block,elevator: use new hashtable implementation

Switch elevator to use the new hashtable implementation. This reduces the
amount of generic unrelated code in the elevator.

This also removes the dymanic allocation of the hash table. The size of the table is
constant so there's no point in paying the price of an extra dereference when accessing
it.

This patch depends on d9b482c ("hashtable: introduce a small and naive
hashtable") which was merged in v3.6.

Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 4 insertions, 1 deletions

diff --git a/include/linux/elevator.h b/include/linux/elevator.h
index c03af7687bb4..7c5a7c9789ee 100644
--- a/include/linux/elevator.h
+++ b/include/linux/elevator.h
@@ -2,6 +2,7 @@
 #define _LINUX_ELEVATOR_H
 
 #include <linux/percpu.h>
+#include <linux/hashtable.h>
 
 #ifdef CONFIG_BLOCK
 
@@ -96,6 +97,8 @@ struct elevator_type
         struct list_head list;
 };
 
+#define ELV_HASH_BITS 6
+
 /*
  * each queue has an elevator_queue associated with it
  */
@@ -105,8 +108,8 @@ struct elevator_queue
         void *elevator_data;
         struct kobject kobj;
         struct mutex sysfs_lock;
-        struct hlist_head *hash;
         unsigned int registered:1;
+        DECLARE_HASHTABLE(hash, ELV_HASH_BITS);
 };
 
 /*