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Subject[PATCH v3 1/8] cfq-iosched: add symmetric reference wrappers
Date
The cfq_group and cfq_queue objects did not have symmetric
wrapper functions and many of the reference taking was
open coded. For clarity add the following wrappers:

cfq_group:
- cfq_get_group_ref()
- cfq_put_group_ref()

cfq_queue:
- cfq_get_queue_ref()
- cfq_put_queue_ref()

The use of '_ref' was done not to collide with existing
function names.

Signed-off-by: Justin TerAvest <teravest@google.com>
---
block/cfq-iosched.c | 95 +++++++++++++++++++++++++++++---------------------
1 files changed, 55 insertions(+), 40 deletions(-)
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 12e380b..74510f5 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -303,6 +303,11 @@ struct cfq_data {
struct rcu_head rcu;
};

+static void cfq_get_group_ref(struct cfq_group *cfqg);
+static void cfq_put_group_ref(struct cfq_group *cfqg);
+static void cfq_get_queue_ref(struct cfq_queue *cfqq);
+static void cfq_put_queue_ref(struct cfq_queue *cfqq);
+
static struct cfq_group *cfq_get_next_cfqg(struct cfq_data *cfqd);

static struct cfq_rb_root *service_tree_for(struct cfq_group *cfqg,
@@ -1048,7 +1053,7 @@ cfq_find_alloc_cfqg(struct cfq_data *cfqd, struct cgroup *cgroup, int create)
* elevator which will be dropped by either elevator exit
* or cgroup deletion path depending on who is exiting first.
*/
- cfqg->ref = 1;
+ cfq_get_group_ref(cfqg);

/*
* Add group onto cgroup list. It might happen that bdi->dev is
@@ -1091,24 +1096,12 @@ static struct cfq_group *cfq_get_cfqg(struct cfq_data *cfqd, int create)
return cfqg;
}

-static inline struct cfq_group *cfq_ref_get_cfqg(struct cfq_group *cfqg)
+static void cfq_get_group_ref(struct cfq_group *cfqg)
{
cfqg->ref++;
- return cfqg;
}

-static void cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group *cfqg)
-{
- /* Currently, all async queues are mapped to root group */
- if (!cfq_cfqq_sync(cfqq))
- cfqg = &cfqq->cfqd->root_group;
-
- cfqq->cfqg = cfqg;
- /* cfqq reference on cfqg */
- cfqq->cfqg->ref++;
-}
-
-static void cfq_put_cfqg(struct cfq_group *cfqg)
+static void cfq_put_group_ref(struct cfq_group *cfqg)
{
struct cfq_rb_root *st;
int i, j;
@@ -1122,6 +1115,17 @@ static void cfq_put_cfqg(struct cfq_group *cfqg)
kfree(cfqg);
}

+static void cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group *cfqg)
+{
+ /* Currently, all async queues are mapped to root group */
+ if (!cfq_cfqq_sync(cfqq))
+ cfqg = &cfqq->cfqd->root_group;
+
+ cfqq->cfqg = cfqg;
+ /* cfqq reference on cfqg */
+ cfq_get_group_ref(cfqq->cfqg);
+}
+
static void cfq_destroy_cfqg(struct cfq_data *cfqd, struct cfq_group *cfqg)
{
/* Something wrong if we are trying to remove same group twice */
@@ -1133,7 +1137,7 @@ static void cfq_destroy_cfqg(struct cfq_data *cfqd, struct cfq_group *cfqg)
* Put the reference taken at the time of creation so that when all
* queues are gone, group can be destroyed.
*/
- cfq_put_cfqg(cfqg);
+ cfq_put_group_ref(cfqg);
}

static void cfq_release_cfq_groups(struct cfq_data *cfqd)
@@ -1177,14 +1181,18 @@ void cfq_unlink_blkio_group(void *key, struct blkio_group *blkg)
}

#else /* GROUP_IOSCHED */
-static struct cfq_group *cfq_get_cfqg(struct cfq_data *cfqd, int create)
+
+static void cfq_get_group_ref(struct cfq_group *cfqg)
{
- return &cfqd->root_group;
}

-static inline struct cfq_group *cfq_ref_get_cfqg(struct cfq_group *cfqg)
+static void cfq_put_group_ref(struct cfq_group *cfqg)
{
- return cfqg;
+}
+
+static struct cfq_group *cfq_get_cfqg(struct cfq_data *cfqd, int create)
+{
+ return &cfqd->root_group;
}

static inline void
@@ -1193,7 +1201,6 @@ cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group *cfqg) {
}

static void cfq_release_cfq_groups(struct cfq_data *cfqd) {}
-static inline void cfq_put_cfqg(struct cfq_group *cfqg) {}

#endif /* GROUP_IOSCHED */

@@ -2553,6 +2560,11 @@ static int cfq_dispatch_requests(struct request_queue *q, int force)
return 1;
}

+static void cfq_get_queue_ref(struct cfq_queue *cfqq)
+{
+ cfqq->ref++;
+}
+
/*
* task holds one reference to the queue, dropped when task exits. each rq
* in-flight on this queue also holds a reference, dropped when rq is freed.
@@ -2560,7 +2572,7 @@ static int cfq_dispatch_requests(struct request_queue *q, int force)
* Each cfq queue took a reference on the parent group. Drop it now.
* queue lock must be held here.
*/
-static void cfq_put_queue(struct cfq_queue *cfqq)
+static void cfq_put_queue_ref(struct cfq_queue *cfqq)
{
struct cfq_data *cfqd = cfqq->cfqd;
struct cfq_group *cfqg;
@@ -2583,7 +2595,7 @@ static void cfq_put_queue(struct cfq_queue *cfqq)

BUG_ON(cfq_cfqq_on_rr(cfqq));
kmem_cache_free(cfq_pool, cfqq);
- cfq_put_cfqg(cfqg);
+ cfq_put_group_ref(cfqg);
}

/*
@@ -2688,7 +2700,7 @@ static void cfq_put_cooperator(struct cfq_queue *cfqq)
break;
}
next = __cfqq->new_cfqq;
- cfq_put_queue(__cfqq);
+ cfq_put_queue_ref(__cfqq);
__cfqq = next;
}
}
@@ -2702,7 +2714,7 @@ static void cfq_exit_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq)

cfq_put_cooperator(cfqq);

- cfq_put_queue(cfqq);
+ cfq_put_queue_ref(cfqq);
}

static void __cfq_exit_single_io_context(struct cfq_data *cfqd,
@@ -2844,7 +2856,7 @@ static void changed_ioprio(struct io_context *ioc, struct cfq_io_context *cic)
GFP_ATOMIC);
if (new_cfqq) {
cic->cfqq[BLK_RW_ASYNC] = new_cfqq;
- cfq_put_queue(cfqq);
+ cfq_put_queue_ref(cfqq);
}
}

@@ -2903,7 +2915,7 @@ static void changed_cgroup(struct io_context *ioc, struct cfq_io_context *cic)
*/
cfq_log_cfqq(cfqd, sync_cfqq, "changed cgroup");
cic_set_cfqq(cic, NULL, 1);
- cfq_put_queue(sync_cfqq);
+ cfq_put_queue_ref(sync_cfqq);
}

spin_unlock_irqrestore(q->queue_lock, flags);
@@ -3004,11 +3016,11 @@ cfq_get_queue(struct cfq_data *cfqd, bool is_sync, struct io_context *ioc,
* pin the queue now that it's allocated, scheduler exit will prune it
*/
if (!is_sync && !(*async_cfqq)) {
- cfqq->ref++;
+ cfq_get_queue_ref(cfqq);
*async_cfqq = cfqq;
}

- cfqq->ref++;
+ cfq_get_queue_ref(cfqq);
return cfqq;
}

@@ -3633,10 +3645,10 @@ static void cfq_put_request(struct request *rq)
rq->elevator_private[1] = NULL;

/* Put down rq reference on cfqg */
- cfq_put_cfqg(RQ_CFQG(rq));
+ cfq_put_group_ref(RQ_CFQG(rq));
rq->elevator_private[2] = NULL;

- cfq_put_queue(cfqq);
+ cfq_put_queue_ref(cfqq);
}
}

@@ -3647,7 +3659,7 @@ cfq_merge_cfqqs(struct cfq_data *cfqd, struct cfq_io_context *cic,
cfq_log_cfqq(cfqd, cfqq, "merging with queue %p", cfqq->new_cfqq);
cic_set_cfqq(cic, cfqq->new_cfqq, 1);
cfq_mark_cfqq_coop(cfqq->new_cfqq);
- cfq_put_queue(cfqq);
+ cfq_put_queue_ref(cfqq);
return cic_to_cfqq(cic, 1);
}

@@ -3669,7 +3681,7 @@ split_cfqq(struct cfq_io_context *cic, struct cfq_queue *cfqq)

cfq_put_cooperator(cfqq);

- cfq_put_queue(cfqq);
+ cfq_put_queue_ref(cfqq);
return NULL;
}
/*
@@ -3722,10 +3734,12 @@ new_queue:

cfqq->allocated[rw]++;

- cfqq->ref++;
+ cfq_get_queue_ref(cfqq);
rq->elevator_private[0] = cic;
rq->elevator_private[1] = cfqq;
- rq->elevator_private[2] = cfq_ref_get_cfqg(cfqq->cfqg);
+
+ cfq_get_group_ref(cfqq->cfqg);
+ rq->elevator_private[2] = cfqq->cfqg;
spin_unlock_irqrestore(q->queue_lock, flags);
return 0;

@@ -3818,13 +3832,13 @@ static void cfq_put_async_queues(struct cfq_data *cfqd)

for (i = 0; i < IOPRIO_BE_NR; i++) {
if (cfqd->async_cfqq[0][i])
- cfq_put_queue(cfqd->async_cfqq[0][i]);
+ cfq_put_queue_ref(cfqd->async_cfqq[0][i]);
if (cfqd->async_cfqq[1][i])
- cfq_put_queue(cfqd->async_cfqq[1][i]);
+ cfq_put_queue_ref(cfqd->async_cfqq[1][i]);
}

if (cfqd->async_idle_cfqq)
- cfq_put_queue(cfqd->async_idle_cfqq);
+ cfq_put_queue_ref(cfqd->async_idle_cfqq);
}

static void cfq_cfqd_free(struct rcu_head *head)
@@ -3922,9 +3936,10 @@ static void *cfq_init_queue(struct request_queue *q)
#ifdef CONFIG_CFQ_GROUP_IOSCHED
/*
* Take a reference to root group which we never drop. This is just
- * to make sure that cfq_put_cfqg() does not try to kfree root group
+ * to make sure that cfq_put_group_ref() does not try to kfree
+ * root group
*/
- cfqg->ref = 1;
+ cfq_get_group_ref(cfqg);
rcu_read_lock();
cfq_blkiocg_add_blkio_group(&blkio_root_cgroup, &cfqg->blkg,
(void *)cfqd, 0);
--
1.7.3.1


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