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Subject[PATCH 02/11] blkcg: kill blkio_list and replace blkio_list_lock with a mutex
Date
With blkio_policy[], blkio_list is redundant and hinders with
per-queue policy activation. Remove it. Also, replace
blkio_list_lock with a mutex blkcg_pol_mutex and let it protect the
whole [un]registration.

This is to prepare for per-queue policy activation and doesn't cause
any functional difference.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
---
block/blk-cgroup.c | 32 +++++++++++++++++---------------
block/blk-cgroup.h | 1 -
2 files changed, 17 insertions(+), 16 deletions(-)

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 9449c38..af665fe 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -24,9 +24,7 @@

#define MAX_KEY_LEN 100

-static DEFINE_SPINLOCK(blkio_list_lock);
-static LIST_HEAD(blkio_list);
-
+static DEFINE_MUTEX(blkcg_pol_mutex);
static DEFINE_MUTEX(all_q_mutex);
static LIST_HEAD(all_q_list);

@@ -311,8 +309,9 @@ blkiocg_reset_stats(struct cgroup *cgroup, struct cftype *cftype, u64 val)
struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgroup);
struct blkio_group *blkg;
struct hlist_node *n;
+ int i;

- spin_lock(&blkio_list_lock);
+ mutex_lock(&blkcg_pol_mutex);
spin_lock_irq(&blkcg->lock);

/*
@@ -321,15 +320,16 @@ blkiocg_reset_stats(struct cgroup *cgroup, struct cftype *cftype, u64 val)
* anyway. If you get hit by a race, retry.
*/
hlist_for_each_entry(blkg, n, &blkcg->blkg_list, blkcg_node) {
- struct blkio_policy_type *pol;
+ for (i = 0; i < BLKIO_NR_POLICIES; i++) {
+ struct blkio_policy_type *pol = blkio_policy[i];

- list_for_each_entry(pol, &blkio_list, list)
- if (pol->ops.blkio_reset_group_stats_fn)
+ if (pol && pol->ops.blkio_reset_group_stats_fn)
pol->ops.blkio_reset_group_stats_fn(blkg);
+ }
}

spin_unlock_irq(&blkcg->lock);
- spin_unlock(&blkio_list_lock);
+ mutex_unlock(&blkcg_pol_mutex);
return 0;
}

@@ -732,20 +732,21 @@ void blkio_policy_register(struct blkio_policy_type *blkiop)
{
struct request_queue *q;

+ mutex_lock(&blkcg_pol_mutex);
+
blkcg_bypass_start();
- spin_lock(&blkio_list_lock);

BUG_ON(blkio_policy[blkiop->plid]);
blkio_policy[blkiop->plid] = blkiop;
- list_add_tail(&blkiop->list, &blkio_list);
-
- spin_unlock(&blkio_list_lock);
list_for_each_entry(q, &all_q_list, all_q_node)
update_root_blkg_pd(q, blkiop->plid);
+
blkcg_bypass_end();

if (blkiop->cftypes)
WARN_ON(cgroup_add_cftypes(&blkio_subsys, blkiop->cftypes));
+
+ mutex_unlock(&blkcg_pol_mutex);
}
EXPORT_SYMBOL_GPL(blkio_policy_register);

@@ -753,19 +754,20 @@ void blkio_policy_unregister(struct blkio_policy_type *blkiop)
{
struct request_queue *q;

+ mutex_lock(&blkcg_pol_mutex);
+
if (blkiop->cftypes)
cgroup_rm_cftypes(&blkio_subsys, blkiop->cftypes);

blkcg_bypass_start();
- spin_lock(&blkio_list_lock);

BUG_ON(blkio_policy[blkiop->plid] != blkiop);
blkio_policy[blkiop->plid] = NULL;
- list_del_init(&blkiop->list);

- spin_unlock(&blkio_list_lock);
list_for_each_entry(q, &all_q_list, all_q_node)
update_root_blkg_pd(q, blkiop->plid);
blkcg_bypass_end();
+
+ mutex_unlock(&blkcg_pol_mutex);
}
EXPORT_SYMBOL_GPL(blkio_policy_unregister);
diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index 64392ac..c772581 100644
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -102,7 +102,6 @@ struct blkio_policy_ops {
};

struct blkio_policy_type {
- struct list_head list;
struct blkio_policy_ops ops;
enum blkio_policy_id plid;
size_t pdata_size; /* policy specific private data size */
--
1.7.7.3


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