[PATCH] iosched: use hlist for request hashtable

From: Akinobu Mita
Date: Mon Apr 24 2006 - 04:38:02 EST

Use hlist instead of list_head for request hashtable in deadline-iosched
and as-iosched. It also can remove the flag to know hashed or unhashed.

Signed-off-by: Akinobu Mita <mita@xxxxxxxxxxxxxxxx>
CC: Jens Axboe <axboe@xxxxxxx>

block/as-iosched.c | 45 +++++++++++++++++++--------------------------
block/deadline-iosched.c | 39 ++++++++++++++++-----------------------
2 files changed, 35 insertions(+), 49 deletions(-)

Index: 2.6-git/block/deadline-iosched.c
===================================================================
--- 2.6-git.orig/block/deadline-iosched.c
+++ 2.6-git/block/deadline-iosched.c
@@ -30,8 +30,7 @@ static const int deadline_hash_shift = 5
#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 list_entry_hash(ptr) list_entry((ptr), struct deadline_rq, hash)
-#define ON_HASH(drq) (drq)->on_hash
+#define ON_HASH(drq) (!hlist_unhashed(&(drq)->hash))

struct deadline_data {
/*
@@ -48,7 +47,7 @@ struct deadline_data {
* next in sort order. read, write or both are NULL
*/
struct deadline_rq *next_drq[2];
- struct list_head *hash; /* request hash */
+ 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 */
@@ -79,8 +78,7 @@ struct deadline_rq {
/*
* request hash, key is the ending offset (for back merge lookup)
*/
- struct list_head hash;
- char on_hash;
+ struct hlist_node hash;

/*
* expire fifo
@@ -100,8 +98,7 @@ static kmem_cache_t *drq_pool;
*/
static inline void __deadline_del_drq_hash(struct deadline_rq *drq)
{
- drq->on_hash = 0;
- list_del_init(&drq->hash);
+ hlist_del_init(&drq->hash);
}

static inline void deadline_del_drq_hash(struct deadline_rq *drq)
@@ -117,8 +114,7 @@ deadline_add_drq_hash(struct deadline_da

BUG_ON(ON_HASH(drq));

- drq->on_hash = 1;
- list_add(&drq->hash, &dd->hash[DL_HASH_FN(rq_hash_key(rq))]);
+ hlist_add_head(&drq->hash, &dd->hash[DL_HASH_FN(rq_hash_key(rq))]);
}

/*
@@ -128,26 +124,24 @@ static inline void
deadline_hot_drq_hash(struct deadline_data *dd, struct deadline_rq *drq)
{
struct request *rq = drq->request;
- struct list_head *head = &dd->hash[DL_HASH_FN(rq_hash_key(rq))];
+ struct hlist_head *head = &dd->hash[DL_HASH_FN(rq_hash_key(rq))];

- if (ON_HASH(drq) && drq->hash.prev != head) {
- list_del(&drq->hash);
- list_add(&drq->hash, head);
+ 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 list_head *hash_list = &dd->hash[DL_HASH_FN(offset)];
- struct list_head *entry, *next = hash_list->next;
+ struct hlist_head *hash_list = &dd->hash[DL_HASH_FN(offset)];
+ struct hlist_node *entry, *next;
+ struct deadline_rq *drq;

- while ((entry = next) != hash_list) {
- struct deadline_rq *drq = list_entry_hash(entry);
+ hlist_for_each_entry_safe(drq, entry, next, hash_list, hash) {
struct request *__rq = drq->request;

- next = entry->next;
-
BUG_ON(!ON_HASH(drq));

if (!rq_mergeable(__rq)) {
@@ -626,7 +620,7 @@ static int deadline_init_queue(request_q
return -ENOMEM;
memset(dd, 0, sizeof(*dd));

- dd->hash = kmalloc_node(sizeof(struct list_head)*DL_HASH_ENTRIES,
+ dd->hash = kmalloc_node(sizeof(struct hlist_head)*DL_HASH_ENTRIES,
GFP_KERNEL, q->node);
if (!dd->hash) {
kfree(dd);
@@ -642,7 +636,7 @@ static int deadline_init_queue(request_q
}

for (i = 0; i < DL_HASH_ENTRIES; i++)
- INIT_LIST_HEAD(&dd->hash[i]);
+ INIT_HLIST_HEAD(&dd->hash[i]);

INIT_LIST_HEAD(&dd->fifo_list[READ]);
INIT_LIST_HEAD(&dd->fifo_list[WRITE]);
@@ -679,8 +673,7 @@ deadline_set_request(request_queue_t *q,
RB_CLEAR(&drq->rb_node);
drq->request = rq;

- INIT_LIST_HEAD(&drq->hash);
- drq->on_hash = 0;
+ INIT_HLIST_NODE(&drq->hash);

INIT_LIST_HEAD(&drq->fifo);

Index: 2.6-git/block/as-iosched.c
===================================================================
--- 2.6-git.orig/block/as-iosched.c
+++ 2.6-git/block/as-iosched.c
@@ -96,7 +96,7 @@ 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 list_head *hash; /* request hash */
+ struct hlist_head *hash; /* request hash */

unsigned long exit_prob; /* probability a task will exit while
being waited on */
@@ -165,8 +165,7 @@ struct as_rq {
/*
* request hash, key is the ending offset (for back merge lookup)
*/
- struct list_head hash;
- unsigned int on_hash;
+ struct hlist_node hash;

/*
* expire fifo
@@ -282,17 +281,15 @@ static const int as_hash_shift = 6;
#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)
-#define list_entry_hash(ptr) list_entry((ptr), struct as_rq, hash)

static inline void __as_del_arq_hash(struct as_rq *arq)
{
- arq->on_hash = 0;
- list_del_init(&arq->hash);
+ hlist_del_init(&arq->hash);
}

static inline void as_del_arq_hash(struct as_rq *arq)
{
- if (arq->on_hash)
+ if (!hlist_unhashed(&arq->hash))
__as_del_arq_hash(arq);
}

@@ -300,10 +297,9 @@ static void as_add_arq_hash(struct as_da
{
struct request *rq = arq->request;

- BUG_ON(arq->on_hash);
+ BUG_ON(!hlist_unhashed(&arq->hash));

- arq->on_hash = 1;
- list_add(&arq->hash, &ad->hash[AS_HASH_FN(rq_hash_key(rq))]);
+ hlist_add_head(&arq->hash, &ad->hash[AS_HASH_FN(rq_hash_key(rq))]);
}

/*
@@ -312,31 +308,29 @@ static void as_add_arq_hash(struct as_da
static inline void as_hot_arq_hash(struct as_data *ad, struct as_rq *arq)
{
struct request *rq = arq->request;
- struct list_head *head = &ad->hash[AS_HASH_FN(rq_hash_key(rq))];
+ struct hlist_head *head = &ad->hash[AS_HASH_FN(rq_hash_key(rq))];

- if (!arq->on_hash) {
+ if (hlist_unhashed(&arq->hash)) {
WARN_ON(1);
return;
}

- if (arq->hash.prev != head) {
- list_del(&arq->hash);
- list_add(&arq->hash, head);
+ 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 list_head *hash_list = &ad->hash[AS_HASH_FN(offset)];
- struct list_head *entry, *next = hash_list->next;
+ struct hlist_head *hash_list = &ad->hash[AS_HASH_FN(offset)];
+ struct hlist_node *entry, *next;
+ struct as_rq *arq;

- while ((entry = next) != hash_list) {
- struct as_rq *arq = list_entry_hash(entry);
+ hlist_for_each_entry_safe(arq, entry, next, hash_list, hash) {
struct request *__rq = arq->request;

- next = entry->next;
-
- BUG_ON(!arq->on_hash);
+ BUG_ON(hlist_unhashed(&arq->hash));

if (!rq_mergeable(__rq)) {
as_del_arq_hash(arq);
@@ -1602,8 +1596,7 @@ static int as_set_request(request_queue_
arq->request = rq;
arq->state = AS_RQ_PRESCHED;
arq->io_context = NULL;
- INIT_LIST_HEAD(&arq->hash);
- arq->on_hash = 0;
+ INIT_HLIST_NODE(&arq->hash);
INIT_LIST_HEAD(&arq->fifo);
rq->elevator_private = arq;
return 0;
@@ -1663,7 +1656,7 @@ static int as_init_queue(request_queue_t

ad->q = q; /* Identify what queue the data belongs to */

- ad->hash = kmalloc_node(sizeof(struct list_head)*AS_HASH_ENTRIES,
+ ad->hash = kmalloc_node(sizeof(struct hlist_head)*AS_HASH_ENTRIES,
GFP_KERNEL, q->node);
if (!ad->hash) {
kfree(ad);
@@ -1685,7 +1678,7 @@ static int as_init_queue(request_queue_t
INIT_WORK(&ad->antic_work, as_work_handler, q);

for (i = 0; i < AS_HASH_ENTRIES; i++)
- INIT_LIST_HEAD(&ad->hash[i]);
+ INIT_HLIST_HEAD(&ad->hash[i]);

INIT_LIST_HEAD(&ad->fifo_list[REQ_SYNC]);
INIT_LIST_HEAD(&ad->fifo_list[REQ_ASYNC]);
-
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