[PATCH] elevator_t lifetime rules and sysfs fixes

block/elevator.c

@@ -120,15 +120,10 @@ static struct elevator_type *elevator_get(const char *name)
 	return e;
 }
 
-static int elevator_attach(request_queue_t *q, struct elevator_type *e,
-			   struct elevator_queue *eq)
+static int elevator_attach(request_queue_t *q, struct elevator_queue *eq)
 {
 	int ret = 0;
 
-	memset(eq, 0, sizeof(*eq));
-	eq->ops = &e->ops;
-	eq->elevator_type = e;
-
 	q->elevator = eq;
 
 	if (eq->ops->elevator_init_fn)
@@ -154,6 +149,32 @@ static int __init elevator_setup(char *str)
 
 __setup("elevator=", elevator_setup);
 
+static struct kobj_type elv_ktype;
+
+static elevator_t *elevator_alloc(struct elevator_type *e)
+{
+	elevator_t *eq = kmalloc(sizeof(elevator_t), GFP_KERNEL);
+	if (eq) {
+		memset(eq, 0, sizeof(*eq));
+		eq->ops = &e->ops;
+		eq->elevator_type = e;
+		kobject_init(&eq->kobj);
+		snprintf(eq->kobj.name, KOBJ_NAME_LEN, "%s", "iosched");
+		eq->kobj.ktype = &elv_ktype;
+		mutex_init(&eq->sysfs_lock);
+	} else {
+		elevator_put(e);
+	}
+	return eq;
+}
+
+static void elevator_release(struct kobject *kobj)
+{
+	elevator_t *e = container_of(kobj, elevator_t, kobj);
+	elevator_put(e->elevator_type);
+	kfree(e);
+}
+
 int elevator_init(request_queue_t *q, char *name)
 {
 	struct elevator_type *e = NULL;
@@ -176,29 +197,26 @@ int elevator_init(request_queue_t *q, char *name)
 		e = elevator_get("noop");
 	}
 
-	eq = kmalloc(sizeof(struct elevator_queue), GFP_KERNEL);
-	if (!eq) {
-		elevator_put(e);
+	eq = elevator_alloc(e);
+	if (!eq)
 		return -ENOMEM;
-	}
 
-	ret = elevator_attach(q, e, eq);
-	if (ret) {
-		kfree(eq);
-		elevator_put(e);
-	}
+	ret = elevator_attach(q, eq);
+	if (ret)
+		kobject_put(&eq->kobj);
 
 	return ret;
 }
 
 void elevator_exit(elevator_t *e)
 {
+	mutex_lock(&e->sysfs_lock);
 	if (e->ops->elevator_exit_fn)
 		e->ops->elevator_exit_fn(e);
+	e->ops = NULL;
+	mutex_unlock(&e->sysfs_lock);
 
-	elevator_put(e->elevator_type);
-	e->elevator_type = NULL;
-	kfree(e);
+	kobject_put(&e->kobj);
 }
 
 /*
@@ -627,26 +645,78 @@ void elv_completed_request(request_queue_t *q, struct request *rq)
 	}
 }
 
+#define to_elv(atr) container_of((atr), struct elv_fs_entry, attr)
+
+static ssize_t
+elv_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
+{
+	elevator_t *e = container_of(kobj, elevator_t, kobj);
+	struct elv_fs_entry *entry = to_elv(attr);
+	ssize_t error;
+
+	if (!entry->show)
+		return -EIO;
+
+	mutex_lock(&e->sysfs_lock);
+	error = e->ops ? entry->show(e, page) : -ENOENT;
+	mutex_unlock(&e->sysfs_lock);
+	return error;
+}
+
+static ssize_t
+elv_attr_store(struct kobject *kobj, struct attribute *attr,
+	       const char *page, size_t length)
+{
+	elevator_t *e = container_of(kobj, elevator_t, kobj);
+	struct elv_fs_entry *entry = to_elv(attr);
+	ssize_t error;
+
+	if (!entry->store)
+		return -EIO;
+
+	mutex_lock(&e->sysfs_lock);
+	error = e->ops ? entry->store(e, page, length) : -ENOENT;
+	mutex_unlock(&e->sysfs_lock);
+	return error;
+}
+
+static struct sysfs_ops elv_sysfs_ops = {
+	.show	= elv_attr_show,
+	.store	= elv_attr_store,
+};
+
+static struct kobj_type elv_ktype = {
+	.sysfs_ops	= &elv_sysfs_ops,
+	.release	= elevator_release,
+};
+
 int elv_register_queue(struct request_queue *q)
 {
 	elevator_t *e = q->elevator;
+	int error;
 
-	e->kobj.parent = kobject_get(&q->kobj);
-	if (!e->kobj.parent)
-		return -EBUSY;
+	e->kobj.parent = &q->kobj;
 
-	snprintf(e->kobj.name, KOBJ_NAME_LEN, "%s", "iosched");
-	e->kobj.ktype = e->elevator_type->elevator_ktype;
-
-	return kobject_register(&e->kobj);
+	error = kobject_add(&e->kobj);
+	if (!error) {
+		struct attribute **attr = e->elevator_type->elevator_attrs;
+		if (attr) {
+			while (*attr) {
+				if (sysfs_create_file(&e->kobj,*attr++))
+					break;
+			}
+		}
+		kobject_uevent(&e->kobj, KOBJ_ADD);
+	}
+	return error;
 }
 
 void elv_unregister_queue(struct request_queue *q)
 {
 	if (q) {
 		elevator_t *e = q->elevator;
-		kobject_unregister(&e->kobj);
-		kobject_put(&q->kobj);
+		kobject_uevent(&e->kobj, KOBJ_REMOVE);
+		kobject_del(&e->kobj);
 	}
 }
 
@@ -697,16 +767,16 @@ EXPORT_SYMBOL_GPL(elv_unregister);
  * need for the new one. this way we have a chance of going back to the old
  * one, if the new one fails init for some reason.
  */
-static void elevator_switch(request_queue_t *q, struct elevator_type *new_e)
+static int elevator_switch(request_queue_t *q, struct elevator_type *new_e)
 {
 	elevator_t *old_elevator, *e;
 
 	/*
 	 * Allocate new elevator
 	 */
-	e = kmalloc(sizeof(elevator_t), GFP_KERNEL);
+	e = elevator_alloc(new_e);
 	if (!e)
-		goto error;
+		return 0;
 
 	/*
 	 * Turn on BYPASS and drain all requests w/ elevator private data
@@ -737,7 +807,7 @@ static void elevator_switch(request_queue_t *q, struct elevator_type *new_e)
 	/*
 	 * attach and start new elevator
 	 */
-	if (elevator_attach(q, new_e, e))
+	if (elevator_attach(q, e))
 		goto fail;
 
 	if (elv_register_queue(q))
@@ -748,7 +818,7 @@ static void elevator_switch(request_queue_t *q, struct elevator_type *new_e)
 	 */
 	elevator_exit(old_elevator);
 	clear_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
-	return;
+	return 1;
 
 fail_register:
 	/*
@@ -761,10 +831,9 @@ fail:
 	q->elevator = old_elevator;
 	elv_register_queue(q);
 	clear_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
-	kfree(e);
-error:
-	elevator_put(new_e);
-	printk(KERN_ERR "elevator: switch to %s failed\n",new_e->elevator_name);
+	if (e)
+		kobject_put(&e->kobj);
+	return 0;
 }
 
 ssize_t elv_iosched_store(request_queue_t *q, const char *name, size_t count)
@@ -791,7 +860,8 @@ ssize_t elv_iosched_store(request_queue_t *q, const char *name, size_t count)
 		return count;
 	}
 
-	elevator_switch(q, e);
+	if (!elevator_switch(q, e))
+		printk(KERN_ERR "elevator: switch to %s failed\n",elevator_name);
 	return count;
 }