1 files changed, 148 insertions, 100 deletions

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 0576e9e..991860e 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1047,6 +1047,49 @@ static unsigned int get_swappiness(struct mem_cgroup *memcg)
 	return swappiness;
 }
 
+/* A routine for testing mem is not under move_account */
+
+static bool mem_cgroup_under_move(struct mem_cgroup *mem)
+{
+	struct mem_cgroup *from = mc.from;
+	struct mem_cgroup *to = mc.to;
+	bool ret = false;
+
+	if (from == mem || to == mem)
+		return true;
+
+	if (!from || !to || !mem->use_hierarchy)
+		return false;
+
+	rcu_read_lock();
+	if (css_tryget(&from->css)) {
+		ret = css_is_ancestor(&from->css, &mem->css);
+		css_put(&from->css);
+	}
+	if (!ret && css_tryget(&to->css)) {
+		ret = css_is_ancestor(&to->css,	&mem->css);
+		css_put(&to->css);
+	}
+	rcu_read_unlock();
+	return ret;
+}
+
+static bool mem_cgroup_wait_acct_move(struct mem_cgroup *mem)
+{
+	if (mc.moving_task && current != mc.moving_task) {
+		if (mem_cgroup_under_move(mem)) {
+			DEFINE_WAIT(wait);
+			prepare_to_wait(&mc.waitq, &wait, TASK_INTERRUPTIBLE);
+			/* moving charge context might have finished. */
+			if (mc.moving_task)
+				schedule();
+			finish_wait(&mc.waitq, &wait);
+			return true;
+		}
+	}
+	return false;
+}
+
 static int mem_cgroup_count_children_cb(struct mem_cgroup *mem, void *data)
 {
 	int *val = data;
@@ -1575,16 +1618,83 @@ static int __cpuinit memcg_stock_cpu_callback(struct notifier_block *nb,
 	return NOTIFY_OK;
 }
 
+
+/* See __mem_cgroup_try_charge() for details */
+enum {
+	CHARGE_OK,		/* success */
+	CHARGE_RETRY,		/* need to retry but retry is not bad */
+	CHARGE_NOMEM,		/* we can't do more. return -ENOMEM */
+	CHARGE_WOULDBLOCK,	/* GFP_WAIT wasn't set and no enough res. */
+	CHARGE_OOM_DIE,		/* the current is killed because of OOM */
+};
+
+static int __mem_cgroup_do_charge(struct mem_cgroup *mem, gfp_t gfp_mask,
+				int csize, bool oom_check)
+{
+	struct mem_cgroup *mem_over_limit;
+	struct res_counter *fail_res;
+	unsigned long flags = 0;
+	int ret;
+
+	ret = res_counter_charge(&mem->res, csize, &fail_res);
+
+	if (likely(!ret)) {
+		if (!do_swap_account)
+			return CHARGE_OK;
+		ret = res_counter_charge(&mem->memsw, csize, &fail_res);
+		if (likely(!ret))
+			return CHARGE_OK;
+
+		mem_over_limit = mem_cgroup_from_res_counter(fail_res, memsw);
+		flags |= MEM_CGROUP_RECLAIM_NOSWAP;
+	} else
+		mem_over_limit = mem_cgroup_from_res_counter(fail_res, res);
+
+	if (csize > PAGE_SIZE) /* change csize and retry */
+		return CHARGE_RETRY;
+
+	if (!(gfp_mask & __GFP_WAIT))
+		return CHARGE_WOULDBLOCK;
+
+	ret = mem_cgroup_hierarchical_reclaim(mem_over_limit, NULL,
+					gfp_mask, flags);
+	/*
+	 * try_to_free_mem_cgroup_pages() might not give us a full
+	 * picture of reclaim. Some pages are reclaimed and might be
+	 * moved to swap cache or just unmapped from the cgroup.
+	 * Check the limit again to see if the reclaim reduced the
+	 * current usage of the cgroup before giving up
+	 */
+	if (ret || mem_cgroup_check_under_limit(mem_over_limit))
+		return CHARGE_RETRY;
+
+	/*
+	 * At task move, charge accounts can be doubly counted. So, it's
+	 * better to wait until the end of task_move if something is going on.
+	 */
+	if (mem_cgroup_wait_acct_move(mem_over_limit))
+		return CHARGE_RETRY;
+
+	/* If we don't need to call oom-killer at el, return immediately */
+	if (!oom_check)
+		return CHARGE_NOMEM;
+	/* check OOM */
+	if (!mem_cgroup_handle_oom(mem_over_limit, gfp_mask))
+		return CHARGE_OOM_DIE;
+
+	return CHARGE_RETRY;
+}
+
 /*
  * Unlike exported interface, "oom" parameter is added. if oom==true,
  * oom-killer can be invoked.
  */
 static int __mem_cgroup_try_charge(struct mm_struct *mm,
-			gfp_t gfp_mask, struct mem_cgroup **memcg, bool oom)
+		gfp_t gfp_mask, struct mem_cgroup **memcg, bool oom)
 {
-	struct mem_cgroup *mem, *mem_over_limit;
-	int nr_retries = MEM_CGROUP_RECLAIM_RETRIES;
-	struct res_counter *fail_res;
+	int nr_oom_retries = MEM_CGROUP_RECLAIM_RETRIES;
+	struct mem_cgroup *mem = NULL;
+	int ret;
 	int csize = CHARGE_SIZE;
 
 	/*
@@ -1602,120 +1712,56 @@ static int __mem_cgroup_try_charge(struct mm_struct *mm,
 	 * thread group leader migrates. It's possible that mm is not
 	 * set, if so charge the init_mm (happens for pagecache usage).
 	 */
-	mem = *memcg;
-	if (likely(!mem)) {
+	if (*memcg) {
+		mem = *memcg;
+		css_get(&mem->css);
+	} else {
 		mem = try_get_mem_cgroup_from_mm(mm);
+		if (unlikely(!mem))
+			return 0;
 		*memcg = mem;
-	} else {
-		css_get(&mem->css);
 	}
-	if (unlikely(!mem))
-		return 0;
 
 	VM_BUG_ON(css_is_removed(&mem->css));
 	if (mem_cgroup_is_root(mem))
 		goto done;
 
-	while (1) {
-		int ret = 0;
-		unsigned long flags = 0;
+	do {
+		bool oom_check;
 
 		if (consume_stock(mem))
-			goto done;
-
-		ret = res_counter_charge(&mem->res, csize, &fail_res);
-		if (likely(!ret)) {
-			if (!do_swap_account)
-				break;
-			ret = res_counter_charge(&mem->memsw, csize, &fail_res);
-			if (likely(!ret))
-				break;
-			/* mem+swap counter fails */
-			res_counter_uncharge(&mem->res, csize);
-			flags |= MEM_CGROUP_RECLAIM_NOSWAP;
-			mem_over_limit = mem_cgroup_from_res_counter(fail_res,
-									memsw);
-		} else
-			/* mem counter fails */
-			mem_over_limit = mem_cgroup_from_res_counter(fail_res,
-									res);
+			goto done; /* don't need to fill stock */
+		/* If killed, bypass charge */
+		if (fatal_signal_pending(current))
+			goto bypass;
 
-		/* reduce request size and retry */
-		if (csize > PAGE_SIZE) {
-			csize = PAGE_SIZE;
-			continue;
+		oom_check = false;
+		if (oom && !nr_oom_retries) {
+			oom_check = true;
+			nr_oom_retries = MEM_CGROUP_RECLAIM_RETRIES;
 		}
-		if (!(gfp_mask & __GFP_WAIT))
-			goto nomem;
 
-		ret = mem_cgroup_hierarchical_reclaim(mem_over_limit, NULL,
-						gfp_mask, flags);
-		if (ret)
-			continue;
+		ret = __mem_cgroup_do_charge(mem, gfp_mask, csize, oom_check);
 
-		/*
-		 * try_to_free_mem_cgroup_pages() might not give us a full
-		 * picture of reclaim. Some pages are reclaimed and might be
-		 * moved to swap cache or just unmapped from the cgroup.
-		 * Check the limit again to see if the reclaim reduced the
-		 * current usage of the cgroup before giving up
-		 *
-		 */
-		if (mem_cgroup_check_under_limit(mem_over_limit))
-			continue;
-
-		/* try to avoid oom while someone is moving charge */
-		if (mc.moving_task && current != mc.moving_task) {
-			struct mem_cgroup *from, *to;
-			bool do_continue = false;
-			/*
-			 * There is a small race that "from" or "to" can be
-			 * freed by rmdir, so we use css_tryget().
-			 */
-			from = mc.from;
-			to = mc.to;
-			if (from && css_tryget(&from->css)) {
-				if (mem_over_limit->use_hierarchy)
-					do_continue = css_is_ancestor(
-							&from->css,
-							&mem_over_limit->css);
-				else
-					do_continue = (from == mem_over_limit);
-				css_put(&from->css);
-			}
-			if (!do_continue && to && css_tryget(&to->css)) {
-				if (mem_over_limit->use_hierarchy)
-					do_continue = css_is_ancestor(
-							&to->css,
-							&mem_over_limit->css);
-				else
-					do_continue = (to == mem_over_limit);
-				css_put(&to->css);
-			}
-			if (do_continue) {
-				DEFINE_WAIT(wait);
-				prepare_to_wait(&mc.waitq, &wait,
-							TASK_INTERRUPTIBLE);
-				/* moving charge context might have finished. */
-				if (mc.moving_task)
-					schedule();
-				finish_wait(&mc.waitq, &wait);
-				continue;
-			}
-		}
-
-		if (!nr_retries--) {
+		switch (ret) {
+		case CHARGE_OK:
+			break;
+		case CHARGE_RETRY: /* not in OOM situation but retry */
+			csize = PAGE_SIZE;
+			break;
+		case CHARGE_WOULDBLOCK: /* !__GFP_WAIT */
+			goto nomem;
+		case CHARGE_NOMEM: /* OOM routine works */
 			if (!oom)
 				goto nomem;
-			if (mem_cgroup_handle_oom(mem_over_limit, gfp_mask)) {
-				nr_retries = MEM_CGROUP_RECLAIM_RETRIES;
-				continue;
-			}
-			/* When we reach here, current task is dying .*/
-			css_put(&mem->css);
+			/* If oom, we never return -ENOMEM */
+			nr_oom_retries--;
+			break;
+		case CHARGE_OOM_DIE: /* Killed by OOM Killer */
 			goto bypass;
 		}
-	}
+	} while (ret != CHARGE_OK);
+
 	if (csize > PAGE_SIZE)
 		refill_stock(mem, csize - PAGE_SIZE);
 done:
@@ -1724,6 +1770,8 @@ nomem:
 	css_put(&mem->css);
 	return -ENOMEM;
 bypass:
+	if (mem)
+		css_put(&mem->css);
 	*memcg = NULL;
 	return 0;
 }