5 files changed, 142 insertions, 360 deletions

diff --git a/block/as-iosched.c b/block/as-iosched.c
index ad1cc407781..6db494333c3 100644
--- a/block/as-iosched.c
+++ b/block/as-iosched.c
@@ -14,7 +14,6 @@
 #include <linux/slab.h>
 #include <linux/init.h>
 #include <linux/compiler.h>
-#include <linux/hash.h>
 #include <linux/rbtree.h>
 #include <linux/interrupt.h>
 
@@ -95,7 +94,6 @@ struct as_data {
 
 	struct as_rq *next_arq[2];	/* next in sort order */
 	sector_t last_sector[2];	/* last REQ_SYNC & REQ_ASYNC sectors */
-	struct hlist_head *hash;	/* request hash */
 
 	unsigned long exit_prob;	/* probability a task will exit while
 					   being waited on */
@@ -162,11 +160,6 @@ struct as_rq {
 	struct io_context *io_context;	/* The submitting task */
 
 	/*
-	 * request hash, key is the ending offset (for back merge lookup)
-	 */
-	struct hlist_node hash;
-
-	/*
 	 * expire fifo
 	 */
 	struct list_head fifo;
@@ -273,77 +266,6 @@ static void as_put_io_context(struct as_rq *arq)
 }
 
 /*
- * the back merge hash support functions
- */
-static const int as_hash_shift = 6;
-#define AS_HASH_BLOCK(sec)	((sec) >> 3)
-#define AS_HASH_FN(sec)		(hash_long(AS_HASH_BLOCK((sec)), as_hash_shift))
-#define AS_HASH_ENTRIES		(1 << as_hash_shift)
-#define rq_hash_key(rq)		((rq)->sector + (rq)->nr_sectors)
-
-static inline void __as_del_arq_hash(struct as_rq *arq)
-{
-	hlist_del_init(&arq->hash);
-}
-
-static inline void as_del_arq_hash(struct as_rq *arq)
-{
-	if (!hlist_unhashed(&arq->hash))
-		__as_del_arq_hash(arq);
-}
-
-static void as_add_arq_hash(struct as_data *ad, struct as_rq *arq)
-{
-	struct request *rq = arq->request;
-
-	BUG_ON(!hlist_unhashed(&arq->hash));
-
-	hlist_add_head(&arq->hash, &ad->hash[AS_HASH_FN(rq_hash_key(rq))]);
-}
-
-/*
- * move hot entry to front of chain
- */
-static inline void as_hot_arq_hash(struct as_data *ad, struct as_rq *arq)
-{
-	struct request *rq = arq->request;
-	struct hlist_head *head = &ad->hash[AS_HASH_FN(rq_hash_key(rq))];
-
-	if (hlist_unhashed(&arq->hash)) {
-		WARN_ON(1);
-		return;
-	}
-
-	if (&arq->hash != head->first) {
-		hlist_del(&arq->hash);
-		hlist_add_head(&arq->hash, head);
-	}
-}
-
-static struct request *as_find_arq_hash(struct as_data *ad, sector_t offset)
-{
-	struct hlist_head *hash_list = &ad->hash[AS_HASH_FN(offset)];
-	struct hlist_node *entry, *next;
-	struct as_rq *arq;
-
-	hlist_for_each_entry_safe(arq, entry, next, hash_list, hash) {
-		struct request *__rq = arq->request;
-
-		BUG_ON(hlist_unhashed(&arq->hash));
-
-		if (!rq_mergeable(__rq)) {
-			as_del_arq_hash(arq);
-			continue;
-		}
-
-		if (rq_hash_key(__rq) == offset)
-			return __rq;
-	}
-
-	return NULL;
-}
-
-/*
  * rb tree support functions
  */
 #define rb_entry_arq(node)	rb_entry((node), struct as_rq, rb_node)
@@ -1060,7 +982,6 @@ static void as_remove_queued_request(request_queue_t *q, struct request *rq)
 		ad->next_arq[data_dir] = as_find_next_arq(ad, arq);
 
 	list_del_init(&arq->fifo);
-	as_del_arq_hash(arq);
 	as_del_arq_rb(ad, arq);
 }
 
@@ -1349,8 +1270,6 @@ static void as_add_request(request_queue_t *q, struct request *rq)
 	}
 
 	as_add_arq_rb(ad, arq);
-	if (rq_mergeable(arq->request))
-		as_add_arq_hash(ad, arq);
 
 	/*
 	 * set expire time (only used for reads) and add to fifo list
@@ -1428,42 +1347,17 @@ as_merge(request_queue_t *q, struct request **req, struct bio *bio)
 	struct as_data *ad = q->elevator->elevator_data;
 	sector_t rb_key = bio->bi_sector + bio_sectors(bio);
 	struct request *__rq;
-	int ret;
-
-	/*
-	 * see if the merge hash can satisfy a back merge
-	 */
-	__rq = as_find_arq_hash(ad, bio->bi_sector);
-	if (__rq) {
-		BUG_ON(__rq->sector + __rq->nr_sectors != bio->bi_sector);
-
-		if (elv_rq_merge_ok(__rq, bio)) {
-			ret = ELEVATOR_BACK_MERGE;
-			goto out;
-		}
-	}
 
 	/*
 	 * check for front merge
 	 */
 	__rq = as_find_arq_rb(ad, rb_key, bio_data_dir(bio));
-	if (__rq) {
-		BUG_ON(rb_key != rq_rb_key(__rq));
-
-		if (elv_rq_merge_ok(__rq, bio)) {
-			ret = ELEVATOR_FRONT_MERGE;
-			goto out;
-		}
+	if (__rq && elv_rq_merge_ok(__rq, bio)) {
+		*req = __rq;
+		return ELEVATOR_FRONT_MERGE;
 	}
 
 	return ELEVATOR_NO_MERGE;
-out:
-	if (ret) {
-		if (rq_mergeable(__rq))
-			as_hot_arq_hash(ad, RQ_DATA(__rq));
-	}
-	*req = __rq;
-	return ret;
 }
 
 static void as_merged_request(request_queue_t *q, struct request *req)
@@ -1472,12 +1366,6 @@ static void as_merged_request(request_queue_t *q, struct request *req)
 	struct as_rq *arq = RQ_DATA(req);
 
 	/*
-	 * hash always needs to be repositioned, key is end sector
-	 */
-	as_del_arq_hash(arq);
-	as_add_arq_hash(ad, arq);
-
-	/*
 	 * if the merge was a front merge, we need to reposition request
 	 */
 	if (rq_rb_key(req) != arq->rb_key) {
@@ -1501,13 +1389,6 @@ static void as_merged_requests(request_queue_t *q, struct request *req,
 	BUG_ON(!arq);
 	BUG_ON(!anext);
 
-	/*
-	 * reposition arq (this is the merged request) in hash, and in rbtree
-	 * in case of a front merge
-	 */
-	as_del_arq_hash(arq);
-	as_add_arq_hash(ad, arq);
-
 	if (rq_rb_key(req) != arq->rb_key) {
 		as_del_arq_rb(ad, arq);
 		as_add_arq_rb(ad, arq);
@@ -1591,7 +1472,6 @@ static int as_set_request(request_queue_t *q, struct request *rq,
 		arq->request = rq;
 		arq->state = AS_RQ_PRESCHED;
 		arq->io_context = NULL;
-		INIT_HLIST_NODE(&arq->hash);
 		INIT_LIST_HEAD(&arq->fifo);
 		rq->elevator_private = arq;
 		return 0;
@@ -1628,7 +1508,6 @@ static void as_exit_queue(elevator_t *e)
 
 	mempool_destroy(ad->arq_pool);
 	put_io_context(ad->io_context);
-	kfree(ad->hash);
 	kfree(ad);
 }
 
@@ -1639,7 +1518,6 @@ static void as_exit_queue(elevator_t *e)
 static void *as_init_queue(request_queue_t *q, elevator_t *e)
 {
 	struct as_data *ad;
-	int i;
 
 	if (!arq_pool)
 		return NULL;
@@ -1651,17 +1529,9 @@ static void *as_init_queue(request_queue_t *q, elevator_t *e)
 
 	ad->q = q; /* Identify what queue the data belongs to */
 
-	ad->hash = kmalloc_node(sizeof(struct hlist_head)*AS_HASH_ENTRIES,
-				GFP_KERNEL, q->node);
-	if (!ad->hash) {
-		kfree(ad);
-		return NULL;
-	}
-
 	ad->arq_pool = mempool_create_node(BLKDEV_MIN_RQ, mempool_alloc_slab,
 				mempool_free_slab, arq_pool, q->node);
 	if (!ad->arq_pool) {
-		kfree(ad->hash);
 		kfree(ad);
 		return NULL;
 	}
@@ -1672,9 +1542,6 @@ static void *as_init_queue(request_queue_t *q, elevator_t *e)
 	init_timer(&ad->antic_timer);
 	INIT_WORK(&ad->antic_work, as_work_handler, q);
 
-	for (i = 0; i < AS_HASH_ENTRIES; i++)
-		INIT_HLIST_HEAD(&ad->hash[i]);
-
 	INIT_LIST_HEAD(&ad->fifo_list[REQ_SYNC]);
 	INIT_LIST_HEAD(&ad->fifo_list[REQ_ASYNC]);
 	ad->sort_list[REQ_SYNC] = RB_ROOT;
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 3a3aee08ec5..1b803c0c90f 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -41,16 +41,6 @@ static DEFINE_SPINLOCK(cfq_exit_lock);
 #define CFQ_QHASH_ENTRIES	(1 << CFQ_QHASH_SHIFT)
 #define list_entry_qhash(entry)	hlist_entry((entry), struct cfq_queue, cfq_hash)
 
-/*
- * for the hash of crq inside the cfqq
- */
-#define CFQ_MHASH_SHIFT		6
-#define CFQ_MHASH_BLOCK(sec)	((sec) >> 3)
-#define CFQ_MHASH_ENTRIES	(1 << CFQ_MHASH_SHIFT)
-#define CFQ_MHASH_FN(sec)	hash_long(CFQ_MHASH_BLOCK(sec), CFQ_MHASH_SHIFT)
-#define rq_hash_key(rq)		((rq)->sector + (rq)->nr_sectors)
-#define list_entry_hash(ptr)	hlist_entry((ptr), struct cfq_rq, hash)
-
 #define list_entry_cfqq(ptr)	list_entry((ptr), struct cfq_queue, cfq_list)
 #define list_entry_fifo(ptr)	list_entry((ptr), struct request, queuelist)
 
@@ -112,11 +102,6 @@ struct cfq_data {
 	 */
 	struct hlist_head *cfq_hash;
 
-	/*
-	 * global crq hash for all queues
-	 */
-	struct hlist_head *crq_hash;
-
 	mempool_t *crq_pool;
 
 	int rq_in_driver;
@@ -203,7 +188,6 @@ struct cfq_rq {
 	struct rb_node rb_node;
 	sector_t rb_key;
 	struct request *request;
-	struct hlist_node hash;
 
 	struct cfq_queue *cfq_queue;
 	struct cfq_io_context *io_context;
@@ -272,42 +256,6 @@ static void cfq_dispatch_insert(request_queue_t *, struct cfq_rq *);
 static struct cfq_queue *cfq_get_queue(struct cfq_data *cfqd, unsigned int key, struct task_struct *tsk, gfp_t gfp_mask);
 
 /*
- * lots of deadline iosched dupes, can be abstracted later...
- */
-static inline void cfq_del_crq_hash(struct cfq_rq *crq)
-{
-	hlist_del_init(&crq->hash);
-}
-
-static inline void cfq_add_crq_hash(struct cfq_data *cfqd, struct cfq_rq *crq)
-{
-	const int hash_idx = CFQ_MHASH_FN(rq_hash_key(crq->request));
-
-	hlist_add_head(&crq->hash, &cfqd->crq_hash[hash_idx]);
-}
-
-static struct request *cfq_find_rq_hash(struct cfq_data *cfqd, sector_t offset)
-{
-	struct hlist_head *hash_list = &cfqd->crq_hash[CFQ_MHASH_FN(offset)];
-	struct hlist_node *entry, *next;
-
-	hlist_for_each_safe(entry, next, hash_list) {
-		struct cfq_rq *crq = list_entry_hash(entry);
-		struct request *__rq = crq->request;
-
-		if (!rq_mergeable(__rq)) {
-			cfq_del_crq_hash(crq);
-			continue;
-		}
-
-		if (rq_hash_key(__rq) == offset)
-			return __rq;
-	}
-
-	return NULL;
-}
-
-/*
  * scheduler run of queue, if there are requests pending and no one in the
  * driver that will restart queueing
  */
@@ -677,7 +625,6 @@ static void cfq_remove_request(struct request *rq)
 
 	list_del_init(&rq->queuelist);
 	cfq_del_crq_rb(crq);
-	cfq_del_crq_hash(crq);
 }
 
 static int
@@ -685,34 +632,20 @@ cfq_merge(request_queue_t *q, struct request **req, struct bio *bio)
 {
 	struct cfq_data *cfqd = q->elevator->elevator_data;
 	struct request *__rq;
-	int ret;
-
-	__rq = cfq_find_rq_hash(cfqd, bio->bi_sector);
-	if (__rq && elv_rq_merge_ok(__rq, bio)) {
-		ret = ELEVATOR_BACK_MERGE;
-		goto out;
-	}
 
 	__rq = cfq_find_rq_fmerge(cfqd, bio);
 	if (__rq && elv_rq_merge_ok(__rq, bio)) {
-		ret = ELEVATOR_FRONT_MERGE;
-		goto out;
+		*req = __rq;
+		return ELEVATOR_FRONT_MERGE;
 	}
 
 	return ELEVATOR_NO_MERGE;
-out:
-	*req = __rq;
-	return ret;
 }
 
 static void cfq_merged_request(request_queue_t *q, struct request *req)
 {
-	struct cfq_data *cfqd = q->elevator->elevator_data;
 	struct cfq_rq *crq = RQ_DATA(req);
 
-	cfq_del_crq_hash(crq);
-	cfq_add_crq_hash(cfqd, crq);
-
 	if (rq_rb_key(req) != crq->rb_key) {
 		struct cfq_queue *cfqq = crq->cfq_queue;
 
@@ -1825,9 +1758,6 @@ static void cfq_insert_request(request_queue_t *q, struct request *rq)
 
 	list_add_tail(&rq->queuelist, &cfqq->fifo);
 
-	if (rq_mergeable(rq))
-		cfq_add_crq_hash(cfqd, crq);
-
 	cfq_crq_enqueued(cfqd, cfqq, crq);
 }
 
@@ -2055,7 +1985,6 @@ cfq_set_request(request_queue_t *q, struct request *rq, struct bio *bio,
 		RB_CLEAR_NODE(&crq->rb_node);
 		crq->rb_key = 0;
 		crq->request = rq;
-		INIT_HLIST_NODE(&crq->hash);
 		crq->cfq_queue = cfqq;
 		crq->io_context = cic;
 
@@ -2221,7 +2150,6 @@ static void cfq_exit_queue(elevator_t *e)
 	cfq_shutdown_timer_wq(cfqd);
 
 	mempool_destroy(cfqd->crq_pool);
-	kfree(cfqd->crq_hash);
 	kfree(cfqd->cfq_hash);
 	kfree(cfqd);
 }
@@ -2246,20 +2174,14 @@ static void *cfq_init_queue(request_queue_t *q, elevator_t *e)
 	INIT_LIST_HEAD(&cfqd->empty_list);
 	INIT_LIST_HEAD(&cfqd->cic_list);
 
-	cfqd->crq_hash = kmalloc(sizeof(struct hlist_head) * CFQ_MHASH_ENTRIES, GFP_KERNEL);
-	if (!cfqd->crq_hash)
-		goto out_crqhash;
-
 	cfqd->cfq_hash = kmalloc(sizeof(struct hlist_head) * CFQ_QHASH_ENTRIES, GFP_KERNEL);
 	if (!cfqd->cfq_hash)
-		goto out_cfqhash;
+		goto out_crqhash;
 
 	cfqd->crq_pool = mempool_create_slab_pool(BLKDEV_MIN_RQ, crq_pool);
 	if (!cfqd->crq_pool)
 		goto out_crqpool;
 
-	for (i = 0; i < CFQ_MHASH_ENTRIES; i++)
-		INIT_HLIST_HEAD(&cfqd->crq_hash[i]);
 	for (i = 0; i < CFQ_QHASH_ENTRIES; i++)
 		INIT_HLIST_HEAD(&cfqd->cfq_hash[i]);
 
@@ -2289,8 +2211,6 @@ static void *cfq_init_queue(request_queue_t *q, elevator_t *e)
 	return cfqd;
 out_crqpool:
 	kfree(cfqd->cfq_hash);
-out_cfqhash:
-	kfree(cfqd->crq_hash);
 out_crqhash:
 	kfree(cfqd);
 	return NULL;
diff --git a/block/deadline-iosched.c b/block/deadline-iosched.c
index c7ca9f0b649..b66e820f544 100644
--- a/block/deadline-iosched.c
+++ b/block/deadline-iosched.c
@@ -12,7 +12,6 @@
 #include <linux/slab.h>
 #include <linux/init.h>
 #include <linux/compiler.h>
-#include <linux/hash.h>
 #include <linux/rbtree.h>
 
 /*
@@ -24,13 +23,6 @@ static const int writes_starved = 2;    /* max times reads can starve a write */
 static const int fifo_batch = 16;       /* # of sequential requests treated as one
 				     by the above parameters. For throughput. */
 
-static const int deadline_hash_shift = 5;
-#define DL_HASH_BLOCK(sec)	((sec) >> 3)
-#define DL_HASH_FN(sec)		(hash_long(DL_HASH_BLOCK((sec)), deadline_hash_shift))
-#define DL_HASH_ENTRIES		(1 << deadline_hash_shift)
-#define rq_hash_key(rq)		((rq)->sector + (rq)->nr_sectors)
-#define ON_HASH(drq)		(!hlist_unhashed(&(drq)->hash))
-
 struct deadline_data {
 	/*
 	 * run time data
@@ -46,7 +38,6 @@ struct deadline_data {
 	 * next in sort order. read, write or both are NULL
 	 */
 	struct deadline_rq *next_drq[2];
-	struct hlist_head *hash;	/* request hash */
 	unsigned int batching;		/* number of sequential requests made */
 	sector_t last_sector;		/* head position */
 	unsigned int starved;		/* times reads have starved writes */
@@ -75,11 +66,6 @@ struct deadline_rq {
 	struct request *request;
 
 	/*
-	 * request hash, key is the ending offset (for back merge lookup)
-	 */
-	struct hlist_node hash;
-
-	/*
 	 * expire fifo
 	 */
 	struct list_head fifo;
@@ -93,69 +79,6 @@ static kmem_cache_t *drq_pool;
 #define RQ_DATA(rq)	((struct deadline_rq *) (rq)->elevator_private)
 
 /*
- * the back merge hash support functions
- */
-static inline void __deadline_del_drq_hash(struct deadline_rq *drq)
-{
-	hlist_del_init(&drq->hash);
-}
-
-static inline void deadline_del_drq_hash(struct deadline_rq *drq)
-{
-	if (ON_HASH(drq))
-		__deadline_del_drq_hash(drq);
-}
-
-static inline void
-deadline_add_drq_hash(struct deadline_data *dd, struct deadline_rq *drq)
-{
-	struct request *rq = drq->request;
-
-	BUG_ON(ON_HASH(drq));
-
-	hlist_add_head(&drq->hash, &dd->hash[DL_HASH_FN(rq_hash_key(rq))]);
-}
-
-/*
- * move hot entry to front of chain
- */
-static inline void
-deadline_hot_drq_hash(struct deadline_data *dd, struct deadline_rq *drq)
-{
-	struct request *rq = drq->request;
-	struct hlist_head *head = &dd->hash[DL_HASH_FN(rq_hash_key(rq))];
-
-	if (ON_HASH(drq) && &drq->hash != head->first) {
-		hlist_del(&drq->hash);
-		hlist_add_head(&drq->hash, head);
-	}
-}
-
-static struct request *
-deadline_find_drq_hash(struct deadline_data *dd, sector_t offset)
-{
-	struct hlist_head *hash_list = &dd->hash[DL_HASH_FN(offset)];
-	struct hlist_node *entry, *next;
-	struct deadline_rq *drq;
-
-	hlist_for_each_entry_safe(drq, entry, next, hash_list, hash) {
-		struct request *__rq = drq->request;
-
-		BUG_ON(!ON_HASH(drq));
-
-		if (!rq_mergeable(__rq)) {
-			__deadline_del_drq_hash(drq);
-			continue;
-		}
-
-		if (rq_hash_key(__rq) == offset)
-			return __rq;
-	}
-
-	return NULL;
-}
-
-/*
  * rb tree support functions
  */
 #define rb_entry_drq(node)	rb_entry((node), struct deadline_rq, rb_node)
@@ -267,22 +190,19 @@ deadline_add_request(struct request_queue *q, struct request *rq)
 {
 	struct deadline_data *dd = q->elevator->elevator_data;
 	struct deadline_rq *drq = RQ_DATA(rq);
-
 	const int data_dir = rq_data_dir(drq->request);
 
 	deadline_add_drq_rb(dd, drq);
+
 	/*
 	 * set expire time (only used for reads) and add to fifo list
 	 */
 	drq->expires = jiffies + dd->fifo_expire[data_dir];
 	list_add_tail(&drq->fifo, &dd->fifo_list[data_dir]);
-
-	if (rq_mergeable(rq))
-		deadline_add_drq_hash(dd, drq);
 }
 
 /*
- * remove rq from rbtree, fifo, and hash
+ * remove rq from rbtree and fifo.
  */
 static void deadline_remove_request(request_queue_t *q, struct request *rq)
 {
@@ -291,7 +211,6 @@ static void deadline_remove_request(request_queue_t *q, struct request *rq)
 
 	list_del_init(&drq->fifo);
 	deadline_del_drq_rb(dd, drq);
-	deadline_del_drq_hash(drq);
 }
 
 static int
@@ -302,19 +221,6 @@ deadline_merge(request_queue_t *q, struct request **req, struct bio *bio)
 	int ret;
 
 	/*
-	 * see if the merge hash can satisfy a back merge
-	 */
-	__rq = deadline_find_drq_hash(dd, bio->bi_sector);
-	if (__rq) {
-		BUG_ON(__rq->sector + __rq->nr_sectors != bio->bi_sector);
-
-		if (elv_rq_merge_ok(__rq, bio)) {
-			ret = ELEVATOR_BACK_MERGE;
-			goto out;
-		}
-	}
-
-	/*
 	 * check for front merge
 	 */
 	if (dd->front_merges) {
@@ -333,8 +239,6 @@ deadline_merge(request_queue_t *q, struct request **req, struct bio *bio)
 
 	return ELEVATOR_NO_MERGE;
 out:
-	if (ret)
-		deadline_hot_drq_hash(dd, RQ_DATA(__rq));
 	*req = __rq;
 	return ret;
 }
@@ -345,12 +249,6 @@ static void deadline_merged_request(request_queue_t *q, struct request *req)
 	struct deadline_rq *drq = RQ_DATA(req);
 
 	/*
-	 * hash always needs to be repositioned, key is end sector
-	 */
-	deadline_del_drq_hash(drq);
-	deadline_add_drq_hash(dd, drq);
-
-	/*
 	 * if the merge was a front merge, we need to reposition request
 	 */
 	if (rq_rb_key(req) != drq->rb_key) {
@@ -370,13 +268,6 @@ deadline_merged_requests(request_queue_t *q, struct request *req,
 	BUG_ON(!drq);
 	BUG_ON(!dnext);
 
-	/*
-	 * reposition drq (this is the merged request) in hash, and in rbtree
-	 * in case of a front merge
-	 */
-	deadline_del_drq_hash(drq);
-	deadline_add_drq_hash(dd, drq);
-
 	if (rq_rb_key(req) != drq->rb_key) {
 		deadline_del_drq_rb(dd, drq);
 		deadline_add_drq_rb(dd, drq);
@@ -594,7 +485,6 @@ static void deadline_exit_queue(elevator_t *e)
 	BUG_ON(!list_empty(&dd->fifo_list[WRITE]));
 
 	mempool_destroy(dd->drq_pool);
-	kfree(dd->hash);
 	kfree(dd);
 }
 
@@ -605,7 +495,6 @@ static void deadline_exit_queue(elevator_t *e)
 static void *deadline_init_queue(request_queue_t *q, elevator_t *e)
 {
 	struct deadline_data *dd;
-	int i;
 
 	if (!drq_pool)
 		return NULL;
@@ -615,24 +504,13 @@ static void *deadline_init_queue(request_queue_t *q, elevator_t *e)
 		return NULL;
 	memset(dd, 0, sizeof(*dd));
 
-	dd->hash = kmalloc_node(sizeof(struct hlist_head)*DL_HASH_ENTRIES,
-				GFP_KERNEL, q->node);
-	if (!dd->hash) {
-		kfree(dd);
-		return NULL;
-	}
-
 	dd->drq_pool = mempool_create_node(BLKDEV_MIN_RQ, mempool_alloc_slab,
 					mempool_free_slab, drq_pool, q->node);
 	if (!dd->drq_pool) {
-		kfree(dd->hash);
 		kfree(dd);
 		return NULL;
 	}
 
-	for (i = 0; i < DL_HASH_ENTRIES; i++)
-		INIT_HLIST_HEAD(&dd->hash[i]);
-
 	INIT_LIST_HEAD(&dd->fifo_list[READ]);
 	INIT_LIST_HEAD(&dd->fifo_list[WRITE]);
 	dd->sort_list[READ] = RB_ROOT;
@@ -667,8 +545,6 @@ deadline_set_request(request_queue_t *q, struct request *rq, struct bio *bio,
 		RB_CLEAR_NODE(&drq->rb_node);
 		drq->request = rq;
 
-		INIT_HLIST_NODE(&drq->hash);
-
 		INIT_LIST_HEAD(&drq->fifo);
 
 		rq->elevator_private = drq;
diff --git a/block/elevator.c b/block/elevator.c
index 4ac97b64204..cff1102dac9 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -33,6 +33,7 @@
 #include <linux/compiler.h>
 #include <linux/delay.h>
 #include <linux/blktrace_api.h>
+#include <linux/hash.h>
 
 #include <asm/uaccess.h>
 
@@ -40,6 +41,16 @@ static DEFINE_SPINLOCK(elv_list_lock);
 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)		((rq)->sector + (rq)->nr_sectors)
+#define ELV_ON_HASH(rq)		(!hlist_unhashed(&(rq)->hash))
+
+/*
  * can we safely merge with this request?
  */
 inline int elv_rq_merge_ok(struct request *rq, struct bio *bio)
@@ -153,25 +164,41 @@ static struct kobj_type elv_ktype;
 
 static elevator_t *elevator_alloc(struct elevator_type *e)
 {
-	elevator_t *eq = kmalloc(sizeof(elevator_t), GFP_KERNEL);
-	if (eq) {
-		memset(eq, 0, sizeof(*eq));
-		eq->ops = &e->ops;
-		eq->elevator_type = e;
-		kobject_init(&eq->kobj);
-		snprintf(eq->kobj.name, KOBJ_NAME_LEN, "%s", "iosched");
-		eq->kobj.ktype = &elv_ktype;
-		mutex_init(&eq->sysfs_lock);
-	} else {
-		elevator_put(e);
-	}
+	elevator_t *eq;
+	int i;
+
+	eq = kmalloc(sizeof(elevator_t), GFP_KERNEL);
+	if (unlikely(!eq))
+		goto err;
+
+	memset(eq, 0, sizeof(*eq));
+	eq->ops = &e->ops;
+	eq->elevator_type = e;
+	kobject_init(&eq->kobj);
+	snprintf(eq->kobj.name, KOBJ_NAME_LEN, "%s", "iosched");
+	eq->kobj.ktype = &elv_ktype;
+	mutex_init(&eq->sysfs_lock);
+
+	eq->hash = kmalloc(sizeof(struct hlist_head) * ELV_HASH_ENTRIES, GFP_KERNEL);
+	if (!eq->hash)
+		goto err;
+
+	for (i = 0; i < ELV_HASH_ENTRIES; i++)
+		INIT_HLIST_HEAD(&eq->hash[i]);
+
 	return eq;
+err:
+	kfree(eq);
+	elevator_put(e);
+	return NULL;
 }
 
 static void elevator_release(struct kobject *kobj)
 {
 	elevator_t *e = container_of(kobj, elevator_t, kobj);
+
 	elevator_put(e->elevator_type);
+	kfree(e->hash);
 	kfree(e);
 }
 
@@ -223,6 +250,53 @@ void elevator_exit(elevator_t *e)
 	kobject_put(&e->kobj);
 }
 
+static inline void __elv_rqhash_del(struct request *rq)
+{
+	hlist_del_init(&rq->hash);
+}
+
+static void elv_rqhash_del(request_queue_t *q, struct request *rq)
+{
+	if (ELV_ON_HASH(rq))
+		__elv_rqhash_del(rq);
+}
+
+static void elv_rqhash_add(request_queue_t *q, struct request *rq)
+{
+	elevator_t *e = q->elevator;
+
+	BUG_ON(ELV_ON_HASH(rq));
+	hlist_add_head(&rq->hash, &e->hash[ELV_HASH_FN(rq_hash_key(rq))]);
+}
+
+static void elv_rqhash_reposition(request_queue_t *q, struct request *rq)
+{
+	__elv_rqhash_del(rq);
+	elv_rqhash_add(q, rq);
+}
+
+static struct request *elv_rqhash_find(request_queue_t *q, sector_t offset)
+{
+	elevator_t *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) {
+		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;
+}
+
 /*
  * Insert rq into dispatch queue of q.  Queue lock must be held on
  * entry.  If sort != 0, rq is sort-inserted; otherwise, rq will be
@@ -235,6 +309,9 @@ void elv_dispatch_sort(request_queue_t *q, struct request *rq)
 
 	if (q->last_merge == rq)
 		q->last_merge = NULL;
+
+	elv_rqhash_del(q, rq);
+
 	q->nr_sorted--;
 
 	boundary = q->end_sector;
@@ -258,11 +335,32 @@ void elv_dispatch_sort(request_queue_t *q, struct request *rq)
 	list_add(&rq->queuelist, entry);
 }
 
+/*
+ * This should be in elevator.h, but that requires pulling in rq and q
+ */
+void elv_dispatch_add_tail(struct request_queue *q, struct request *rq)
+{
+	if (q->last_merge == rq)
+		q->last_merge = NULL;
+
+	elv_rqhash_del(q, rq);
+
+	q->nr_sorted--;
+
+	q->end_sector = rq_end_sector(rq);
+	q->boundary_rq = rq;
+	list_add_tail(&rq->queuelist, &q->queue_head);
+}
+
 int elv_merge(request_queue_t *q, struct request **req, struct bio *bio)
 {
 	elevator_t *e = q->elevator;
+	struct request *__rq;
 	int ret;
 
+	/*
+	 * First try one-hit cache.
+	 */
 	if (q->last_merge) {
 		ret = elv_try_merge(q->last_merge, bio);
 		if (ret != ELEVATOR_NO_MERGE) {
@@ -271,6 +369,15 @@ int elv_merge(request_queue_t *q, struct request **req, struct bio *bio)
 		}
 	}
 
+	/*
+	 * See if our hash lookup can find a potential backmerge.
+	 */
+	__rq = elv_rqhash_find(q, bio->bi_sector);
+	if (__rq && elv_rq_merge_ok(__rq, bio)) {
+		*req = __rq;
+		return ELEVATOR_BACK_MERGE;
+	}
+
 	if (e->ops->elevator_merge_fn)
 		return e->ops->elevator_merge_fn(q, req, bio);
 
@@ -284,6 +391,8 @@ void elv_merged_request(request_queue_t *q, struct request *rq)
 	if (e->ops->elevator_merged_fn)
 		e->ops->elevator_merged_fn(q, rq);
 
+	elv_rqhash_reposition(q, rq);
+
 	q->last_merge = rq;
 }
 
@@ -294,8 +403,11 @@ void elv_merge_requests(request_queue_t *q, struct request *rq,
 
 	if (e->ops->elevator_merge_req_fn)
 		e->ops->elevator_merge_req_fn(q, rq, next);
-	q->nr_sorted--;
 
+	elv_rqhash_reposition(q, rq);
+	elv_rqhash_del(q, next);
+
+	q->nr_sorted--;
 	q->last_merge = rq;
 }
 
@@ -371,8 +483,12 @@ void elv_insert(request_queue_t *q, struct request *rq, int where)
 		BUG_ON(!blk_fs_request(rq));
 		rq->cmd_flags |= REQ_SORTED;
 		q->nr_sorted++;
-		if (q->last_merge == NULL && rq_mergeable(rq))
-			q->last_merge = rq;
+		if (rq_mergeable(rq)) {
+			elv_rqhash_add(q, rq);
+			if (!q->last_merge)
+				q->last_merge = rq;
+		}
+
 		/*
 		 * Some ioscheds (cfq) run q->request_fn directly, so
 		 * rq cannot be accessed after calling
@@ -557,6 +673,7 @@ struct request *elv_next_request(request_queue_t *q)
 void elv_dequeue_request(request_queue_t *q, struct request *rq)
 {
 	BUG_ON(list_empty(&rq->queuelist));
+	BUG_ON(ELV_ON_HASH(rq));
 
 	list_del_init(&rq->queuelist);
 
diff --git a/block/ll_rw_blk.c b/block/ll_rw_blk.c
index 9b91bb70c5e..9cbf7b550c7 100644
--- a/block/ll_rw_blk.c
+++ b/block/ll_rw_blk.c
@@ -281,6 +281,7 @@ static inline void rq_init(request_queue_t *q, struct request *rq)
 {
 	INIT_LIST_HEAD(&rq->queuelist);
 	INIT_LIST_HEAD(&rq->donelist);
+	INIT_HLIST_NODE(&rq->hash);
 
 	rq->errors = 0;
 	rq->rq_status = RQ_ACTIVE;
@@ -2700,6 +2701,7 @@ void __blk_put_request(request_queue_t *q, struct request *req)
 		int priv = req->cmd_flags & REQ_ELVPRIV;
 
 		BUG_ON(!list_empty(&req->queuelist));
+		BUG_ON(!hlist_unhashed(&req->hash));
 
 		blk_free_request(q, req);
 		freed_request(q, rw, priv);