[PATCH 08/12] blkcg: use the usual get blkg path for root blkio_group
From: Tejun Heo
Date: Wed Jan 18 2012 - 20:13:14 EST
For root blkg, blk_throtl_init() was using throtl_alloc_tg()
explicitly and cfq_init_queue() was manually initializing embedded
cfqd->root_group, adding unnecessarily different code paths to blkg
handling.
Make both use the usual blkio_group get functions - throtl_get_tg()
and cfq_get_cfqg() - for the root blkio_group too. Note that
blk_throtl_init() callsite is pushed downwards in
blk_alloc_queue_node() so that @q is sufficiently initialized for
throtl_get_tg().
This simplifies root blkg handling noticeably for cfq and will allow
further modularization of blkcg API.
Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
Cc: Vivek Goyal <vgoyal@xxxxxxxxxx>
---
block/blk-core.c | 6 ++--
block/blk-throttle.c | 18 +++++++-------
block/cfq-iosched.c | 64 ++++++++++++++++---------------------------------
3 files changed, 33 insertions(+), 55 deletions(-)
diff --git a/block/blk-core.c b/block/blk-core.c
index e6c05a9..e2a4656a 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -498,9 +498,6 @@ struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id)
if (err)
goto fail_id;
- if (blk_throtl_init(q))
- goto fail_id;
-
setup_timer(&q->backing_dev_info.laptop_mode_wb_timer,
laptop_mode_timer_fn, (unsigned long) q);
setup_timer(&q->timeout, blk_rq_timed_out_timer, (unsigned long) q);
@@ -522,6 +519,9 @@ struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id)
*/
q->queue_lock = &q->__queue_lock;
+ if (blk_throtl_init(q))
+ goto fail_id;
+
return q;
fail_id:
diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 8314da4..cd3eb6a 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -1229,7 +1229,6 @@ void blk_throtl_drain(struct request_queue *q)
int blk_throtl_init(struct request_queue *q)
{
struct throtl_data *td;
- struct throtl_grp *tg;
td = kzalloc_node(sizeof(*td), GFP_KERNEL, q->node);
if (!td)
@@ -1242,19 +1241,20 @@ int blk_throtl_init(struct request_queue *q)
/* alloc and Init root group. */
td->queue = q;
- tg = throtl_alloc_tg(td);
- if (!tg) {
- kfree(td);
- return -ENOMEM;
- }
+ rcu_read_lock();
+ spin_lock_irq(q->queue_lock);
- td->root_tg = tg;
+ td->root_tg = throtl_get_tg(td, &blkio_root_cgroup);
- rcu_read_lock();
- throtl_init_add_tg_lists(td, tg, &blkio_root_cgroup);
+ spin_unlock_irq(q->queue_lock);
rcu_read_unlock();
+ if (!td->root_tg) {
+ kfree(td);
+ return -ENOMEM;
+ }
+
/* Attach throtl data to request queue */
q->td = td;
return 0;
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 511c0f1..4b09ba0 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -229,7 +229,7 @@ struct cfq_data {
struct request_queue *queue;
/* Root service tree for cfq_groups */
struct cfq_rb_root grp_service_tree;
- struct cfq_group root_group;
+ struct cfq_group *root_group;
/*
* The priority currently being served
@@ -1106,7 +1106,7 @@ cfq_find_cfqg(struct cfq_data *cfqd, struct blkio_cgroup *blkcg)
* Avoid lookup in this case
*/
if (blkcg == &blkio_root_cgroup)
- cfqg = &cfqd->root_group;
+ cfqg = cfqd->root_group;
else
cfqg = cfqg_of_blkg(blkiocg_lookup_group(blkcg, cfqd->queue,
BLKIO_POLICY_PROP));
@@ -1166,7 +1166,7 @@ static struct cfq_group *cfq_get_cfqg(struct cfq_data *cfqd,
}
if (!cfqg)
- cfqg = &cfqd->root_group;
+ cfqg = cfqd->root_group;
cfq_init_add_cfqg_lists(cfqd, cfqg, blkcg);
return cfqg;
@@ -1182,7 +1182,7 @@ 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;
+ cfqg = cfqq->cfqd->root_group;
cfqq->cfqg = cfqg;
/* cfqq reference on cfqg */
@@ -3660,62 +3660,40 @@ static void cfq_exit_queue(struct elevator_queue *e)
if (wait)
synchronize_rcu();
-#ifdef CONFIG_CFQ_GROUP_IOSCHED
- /* Free up per cpu stats for root group */
- free_percpu(cfqd->root_group.blkg.stats_cpu);
-#endif
kfree(cfqd);
}
static int cfq_init_queue(struct request_queue *q)
{
struct cfq_data *cfqd;
- int i, j;
- struct cfq_group *cfqg;
- struct cfq_rb_root *st;
+ int i;
cfqd = kmalloc_node(sizeof(*cfqd), GFP_KERNEL | __GFP_ZERO, q->node);
if (!cfqd)
return -ENOMEM;
+ cfqd->queue = q;
+ q->elevator->elevator_data = cfqd;
+
/* Init root service tree */
cfqd->grp_service_tree = CFQ_RB_ROOT;
- /* Init root group */
- cfqg = &cfqd->root_group;
- for_each_cfqg_st(cfqg, i, j, st)
- *st = CFQ_RB_ROOT;
- RB_CLEAR_NODE(&cfqg->rb_node);
+ /* Init root group and prefer root group over other groups by default */
+ rcu_read_lock();
+ spin_lock_irq(q->queue_lock);
- /* Give preference to root group over other groups */
- cfqg->weight = 2*BLKIO_WEIGHT_DEFAULT;
+ cfqd->root_group = cfq_get_cfqg(cfqd, &blkio_root_cgroup);
-#ifdef CONFIG_CFQ_GROUP_IOSCHED
- /*
- * Set root group reference to 2. One reference will be dropped when
- * all groups on cfqd->cfqg_list are being deleted during queue exit.
- * Other reference will remain there as we don't want to delete this
- * group as it is statically allocated and gets destroyed when
- * throtl_data goes away.
- */
- cfqg->ref = 2;
+ spin_unlock_irq(q->queue_lock);
+ rcu_read_unlock();
- if (blkio_alloc_blkg_stats(&cfqg->blkg)) {
- kfree(cfqg);
+ if (!cfqd->root_group) {
kfree(cfqd);
return -ENOMEM;
}
- rcu_read_lock();
-
- cfq_blkiocg_add_blkio_group(&blkio_root_cgroup, &cfqg->blkg,
- cfqd->queue, 0);
- rcu_read_unlock();
- cfqd->nr_blkcg_linked_grps++;
+ cfqd->root_group->weight = 2*BLKIO_WEIGHT_DEFAULT;
- /* Add group on cfqd->cfqg_list */
- hlist_add_head(&cfqg->cfqd_node, &cfqd->cfqg_list);
-#endif
/*
* Not strictly needed (since RB_ROOT just clears the node and we
* zeroed cfqd on alloc), but better be safe in case someone decides
@@ -3727,14 +3705,14 @@ static int cfq_init_queue(struct request_queue *q)
/*
* Our fallback cfqq if cfq_find_alloc_queue() runs into OOM issues.
* Grab a permanent reference to it, so that the normal code flow
- * will not attempt to free it.
+ * will not attempt to free it. oom_cfqq is linked to root_group
+ * but shouldn't hold a reference as it'll never be unlinked. Lose
+ * the reference from linking right away.
*/
cfq_init_cfqq(cfqd, &cfqd->oom_cfqq, 1, 0);
cfqd->oom_cfqq.ref++;
- cfq_link_cfqq_cfqg(&cfqd->oom_cfqq, &cfqd->root_group);
-
- cfqd->queue = q;
- q->elevator->elevator_data = cfqd;
+ cfq_link_cfqq_cfqg(&cfqd->oom_cfqq, cfqd->root_group);
+ cfq_put_cfqg(cfqd->root_group);
init_timer(&cfqd->idle_slice_timer);
cfqd->idle_slice_timer.function = cfq_idle_slice_timer;
--
1.7.7.3
--
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