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>

1 files changed, 5 insertions, 4 deletions

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 388fe01de18..72680a6715f 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;
 }
 
 /*