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

Ming Lei
2017-08-05T06:58:11Z

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.lei@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