[PATCH 05/10] block, cfq: move cfqd->icq_list to request_queue and add request->elv.icq

From: Tejun Heo
Date: Sat Oct 29 2011 - 19:51:31 EST


Most of icq management is about to be moved out of cfq into blk-ioc.
This patch prepares for it.

* Move cfqd->icq_list to request_queue->icq_list

* Make request explicitly point to icq instead of through elevator
private data. ->elevator_private[3] is replaced with sub struct elv
which contains icq pointer and priv[2]. cfq is updated accordingly.

* Meaningless clearing of ->elevator_private[0] removed from
elv_set_request(). At that point in code, the field was guaranteed
to be %NULL anyway.

This patch doesn't introduce any functional change.

Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
Cc: Jens Axboe <axboe@xxxxxxxxx>
---
block/blk-core.c | 1 +
block/cfq-iosched.c | 28 +++++++++++-----------------
block/elevator.c | 2 --
include/linux/blkdev.h | 10 ++++++++--
4 files changed, 20 insertions(+), 21 deletions(-)

diff --git a/block/blk-core.c b/block/blk-core.c
index 74b44ab..5315f09 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -492,6 +492,7 @@ struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id)
laptop_mode_timer_fn, (unsigned long) q);
setup_timer(&q->timeout, blk_rq_timed_out_timer, (unsigned long) q);
INIT_LIST_HEAD(&q->timeout_list);
+ INIT_LIST_HEAD(&q->icq_list);
INIT_LIST_HEAD(&q->flush_queue[0]);
INIT_LIST_HEAD(&q->flush_queue[1]);
INIT_LIST_HEAD(&q->flush_data_in_flight);
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index d2f16fc..9bc5ecc 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -54,9 +54,9 @@ static const int cfq_hist_divisor = 4;
#define CFQQ_SECT_THR_NONROT (sector_t)(2 * 32)
#define CFQQ_SEEKY(cfqq) (hweight32(cfqq->seek_history) > 32/8)

-#define RQ_CIC(rq) icq_to_cic((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])
+#define RQ_CIC(rq) icq_to_cic((rq)->elv.icq)
+#define RQ_CFQQ(rq) (struct cfq_queue *) ((rq)->elv.priv[0])
+#define RQ_CFQG(rq) (struct cfq_group *) ((rq)->elv.priv[1])

static struct kmem_cache *cfq_pool;
static struct kmem_cache *cfq_icq_pool;
@@ -297,8 +297,6 @@ struct cfq_data {
unsigned int cfq_group_idle;
unsigned int cfq_latency;

- struct list_head icq_list;
-
/*
* Fallback dummy cfqq for extreme OOM conditions
*/
@@ -3053,7 +3051,7 @@ static int cfq_create_cic(struct cfq_data *cfqd, gfp_t gfp_mask)
ret = radix_tree_insert(&ioc->icq_tree, q->id, icq);
if (likely(!ret)) {
hlist_add_head(&icq->ioc_node, &ioc->icq_list);
- list_add(&icq->q_node, &cfqd->icq_list);
+ list_add(&icq->q_node, &q->icq_list);
icq = NULL;
} else if (ret == -EEXIST) {
/* someone else already did it */
@@ -3605,12 +3603,10 @@ static void cfq_put_request(struct request *rq)

put_io_context(RQ_CIC(rq)->icq.ioc, cfqq->cfqd->queue);

- rq->elevator_private[0] = NULL;
- rq->elevator_private[1] = NULL;
-
/* Put down rq reference on cfqg */
cfq_put_cfqg(RQ_CFQG(rq));
- rq->elevator_private[2] = NULL;
+ rq->elv.priv[0] = NULL;
+ rq->elv.priv[1] = NULL;

cfq_put_queue(cfqq);
}
@@ -3696,9 +3692,9 @@ new_queue:
cfqq->allocated[rw]++;

cfqq->ref++;
- rq->elevator_private[0] = &cic->icq;
- rq->elevator_private[1] = cfqq;
- rq->elevator_private[2] = cfq_ref_get_cfqg(cfqq->cfqg);
+ rq->elv.icq = &cic->icq;
+ rq->elv.priv[0] = cfqq;
+ rq->elv.priv[1] = cfq_ref_get_cfqg(cfqq->cfqg);
spin_unlock_irq(q->queue_lock);
return 0;

@@ -3810,8 +3806,8 @@ static void cfq_exit_queue(struct elevator_queue *e)
if (cfqd->active_queue)
__cfq_slice_expired(cfqd, cfqd->active_queue, 0);

- while (!list_empty(&cfqd->icq_list)) {
- struct io_cq *icq = list_entry(cfqd->icq_list.next,
+ while (!list_empty(&q->icq_list)) {
+ struct io_cq *icq = list_entry(q->icq_list.next,
struct io_cq, q_node);
struct io_context *ioc = icq->ioc;

@@ -3922,8 +3918,6 @@ static void *cfq_init_queue(struct request_queue *q)
cfqd->oom_cfqq.ref++;
cfq_link_cfqq_cfqg(&cfqd->oom_cfqq, &cfqd->root_group);

- INIT_LIST_HEAD(&cfqd->icq_list);
-
cfqd->queue = q;

init_timer(&cfqd->idle_slice_timer);
diff --git a/block/elevator.c b/block/elevator.c
index 31ffe76..c5c6214 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -745,8 +745,6 @@ int elv_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask)

if (e->type->ops.elevator_set_req_fn)
return e->type->ops.elevator_set_req_fn(q, rq, gfp_mask);
-
- rq->elevator_private[0] = NULL;
return 0;
}

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index e4c10a0..6c7e09c 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -111,10 +111,14 @@ struct request {
* Three pointers are available for the IO schedulers, if they need
* 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.
+ * space with the elevator data.
*/
union {
- void *elevator_private[3];
+ struct {
+ struct io_cq *icq;
+ void *priv[2];
+ } elv;
+
struct {
unsigned int seq;
struct list_head list;
@@ -357,6 +361,8 @@ struct request_queue {
struct timer_list timeout;
struct list_head timeout_list;

+ struct list_head icq_list;
+
struct queue_limits limits;

/*
--
1.7.3.1

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