mm: migrate: do not touch page->mem_cgroup of live pages

[deliverable/linux.git] / mm / memcontrol.c

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index d06cae2de783acf462162e27f8770ff7bf60f4ad..64506b2eef3479dc190ec93f48f2852e32a7b7cf 100644 (file)
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -268,31 +268,6 @@ static inline bool mem_cgroup_is_root(struct mem_cgroup *memcg)
        return (memcg == root_mem_cgroup);
 }
 
-/*
- * We restrict the id in the range of [1, 65535], so it can fit into
- * an unsigned short.
- */
-#define MEM_CGROUP_ID_MAX      USHRT_MAX
-
-static inline unsigned short mem_cgroup_id(struct mem_cgroup *memcg)
-{
-       return memcg->css.id;
-}
-
-/*
- * A helper function to get mem_cgroup from ID. must be called under
- * rcu_read_lock().  The caller is responsible for calling
- * css_tryget_online() if the mem_cgroup is used for charging. (dropping
- * refcnt from swap can be called against removed memcg.)
- */
-static inline struct mem_cgroup *mem_cgroup_from_id(unsigned short id)
-{
-       struct cgroup_subsys_state *css;
-
-       css = css_from_id(id, &memory_cgrp_subsys);
-       return mem_cgroup_from_css(css);
-}
-
 #ifndef CONFIG_SLOB
 /*
  * This will be the memcg's index in each cache's ->memcg_params.memcg_caches.
@@ -1709,19 +1684,13 @@ cleanup:
 }
 
 /**
- * mem_cgroup_begin_page_stat - begin a page state statistics transaction
- * @page: page that is going to change accounted state
- *
- * This function must mark the beginning of an accounted page state
- * change to prevent double accounting when the page is concurrently
- * being moved to another memcg:
+ * lock_page_memcg - lock a page->mem_cgroup binding
+ * @page: the page
  *
- *   memcg = mem_cgroup_begin_page_stat(page);
- *   if (TestClearPageState(page))
- *     mem_cgroup_update_page_stat(memcg, state, -1);
- *   mem_cgroup_end_page_stat(memcg);
+ * This function protects unlocked LRU pages from being moved to
+ * another cgroup and stabilizes their page->mem_cgroup binding.
  */
-struct mem_cgroup *mem_cgroup_begin_page_stat(struct page *page)
+struct mem_cgroup *lock_page_memcg(struct page *page)
 {
        struct mem_cgroup *memcg;
        unsigned long flags;
@@ -1759,20 +1728,20 @@ again:
        /*
         * When charge migration first begins, we can have locked and
         * unlocked page stat updates happening concurrently.  Track
-        * the task who has the lock for mem_cgroup_end_page_stat().
+        * the task who has the lock for unlock_page_memcg().
         */
        memcg->move_lock_task = current;
        memcg->move_lock_flags = flags;
 
        return memcg;
 }
-EXPORT_SYMBOL(mem_cgroup_begin_page_stat);
+EXPORT_SYMBOL(lock_page_memcg);
 
 /**
- * mem_cgroup_end_page_stat - finish a page state statistics transaction
- * @memcg: the memcg that was accounted against
+ * unlock_page_memcg - unlock a page->mem_cgroup binding
+ * @memcg: the memcg returned by lock_page_memcg()
  */
-void mem_cgroup_end_page_stat(struct mem_cgroup *memcg)
+void unlock_page_memcg(struct mem_cgroup *memcg)
 {
        if (memcg && memcg->move_lock_task == current) {
                unsigned long flags = memcg->move_lock_flags;
@@ -1785,7 +1754,7 @@ void mem_cgroup_end_page_stat(struct mem_cgroup *memcg)
 
        rcu_read_unlock();
 }
-EXPORT_SYMBOL(mem_cgroup_end_page_stat);
+EXPORT_SYMBOL(unlock_page_memcg);
 
 /*
  * size of first charge trial. "32" comes from vmscan.c's magic value.
@@ -4488,7 +4457,7 @@ static int mem_cgroup_move_account(struct page *page,
        VM_BUG_ON(compound && !PageTransHuge(page));
 
        /*
-        * Prevent mem_cgroup_replace_page() from looking at
+        * Prevent mem_cgroup_migrate() from looking at
         * page->mem_cgroup of its source page while we change it.
         */
        ret = -EBUSY;
@@ -4923,9 +4892,9 @@ static void mem_cgroup_move_charge(struct mm_struct *mm)
 
        lru_add_drain_all();
        /*
-        * Signal mem_cgroup_begin_page_stat() to take the memcg's
-        * move_lock while we're moving its pages to another memcg.
-        * Then wait for already started RCU-only updates to finish.
+        * Signal lock_page_memcg() to take the memcg's move_lock
+        * while we're moving its pages to another memcg. Then wait
+        * for already started RCU-only updates to finish.
         */
        atomic_inc(&mc.from->moving_account);
        synchronize_rcu();
@@ -5517,16 +5486,17 @@ void mem_cgroup_uncharge_list(struct list_head *page_list)
 }
 
 /**
- * mem_cgroup_replace_page - migrate a charge to another page
- * @oldpage: currently charged page
- * @newpage: page to transfer the charge to
+ * mem_cgroup_migrate - charge a page's replacement
+ * @oldpage: currently circulating page
+ * @newpage: replacement page
  *
- * Migrate the charge from @oldpage to @newpage.
+ * Charge @newpage as a replacement page for @oldpage. @oldpage will
+ * be uncharged upon free.
  *
  * Both pages must be locked, @newpage->mapping must be set up.
  * Either or both pages might be on the LRU already.
  */
-void mem_cgroup_replace_page(struct page *oldpage, struct page *newpage)
+void mem_cgroup_migrate(struct page *oldpage, struct page *newpage)
 {
        struct mem_cgroup *memcg;
        unsigned int nr_pages;