[PATCH] 1/15 elevator: move the backmerging logic into the elevator core

From: Jens Axboe
Date: Thu Jul 13 2006 - 08:45:55 EST

Right now, every IO scheduler implements its own backmerging (except for
noop, which does no merging). That results in duplicated code for
essentially the same operation, which is never a good thing. This patch
moves the backmerging out of the io schedulers and into the elevator
core. We save 1.6kb of text and as a bonus get backmerging for noop as
well. Win-win!

Signed-off-by: Jens Axboe <axboe@xxxxxxx>
---
block/as-iosched.c | 139 +------------------------------------------
block/cfq-iosched.c | 86 +--------------------------
block/deadline-iosched.c | 128 +---------------------------------------
block/elevator.c | 147 +++++++++++++++++++++++++++++++++++++++++-----
block/ll_rw_blk.c | 2 +
include/linux/blkdev.h | 17 +----
include/linux/elevator.h | 2 +
7 files changed, 146 insertions(+), 375 deletions(-)

diff --git a/block/as-iosched.c b/block/as-iosched.c
index 5da56d4..1c44ce3 100644
--- a/block/as-iosched.c
+++ b/block/as-iosched.c
@@ -14,7 +14,6 @@ #include <linux/module.h>
#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_
}

/*
- * 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(req
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
}

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 requ
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_qu
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_q
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_
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

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
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 102ebc2..6fd8af1 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -41,16 +41,6 @@ #define CFQ_QHASH_SHIFT 6
#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_
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 re

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 req
{
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_q

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, stru
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_queu
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_queu
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 c7ca9f0..b66e820 100644
--- a/block/deadline-iosched.c
+++ b/block/deadline-iosched.c
@@ -12,7 +12,6 @@ #include <linux/module.h>
#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;
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_queu
{
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(requ

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, struc
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, struc

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(requ
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
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
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
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
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,
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 bc7baee..3e40530 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -33,6 +33,7 @@ #include <linux/init.h>
#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 *

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 *
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
}
}

+ /*
+ * 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
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

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, stru
BUG_ON(!blk_fs_request(rq));
rq->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
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 61d6b3c..84c7b1c 100644
--- a/block/ll_rw_blk.c
+++ b/block/ll_rw_blk.c
@@ -281,6 +281,7 @@ static inline void rq_init(request_queue
{
INIT_LIST_HEAD(&rq->queuelist);
INIT_LIST_HEAD(&rq->donelist);
+ INIT_HLIST_NODE(&rq->hash);

rq->errors = 0;
rq->rq_status = RQ_ACTIVE;
@@ -2665,6 +2666,7 @@ void __blk_put_request(request_queue_t *
int priv = req->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);
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index aafe827..9b23cbe 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -148,6 +148,8 @@ struct request {
struct bio *bio;
struct bio *biotail;

+ struct hlist_node hash; /* merge hash */
+
void *elevator_private;
void *completion_data;

@@ -679,21 +681,6 @@ static inline void blkdev_dequeue_reques
}

/*
- * This should be in elevator.h, but that requires pulling in rq and q
- */
-static inline void elv_dispatch_add_tail(struct request_queue *q,
- struct request *rq)
-{
- if (q->last_merge == rq)
- q->last_merge = NULL;
- q->nr_sorted--;
-
- q->end_sector = rq_end_sector(rq);
- q->boundary_rq = rq;
- list_add_tail(&rq->queuelist, &q->queue_head);
-}
-
-/*
* Access functions for manipulating queue properties
*/
extern request_queue_t *blk_init_queue_node(request_fn_proc *rfn,
diff --git a/include/linux/elevator.h b/include/linux/elevator.h
index 1713ace..2c270e9 100644
--- a/include/linux/elevator.h
+++ b/include/linux/elevator.h
@@ -82,12 +82,14 @@ struct elevator_queue
struct kobject kobj;
struct elevator_type *elevator_type;
struct mutex sysfs_lock;
+ struct hlist_head *hash;
};

/*
* block elevator interface
*/
extern void elv_dispatch_sort(request_queue_t *, struct request *);
+extern void elv_dispatch_add_tail(request_queue_t *, struct request *);
extern void elv_add_request(request_queue_t *, struct request *, int, int);
extern void __elv_add_request(request_queue_t *, struct request *, int, int);
extern void elv_insert(request_queue_t *, struct request *, int);
--
1.4.1.ged0e0

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/