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block: share request flush fields with elevator_private

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Flush requests are never put on the IO scheduler.  Convert request
structure's elevator_private* into an array and have the flush fields
share a union with it.

Reclaim the space lost in 'struct request' by moving 'completion_data'
back in the union with 'rb_node'.

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
This commit is contained in:
Mike Snitzer 2011-02-11 11:08:00 +01:00 committed by Jens Axboe
parent 9d5a4e946c
commit c186794dbb
3 changed files with 22 additions and 21 deletions
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18
block/cfq-iosched.c
View File

@ -54,9 +54,9 @@ static const int cfq_hist_divisor = 4;
#define CFQQ_SEEKY(cfqq) (hweight32(cfqq->seek_history) > 32/8)
#define RQ_CIC(rq) \
((struct cfq_io_context *) (rq)->elevator_private)
#define RQ_CFQQ(rq) (struct cfq_queue *) ((rq)->elevator_private2)
#define RQ_CFQG(rq) (struct cfq_group *) ((rq)->elevator_private3)
((struct cfq_io_context *) (rq)->elevator_private[0])
#define RQ_CFQQ(rq) (struct cfq_queue *) ((rq)->elevator_private[1])
#define RQ_CFQG(rq) (struct cfq_group *) ((rq)->elevator_private[2])
static struct kmem_cache *cfq_pool;
static struct kmem_cache *cfq_ioc_pool;
@ -3589,12 +3589,12 @@ static void cfq_put_request(struct request *rq)
put_io_context(RQ_CIC(rq)->ioc);
rq->elevator_private = NULL;
rq->elevator_private2 = NULL;
rq->elevator_private[0] = NULL;
rq->elevator_private[1] = NULL;
/* Put down rq reference on cfqg */
cfq_put_cfqg(RQ_CFQG(rq));
rq->elevator_private3 = NULL;
rq->elevator_private[2] = NULL;
cfq_put_queue(cfqq);
}
@ -3685,9 +3685,9 @@ new_queue:
spin_unlock_irqrestore(q->queue_lock, flags);
rq->elevator_private = cic;
rq->elevator_private2 = cfqq;
rq->elevator_private3 = cfq_ref_get_cfqg(cfqq->cfqg);
rq->elevator_private[0] = cic;
rq->elevator_private[1] = cfqq;
rq->elevator_private[2] = cfq_ref_get_cfqg(cfqq->cfqg);
return 0;
queue_fail:

2
block/elevator.c
View File

@ -764,7 +764,7 @@ int elv_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask)
if (e->ops->elevator_set_req_fn)
return e->ops->elevator_set_req_fn(q, rq, gfp_mask);
rq->elevator_private = NULL;
rq->elevator_private[0] = NULL;
return 0;
}

23
include/linux/blkdev.h
View File

@ -99,25 +99,26 @@ struct request {
/*
* The rb_node is only used inside the io scheduler, requests
* are pruned when moved to the dispatch queue. So let the
* flush fields share space with the rb_node.
* completion_data share space with the rb_node.
*/
union {
struct rb_node rb_node; /* sort/lookup */
struct {
unsigned int seq;
struct list_head list;
} flush;
void *completion_data;
};
void *completion_data;
/*
* Three pointers are available for the IO schedulers, if they need
* more they have to dynamically allocate it.
* more they have to dynamically allocate it. Flush requests are
* never put on the IO scheduler. So let the flush fields share
* space with the three elevator_private pointers.
*/
void *elevator_private;
void *elevator_private2;
void *elevator_private3;
union {
void *elevator_private[3];
struct {
unsigned int seq;
struct list_head list;
} flush;
};
struct gendisk *rq_disk;
unsigned long start_time;