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Subject[PATCH 11/16] blkcg: add blkio_policy[] array and allow one policy per policy ID
Date
Block cgroup policies are maintained in a linked list and,
theoretically, multiple policies sharing the same policy ID are
allowed.

This patch temporarily restricts one policy per plid and adds
blkio_policy[] array which indexes registered policy types by plid.
Both the restriction and blkio_policy[] array are transitional and
will be removed once API cleanup is complete.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
---
block/blk-cgroup.c | 10 ++++++++++
block/blk-cgroup.h | 2 ++
2 files changed, 12 insertions(+), 0 deletions(-)
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index cd9fbae..3c13943 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -29,6 +29,8 @@ static LIST_HEAD(blkio_list);
struct blkio_cgroup blkio_root_cgroup = { .weight = 2*BLKIO_WEIGHT_DEFAULT };
EXPORT_SYMBOL_GPL(blkio_root_cgroup);

+static struct blkio_policy_type *blkio_policy[BLKIO_NR_POLICIES];
+
static struct cgroup_subsys_state *blkiocg_create(struct cgroup_subsys *,
struct cgroup *);
static int blkiocg_can_attach(struct cgroup_subsys *, struct cgroup *,
@@ -1694,7 +1696,11 @@ static void blkiocg_attach(struct cgroup_subsys *ss, struct cgroup *cgrp,
void blkio_policy_register(struct blkio_policy_type *blkiop)
{
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);
}
EXPORT_SYMBOL_GPL(blkio_policy_register);
@@ -1702,7 +1708,11 @@ EXPORT_SYMBOL_GPL(blkio_policy_register);
void blkio_policy_unregister(struct blkio_policy_type *blkiop)
{
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);
}
EXPORT_SYMBOL_GPL(blkio_policy_unregister);
diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index 41c960b..562fa55 100644
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -19,6 +19,8 @@
enum blkio_policy_id {
BLKIO_POLICY_PROP = 0, /* Proportional Bandwidth division */
BLKIO_POLICY_THROTL, /* Throttling */
+
+ BLKIO_NR_POLICIES,
};

/* Max limits for throttle policy */
--
1.7.7.3


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