block, cfq: move icq cache management to block core

Let elevators set ->icq_size and ->icq_align in elevator_type and
elv_register() and elv_unregister() respectively create and destroy
kmem_cache for icq.

* elv_register() now can return failure.  All callers updated.

* icq caches are automatically named "ELVNAME_io_cq".

* cfq_slab_setup/kill() are collapsed into cfq_init/exit().

* While at it, minor indentation change for iosched_cfq.elevator_name
  for consistency.

This will help moving icq management to block core.  This doesn't
introduce any functional change.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 35 insertions, 2 deletions

diff --git a/block/elevator.c b/block/elevator.c
index c5c6214829cb..cca049fb45c8 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -886,15 +886,36 @@ void elv_unregister_queue(struct request_queue *q)
 }
 EXPORT_SYMBOL(elv_unregister_queue);
 
-void elv_register(struct elevator_type *e)
+int elv_register(struct elevator_type *e)
 {
         char *def = "";
 
+        /* create icq_cache if requested */
+        if (e->icq_size) {
+                if (WARN_ON(e->icq_size < sizeof(struct io_cq)) ||
+                    WARN_ON(e->icq_align < __alignof__(struct io_cq)))
+                        return -EINVAL;
+
+                snprintf(e->icq_cache_name, sizeof(e->icq_cache_name),
+                         "%s_io_cq", e->elevator_name);
+                e->icq_cache = kmem_cache_create(e->icq_cache_name, e->icq_size,
+                                                 e->icq_align, 0, NULL);
+                if (!e->icq_cache)
+                        return -ENOMEM;
+        }
+
+        /* register, don't allow duplicate names */
         spin_lock(&elv_list_lock);
-        BUG_ON(elevator_find(e->elevator_name));
+        if (elevator_find(e->elevator_name)) {
+                spin_unlock(&elv_list_lock);
+                if (e->icq_cache)
+                        kmem_cache_destroy(e->icq_cache);
+                return -EBUSY;
+        }
         list_add_tail(&e->list, &elv_list);
         spin_unlock(&elv_list_lock);
 
+        /* print pretty message */
         if (!strcmp(e->elevator_name, chosen_elevator) ||
                         (!*chosen_elevator &&
                          !strcmp(e->elevator_name, CONFIG_DEFAULT_IOSCHED)))
@@ -902,14 +923,26 @@ void elv_register(struct elevator_type *e)
 
         printk(KERN_INFO "io scheduler %s registered%s\n", e->elevator_name,
                                                                 def);
+        return 0;
 }
 EXPORT_SYMBOL_GPL(elv_register);
 
 void elv_unregister(struct elevator_type *e)
 {
+        /* unregister */
         spin_lock(&elv_list_lock);
         list_del_init(&e->list);
         spin_unlock(&elv_list_lock);
+
+        /*
+         * Destroy icq_cache if it exists.  icq's are RCU managed.  Make
+         * sure all RCU operations are complete before proceeding.
+         */
+        if (e->icq_cache) {
+                rcu_barrier();
+                kmem_cache_destroy(e->icq_cache);
+                e->icq_cache = NULL;
+        }
 }
 EXPORT_SYMBOL_GPL(elv_unregister);