elevator: make elevator_init_fn() return 0/-errno

elevator_ops->elevator_init_fn() has a weird return value.  It returns
a void * which the caller should assign to q->elevator->elevator_data
and %NULL return denotes init failure.

Update such that it returns integer 0/-errno and sets elevator_data
directly as necessary.

This makes the interface more conventional and eases further cleanup.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

4 files changed, 17 insertions, 20 deletions

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 388fe01de18e..72680a6715fc 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -3656,7 +3656,7 @@ static void cfq_exit_queue(struct elevator_queue *e)
         kfree(cfqd);
 }
 
-static void *cfq_init_queue(struct request_queue *q)
+static int cfq_init_queue(struct request_queue *q)
 {
         struct cfq_data *cfqd;
         int i, j;
@@ -3665,7 +3665,7 @@ static void *cfq_init_queue(struct request_queue *q)
 
         cfqd = kmalloc_node(sizeof(*cfqd), GFP_KERNEL | __GFP_ZERO, q->node);
         if (!cfqd)
-                return NULL;
+                return -ENOMEM;
 
         /* Init root service tree */
         cfqd->grp_service_tree = CFQ_RB_ROOT;
@@ -3692,7 +3692,7 @@ static void *cfq_init_queue(struct request_queue *q)
         if (blkio_alloc_blkg_stats(&cfqg->blkg)) {
                 kfree(cfqg);
                 kfree(cfqd);
-                return NULL;
+                return -ENOMEM;
         }
 
         rcu_read_lock();
@@ -3723,6 +3723,7 @@ static void *cfq_init_queue(struct request_queue *q)
         cfq_link_cfqq_cfqg(&cfqd->oom_cfqq, &cfqd->root_group);
 
         cfqd->queue = q;
+        q->elevator->elevator_data = cfqd;
 
         init_timer(&cfqd->idle_slice_timer);
         cfqd->idle_slice_timer.function = cfq_idle_slice_timer;
@@ -3747,7 +3748,7 @@ static void *cfq_init_queue(struct request_queue *q)
          * second, in order to have larger depth for async operations.
          */
         cfqd->last_delayed_sync = jiffies - HZ;
-        return cfqd;
+        return 0;
 }
 
 /*
diff --git a/block/deadline-iosched.c b/block/deadline-iosched.c
index 7bf12d793fcd..599b12e5380f 100644
--- a/block/deadline-iosched.c
+++ b/block/deadline-iosched.c
@@ -337,13 +337,13 @@ static void deadline_exit_queue(struct elevator_queue *e)
 /*
  * initialize elevator private data (deadline_data).
  */
-static void *deadline_init_queue(struct request_queue *q)
+static int deadline_init_queue(struct request_queue *q)
 {
         struct deadline_data *dd;
 
         dd = kmalloc_node(sizeof(*dd), GFP_KERNEL | __GFP_ZERO, q->node);
         if (!dd)
-                return NULL;
+                return -ENOMEM;
 
         INIT_LIST_HEAD(&dd->fifo_list[READ]);
         INIT_LIST_HEAD(&dd->fifo_list[WRITE]);
@@ -354,7 +354,9 @@ static void *deadline_init_queue(struct request_queue *q)
         dd->writes_starved = writes_starved;
         dd->front_merges = 1;
         dd->fifo_batch = fifo_batch;
-        return dd;
+
+        q->elevator->elevator_data = dd;
+        return 0;
 }
 
 /*
diff --git a/block/elevator.c b/block/elevator.c
index f8c08e1bff2b..f81c061dad15 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -121,14 +121,6 @@ static struct elevator_type *elevator_get(const char *name)
         return e;
 }
 
-static int elevator_init_queue(struct request_queue *q)
-{
-        q->elevator->elevator_data = q->elevator->type->ops.elevator_init_fn(q);
-        if (q->elevator->elevator_data)
-                return 0;
-        return -ENOMEM;
-}
-
 static char chosen_elevator[ELV_NAME_MAX];
 
 static int __init elevator_setup(char *str)
@@ -224,7 +216,7 @@ int elevator_init(struct request_queue *q, char *name)
         if (!q->elevator)
                 return -ENOMEM;
 
-        err = elevator_init_queue(q);
+        err = e->ops.elevator_init_fn(q);
         if (err) {
                 kobject_put(&q->elevator->kobj);
                 return err;
@@ -927,7 +919,7 @@ static int elevator_switch(struct request_queue *q, struct elevator_type *new_e)
         if (!q->elevator)
                 goto fail_init;
 
-        err = elevator_init_queue(q);
+        err = new_e->ops.elevator_init_fn(q);
         if (err) {
                 kobject_put(&q->elevator->kobj);
                 goto fail_init;
diff --git a/block/noop-iosched.c b/block/noop-iosched.c
index 413a0b1d788c..5d1bf70e33d5 100644
--- a/block/noop-iosched.c
+++ b/block/noop-iosched.c
@@ -59,15 +59,17 @@ noop_latter_request(struct request_queue *q, struct request *rq)
         return list_entry(rq->queuelist.next, struct request, queuelist);
 }
 
-static void *noop_init_queue(struct request_queue *q)
+static int noop_init_queue(struct request_queue *q)
 {
         struct noop_data *nd;
 
         nd = kmalloc_node(sizeof(*nd), GFP_KERNEL, q->node);
         if (!nd)
-                return NULL;
+                return -ENOMEM;
+
         INIT_LIST_HEAD(&nd->queue);
-        return nd;
+        q->elevator->elevator_data = nd;
+        return 0;
 }
 
 static void noop_exit_queue(struct elevator_queue *e)