4 files changed, 18 insertions, 53 deletions

diff --git a/Documentation/cgroups/memory.txt b/Documentation/cgroups/memory.txt
index e479007f1a75..6a066a270fc5 100644
--- a/Documentation/cgroups/memory.txt
+++ b/Documentation/cgroups/memory.txt
@@ -184,12 +184,14 @@ behind this approach is that a cgroup that aggressively uses a shared
 page will eventually get charged for it (once it is uncharged from
 the cgroup that brought it in -- this will happen on memory pressure).
 
+But see section 8.2: when moving a task to another cgroup, its pages may
+be recharged to the new cgroup, if move_charge_at_immigrate has been chosen.
+
 Exception: If CONFIG_CGROUP_CGROUP_MEM_RES_CTLR_SWAP is not used.
 When you do swapoff and make swapped-out pages of shmem(tmpfs) to
 be backed into memory in force, charges for pages are accounted against the
 caller of swapoff rather than the users of shmem.
 
-
 2.4 Swap Extension (CONFIG_CGROUP_MEM_RES_CTLR_SWAP)
 
 Swap Extension allows you to record charge for swap. A swapped-in page is
@@ -615,8 +617,7 @@ memory cgroup.
   bit | what type of charges would be moved ?
  -----+------------------------------------------------------------------------
    0  | A charge of an anonymous page(or swap of it) used by the target task.
-      | Those pages and swaps must be used only by the target task. You must
-      | enable Swap Extension(see 2.4) to enable move of swap charges.
+      | You must enable Swap Extension(see 2.4) to enable move of swap charges.
  -----+------------------------------------------------------------------------
    1  | A charge of file pages(normal file, tmpfs file(e.g. ipc shared memory)
       | and swaps of tmpfs file) mmapped by the target task. Unlike the case of
@@ -629,8 +630,6 @@ memory cgroup.
 
 8.3 TODO
 
-- Implement madvise(2) to let users decide the vma to be moved or not to be
-  moved.
 - All of moving charge operations are done under cgroup_mutex. It's not good
   behavior to hold the mutex too long, so we may need some trick.
 
diff --git a/include/linux/swap.h b/include/linux/swap.h
index d965c4bfab3a..49c0fa9ef5cf 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -359,7 +359,6 @@ struct backing_dev_info;
 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
 extern void
 mem_cgroup_uncharge_swapcache(struct page *page, swp_entry_t ent, bool swapout);
-extern int mem_cgroup_count_swap_user(swp_entry_t ent, struct page **pagep);
 #else
 static inline void
 mem_cgroup_uncharge_swapcache(struct page *page, swp_entry_t ent, bool swapout)
@@ -470,14 +469,6 @@ mem_cgroup_uncharge_swapcache(struct page *page, swp_entry_t ent)
 {
 }
 
-#ifdef CONFIG_CGROUP_MEM_RES_CTLR
-static inline int
-mem_cgroup_count_swap_user(swp_entry_t ent, struct page **pagep)
-{
-        return 0;
-}
-#endif
-
 #endif /* CONFIG_SWAP */
 #endif /* __KERNEL__*/
 #endif /* _LINUX_SWAP_H */
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index d7ce417cae7c..e7db70f3d2d6 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -5154,7 +5154,7 @@ static struct page *mc_handle_present_pte(struct vm_area_struct *vma,
                 return NULL;
         if (PageAnon(page)) {
                 /* we don't move shared anon */
-                if (!move_anon() || page_mapcount(page) > 2)
+                if (!move_anon())
                         return NULL;
         } else if (!move_file())
                 /* we ignore mapcount for file pages */
@@ -5165,26 +5165,32 @@ static struct page *mc_handle_present_pte(struct vm_area_struct *vma,
         return page;
 }
 
+#ifdef CONFIG_SWAP
 static struct page *mc_handle_swap_pte(struct vm_area_struct *vma,
                         unsigned long addr, pte_t ptent, swp_entry_t *entry)
 {
-        int usage_count;
         struct page *page = NULL;
         swp_entry_t ent = pte_to_swp_entry(ptent);
 
         if (!move_anon() || non_swap_entry(ent))
                 return NULL;
-        usage_count = mem_cgroup_count_swap_user(ent, &page);
-        if (usage_count > 1) { /* we don't move shared anon */
-                if (page)
-                        put_page(page);
-                return NULL;
-        }
+        /*
+         * Because lookup_swap_cache() updates some statistics counter,
+         * we call find_get_page() with swapper_space directly.
+         */
+        page = find_get_page(&swapper_space, ent.val);
         if (do_swap_account)
                 entry->val = ent.val;
 
         return page;
 }
+#else
+static struct page *mc_handle_swap_pte(struct vm_area_struct *vma,
+                        unsigned long addr, pte_t ptent, swp_entry_t *entry)
+{
+        return NULL;
+}
+#endif
 
 static struct page *mc_handle_file_pte(struct vm_area_struct *vma,
                         unsigned long addr, pte_t ptent, swp_entry_t *entry)
diff --git a/mm/swapfile.c b/mm/swapfile.c
index b0c86e92f42c..457b10baef59 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -717,37 +717,6 @@ int free_swap_and_cache(swp_entry_t entry)
         return p != NULL;
 }
 
-#ifdef CONFIG_CGROUP_MEM_RES_CTLR
-/**
- * mem_cgroup_count_swap_user - count the user of a swap entry
- * @ent: the swap entry to be checked
- * @pagep: the pointer for the swap cache page of the entry to be stored
- *
- * Returns the number of the user of the swap entry. The number is valid only
- * for swaps of anonymous pages.
- * If the entry is found on swap cache, the page is stored to pagep with
- * refcount of it being incremented.
- */
-int mem_cgroup_count_swap_user(swp_entry_t ent, struct page **pagep)
-{
-        struct page *page;
-        struct swap_info_struct *p;
-        int count = 0;
-
-        page = find_get_page(&swapper_space, ent.val);
-        if (page)
-                count += page_mapcount(page);
-        p = swap_info_get(ent);
-        if (p) {
-                count += swap_count(p->swap_map[swp_offset(ent)]);
-                spin_unlock(&swap_lock);
-        }
-
-        *pagep = page;
-        return count;
-}
-#endif
-
 #ifdef CONFIG_HIBERNATION
 /*
  * Find the swap type that corresponds to given device (if any).