[PATCH] fix try_module_get race in elevator_find (2824bc93) · Commits · 戴 / test

drivers/block/elevator.c

+14 −10

Original line number	Diff line number	Diff line
		@@ -97,7 +97,6 @@ static struct elevator_type elevator_find(const char name)
		struct elevator_type *e = NULL;
		struct list_head *entry;

		spin_lock_irq(&elv_list_lock);
		list_for_each(entry, &elv_list) {
		struct elevator_type *__e;

		@@ -108,7 +107,6 @@ static struct elevator_type elevator_find(const char name)
		break;
		}
		}
		spin_unlock_irq(&elv_list_lock);

		return e;
		}
		@@ -120,12 +118,15 @@ static void elevator_put(struct elevator_type *e)

		static struct elevator_type elevator_get(const char name)
		{
		struct elevator_type *e = elevator_find(name);
		struct elevator_type *e;

		if (!e)
		return NULL;
		if (!try_module_get(e->elevator_owner))
		return NULL;
		spin_lock_irq(&elv_list_lock);

		e = elevator_find(name);
		if (e && !try_module_get(e->elevator_owner))
		e = NULL;

		spin_unlock_irq(&elv_list_lock);

		return e;
		}
		@@ -153,11 +154,15 @@ static char chosen_elevator[16];

		static void elevator_setup_default(void)
		{
		struct elevator_type *e;

		/*
		* check if default is set and exists
		*/
		if (chosen_elevator[0] && elevator_find(chosen_elevator))
		if (chosen_elevator[0] && (e = elevator_get(chosen_elevator))) {
		elevator_put(e);
		return;
		}

		#if defined(CONFIG_IOSCHED_AS)
		strcpy(chosen_elevator, "anticipatory");
		@@ -555,10 +560,9 @@ void elv_unregister_queue(struct request_queue *q)

		int elv_register(struct elevator_type *e)
		{
		spin_lock_irq(&elv_list_lock);
		if (elevator_find(e->elevator_name))
		BUG();

		spin_lock_irq(&elv_list_lock);
		list_add_tail(&e->list, &elv_list);
		spin_unlock_irq(&elv_list_lock);