block: split the blk-mq case from elevator_init

There is almost no shared logic, which leads to a very confusing code
flow.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
Tested-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 858d6edff4d351c298ac0a69dd8b84642cd56157..6332940ca1187f684343d9b7d6fcc21dd9e6e005 100644 (file)
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2573,7 +2573,7 @@ struct request_queue *blk_mq_init_allocated_queue(struct blk_mq_tag_set *set,
        if (!(set->flags & BLK_MQ_F_NO_SCHED)) {
                int ret;
 
-               ret = elevator_init(q);
+               ret = elevator_init_mq(q);
                if (ret)
                        return ERR_PTR(ret);
        }

diff --git a/block/blk.h b/block/blk.h
index ab5ec2dadc7b7ff11481f543dca91423775962fc..8d23aea96ce9e73b100a8ee390344ba2b0c34bfd 100644 (file)
--- a/block/blk.h
+++ b/block/blk.h
@@ -232,6 +232,7 @@ static inline void elv_deactivate_rq(struct request_queue *q, struct request *rq
 }
 
 int elevator_init(struct request_queue *);
+int elevator_init_mq(struct request_queue *q);
 void elevator_exit(struct request_queue *, struct elevator_queue *);
 int elv_register_queue(struct request_queue *q);
 void elv_unregister_queue(struct request_queue *q);

diff --git a/block/elevator.c b/block/elevator.c
index d6480e70816eae5bfe829a5617d26b6e7a5ffe93..fa828b5bfd4b14c977b2d3cdea41ff12f1573344 100644 (file)
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -199,6 +199,11 @@ static void elevator_release(struct kobject *kobj)
        kfree(e);
 }
 
+/*
+ * Use the default elevator specified by config boot param for non-mq devices,
+ * or by config option.  Don't try to load modules as we could be running off
+ * async and request_module() isn't allowed from async.
+ */
 int elevator_init(struct request_queue *q)
 {
        struct elevator_type *e = NULL;
@@ -212,46 +217,22 @@ int elevator_init(struct request_queue *q)
        if (unlikely(q->elevator))
                goto out_unlock;
 
-       /*
-        * Use the default elevator specified by config boot param for
-        * non-mq devices, or by config option. Don't try to load modules
-        * as we could be running off async and request_module() isn't
-        * allowed from async.
-        */
-       if (!q->mq_ops && *chosen_elevator) {
+       if (*chosen_elevator) {
                e = elevator_get(q, chosen_elevator, false);
                if (!e)
                        printk(KERN_ERR "I/O scheduler %s not found\n",
                                                        chosen_elevator);
        }
 
+       if (!e)
+               e = elevator_get(q, CONFIG_DEFAULT_IOSCHED, false);
        if (!e) {
-               /*
-                * For blk-mq devices, we default to using mq-deadline,
-                * if available, for single queue devices. If deadline
-                * isn't available OR we have multiple queues, default
-                * to "none".
-                */
-               if (q->mq_ops) {
-                       if (q->nr_hw_queues == 1)
-                               e = elevator_get(q, "mq-deadline", false);
-                       if (!e)
-                               goto out_unlock;
-               } else
-                       e = elevator_get(q, CONFIG_DEFAULT_IOSCHED, false);
-
-               if (!e) {
-                       printk(KERN_ERR
-                               "Default I/O scheduler not found. " \
-                               "Using noop.\n");
-                       e = elevator_get(q, "noop", false);
-               }
+               printk(KERN_ERR
+                       "Default I/O scheduler not found. Using noop.\n");
+               e = elevator_get(q, "noop", false);
        }
 
-       if (e->uses_mq)
-               err = blk_mq_init_sched(q, e);
-       else
-               err = e->ops.sq.elevator_init_fn(q, e);
+       err = e->ops.sq.elevator_init_fn(q, e);
        if (err)
                elevator_put(e);
 out_unlock:
@@ -992,6 +973,40 @@ static int elevator_switch_mq(struct request_queue *q,
        return ret;
 }
 
+/*
+ * For blk-mq devices, we default to using mq-deadline, if available, for single
+ * queue devices.  If deadline isn't available OR we have multiple queues,
+ * default to "none".
+ */
+int elevator_init_mq(struct request_queue *q)
+{
+       struct elevator_type *e;
+       int err = 0;
+
+       if (q->nr_hw_queues != 1)
+               return 0;
+
+       /*
+        * q->sysfs_lock must be held to provide mutual exclusion between
+        * elevator_switch() and here.
+        */
+       mutex_lock(&q->sysfs_lock);
+       if (unlikely(q->elevator))
+               goto out_unlock;
+
+       e = elevator_get(q, "mq-deadline", false);
+       if (!e)
+               goto out_unlock;
+
+       err = blk_mq_init_sched(q, e);
+       if (err)
+               elevator_put(e);
+out_unlock:
+       mutex_unlock(&q->sysfs_lock);
+       return err;
+}
+
+
 /*
  * switch to new_e io scheduler. be careful not to introduce deadlocks -
  * we don't free the old io scheduler, before we have allocated what we