1 files changed, 55 insertions, 30 deletions

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 2efa8ea07ff..00bb8a64d02 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -61,7 +61,14 @@ struct mem_cgroup *root_mem_cgroup __read_mostly;
 #ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP
 /* Turned on only when memory cgroup is enabled && really_do_swap_account = 1 */
 int do_swap_account __read_mostly;
-static int really_do_swap_account __initdata = 1; /* for remember boot option*/
+
+/* for remember boot option*/
+#ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP_ENABLED
+static int really_do_swap_account __initdata = 1;
+#else
+static int really_do_swap_account __initdata = 0;
+#endif
+
 #else
 #define do_swap_account         (0)
 #endif
@@ -278,13 +285,14 @@ enum move_type {
 
 /* "mc" and its members are protected by cgroup_mutex */
 static struct move_charge_struct {
-        spinlock_t        lock; /* for from, to, moving_task */
+        spinlock_t        lock; /* for from, to */
         struct mem_cgroup *from;
         struct mem_cgroup *to;
         unsigned long precharge;
         unsigned long moved_charge;
         unsigned long moved_swap;
         struct task_struct *moving_task;        /* a task moving charges */
+        struct mm_struct *mm;
         wait_queue_head_t waitq;                /* a waitq for other context */
 } mc = {
         .lock = __SPIN_LOCK_UNLOCKED(mc.lock),
@@ -1917,19 +1925,18 @@ again:
 
                 rcu_read_lock();
                 p = rcu_dereference(mm->owner);
-                VM_BUG_ON(!p);
                 /*
-                 * because we don't have task_lock(), "p" can exit while
-                 * we're here. In that case, "mem" can point to root
-                 * cgroup but never be NULL. (and task_struct itself is freed
-                 * by RCU, cgroup itself is RCU safe.) Then, we have small
-                 * risk here to get wrong cgroup. But such kind of mis-account
-                 * by race always happens because we don't have cgroup_mutex().
-                 * It's overkill and we allow that small race, here.
+                 * Because we don't have task_lock(), "p" can exit.
+                 * In that case, "mem" can point to root or p can be NULL with
+                 * race with swapoff. Then, we have small risk of mis-accouning.
+                 * But such kind of mis-account by race always happens because
+                 * we don't have cgroup_mutex(). It's overkill and we allo that
+                 * small race, here.
+                 * (*) swapoff at el will charge against mm-struct not against
+                 * task-struct. So, mm->owner can be NULL.
                  */
                 mem = mem_cgroup_from_task(p);
-                VM_BUG_ON(!mem);
-                if (mem_cgroup_is_root(mem)) {
+                if (!mem || mem_cgroup_is_root(mem)) {
                         rcu_read_unlock();
                         goto done;
                 }
@@ -2152,7 +2159,7 @@ static void __mem_cgroup_move_account(struct page_cgroup *pc,
 {
         VM_BUG_ON(from == to);
         VM_BUG_ON(PageLRU(pc->page));
-        VM_BUG_ON(!PageCgroupLocked(pc));
+        VM_BUG_ON(!page_is_cgroup_locked(pc));
         VM_BUG_ON(!PageCgroupUsed(pc));
         VM_BUG_ON(pc->mem_cgroup != from);
 
@@ -4631,7 +4638,7 @@ static unsigned long mem_cgroup_count_precharge(struct mm_struct *mm)
         unsigned long precharge;
         struct vm_area_struct *vma;
 
-        down_read(&mm->mmap_sem);
+        /* We've already held the mmap_sem */
         for (vma = mm->mmap; vma; vma = vma->vm_next) {
                 struct mm_walk mem_cgroup_count_precharge_walk = {
                         .pmd_entry = mem_cgroup_count_precharge_pte_range,
@@ -4643,7 +4650,6 @@ static unsigned long mem_cgroup_count_precharge(struct mm_struct *mm)
                 walk_page_range(vma->vm_start, vma->vm_end,
                                         &mem_cgroup_count_precharge_walk);
         }
-        up_read(&mm->mmap_sem);
 
         precharge = mc.precharge;
         mc.precharge = 0;
@@ -4694,11 +4700,16 @@ static void mem_cgroup_clear_mc(void)
 
                 mc.moved_swap = 0;
         }
+        if (mc.mm) {
+                up_read(&mc.mm->mmap_sem);
+                mmput(mc.mm);
+        }
         spin_lock(&mc.lock);
         mc.from = NULL;
         mc.to = NULL;
-        mc.moving_task = NULL;
         spin_unlock(&mc.lock);
+        mc.moving_task = NULL;
+        mc.mm = NULL;
         mem_cgroup_end_move(from);
         memcg_oom_recover(from);
         memcg_oom_recover(to);
@@ -4724,12 +4735,21 @@ static int mem_cgroup_can_attach(struct cgroup_subsys *ss,
                         return 0;
                 /* We move charges only when we move a owner of the mm */
                 if (mm->owner == p) {
+                        /*
+                         * We do all the move charge works under one mmap_sem to
+                         * avoid deadlock with down_write(&mmap_sem)
+                         * -> try_charge() -> if (mc.moving_task) -> sleep.
+                         */
+                        down_read(&mm->mmap_sem);
+
                         VM_BUG_ON(mc.from);
                         VM_BUG_ON(mc.to);
                         VM_BUG_ON(mc.precharge);
                         VM_BUG_ON(mc.moved_charge);
                         VM_BUG_ON(mc.moved_swap);
                         VM_BUG_ON(mc.moving_task);
+                        VM_BUG_ON(mc.mm);
+
                         mem_cgroup_start_move(from);
                         spin_lock(&mc.lock);
                         mc.from = from;
@@ -4737,14 +4757,16 @@ static int mem_cgroup_can_attach(struct cgroup_subsys *ss,
                         mc.precharge = 0;
                         mc.moved_charge = 0;
                         mc.moved_swap = 0;
-                        mc.moving_task = current;
                         spin_unlock(&mc.lock);
+                        mc.moving_task = current;
+                        mc.mm = mm;
 
                         ret = mem_cgroup_precharge_mc(mm);
                         if (ret)
                                 mem_cgroup_clear_mc();
-                }
-                mmput(mm);
+                        /* We call up_read() and mmput() in clear_mc(). */
+                } else
+                        mmput(mm);
         }
         return ret;
 }
@@ -4832,7 +4854,7 @@ static void mem_cgroup_move_charge(struct mm_struct *mm)
         struct vm_area_struct *vma;
 
         lru_add_drain_all();
-        down_read(&mm->mmap_sem);
+        /* We've already held the mmap_sem */
         for (vma = mm->mmap; vma; vma = vma->vm_next) {
                 int ret;
                 struct mm_walk mem_cgroup_move_charge_walk = {
@@ -4851,7 +4873,6 @@ static void mem_cgroup_move_charge(struct mm_struct *mm)
                          */
                         break;
         }
-        up_read(&mm->mmap_sem);
 }
 
 static void mem_cgroup_move_task(struct cgroup_subsys *ss,
@@ -4860,17 +4881,11 @@ static void mem_cgroup_move_task(struct cgroup_subsys *ss,
                                 struct task_struct *p,
                                 bool threadgroup)
 {
-        struct mm_struct *mm;
-
-        if (!mc.to)
+        if (!mc.mm)
                 /* no need to move charge */
                 return;
 
-        mm = get_task_mm(p);
-        if (mm) {
-                mem_cgroup_move_charge(mm);
-                mmput(mm);
-        }
+        mem_cgroup_move_charge(mc.mm);
         mem_cgroup_clear_mc();
 }
 #else   /* !CONFIG_MMU */
@@ -4911,10 +4926,20 @@ struct cgroup_subsys mem_cgroup_subsys = {
 };
 
 #ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP
+static int __init enable_swap_account(char *s)
+{
+        /* consider enabled if no parameter or 1 is given */
+        if (!s || !strcmp(s, "1"))
+                really_do_swap_account = 1;
+        else if (!strcmp(s, "0"))
+                really_do_swap_account = 0;
+        return 1;
+}
+__setup("swapaccount", enable_swap_account);
 
 static int __init disable_swap_account(char *s)
 {
-        really_do_swap_account = 0;
+        enable_swap_account("0");
         return 1;
 }
 __setup("noswapaccount", disable_swap_account);