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, 10 insertions, 1 deletions

diff --git a/include/linux/elevator.h b/include/linux/elevator.h
index 04958ef53e62..d3d3e28cbfd4 100644
--- a/include/linux/elevator.h
+++ b/include/linux/elevator.h
@@ -78,10 +78,19 @@ struct elv_fs_entry {
  */
 struct elevator_type
 {
+        /* managed by elevator core */
+        struct kmem_cache *icq_cache;
+
+        /* fields provided by elevator implementation */
         struct elevator_ops ops;
+        size_t icq_size;
+        size_t icq_align;
         struct elv_fs_entry *elevator_attrs;
         char elevator_name[ELV_NAME_MAX];
         struct module *elevator_owner;
+
+        /* managed by elevator core */
+        char icq_cache_name[ELV_NAME_MAX + 5];  /* elvname + "_io_cq" */
         struct list_head list;
 };
 
@@ -127,7 +136,7 @@ extern void elv_drain_elevator(struct request_queue *);
 /*
  * io scheduler registration
  */
-extern void elv_register(struct elevator_type *);
+extern int elv_register(struct elevator_type *);
 extern void elv_unregister(struct elevator_type *);
 
 /*