[PATCH] elevator_t lifetime rules and sysfs fixes

block/as-iosched.c

@@ -1709,11 +1709,6 @@ static int as_init_queue(request_queue_t *q, elevator_t *e)
 /*
  * sysfs parts below
  */
-struct as_fs_entry {
-	struct attribute attr;
-	ssize_t (*show)(struct as_data *, char *);
-	ssize_t (*store)(struct as_data *, const char *, size_t);
-};
 
 static ssize_t
 as_var_show(unsigned int var, char *page)
@@ -1730,8 +1725,9 @@ as_var_store(unsigned long *var, const char *page, size_t count)
 	return count;
 }
 
-static ssize_t as_est_show(struct as_data *ad, char *page)
+static ssize_t as_est_show(elevator_t *e, char *page)
 {
+	struct as_data *ad = e->elevator_data;
 	int pos = 0;
 
 	pos += sprintf(page+pos, "%lu %% exit probability\n",
@@ -1747,8 +1743,9 @@ static ssize_t as_est_show(struct as_data *ad, char *page)
 }
 
 #define SHOW_FUNCTION(__FUNC, __VAR)				\
-static ssize_t __FUNC(struct as_data *ad, char *page)		\
+static ssize_t __FUNC(elevator_t *e, char *page)		\
 {								\
+	struct as_data *ad = e->elevator_data;			\
 	return as_var_show(jiffies_to_msecs((__VAR)), (page));	\
 }
 SHOW_FUNCTION(as_readexpire_show, ad->fifo_expire[REQ_SYNC]);
@@ -1759,9 +1756,10 @@ SHOW_FUNCTION(as_write_batchexpire_show, ad->batch_expire[REQ_ASYNC]);
 #undef SHOW_FUNCTION
 
 #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX)				\
-static ssize_t __FUNC(struct as_data *ad, const char *page, size_t count)	\
+static ssize_t __FUNC(elevator_t *e, const char *page, size_t count)	\
 {									\
-	int ret = as_var_store(__PTR, (page), count);		\
+	struct as_data *ad = e->elevator_data;				\
+	int ret = as_var_store(__PTR, (page), count);			\
 	if (*(__PTR) < (MIN))						\
 		*(__PTR) = (MIN);					\
 	else if (*(__PTR) > (MAX))					\
@@ -1778,37 +1776,37 @@ STORE_FUNCTION(as_write_batchexpire_store,
 			&ad->batch_expire[REQ_ASYNC], 0, INT_MAX);
 #undef STORE_FUNCTION
 
-static struct as_fs_entry as_est_entry = {
+static struct elv_fs_entry as_est_entry = {
 	.attr = {.name = "est_time", .mode = S_IRUGO },
 	.show = as_est_show,
 };
-static struct as_fs_entry as_readexpire_entry = {
+static struct elv_fs_entry as_readexpire_entry = {
 	.attr = {.name = "read_expire", .mode = S_IRUGO | S_IWUSR },
 	.show = as_readexpire_show,
 	.store = as_readexpire_store,
 };
-static struct as_fs_entry as_writeexpire_entry = {
+static struct elv_fs_entry as_writeexpire_entry = {
 	.attr = {.name = "write_expire", .mode = S_IRUGO | S_IWUSR },
 	.show = as_writeexpire_show,
 	.store = as_writeexpire_store,
 };
-static struct as_fs_entry as_anticexpire_entry = {
+static struct elv_fs_entry as_anticexpire_entry = {
 	.attr = {.name = "antic_expire", .mode = S_IRUGO | S_IWUSR },
 	.show = as_anticexpire_show,
 	.store = as_anticexpire_store,
 };
-static struct as_fs_entry as_read_batchexpire_entry = {
+static struct elv_fs_entry as_read_batchexpire_entry = {
 	.attr = {.name = "read_batch_expire", .mode = S_IRUGO | S_IWUSR },
 	.show = as_read_batchexpire_show,
 	.store = as_read_batchexpire_store,
 };
-static struct as_fs_entry as_write_batchexpire_entry = {
+static struct elv_fs_entry as_write_batchexpire_entry = {
 	.attr = {.name = "write_batch_expire", .mode = S_IRUGO | S_IWUSR },
 	.show = as_write_batchexpire_show,
 	.store = as_write_batchexpire_store,
 };
 
-static struct attribute *default_attrs[] = {
+static struct attribute *as_attrs[] = {
 	&as_est_entry.attr,
 	&as_readexpire_entry.attr,
 	&as_writeexpire_entry.attr,
@@ -1818,43 +1816,6 @@ static struct attribute *default_attrs[] = {
 	NULL,
 };
 
-#define to_as(atr) container_of((atr), struct as_fs_entry, attr)
-
-static ssize_t
-as_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
-{
-	elevator_t *e = container_of(kobj, elevator_t, kobj);
-	struct as_fs_entry *entry = to_as(attr);
-
-	if (!entry->show)
-		return -EIO;
-
-	return entry->show(e->elevator_data, page);
-}
-
-static ssize_t
-as_attr_store(struct kobject *kobj, struct attribute *attr,
-		    const char *page, size_t length)
-{
-	elevator_t *e = container_of(kobj, elevator_t, kobj);
-	struct as_fs_entry *entry = to_as(attr);
-
-	if (!entry->store)
-		return -EIO;
-
-	return entry->store(e->elevator_data, page, length);
-}
-
-static struct sysfs_ops as_sysfs_ops = {
-	.show	= as_attr_show,
-	.store	= as_attr_store,
-};
-
-static struct kobj_type as_ktype = {
-	.sysfs_ops	= &as_sysfs_ops,
-	.default_attrs	= default_attrs,
-};
-
 static struct elevator_type iosched_as = {
 	.ops = {
 		.elevator_merge_fn = 		as_merge,
@@ -1876,7 +1837,7 @@ static struct elevator_type iosched_as = {
 		.trim =				as_trim,
 	},
 
-	.elevator_ktype = &as_ktype,
+	.elevator_attrs = as_attrs,
 	.elevator_name = "anticipatory",
 	.elevator_owner = THIS_MODULE,
 };

block/cfq-iosched.c

@@ -2275,11 +2275,6 @@ fail:
 /*
  * sysfs parts below -->
  */
-struct cfq_fs_entry {
-	struct attribute attr;
-	ssize_t (*show)(struct cfq_data *, char *);
-	ssize_t (*store)(struct cfq_data *, const char *, size_t);
-};
 
 static ssize_t
 cfq_var_show(unsigned int var, char *page)
@@ -2297,8 +2292,9 @@ cfq_var_store(unsigned int *var, const char *page, size_t count)
 }
 
 #define SHOW_FUNCTION(__FUNC, __VAR, __CONV)				\
-static ssize_t __FUNC(struct cfq_data *cfqd, char *page)		\
+static ssize_t __FUNC(elevator_t *e, char *page)			\
 {									\
+	struct cfq_data *cfqd = e->elevator_data;			\
 	unsigned int __data = __VAR;					\
 	if (__CONV)							\
 		__data = jiffies_to_msecs(__data);			\
@@ -2318,8 +2314,9 @@ SHOW_FUNCTION(cfq_max_depth_show, cfqd->cfq_max_depth, 0);
 #undef SHOW_FUNCTION
 
 #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV)			\
-static ssize_t __FUNC(struct cfq_data *cfqd, const char *page, size_t count)	\
+static ssize_t __FUNC(elevator_t *e, const char *page, size_t count)	\
 {									\
+	struct cfq_data *cfqd = e->elevator_data;			\
 	unsigned int __data;						\
 	int ret = cfq_var_store(&__data, (page), count);		\
 	if (__data < (MIN))						\
@@ -2345,63 +2342,63 @@ STORE_FUNCTION(cfq_slice_async_rq_store, &cfqd->cfq_slice_async_rq, 1, UINT_MAX,
 STORE_FUNCTION(cfq_max_depth_store, &cfqd->cfq_max_depth, 1, UINT_MAX, 0);
 #undef STORE_FUNCTION
 
-static struct cfq_fs_entry cfq_quantum_entry = {
+static struct elv_fs_entry cfq_quantum_entry = {
 	.attr = {.name = "quantum", .mode = S_IRUGO | S_IWUSR },
 	.show = cfq_quantum_show,
 	.store = cfq_quantum_store,
 };
-static struct cfq_fs_entry cfq_queued_entry = {
+static struct elv_fs_entry cfq_queued_entry = {
 	.attr = {.name = "queued", .mode = S_IRUGO | S_IWUSR },
 	.show = cfq_queued_show,
 	.store = cfq_queued_store,
 };
-static struct cfq_fs_entry cfq_fifo_expire_sync_entry = {
+static struct elv_fs_entry cfq_fifo_expire_sync_entry = {
 	.attr = {.name = "fifo_expire_sync", .mode = S_IRUGO | S_IWUSR },
 	.show = cfq_fifo_expire_sync_show,
 	.store = cfq_fifo_expire_sync_store,
 };
-static struct cfq_fs_entry cfq_fifo_expire_async_entry = {
+static struct elv_fs_entry cfq_fifo_expire_async_entry = {
 	.attr = {.name = "fifo_expire_async", .mode = S_IRUGO | S_IWUSR },
 	.show = cfq_fifo_expire_async_show,
 	.store = cfq_fifo_expire_async_store,
 };
-static struct cfq_fs_entry cfq_back_max_entry = {
+static struct elv_fs_entry cfq_back_max_entry = {
 	.attr = {.name = "back_seek_max", .mode = S_IRUGO | S_IWUSR },
 	.show = cfq_back_max_show,
 	.store = cfq_back_max_store,
 };
-static struct cfq_fs_entry cfq_back_penalty_entry = {
+static struct elv_fs_entry cfq_back_penalty_entry = {
 	.attr = {.name = "back_seek_penalty", .mode = S_IRUGO | S_IWUSR },
 	.show = cfq_back_penalty_show,
 	.store = cfq_back_penalty_store,
 };
-static struct cfq_fs_entry cfq_slice_sync_entry = {
+static struct elv_fs_entry cfq_slice_sync_entry = {
 	.attr = {.name = "slice_sync", .mode = S_IRUGO | S_IWUSR },
 	.show = cfq_slice_sync_show,
 	.store = cfq_slice_sync_store,
 };
-static struct cfq_fs_entry cfq_slice_async_entry = {
+static struct elv_fs_entry cfq_slice_async_entry = {
 	.attr = {.name = "slice_async", .mode = S_IRUGO | S_IWUSR },
 	.show = cfq_slice_async_show,
 	.store = cfq_slice_async_store,
 };
-static struct cfq_fs_entry cfq_slice_async_rq_entry = {
+static struct elv_fs_entry cfq_slice_async_rq_entry = {
 	.attr = {.name = "slice_async_rq", .mode = S_IRUGO | S_IWUSR },
 	.show = cfq_slice_async_rq_show,
 	.store = cfq_slice_async_rq_store,
 };
-static struct cfq_fs_entry cfq_slice_idle_entry = {
+static struct elv_fs_entry cfq_slice_idle_entry = {
 	.attr = {.name = "slice_idle", .mode = S_IRUGO | S_IWUSR },
 	.show = cfq_slice_idle_show,
 	.store = cfq_slice_idle_store,
 };
-static struct cfq_fs_entry cfq_max_depth_entry = {
+static struct elv_fs_entry cfq_max_depth_entry = {
 	.attr = {.name = "max_depth", .mode = S_IRUGO | S_IWUSR },
 	.show = cfq_max_depth_show,
 	.store = cfq_max_depth_store,
 };
 
-static struct attribute *default_attrs[] = {
+static struct attribute *cfq_attrs[] = {
 	&cfq_quantum_entry.attr,
 	&cfq_queued_entry.attr,
 	&cfq_fifo_expire_sync_entry.attr,
@@ -2416,43 +2413,6 @@ static struct attribute *default_attrs[] = {
 	NULL,
 };
 
-#define to_cfq(atr) container_of((atr), struct cfq_fs_entry, attr)
-
-static ssize_t
-cfq_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
-{
-	elevator_t *e = container_of(kobj, elevator_t, kobj);
-	struct cfq_fs_entry *entry = to_cfq(attr);
-
-	if (!entry->show)
-		return -EIO;
-
-	return entry->show(e->elevator_data, page);
-}
-
-static ssize_t
-cfq_attr_store(struct kobject *kobj, struct attribute *attr,
-	       const char *page, size_t length)
-{
-	elevator_t *e = container_of(kobj, elevator_t, kobj);
-	struct cfq_fs_entry *entry = to_cfq(attr);
-
-	if (!entry->store)
-		return -EIO;
-
-	return entry->store(e->elevator_data, page, length);
-}
-
-static struct sysfs_ops cfq_sysfs_ops = {
-	.show	= cfq_attr_show,
-	.store	= cfq_attr_store,
-};
-
-static struct kobj_type cfq_ktype = {
-	.sysfs_ops	= &cfq_sysfs_ops,
-	.default_attrs	= default_attrs,
-};
-
 static struct elevator_type iosched_cfq = {
 	.ops = {
 		.elevator_merge_fn = 		cfq_merge,
@@ -2473,7 +2433,7 @@ static struct elevator_type iosched_cfq = {
 		.elevator_exit_fn =		cfq_exit_queue,
 		.trim =				cfq_trim,
 	},
-	.elevator_ktype =	&cfq_ktype,
+	.elevator_attrs =	cfq_attrs,
 	.elevator_name =	"cfq",
 	.elevator_owner =	THIS_MODULE,
 };

block/deadline-iosched.c

@@ -694,11 +694,6 @@ deadline_set_request(request_queue_t *q, struct request *rq, struct bio *bio,
 /*
  * sysfs parts below
  */
-struct deadline_fs_entry {
-	struct attribute attr;
-	ssize_t (*show)(struct deadline_data *, char *);
-	ssize_t (*store)(struct deadline_data *, const char *, size_t);
-};
 
 static ssize_t
 deadline_var_show(int var, char *page)
@@ -716,9 +711,10 @@ deadline_var_store(int *var, const char *page, size_t count)
 }
 
 #define SHOW_FUNCTION(__FUNC, __VAR, __CONV)				\
-static ssize_t __FUNC(struct deadline_data *dd, char *page)		\
+static ssize_t __FUNC(elevator_t *e, char *page)			\
 {									\
-	int __data = __VAR;					\
+	struct deadline_data *dd = e->elevator_data;			\
+	int __data = __VAR;						\
 	if (__CONV)							\
 		__data = jiffies_to_msecs(__data);			\
 	return deadline_var_show(__data, (page));			\
@@ -731,8 +727,9 @@ SHOW_FUNCTION(deadline_fifobatch_show, dd->fifo_batch, 0);
 #undef SHOW_FUNCTION
 
 #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV)			\
-static ssize_t __FUNC(struct deadline_data *dd, const char *page, size_t count)	\
+static ssize_t __FUNC(elevator_t *e, const char *page, size_t count)	\
 {									\
+	struct deadline_data *dd = e->elevator_data;			\
 	int __data;							\
 	int ret = deadline_var_store(&__data, (page), count);		\
 	if (__data < (MIN))						\
@@ -752,33 +749,33 @@ STORE_FUNCTION(deadline_frontmerges_store, &dd->front_merges, 0, 1, 0);
 STORE_FUNCTION(deadline_fifobatch_store, &dd->fifo_batch, 0, INT_MAX, 0);
 #undef STORE_FUNCTION
 
-static struct deadline_fs_entry deadline_readexpire_entry = {
+static struct elv_fs_entry deadline_readexpire_entry = {
 	.attr = {.name = "read_expire", .mode = S_IRUGO | S_IWUSR },
 	.show = deadline_readexpire_show,
 	.store = deadline_readexpire_store,
 };
-static struct deadline_fs_entry deadline_writeexpire_entry = {
+static struct elv_fs_entry deadline_writeexpire_entry = {
 	.attr = {.name = "write_expire", .mode = S_IRUGO | S_IWUSR },
 	.show = deadline_writeexpire_show,
 	.store = deadline_writeexpire_store,
 };
-static struct deadline_fs_entry deadline_writesstarved_entry = {
+static struct elv_fs_entry deadline_writesstarved_entry = {
 	.attr = {.name = "writes_starved", .mode = S_IRUGO | S_IWUSR },
 	.show = deadline_writesstarved_show,
 	.store = deadline_writesstarved_store,
 };
-static struct deadline_fs_entry deadline_frontmerges_entry = {
+static struct elv_fs_entry deadline_frontmerges_entry = {
 	.attr = {.name = "front_merges", .mode = S_IRUGO | S_IWUSR },
 	.show = deadline_frontmerges_show,
 	.store = deadline_frontmerges_store,
 };
-static struct deadline_fs_entry deadline_fifobatch_entry = {
+static struct elv_fs_entry deadline_fifobatch_entry = {
 	.attr = {.name = "fifo_batch", .mode = S_IRUGO | S_IWUSR },
 	.show = deadline_fifobatch_show,
 	.store = deadline_fifobatch_store,
 };
 
-static struct attribute *default_attrs[] = {
+static struct attribute *deadline_attrs[] = {
 	&deadline_readexpire_entry.attr,
 	&deadline_writeexpire_entry.attr,
 	&deadline_writesstarved_entry.attr,
@@ -787,43 +784,6 @@ static struct attribute *default_attrs[] = {
 	NULL,
 };
 
-#define to_deadline(atr) container_of((atr), struct deadline_fs_entry, attr)
-
-static ssize_t
-deadline_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
-{
-	elevator_t *e = container_of(kobj, elevator_t, kobj);
-	struct deadline_fs_entry *entry = to_deadline(attr);
-
-	if (!entry->show)
-		return -EIO;
-
-	return entry->show(e->elevator_data, page);
-}
-
-static ssize_t
-deadline_attr_store(struct kobject *kobj, struct attribute *attr,
-		    const char *page, size_t length)
-{
-	elevator_t *e = container_of(kobj, elevator_t, kobj);
-	struct deadline_fs_entry *entry = to_deadline(attr);
-
-	if (!entry->store)
-		return -EIO;
-
-	return entry->store(e->elevator_data, page, length);
-}
-
-static struct sysfs_ops deadline_sysfs_ops = {
-	.show	= deadline_attr_show,
-	.store	= deadline_attr_store,
-};
-
-static struct kobj_type deadline_ktype = {
-	.sysfs_ops	= &deadline_sysfs_ops,
-	.default_attrs	= default_attrs,
-};
-
 static struct elevator_type iosched_deadline = {
 	.ops = {
 		.elevator_merge_fn = 		deadline_merge,
@@ -840,7 +800,7 @@ static struct elevator_type iosched_deadline = {
 		.elevator_exit_fn =		deadline_exit_queue,
 	},
 
-	.elevator_ktype = &deadline_ktype,
+	.elevator_attrs = deadline_attrs,
 	.elevator_name = "deadline",
 	.elevator_owner = THIS_MODULE,
 };

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)
 	}
 }
 
-int elv_register_queue(struct request_queue *q)
+#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 = q->elevator;
+	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;
+}
 
-	e->kobj.parent = kobject_get(&q->kobj);
-	if (!e->kobj.parent)
-		return -EBUSY;
+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;
 
-	snprintf(e->kobj.name, KOBJ_NAME_LEN, "%s", "iosched");
-	e->kobj.ktype = e->elevator_type->elevator_ktype;
+	if (!entry->store)
+		return -EIO;
 
-	return kobject_register(&e->kobj);
+	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 = &q->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;
 }
 

include/linux/elevator.h

@@ -61,7 +61,7 @@ struct elevator_type
 	struct list_head list;
 	struct elevator_ops ops;
 	struct elevator_type *elevator_type;
-	struct kobj_type *elevator_ktype;
+	struct attribute **elevator_attrs;
 	char elevator_name[ELV_NAME_MAX];
 	struct module *elevator_owner;
 };
@@ -75,6 +75,7 @@ struct elevator_queue
 	void *elevator_data;
 	struct kobject kobj;
 	struct elevator_type *elevator_type;
+	struct mutex sysfs_lock;
 };
 
 /*
@@ -141,6 +142,12 @@ enum {
 	ELV_MQUEUE_MUST,
 };
 
+struct elv_fs_entry {
+	struct attribute attr;
+	ssize_t (*show)(elevator_t *, char *);
+	ssize_t (*store)(elevator_t *, const char *, size_t);
+};
+
 #define rq_end_sector(rq)	((rq)->sector + (rq)->nr_sectors)
 
 #endif