[PATCH V5 3/8] block: introduce rqhash helpers

[Ming Lei <ming.lei@xxxxxxxxxx>]

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

No functional change.

Tested-by: Oleksandr Natalenko <oleksandr@xxxxxxxxxxxxxx>
Tested-by: Tom Nguyen <tom81094@xxxxxxxxx>
Tested-by: Paolo Valente <paolo.valente@xxxxxxxxxx>
Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
---
 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 fcb9775b997d..eb3436d4a73f 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -146,6 +146,58 @@ 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 153926a90901..824cc3e69ac3 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);
 }
 
 /*
-- 
2.9.5