[PATCH V2 15/20] block: introduce rqhash helpers

[Ming Lei]

We need this helpers for supporting to use hashtable to improve
bio merge from sw queue in the following patches.

No functional change.

Signed-off-by: Ming Lei <ming....@redhat.com>
---
 block/blk.h      | 52 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 block/elevator.c | 36 +++++++-----------------------------
 2 files changed, 59 insertions(+), 29 deletions(-)

diff --git a/block/blk.h b/block/blk.h
index 3a3d715bd725..313002c2f666 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -147,6 +147,58 @@ static inline void blk_clear_rq_complete(struct request 
*rq)
  */
 #define ELV_ON_HASH(rq) ((rq)->rq_flags & RQF_HASHED)
 
+/*
+ * Merge hash stuff.
+ */
+#define rq_hash_key(rq)                (blk_rq_pos(rq) + blk_rq_sectors(rq))
+
+#define bucket(head, key)      &((head)[hash_min((key), ELV_HASH_BITS)])
+
+static inline void __rqhash_del(struct request *rq)
+{
+       hash_del(&rq->hash);
+       rq->rq_flags &= ~RQF_HASHED;
+}
+
+static inline void rqhash_del(struct request *rq)
+{
+       if (ELV_ON_HASH(rq))
+               __rqhash_del(rq);
+}
+
+static inline void rqhash_add(struct hlist_head *hash, struct request *rq)
+{
+       BUG_ON(ELV_ON_HASH(rq));
+       hlist_add_head(&rq->hash, bucket(hash, rq_hash_key(rq)));
+       rq->rq_flags |= RQF_HASHED;
+}
+
+static inline void rqhash_reposition(struct hlist_head *hash, struct request 
*rq)
+{
+       __rqhash_del(rq);
+       rqhash_add(hash, rq);
+}
+
+static inline struct request *rqhash_find(struct hlist_head *hash, sector_t 
offset)
+{
+       struct hlist_node *next;
+       struct request *rq = NULL;
+
+       hlist_for_each_entry_safe(rq, next, bucket(hash, offset), hash) {
+               BUG_ON(!ELV_ON_HASH(rq));
+
+               if (unlikely(!rq_mergeable(rq))) {
+                       __rqhash_del(rq);
+                       continue;
+               }
+
+               if (rq_hash_key(rq) == offset)
+                       return rq;
+       }
+
+       return NULL;
+}
+
 void blk_insert_flush(struct request *rq);
 
 static inline struct request *__elv_next_request(struct request_queue *q)
diff --git a/block/elevator.c b/block/elevator.c
index 4bb2f0c93fa6..7423e9c9cb27 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -47,11 +47,6 @@ static DEFINE_SPINLOCK(elv_list_lock);
 static LIST_HEAD(elv_list);
 
 /*
- * Merge hash stuff.
- */
-#define rq_hash_key(rq)                (blk_rq_pos(rq) + blk_rq_sectors(rq))
-
-/*
  * Query io scheduler to see if the current process issuing bio may be
  * merged with rq.
  */
@@ -268,14 +263,12 @@ EXPORT_SYMBOL(elevator_exit);
 
 static inline void __elv_rqhash_del(struct request *rq)
 {
-       hash_del(&rq->hash);
-       rq->rq_flags &= ~RQF_HASHED;
+       __rqhash_del(rq);
 }
 
 void elv_rqhash_del(struct request_queue *q, struct request *rq)
 {
-       if (ELV_ON_HASH(rq))
-               __elv_rqhash_del(rq);
+       rqhash_del(rq);
 }
 EXPORT_SYMBOL_GPL(elv_rqhash_del);
 
@@ -283,37 +276,22 @@ void elv_rqhash_add(struct request_queue *q, struct 
request *rq)
 {
        struct elevator_queue *e = q->elevator;
 
-       BUG_ON(ELV_ON_HASH(rq));
-       hash_add(e->hash, &rq->hash, rq_hash_key(rq));
-       rq->rq_flags |= RQF_HASHED;
+       rqhash_add(e->hash, rq);
 }
 EXPORT_SYMBOL_GPL(elv_rqhash_add);
 
 void elv_rqhash_reposition(struct request_queue *q, struct request *rq)
 {
-       __elv_rqhash_del(rq);
-       elv_rqhash_add(q, rq);
+       struct elevator_queue *e = q->elevator;
+
+       rqhash_reposition(e->hash, rq);
 }
 
 struct request *elv_rqhash_find(struct request_queue *q, sector_t offset)
 {
        struct elevator_queue *e = q->elevator;
-       struct hlist_node *next;
-       struct request *rq;
-
-       hash_for_each_possible_safe(e->hash, rq, next, hash, offset) {
-               BUG_ON(!ELV_ON_HASH(rq));
 
-               if (unlikely(!rq_mergeable(rq))) {
-                       __elv_rqhash_del(rq);
-                       continue;
-               }
-
-               if (rq_hash_key(rq) == offset)
-                       return rq;
-       }
-
-       return NULL;
+       return rqhash_find(e->hash, offset);
 }
 
 /*
-- 
2.9.4