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[PATCH] elevator: abstract out the rbtree sort handling
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The rbtree sort/lookup/reposition logic is mostly duplicated in
cfq/deadline/as, so move it to the elevator core. The io schedulers
still provide the actual rb root, as we don't want to impose any sort
of specific handling on the schedulers.

Introduce the helpers and rb_node in struct request to help migrate the
IO schedulers.

Signed-off-by: Jens Axboe <[email protected]>
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Jens Axboe authored and Jens Axboe committed Sep 30, 2006
1 parent 10fd48f commit 2e662b6
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Showing 4 changed files with 130 additions and 19 deletions.
123 changes: 109 additions & 14 deletions block/elevator.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -239,6 +239,8 @@ int elevator_init(request_queue_t *q, char *name)
return ret;
}

EXPORT_SYMBOL(elevator_init);

void elevator_exit(elevator_t *e)
{
mutex_lock(&e->sysfs_lock);
Expand All @@ -250,6 +252,8 @@ void elevator_exit(elevator_t *e)
kobject_put(&e->kobj);
}

EXPORT_SYMBOL(elevator_exit);

static inline void __elv_rqhash_del(struct request *rq)
{
hlist_del_init(&rq->hash);
Expand Down Expand Up @@ -297,10 +301,69 @@ static struct request *elv_rqhash_find(request_queue_t *q, sector_t offset)
return NULL;
}

/*
* RB-tree support functions for inserting/lookup/removal of requests
* in a sorted RB tree.
*/
struct request *elv_rb_add(struct rb_root *root, struct request *rq)
{
struct rb_node **p = &root->rb_node;
struct rb_node *parent = NULL;
struct request *__rq;

while (*p) {
parent = *p;
__rq = rb_entry(parent, struct request, rb_node);

if (rq->sector < __rq->sector)
p = &(*p)->rb_left;
else if (rq->sector > __rq->sector)
p = &(*p)->rb_right;
else
return __rq;
}

rb_link_node(&rq->rb_node, parent, p);
rb_insert_color(&rq->rb_node, root);
return NULL;
}

EXPORT_SYMBOL(elv_rb_add);

void elv_rb_del(struct rb_root *root, struct request *rq)
{
BUG_ON(RB_EMPTY_NODE(&rq->rb_node));
rb_erase(&rq->rb_node, root);
RB_CLEAR_NODE(&rq->rb_node);
}

EXPORT_SYMBOL(elv_rb_del);

struct request *elv_rb_find(struct rb_root *root, sector_t sector)
{
struct rb_node *n = root->rb_node;
struct request *rq;

while (n) {
rq = rb_entry(n, struct request, rb_node);

if (sector < rq->sector)
n = n->rb_left;
else if (sector > rq->sector)
n = n->rb_right;
else
return rq;
}

return NULL;
}

EXPORT_SYMBOL(elv_rb_find);

/*
* 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
* appended to the dispatch queue. To be used by specific elevators.
* entry. rq is sort insted into the dispatch queue. To be used by
* specific elevators.
*/
void elv_dispatch_sort(request_queue_t *q, struct request *rq)
{
Expand Down Expand Up @@ -335,8 +398,12 @@ void elv_dispatch_sort(request_queue_t *q, struct request *rq)
list_add(&rq->queuelist, entry);
}

EXPORT_SYMBOL(elv_dispatch_sort);

/*
* This should be in elevator.h, but that requires pulling in rq and q
* Insert rq into dispatch queue of q. Queue lock must be held on
* entry. rq is added to the back of the dispatch queue. To be used by
* specific elevators.
*/
void elv_dispatch_add_tail(struct request_queue *q, struct request *rq)
{
Expand All @@ -352,6 +419,8 @@ void elv_dispatch_add_tail(struct request_queue *q, struct request *rq)
list_add_tail(&rq->queuelist, &q->queue_head);
}

EXPORT_SYMBOL(elv_dispatch_add_tail);

int elv_merge(request_queue_t *q, struct request **req, struct bio *bio)
{
elevator_t *e = q->elevator;
Expand Down Expand Up @@ -384,14 +453,15 @@ int elv_merge(request_queue_t *q, struct request **req, struct bio *bio)
return ELEVATOR_NO_MERGE;
}

void elv_merged_request(request_queue_t *q, struct request *rq)
void elv_merged_request(request_queue_t *q, struct request *rq, int type)
{
elevator_t *e = q->elevator;

if (e->ops->elevator_merged_fn)
e->ops->elevator_merged_fn(q, rq);
e->ops->elevator_merged_fn(q, rq, type);

elv_rqhash_reposition(q, rq);
if (type == ELEVATOR_BACK_MERGE)
elv_rqhash_reposition(q, rq);

q->last_merge = rq;
}
Expand Down Expand Up @@ -577,6 +647,8 @@ void __elv_add_request(request_queue_t *q, struct request *rq, int where,
elv_insert(q, rq, where);
}

EXPORT_SYMBOL(__elv_add_request);

void elv_add_request(request_queue_t *q, struct request *rq, int where,
int plug)
{
Expand All @@ -587,6 +659,8 @@ void elv_add_request(request_queue_t *q, struct request *rq, int where,
spin_unlock_irqrestore(q->queue_lock, flags);
}

EXPORT_SYMBOL(elv_add_request);

static inline struct request *__elv_next_request(request_queue_t *q)
{
struct request *rq;
Expand Down Expand Up @@ -670,6 +744,8 @@ struct request *elv_next_request(request_queue_t *q)
return rq;
}

EXPORT_SYMBOL(elv_next_request);

void elv_dequeue_request(request_queue_t *q, struct request *rq)
{
BUG_ON(list_empty(&rq->queuelist));
Expand All @@ -686,6 +762,8 @@ void elv_dequeue_request(request_queue_t *q, struct request *rq)
q->in_flight++;
}

EXPORT_SYMBOL(elv_dequeue_request);

int elv_queue_empty(request_queue_t *q)
{
elevator_t *e = q->elevator;
Expand All @@ -699,6 +777,8 @@ int elv_queue_empty(request_queue_t *q)
return 1;
}

EXPORT_SYMBOL(elv_queue_empty);

struct request *elv_latter_request(request_queue_t *q, struct request *rq)
{
elevator_t *e = q->elevator;
Expand Down Expand Up @@ -1025,11 +1105,26 @@ ssize_t elv_iosched_show(request_queue_t *q, char *name)
return len;
}

EXPORT_SYMBOL(elv_dispatch_sort);
EXPORT_SYMBOL(elv_add_request);
EXPORT_SYMBOL(__elv_add_request);
EXPORT_SYMBOL(elv_next_request);
EXPORT_SYMBOL(elv_dequeue_request);
EXPORT_SYMBOL(elv_queue_empty);
EXPORT_SYMBOL(elevator_exit);
EXPORT_SYMBOL(elevator_init);
struct request *elv_rb_former_request(request_queue_t *q, struct request *rq)
{
struct rb_node *rbprev = rb_prev(&rq->rb_node);

if (rbprev)
return rb_entry_rq(rbprev);

return NULL;
}

EXPORT_SYMBOL(elv_rb_former_request);

struct request *elv_rb_latter_request(request_queue_t *q, struct request *rq)
{
struct rb_node *rbnext = rb_next(&rq->rb_node);

if (rbnext)
return rb_entry_rq(rbnext);

return NULL;
}

EXPORT_SYMBOL(elv_rb_latter_request);
7 changes: 4 additions & 3 deletions block/ll_rw_blk.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -281,11 +281,12 @@ 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;
rq->bio = rq->biotail = NULL;
INIT_HLIST_NODE(&rq->hash);
RB_CLEAR_NODE(&rq->rb_node);
rq->ioprio = 0;
rq->buffer = NULL;
rq->ref_count = 1;
Expand Down Expand Up @@ -2943,7 +2944,7 @@ static int __make_request(request_queue_t *q, struct bio *bio)
req->ioprio = ioprio_best(req->ioprio, prio);
drive_stat_acct(req, nr_sectors, 0);
if (!attempt_back_merge(q, req))
elv_merged_request(q, req);
elv_merged_request(q, req, el_ret);
goto out;

case ELEVATOR_FRONT_MERGE:
Expand All @@ -2970,7 +2971,7 @@ static int __make_request(request_queue_t *q, struct bio *bio)
req->ioprio = ioprio_best(req->ioprio, prio);
drive_stat_acct(req, nr_sectors, 0);
if (!attempt_front_merge(q, req))
elv_merged_request(q, req);
elv_merged_request(q, req, el_ret);
goto out;

/* ELV_NO_MERGE: elevator says don't/can't merge. */
Expand Down
1 change: 1 addition & 0 deletions include/linux/blkdev.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -230,6 +230,7 @@ struct request {
struct bio *biotail;

struct hlist_node hash; /* merge hash */
struct rb_node rb_node; /* sort/lookup */

void *elevator_private;
void *completion_data;
Expand Down
18 changes: 16 additions & 2 deletions include/linux/elevator.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -6,7 +6,7 @@ typedef int (elevator_merge_fn) (request_queue_t *, struct request **,

typedef void (elevator_merge_req_fn) (request_queue_t *, struct request *, struct request *);

typedef void (elevator_merged_fn) (request_queue_t *, struct request *);
typedef void (elevator_merged_fn) (request_queue_t *, struct request *, int);

typedef int (elevator_dispatch_fn) (request_queue_t *, int);

Expand Down Expand Up @@ -96,7 +96,7 @@ extern void elv_insert(request_queue_t *, struct request *, int);
extern int elv_merge(request_queue_t *, struct request **, struct bio *);
extern void elv_merge_requests(request_queue_t *, struct request *,
struct request *);
extern void elv_merged_request(request_queue_t *, struct request *);
extern void elv_merged_request(request_queue_t *, struct request *, int);
extern void elv_dequeue_request(request_queue_t *, struct request *);
extern void elv_requeue_request(request_queue_t *, struct request *);
extern int elv_queue_empty(request_queue_t *);
Expand Down Expand Up @@ -126,6 +126,19 @@ extern int elevator_init(request_queue_t *, char *);
extern void elevator_exit(elevator_t *);
extern int elv_rq_merge_ok(struct request *, struct bio *);

/*
* Helper functions.
*/
extern struct request *elv_rb_former_request(request_queue_t *, struct request *);
extern struct request *elv_rb_latter_request(request_queue_t *, struct request *);

/*
* rb support functions.
*/
extern struct request *elv_rb_add(struct rb_root *, struct request *);
extern void elv_rb_del(struct rb_root *, struct request *);
extern struct request *elv_rb_find(struct rb_root *, sector_t);

/*
* Return values from elevator merger
*/
Expand All @@ -151,5 +164,6 @@ enum {
};

#define rq_end_sector(rq) ((rq)->sector + (rq)->nr_sectors)
#define rb_entry_rq(node) rb_entry((node), struct request, rb_node)

#endif

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