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>

diff --git a/block/blk.h b/block/blk.h
index 47fdfdd41520611f59caca02bfeb0623951fa9d5..e837b8f619b7d646825d43ea5ddeb9beacbea3d2 100644 (file)
--- a/block/blk.h
+++ b/block/blk.h
@@ -61,7 +61,7 @@ static inline void blk_clear_rq_complete(struct request *rq)
 /*
  * Internal elevator interface
  */
-#define ELV_ON_HASH(rq)                (!hlist_unhashed(&(rq)->hash))
+#define ELV_ON_HASH(rq) hash_hashed(&(rq)->hash)
 
 void blk_insert_flush(struct request *rq);
 void blk_abort_flushes(struct request_queue *q);

diff --git a/block/elevator.c b/block/elevator.c
index 9edba1b8323ed713f17f475511a370d2cdd8df47..11683bb10b7b75e6f94d1124d91fe549a8934a65 100644 (file)
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -46,11 +46,6 @@ static LIST_HEAD(elv_list);
 /*
  * Merge hash stuff.
  */
-static const int elv_hash_shift = 6;
-#define ELV_HASH_BLOCK(sec)    ((sec) >> 3)
-#define ELV_HASH_FN(sec)       \
-               (hash_long(ELV_HASH_BLOCK((sec)), elv_hash_shift))
-#define ELV_HASH_ENTRIES       (1 << elv_hash_shift)
 #define rq_hash_key(rq)                (blk_rq_pos(rq) + blk_rq_sectors(rq))
 
 /*
@@ -142,7 +137,6 @@ static struct elevator_queue *elevator_alloc(struct request_queue *q,
                                  struct elevator_type *e)
 {
        struct elevator_queue *eq;
-       int i;
 
        eq = kmalloc_node(sizeof(*eq), GFP_KERNEL | __GFP_ZERO, q->node);
        if (unlikely(!eq))
@@ -151,14 +145,7 @@ static struct elevator_queue *elevator_alloc(struct request_queue *q,
        eq->type = e;
        kobject_init(&eq->kobj, &elv_ktype);
        mutex_init(&eq->sysfs_lock);
-
-       eq->hash = kmalloc_node(sizeof(struct hlist_head) * ELV_HASH_ENTRIES,
-                                       GFP_KERNEL, q->node);
-       if (!eq->hash)
-               goto err;
-
-       for (i = 0; i < ELV_HASH_ENTRIES; i++)
-               INIT_HLIST_HEAD(&eq->hash[i]);
+       hash_init(eq->hash);
 
        return eq;
 err:
@@ -173,7 +160,6 @@ static void elevator_release(struct kobject *kobj)
 
        e = container_of(kobj, struct elevator_queue, kobj);
        elevator_put(e->type);
-       kfree(e->hash);
        kfree(e);
 }
 
@@ -240,7 +226,7 @@ EXPORT_SYMBOL(elevator_exit);
 
 static inline void __elv_rqhash_del(struct request *rq)
 {
-       hlist_del_init(&rq->hash);
+       hash_del(&rq->hash);
 }
 
 static void elv_rqhash_del(struct request_queue *q, struct request *rq)
@@ -254,7 +240,7 @@ static void elv_rqhash_add(struct request_queue *q, struct request *rq)
        struct elevator_queue *e = q->elevator;
 
        BUG_ON(ELV_ON_HASH(rq));
-       hlist_add_head(&rq->hash, &e->hash[ELV_HASH_FN(rq_hash_key(rq))]);
+       hash_add(e->hash, &rq->hash, rq_hash_key(rq));
 }
 
 static void elv_rqhash_reposition(struct request_queue *q, struct request *rq)
@@ -266,11 +252,10 @@ static void elv_rqhash_reposition(struct request_queue *q, struct request *rq)
 static struct request *elv_rqhash_find(struct request_queue *q, sector_t offset)
 {
        struct elevator_queue *e = q->elevator;
-       struct hlist_head *hash_list = &e->hash[ELV_HASH_FN(offset)];
        struct hlist_node *entry, *next;
        struct request *rq;
 
-       hlist_for_each_entry_safe(rq, entry, next, hash_list, hash) {
+       hash_for_each_possible_safe(e->hash, rq, entry, next, hash, offset) {
                BUG_ON(!ELV_ON_HASH(rq));
 
                if (unlikely(!rq_mergeable(rq))) {

diff --git a/include/linux/elevator.h b/include/linux/elevator.h
index c03af7687bb4fdd916d5bf3c835e801376132392..7c5a7c9789ee63f17c1ece383679433412b4e678 100644 (file)
--- 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);
 };
 
 /*