_uncharge_common(page,
-                                        MEM_CGROUP_CHARGE_TYPE_SWAPOUT);
         /* record memcg information */
-        if (do_swap_account && memcg) {
+        if (do_swap_account && swapout && memcg) {
                 swap_cgroup_record(ent, css_id(&memcg->css));
                 mem_cgroup_get(memcg);
         }
-        if (memcg)
+        if (swapout && memcg)
                 css_put(&memcg->css);
 }
 #endif
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 28faa01cf578..d1ade1a48ee7 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -583,8 +583,9 @@ static int swap_entry_free(struct swap_info_struct *p,
                         swap_list.next = p - swap_info;
                 nr_swap_pages++;
                 p->inuse_pages--;
-                mem_cgroup_uncharge_swap(ent);
         }
+        if (!swap_count(count))
+                mem_cgroup_uncharge_swap(ent);
         return count;
 }
 
@@ -609,12 +610,19 @@ void swap_free(swp_entry_t entry)
 void swapcache_free(swp_entry_t entry, struct page *page)
 {
         struct swap_info_struct *p;
+        int ret;
 
-        if (page)
-                mem_cgroup_uncharge_swapcache(page, entry);
         p = swap_info_get(entry);
         if (p) {
-                swap_entry_free(p, entry, SWAP_CACHE);
+                ret = swap_entry_free(p, entry, SWAP_CACHE);
+                if (page) {
+                        bool swapout;
+                        if (ret)
+                                swapout = true; /* the end of swap out */
+                        else
+                                swapout = false; /* no more swap users! */
+                        mem_cgroup_uncharge_swapcache(page, entry, swapout);
+                }
                 spin_unlock(&swap_lock);
         }
         return;